Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/40—Treatment after imagewise removal, e.g. baking

Definitions

• This invention relates to an improved process for thermally stabilizing photoresist images and is more particularly concerned with the thermal stabilization of photoresist images having high resolution geometries for use in microelectronic applications.
• the coated substrate is covered with a mask, exposed through the mask using appropriate UV radiation (often monochro ⁇ matic) and then developed using an alkaline developer.
• the image present on the mask is thereby reproduced on. the substrate, the areas of the photoresist layer, which were exposed to radiation by passage through the trans ⁇ parent portions of the mask, having been rendered soluble in the alkaline developer and therefore having been removed during the developing step.
• the unexposed portions of the photoresist layer, corresponding to the opaque portions of the mask remain on the substrate.
• the developed image layer and substrate is then exposedto a post-development bake, to cure the photoresist remaining on the substrate and enhance the adhesion thereof to the substrate, before subjecting the image and substrate to the pattern generation step.
• the thermal curing of the photoresist may also take place if the photoresist and substrate are subjected to a later step involving exposure to heat and, in such circum ⁇ stances, a specific post-development bake may not be required.
• the pattern generation step comprises etch ⁇ ing, ion implantation doping, metal deposition and the like to produce the final desired image (e.g. an inte- grated circuit) on the substrate. Thereafter, in a final step, the remaining photoresist is stripped from the substrate using appropriate solvents or other techniques known in the art.
• Ratios of photoresist thickness to line widths as high as 2:1 have been employed. This is commonly referred to in the art as the use of a high aspect ratio image. As will be apparent to one skilled in the art, the use of such high aspect ratios is often difficult to achieve especially when geometries shrink below 1 micron.
• Verelst et al. U.S. Patent 3,652,274 describes the preparation of a metal printing plate in which a photo ⁇ resist image is produced on the metal substrate and the image is developed using a hydrophobizing agent in the development fluid in order to increase the resistance of the image to the etching fluid used in the subsequent step.
• the hydrophobizing agent can be a fluoroalkyl- substituted organic silane.
• Tada et al. U.S. Patent 4,454,222 teaches the pre- paration of high resolution photoresist images using as the photoresist resin a polymer derived from trifluoro- ethyl-2-chloroacrylate and employing certain ketones as developers for the exposed image.
• Another object of the invention is to dye the photo ⁇ resist after exposure and development to make it visible for inspection purposes.
• the resist layer is so thin, typically less than 2 microns, that its inherent color is attenuated below visible recognition.
• the process of the invention which, in its broadest aspect, comprises a process for thermally stabilizing a photoresist image layer formed on a sub ⁇ strate wherein the image layer, prior to being subjected to a post-development bake, is coated with a protective film of a material which, as discussed in detail below, bonds to the photoresist but is substantially rinsed from the exposed substrate after post bake and which does not interfere with the desired operation of any of the subsequent steps of pattern generation including final removal of the photoresist image.
• the protective film also contains a dyestuff.
• the process of the invention can be utilized to thermally stabilize any type of photoresist image supported by a substrate.
• substrates such as silicon, silicon oxide, metals, nitrides, phosphides and the like.
• the latter is employed to thermally stabilize a high resolution positive photoresist image which has been prepared using a photoresist system based on a novolak resin.
• the invention also comprises high resolution photo ⁇ resist images supported on substrates, which images have been stabilized against distortion and other degradation which would otherwise be caused by the image during post- development processing of the substrate.
• the process of the invention can be employed to thermally stabilize any photoresist image formed on a substrate.
• the formation of the image on the substrate can be carried out by any of the proce ⁇ dures well known and conventionally used in the art.
• the steps to which the image and supporting substrate are subjected, before and after the process of the invention has been carried out on the image can be any of those well-known and practiced in the art.
• Illustrative of the steps involved in the preparation of a high (often sub-micron) resolution positive resist image, and its processing by plasma etching to produce geometries which can be sub-micron on silicon wafers and like substrates are those described by Grunwald et al. in a paper presented at the SPIE Conference on Micro- lithography, Santa Clara,_ California, March 1984.
• the process of the invention is interposed as a novel step in these known and conventionally used processes after the photoresist image has been developed on the substrate but preferably prior to the post-development baking step or prior to exposure to heat generated in the subsequent pattern generation step as discussed above.
• the novel process step of the invention comprises applying a coating of a protective film of thermally stabilizing, material to the surface of the photoresist image.
• the thermally stabilizing material can be any of a wide variety of high temperature resistant materials which meet certain parameters.
• the material is capable of being applied in solution or as a dispersion in an appropriate medium (preferably water) to form a thin film by coating using spin coating and the like techniques conventionally employed in the art.
• the material bonds sufficiently to the surface of the photoresist image during the heating process so that, after post baking, excess material can be rinsed using appropriate solvents (preferably water) from other portions of the coated substrate without removing any significant amount of the material on the photoresist image.
• the material is such that it does not interfere with any of the subsequent steps, i.e. the steps of pattern generation and photoresist removal to which the treated image is to be subjected.
• the material when applied as a coating to the photoresist image serves to stabilize the latter to exposure to temperatures of at least about 140°C and preferably to temperatures at least as high as about 175°C.
• Illustra ⁇ tive of materials which meet the above criteria and which can be employed in the process of the invention are fluorocarbon surfactants, film forming polymers, chromium sulfate, trichloroacetic acid, chromotropic acid (4,5-dihydroxy-2,7-naphthalene-disulfonic acid) and salts thereof such as the di-alkali metal salts, and the like.
• fluorocarbon surfactants fluorocarbon surfactants
• film forming polymers chromium sulfate
• trichloroacetic acid chromotropic acid (4,5-dihydroxy-2,7-naphthalene-disulfonic acid) and salts thereof such as the di-alkali metal salts, and the like.
• perfluorcarbon surfactants which are employed as one of the thermally stabilizing materials in the novel process of the invention are a class of compounds well- known and recognized in the art.
• this class of compounds is characterized by the presence of a perfluoroalkyl group CF 3 -(CF 2 )- n united directly or through a poly ethylene group -(CH 2 )- m to a hydrophilic group such as a carboxylic, sulfonic or phosphonic acid group, either in the form of the free acid or a salt or ester thereof, a polyether moiety such as R-(CH 2 CH 2 -0-)x H wherein R is hydrogen or methyl, x has a value of about 8 to about 20, and quater ⁇ nary ammonium groups.
• perfluorocarbon surfactants are: (i) perfluorocarbon-carboxylic acids of the general formula
• n has a value of about 6 to about 16 and m has a value of 0 to about 8, and the alkali metal, ammonium and tertiary a ine salts of the above acids;
• n and m have the values set forth above, and the alkali metal, ammonium and tertiary amine salts of the above acids;
• n and m have the values set forth above , and the alkali metal , ammonium and tertiary amine salts of the above acids ;
• n and m have the values set forth above;
• Mixtures of two or more different perfluorocarbon sur ⁇ factants can be employed if desired provided that the combined amount of the surfactants in the mixture, which is employed in the coating solution used in the process of the invention, lies within the ranges set forth above.
• perfluorocarbon sur- factant While all the above types of perfluorocarbon sur- factant have some solubility in water or in a mixture of water and a lower aliphatic alcohol such as methanol, ethanol, isopropyl alcohol, and the like, the solubility can be enhanced, if desired or if necessary, by employ ⁇ ing a non-fluorine-containing surfactant in combination with the perfluorocarbon surfactant. Any of the sur ⁇ factants, anionic, cationic or non-ionic, known in the art can be employed for this purpose.
• Illustrative ' of the perfluorocarbon surfactants which can be employed in the process of the inventions re those which are available from E. I. duPont under the trademark ZONYL and those available from 3M Company under the trademark FLUORAD.
• film forming polymers which are employed as thermally stabilizing agents in the process of the invention are carboxymethyl cellulose, carboxy- ethyl cellulose, polyvinyl alcohol, polyvinylpyrroli- done, polyalkylene oxides such as polyethylene oxide, polypropylene oxide and the like, hydrolyzed collagen, and other gelatinous colloidal materials such as pectin, gum tragacanth, gum arabi ⁇ and the like.
• hydrolyzed collagen is inclusive of gelatin and glue derived from sources of collagen such as animal tissue, bones, sinews, hides and the like by hydrolysis (acid or alkaline) or by enzymolysis, as well as further hydro- lyzed versions of gelatin and glue.
• Gelatin and glue are very similar chemically but gelatin is the name given to the proteinaceous product obtained in a purity suitable for edible consumption while glue is the name given to the product obtained in a purity suitable only for non-food uses.
• a preferred film forming polymer for use in the present invention is gelatin. Any of the various grades of gelatin/ including Type A (acid) and Type B (alkali) can be employed.
• the bloom is typically within the range of about 100 to about 275 but the particular bloom is not critical.
• especially preferred film formers for use in the process of this invention are non-gelling hydrolysates of gelatin, such as those obtained from acid or alkaline hydrolysis of Type A or Type B gelatins, particularly those having molecular weights in the 1000 to 5000 range.
• the thermally stabilizing material is employed as a solution in water or in water-miscible solvents such as ethanol, isopropanol, and the like lower aliphatic alcohols, and is applied by any appro ⁇ priate coating technique such as dip-coating, roller coating, spray—coating, spin-coating and the like.
• Spin-coating is a particularly preferred technique in the processing of wafers.
• the application of the solution of the above material is carried out advantageously at ambient temper ⁇ ature but elevated temperatures, i.e. temperatures up to about 120°C, can be employed if desired, provided such temperatures have no adverse effect on the photoresist.
• the concentration of the thermally stabilizing material employed in the coating solution can vary over a wide range from about 0.1 about 10 percent by weight.
• the material is employed in a concentration of about 0.5 to about 5 percent by weight and, most prefer- ably, in a range of about 1 to about 2 percent by weight.
• the amount of thermally stabilizing material which is applied to the surface of the photoresist image in the above manner is not critical provided that the added film thickness is not so large as to alter significantly the geometry and profile of the image being coated.
• the spin-coating method of application is particularly advantageous because it leaves only a thin film on the image and any excess is spun-off.
• the coated image and supporting substrate is then subjected to the post-development bake normally employed in the conventional processes of the art dis ⁇ cussed above.
• This bake step is advantageously carried out at a temperature in the range of about 100 ⁇ C to about 190"C or higher provided that the particular temperature chosen in any given instance is such that no significant change of profile or critical dimensions (CDs) of the photoresist image is produced during the baking step.
• the time for which the baking is continued is not critical and is generally of the order of about 10 minutes to about 30 minutes.
• the time of baking employed in any given instance is dependent on the bake temperature employed and on the nature of the particular photoresist and protective coating employed.
• the most appropriate baking time for any given combination of reactants and bake temperatures can be readily deter ⁇ mined by a process of trial and error.
• the baking step is accomplished using equipment such as a convection oven conventionally employed in the art for this particular operation.
• the image and substrate are rinsed using water or appropriate water-miscible sol ⁇ vents, to remove material from areas other than the photoresist image but leaving the photoimage itself coated with a protective layer of the material.
• the solutions of thermally stabilizing agents employed to treat the photoresist in the above-described manner can, if desired, contain additives such as sur ⁇ factants, dyestuffs, stabilizers and the like provided that these additives do not in any way interfere with the desired result of thermally stabilizing the photo ⁇ resist or affect the subsequent performance of the photoresist.
• the inclusion of surfactants serves to lower the surface tension of the aqueous solution of film-forming polymeric material and improve the wettabil- ity of the surface of the photoresist which is normally hydrophobic.
• Surfactants which can be employed, advantageously in a concentration of about 0.05 to about 3 weight per cent, include anionic, cationic and non-ionic sur ⁇ factants.
• a preferred group of surfactants are the perfluorocarbons and phosphate esters. As will be obvious to one skilled in the art, no additional surfactant is required when the thermally stabilizing material employed in the process of the invention is a perfluorocarbon surfactant.
• perfluorocarbon surfactants are those which are available from E. I. duPont under the trademark ZONYL and those available from 3M Company under the trademark FLUORAD.
• phosphate ester surfactants are ethoxylated alcohol phosphate esters available from Jordan Chemical Company.
• any of the dyestuffs known in the art which are compatible with the solution of the thermally stable coating material, and which do not interfere with the thermally stabilizing action of the material or with the subsequent performance of the photoresist, can be employed.
• Illustrative of such dyestuffs are those of the xanthene type.
• the presence of the dyestuff in the coating composition and hence in the protective film deposited on the photoresist image greatly facilitates visual inspection of the image.
• the amount of dye i.e. the concentration in parts by weight, which it is necessary to incorporate into the photoresist in order to facilitate inspection of the coated image after application of the solution contain- ing the dye, will obviously vary depending upon the particular dye in question. In general, it has been found that the minimum amount of dye necessary in any given case is that which will produce an optical density in the solution of film forming polymer of not less than about 10 3 .
• Optical density (E) is defined by the equa ⁇ tion
• the process of the invention serves to impart, to the photoresist image which has been treated, the capability of resisting flow when exposed to tempera ⁇ tures as high as about 220°C. Accordingly, the image so treated is capable of withstanding the temperatures to which it is to be subjected in further processing of the substrate and image supported thereon whether this be by chemical etching or plasma etching and the like, with no unacceptable loss of integrity of the resist image profile. Further, the process of the invention does not interfere with the ease with which the photoresist can be stripped from the substrate when the final step of the overall process is reached.
• the process of the invention is readily carried out in standard equipment, which same equipment is used in other steps of the overall process of forming and end-processing the photoresist image on the substrate.
• process of the invention can be used to thermally stabilize any photoresist image supported on a substrate, it is of particular advantage when utilized in the production and processing of high resolution images required in the production of sub-micron circuit- ry and the like.
• process of the invention will be further illustrated below by reference to its use in treating positive photoresist images but it is to be clearly understood that it is not limited to treatment of such images and can be employed with any photoresist images.
• a silicon wafer with approximately 10,000 Angstroms of aluminum over 1,000 Angstroms of silicon dioxide was spun-coated at 5000 rpm with a high resolution, high con ⁇ trast, high aspect ratio positive photoresist system comprising a solvent blend solution of a novolak resin and a trihydroxybenzophenone ester of 2-diazo-l- oxonaphthoquinone-5-sulfonic acid [ULTRAMAC tm PR 914; MacDermid Inc. , Waterbury, CT] .
• the coated wafer was baked at 100"C for 30 minutes in a convection oven to evaporate the solvents from the coating before being exposed through a sub-micron geometry mask to UV light in a broad band contact exposure mode using an Oriel printer.
• the resulting coating had an average thickness of 1.2 microns.
• the exposed photoresist was developed using an alkaline developer [ULTRAMAC MF-28: MacDermid, Inc. ] to give an image of high resolution with walls approaching 90 degrees.
• the imaged wafer was rinsed with water on the vacuum chuck and flooded with an aqueous solution obtained by dissolving 10 g. of gelatin [granular, 100 bloom: Fisher Scientific Company] in sufficient water, at 50°C, to make 1 liter of solution.
• the wafer was then spun at 2500 rpm for 20 seconds leaving a thin film of gelatin on the photoresist image. The film dried during the spinning operation.
• Plasma Chamber DRYTEK Model 303
• Example 1 The procedure of Example 1 was repeated exactly as described except that a post bake temperature of 170"C was employed. Inspection of the photoresist image showed some edge rounding. Examole 3 .
• Example 1 The procedure of Example 1 was repeated exactly as described except that a post bake temperature of 180°C was employed. Inspection of the photoresist image after post- bake showed significant edge rounding similar to that observed in the absence of a gelatin coating layer. However, after plasma treatment and resist removal, the lines of the final image were found to be straight, sharp and clean with no evidence of distortion.
• Example 1 The procedure of Example 1 was repeated exactly as described except that the novolak resin photoresist system there used was replaced by each of the following commercially available novolak-based systems: PR64 and EPA914 (MacDermid Inc.) " In all cases the resulting photoresist image showed no significant distortion or other loss of integrity.
• Example 5 The procedure of Example 1 was repeated twice exactly as described except that
• Example 1 The procedure of Example 1 was repeated exactly as described except that 1.5 g. of surfactant [Jordaphos JA-60; Jordan Chemical Company: ethoxylated alcohol phosphate ester] was added to the gelatin solution employed in the coating. After plasma treatment the image was inspected and found to show no significant distortion or other loss of integrity of the walls of the image.
• surfactant Jordaphos JA-60; Jordan Chemical Company: ethoxylated alcohol phosphate ester
• Example 1 The procedure of Example 1 is repeated exactly as described except that 2 g. of Rhodamine B and 1.5 g. of surfactant [Jordaphos JA-60] are added to the gelatin solution employed in the coating.
• a silicon wafer with approximately 10,000 Angstroms of aluminum over 1,000 Angstroms of silicon dioxide was spun-coated at 5000 rpm with a high resolution, high contrast, high aspect ratio positive photoresist system comprising a solvent blend solution of novolak resin and a trihydroxybenzophenone ester of 2-diazo-l-nxonaphtho- quinone-5-sulfonic acid [ULTRAMAC tm PR 914; MacDermid, Inc., Waterbury, CT] .
• the coated wafer was baked at 100"C for 30 minutes in a convection oven to evaporate the solvents from the coating before being exposed through a sub-micron geometry mask to UV light in a broad band contact exposure mode using an Oriel printer.
• the resulting coating had an average thickness of 1.2 microns.
• the exposed photoresist was developed using an alkaline developer [ULTRAMAC MF-28: MacDermid, Inc.] to give an image of high resolution with walls approaching 90 degrees.
• the imaged wafer was rinsed with water on the vacuum chuck and flooded with an aqueous solution obtained by dissolving 10 g. of non-gelling gelatin hydrolysate [hydrolyzed Type B gelatin; molecular weight approximately 2000; protein content above 88%: Peter Cooper Corporations, Oak Creek, Wisconsin; treated to reduce sodium, potassium and iron below 1 ppm] in sufficient water to make 1 liter of solution.
• the wafer was then spun at 800 rpm for 20 seconds, followed by 4000 rpm for 10 seconds, leaving a thin film of the gelatin hydrolysate on the photoresist image.
• the film dried during the spinning operation.
• the wafer and image was then baked at 160°C for 30 minutes in a convection oven and then rinsed with water for 2 minutes in a rinser-drier. After rinsing and drying, the coated wafer was subjected to a plasma treatment under the following conditions:
• Plasma Chamber DRYTEK Model 303 Gas mixture : BC1 3 at 302 SCCM
• a silicon wafer with an oxide coating was spun- -coated at 5000 rpm with a high resolution, high contrast, high aspect ratio positive photoresist system comprising a solvent blend solution of a novolak resin and a trihydroxybenzophenone ester of 2-diazo-l-oxo-naph- thoquinone-5 -sul f onic ac id [ ULTRAMAC tm PR 914 ; MacDermid, Inc. , Waterbury, CT] .
• the resulting coating had an average thickness of 1.2 microns.
• the coated wafer was baked at 100 °C for 30 minutes in a convection oven to evaporate the solvents from the coating before being exposed through a submicron geometry mask to UV light in a broad band contact exposure mode using an Oriel printer.
• the exposed photoresist was developed using an alkaline developer [ULTRAMAC MF-28: MacDermid, Inc.] to give an image of high resolution with walls approaching 90 degrees.
• the wafer with image attached was rinsed with water, mounted in a vacuum chuck and flooded with an aqueous solution obtained by diluting 3 parts by weight of FLUORAD FC-99 [believed to be a 25% w/w aqueous solution of an amine salt of perfluoroalkyl- sulfonic acid; 3M Company] with 1 part by weight of water.
• the wafer was then spun at 6000 rpm for 20 seconds leaving a thin film of the perfluoroalkylsulfo- nate surfactant on the photoresist image. The film dried during the spinning operation.
• the wafer and image was then baked at 160 ⁇ C for 30 minutes in a convection oven and then rinsed with water. Inspection of 'the resulting image using a scanning electron microscope showed no significant distortion or other loss of integrity of the walls of the image.
• a series of positive photoresist high resolution images on sil icon wafers was prepared using the procedure described in Example 1 but varying the concentration of perf luoroalkylsulfonate surfactant (FLUORAD FC-99 used in all runs) , the nature of the photoresist, the spin time (20 seconds in all cases) in spin coating of the image, and the temperature of baking.
• the various parameters are summarized in TABLE 1 below.
• the images produced in all the runs were inspected using a scanning electron microscope and were found to have suffered no significant distortion or other loss of integrity of the walls of the image during the exposure to the baking temperature.
• Run 2K the photoresist, after the baking step, was stripped without difficulty using a proprietary resist stripper (S41; MacDermid, Inc.) at 100°C in 2.5 minutes.
• Novolak resin based positive resist Shipley Company, Inc.
• Novolak resin based positive resist Hunt Chemical 3.
• Novolak resin based positive resist MacDermid, Inc.
• Novolak resin based positive resist MacDermid, Inc. Run No. 2K was repeated without carrying out the coating with FC-99. Post baking at 175°C caused marked flow of the image and rendered the latter difficult to strip from the substrate.
• Example 1 The process of Example 1 was repeated exactly as described except that the fluorocarbon surfactant there used was replaced by a 0.5% w/w aqueous solution of FLUORAD FC 98 (potassium perfluoroalkylsulfonate; 3M Company) and the spin coating of the image with this surfactant was carried out for 20 second at 6000 rpm. The resulting image was found to have undergone no edge rounding or flow during the baking process (150"C for 30 minutes) .
• FLUORAD FC 98 potassium perfluoroalkylsulfonate
• Example 3 The process of Example 3 was repeated but replacing the FLUORAD FC98 solution by a 0.1% w/w aqueous solution of FLUORAD FC95 (potassium perfluoralkylsulfonates : 3M Company) . Again it was found that the so treated image suffered no edge rounding or flow during the baking process at 150°C for 30 minutes.
• Example 3 The process of Example 3 was repeated but replacing the FLUORAD FC98 solution by a 25% by weight solids solution of FLUORAD FC93 (ammonium perfluoroalkyl- sulfonates; 3M Company) in an isopropyl alcohol-water solution (27% by weight isopropyl alochol) . • Again it was found that the so treated image suffered no edge rounding or flow during the baking process at 150°C for 30 minutes. Examole 14
• Example 1 The process of Example 1 was repeated except that the FC surfactant was replaced by a solution of ZONYL FSA ("Dupont"), believed to be the lithium salt of a mixed fluorocarbon-hydrocarbon carboxylic acid (50% (wt) in a mixture of water and isopropyl alcohol) , spin-coat ⁇ ed at 5000 rpm. After a post bake of 150°C for 30 minutes, there was no image flow (but line edges were somewhat irregular) .
• ZONYL FSA ZONYL FSA
• Example 1 The process of Example 1 was repeated except that the FC surfactant was replaced by a solution of poly- vinyl alcohol (5% by wt. in water) , spin-coated at 5000 rpm. After a post bake at 140°C for 30 minutes a slight edge rounding was seen whereas in Example 1 (second portion, without FC) , edge-rounding was noted at 120 ⁇ C.
• Example 1 The process of Example 1 was repeated except that the FC surfactant was replaced by a solution of 10% by wt. chromium trioxide in water, spin-coated at 1000 rpm for 20 seconds. After a post bake at 140°C for 30 minutes, some partial edge-rounding was visible.
• Example 1 The process of Example 1 was repeated except that the FC surfactant was rep laced by a so lution of chromotropic acid, (disodium salt) , 10% wt. in water, spin-coated at 1000 rpm for 20 seconds . After a 140 " C post bake for 30 minutes , some partial edge-rounding was noted.
• chromotropic acid diisodium salt
• Plasma Treatment Si0
• the process of Example 1 was repeated and after treatment with the thermal stabilizing solution, the wafer was post baked at 140 ⁇ C for 30 minutes and exposed to plasma treatment under the following conditions: Plasma Chamber DRYTEK Model 202
• the resist thickness loss was 11%, with clean and sharp edge definition. There was no surface pitting on the resist nor any changes in the critical dimensions.
• a control wafer without the thermal stabilizing treatment showed significant edge rounding after the post bake and before plasma .treatment. After plasma, the pattern was transferred through the oxide leaving somewhat rounded edges and changes in the critical dimen ⁇ sions.
• Example 1 The process of Example 1 was repeated on a wafer of aluminum alloy (96% Al, 4% Cu) . After treatment with the thermal stabilizing solution, the wafer was post baked at 125°C for 30 minutes and subjected to plasma treatment.
• a control wafer without the thermal stabilizer treatment showed a 40% loss in resist thickness. There was edge rounding after the post bake which was trans ⁇ ferred to the image.

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  • 1986-11-12 WO PCT/US1986/002441 patent/WO1987003387A1/fr not_active Application Discontinuation
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