Search

Recent research on organic and polymeric semiconductors is directed towards highly ordered molecular structures in solid states. Through molecular design and engineering, it has been shown possible to control the molecular orientation and processing conditions of these materials as well as fine tuning their energy levels and color emissions. Thin film field-effect transistors (FETs) have been used as testing structures for evaluating the semiconducting properties of new organic semiconducting materials. Performance similar to amorphous-Si can now be realized with some organic materials. Large-scale integration of organic transistors has been demonstrated. In addition, several low cost novel non-lithographic patterning methods have been developed, which resulted in the first flexible electronic paper. The field-effect transistor device structure can also be utilized as a means to induce a great amount of charge carriers in organic thin films through the gate field. Using this type of structure, superconductivity was observed in a highly ordered conjugated regioregular poly(3-hexylthiophene).

formulated in a poly(norbornene/maleic anhydride/acrylic acid/tert-butyl acrylate) 193 nm single layer resin. A comparisonis made between formulations containing non-cholate Dl's, cholate based Dl's and formulations containing blends ofthe twodifferent types ofDI's. It was found that formulations containing the non-cholate materials tended to give T-topped profileswhile the formulations containing cholate based materials and blends containing as little as 1% cholate based DI did not.Keywords:Dissolution Inhibitors, 193 nm, blending.

We report on a study of the chemical and lithographic behavior of two types of base additives. One class of materials that we will report on are aminosulfonate onium salts, we report a study of both the thermal stability and the lithographic behavior imparted by these as a function of chemical structure. It will be shown that the decomposition temperature is a function of the basicity (nucleophilicity) of the counter anion but this can be countered by appropriate choice on onium cation. We will also discuss the lithographic performance of formulations containing transparent ammonium carboxylate bases. It will be shown that these materials provide for comparable lithographic to a standard formulation containing an amine additive. Since carboxylates and aminosulfonates are far less nucleophilic than amine additives these additives may be useful because they will not have the tendency to interact with electrophilic sites such as maleic anhydride derived repeat units.

The fundamental nature of the interactions between poly (norbornene-alt-maleic anhydride) based resins and cholate based dissolution inhibitors (DIs) were studied by FT-IR and NMR spectroscopy. We also studied the role that photo-acid generators (PAGs) play in the dissolution of these polymer resins. We attempted to disentangle the hydrophobic effects of the DIs and PAGs from the specific interactions (Van der Waal's, hydrogen bonding or ionic) that these materials have within the polymer system. We employed solubility studies of DIs and PAGs using cloud point determinations and dissolution inhibition experiments on spun films to determine the extent that hydrophobicity and polymer interactions play in development. We found that for simple cholate derivatives the interactions with maleic anhydride repeating units parallel the dissolution inhibition sequence (t-butyllithocholate > t-butyldeoxycholate > t-butylcholate). For a wider range of cholate derivatives, the cloud point in water is a useful predictive tool, in that it takes into account both the hydrophobicity and the propensity to interact with other moieties. Thus for these materials, dissolution inhibition is governed by both interactions between the DI and the polymer, and the hydrophobic nature of the DIs. In contrast, for the PAGs, the cloud point is not a good predictive tool for dissolution inhibition. We found for onium salt materials, that the extent of dissolution inhibition is predicated by the size of the anion. For example, large sterically hindered anions which give rise to PAGs that exhibit poor solubility in water, paradoxically also show poor dissolution inhibition. This may be because the steric hinderance disfavors interactions with the polymer matrix.

We have found that the progress of developer base into films of terpolymers of norbornene (NB)-maleic anhydride (MA) and acrylic acid (AA) is a percolation process with a critical site concentration of x(c) equals 0.084 which suggests that every acrylic acid site in the terpolymer of norbornene-maleic anhydride-acrylic acid can make 12 monomer units of the polymer water compatible. In practice these systems are being used with various tert-butyl esters of cholic acid as dissolution inhibitors. The cholates differ very much in their dissolution inhibition factors (lowest t-butyl cholate (1.3) to highest t-butyl lithocholate glutarate dimer (7.4). The change in these factors corrected for molarity follow the hydrophobic character of the dissolution as measured by log(p). A quick screening method has also been established to evaluate dissolution inhibitors based on our observation that the cloud point (the volume % acetone in a water/acetone which gives persistent cloudiness) parallels the dissolution inhibiting power as measured by the dissolution inhibition factor. For dissolution promotion, optimal results are obtained with t-butyl 1,3,5-cyclohexanetricarboxylate (f equals -6.3) and poorest results with t-butyl lithocholate (f equals -2.8); this appears to track with the number of carboxyl groups and the hydrophobicity of the carboxylic acids. The Rmax found for resist formulations tracks well with these findings. Another factor in determining the ultimate achievable contrast is the degree of acidolytic deprotection achieved by the material. It appears that acidolyticaly cleaveable carboxylate esters with a higher concentration of electron withdrawing groups such as t-butyl 1,3,5-cyclohexanetricarboxylate are more effective.

Influence of different functional groups on dissolution behavior of resist resins based on charge-transfer polymerization of cycloolefins with maleic anhydride was studied. tertButyl carboxylate moiety was used in all materials as an imaging group. Two approaches were identified for increase in the dissolution rate of totally deprotected polymers (Rmax). First, the Rmax value can be modified by changing the total amount of tertbutyl-protected and unprotected carboxylate moieties in the polymer. On the other hand, Rmax can be improved by introducing the base- hydrolyzable functionalities, such as a formate esters, into the polymer chain. It was established that such polymers are stable to hydrolysis in hydrophobic matrix but undergo quick hydrolysis in hydrophilic film. For example, a polymer in which the cycloolefin moiety has a formate side group displayed dissolution rate of approximately 10,000 angstrom/sec while an analogous polymer in which the cycloolefin moiety does not have a formate group showed a dissolution rate of approximately 500 angstrom/sec.

The effect of different photoadditives in high and low activation energy resist resins on resist outgassing during lithographicexposure was studied by quartz microbalance and gas chromatography! mass spectroscopy techniques. The resist outgassingwas analyzed both qualitatively and quantitatively and structure-property relashionships were developed between resistoutgassing and the molecular structure of photoacid generators and additives. The photoadditives examined include, aryliodonium perfluoroalkylsulfonates, triarylsulfonium perfluoroakylsulfonates, photogenerators of sulfamic acids (SweetPAG analogs), 2-nitrobenzyl PAG's and doxyl derivatives.Keywords: resist outgassing, photoacid generators, 193 nm, 248 nm, e-beam.

The fundamental nature of the interaction between the polymer matrix and the cholate based dissolution inhibitors are being studied by Fourier Transform-IR (FTIR) spectroscopy. It was found that the simple cholate derivatives undergo, in a blend with poly(norbornene-alt- maleic anhydride) and in a blend with the terpolymers poly(norbornene-alt-maleic anhydride-co-t-butylacrylate) and poly(norbornene-alt-maleic anhydride-co-acrylic acid), stronger interaction as seen by shifts in the OH region of the spectra than do blends with dimeric or oligomeric cholates.

A series of new polymers for 193 nm single layer resist based on maleic anhydride/cycloolefin systems with minimum amount of acrylate units were synthesized. In order to minimize the acrylate content, the cycloolefin moiety of the polymers was functionalized with side groups designed to either promotes adhesion to silicon substrate and/or impart the imaging functionality. All polymers were prepared by free-radical polymerization in moderate to high yields and were characterized by variety of techniques. The initial lithographic evaluation of the new resists was carried out. It was found that acrylates can be successfully replaced with appropriately substituted cycloolefins to provide good resolution. The etch resistance of the new materials generally improves with increase in cycloolefin content. The Onishi and Kunz type plots will be discussed.

Through a series of statistical design experiments we optimized the lithographic performance of a 193 nm single layer resists based on a norbornene-maleic anhydride matrix resin. Several interesting findings were found including that having the PEB temperature improved the performance of the resist. The polymer composition was found to strongly influence the lithographic performance of the resist. Variables that we examined included acrylate loading and blocking level. By optimizing the composition of the polymer, we have obtained resist with high etch resistance, square profiles and 0.130 micron dense line ultimate resolution in 0.5 micron thick films. The resist formulations are compatible with industry standard 0.262 N TMAH. During exposure the resists does not suffer from the outgassing of volatile species.

Single layer resists for 193 nm based upon resins derived from alternating copolymers of cycloolefins and maleic anhydride will be discussed. Our past work has examined the effect of polymer structure and composition, dissolution inhibitor structure and loading as well as the effect of the photoacid generator on the resist dissolution properties. In this paper, we will report upon on some of our recent investigations aimed at improving performance by use of a new class of photoreactive additives, photogenerators of aminosulfonic acids. One example of these, bis(t- butylphenyl)iodonium cyclamate, will be shown in our high activation 193 nm single layer resist system as being a useful photodecomposable base additive capable of limiting acid diffusion and alleviating post exposure bake delay effects. Finally, we will describe the utility of these materials in low activation energy (acetal based) resist systems.

Plasma polymerized methylsilane (PPMS) films exposed to UV light in the presence of air undergo photo-oxidation to produce a glass-like material, PPMSO, which can be selectively removed using aqueous HF based chemistries. We find that PPMS, used in such positive tone imaging processes, suffers from several drawbacks which make it an unattractive candidate for use as an imaging layer in positive tone resist schemes. We have used infrared and X- ray photoelectron spectroscopy to characterize the PPMS films. We have found evidence for the presence of bridging methylene groups in the Si-Si backbone of the PPMS polymer at the PPMS/Substrate interface. This thin underlayer of a polycarbosilane material is initially deposited in the PPMS CVD process and is insoluble in aqueous or vapor HF contributing to residue after the development. The limitation as to how rapidly PPMS films can be photo- oxidized in the presence of air using high-fluence laser steppers is determined by the rate of oxygen diffusion into the PPMS films during exposure. This reciprocity failure exhibited by PPMS films may limit positive tone PPMS processing from consideration in high-throughput UV based lithography.

We report on our recent investigations on the formulation and processing of 193 nm single layer photoresists based on alternating copolymers of cycloolefins with maleic anhydride. Resists formulated with cycloolefin copolymers are compatible with 0.262 N tetramethylammonium developers, have excellent adhesion, sensitivity, etch resistance and thermal flow properties. The effect of polymer structure and composition, dissolution inhibitor structure and loading as well as the effect of the photoacid generator on the resist dissolution properties was investigated. Based on the results high contrast formulations were evaluated on a GCA XLS (NA equals 0.53, 4X reduction optics) deep-UV stepper to exhibit 0.27 micrometer L/S pair resolution with excellent photosensitivity. Based on the dissolution properties and a spectroscopic examination of the resist, we have designed materials that show less than 0.17 micrometer L/S pair resolution with 193 nm exposures. In this paper, the formulation methodology is detailed and the most recent results upon both with 248 and 193 nm irradiation are described.

An overview is given of how the design of photoacid generators (PAGs) is critical to tuning both the lithographic and thermal properties of chemically amplified resist systems. The importance of PAG chemistry is illustrated with an ARCH resist system that contains acetal protecting groups removable with low activation energies. We detail the effect of PAG on the resist's resolution, depth of focus and thermal decomposition temperature.

We have developed a fundamentally new class of photoresist matrix resins for use in 193 and 248 nm lithography based on cycloolefin-maleic anhydride alternating copolymers. When used in three-component formulations with cholate-based dissolution inhibitions (DIs) and conventional photoacid generators, these copolymers afford positive-tone resists with potential sub-0.25 micrometer image fidelity. The resists exhibit high contrast (3 - 5.5) and high sensitivity (3 - 5 mJ/cm2 at 248 nm, depending on exact formulation) with low loadings (ca. 1 wt%) of triphenylsulfonium salt photoacid generators. These formulations are sufficiently transparent to be used at 193 nm without further modification.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

New positive tone deep UV resists with enhanced post-exposure delay (PED) latitude and process latitude are presented. Additives and functionalized sulfone terpolymers are tailored to optimize the dissolution properties and process stability. Adjustment of the dissolution rate is used as a design criterion for optimizing the resist performance. RX 165 resist, optimized using the above criteria, exhibits 0.25 micron line/space resolution, 0.8 micrometers focus latitude at 0.275 micrometers resolution, and 1 hour post exposure delay latitude.

When used in conjunction with a nitrobenzylester photoacid generator, poly(t-butoxycarbonyloxy-styrene-sulfone) deep-UV resist films exhibit high contrast, good resolution and linewidth stability. Use of overcoat materials dramatically reduce the surface inhibition problems, improve the latent image stability (time delay) and enhance the sensitivity by isolating the resist surface from environmental contaminants that react with the photogenerated acid. The photospeed of the all organic CAMP formulation is lower compared to the arsenate based system but can be improved by using more aggressive PEB conditions. Coded, 0.35 micrometers l/s pairs could be resolved in 1 micrometers thick resist films at a dose of 20-30 mJ/cm2. The exposure latitude is approximately equals 25% for 0.5 micrometers features, upon exposure with a GCA prototype deep-UV exposure tool with a NA equals 0.35 and 5x reduction optics. This paper will discuss the resolution, depth-of-focus, exposure latitude and processing characteristics obtained during the evaluation of this chemically amplified resist.

Copolymers of 4-tert-butoxycarbonyloxystyrene (TBS) and sulfur dioxide (SO2) have been found to act as sensitive x-ray ((lambda) equals 14 angstrom) and moderately sensitive electron-beam, single component, chemically amplified, aqueous base soluble positive acting resists. The x-ray and electron-beam response of these materials was a function of copolymer composition, where an increase in the sulfur dioxide content enhanced the resist sensitivity. Initial investigation into the radiation induced reaction mechanism provided evidence that acid formation occurs via polymer main chain scission. It is proposed that at the scission sites radical species are produced which in turn are responsible for the formation of the acidic moieties. Heat treatment of resist films after exposure converted the copolymers to poly(4- hydroxystyrene sulfone) and permitted the exposed film areas to be developed in an aqueous base solution. Preliminary lithographic evaluation has resolved 0.5 micrometers line and space patterns in 0.65 micrometers thick 1.75/1 TBS/SO2 resist films using an x-ray dose of 10 mJ/cm2. For a resist having a composition of 2.1/1 TBS/SO2, 0.25 micrometers line and space features where delineated using an electron-beam dose of 90 (mu) C/cm2 at 30 KV. In addition, minimal surface residue of the exposed areas of the resist film after development was observed when the time interval between the exposure and the post-exposure baking steps was varied from 2-10 minutes.

The chemistry and preliminary lithographic characteristics of chemically amplified positive acting (CAMP) resist formulations that meet the deep-UV lithography requirements of low optical density and high sensitivity were described recently.11 This paper examines the lithographic performance of a specific resist comprised of poly (t-butoxycarbonyloxystyrene-sulfur dioxide) and the onium salt, triphenylsulfonium hexafluoroarsenate as the photoacid generator. The lithographic performance was evaluated as a function of resin molecular properties, sensitizer loading effects and various process parameters. Exposures of optimum formulations of this resist (CAMP) were conducted on a GCA prototype deep-UV exposure tool with a NA = 0.35 and 5X reduction optics. Line/space patterns down to 0.35p.m with vertical wall profiles and 0.4.tm windows in 1-1.2im thick films were obtained. The paper will summarize the resolution, depth of focus, exposure latitude and processing characteristics obtained from the evaluation of CAMP and will discuss the pattern transfer results obtained with different substrates. The performance of CAMP was also evaluated on substrates with topography and the results will be presented.

Interest has steadily grown during the past few years in materials that are resistant to dry etching techniques that can be used in multilevel resist processes. This is perhaps a result of the greater demands placed on resist technology by increased device complexity and resolution requirements. The most well known multilevel resist methods are the two-level PCM (portable conformable mask, first described by B. J. Lin ) and the BTL trilevel processes. In the latter, the pattern defined in the top level is transfered first to a thin silicon dioxide layer and subsequently to the substrate by dry etching. A two-level photoresist process employing 200-300 nm irradiation of the upper layer followed by transfer of the resultant image into the lower layer by dry etching, combines the attractive features of both deep UV lithography and multilevel resist 3processing. Deep UV lithography affords improved resolution due to decreased diffraction, while multilevel processing2alleviates the problems associated with substrate topography and sur-face reflectivity. An outline of this resist processing scheme is shown in Figure 1. The substrate is coated first with a thick layer of an organic polymer that effectively planarizes the wafer surface. A layer of photoresist is then applied. Deep UV exposure and routine development of the top layer generates the desired pattern which is transferred to the substrate by oxygen RIE. One means of iiproving the resistance of a material to RIE is incorporation of silicon. Taylor and Wolf have reported that the addition of silicon containing compounds to organic polymers improves their resistance to erosion by an oxygen discharge, presumably by the formation of a protective layer of SiO2. Dialkyl siloxane polymers have been Eeported to be usable as negative deep UV resists in the two-level process described above. Anotheg negative, oxygen RIE resistant, deep UV resist has been reported by MacDonald et al. This material, a copolymer of trimethylsilylstyrene and chlorostyrene, shows excellent resistance to oxygen RIE. Similar trimethylsilylstyrene-chloromethylstyrene copolymers have been described by Suzuki et al. Negative resists, however, may swell during development and thus limit the degree of resolution. Poly(methyl methacrylate) (PMMA)3 and various substituted methacrylates 8,9 are well known, high resolution, positive deep UV resists. However they are not sufficiently resistant to an oxygen plasma to be usable in a two-level process employing RIE pattern transfer. Ideally, the etching rate ratios for the planarizing material vs. resist should be >10:1 and preferably >20:1 in order to minimize the effects of line width erosion and allow optimization of the thickness of the lower layer. This ratio may also be maximized through appropriate selection of the planarizing layer material. Our initial efforts have concentrated on effecting an improvement in the oxygen RIE resistance of PMMA, without destroying its high resolution characteristics. Improvements by factors of over 30 have been accomplished through the incorporation of siloxane substituted esters in the poly-mers; these effects are described as a function of silicon content. A preliminary litho-graphic evaluation of the materials is presented and while the etching rate ratio of HPR-204 vs. the P(DS-A-M) polymer employed is only ≈7 it is demonstrated that these new deep UV resists show promise as oxygen RIE masks for a two-level photoresist system employing dry etching pattern transfer techniques.

NPR, a material consisting of a novolac resin blended with poly(2-methyl-l-pentene sulfone) (PMPS), is an attractive positive electron beam resist. However, it exhibited a number of problems during processing. For example after the development step, NPR patterns were surrounded by a halo due to resist thickness differences in the region next to the exposed areas. Also, a thin residual film appeared in the developed regions. A study of these problems showed that immiscibility between the two NPR components was responsible for many of the results. Also, Fourier Transform Infra Red Spectroscopy showed that a low molecular weight PMPS, [n] - 20 cm3/g, considerably improved compatibility and reduced the defects mentioned above. For this reason a study of PMPS molecular parameters by Gel Permeation Chromatography (GPC), light scattering and intrinsic viscosity was undertaken. This study related the molecular variables to synthetic conditions and a reproducible synthesis was established. A new NPR system was prepared with 9% low molecular weight sulfone polymer. This resist exhibits good film quality after development and displays a sensitivity of 8pC/cm2 with excellent (0.25μm) resolution.

NPR (Novolac Positive Resist), a high resolution (0.25 pm) positive electron beam resist, is a blend of a cresol novolac and a polymeric dissolution inhibitor, poly(2- methyl-l-pentene sulfone) (PMPS) which undergoes spontaneous depolymerization during electron irradiation. Stringent control of processing parameters is necessary to obtain optimum resist sensitivity and contrast. The study of the chemistry of NPR has been discussed previously. In this paper we report on the role of processing variables on pattern quality and identify some of the conditions necessary for submicron resolution. The effect of NPR prebake temperature on resist pattern quality was studied and thermal analysis data compiled. The contrast of NPR as a function of the developing mode (dip, pubble, spray) was examined. The influence of electron beam parameters such as beam size and beam defocus on resist line edge quality was looked at extensively. The results and conclusions of these studies are reported in this paper. The application of NPR in trilevel resist systems was carefully evaluated. Excellent submicron resolution capabilities of the resist will be illustrated with scanning electron micrographs. Proximity effects were reduced through the use of "ghosting" techniques and examples of improved linewidth control will be shown.

A steady-state model has been proposed to predict the oxygen reactive-ion-etching resistance of organosilicon polymers. This model is based on a Silicon material balance and the assumption that a protective Si02 film forms and reaches a steady-state thickness on the surface of the polymer. At steady-state, the rate determining step is sputtering of the SiO2 film. This model predicts that the steady-state etching rate is proportional to the sputtering rate of Si02 and inversely proportional to the mass density of silicon in the polymer. It also predicts that the etching rate is independent of other chemical or physical properties of the material. This model accurately predicts the etching behavior of a silyl novolac polymer over a wide range of etching conditions. Two silyl methacrylates etch at the predicted rate under conditions typical of trilevel processing, but exceed the predicted rate under conditions where the average bombardment energy is lower. Surface analysis shows that the steady-state approximation is not valid for the methacrylates under these etching conditions; the oxide thickness continues to increase with time, even though a constant etching rate is achieved. Polymers with very low silicon content do not etch according to the model but form highly porous oxides that continuously accumulate on the surface of the polymer.

A novel terpolymer of a methylated phenol, p-trimethylsilylmethyl phenol and formaldehyde was synthesized. With a 9.7wt% Si content, the polymer displayed an RIE resistance 10 times greater than hard-baked HPR 204. The organosilicon novolac was employed as a base resin component of bilevel resist systems for both photo and electron-beam lithography. The low molecular weight polymer behaves as a positive resist when mixed with a dissolution inhibitor. In photo-lithography, the dissolution inhibitor was a diazoquinone based chemical which was converted to an acidic species during irradiation. In electron-beam lithography, poly (2-methyl-l-pentene sulfone) (PMPS), which depolymerizes upon electron-irradiation, functioned as the dissolution inhibitor. When the silylated novolac was used as a photoresist, coded 0.8μm line/space patterns were obtained with a sensitivity of -120 mJ/cm 2 . When employed as,an electron-beam resist coded 0.75μm line/space patterns were resolved with a dose of 8μC/cm 4 .

The random copolymer comprised of trimethylsilylme Abstract The random copolymer comprised of trimethy1silyImethy1 methacrylate (SI) and chloromethyl styrene (CMS) is shown to function as a negative acting e-beam and deep UV resist. The resist is prepared using free radical solution polymerization techniques. Reactivity ratios were calculated using the least squares treatment of Fineman-Ross, and were determined to be 0.49 and 0.54 for SI and CMS, respectively. This material exhibits etching resistance in an 0, reactive ion etching discharge, and is applicable to bilevel lithographic processes. The resist system exhibits an e-beam and deep UV sensitivity (D ) equal to 1.95 yC/cm2 and 18mj/cm2, respectively. The ratio of etching rates of the planarizing layer HPR-206 to this material is 12 to 1 in O2 . Preliminary results indicate this system to have submicron resolution capability. 1.0 INTRODUCTION Multi-layer resist systems have secured an important role in fabricating devices with geometries of l.Oym or less. The many inherent advantages of such systems have been documented previously by a number of co-workers in this field.^1'2' A consistent conclusion from all this work is that although multi-layer lithography provides the ability to build devices of submicron dimensions, the complexity associated with it must be simplified. Since the advent of tri-layer systems,(3^ an obvious simplification is to combine the properties of both the upper resist imaging layer and the O2 reactive ion etching (RIR) resistant masking layer (typically Si02) into one. One mechanism to accomplish this is to incorporate metal atoms into polymeric materials that function as resists.^^ Organosi1 icon species have been shown to provide excellent O2 RIE resistance. These materials are typically copolymerized with a second monomer which affords the radiation sensitivity necessary for imaging these types of resists.^5) This paper discloses a negative acting deep UV, and e-beam sensitive material suitable for bilevel lithography. The material is a copolymer comprised of trimethylsilylmethyl methacrylate and chloromethyl styrene. The method of preparation, physical characterization, and preliminary lithographic properties are presented. 2.0 Experimental 2.1 Synthesis Trimethylsilylmethyl methacrylate and chloromethyl styrene (mixed m,p isomers) were obtained from Petrarch Systems and Dow Chemical, respectively. Both monomers were freed of inhibitor by reduced pressure distillation. Copolymers were prepared using standard free-radical solution polymerization techniques. 2.2 Characterization Copolymer molecular weight was determined by high pressure size exclusion chromatography (HPSEC) using a Waters Model 510 pump, 401 differential refractometer, and a set of Dupont bimodal silanized columns. Copolymer composition and reactivity ratios were determined from elemental analysis for silicon and chlorine. Analyses were performed by Gailbraith Labs, Knoxville, Tenn. Glass transition temperatures (Tg) were determined using a Perkin-Elmer DSC-2. The temperature rate was 10°C/min with sample masses ranging from 10 to 20 mg. 2.3 Lithographic Evaluation Resist films, 0.5ym to l.Oym thick, were spun from a 10-12 w/v % solution of the polymers in 2-methoxyethyl acetate. Four inch Si substrates were used which were either bare, or precoated with 1.5ym of Hunt Photoresist (HPR-206) baked at 210°C for 2 hrs in air. Prior to exposure, the wafers were given a 30 min prebake at 80°C in air. Depending on which size features were being patterned, postbake conditions were varied between