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Thermal wave (TW) studies of ultra-shallow junctions (USJ) formed by ion implantation into a semiconductor wafer followed by rapid thermal annealing (RTP) are described. It is shown that using the TW technique allows for a simultaneous determination of the most important USJ parameters—depth and profile abruptness. In a TW-based system, the USJ depth is obtained using the quadrature component of the TW signal while determination of USJ profile abruptness is based on the analysis of the TW quadrature and in-phase components measured at two different pump-probe beam offsets. Experimental results for junction depth and abruptness obtained on a set of B+-implanted, RTP-annealed USJ samples show better than 0.99 correlations to the corresponding secondary ion mass spectroscopy data.

Quantitative analysis of ion-implanted layers in Si using the damage-based theoretical modeling and experimental results obtained with the photomodulated reflectance (PMR) technique are described. Our theoretical approach [A. Salnick and J. Opsal, J. Appl. Phys. 91, 2874 (2002)] combines calculations of the ion-induced damage depth profiles in semiconductors with the corresponding scaling of the thermal and carrier plasma wave parameters followed by the calculation of the photothermal response from a multilayered sample. Comparison of the simulated theoretical dose dependencies with experimental PMR amplitude and phase data allows us to study the dynamics of the thermal- and carrier-plasma waves in an ion-implanted semiconductor. The regions of the plasma, thermal, and optical component dominance are defined and the photothermal signal behavior is analyzed in the low, intermediate, and high implantation dose ranges. It is shown that the pump and probe beam wavelengths control the nature of the resulting photothermal signal (thermally or plasma dominated) at low doses while self-annealing effects play a significant role in the photothermal signal behavior at high implantation doses.

Quantitative analysis of ion-implanted layers in Si using the damage-based theoretical modeling and experimental results obtained with the photomodulated reflectance (PMR) technique are described. Our theoretical approach combines the conventional quantum mechanics based calculations of the ion-induced damage depth profiles in semiconductors with the corresponding scaling of the thermal and carrier plasma parameters followed by the calculation of the photothermal response from a multilayered sample. The theoretical limit of the photothermal signal sensitivity to the implantation dose in the absence of optical and carrier plasma-wave interference effects is estimated. Simulations of the photothermal amplitude and phase dose dependencies allow us to follow the dynamics of the thermal- and carrier plasma waves in an ion-implanted semiconductor. The validity of the proposed damage-based modeling approach to the problem of quantitative analysis of surface-modified semiconductors is analyzed. It is shown that t...

A quantitative analysis based on a new three-dimensional nonlinear theoretical model of the experimental fundamental nonlinear photothermal response from multilayer structures containing a tungsten layer is presented. Two sets of wafers, one with a very rough tungsten overlayer surface and another with a smooth polished tungsten surface have been studied. It is shown that the rough tungsten surface gives rise to a very strong nonlinear behavior of the thermal-wave field.

A general three-dimensional theoretical model for fundamental and harmonic response generation as a result of periodic heating of a system consisting of a nonlinear layer with temperature-dependent thermal conductivity and specific heat and a linear substrate is developed. Analysis of the fundamental component of the surface temperature shows that the nonlinear thermal conductivity alone does not affect the phase of the thermal-wave field. The efficiency of the thin nonlinear layer as an energy conversion filter that drives the harmonic response of the substrate is shown by the analysis of the limiting cases of the theoretical model.

Various representations of the dielectric functions of semiconducting materials have been proposed. We compare five different models for representing the dielectric functions of crystalline (c-) Si, amorphous (a-) Si, and c-Ge from 1.5 to 6.0 eV. The four-oscillator critical point with parity plus one-dimensional tight-binding model (CPP-1D) best represents c-Si. Different models best represent a-Si and c-Ge. These representations provided a basis for modeling variations encountered in semiconductor manufacturing.

Analytic representations of the dielectric function e are needed for the analysis of optical data of complex materials and structures. Here, we examine various harmonic-oscillator-based representations of the dielectric functions of the silicon-related materials, crystalline Si, amorphous Si, and silicon nitride. For crystalline semiconductors we develop a new representation with a prefactor proportional to ω−2, the expected response for materials with wavefunctions that are eigenfunctions of the momentum operator.

We show that a rotating-compensator ellipsometer (RCE) with a zero-order retarder can be used for broadband spectroscopy, for example from 200 to 800 nm, when the compensator retardation δ is known as a function of wavelength and sample properties are determined by least-squares methods. The resulting instrument offers the standard advantages of an RCE and is no less sensitive than a rotating-analyzer or -polarizer ellipsometer under worst-case conditions, where the sin (2ω t ) component vanishes at δ=180°C. Sensitivity and operation are illustrated by application to the measurement of crystalline Si.

A combination of the thermal wave and optical technologies was found to be advantageous in characterization of implants for ultrashallow junctions. Two sets of Si wafers implanted with boron and arsenic ions at low energies (0.5–5.0 keV) and high dose (5×1014 cm−2) were studied after implantation and prior to annealing. Signals obtained by using the thermal wave and optical methods exhibit a linear dependence on implantation energy below 2 keV for both implants. Results of the thermal wave and optical studies were also correlated to conventional TRIM calculations of crystalline damage and implanted ion concentration.

It is shown that the thermal wave (TW) nondestructive technology widely used in semiconductor industry for ion-implant monitoring can also be used for characterization of ultrashallow junctions created as a result of thermal annealing of ion implanted wafers. A set of Si wafers implanted with boron at energies 0.2–0.5 keV and implantation doses in the range of 1014–1015 cm−2 thermally annealed at different temperatures (950–1100 °C) has been studied. For all samples, the TW signal is found to vary linearly with junction depth and is shown to exhibit a very good correlation with secondary ion mass spectrometry data. A special processing of experimental data using both the TW quadrature and in-phase signal components allowing for resolution of effects introduced by different implantation doses, energies, and annealing temperatures is discussed.

Beam‐profile reflectometry is a new technique for measuring the thickness and optical constants of dielectric, semiconducting, and thin metal films. The technique consists of measuring the intensity profile of a highly focused beam reflected from the sample. By using a linearly polarized light source and a tightly focussed beam, the S‐ and P‐polarization reflectivities of the film are simultaneously obtained over a wide range of angles. The focusing also provides a submicrometer spot, thus allowing these measurements to be performed in very small geometries. How the information present in the reflectivity profiles can reveal information about as many as three unknown film parameters simultaneously is described, and results from film samples for which the multiparameter fitting capability was essential to the success of the measurement are also presented.

Low-intensity laser illumination has been found to induce recrystallization of amorphous layers in ion-implanted silicon wafers. With the conditions used here, the temperature rise is much lower than that usually required for annealing of amorphous silicon. Therefore, this is an observation of recombination-induced nonthermal recrystallization of amorphous silicon layers.

Thermal-wave measurements of high-dose ion implantation into silicon have been characterized. In order to evaluate this technique for use in production as an ion-implant monitor, correlations were performed between thermal-wave and four-point-probe sheet-resistance measurements on test wafers. On device wafers, thermal-wave measurements were correlated to contact resistance on resistor test structures.

Modulated optical reflectance (MOR) images of plastically-deformed silicon show slip bands created by the deformation, which are also visible in electron beam induced conductivity images. Annealing the material decreases the electrical activity of the dislocations, but has no effect on the MOR image. MOR measurements of implanted and annealed silicon wafers show that a high MOR response is caused by decreased diffusivity in the surface layer. We conclude that the MOR contrast of defects in silicon is due primarily to scattering by dislocations and ionized impurities, and that carrier recombination is not significant.

A new application for ultra-fast and repeatable in-die determination of CD structures at the ∼1 μm length scale using the BPR®/BPE® (Beam Profile Reflectometry/Ellipsometry) technologies on the Opti-Probe® OP9000 series system, is presented and summarized. Two structures were measured and analyzed, including a poly-silicon CD standard and an advanced poly-silicon recessed structure relevant to advanced memory devices. A focused beam spot (∼1 μm) and fast BPR data acquisition capability (∼17 ms) were utilized to perform high-resolution scans across wafer and within single die regions. Rotating Compensator Spectroscopic Ellipsometry (RCSE®) signals were also used to independently determine and compare to BPR results from data collected over larger areas (∼15 μm). The BPR/BPE and SE results for line CD were found to have high correlation. Further, model regression for SE data coupled with an artificial neural network model and fast BPR were utilized to measure and calculate 10,000 points across a 1 mm 2 area in a matter of minutes. Overall, the results were found to be repeatable and correlated well to CD-SEM analysis.

In this study, the optical properties of amorphous carbon (aC) ARC films are investigated using an Opti-probe OP7341, and a metrology solution that robustly measures a broad range of process conditions is presented. We find that the aC material is consistent with uni-axial anisotropy, and that this effect may have important implications for photolithography. These results are obtained through the combination of multiple technologies in one tool: spectroscopic ellipsometry (SE); spectroscopic reflectometry or broadband (BB), with a wavelength range of 190-840 nm; single wavelength (673 nm) but multiple incident angle beam profile reflectometry (BPR) and beam profile ellipsometry (BPE), and single wavelength (633nm) absolute ellipsometry (AE). The combination of technologies at multiple angles and wavelengths provides additional optical information and sensitivity not possible with single-technology approaches. A complex wavelength dependent anisotropy model was developed for this analysis, and is compared with a real anisotropy model. The complex anisotropy model and the effective medium approximation (EMA) with two and three components were applied to a set of 12 wafer set with thickness swing aC films in the range of 500-750 a as well as a second set of 23 pre- and post- etch wafers. The complex anisotropy model clearly has the advantage of best fit the BPR profiles along with the SE Fourier coefficients. The etch rate obtained by the complex anisotropy also showed a much narrower variation as compared with the EMA2 and EMA32 models with the real anisotropy.

Evaluation and qualification of lithographic exposure tools is a crucial step in establishing high volume manufacturing processes for IC manufacturers. The data sampling offered by scatterometry can be as dense as that from ECD (electrical CD) for the qualification of the tool. In this paper, the CDs obtained from scatterometry measurements are compared with those obtained by ECD (electrical CD) measurements to show the cross-slit and cross-scan tool characteristics. Since scatterometry is still an order of magnitude slower than ECD, data from various sampling plans will be compared. Another important consideration of this study is to use scatterometry to generate OPC (optical proximity correction) models for the 45nm and 32nm nodes. An accurate measurement of the process to fit the model becomes very crucial in the very deep sub-micron regime. Currently, SEM measurements are performed but they are slow and their precision is not adequate. In this paper, scatterometry measured data will also be compared with SEM data for OPC model fit.

A selection of thin Si layers grown epitaxially upon thick relaxed SiGe films were measured using the combination of optical metrology techniques available on the Opti-Probe 7341 system. The techniques used included in particular (i) angle resolved laser Beam Profile Reflectometry (BPR) with S and P polarization, (ii) Broad-band visible-DUV spectrophotometry (BB), and (iii) spectroscopic ellipsometry (SE). The measured parameters included the Ge-content of the relaxed SiGe layer, the thickness and optical dispersion of the thin Si layer, and the thickness of the native oxide layer on the strained Si. Strain in the Si layer can be recognized by a significant downwards shift in the energy of the E1 peak and in the magnitude of the E2 peak in the e2 dispersion curve, which is consistent with theoretical predictions when the strain in the layer is tensile. The thickness measurements of the Si layer made by the Opti-Probe were found to be in agreement with subsequent SIMS analysis to within 5Å for the strained-Si layer. Measurement precision for thickness was

Spectra of contact hole arrays with target diameters ranging from 106 to 131 nm and pattern pitch ranging from 220 to 300 nm are taken from an off-axis (65°) rotating compensator spectroscopic ellipsometry (RCSE).[1] 3-dimensional finite difference (FD3D) model developed by H. Chu,[2] is applied in the studies. To ensure accuracy of optical dispersion of each film, the simultaneous use of angle resolved beam profile reflectometry (BPR), broadband spectroscopic reflectometry (BB), and SE of an Opti-Probe 7341 are used for characterizing of the resist and BARC films. In particular, The extracted n&k dispersions are used to model the contact hole SE data using Therma-Wave's proprietary 3-dimensional RT/CD technology.[3,4] The performance of stability of both static and dynamic repeatability, uniformity, and correlation to other independent technology (i.e., SEM) will be presented in this paper.

In the 90nm node and beyond, Critical Dimension Uniformity (CDU) control is essential for today's high performance IC devices. The desired control of CDU is just under 2nm (3 sigma) across a 300mm wafer with 577 die. In this study we used an Opti-Probe 7341 RT/CD system that combines broadband (190-840 nm) spectroscopic ellipsometry (SE), spectroscopic reflectometry (BB), single wavelength (673 nm) beam profile reflectometry (BPR) and single wavelength (633nm) absolute ellipsometry (AE). All of the above technologies were used to characterize the optical dispersions of the individual films in the stack of interest, resist/barc/sion/poly/oxide/silicon. We then used these dispersion results and the SE and BB technologies to characterize the CDU of the patterned wafer. With the SE technology we measured CDU's in the range of 1.9-2.0 nm compared with BB measured CDU's in the range of 4-5 nm, both SE and BB wavelength were in the range of 240 nm-780 nm. However, if the wavelength range of SE and BB were extended to 190nm-840 nm, the CDU with SE stayed at the same level while that of BB reduced a factor of 2 to about 2.0-2.5 nm.

We demonstrate that a multi-technology approach enables the accurate characterization of the thickness and optical properties of Amorphous Carbon (α-C) films used in semiconductor manufacturing. Because the material is found to be highly birefringent, with its measured refractive index and extinction coefficient depending strongly upon the polarization and angle-of-incidence of the optical probe beam that is used, conventional single angle-of-incidence Spectroscopic Ellipsometry (SE) has insufficient information-content to detect the ordinary and extraordinary refractive indices with sufficient accuracy. On the other hand, Beam Profile Reflectometry® (BPR®) is particularly strong in this case because it measures the actual reflectances for both polarization components (rather than just the difference between them) at multiple angles-of-incidence. Furthermore, the fact that BPR is a single-wavelength technique means that no assumptions must be made about the optical dispersion of the film and an absolute measurement can be made. It is then possible to combine this with other, spectral technologies to obtain ordinary and extraordinary n and k at all wavelengths. We show that, to first order, the birefringence can be modeled by assuming a single “anisotropy parameter”, the ratio between the ordinary and extraordinary refractive indices (or, more correctly, the complex dielectric functions). Using this approach in combination with a simple Bruggeman effective-medium dispersion model enables robust characterization of these films for production.

This paper presents measurement results of 3-D contact hole profiles using RT/CD ® technology for various diameter-to-space (D/S) ratios and film stacks. The key controlling parameters (hole depth, diameter, sidewall angle, and hole openness, etc.) for lithography processing of contacts and vias were studied in terms of measurement sensitivity on samples with different pitches and D/S ratios and film stacks. Good correlation (R 2 ~0.99) between CD-SEM and RT/CD ® was obtained for the sample structures. The static and dynamic measurem ent stability of contact diameter and contact depth was better than 1 nm using simple profile modeling. Key words Metrology, spectroscopic ellipsometry, scatte rometry, critical dimension, contact hole. 1. INTRODUCTION The advance of semiconductor manufacturing into subwavelengt h patterning calls for much tighter control not only on the critical dimension (CD) and detailed profile of 2D line/space pairs but also of contact holes and vias on devices. As an advanced metrology altern ative to the conventional top-down CD-SEM and cross-section SEM technologies, optical scatterometery can provide accurate 2-D and 3-D structure profile information with better precision and throughput. Apart from CD-SEMs and cross-section SEMs which concentr ate on discrete single structures, the optical scatterometers generally make CD measurements on specially designed test areas which have regularly distributed 2D line/space pairs or 3D contact hole or vias for fast production process CD monitoring. The technology of real-time critical dimension (RT/CD

Thermal wave (TW) studies of ultra-shallow junctions (USJ) formed by ion implantation into a semiconductor wafer followed by rapid thermal annealing (RTP) are described. It is shown that using the TW technique allows for a simultaneous determination of the most important USJ parameters – depth and profile abruptness. Experimental results for junction depth and abruptness obtained on a set of B+-implanted, RTP-annealed USJ samples show better than 0.99 correlations to the corresponding secondary ion mass spectroscopy (SIMS) data.

Real-time optical CD metrology(1), employing fast numerical solutions to the diffraction of light from microelectronic features, is beginning to gain wide usage for sub-130nm IC processing. Applications of this method heretofore have concentrated on two steps in the patterning process: the 'develop inspect' (DI) step, at which point the pattern features are formed in the photoresist but prior to etch, and the 'final inspect' (FI) step, after the etch process has transferred the feature into the underlying IC layer(s). In this article, we examine another application: use of optical CD metrology for rapid characterization of stepper/scanner performance and optimization. In order to be useful to characterize a litho process, we found it necessary to expand the set of fitting parameters to include the pitch of the measured line/space array. This is due to two practical matters: first, the pitch imprinted on a wafer is the result of the pitch on reticle and second, the pitch on the wafer is a result of imaging magnification. As a result, this parameter can vary by several percent typically, for a pitch target of 240 to 350nm. Without taking this parameter into account, high-quality fitting of results over a full-field focus-exposure matrix (FEM) wafer, for example, is problematic. With the pitch included as a fitting parameter, it is possible to obtain excellent data-model fits across an entire FEM with a single metrology recipe.

We have developed a new Multi-domain Genetic Algorithm (MDGA) as a tool for advanced recipe development and applied it to metrology based on X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE). In our MDGA approach, multiple data sets are examined with the output being an optimal set of parameters for robust and rapid measurements. The data sets usually span the expected range of variations likely to be encountered in a process to be monitored (e.g., the data sets correspond to different thickness but with the same density or dispersion).In one application involving XRR measurements, a set of Ti films with thickness of 200 a was plasma treated for 0 sec, 10 sec, 30 sec, 50 sec, and 100 sec. Although it was expected that the plasma treated Ti film had a higher density than the non-treated Ti film, we found that the plasma treated Ti film had to be modeled as a two-layer film stack: the plasma treated Ti on top of a regular Ti. Without the MDGA, the densities of the top plasma treated Ti and the bottom Ti traded off since they are so close. With the MDGA, the densities of the top and bottom Ti films were regarded as global optimization parameters while the thickness and roughness of each layer were allowed to vary as local parameters. Our results show that the MDGA can clearly separate the plasma treated Ti from the untreated Ti film across the entire wafer set. On the other hand normal non-linear regression methods cannot distinguish the plasma treated Ti from the untreated Ti. In an application using SE measurement of a bottom anti-reflective coating (BARC) material, a linescan of 11 points across a 200mm wafer was measured with the thickness of the BARC film treated as a local parameter while the dispersion was treated as a set of global parameters. With the help of the MDGA, the dispersion modeling of the BARC film captured two main features at ~ 4.77 eV (260nm) and ~ 5.07 eV(235nm), as well as three small peaks at 3.16 eV(392nm), 3.37 eV (368nm) and 3.53 eV (351nm). In this way, the measured dispersion of the BARC film is more representative of the entire wafer than any dispersion developed from a single point measurement.

We describe a new technique for measuring the thickness and optical constants of dielectric, semiconducting, and thin metal films. Beam profile reflectometry provides excellent precision for films as thin as 30 A and as thick as 20 000 A. The technique is also capable of simultaneous 2 and 3 parameter measurements and it performs all measurements with a submicron spot size.

High-k gate dielectric films with equivalent oxide thickness (EOT) of 3 nm or less are becoming the main theme of research and development in ultra-large-scale integrated circuits industry with device dimensions scaled down to less than 130 nm. Among the high-k gate dielectric materials hafnium dioxide (HfO2) is very promising with its high dielectric constant (approximately 30) and stability in contact with Si. The samples were prepared with a DC magnetron-reactive sputtering method and subsequently annealed in the furnace with a temperature range of 500- 850 degree(s)C. The thickness of the HfO2 varied from 3.5- 18nm with a hafnium silicate interface layer of approximately 1 nm. The electrical measurement showed that the breakdown voltage is inversely proportional to the physical thickness, suggesting the breakdown process occur at the HfO2 thin film rather than in the interface layer. To measure the physical thickness of hafnium dioxide and hafnium silicate interface simultaneously, a research grade bench top rotating compensator spectroscopic ellipsometry (RCSE) in the wavelength range of 195-915 nm was used. The dispersion of HfO2 film was characterized with a two-peak critical point (CP) model and the dispersion of the interface layer of hafnium silicate was characterized with a five-peak CP model. An interface layer thickness of 0.7-2 nm was found for all hafnium dioxide films on Si, depending on the process conditions such as annealing temperature and oxygen flow rate. The same wafers measured by RCSE were later studied by transmission electron microscopy (TEM). The thickness of hafnium dioxide and hafnium silicate determined by TEM is in good agreement with the noninvasive RCSE method.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A new approach to the issues of characterization of ion-implanted semiconductors using the thermal wave technology is presented. Experimental results obtained using a new multifrequency lateral-scanning system on a set of Si wafers implanted with Boron in the energy range of 0.2–5 keV and dose range 4.5×1014−1.1×1015 ions/cm2 show that the sensitivity to dose and energy can be significantly increased by using the new system. The concept of quantitative depth profiling using the calculation of the photothermal response from the ion-implantation induced damaged layers in Si is also discussed.

A general three-dimensional theoretical model is developed for the fundamental and harmonic photothermal response generation as a result of periodic heating of a system consisting of a nonlinear layer with temperature-dependent thermal conductivity and specific heat and a linear substrate. The efficiency of the thin nonlinear layer as an energy conversion filter that drives the harmonic response of the substrate is shown by the analysis of the limiting cases of the theoretical model.

A new photothermal system designed for the metrology and characterization of thin metal films is described. This system employs a new technology based on the precise scanning of the thermal-wave field by varying the pump-probe beam offset distance. The resulting set of photomodulated reflectance signal amplitude and phase offset scans recorded at multiple modulation frequencies is processed using an appropriate theoretical model to obtain the parameters of the wafer under study.

A quantitative analysis of the experimental fundamental nonlinear photothermal responses from multilayer structures containing a tungsten layer is presented. Two sets of wafers, one with a very rough tungsten overlayer surface and another with a smooth polished tungsten surface have been studied. It is shown that the rough tungsten surface causes a very strong nonlinear behavior of the thermal-wave field. The effective nonlinear thermal conductivity k(T) dependence for the rough tungsten films has been found to decrease with increasing thickness of the layer.

An analysis of a new photothermal system—META-PROBE™ (MP)—capabilities in measuring the thickness and thermal parameters of a single layer metal structures and of multilayer stacks is presented. Examples of MP applications include structures containing Al, Ti, TiN, and SiO2 layers of various thicknesses and processing history.

We developed a robust measurement recipe for six layer SOI film stack. Both spectrometer and BPR were combined to characterize the plate and storage polysilicons. A new global optimization method was developed to find the best solution in parameter spaces with up to 12 parameters. Such a recipe was applied to production wafers with over 50 site die mapping. The 5 day repeatability shows the measurements were stable and robust.

We have developed a novel technique for performing simple phase-sensitive optical measurements in a sub-micrometer area. We presently use this technique to measure film stacks commonly found in the semiconductor industry. This article explains the theory behind this technique and presents several examples demonstrating the capabilities of the system.

Measurements of ultra-thin films (

As indicated by the ITRS roadmap, obtaining accurate information on the electrically active dopant profile for sub-30-nm structures is a key issue. Presently, however, there is no conventional, probe-based (destructive) technique available satisfying the ITRS targeted depth (3%) and carrier level (5%−10%) reproducibility and accuracy. In this work, the authors explore the promising capabilities of nondestructive photomodulated optical reflectance (PMOR) techniques, based on the localized (micrometer beam size) detection of variations in the reflectivity of the sample, due to thermal and plasma (excess carrier) effects as can be generated by a modulated pump laser such as the Therma-Probe® (TP) system. Earlier and more recent work using low modulation (1 kHz) frequencies has shown that it is possible, but rather tedious, to extract the electric junction depth (at about 1018 cm−3) and carrier concentration of chemical vapor deposition grown (CVD) (boxlike) structures based on so-called power curves (where t...

We present an efficient method for calculating the reflectivity of three-dimensional gratings on multilayer films based on a finite-element, Green's function approach. Our method scales as NlogN, where N is the number of plane waves used in the expansion. Therefore, it is much more efficient than the commonly adopted rigorous-coupled-wave analysis (RCWA), which scales as N3. We demonstrate the effectiveness of this method by applying it to a two-dimensional periodic array of contact holes on a multilayer film. We find that our Green's function approach is about one order of magnitude faster than the RCWA approach when applied to typical contact holes considered in industry. For most cases, this method is efficient enough for application as a real-time, critical-dimension metrology tool.

As indicated by the International Technology Roadmap for Semiconductors (ITRS) (http://public.itrs.net/), obtaining accurate information on the electrically active dopant profile for sub-30nm structures is a key issue. Presently, however, there is no conventional destructive (probe based) technique available satisfying the ITRS targeted depth (3%) and carrier level (5%–10%) reproducibility and accuracy. In this work, we explore the promising capabilities of a nondestructive photomodulated reflectance technique, based on the local detection of variations in the reflectivity of the sample due to thermal and plasma (excess carrier) effects as can be generated by a modulated pump laser such as in the therma-probe (TP) system. Experimental data obtained on chemical vapor deposition grown layers will be discussed with respect to junction depth and active dopant (carrier) level sensitivity. A methodology to decouple the junction depth and peak carrier concentration information for unknown samples based on the co...

Boron and arsenic low-energy (200–5000 eV) implants are studied after implantation, prior to annealing. We present results of optical measurements that provide new information on the damage depth profile. In addition, a method for simultaneous determination of implant dose and energy is proposed. Thermal wave and spectroscopic methods are observed to support each other in the analysis of arsenic ultrashallow junctions. New results are reported on the boron induced implant damage and the necessity for a combined technology is addressed. A combination of optical spectroscopy and thermal wave techniques are shown to provide a highly repeatable, nondestructive metrology to assist in ultrashallow junction fabrication.

Absolute constraints, namely, the Schwarz inequality and a complementary expression derived by us, are used to obtain corresponding absolute constraints on the Fourier coefficients of the intensity transmitted through rotating-compensator polarimeters and ellipsometers. These expressions allow the investigation of artifacts that result in mixed or apparently mixed polarization states over the cross section of the beam, the averaging time of the detector, or the frequency passband of the dispersing element. Examples include multiple internal reflections or inhomogeneous strain within an element, scattered light, and other types of system and component defects that cannot be accessed by means of polarization-state data alone. We apply these results to our polarizer-sample-compensator-analyzer (PSCA) ellipsometer to illustrate capabilities. A simple analytic model is shown to give a quantitative description of depolarization in systems for which the resolution is finite and the retardation varies with wavelength.

Thermal wave physics is playing an ever increasing role in the on-line characterization of semiconductor materials and devices. This is especially true for thermal wave methods that employ laser beams for both the generation and detection of thermal waves. For the modulated reflectance method discussed here, the pump and probe beams are focused on the same spot. They therefore achieve the noncontact advantage of optical methods in addition to the optimum condition for high spatial resolution, a necessary condition for thermal wave measurements on product wafers.When a material is excited with an intensity-modulated laser beam or pump, a thermal wave is generated in the material and in the air above the sample. The material within this heated region will undergo a thermal expansion which can be detected with a probe beam interferometer or by deflecting the probe beam from the thermoelastic deformation of the surface. Since the complex refractive index of most materials depends on temperature, a modulated temperature will also induce a corresponding modulation in the refractive index and consequently a modulation on a probe beam passing anywhere near the thermal wave. A probe beam directed along the heated surface of the sample, for example, will be deflected as it passes through the heated region above the surface. This mirage effect can also be observed within the sample by directing a transmitting probe through the heated region beneath the surface. Likewise, using a probe beam directed onto the sample surface one can observe a modulation in reflection, transmission, or scattering. A related noncontact method is the photothermal measurement of infrared radiation emitted from the material's heated region. Note that with all these detection methods, thermal wave measurements can be, and most often are, done in air and at room temperature.

We report on the results of a study of the temporal behavior of the laser‐induced modulated optical reflectance from the surfaces of crystalline silicon wafers, epitaxial silicon films, and ion implanted but unannealed silicon wafers. The observed temporal behavior of this signal appears to be associated with the presence and temporal evolution of electronic surface states.

We have developed a one‐dimensional model for thermal‐wave depth profiling that provides expressions for the temperature at the surface of the sample and for the thermoelastic response beneath the surface. The model shows that elastic wave interference effects produce significant differences between samples with mechanically free and constrained surfaces, and that thermal‐ wave images of thermal conductivity variations are obtainable from the thermoelastic signal only if the front surface is mechanically free. We have also considered the case of subsurface heating and found that for heating occurring at depths of more than a few thermal diffusion lengths, the thermoelastic signal becomes independent of thermal conductivity variations. This has important implications for thermal‐wave image range and resolution.

We calculate the Kapitza resistance ${R}_{K}(T)$ for a Cu-${\mathrm{He}}^{4}$ interface using the acoustic mismatch theory of Khalatnikov and of Mazo and Onsager. Included in the calculation are the effects of: phonon attenuation in the Cu as well as impedance matching due to the increased He density near the interface. We calculate ${R}_{K}(T)$ for several values of attenuation in the Cu; detailed calculations are displayed for the case of equal attenuations for longitudinal and transverse waves in the solid. Also considered are different attenuation profiles in the Cu. We use a density profile calculated from compressibility data and the Van der Waals attractive force between He and the Cu substrate. Our model includes the effects of a solid layer of He at the Cu surface, i.e., in such a He layer both longitudinal and transverse waves are allowed. Included in our calculations are the effects of different density profiles for the He. The calculations indicate that for suitable choices of the physical parameters, the theoretical results for ${R}_{K}(T)$ agree in magnitude as well as $T$ dependence with the experimental data. Unfortunately, the important physical properties have not yet been experimentally determined and definitive test of this theory must await such data.

Using semi-classical transport theory, exact expressions are obtained for the low temperature phonon-drag contribution to the thermoelectric tensor of a metal in a high transverse magnetic field, H. It is shown that the off diagonal elements (exy and eyx)of the thermoelectric tensor to leading order go as 1/H and, under certain symmetry conditions, are independent of the impurity scattering. It is also shown that under the same conditions the diagonal elements to leading order go as 1/H2. It is especially significant that exy does not contain any of the complex many-body effects predicted by Nielsen and Taylor1 and by Hasegawa2. Since exy is also amenable to measurement, the real possibility exists, for the first time, of testing the theory of phonon-drag in metals.

The method of optimal truncation is developed and applied to a variety of rotationally symmetric defects in elastic materials. Results are presented for oblate and prolate spheroidal voids, cracks, irregularly shaped voids, and compound inclusions. Most of the examples are in the frequency domain, but samples of time‐domain calculations are included. Physical interpretations of some features of the calculated amplitudes are given. Checks on accuracy of the results are emphasized and implemented.

Thermal wave technology has led to a new means of monitoring the dose and dose uniformity of ions implanted into wafers of silicon and gallium arsenide. New monitoring characteristics made available with this technique include nondestructive real-time dose measurements on product wafers as well as test wafers without annealing or other processing, dose measurements down to the 1E10 ions/cm 2 decade and up to 1E16 ions/cm 2 , dose measurements down to 5 keV ion energy and measurement through oxide or nitride overlayers. Furthermore, postanneal measurements of dose are also available in the high-dose range of 5E14-1E16 ions/cm 2 . In this paper we present examples to illustrate these capabilities.

Technique nouvelle de deflexion d'un faisceau laser induite par une onde thermique permettant de mesurer des epaisseurs de couches opaques ou transparentes de 500 a 25000 A. Application a la mesure des epaisseurs de couches minces de Al ou SiO 2 deposes sur du silicium