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Patent US7045273 - Amplification of structured resists utilizes a reaction between a ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA process for the amplification of structured resists utilizes a reaction between a nucleophilic group and an isocyanate group or thiocyanate group to link an amplification agent to a polymer present in the photoresist. The isocyanate group or the thiocyanate group in addition to the nucleophilic group...http://www.google.com/patents/US7045273?utm_source=gb-gplus-sharePatent US7045273 - Amplification of structured resists utilizes a reaction between a nucleophilic group and an isocyanate group or thiocyanate group to link an amplification agent to a polymer present in the photoresist. The isocyanate group or theAdvanced Patent SearchPublication numberUS7045273 B2Publication typeGrantApplication numberUS 10/285,050Publication dateMay 16, 2006Filing dateOct 31, 2002Priority dateOct 31, 2001Fee statusPaidAlso published asDE10153497A1, DE10153497B4, US20030124468Publication number10285050, 285050, US 7045273 B2, US 7045273B2, US-B2-7045273, US7045273 B2, US7045273B2InventorsJens Ferbitz, Werner Mormann, Jens Rottstegge, Christoph Hohle, Christian Eschbaumer, Michael SebaldOriginal AssigneeInfineon Technologies AgExport CitationBiBTeX, EndNote, RefManPatent Citations (10), Non-Patent Citations (2), Classifications (13), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetAmplification of structured resists utilizes a reaction between a nucleophilic group and an isocyanate group or thiocyanate group to link an amplification agent to a polymer present in the photoresist. The isocyanate group or theUS 7045273 B2Abstract A process for the amplification of structured resists utilizes a reaction between a nucleophilic group and an isocyanate group or thiocyanate group to link an amplification agent to a polymer present in the photoresist. The isocyanate group or the thiocyanate group in addition to the nucleophilic group form a reaction pair. One of the partners is provided on the polymer and the other partner on the amplification agent. The amplification reaction takes place more rapidly than a linkage to carboxylic anhydride groups. Furthermore, the amplification reaction permits the use of polymers that have high transparency at short wavelengths of less than 200 nm, in particular 157 nm.
forming a pair from the linkage group and the anchor group, one of the linkage group and the anchor group being a group having a structure �N═C═X, with X being a substituent selected from the group consisting of O and S, and the other of the linkage group and the anchor group being a nucleophilic group.
A process for the amplification of resist structures is described, for example, in commonly-assigned European Patent No. EP 0 395 917 B1, which corresponds to U.S. Pat. Nos. 5,234,794 and 5,234,793. There, the photoresists used for exposure wavelengths of 248 and 193 nm are structured and then chemically amplified in their etch resistance by the incorporation of organosilicon groups and thus form a sufficiently stable etch resist. For this purpose, the film-forming polymer of the photoresist includes reactive groups, for example anhydride groups. These anhydride groups react with basic groups of the silylating solution, which contains, for example, bifunctional aminosiloxanes, amide bonds being formed between polymer and silylating agent with crosslinking of the resist structure. Finally, a suitable wash solution washes away excess silylating agent. Resists as used for exposure to radiation having a wavelength of 248 to 193 nm permit layer thicknesses in the range from 140 to 200 nm. The amplification agent increases a volume in the horizontal and vertical direction during the silylation. A narrowing of trenches of the resist structure and hence an improvement in the resolution are therefore possible. This narrowing of trenches is referred to as �CARL� (Chemical Amplification of Resist Lines).
SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a process for silylating photoresists in the UV range that overcomes the hereinafore-mentioned disadvantages of the heretofore-known processes of this general type and that amplifies resist structures to increase the layer thickness of an already structured photoresist for the 157 nm technology.
(a) Applying a chemically amplified photoresist to a substrate. The photoresist contains the following components. A polymer including acid-labile groups that are eliminated upon the action of acid and liberate groups that increase the solubility of the polymer in aqueous alkaline developers, and which furthermore include anchor groups for the linkage of amplification agents. The anchor groups can be present in the form of a protected anchor group. The photoresist also contains a photo acid generator and a solvent. (b) Drying the photoresist to give a dried resist film. (c) Structuring the resist film to give a structured resist. (d) Optionally, liberating the anchor groups from the protected anchor groups. (e) Applying an amplification agent to the structured resist. The amplification agent includes at least one silicon-containing group and at least one linkage group for the linkage of the amplification agent to the anchor group of the polymer, so that the anchor group and the linkage group react with one another the for formation of a chemical bond and a covalent bond links the amplification agent to the polymer. (h) Removing excess amplification agent. The linkage group and anchor group form a pair formed from a group of the structure �N═C═X, where X═O or S, on the one hand, and a nucleophilic group on the other hand.
The process according to the invention uses the isocyanate group �N═C═O or the thiocyanate group �N═C═S as the group susceptible to nucleophilic attack. In comparison with the carboxylic anhydride group, these groups have higher reactivity so that the reaction rate and hence the film thickness increase can be increased compared with the carboxylic anhydride-containing polymers customary to date, or lower concentrations of silylating solution can be employed. A rapid, complete reaction is particularly advantageous with very thin resists where the dry etch resistance has to be particularly greatly increased. Furthermore, the isocyanate group and the thiocyanate group have about 50% lower absorption for radiation of a wavelength of less than 160 nm compared with the carboxylic anhydride group. A further advantage that results from this is that the transparency of the polymer contained in the resist can also be increased at low wavelengths in comparison with anhydride-containing polymers, which permits an increase in the layer thickness of the photoresist. The reaction occurring in the process according to the invention is shown below:
�The film-forming polymer contains, in the chain or as side groups, acid-labile groups that decrease the solubility of the polymer in polar solvents. Through the catalytic action of acid and, if required, a simultaneous thermal treatment, polar groups are produced on the polymer. For example, the following groups may be used as acid-labile groups: tert-alkyl ester, tert-butyl ester, tert-butoxycarbonyloxy, tetrahydrofuranyloxy, tetrahydropyranyloxy, tert-butyl ether, lactone, or acetal groups. Copolymerization of suitable monomers that include the acid-labile groups can introduce the acid-labile groups into the polymer. Preferably, used monomers here are those that have repeating units in the polymer with high transparency at short wavelengths, for example of 157 nm. Such repeating units have, for example, hydrocarbon groups in which fluorine atoms have replaced some or all of the hydrogen atoms. For example, carboxyl groups or in particular acidic hydroxyl groups are suitable as polar groups that are liberated after cleavage of the acid-labile group. Some repeating units that result in increased transparency of the polymer at short wavelengths of less than 200 nm, preferably less than 160 nm, in particular 157 nm, are shown as typical examples of a large number of suitable, repeating units.�
R1 is �H, �CH3, �CF3, or �CN and n is an integer from 1 to 10.
The resist generally has the following composition: film-forming polymer, 1�50% by weight, preferably 2�10% by weight; photo acid generator, 0.01�10% by weight, preferably 0.01�0.1% by weight; and solvent, 50�99% by weight, preferably 88�97% by weight.
The dried resist film is now structured in a customary manner. For this purpose, a latent image of the desired structure, which contains, in the exposed parts, the acid liberated from the photo acid generator, is first produced in the resist film by selective irradiation with the aid of a photomask or by direct irradiation with focused electrons or ions. In a heating step following the exposure (post exposure bake �PEB�), the acid-labile groups on the polymer are cleaved and polar groups are liberated by the catalytic effect of the acid produced by the exposure. In the exposed parts, the resist film therefore becomes soluble in an alkaline developer. In the subsequent development step, a 2.38% strength solution of tetramethylammonium hydroxide in water dissolves the exposed parts of the substrate and a positive relief pattern is thus produced in the resist film. In the exposed parts, the substrate is now bare; whereas the solid resist film protects the unexposed parts.
In order to accelerate the amplification reaction, a reaction accelerator may be added to the amplification agent. Suitable reaction accelerators are, for example, tertiary amines, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0 ]non-5-ene (DBN), 1,4-diazabicyclo[2.2.2]octane (DABCO), tetramethyl-guanidine (TMG), N-dimethylaminopropyl ethyl ether, bis(N-dimethylaminoethyl)methylamine, N-dimethylbenzylamine, N-methyl -N-dimethylaminoethylpiperazine and N-methylmorpholine. Further suitable reaction accelerators are described, for example, in Kleimann, Helmut, Die angewandte makromolekulare Chemie [Applied macromolecular chemistry], 98 (1981) 185�194.
R2 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, which may be straight-chain or branched and in which one or more hydrogen atoms may have been replaced by fluorine atoms, or is �CN or �R3�C(O)O�R4;
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A�1D are diagrammatic sectional views showing the steps of a process according to the invention;
FIG. 2A�2D are diagrammatic sectional views showing the process according to the invention in which a two-layer resist is used;
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawings in detail and first, particularly to FIGS. 1A�1D thereof, there is shown a sequence of process steps that are passed through on carrying out the process according to the invention. First, a photoresist 2 is produced on a substrate 1, as shown in FIG. 1A. The resist film contains a polymer having acid-labile groups and a photo acid generator. In this case, the substrate 1 is, for example, a silicon wafer. The resist film 2 is produced by adding a solution of the photoresist to the substrate 1, for example by spin-coating, and then evaporating the solvent. The resist film 2 is now exposed, an acid being liberated in the exposed parts 2 a from the photo acid generator as shown in FIG. 1B, while the resist film remains unchanged in the unexposed parts 2 b. This is followed by a heating step (PEB, post exposure bake) in which the acid-labile groups of the polymer are cleaved by the liberated acid in the exposed parts 2 a. The exposed resist is then developed with an aqueous alkaline solution, for example a 2.38% strength solution of tetramethylammonium hydroxide in water, the exposed parts 2 a, in which the polarity of the polymer contained in the resist is increased, being detached from the substrate 1. As shown in FIG. 1C, the unexposed sections 2 b now form raised parts by which the substrate 1 is protected, whereas the exposed parts 2 a form trenches 3 in which the substrate 1 is bare. In the parts 2 b, the anchor groups are now liberated for linkage of the amplification agent, by first exposing the parts 2 b and then heating the substrate with the exposed resist sections 2 b. The acid-labile groups of the polymer are now eliminated in the resist structures 2 b too and, for example, hydroxyl groups are liberated as anchor groups. A solution of an amplification agent that has isocyanate or thiocyanate groups is then added to the surface of the substrate 1 and of the resist sections 2 b. The resist structures 2 b are swollen by the solvent so that amplification agent can penetrate and can react with the anchor groups on the polymer. Incorporation of the amplification agent results in growth of the resist sections 2 b in the horizontal and vertical direction. The resist structures 2 b grow in their dimensions so that the state shown in FIG. 1D is reached. The layer thickness of the raised resist sections 2 b has increased and the width of the trenches 3 disposed between the raised resist sections 2 b has decreased. The resist structures 2 b include a core 2 c in which no amplification has taken place since the amplification agent could not diffuse into the interior parts of the resist structure 2 b. The core 2 c is surrounded by an amplified layer 2 d in which silicon-containing groups are linked to the polymer. The resist structure 2 d therefore has a greater layer thickness and a smaller width of the trenches 3 compared with the unamplified state shown in FIG. 1C. As a result of the amplified layer 2 b, which includes silicon-containing groups, the resist structures acquire increased etch resistance to a plasma, in particular an oxygen plasma. In the subsequent step, the structure of the trenches 3 is transferred by a plasma to the substrate 1.
FIGS. 2A�2D show the process sequence for a two-layer resist. This process variant permits the use of very thin layers of the photoresist and exact focusing of short-wave exposure radiation even when no flat surface is available on the substrate owing to the fact that electronic components have already been integrated. The substantial steps of the process correspond to the process sequence shown in FIG. 1. First, a bottom resist 4 which is not photosensitive and is formed, for example, from a novolak resin is applied to a substrate 1. A thin layer of the photoresist 2 is then applied to the layer of the bottom resist 4. The photoresist contains a polymer having acid-labile groups and a photo acid generator. The photoresist layer 2 is now exposed and developed as described in FIGS. 1B and 1C so that a state shown in FIG. 2B is reached. Raised sections 2 b have formed on the bottom resist 4, between which sections trenches 3 are disposed. The solution of an amplification agent which includes silicon-containing groups is now applied to the surface of the resist structure 2 b and the bare sections of the bottom resist 4. The resist structures 2 b are swollen by the solvent so that at the same time the amplification agent can penetrate and reacts with the anchor groups of the polymer contained in the resist. For this purpose, the polymer has isocyanate groups or thiocyanate groups and the amplification agent has a nucleophilic group, for example an amino group. There is an increase in the volume of the resist structures 2 b. The increase leads to a substantial film thickness increase. The constriction of the trenches 3 is less pronounced compared to the process shown in FIG. 1, owing to the smaller layer thickness of the photoresist 2. A state shown in FIG. 2C is reached. Amplified sections 2 d whose etch resistance to an oxygen plasma has been increased by the introduction of silicon-containing groups have formed on the bottom resist 4. The structure of the trenches 3 is now transferred to the bottom resist 4 by using an oxygen plasma. The bottom resist 4 is removed in the sections of the trenches 3 down to the substrate 1, so that the substrate 1 is bare in the trenches 3, and the trenches 3 are each bounded on both sides by raised parts that are formed in their upper section from a resist amplified by silicon-containing groups and in their lower section by the material of the bottom resist 4, as shown in FIG. 2D. The structure of the trenches 3 can now be etched into the substrate 1 by using a fluorine plasma (not shown).
EXAMPLE 1 To detect the silylation reaction of isocyanates with primary amines, a copolymer including 82 mol % of tert-butyl methacrylate and 18 mol % of isopropenyl isocyanate is dissolved in toluene. The structure of the polymer is shown below:
EXAMPLE 2 A 200 nm thick layer of the copolymer described in Example 1 is produced on a substrate. A silylation solution that contains 10% by weight of bisamino-oligodimethylsiloxane in heptane is applied to the layer of the copolymer. The amplification reaction is carried out for different reaction times and the film thickness increase of the copolymer film is then determined. After 60 seconds, a film thickness increase of 55 nm is obtained.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4491628 *Aug 23, 1982Jan 1, 1985International Business Machines CorporationPositive- and negative-working resist compositions with acid generating photoinitiator and polymer with acid labile groups pendant from polymer backboneUS5173393 *Apr 24, 1990Dec 22, 1992Siemens AktiengesellschaftEtch-resistant deep ultraviolet resist process having an aromatic treating step after developmentUS5234793 *Apr 24, 1990Aug 10, 1993Siemens AktiengesellschaftMethod for dimensionally accurate structure transfer in bilayer technique wherein a treating step with a bulging agent is employed after developmentUS5234794Mar 10, 1992Aug 10, 1993Siemens AktiengesellschaftMinimizing trench width by chemically bulging polymeric anhydride in structure with agent having amino groupUS5250375Dec 20, 1991Oct 5, 1993Siemens AktiengesellschaftPhotostructuring processUS5650261 *Oct 27, 1989Jul 22, 1997Rohm And Haas CompanyPositive acting photoresist comprising a photoacid, a photobase and a film forming acid-hardening resin systemUS20020068808 *Oct 11, 2001Jun 6, 2002Hiroyuki KometaniCatalyst comprises amilidine compound and unsaturated monocarboxylic acid extending pot life and rapid viscosity increasesUS20020146638 *Jan 26, 2001Oct 10, 2002Hiroshi ItoUsed to generate resist images; in the manufacture of integrated circuitsUS20030073043Jun 28, 2002Apr 17, 2003Jorg RottsteggeAmplification of resist structures of fluorinated resist polymers by structural growth of the structures by targeted chemical bonding of fluorinated oligomersJPH11338155A Title not available* Cited by examinerNon-Patent CitationsReference1Helmut Kleimann: "Die basenkatalysierte Isocyanat-Amin-Reaktion"[a base catalyzed isocyanate amino reaction], Die Angewandte Makromolekulare Chemie, vol. 98, 19981, pp. 185-194 (No. 1580).2 *Kleimann, Helmut, Die Angewandte Makromoleculare Chemie, 98 (1981), pp. 185-194 (No. 1580), Bayer AG, Polyurethan-Anwendungstechnik, D-5090 Leverkusen, translated title: Basically Catalyzed Isocyanate-Amine Reaction.* Cited by examinerClassifications U.S. Classification430/296, 430/270.1, 430/311, 430/330, 430/324, 430/315, 502/167, 430/326International ClassificationB01J31/00, G03F7/00, G03F7/40Cooperative ClassificationG03F7/405European ClassificationG03F7/40DLegal EventsDateCodeEventDescriptionNov 7, 2013FPAYFee paymentYear of fee payment: 8Jan 13, 2010ASAssignmentOwner name: QIMONDA AG, GERMANYFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INFINEON TECHNOLOGIES AG;REEL/FRAME:023773/0457Effective date: 20060425Nov 13, 2009FPAYFee paymentYear of fee payment: 4Oct 24, 2006CCCertificate of correctionMar 1, 2006ASAssignmentOwner name: INFINEON TECHNOLOGIES AG, GERMANYFree format text: CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE ADDRESS OF;ASSIGNORS:FERBITZ, JENS;MORMANN, WERNER;ROTTSTEGGE, JOERG;AND OTHERS;REEL/FRAME:017233/0279;SIGNING DATES FROM 20021219 TO 20030109Feb 15, 2006ASAssignmentOwner name: INFINEON TECHNOLOGIES AG, GERMANYFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:FERBITZ, JENS;MORMANN, WERNER;ROTTSTEGGE, JOERG;AND OTHERS;REEL/FRAME:017171/0984;SIGNING DATES FROM 20021219 TO 20030109RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google