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There is a strong demand to increase the routing density of the RDL to match the requirements for future microelectronic systems which are mainly miniaturization and performance. Photo-resists for structuring the metallization or acting as a mold for electroplating are common for very fine lines and spaces due to the developments in the front-end processing. For example chemical amplified Photo-resists are now moving in the back-end and wafer level packaging process. The results are mainly governed by the performance of the equipment i.e. the photo-tool. This is different for the permanent dielectric polymer material. The major difference in photo-resists and dielectric photo-polymer are the different functions of the material systems. Photo-resists are only temporary masks for subsequent process steps like etching and plating. This is different for the photo-polymers which are a permanent part of the future systems. In this paper a new technology is discussed which uses a laser scanning ablation process and BCB-Based Dry Film low k Permanent Polymer. Laser ablation of polymers is in principle not a new technology. Low speed and high cost was the major barrier. But the combination of a scanning technology together with quartz masks has opened this technology to overcome the limitation of the current photo-polymer process. The new technology is described in detail and the results of structuring BCB-Based Films down to less than 4 μm via diameter in a 15 μm thick film has been shown. The via side wall can be controlled by the fluence of the laser pulse. Test structures have been designed and fabricated to demonstrate the excellent electrical resistivity of the vias using a two-layer metallization process.

Flip-chip interconnect and 3-D packaging applications must utilize reliable, high-performance metallization products in order to produce highly-efficient, low-cost microelectronic devices. As the market moves to shrinking device architectural features and increasingly difficult pattern layouts, more demand is placed on the plating performance of the copper, nickel and lead-free solder products used to create these interconnects. Additionally, the move from traditional C4 bumping processes with lead-free solder to capping processes utilizing copper pillars with lead-free solder requires metal interfaces that are highly compatible in order to avoid defects that could occur. In this paper, next-generation products developed for copper pillar, nickel barrier, and lead-free solder plating will be introduced that are capable of delivering high-performance and highly reliable metallic interconnects. The additive packages that were selected and optimized allowing for increased rate of electrodeposition, uniform height control with controllable pillar shape and smooth surface morphology will be discussed. Furthermore, compatibility will be shown for a lead-free solder cap electrodeposited onto copper pillar structures, both with and without nickel barrier layers, on large pore features (≥50 μm diameter) and micro pore features (≤20 μm diameter) for both bumping and capping applications.

There has been significant activity in recent years to develop Non-Conductive Films (NCF), which are also known as Pre-Applied Underfills (PAUF) and Wafer Level Underfills (WLUF), for use in the High Volume Manufacturing (HVM) of 2.5D and 3D packages. They are essentially underfills in laminate film form. Like other underfills, they ensure the integrity of the electrical interconnects in a package by mitigating stress, acting as an adhesive to bind the package together, and encapsulating to protect against moisture and other unwanted materials that can compromise electrical connectivity. NCF's are seen as an alternative to the more traditional capillary underfills, especially in devices with finer pitch, smaller gap, and larger size. Since the NCF can be applied to multiple devices simultaneously, this new technology has an advantage over capillary underfills in HVM. These film-type underfills can be applied to wafers (PAUF, WLUF, NCF) or substrates (PAUF, NCF). Two key attributes of any underfill are no voiding and high reliability. No voiding is an essential requirement for high reliability. Voiding in NCF materials can result from the lamination and thermocompression bonding (TCB) processes. Voiding under the die can manifest from a variety of causes, including some of the following: (1) volatilization of materials in the coating, (2) dimensional changes within the coating during processing, (3) poor fundamental conformation to surface topography during film lamination and (4) ineffective air release during TCB due to un-optimized material flow. Unwanted issues such as reduced adhesion, solder shorting, increased moisture uptake and reduced stress mitigation can result from the presence of voids in the NCF. Pressure cure after joining is one method for eliminating voids in NCF materials. An earlier version of the NCF discussed in this study required pressure to eliminate voids after TCB. Pressure curing, however, adds process steps and is not accepted by all manufacturers. An improved NCF formulation and bonding process has resulted in a void-free NCF that does not require pressure cure for void elimination. This improved version not only addresses voiding after bonding, but also it has been proven to be very reliable in the presence of extreme temperatures, high humidity and temperature cycling. No one test is sufficient to adequately determine the long term reliability of NCF materials so a battery of tests was run to conduct a comprehensive assessment. The reliability evaluation results demonstrate that this newly developed NCF exhibits not only no voiding after TCB without the need for pressure cure, but also high reliability to various forms of temperature and humidity stress testing.

As the advancement of transistor nodes faces unprecedented challenges and work continues to extend Moore's law at the back end of the line (BEOL), packaging has become one of the fastest growing segments in the semiconductor industry. Lead-free soldering is one of the most critical steps in interconnection at the packaging level. The evolution of packaging requirements for various devices is driving changes in lead-free solder material selection, with lower melting point being an emerging criterion. Indium, because of its unique properties such as high thermal and electrical conductivity, excellent ductility, and particularly the low melting point of 157 °C along with the capability of alloying with other metals (e.g. tin) to bring the melting point further down, is drawing increasing attention to its application in packaging, as a candidate for low temperature solders. In the current study, indium capping on standard and micro copper pillars was demonstrated. It was also shown that stacking indium and tin layers could form (near) eutectic indium-tin alloys after reflow with a melting point as low as 119 °C. The experimental next-generation indium electroplating chemistry demonstrated a strong potential to further improve the performance, such as a smoother surface morphology compared to the current generation chemistry, towards demanding requirements for future packaging applications.

Flip-chip interconnect and 3-D packaging applications must utilize reliable lead-free solder joints in order to produce highly efficient, advanced microelectronic devices. The solder alloy most commonly utilized for these applications is SnAg, which is typically deposited by electroplating due to lower cost and greater reliability as compared to other methods. The electroplating performance and robustness of SnAg products for bumping and capping applications is highly dependent on the organic additives used in the process. Here, next-generation SnAg products that improve the rate of solder electrodeposition without compromising key requirements such as tight Ag% control, uniform height distribution and smooth surface morphology will be discussed. These plated solders were then evaluated for compatibility with bumping, capping and micro-capping applications.

Electroless Ni exhibits excellent plasma etch resistance and has been successfully employed as a hard etch mask in the fabrication of microelectronic and microelectromechanical components and templates for contact printing and biomedical applications. The use of a catalytic agent to initiate electroless deposition is known to directly affect the microstructure and properties of the deposited metal and thus the etch resistance and potential pattern resolution. We have previously reported the development of tin-free colloidal Pd(II) electroless catalysts, which are suitable for initiating the deposition of patterned EL Ni films for use as plasma etch masks. In this work we examine the effect of the Pd(II) precursor on feature resolution, Ni plating rate, and etch resistance. The etch selectivity of deposited films is determined by real-time endpoint detection using laser reflectometry. Both film morphology and the formation of nickel silicides were found to impact the etch resistance in thin (

SnAg solder is the industry standard for lead-free wafer bumping. SnAg electroplating chemistry for C4 bumping must be capable of achieving tight performance standards over a wide range of applications: mushroom or in-via electroplating, a diverse range of die designs and pattern densities, and over a wide range of plating rates, including high speeds to enable higher throughput. Beyond C4 applications, SnAg electroplating chemistries must also deliver strong performance on emerging micro-bumping and Cu pillar capping applications, leading to new materials challenges and new demands on both the solder and copper electroplating chemistries. Electrodeposited SnAg solder and Cu pillar performance is controlled by the specially formulated additives used during the electroplating process, paired with optimized high purity, low-alpha emitting inorganic metal salts and acids. Selection of robust, versatile SnAg and Cu plating chemistries capable of operation at high plating rate is critical to achieving optimized high volume, high throughput, and cost effective manufacturing. Improper additive selection can lead to a number of defects, which can manifest after plating, after reflow, or during reliability testing. These defects include as-plated defected or rough surface morphology, post-reflow macro-voiding, micro-voiding, bridging, and Ag 3 Sn plate formation, and poor height uniformity control across the die and wafer. These defects can lead to critical failures that lower yield and require wafer rework or wafer scrapping. To reduce the frequency of solder bumping, micro-bumping and Cu pillar capping defectivity, solder and Cu electroplating processes must be selected to enable wide process versatility and stability. In this paper, a wide range of bumping defects is introduced, root causes are discussed, and defect mitigation strategies are presented. Further, next-generation SnAg electroplating chemistries are presented that are designed to minimize solder defectivity and provide high performance, high yield, wide process windows, and high throughput options over a wide range of applications.

Channel-constrained metallization is described as a novel process for fabrication of metal features useful as etchmasks and electrical interconnects in microelectronics applications. The method creates a requisite surface reactivity template through patterned exposure and development of photoresist films to open channels to an underlying ligand self-assembled film. Subsequent electroless metal deposition occurs selectively at exposed ligand sites in the channels, which constrain lateral metal growth detrimental to feature critical dimension (CD) control during plating. A characterization of the individual process steps is presented using a positive tone photoresist system as an example. Determination of the exposure and development conditions that promote clearance of photoresist residues from the channels while maintaining adequate feature CD control is identified as an important issue in successfully performing the process. The process has been successfully demonstrated using optical exposure sources and is compatible with a range of substrates relevant for electronics applications, including Si. The high plasma etching selectivity of a thin Ni metal masking layer was used in the fabrication of high aspect ratio structures (≤5:1) in Si.

This communication describes our work in electrical, topological, and chemical micromodification of surfaces to modulate cellular form and function. We have addressed the surface physico-chemico-mechano properties of cell culture substrates that play a role in modulating cellular behavior. Single factorial model systems have been built using techniques adapted from microlithography. The tools and techniques of microfabrication, if harnessed and used correctly, can be enabling in elucidating the underlying principles and fundamental forces driving the cell–substrate interface. Additionally, the long-term practical applications of microfabrication in medicine and biomaterial/tissue engineering lie in enabling “communication” with living cells/tissues at the cellular and subcellular levels.

A new Pd(II) electroless metal deposition catalyst dispersion, PD2, prepared by quenching a PdCl 4 2 solution with HCl and excess NaCl following rapid hydrolysis at pH ∼ 7 and ∼0.8 mM NaCl is described. The precursors to the catalytic Pd(0) species are shown to be chloride-rich Pd(II) colloidal particles having negative surface charge by x-ray photoelectron spectroscopy, UV-visible spectroscopy, centrifugation, and chemical tests. The particles bind selectively and covalently at ligand-modified surfaces with complete surface coverage occurring for treatment times ≥2 min. Atomic force microscopy indicates that the average and maximum sizes of the bound particles are 9 ± 3 and 18 nm, respectively. A correspondingly narrow distribution (15 to 33 nm) of Ni particles of average size 21 ± 5 nm is obtained following metallization of catalyzed surfaces. The ability to control Ni particle morphology using PD2 is successfully exploited in the selective metallization of ∼15 nm features patterned by scanning tunneling microscopy. Metallization occurs with minimal distortion of feature geometries and no pattern degradation due to Ni overgrowth or bridging of adjacent features. Catalyst behavior is well described by a model in which domination of particle nucleation events and dispersion medium chemistry during colloid formation determine particle surface binding, stability, size, and dispersity

Two approaches were developed using an ambient atomic force microscope (AFM) to pattern metal in either positive or negative tone. The difference in surface chemical reactivity between exposed and unexposed regions was used to selectively attach colloidal Pd(II) nanoparticles capable of initiating the deposition of electroless (EL) Ni. In one case, EL Ni was selectively deposited in the unexposed regions of an organosilane film. In the second case, EL Ni was selectively deposited directly on an AFM oxide pattern. Based on the different binding selectivities of the Pd(II) catalysts, selective deposition on AFM patterns was attributed to the presence of a carbon residue in AFM oxide patterns formed under ambient conditions. The patterned Ni films were used as a mask for pattern transfer into the underlying substrate by reactive ion etching.

A new, additive, substrate metallization process, useful for high resolution lithography and microelectronic circuit fabrication has been developed. The process, which involves surface modification with a self-assembled monolayer (SAM) film, selective binding of a catalytic Pd colloid, and electroless (EL) metal deposition, was used to deposit EL Ni on p-type (100) silicon substrates with a native oxide layer. The deposits were characterized by current-potential (I-V) and capacitance-potential (C-V) measurements, and were compared to evaporatively deposited Ni films. Schottky barrier heights for both the EL and evaporated Ni contacts ranged between 0.6 to 0.7 eV; ∼0.1 to 0.2 eV higher than the typical value for Ni on atomically clean p-type silicon, as expected for contacts separated from the substrate by a thin insulating layer. The similarity of the EL and evaporated Ni barrier heights indicates that the buried organic SAM film and the Pd catalyst did not significantly alter the interfacial electrical characteristics. Heating the EL Ni deposits to over 300°C reduced the Schottky barrier height and increased the leakage current, although less so than on the evaporated contacts.

The deep UV (193 nm) photochemistry of the self-assembled monolayer film PEDA, H 2 NCH 2 CH 2 NHCH 2 C 6 H 4 CH 2 CH 2 Si(OCH 3 ) 3 , has been studied on Si and SiO 2 surfaces using UV and X-ray photoelectron spectroscopies, contact angle goniometry, and laser-desorption Fourier transform mass spectrometry. Mechanistic studies show that Si-C cleavage is the ultimate photochemical pathway; however, interpretation of the photochemical data is complicated by formation of a surface-bound intermediate, as well as adsorption of photoproducts to the substrate surface. Treatment of the exposed film with high ionic strength aqueous solutions is found to remove the adsorbed material. Patterned 193 nm exposure of PEDA SAM films on SiO 2 produces a surface template of reactive amine groups at relatively low doses (~ 400 mJ cm −2 ), which can be used for selective, high-resolution attachment or deposition of materials on the unexposed regions of the film.

Two photolithographic methods are described for the formation of patterned single or multiple DNA species on SiO2 substrates. In the first approach, substrates are treated with a photochemically labile organosilane monolayer film. Irradiation of these surfaces with patterned deep UV (193 nm) light results in patterned chemically reactive groups which are then reacted with heterobifunctional crosslinking molecules. Covalent attachment of modified synthetic DNA oligomers to the crosslinker results in stable DNA patterns. Alternatively, a photoresist is spin-coated over a silane film which had been previously modified with the heterobifunctional crosslinker. Upon patterned irradiation and subsequent development, the underlying crosslinker-modified layer is revealed, and is then reacted with a chemically modified DNA. Feature dimensions to 1 micron are observed when a single fluorescent DNA is attached to the surface. By performing sequential exposures, we have successfully immobilized two distinguishable DNA oligomers on a single surface. Synthetic DNA immobilized in this manner retains the ability to hybridize to its complementary strand, suggesting that these approaches may find utility in the development of miniaturized DNA-based biosensors.

An aqueous Pd(II) dispersion, useful as a catalyst for the selective electroless deposition of nickel metal at ligand-bearing surfaces, is prepared by the hydrolysis of PdCl 4 2− at pH 5 in an approximately 0.01 mol dm −3 NaCl solution. The catalyst dispersion is characterized by UV-visible absorption spectroscopy, electroless metallization, ultracentrifugation, and electrophoresis. The dispersion is found to consist of a distribution of anionic and uncharged Pd(II) species ranging in type from monomeric to colloidal. The species responsible for the initiation of electroless metal deposition at the ligand surface are identified as colloidal. Atomic force microscopy indicates that the colloidal catalysts are bound at the surface and range in diameter from approximately 4 to 53 nm with an avarage size of 30 ± 12 nm. The behavior of the catalyst dispersion is consistent with a model in which colloid formation is initiated by polymerization of monomeric precursors generated by successive hydrolytic Cl − loss from PdCl 4 2− , and deprotonation of the corresponding aquo-Pd(II) complex(es).

The deep ultraviolet (λ < ∼250 nm) photochemistry of chemisorbed organosilane self-assembled films of the type R(CH2)nSiO−surface where n = 0, 1, 2 and R = phenyl, naphthyl, or anthracenyl is explored. Photochemistry is examined using 193 and 248 nm laser irradiation as well as deep ultraviolet lamp sources. It is demonstrated for a variety of systems, including single and multiple rings as well as heterocycles, that the primary photochemical mechanism is cleavage of the Si−C bond. Photocleavage of the organic group generates a polar, wettable silanol surface that is amenable to subsequent remodification by organosilane chemisorption, allowing the fabrication of high-resolution patterns of chemical functional groups in a single molecular plane. The use of patterned monolayers as templates of reactivity for subsequent selective chemical reactions is demonstrated.

A new method is described for producing biomedically relevant polymers with precisely defined micron scale surface texture in the x, y, and z planes. Patterned Si templates were fabricated using photolithography to create a relief pattern in photoresist with lateral dimensions as small as I μm. Electroless Ni was selectively deposited in the trenches of the patterned substrate. The Ni served as a resilient mask for transferring the patterns onto the Si substrate to depths of up to 8.5 μm by anisotropic reactive ion etching with a fluorine-based plasma. The 3-dimensional (3-D) textured silicon substrates were used as robust, reusable molds for pattern transfer onto poly(dimethyl siloxane), low density poly(ethylene), poly(L-lactide), and poly(glycolide) by either casting or injection molding. The fidelity of the pattern transfer from the silicon substrates to the polymers was 90 to 95% in all three planes for all polymers for more than 60 transfers from a single wafer, as determined by scanning electron microscopy and atomic force microscopy. Further, the 3-D textured polymers were selectively modified to coat proteins either in the trenches or on the mesas by capillary modification or selective coating techniques. These selectively patterned 3-D polymer substrates may be useful for a variety of biomaterial applications. © 1996 John Wiley & Sons, Inc.

The adhesion of polyelectrolytes such as poly(aniline) (PANI), poly(pyrrole) (PPY), and sodium poly(styrene sulfonate) (PSS) to modified fluoropolymer and self-assembled monolayer film surfaces is investigated. Radio frequency glow discharge (RFGD) H2CH3OH plasma modification of poly(tetra-fluoroethylene-co-hexafluoropropylene) (FEP) produces surfaces of tunable chemical functionality, charge, and surface energy. The level of adhesion of the polycations to RFGD modified FEP surfaces is directly correlated with production of anionic sites by controlled defluorination of FEP; complete adhesion (withstands ultrasonication and tape peel testing) is achieved on surfaces with F:O ratios of ~4:1 or less. FEP substrates, modified by the RFGD plasma in selected regions, are used as templates for fabricating patterned electrically conductive PANI or PPY films, or patterned multilayer films constructed of alternating layers of PANI and PSS.

The surface morphology of a surface-bound colloidal Pd(II) catalyst and its effect on the particle sizes with the largest particles reaching approximately 50 nm in diameter. Catalyst surface coverages as low as 20% are found to be sufficient to initiate complete and homogeneous metallization. The distribution of particle sizes for the electroless metal deposit, found to be a function of plating time, is broad with the maximum Ni particle size exceeding 120 nm. Results indicate controlling the size of the bound catalyst is the principal determining factor in controlling the particle size of the electroless deposit. Modification of the surface by depleting the concentration of surface functional groups capable of binding catalyst is used to shift the size distribution of bound catalyst to smaller values. A resulting three-to fourfold reduction in the particle size of the electroless deposit is demonstrated.

Conductive, adherent copper films were deposited selectively on diamond substrates using ligating aminosilane self-assembled films and a Pd-based catalyst. Copper chemical vapor deposition (CVD) was performed at 444-456 K in a cold-walled chamber using 4 x 10 -3 Pa of (hexafluoroacetylacetonato)-copper(I)-trimethylvinylsilane mixed 1 :1 (v/v) with H 2 carrier gas. In the absence of the Pd catalyst, only isolated copper particles deposited on hydrogenated or aminosilane-coated diamond. The Pd catalyst enhanced selectivity for Cu deposition by a factor of 10 3 to 10 4 . Copper patterns with feature sizes to 1 μm were formed by lithographically patterning an aminosilane film on diamond using UV (193 nm) radiation and a contact mask prior to catalyst deposition and copper CVD. The Pd catalyst also enhanced Cu deposition on aminosilane-coated Si(100) and quartz substrates. Treating substrates with octadecylsilane or aminosilane self-assembled films without the bound Pd catalyst reduced copper deposition compared to Si(100) native oxide or hydrogenated diamond surfaces.

A new approach for the selective electroless (EL) metallization of surfaces is described. Surfaces are modified with a chemisorbed ligand‐bearing organosilane film, and then catalyzed with an aqueous Pd(II) catalyst solution. The catalyzed substrate is then immersed in an EL metal deposition bath to complete the metallization process. The ligating surfaces are produced by molecular self‐assembly of 2‐(trimethoxysilyl)ethyl‐2‐pyridine (PYR) on silicon or silica substrates. The catalyst consists of chloride‐containing aqueous Pd(II) solutions buffered at pH 5.0 to 6.4; oligomeric chloro and/or hydroxo‐bridged Pd(II) complexes act as the catalytic species at the surface. The activity of the catalyst has been characterized and modeled as a function of solution pH, [Cl−], and time from preparation. Adhesion of the Pd(II) EL catalyst to the substrate involves covalent bond formation with the surface ligand. An average minimum Pd(II) level on the surface of ~1015 Pd atom cm2 is shown to be necessary to initiate EL metallization of the substrate with an EL Co bath. This process involves fewer steps and displays improved selectivity compared to processes that involve a conventional Pd/Sn catalyst. Fabrication of high resolution metal patterns using the new metallization chemistry in conjunction with deep UV patterning of PYR films is demonstrated.

Proteins were attached in defined geometric patterns on a surface. A prerequisite to making a pattern of proteins is generation of surfaces resistant to nonspecific protein adsorption. This was accomplished via oxidation of the thiol terminus of an organosilane self-assembled monolayer film by deep ultraviolet (DUV) irradiation. The resultant surface exhibited marked resistance to protein adsorption. Using a mask to protect regions of the silanized surface from irradiation, proteins were selectively adsorbed or attached via covalent linkage at locations protected from the DUV light. Antibodies immobilized in patterns using this procedure retained their antigen-binding capability. Thus chemistry and DUV lithography were combined to create patterns of active biomolecules which could be used in the microfabrication of electronic devices and biosensors.

A new Pd(II) electroless metal deposition catalyst dispersion, PD2, prepared by quenching a PdCl 4 2 solution with HCl and excess NaCl following rapid hydrolysis at pH ∼ 7 and ∼0.8 mM NaCl is described. The precursors to the catalytic Pd(0) species are shown to be chloride-rich Pd(II) colloidal particles having negative surface charge by x-ray photoelectron spectroscopy, UV-visible spectroscopy, centrifugation, and chemical tests. The particles bind selectively and covalently at ligand-modified surfaces with complete surface coverage occurring for treatment times ≥2 min. Atomic force microscopy indicates that the average and maximum sizes of the bound particles are 9 ± 3 and 18 nm, respectively. A correspondingly narrow distribution (15 to 33 nm) of Ni particles of average size 21 ± 5 nm is obtained following metallization of catalyzed surfaces. The ability to control Ni particle morphology using PD2 is successfully exploited in the selective metallization of ∼15 nm features patterned by scanning tunneling microscopy. Metallization occurs with minimal distortion of feature geometries and no pattern degradation due to Ni overgrowth or bridging of adjacent features. Catalyst behavior is well described by a model in which domination of particle nucleation events and dispersion medium chemistry during colloid formation determine particle surface binding, stability, size, and dispersity

The photochemistry of organosilanw was used to (1) create mixed monolayers having continuously adjustable surface free energies and (2) affect high resolution adhesion and spatial orientation of biological cells on silica substrates. Monolayers were formed from two materials, an aminoalkylsilane, NH 2 (CH 2 ) 2 NH(CH 2 ) 3 Si(OCH 3 ) 3 (EDA), and a perfluorinated alkylsilane, CF 3 (CF 2 ) 5 (CH 2 ) 2 Si(CH 3 ) 2 Cl (13F), and were characterized by ellipsometry and water contact angle measurements

A top surface imaging approach for the fabrication of submicron features on solid substrates has been developed. A monolayer film is exposed to patterned deep ultraviolet radiation, then selectively metallized using electroless deposition such that a thin metal layer (200-400 A) is deposited only in the unexposed areas. The film/metal assembly is a highly effective mask for reactive ion etching which can subsequently be stripped from the substrate after feature definition. Features with 0.3 μm line width in polysilicon and working transistor test structures have been produced using this process

Patterned deep UV irradiation of organosilane self-assembled monolayer (SAM) films caused photocleavage of the organic groups in the molecule, and creates alternating regions of intact film and hydrophilic, surface silanol moieties. The exposed regions can undergo a second chemisorption reaction to produce an assembly of SAMs in the same molecular plane. The patterned SAM films can also act as a template for selective build-up of materials in the z-direction. The use of UV patterned silane SAM films as imaging layers for optical lithography has been demonstrated. The exposed films are selectively metallized using electroless deposition to produce a thin metal layer only in the unexposed areas. The film/metal assembly is a highly resistive barrier to reactive ion etching (RIE) for pattern transfer into the substrate. Features to 0.5 μm line width and working transistor test structures have been produced using this process.

Copper electroplating is one of the most important metallization technologies to produce metal contacts in the fabrication of crystalline silicon solar cells. It has been adopted in three areas, including: Interdigited Back Contact cell (IBC); Heterojunction with Intrinsic Thin layer (HIT); and Fully Plated Front Contact solar cells. Due to cost concerns, significant changes have been made in the silicon manufacturing process leading to thinner Si wafers. This change brings many challenges for copper metallization. One of the biggest challenges is to maintain a low internal stress of the copper deposit. This is key to avoid solar wafer warpage and maintain good adhesion. Copper deposits with high ductility are also desired to prevent or reduce the potential for the copper deposit to crack under stress over time. Ideal copper deposits exhibit low internal stress and high ductility. However, development of this plating chemistry is a challenge for the material supplier, as improvement in one attribute typically comes at the expense of another. Accordingly, there is need to develop organic additives for copper electroplating baths that alleviate internal stress in copper deposits as well as providing good ductility. In this paper, the performance of new acid copper electroplating bath capable of achieving both low internal stress and good ductility will be highlighted. Additive impact on copper deposit material properties and correlation between these properties and performance will be discussed

Goat immunoglobulin has been immobilized on glass substrates in a pattern defined photolithographically. The presence of the pattern has been verified by autoradiography, and the surfaces have been characterized by UV absorption measurements. The enzyme choline oxidase (ChO) also has been immobilized on silicon and initial work on amperometric detection of its activity has been begun. photolithographically. The success of the patterning

Organosilane precursor molecules, here (aminoethylaminomethyl)phenethyltrimethoxysilane, or PEDA, are chemisorbed onto a Si surface forming a monolayer thick film. These films are patterned using the scanning tunneling microscope to locally modify the chemical reactivity and are then used as a template for selective electroless plating of a thin Ni film. Reactive ion etching in a C2F6/O2 mixture transfers this pattern into the substrate. Improvement over previous lithographic performance is achieved by growing the films on a passivated and lightly oxidized Si surface, optimizing the patterning conditions, and improving the metallization and etch chemistry. In this way, we have generated deep trenches on the order of 15±4 nm width, with edge roughness of 3 nm. We believe this demonstrates the resolution limiting factors of this lithographic process.

Two research areas currently under study, lipid-based tubules and optical nanolithography, are highlighted, and the potential technological impact of the work is discussed. One of the first efforts in the liposome field was to try to improve liposome performance by making them stronger and more stable, so that they would be less likely to break open or leak their contents when sheared, heated or subjected to other forms of stress. This was achieved by cross-linking. Exposed lipid headgroups on the tubule surface proved to be susceptible to the attachment of catalysts, which allowed the microstructures to be electrolessly coated with metal. Once the lipid structures have been metalized, the resulting microstructures are quite robust, and compatible with most material environments. An optical lithography process has been developed and described for fabrication of high-resolution microstructures of metal and other materials on a variety of substrates. The process has applications in numerous areas of microcircuit lithography. >

With a scanning tunneling microscope (STM) operating in vacuum, we have studied the lithographic patterning of self‐assembling organosilane monolayer resist films. Where the organic group is benzyl chloride, the resist layer can be patterned with electrons down to 4 eV in energy. The patterned films have been used as templates for the electroless plating of thin Ni films. Linewidths down to ∼20 nm have been observed in scanning electron micrographs of the plated films. Still smaller features are observed in STM images of the exposed organosilane films.

A modified photolithographic approach to fabricating optically clear, 10 /spl mu/m and above wide multiple channels in biomedically relevant polymers like poly(dimethyl-siloxalane) is described. This approach allows control of size and shape of the channels and vessel wall architecture. Elimination of wet etchants, such as hydrofluoric acid, enables better control on the chemistry and surface topography of the formed channels.

Channel Constrained Metalization (CCM), which employs photoresist patterning to confine electroless metal deposition to selected regions, is an inexpensive alternative to metal sputtering or evaporation. Using CCM we deposited arrays of square nickel electrodes up to one micron in thickness and between 11 microns and 44 microns on the side. Gaps between the electrodes ranging from 1 micron to 4 microns were successfully patterned. In preliminary experiments, we have already achieved a reflectivity of up to 94% and an r.m.s. surface roughness of 3.3 nm evaluated on a pixel size (20 micron square) area.

Central to nanofabrication is the ability to transfer a pattern from an imaging layer to a device or structure. At the smallest dimensions (6. With our process 15 nm lines with 3.3 nm edge roughness have been fabricated in the plated Ni and etched into the underlying Si. The development of the resist process and the STM lithography will be described and the resolution of the approach will be discussed.

Light emitting electroluminescent devices have been studied in which the conjugated light emitting polymer is separated on both sides from the device electrodes by a film of nonconducting polyaniline. The devices operate under an AC applied potential.Aluminum, copper or gold serve as the metal electrodes. Flexible, completely organic polymer dispersed liquid crystal light valves have been fabricated from transparent plastic substrates on which a conducting film of polypyrrole has been deposited. A new concept, “microcontact printing”, is being investigated for patterning the polypyrrole.

hydrophobic monolayers tend to align liquid crystals homeotropically (molecules perpendicular to thesurface), the hydrophilic monolayers, in general, lead to a planar orientation. The quality of alignmentis found to depend on the degree of hydrophilicity as determined from contact angle measurements.INTRODUCTIONLiquid crystal devices require a preferential orientation of the molecules on the surface.1'2When a perpendicular orientation is required the surface is usually treated with surfactants. Typically,a planar orientation is obtained from mechanically rubbing a polymer coated surface. Although it hasbeen known that surfaces treated with silanes can control the alignment of liquid crystal molecules,no systematic study has been done on different types of silanes to find a correlation between the

Selective chemical vapor deposition (CVD) of conductive, adherent copper films was achieved on single-crystal and polycrystalline diamond substrates modified with a ligating aminosilane and a Pd-based catalyst. Only isolated copper particles deposited on hydrogenated or aminosilane-coated diamond substrates without Pd. The Pd catalyst enhanced selectivity by a factor of 103 to 104. Copper CVD was performed in a cold-walled chamber at 446-456 K and 8x10-3 Pa using hexafluoroacetylacetonate-Cu-trimethylvinylsilane in H2 (1:1). Surfaces were characterized with x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Patterned Cu features were formed by exposing the aminosilane films to patterned ultraviolet (193 nm) radiation prior to Pd-catalyst addition and Cu CVD.

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.

Soft x-ray synchrotron radiation, of wavelength 14 nm, has been used to pattern self- assembled monolayer films, which were then selectively metallized using electroless deposition. Organosilane precursors of the general type RSiX3 (R equals organic functional group; X equals Cl, OCH3) are used to form covalently bound ultrathin films by molecular self-assembly on Si wafers. These films are approximately one monolayer (approximately 1 nm) thick. X-ray exposure was used to remove or transform the R groups in selected areas of the film. The laterally patterned reactivity on the surface was then used as a template for the additive deposition of a thin layer of electroless nickel in the unexposed regions. The Ni metal layer can then be used as a plasma etch mask for pattern transfer. Metal features with linewidths to

Self-assembled monolayer (SAM) films of organosilanes have been characterized as surfaces for the spatially-controlled, selective attachment of single-stranded synthetic DNA. Geometric patterns of DNA on silica substrates have been created by photochemical modification of the SAMs to produce regions which promote or resist DNA attachment. The attachment of DNA to the modified surfaces was followed using UV spectroscopy, radioassay, ellipsometry, and enzyme-linked colorimetric assay. We have also demonstrated that immobilized DNA is capable of hybridization with a complementary strand under stringent conditions.

The use of low energy electrons for e-beam lithography in radiation sensitive materials is of interest because the detrimental effects of electron scattering can be eliminated. The scanning tunneling microscope (STM) is a convenient way to produce such electrons in a spatially localized beam. The STM has proved to be a valuable probe of resist materials and a viable method of lithography for high resolution patterning of semiconductor substrates. Thin layers of commercially available resist materials have been patterned and the patterns transferred into a substrate with a reactive ion etch. The absence of electron scattering is evidenced by the elimination of proximity effects and an improvement in resolution over that obtained with a tightly focussed 50 kV e-beam in identically prepared and processed resist films. Preliminary studies are also reported of STM lithography of ultrathin resists formed by self assembly techniques. The use of such thin films promises to increase further the resolution capability of STM based lithography. Issues related to the implementation of a low voltage lithography tool are discussed. A single tip instrument built with a fast STM like scanner appears viable for small scale nanolithography whereas a multiple tip approach is required for applications where throughput is an issue.

Significant improvements in high angle of attack aerodynamics, flight control systems and the use of thrust vectoring is providing current and anticipated aircraft with enhanced maneuverability. These aircraft generate unusual rates and accelerations which will severely affect pilot spatial orientation and situational awareness during air combat maneuvering. The developing technology of centrifuge flight simulation offers the prospect of ground-based flying qualities and human factors testing in this same environment. Centrifuge flight simulation technology, as implemented on the Dynamic Flight Simulator, has shown its value with F-14 flat spin and mishap investigations, preliminary enhanced fighter maneuverability studies, and physiological investigations in a realistic flight environment. Recent and current efforts are to expand this role for potential use as an enhanced maneuverability simulation tool. Specifically targeted for evaluation is the ability to perform piloted analyses of critical displays during high angle of attack enhanced maneuvering tasks. Improvements have been made to the Dynamic Flight Simulator motion base control and actuator quality, cockpit displays, data collection capability, and compatible tactical aircraft models. The evaluation involved analyzing improvements to motion fidelity and demonstrating the potential for addressing a broader class of aircraft research, development, test and evaluation issues. Limitations are separated into those inherent to the technology and those dependent on the Dynamic Flight Simulator implementation. Tradeoffs between control method and mission applications are shown. At B CCA CFS

A process for creating patterns of metal-binding ligands on a variety of substrates is described. Deep UV patterning of chemisorbed ligand-bearing organosilane films creates modified surfaces that can selectively bind species such as Pd(II) via a covalent metal ion-ligand interaction. Patterned surface-bound Pd(II) is used to initiate additive electroless metallization at the catalytic sites. Metal adhesion to the substrate is controlled by the nature of the catalyst-ligand interaction.