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The human body constantly undergoes heat exchange with the environment, and that can be imaged well by thermal imaging. Some application of thermal imaging is in neurology, vascular disorders, rheumatic diseases, oncology, dentistry, and ophthalmology. Every activity described above has unique characteristics. The temperature range for inflammatory condition of the human skin varies significantly from that of an ocular surface. Specific to ophthalmology, the thermal imaging should be able to capture the subtle changes of ocular surface temperature. The existing thermal sensors used in most ophthalmic studies have a dynamic range from -20°C to 350°C and accuracy of 2°C. This paper talks about the development and calibration of a new sensor with optimization in the desired dynamic range and its demonstration for capturing the ocular surface temperature.

Top surface imaging (TSI) techniques using vapor or liquid phase silylation have been investigated extensively as alternatives to conventional resist processing. However, earlier imaging schemes such as diffusion enhanced silylated resist (DESIRE) and digital top surface imaging showed several difficulties limiting the successful application of such TSI approaches. In the case of DESIRE, additional CF4 plasma descum process was required to remove the thin layer of Si incorporated into the cross-linked regions, as some of the Si remained even in the unexposed regions. Also, difference in the cross-linking density and subsequent amount of silicon incorporation across the width of an optically projection printed feature led to non-uniform silylation profiles resulting the difficulty with critical dimension (CD) control of the feature and increased the LER of the overall process. In the case of digital TSI, even though it was developed to overcome these problems with the cross-linking-based silylation process, the concentration of active sites in the exposed polymer varies across the feature width due to the non-uniform energy deposition profile across a feature which results from the non-ideal aerial image produced using optical projection tools. In this study, we have used a diazoketo-functionalized polymer as the platform for the immobilization of amine-functionalized poly(dimethyl siloxane) (amine-PDMS). The diazoketo functional groups undergo Wolff rearrangement to generate carboxylic acid groups upon UV light exposure. This chemistry is exploited to create alternate hydrophilic/hydrophobic patterned regions by selective UV light exposure. The hydrophilic regions that contain carboxylic acid groups predominantly are further used to immobilize amine-PDMS by amide bond formation using carbodiimide coupling chemistry. Due to the high silicon content, the immobilized PDMS acts as the etch barrier for the subsequent oxygen plasma reactive ion etching (O2-RIE) process. Thus, a negative-tone pattern has been successfully generated using O2-RIE process. An amine-PDMS with a molecular weight of 900 was used in this study. Auger electron spectroscopy was employed to characterize the immobilization of amine-PDMS onto UV light exposed regions of diazoketo-functionalized polymer surface. Atomic force microscopy was used to study the surface smoothness after O2-RIE process. Scanning electron microscopy was used to image the pattern profiles formed after O2-RIE process. High resolution pattern profiles are obtained using the TSI process reported in this study.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An imaging system for the continuous casting mold copper surface is researched and developed, to replace the on-line manual measuring method, which is used to checking Copper defects such as wearing, scratches and coating loss and other phenomena. Method: The imaging system proposes a special optical loop formed by three Mirrors, selects light source, CCD camera and lens type, designs mechanical transmission system and installation platform. Result: the optical loop and light source can insure imaging large-format object in narrow space. The CCD camera and lens determine the accuracy of horizontal scanning, and the mechanical transmission system ensures accuracy of the vertical scan. The installation platform supplies base and platform for the system. Conclusions: CCD-based copper surface imaging system effectively prevent defects such as missed measuring and low efficiency, etc. It can automatically and accurately shoot copper surface images on-line, and supply basis for image processing, defects identification and copper changing in the late.

Optoacoustic systems making use of optical detection probes are potentially advantageous over contact transducers for noncontact, noninvasive high-resolution near surface imaging applications. In this work, an interferometer is used for high-frequency optoacoustic microscopy. The limitations of this system in terms of both sensitivity and resolution are discussed. A theoretical model has been developed for two-dimensional excitation source geometries, which can be used to predict the optoacoustic signal from a target material with an arbitrary through-thickness optical absorption distribution. The model incorporates the temporal and spatial profile of the excitation laser pulse, and is used to predict the actual out-of-plane displacement at the target surface. An adaptive, photorefractive crystal-based interferometry system has been used to measure the optically induced displacement on the surface of target materials, and the results show reasonable quantitative agreement with theory. The detection system has a 200 MHz bandwidth allowing for high-resolution imaging, and the use of optical probes for both generation and detection allows for the probes to be easily co-aligned on the sample surface. Preliminary experimental results are presented demonstrating the feasibility of using all-optical optoacoustic microscopy for near surface imaging of small-scale spatial variations in optical absorption.

We present an imaging technique using an optically trapped silica microrod probe controlled using holographic optical tweezers. The probe is raster scanned over a surface, allowing an image to be recorded in a manner analogous to scanning probe microscopy (SPM), with closed loop feedback control provided by high-speed CMOS camera image tracking. We demonstrate a proof of principle of this technique by imaging the surface of an oil droplet. We estimate the normal force exerted on the sample during imaging to be 1 pN. The resolution is limited by the diameter of the microrod tip, thermal motion of the probe and the tracking accuracy. As our technique is not diraction limited, there is scope for signicant improvement by reducing the tip diameter, and position clamping to reduce unwanted thermal motion.

Broad-band light reflectance spectroscopy (LRS) of tissue with sub-millimeter fiber optic probes in the visible and nearinfrared range has shown its utility in differentiation of tissue types, identification of cancer, and measurement of stimulus-induced physiological responses. So far, single point measurement set-up has been widely employed to determine local optical properties of tissue. However, it may often be of interest to obtain a 2D map of a surface area of a tissue under investigation, rather than a single point reading, as in case of cancer margin detection or intraoperative perfusion measurement. It is thus imperative to expand the LRS technique to multipoint measurement covering a larger surface area. Here we describe the two methods that we use to quantify the hemoglobin derivatives and scattering of tissue under investigation, and then utilize two bifurcated fiber optic probes with different fiber diameters and different source-detector separations, to demonstrate the 2D imaging capability of LRS technique. In this study, we constructed a tissue phantom, simulating tissue and blood vessel, and used 2D scanning to determine the spatial resolution and depth resolution using two different probe geometries. Our results suggest that the depth sensitivity of these probes was limited to sub-millimeter for hemoglobin derivatives, whereas scattering changes could be observed up to 2mm deep. It was also found that the lateral resolution was affected, and the scattering signal became more diffuse, as a function of depth.

A novel method for performing top surface imaging (TSI) on a single polymeric photoresist film using area selective atomic layer deposition (ALD) is presented. In this method, exposure of the polymer thin film creates reactive hydroxyl sites on the film surface in the exposed areas that subsequently act as nucleation and growth sites for deposition of metal oxide features using a chemically selective ALD process. It is demonstrated that titanium isopropoxide and water can be used as ALD precursors in conjunction with a chemically amplified photoresist film, formulated using a protected polymer (poly-tertbutylmethacrylate (PtBMA)) and a photoacid generator (triphenylsulfonium tris(perfluoromethanesulfonyl) methide), to successfully perform such an area selective ALD TSI process. Using this material set and methodology, micron scale photoresist features are defined, metal oxide patterns are produced, and these patterns have been transferred through the polymer film via plasma etching. A comparison is also made between the silylation chemical contrast obtained from earlier TSI methods and the metal oxide deposition contrast obtained using the ALD TSI method. It is shown that the ALD TSI chemical contrast for metal oxide deposition can be much higher than the corresponding silylation-based silicon incorporation contrast This result translates into a unique feature of the ALD TSI process which is it can be achieved without requiring the descum etch that is commonly needed with other TSI methods based on silylation.

Application of a top surface imaging process by silylation (TIPS) to ArF excimer lithography is desirable for ULSI production with minimum feature size below 0.12micrometers . It provides high etch resistance and controls non-uniform reflectivity in the multiple film layers over topography and shows superior characteristics in terms of adhesion and resist pattern collapse compared with single layer resist process of wet development. The processes for top surface imaging have been improved by many groups, however, the design of photoresist for TIPS in 193nm lithography has been considerably limited due to its characteristics like energy sensitivity, silylation selectivity. Positive-tone chemically amplified TSI resist of crosslinking type is more appropriate for sub-100nm lithography in consideration of adhesion and resist rigidity. A new class of positive phororesist containing polyvinylphenol and novel acetal type crosslinker of poly(3,3'-dimethoxypropene) was developed for 193nm top surface imaging process by silylation. This new resist containing acetal type crosslinker is quite different with those practiced in traditional DUV and ArF lithography. Novel crosslinker was synthesized from polyacrolein with a yield of 90%. And then the silylation properties and lithography performances of the resist were investigated for 193nm top surface imaging process using gas-phase 1,1,3,3- tetramethyl disilazane(TMDS) as a silylating agent. The minimum pattern size of 0.12micrometers L/S was defined after dry development at a sensitivity of 2 mJ/cm 2 with annular illumination using ArF microstepper having 0.60 NA. In this paper, the material characteristics of novel resist containing acetal type crosslinker of poly(3,3'- dimethoxypropene) and lithographic performances is reported for 193nm top surface imaging process by silylation.

The three-dimensional shapes of microscopic objects are becoming increasingly important for battlespace CBRNE sensing. Potential applications of microscopic 3D shape observations include characterization of biological weapon particles and manufacturing of micromechanical components. Aerosol signatures of stand-off lidar systems, using elastic backscatter or polarization, are dictated by the aerosol particle shapes and sizes that must be well characterized in the lab. A low-cost, fast instrument for 3D surface shape microscopy will be a valuable point sensor for biological particle sensing applications. Both the cost and imaging durations of traditional techniques such as confocal microscopes, atomic force microscopes, and electron scanning microscopes are too high. We investigated the feasibility of a low-cost, fast interferometric technique for imaging the 3D surface shape of microscopic objects at frame rates limited only by the camera in the system. The system operates at two laser wavelengths producing two fringe images collected simultaneously by a digital camera, and a specialized algorithm we developed reconstructs the surface map of the microscopic object. The current implementation assembled to test the concept and develop the new 3D reconstruction algorithm has 0.25 micron resolution in the x and y directions, and about 0.1 micron accuracy in the z direction, as tested on a microscopic glass test object manufactured with etching techniques. We describe the interferometric instrument, present the reconstruction algorithm, and discuss further development.

Top surface imaging (TSI) systems based on vapor phase silylation have been investigated for use at a variety of wavelengths. This approach to generating high aspect ratio, high resolution images held great promise particularly for 193 nm and EUV lithography applications. Several 193 nm TSI systems have been described that produce very high resolution (low k factor) images with wide process latitude. However, because of the line edge roughness associated with the final images, TSI systems have fallen from favor. In fact, top surface imaging and line edge roughness have become synonymous in the minds of most. Most of the 193 nm TSI systems are based on poly(p-hydroxystyrene) resins. These polymers have an unfortunate combination of properties that limit their utility in this application. These limiting properties include (1) High optical density (2) Poor silylation contrast (3) Low glass transition temperature of the silylated material. These shortcomings are related to inherent polymer characteristics and are responsible for the pronounced line edge roughness in the poly(p-hydroxystyrene) systems. We have synthesized certain alicyclic polymers that have higher transparency and higher glass transition temperatures. Using these polymers, we have demonstrated the ability to print high resolution features with very smooth sidewalls. This paper will describe the synthesis and characterization of the polymers and their application to top surface imaging at 193 nm. Additionally, it will describe the analysis that was used to tailor the processing and the polymer's physical properties to achieve optimum imaging.

Focused Ion beam (FIB) lithography has significant advantages over the electron beam counterpart in terms of resist sensitivity, backscattering and proximity effects. However, combining the FIB lithography with Top Surface Imaging (TSI) will extend its advantages by allowing anisotropic processing of thicker resist layers. This paper reports the development of novel single layer lithography process by combining focused Ga + ion beam (Ga + FIB) lithography, silylation and oxygen dry etching. The Negative Resist Image by Dry Etching (NERIME) is a TSI scheme for DNQ/novolak based resists and can result in either positive or negative resist images depending on the extent of the ion beam exposure dose. Results show that Ga + ion beam dose in the range of 1μC/cm 2 to 50μC/cm 2 at 30keV can successfully prevent silylation of the resist, thus resulting in the formation of positive image after the dry etching. A negative image can be formed by using a second Ga + ion beam exposure with a dose higher than 900 μC/cm 2 at 30keV to pattern lines into the original exposed resist area. It was observed that resist regions exposed to such high doses can effectively withstand oxygen dry development, thus giving formation of negative resist image. In this study, nanometer resist patterns with high aspect ratio up to 15 were successfully resolved due to the ion beam exposure and anisotropic dry development. This novel TSI scheme for ion beam lithography could be utilized for the fabrication of critical CMOS process steps, such as deep isolation trench formation and lithography over substantial topography.

Depth of focus is known to decrease with short wavelengths of light or high numerical aperture lenses. With the advent of short wavelength ultraviolet sources (DUV - 248 nm, 213 nm & 193 nm), and high numerical aperture lenses (NA > .40), the depth of focus for imaging sub-micron features in single layer photoresist becomes an area of concern. Surface imaging resist (SIR), or top surface imaging (TSI) has been proposed as the solution to the diminishing depth of focus for lithography of single layer photoresists. The most commonly known form this technology has taken is the silylation of organic photoresists following exposure to an appropriate illuminating source. This technology has drawbacks in that the resulting silylated resist is not too much different chemically from many of the inorganic substrates that one wishes to pattern. This limits its applicability in use with fluorine containing plasmas. It also creates a film that is difficult to remove after the pattern transfer is accomplished. A developmental type of surface imaging system is currently being evaluated for its applicability as a photolithographical resist. MIMMITM (micro imaging with metal mask integration) uses an ultrathin metallic layer over conventionally applied and exposed photoresist. The film is shallowly developed and metallization is electrolessly applied to the remaining pattern. The metal pattern is further dry developed to complete its structure for image transfer. The metallized pattern is impervious to all commonly used plasma etch environments and is easily stripped in dilute acid and common organic solvents.

A top surface imaging (TSI) process with a very thin imaging resist is one of the approaches for 100-nm or smaller pattern fabrication. We have been evaluating the different types of bilayer silylation processes for 193nm lithography, such as the bilayer silylation process without applying any wet-development and an improved bilayer silylation process that applies the vapor phase silylation treatment after alkaline wet-development of the top layer (SILYAL). We have been trying to apply these TSI processes to 157nm lithography and could successfully fabricate sub-100-nm fine resist patterns with high aspect ratios. We confirmed the lithographic high performance of these bilayer silylation processes and 157-nm lithography. In this paper, we describe the current status and progress in these silylation processes for 157nm lithography.

Top surface imaging (TSI) has had an interesting history. This process showed great promise in the late 1980's and several attempts were made to introduce it to full-scale manufacturing. Unfortunately, defect density problems limited the process and it fell from favor. TSI emerged again as an important part of the EUV and 193 nm strategies in the early stages of those programs because it offered a solution to the high opacity of common resist materials at both wavelengths. A flurry of research in both areas identified the seemingly insurmountable problem of line edge roughness than typical single layer resist systems. This has largely been due to the development of polymers specifically tailored for this end use. The optimum materials must be moderately transparent and have high Tg's in the silylated state. The 157nm program has much in common with the early stages of the 193nm program. The optical density of even 193nm resist materials at 157nm is far too high to allow their use in single layer applications. The less stringent optical density of even 193nm resist materials at 157nm is far too high to allow their use in single layer applications. The less stringent optical density requirements of TSI make it a potentially viable imaging scheme for use at 157nm. Various TSI materials, including the traditional poly(t-BOC- hydroxystyrene), as well as novel aliphatic cyclic polymers bearing bis-trifluoromethyl carbinol substituents, have been investigated for use at 157 nm, and smooth high-resolution images have been generated.

In the past, a number of authors have described the advantages of the silylation reaction performed in a novolak resist's latent image. Both the advantages and difficulties were described. A process based on silylation of latent images was shown to improve the working resolution in a novolak resist due to the surface imaging principle. The difficulties included swelling of the resist film during silylation resulting in some loss of dimensional control of critical dimensions. This paper describes a different approach to near surface imaging. The method relies on the use of spin-on, closely planarizing polymeric antireflective coating, such as AZ TM BARLi TM coating, followed by imaging thin (less than 0.5 micron) i-line resist. After a conventional lithographic process which includes a wet develop step, a silylation reaction is performed. Swelling of the real resist image due to silylation is controllable within necessary tolerances. Image transfer process of the silylated image is also described.

Thin film imaging processes such as top surface imaging (TSI) are candidates for sub-150 nm lithography using 193 nm lithography. Single component, non-chemically amplified, positive tone TSI photoresists based on phenolic polymers demonstrate good post-etch contrast, resolution, and minimal line edge roughness, in addition to being the most straightforward thin film imaging approach. In this approach, ArF laser exposure results directly in radiation- induced crosslinking of the phenolic polymer, followed by formation of a thin etch mask at the surface of the un- exposed regions by vapor-phase silylation, followed by reactive ion etching of the non-silylated regions. However, single component resists based on poly(para-hydroxystryene) (PHS), such as MicroChem's Nano MX-P7, suffer from slow photospeed as well as low silylation contrast which can cause reproducibility and line-edge-roughness problems. We report that selected aromatic substitution of the poly(para- hydroxystryene) polymer can increase the photospeed by up to a factor of four relative to un-substituted PHS. In this paper we report the synthesis and lithographic evaluations of four experimental TSI photoresists. MX-EX-1, MX-EX-2, MX- EX-3 and MX-EX-4 are non-chemically amplified resists based on aromatic substitutions of chloro- and hydroxymethyl- groups and PHS. We report optimized lithographic processing conditions, line edge roughness, silylation contrast, and compare the results to the parent PHS photoresist.

The maturity and acceptance of top surface imaging (TSI) technology has been hampered by several factors including inadequate resist sensitivity and silylation contrast, defects and line edge roughness and equipment performance/reliability issues. We found that the use of a chemically amplified resist can improve the sensitivity by a factor of 1.5 - 2X, without compromising line edge roughness. While the post-silylation contrast of this chemically amplified material is poor ((gamma) > 10) and the use of advanced silylation chemistries (disilanes) can further reduce the dose-to-size and increase the contrast. We have also demonstrated that using sulfur dioxide in the plasma etch process can improve the sidewall passivation of the resist lines, thus reducing the overall line edge roughness. Finally, we have been able to successfully use the TSI process to pattern deep sub-micron polysilicon and metal patterns.

The strong attenuation of extreme ultraviolet (EUV) radiation by organic materials necessitates the use of a thin layer imaging (TLI) process for EUV lithography. Several TLI processes have been identified for potential use for EUVL, and the common theme in these approaches is the transfer of the aerial image to a thin layer of refractory-containing material, which is then used as a dry O 2 etch mask during a subsequent pattern transfer to the device layer. One TLI process that has been extensively examined for EUVL is the silylated top-surface imaging (TSI) technology, which is discussed in this paper. Using a new disilane silylation reagent, dimethylaminodimethyldisilane (DMDS) and 13.4 nm exposure, the TSI process has been used to print 100 nm lines and spaces at equal pitch and 70 nm lines and spaces at a higher 1:2 pitch. The line edge roughness for the printed lines has been determined using a custom image analysis program and, as expected, varies with the particular EUV exposure system and numerical aperture. Exposures done with 193 nm lithography and the TSI process using DMDS are also shown for comparison to the EUV results.

Top-surface imaging process by silylation (TIPS) has been suggested as an attractive solution to cope not only with limitation of resolution and process latitudes but also with line width variations due to reflections over steps. However this technique has not received a wide acceptance as a production worthy process until now, because of the stringent requirements on suitable silylation and dry development equipment that have good uniformity and good reproducibility. In a parametric study of TIPS dry development steps, we found the most important factors in the first step and the second step respectively. The optimized process demonstrated good etch rate uniformity and excellent 0.17 micrometer dense and isolated pattern of gate and islands pattern of capacitor in 1 G bit DRAM device. Their profiles were vertical and uniform within a wafer, while the proximity effect between dense and isolated pattern of gate remained 0.01 micrometer. In islands pattern, wider process margins of both local depth of focus (LDOF) and exposure latitude (EL) could be obtained and excellent 3(sigma) value of critical dimension (CD) uniformity within a wafer confirmed better applicability to 1 G bit DRAM and beyond. When silylated resist patten was transferred into substrate layer CD bias and uniformity could be controlled less than 0.02 micrometer. There were also no residues after both photoresist strip and induced polymer removal step. From these studies. TIPS process using cluster tool of silylation system made by LRC and TCP TM 9400 TM SE etcher for dry development was demonstrated a production worth process for the sub-0.20 micrometer lithography in terms of obtaining finer pattern without pattern problems and a reliable process for 1 G bit DRAM and beyond.

We have investigated the effect of line edge roughness (LER) of active patterns used for shallow trench isolation to the electrical performance of MOS transistor applicable for 1 giga-bit DRAM. Three different processes for resist patterning were applied for comparative analysis to form the active pattern in MOS transistor; the first method applied a conventional single layer resist (SLR) process, the second TIPS with two step dry development, and the third another TIPS with three step dry development. The third process adopted an additional step to break-through thin silicon dioxide which may contribute to the LER. The LER data of an active pattern before and after nitride substrate etching and their profiles were investigated among these processes. The third method shows the almost same LER and CD uniformity of the active pattern as those of SLR. The electrical properties. Only, threshold voltage variation of MOS transistor by the second method shows the worse results than those of SLR. Considering the ratio of LER in isolated active pattern with channel width of 0.3 micrometers to its average CD value, we think that its ratio should be controlled well below 7 percent for TIPS to make an useful technology for real device. Based on these studies, we believed that the well-controlled TIPS process using three step dry development is a strong candidate for device production of ArF and EUV lithography, if the advantages of TIPS technology over the SLR process are considered in the respect of lithography.

The advantages of surface-imaging photoresist processes have been well documented in the literature: greater resolution, wider focus budget, and less sensitivity to topography and reflections from the substrate. The diffusion enhanced silylated resist (DESIRE) is a good example of a surface-imaging process. In previous papers we have presented characterization data for this process, and discussed some of the issues involved in its implementation in a manufacturing environment. More recently we have reviewed integration issues evolving from the interactions between the equipment, materials, and process. In this paper we continue our discussion of process integration issues focusing on: (1) electrical discharge, or arcing, during dry-development, and (2) line-width uniformity. Arcing is a very serious problem because of its catastrophic effect on yield. Thus far we have determined that the substrate and equipment influence the occurrence of arching, but further work remains to be done to determine all the possible causes. In previous papers we showed that the linewidth can be controlled across the wafer, and from wafer-to-wafer. By optimizing the magnetic field uniformity in our initial process set up, we were able to control the linewidth to within +/- 8% for 0.63 micrometers lines. However, to maintain this control over time, modifications in the silylation reactor had to be made. Additional improvements in the linewidth uniformity require us to go back and make modifications to the dry-develop reactor to improve the magnetic field uniformity further. These two examples illustrate the need to take a comprehensive or process integration approach to successfully implement this process.

A variety of analytical and process control techniques have been employed during process development activities for a 0.5 micrometers deep UV positive tone surface imaging process. Examples of applications of these methods for identification of primary positive tone surface imaging issues and process optimization for enhancement of ultimate resolution are described. Advantages and limitations for each technique are discussed.

This paper describes the silylation properties and the lithographic performance of ArF (193 nm) surface imaging process with bis(dimethylamino)methylsilane [B(DMA)MS]. The silicon concentration of silylated region with B(DMA)MS in liquid phase is much higher (2 times) than that for the conventional silylation with dimethylsilyldimethylamine (DMSDMA) in vapor phase. The excellent resolution of 0.12 micrometers L/S and practical DOF (1.0 micrometers in a range for 0.18 micrometers L/S) have been achieved using ArF exposure system with a conventional binary mask under a normal illumination. Further, the resolution of 0.088 micrometers has been obtained with a Levenson-type phase shifting mask.

Sub-micron resist features obtained by surface imaging and dry development have been used as masks in the pattern transfer of multilevel metal stacks in a single-wafer multichamber etcher. The calibration of such a negative working submicron lithographic process, derived from a g-line wafer stepper having a specified resolution of 1 micron, is described. Surface imaging was initiated by silylation of a proprietary resist using HMDS, while dry development was performed in a single-stage oxygen process in a conventional reactive ion etcher. Metal etch processes are outlined in conjunction with their effect on resist integrity and removal and the need for post-development deep-UV hardening. While not being part of the two-layer demonstrator, submicron 'via' hole definition in polyimide interlayer dielectric is demonstrated in a single-stage dry development/pattern transfer process.

A variety of different approaches were used in an effort to improve the photospeeds of single component TSI resists based on poly(4-hydroxystyrene). The variations included molecular weights, co-monomer partners, and selected substituents. The factors that were studied dramatically affected silylation rates, in one case by as much as an order of magnitude. However, when the silylation times were adjusted to compensate for the rate differences and silylation depths, only minimal differences in photospeed were observed. The apparent contrast measured by swelling upon silylation was very poor ((gamma) equals 1.5) while the contrast measured after etching was quite high, approximately ten times that of the silylation value.

The practical limits of i-line top surface imaging process using a novolak based photoresist were investigated dependent on exposure techniques such as conventional and off-axis illumination. Ultimately, quarter micron small geometry was clearly delineated and depth of focus (DOF) latitude of 1.5micrometers and 2.7micrometers was achieved respectively for 0.25micrometers and 0.30micrometers lines and spaces pattern by annular illumination of 0.50NA. To compensate proximity effect caused by pattern density, sub-resolution auxiliary pattern was firstly optimized for off- axis illumination of quadrapole and annular. As a result, critical dimension (CD) difference between dense and isolated pattern in 0.30micrometers reduced to half-level compared to that of non-auxiliary pattern. It was found that desilylation phenomenon was critically affected by the kind of photopolymer reacted with silicon source and molecular weight of silylation agent. Novolak based polymer maintained superior silylation durability to polyvinyl phenolic (PVP) resin. New silylation process concept which is dual silylation method was developed to utilize PVP's merits in the silylation process against desilylation. Dry development lithography of i-line was feasible to practical application of prototype 256 mega bit DRAM which demands 0.30micrometers patterning with a reproducibility.

A method for full-field surface profiling in the tandem scanning confocal microscope has been previously described. The technique utilizes chromatic aberration to produce an extended and color coded focal volume. Planes at different axial depths within this volume correspond to the foci of different wavelengths through the intentionally aberrant system. To determine the height of any point within the field, the confocal detection system must be capable of identifying the wavelength of the most intensely reflected light from that point. Hence the relative sensitivity of the detector and the spectral response of the imaging system are important parameters. We have utilized xenon and mercury arc sources and compared results with various types of objective lens. One potential limitation of this microscope is the fact that the introduction of longitudinal chromatic aberration affects the correction of the optics for plan imaging, i.e., introduces spherical aberrations, but the technique is rapid and produces results well correlated with more conventional techniques. To allow detailed study of the use of a chromatic 3-D probe for surface imaging we have designed and constructed a stage- scanned instrument which uses on-axis optics and is therefore free from spherical aberrations and can be corrected optimally. The instrument is described and results presented for single pass 3-D imaging.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Techniques commonly used to determine silicon penetration depth during deep UV surface imaging lithography are compared to a method referred to as plasma etch 'staining.' This methodology is described in detail and the results compared and correlated to Rutherford Backscattering Spectroscopy (RBS) and ellipsometric (film swelling) measurements. Effects of the staining parameters on the resulting silicon depth are also discussed.

Deep UV photochemical patterning of chemisorbed metal-binding (ligating) organosilane films has been previously used to demonstrate sub-0.5 micrometers patterned additive metallization by electroless deposition. Significant photospeed advantages have now been obtained using a two step process in which an organosilane film is first patterned and then functionalized to impart the ability to metallize. This is achieved by photochemical patterning of a film which lacks a ligating group, but which is optimized for photospeed. The pattern of chemical functions so created is then reacted with an organic ligand which selectively places the ligand functionalities on the surface. Treatment with an aqueous Pd catalyst followed by electroless plating deposits metal in patterns defined by the irradiation step. Using several chemical approaches based upon this concept, metal patterns have been fabricated to 0.5 micrometers feature width at doses of 50 mJ/cm2 at 193 nm.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

G- and i-line diazonaphthoquinone/novolak photoresist films are surface imaged with g-line, i-line and deep-UV steppers. Following optical exposure, the resist film is treated with aqueous solutions which deposit a catalyst for electroless metal deposition. Wet development of the exposed and catalyzed photoresist results in selective removal of catalyst along with the exposed portion of the underlying photoresist. Upon immersion in an aqueous electroless plating solution, metal is selectively deposited on the unexposed photoresist which is still bearing catalyst to yield a positive-tone plasma etch mask. Oxygen magnetron-enhanced reactive ion etching (O2 MERIE) provides high polymer etch rates (approximately equals 1 micrometers /min) with excellent selectivity (> 300:1) to 70-170 angstrom Ni films. In addition, large ion fluxes produce highly anisotropic etch profiles for faithful pattern transfer. The process has achieved 0.30 micrometers resolution with a 6:1 aspect ratio at 248 nm (0.35 NA). Printing of 0.40 micrometers lines and spaces has been achieved at i-line (0.45 NA) over Al steps.

A variety of novolac-based polymers and blends with photoactive compounds were studied for their suitability as resists in a 193-nm positive-tone silylation process. The addition of photoactive compound was found to reduce the sensitivity of the resist and to hinder the diffusion of the silylating agent. Pure meta-cresol novolacs and polyvinylphenols, both of which can be polymerized to high (> 10,000) molecular weights show the best sensitivity for this process. Diffusion rates correlate with the molar volume of the silylating agent, although the activation energy does not. Resolution of 0.2-micrometers line-and-space gratings has been achieved with the polyvinylphenol and meta-cresol novolac resins.

As the pitch approaches the 10nm node, in order to meet current and future patterning challenges, high resolution techniques are required, complementary to extreme ultraviolet lithography (EUVL) for high volume manufacturing of nanodevices. These complementary techniques should have the following specifications: 1) High patterning resolution, below 10 nm; 2) capability of patterning in 3D; 3) sufficient wafer-scale throughput; 4) the capability of closed loop metrology and 5) the capability of measuring nondestructively through layers, for alignment and overlay applications. Scanning probe microscopy (SPM) has shown a great degree of nano-scale control, and a great potential to address the challenges found in metrology. There has been a broad development of SPM-based methods for patterning and metrology purposes although its exploitation for technological applications is limited due to the modest throughput of scanning probe based techniques. In this article we present experimental results that include the proof-of-principle of using SSURFM to locate existing buried nanopatterns (lines of 50 nm) and subsequently using our patterning technology to manufacture nanocontact holes aligned to the existing buried lines. In combination with the high throughput parallel scanning probe, this example demonstrates the great potential and the suitability of the group of technologies developed at TNO (consisting of the patterning and the subsurface nanoimaging) for alignment and overlay, especially through opaque layers.

In recent years, surface imaging of various biological dynamics and biomechanical phenomena has seen a surge of interest. Imaging of processes such as exocytosis and kinesin motion are most effective when depth is limited to a very thin region of interest at the edge of the cell or specimen. However, many objects and processes of interest are of size scales below the diffraction limit for safe, visible wavelength illumination. Super-resolution imaging methods such as structured illumination microscopy and others have offered various compromises between resolution, imaging speed, and bio-compatibility. In this talk, I will present our most recent progress in plasmonic structured illumination microscopy (PSIM) and localized plasmonic structured illumination microscopy (LPSIM), and their applications in bio-imaging. We have achieved wide-field surface imaging with resolution down to 75 nm while maintaining reasonable speed and compatibility with biological specimens. These plasmonic enhanced super resolution techniques offer unique solutions to obtain 50nm spatial resolution and 50 frames per second wide imaging speed at the same time.

New microlithography patterning technologies must be developed in order to meet the demands of advanced semiconductor manufacturing. This paper describes the development of a new top surface imaging technique that is designed to circumvent the difficulties associated with developing next generation single layer resists. Graft polymerization lithography is an extension of top surface imaging in which exposure creates an acidic surface that activates monomer deposition on top of the base layer. Silicon-containing monomers were synthesized in order to meet the graft polymerization process requirements. A QCM-monitored deposition system was developed to study the fundamental behavior of the deposition process as a function of temperature, pressure, and photoacid generator (PAG) loading. Volumetric, bulk polymer sorption measurements were used to provide insight into the critical sorption behavior that drives the deposition process. These fundamental studies led to a proposed process mechanism that explains the experimentally observed behavior. Finally, proof of concept imaging experiments were conducted that demonstrate the graft polymerization process through all lithographic steps.

With increase in density of semiconductor devices, 193 nm lithography is promising to attain smaller feature size patterns. Surface imaging process is useful for this lithography in terms of large depth of focus and prevention from substrate reflection. As the surface imaging process, so far we developed positive surface modification resist process using CVD for various device patterns' fabrication. To solve the issues of selective polysiloxane layer formation and sensitivity, we have improved this positive surface modification resist process using a new polymer, poly(cyclohexyl p-styrenesulfonate-co-methyl methacrylate), and a new photobase generator, O-phenylacetyl acetonaphthone oxime. 0.15 micrometers pattern was successfully fabricated using the new process with improved sensitivity of 80 mJ/cm2.

We have characterized line-edge roughness in single-layer, top-surface imaging, bilayer and trilayer resist schemes. The results indicate that in dry developed resists there is inherent line-edge roughness which results from the etch mask, resist (planarizing layer) erosion, and their dependence on plasma etch conditions. In top surface imaging the abruptness of the etch mask, i.e., the silylation contrast, and the silicon content in the silylated areas are the most significant contributors to line-edge roughness. Nevertheless, even in the case of a trilayer, where the SiO2 layer represents the near ideal mask, there is still resist sidewall roughness of the planarizing layer observed which is plasma induced and polymer dependent. The mechanism and magnitude of line-edge roughness are different for different resist schemes, and require specific optimization. Plasma etching of silicon, like O2 dry development, contributes to the final line-edge roughness of patterned features.

In order to establish surface imaging process using O 2 - RIE on ArF lithography, silicon containing bi-layer resists have been investigated. We synthesized cyclohexyl pendant silsesquioxane polymer to obtain high transparency at ArF wavelength. This polymer has ladder siloxane structure with high Si density (13 wt%), over 80%0.35 um transmittance at 193 nm, and has carboxylic acid partially protected by acid labile group for TMAH aq. development. Addition of base enhanced the slope of deprotecting reaction and suppressed acid diffusion. The function of specific amines as acid quencher was considered to cause `Proton-Jumping'. Substituting of carboxylic acid by alcohol type polar linkage increased alkali tolerance, adhesion force and polymer Tg. Standard 2.38wt% TMAH developer was applied and expanded the dissolution rate gap. For further improvement of the resolution, we increased alkali tolerance by introduction of tricyclodecanyl pendant and optimized alkali concentration of developer. As a result, suitable dissolution curve for surface imaging resists was realized and rectangular patterns were observed on bottom ARC.

This paper describes the use of a 193 nm surface imaging resist in a new small-field, deep-UV projection exposure system. The 193 nm surface imaging technology utilizes commercial photoresists, in conjunction with a small field step-and-repeat exposure system. Typical processing characteristics of the imaging chemistry are presented, along with a detailed description of the projection exposure system. The resist uses vapor phase silylation with oxygen RIE developing and has been shown to provide wide focus latitude and better than 0.2 micrometers resolution. The imaging system uses a catadioptric lens with 0.5 NA for 0.20 images.

Top surface imaging and subsequent dry development were known to improve lithographic performance. Since negative working DESIRE process was introduced, several alternative methods have also been proposed. We propose a new resist system (SS-201), which is positive working in DUV lithography. We characterized this resist in view of top surface imaging (TSI) process and applied it to our 256 mega bit DRAM test device. Since conventional TSI process has a swelling problem by nature, WEBS (wet development before silylation) technique is proposed to minimize swelling. Special attention was focused on contact holes since our TSI process enables positive tone mask, which has a definite advantage in reducing potential defects in mask making.

In recent years, there have been a lot of studies on surface imaging techniques in which the single layer lithography process is utilized. They have advantages of capability of high resolution, wide focus latitude, small critical dimension (CD) variation on topography, as well as their process simplicity compared with multilayer lithography process. The DESIRE process, one of the surface imaging process, also has the same advantages. This process is based on the selective silylation which proceeds only in an optically exposed region of surface layer with use of vapor phase silylation. This paper describes the relation between resist profile and the silylation condition which may influence the silylated layer owing to the variation of diffusion characteristics of the silylation agent. We found that resist profile was strongly influenced by the silylation condition. In order to make the phenomenon clear, we studied the silylated profile of cross sectional view under various silylation conditions. As a result, it was found that the lower degree of silylation became, the less silicon diffusion depth was dependent on exposure energy and pattern size. Furthermore, the silylated profile having a gentle slope and thin shape tended to make a vertical sidewall profile after dry-development. It is discussed what characteristics of silylated profile have a significant effect on the final resist profile in the DESIRE process.

Dry developable lithography as represented by the DESIRE process, is one of the most attractive surface imaging technologies for advanced optical lithography. A resolution of 0.25 micrometers has been demonstrated with this process, using i-line exposure in conjunction with a phase shifting mask and by deep-UV exposure (248 nm). Surface imaging is especially suited for deep-UV lithography since it overcomes the poor CD-control over topography encountered with highly transparent wet developable resists. In this work the applicability of DESIRE to sub-0.5 micrometers processing has been studied. With regard to the silylation process, crosslinking effects resulting from the radiation at 248 nm have been found to reduce the Si incorporation. This crosslinking effect can be reduced by the use of alternative silylating agents (such as TMDS 1,1,3,3-tetramethyl disilazane), which silylate at a lower temperature. A comparison of processing latitudes for lines and for contact holes has been made for silylation with HMDS and with TMDS. Other issues related to the implementation of DESIRE in typical CMOS processing, such as dry etch compatibility and resist stripping have also been addressed.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Metals can break either in a ductile or brittle manner if a static or dynamic load is applied to the same material. This depends on a variety of factors, such as the manner in which the load is applied, the shape of the mechanical part, the operating conditions, the nature and structure of the metallic material, and the working temperature. If subjected to variable loads, metallic materials break due to what is called fatigue. The microscopic analysis of fracture surfaces is currently carried out by using scanning electron microscopy (SEM). We have proposed, for the first time to our knowledge, a new method to analyze fracture surfaces, using a low coherence interferometry technique, Optical Coherence Tomography (OCT) [Gh. Hutiu, V.-F. Duma, et al., Surface imaging of metallic material fractures using optical coherence tomography, Appl. Opt. 53, 5912-5916 (2014); Gh. Hutiu, V.-F. Duma, et al., Assessment of ductile, brittle, and fatigue fractures of metals using optical coherence tomography, Metals 8, 117 (2018)]. The present paper presents the way we have demonstrated that OCT can replace the gold standard in such assessments, i.e. SEM, despite the fact that OCT has a resolution of 20 to 4 μm (in our investigations), while the SEM we employed has a 4 to 2 nm resolution. A few examples are given in this respect–for different types of fractures. The advantages of OCT versus SEM are discussed. This development opens the way for in situ investigations, for example in forensic sciences, where OCT can be applied (including with handheld scanning probes. as we have developed). In contrast, SEM, TEM, and AFM are lab-based techniques, more expensive, and they require trained operators.

Autoradiography potentially offers high molecular sensitivity and spatial resolution for tumor margin estimation. However, conventional autoradiography requires sectioning the sample which is destructive and labor-intensive. Here we describe a novel autoradiography technique that uses a flexible ultra-thin scintillator which conforms to the sample surface. Imaging with the flexible scintillator enables direct, high-resolution and high-sensitivity imaging of beta particle emissions from targeted radiotracers. The technique has the potential to identify positive tumor margins in fresh unsectioned samples during surgery, eliminating the processing time demands of conventional autoradiography. We demonstrate the feasibility of the flexible autoradiography approach to directly image the beta emissions from radiopharmaceuticals using lab experiments and GEANT-4 simulations to determine i) the specificity for 18 F compared to 99m Tc-labeled tracers ii) the sensitivity to detect signal from various depths within the tissue. We found that an image resolution of 1.5 mm was achievable with a scattering background and we estimate a minimum detectable activity concentration of 0.9 kBq/ml for 18 F. We show that the flexible autoradiography approach has high potential as a technique for molecular imaging of tumor margins using 18 F-FDG in a tumor xenograft mouse model imaged with a radiation-shielded EMCCD camera. Due to the advantage of conforming to the specimen, the flexible scintillator showed significantly better image quality in terms of tumor signal to whole-body background noise compared to rigid and optimally thick CaF 2 :Eu and BC400. The sensitivity of the technique means it is suitable for clinical translation.

The optical coherence tomography (OCT) is an optical imaging method, which is widely applied in variety applications. This technology is used to cross-sectional or surface imaging with high resolution in non-contact and non-destructive way. OCT is very useful in medical applications like ophthalmology, dermatology or dentistry, as well as beyond biomedical fields like stress mapping in polymers or protective coatings defects detection. Standard OCT imaging is based on intensity images which can visualize the inner structure of scattering devices. However, there is a number of extensions improving the OCT measurement abilities. The main of them are the polarization sensitive OCT (PS-OCT), Doppler enable OCT (D-OCT) or spectroscopic OCT (S-OCT). Our research activities have been focused on PS-OCT systems. The polarization sensitive analysis delivers an useful information about optical anisotropic properties of the evaluated sample. This kind of measurements is very important for inner stress monitoring or e.g. tissue recognition. Based on our research results and knowledge the standard PS-OCT provide only data about birefringence of the measured sample. However, based on the OCT measurements more information including depolarization and diattenuation might be obtained. In our work, the method based on Jones formalism are going to be presented. It is used to determine birefringence, dichroism and optic axis orientation of the tested sample. In this contribution the setup of the optical system, as well as tests results verifying the measurements abilities of the system are going to be presented. The brief discussion about the effectiveness and usefulness of this approach will be carried out.

Monte Carlo-based SEM image simulation can reproduce SEM micrographs by calculating scattering events of primary electrons inside the target materials. By using the simulated SEM images, it is possible to optimize imaging conditions prior to the specimen observation, which could save time for finding suitable observation condition. However, a recent trend of miniaturized and 3-dimentional structures of semiconductor devices, and introduction of various novel materials have created a challenge for such SEM image simulation techniques; that is, more precise and accurate modeling is required. In this paper, we present a quantitatively accurate BSE simulation and a precise parameters setting in voltage contrast simulation, for both to reproduce experimental SEM images accurately. We apply these simulation techniques to optimize the accelerating voltage of SEM for sub-surface imaging, and to analyze a charge distribution on the insulating specimen under the electron irradiation. These applications promise the advancement in developing a new device by preparing inspecting condition in a timely manner.

Label-free photoacoustic microscopy (PAM) with nanometric resolution is important to study cellular and sub-cellular structures, microcirculation systems, micro-vascularization, and tumor angiogenesis etc. But, the lateral resolution of a conventional microscopy is limited by optical diffraction. The photonic nanojet generated by silica microspheres can break this diffraction limit. Single silica sphere can provide narrow photonic jet, however its short length and short working distance limits its applications to surface imaging. It is possible to increase the length of the photonic nanojet and its working distance by optimizing the sphere design and its optical properties. In this work, we will present various sphere designs to achieve ultra-long and long-working distance photonic nanojets for far-field imaging. The nanojets thus generated will be used to demonstrate super-resolution photo-acoustic imaging using k-wave simulations. The study will provide new opportunities for many biomedical imaging applications that require finer resolution. MOE (Min. of Education, S’pore) Published version

Imaging spectroscopic reflectometry is a technique suitable for measurements of local optical parameters (thickness, refraction index and index of extinction) of non-uniform thin films along their surface. It is usually assumed that gradients of these non-uniformities are reasonably small. A new design of an imaging spectroscopic reflectometer provides the possibility to successfully measure high gradient non-uniformities along relatively large area of a thin film surface. A specialized low cost apparatus was developed to accomplish a higher resolution of surface imaging at the cost of reduction of the spectral range usable. The whole concept of the imaging spectroscopic reflectometer was designed to achieve high light throughput using only prefabricated optical components. Shorter measurement times and lower demands on an imaging camera used were achieved. The imaging spectroscopic reflectometer mentioned above was realized as a compact device with easy calibration and handling. Any monochromator with its output into an optical fiber can be used as a source of light. The potential of the device is demonstrated using samples with high gradients of thickness along their surfaces. A significant improvement in the resolution of thin film interference pattern images was observed in comparison with the same images obtained by means of an older UV-VIS-NIR device.

The three-dimensional (3D) microstuructural evolution in a Pb-free solder system undergoing accelerated electromigration (EM) testing is characterized using a custom, lab-scale, cone-beam, micro x-ray computed tomography (μXCT) instrument. A micro-scale Sn-0.7Cu butt -joint was subjected to a current density of 104A/cm2 at 100°C. The experimentation was enabled by the design of a miniature fixture for in situ imaging under accelerating EM testing conditions. The fixture is friendly to surface imaging and μXCT scanning. The migrating species, copper and tin, are observed volumetrically through substrate dissolution, solder build-up, and the formation of reaction products in the solder joint by μXCT imaging. The migration of the copper substrate and the formation of copper-tin reaction products is quantified.

Surface plasmon-coupled emission (SPCE) microscopy provides high sensitivity for surface imaging due to the field enhancement effect of surface plasmon resonance. Based on previous theoretical and experimental studies, SPCE microscopy (SPCEM) generates an unusual annular-shape point spread function (PSF). In order to correct the distorted PSF without numerical deconvolution, an experimental method with a spiral phase plate (SPP) has been proposed. However the three-dimensional nature of PSF has not been explored in the past. In this study, we performed a theoretical study to obtain three-dimensional PSF of SPCE microscopy.

A Gen-2 hand-held optical imager has been developed capable of 2D surface imaging and 3D tomography. In the current work, the capability of the imager to resolve two closely placed targets is assessed via 2D and 3D tomographic studies. Resolution studies have been carried out under various experimental conditions using slab phantoms. Preliminary 2D surface images of reflected measurements have demonstrated the ability of the system to resolve 0.95cm diameter targets placed 0.5cm apart at 2cm depth. Three dimensional tomography reconstructions are currently performed to assess the resolution capacity under different experimental conditions.