Patent Application: US-201113583369-A

Abstract:
the present invention describes the synthesis of silicon - containing monomers and copolymers . the synthesis of a monomer , trimethyl - silane and subsequent synthesis of diblock copolymer with styrene , forming polystyrene - block - polytrimethylsilyl isoprene , and synthesis of diblock copolymer polystyrene - block - polymethacryloxymethyltrimethylsilane or ps - b - p . these silicon containing diblock copolymers have a variety of uses . one preferred application is as novel imprint template material with sub - 100 nm features for lithography .

Description:
due to the need for nanofeatures that can be etched , silicon - containing monomers were pursued . it is not intended that the present invention be limited by the nature of the silicon - containing monomer or that the present invention be limited to specific block polymers . however , to illustrate the invention , examples of various silicon - containing monomers and copolymers are provided . in one embodiment , a monomer trimethyl ( 2 - methylenebut - 3 - enyl ) silane was synthesized . after purification over nbuli , isoprene trimethyl ( 2 - methylenebut - 3 - enyl ) silane was successfully added on to a living polystyrene ( ps ) anion ( e ) in cyclohexane ( fig2 ). 1 h - nmr analysis showed a mol ratio of 83 : 17 sty : tmsi ( fig4 ). using the density of ps previously reported in the literature [ 11 ], and assuming the density of ptmsi is similar to that of polyisoprene ( pi ), the volume fraction of ps is approximated at 0 . 77 . small changes in the density of ptmsi produce relatively small changes in the volume fraction of ptmsi . according to literature [ 12 ], p ( s - b - i ) with fpi = 0 . 24 produces cylinders of pi , therefore a cylindrical morphology is expected . gpc determined the pdi of the ps aliquot and ps - b - ptmsi to be 1 . 00 and 1 . 02 , respectively with a total mn of 65 . 7 kda ( fig3 ). dsc traces of the polymer showed two tgs ( fig5 ): one at 103 ° c ., which is consistent with reported ps values , and another at − 34 ° c ., which is assumed to that of the ptmsi block . the reported tg for pi is − 73 ° c , 44 but due to the steric bulk of the tms group , this number seems to be reasonable . tmsi was successfully synthesized in good yield by a kumada coupling reaction [ 10 , 13 ] of chloroprene with ( trimethylsilyl ) methylmagnesium chloride ( fig1 ). anionic polymerization was selected for the diblock copolymer synthesis because of its capability to provide narrow polydispersity and its scalability . the diblock copolymer synthesis was successfully conducted in cyclohexane ( fig2 ) with good control of molecular weight and polydispersity ( table 1 ). the gel permeation chromatogram shown in fig3 demonstrates the successful growth of ps - b - ptmsi . the 1 h nmr spectrum ( fig4 ) shows a molar ratio of 0 . 84 : 0 . 16 ps : p ( tmsi ) when integrating the five aromatic styrene protons against both the single olefin proton in the backbone of the p ( tmsi ) block and the 9 tms protons ( table 2 ). using the previously reported density of ps [ 11 ] and assuming the density of p ( tmsi ) is similar to that of polyisoprene ( pi ), the volume fractions ( f ) of each block were calculated . fortunately , small changes in the density of p ( tmsi ) produce relatively small changes in the volume fraction of p ( tmsi ). according to existing literature [ 12 ], p ( s - b - i ) with f pi = 0 . 24 produces cylinders of pi , therefore a cylindrical morphology of the p ( tmsi ) block is expected . colburn et al conducted a series of experiments that concluded a formulation with a minimum of approximately 12 wt % si can serve as an etch barrier under standard o 2 rie conditions versus ps [ 6 ]. therefore , a block copolymer ( bc ) was designed that contained over 12 wt % silicon in one block but was all hydrocarbons ( i . e . lacking silicon ) in the other . this would provide the etch selectivity to yield a 3 - d pattern of self - assembled features . reagents . all reagents were purchased from sigma - aldrich chemical co . and used without further purification unless otherwise stated . ap410 and ap310 were purchased from az clariant . thf was purchased from jt baker . chloroprene 50 wt % in xylenes was purchased from pfaltz & amp ; bauer . cyclohexane was purified with a pure solv md - 2 solvent purification system . instrumentation . all 1 h and 13 c nmr spectra were recorded on a varian unity plus 400 mhz instrument . all chemical shifts are reported in ppm downfield from tms using the residual protonated solvent as an internal standard ( cdcl 3 , 1 h 7 . 26 ppm and 13 c 77 . 0 ppm ). molecular weight and polydispersity data were measured using an agilent 1100 series isopump and autosampler and a viscotek model 302 tetra detector platform with 3 iseries mixed bed high mw columns against polystyrene standards . hrms ( ci ) was obtained on a vg analytical zab2 - e instrument . ir data were recorded on a nicolet avatar 360 ft - ir and all peaks are reported in cm − 1 . glass transition temperatures ( t g ) were recorded on a ta q100 differential scanning calorimeter ( dsc ). monomer ( tmsi ). in a modification of a procedure from sakurai [ 13 ], a 250 ml rbf with condenser was charged with freshly ground mg turnings ( 2 . 2 g , 92 . 2 mmol ), a catalytic amount of dibromoethane , diethyl ether ( 100 ml ), and a stir bar . after stirring for 15 min at rt , the reaction mixture was brought to reflux , and chloromethyltrimethylsilane ( 10 . 6 ml , 76 . 8 mmol ) was added drop - wise over 30 min . in a separate 1 l round bottom flask ( rbf ) with addition funnel , a mixture of 1 , 3 - bis ( diphenylphosphino ) propane nickel ( ii ) chloride ( 1 . 3 g , 2 . 3 mmol ), freshly distilled chloroprene ( 9 . 0 ml , 97 . 6 mmol , bp = 58 - 61 ° c ., 760 torr ), and diethyl ether ( 500 ml ) was stirred at 0 ° c . after nearly complete mg consumption ( 2 h ), the pale - gray grignard solution was cooled , added drop - wise to the dark - red , chloroprene mixture over 30 min and stirred overnight at room temperature ( rt ). the yellow solution was quenched with h 2 o ( 500 ml ) and extracted with ether ( 3 × 250 ml ); the organic layers were combined , dried over mgso 4 , filtered and concentrated in vacuo . trimethyl -( 2 - methylenebut - 3 - enyl ) silane ( tmsi ) was isolated by distillation ( 57 - 60 ° c ., 66 torr ) in moderate yield ( 6 . 5 g , 60 %) as a clear liquid ; 1 h nmr ( cdcl 3 ) δ ppm : 6 . 380 ( ddd , j = 17 . 6 , 10 . 8 , 0 . 4 hz , 1h ), 5 . 121 ( dd , j = 17 . 6 , 0 . 4 hz , 1h ), 5 . 052 ( dd , j = 10 . 4 , 0 . 4 hz , 1h ), 4 . 903 ( m , 1h ), 4 . 794 ( s , 1h ), 1 . 711 ( d , j = 0 . 8 hz , 2h ), 0 . 007 ( s , 9h ); 13 c - nmr ( cdcl 3 ) δ ppm : 144 . 141 , 139 . 915 , 114 . 142 , 113 . 606 , 21 . 190 , − 1 . 250 ; ir ( nacl ) cm − 1 : 3084 , 2955 , 2897 , 1588 , 1248 , 851 ; hrms ( ci ) 140 . 1021 calc , 140 . 1023 found . purifications . all purifications and polymerizations were performed under an ar atmosphere using standard schlenk techniques . [ 14 ] styrene was vacuum distilled twice from di - n - butylmagnesium . tmsi was vacuum distilled twice from n - butyllithium . cyclohexane was purified with a pure solv md - 2 solvent purification system . the cyclohexane was run through a - 2 alumina to remove trace amounts of water followed by a supported q - 5 copper redox catalyst to remove oxygen [ 15 ]. polymer . the styrene polymerization was initiated with secbutyllithium at 40 ° c . in cyclohexane . after 12 h , a 5 ml aliquot of polystyrene ( ps ) was extracted from the reactor and terminated with degassed methanol . purified tmsi monomer was then added to the reactor drop - wise and reacted for 12 h , followed by addition of degassed methanol to quench the living anions . the block copolymer was precipitated in methanol , filtered and freeze dried in a 10 wt % benzene solution with 0 . 25 wt % butylated hydroxytoluene inhibitor to prevent oxidative degradation of the p ( tmsi ) backbone . due to the problems associated with styrene derivatives , monomer trimethyl ( 2 - methylenebut - 3 - enyl ) silane was synthesized . after purification over nbuli , isoprene trimethyl ( 2 - methylenebut - 3 - enyl ) silane was successfully added on to a living polystyrene ( ps ) anion in cyclohexane ( fig2 ). 1 h - nmr analysis showed a mol ratio of 83 : 17 sty : tmsi ( fig4 ). using the density of ps previously reported in the literature [ 11 ], and assuming the density of ptmsi is similar to that of polyisoprene ( pi ), the volume fraction of ps is approximated at 0 . 77 . small changes in the density of ptmsi produce relatively small changes in the volume fraction of ptmsi . according to existing literature 43 , p ( s - b - i ) with fpi = 0 . 24 produces cylinders of pi , therefore a cylindrical morphology is expected . gpc determined the pdi of the ps aliquot and ps - b - ptmsi to be 1 . 00 and 1 . 02 , respectively with a total mn of 65 . 7 kda ( fig3 ). dsc traces of the polymer showed two tgs ( fig5 ): one at 103 ° c ., which is consistent with reported ps values [ 16 ], and another at − 34 ° c ., which is assumed to that of the ptmsi block . the reported tg for pi is − 73 ° c . [ 16 ], but due to the steric bulk of the tms group , this number seems to be reasonable . in a modified procedure from sakurai [ 13 ], a 250 ml rbf with condenser was charged with freshly ground mg ( 2 . 2 g , 92 . 2 mmol ), a catalytic amount of dibromoethane , diethyl ether ( 100 ml ), and a stir bar . after stirring for 15 min at rt , the reaction mixture was brought to reflux , and chloromethyltrimethylsilane ( 10 . 6 ml , 76 . 8 mmol ) was added drop - wise over 30 min . in a separate 1 l rbf with addition funnel , a mixture of 1 , 3 - bis ( diphenylphosphino ) propane nickel ( ii ) chloride ( 1 . 3 g , 2 . 3 mmol ), freshly distilled chloroprene ( 9 . 0 ml , 97 . 6 mmol , bp = 58 - 61 ° c ., 760 ton ), and diethyl ether ( 500 ml ) was stirred at 0 ° c . after nearly complete mg consumption ( 2 h ), the pale - gray grignard solution was cooled , added drop - wise to the dark - red , chloroprene mixture over 30 min , and stirred overnight at rt . the yellow product was quenched with h 2 o ( 500 ml ) and extracted with ether ( 3 × 250 ml ); the organic layers were combined , dried over mgso 4 , filtered , and concentrated in vacuo . monomer 5 . 9 was isolated by distillation ( 57 - 60 ° c ., 66 ton ) as a clear liquid in moderate yield ( 6 . 5 g , 60 %); 1 h nmr ( cdcl 3 ) _ppm : 6 . 380 ( ddd , j = 17 . 6 , 10 . 8 , 0 . 4 hz , 1h ), 5 . 121 ( dd , j = 17 . 6 , 0 . 4 hz , 1h ), 5 . 052 ( dd , j = 10 . 4 , 0 . 4 hz , 1h ), 4 . 903 ( m , 1h ), 4 . 794 ( s , 1h ), 1 . 711 ( d , j = 0 . 8 hz , 2h ), 0 . 007 ( s , 9h ); 13 c - nmr ( cdcl 3 ) _ppm : 144 . 141 , 139 . 915 , 114 . 142 , 113 . 606 , 21 . 190 , − 1 . 250 ; ir ( nacl ) cm − 1 : 3084 , 2955 , 2897 , 1588 , 1248 , 851 ; hrms ( ci ) 140 . 1021 calc , 140 . 1023 found . all reactions and purification were conducted under ar atmosphere via standard schlenk line techniques [ 14 ]. all glassware was flame dried and purged with argon five times prior to exposure to any solvent or monomer . purification agents , n - butyllithium ( 2 . 5 m solution in hexanes , aldrich ), and dibutylmagnesium ( 1 m solution in heptane , aldrich ) were received as solutions , and the solvents were removed using vacuum , prior to mixing with monomers . exposure to air was prevented by storing and handling the reagent bottles under argon atmosphere inside a dry - box . lithium chloride ( licl , fluka ) was stored in a 120 ° c . oven and repeatedly flame dried and purged when placed inside the reactor . 1 , 1 ′- diphenylethylene ( dpe ) ( 97 %, aldrich ) was freeze - dried and vacuumdistilled twice over n - butyllithium and stored under argon atmosphere inside a dry - box . dpe , which is a high boiling liquid ( bp 270 - 272 ° c .) was distilled at 140 - 160 ° c . under continuous vacuum . high - purity argon , used for maintain inert conditions , was passed through an omi - 2 organometallic nanochem ® resin indicator / purification column ( air products ). methanol ( reagent grade , aldrich ) used as termination reagent , was degassed by sparging with argon for 45 min for removing air ( particularly oxygen ), which can potentially couple “ living ” polymer chains leading to undesired products . all other chemicals were used as purchased . styrene ( 99 %, 10 - 15 ppm p - tert - butylcatechol inhibitor , aldrich ) was freezedried and then purified by two successive distillations over solvent - dried dibutylmagnesium ( 0 . 1 mmol / g styrene ) at 40 ° c . for 2 h . the styrene burette was covered with aluminum foil to prevent photopolymerization and stored in a freezer . when ready for a reaction , the monomer was freeze - dried twice . trimethyl -( 2 - methylene - but - 3 - enyl ) silane was freeze - dried , and then dried over n - buli twice for at least 1 h at rt . after distilling a burrette , the monomer was freeze dried and used immediately . methacryloxymethyltrimethylsilane ( gelest , sim6485 . 5 ) was filtered through basic alumina on a bench top open of the air , and then freeze - dried in a solvent flask . after drying over calcium hydride two times for at least 1 h at rt , the monomer was distilled into a burrette . the monomer was covered in foil and stored in the freezer for up to two days . trimethyl -( 2 - methylene - but - 3 - enyl ) silane was freeze - dried , and then dried over n - buli twice for at least 1 h at rt . after distilling a burrette , the monomer was freeze dried and used immediately . a 500 ml reactor was loaded with a stir bar , flame dried , and cyclohexane was added into the reactor via a solvent flask . the total volume of cyclohexane used was set to so that the final concentration was 5 wt % monomer . after heating the reactor to 40 ° c ., sec - buli was added and stirred for 30 min to ensure a homogenous solution . approximately 20 drops of purified styrene was then added to the reaction via an airlock and a burrette . the color of the solution slowly turned orange , and after a 20 min seeding period , the remaining styrene was added . after stirring overnight , 20 drops of tmsi was added via the airlock and a burrette . after a 20 min of seeding , the remaining tmsi was added to the colorless reaction . to quench the reaction , degassed methanol ( 5 ml ) was added to the reaction and stirred for 30 min . a silicon containing methacryloxymethyltrimethylsilane ( mtmsma ) is commercially available from gelest , inc . due to its higher mw and boiling point compared to mma , the purification proved to be difficult . during the last distillation to remove alcohols , trioctylaluminum initiated mtmsma polymerization . attempts to remove alcohols by sodium hydride also led to polymerization . it was determined that alcohols could be removed by passing the monomer through an alumina plug , and then subjected to freeze , pump , thaw cycles and distillation over calcium hydride . this monomer was successfully incorporated ps - b - p ( mtmsma ) ( fig6 ). 1 h nmr analysis showed a mol ratio of 73 : 27 sty : mtmsma ( fig7 ). using the density of ps previously reported in the literature 12 and assuming the density of pmtmsma is similar to that of pmma , the volume fraction of ps is approximated at 0 . 66 . similarly to ps - b - ptmsi , small changes in the assumed density of p ( mtmsma ) produce relatively small changes in the its volume fraction . according to the literature , 11 this volume fraction should yield a cylindrical morphology . gpc determined the pdi of the ps aliquot and ps - b - ptmsi both to be 1 . 17 . the mn of the ps aliquot and final precipitated block was 60 . 0 and 75 . 2 kda , respectively ( fig8 ). methacryloxymethyltrimethylsilane ( mtmsma ) ( gelest , sim6485 . 5 ) was filtered through basic alumina on a bench top open of the air , and then freeze - dried in a solvent flask . after drying over calcium hydride two times for at least 1 h at rt , the monomer was distilled into a burrette . the monomer was covered in foil and stored in the freezer for up to two days . a 500 ml reactor was loaded with a stir bar and 5 molar equivalents of licl to initiator . licl suppresses side reactions during methacryloxymethyltrimethylsilane ( mtmsma ) propagation [ 17 ]. purified thf was added into the reactor via a solvent flask , and the reactor was cooled to − 72 ° c . in a dry ice / ipa bath . the total volume of thf used was set to so that the final concentration was 5 wt % monomer . after the solution temperature was stabilized at − 72 ° c ., secbuli was added and stirred for 5 min . approximately 20 drops of purified styrene was then added to the reaction via an airlock and a burrette . the color of the solution immediately turned orange , and after a 20 min seeding period , the remaining styrene was added . this was stirred for 4 h followed by addition of 5 molar equivalents of dpe to initiator . this addition turned the reaction a deep red . after 3 h of stirring , 20 drops of mtmsma was added to seed the mtmsma via the airlock and a burrette , and this caused the reaction to turn colorless . the reaction was stirred for 4 h after the remaining mtmsma was added . to quench the reaction , degassed methanol ( 5 ml ) was added to the reaction and stirred for 45 min . a sample of ps - b - p ( mtmsma ) was analyzed via small angle x - ray scattering ( saxs ). the data definitively show this block copolymer is phase separated at the nanoscale and that χn is of a sufficient value to induce order . the resulting bragg &# 39 ; s diffraction pattern displayed maxima at √ 3 , √ 4 , √ 7 , indicative of a hexagonally packed cylindrical morphology . the domain spacing was calculated to be 49 nm . see fig9 . thin films were spin coated on freshly oxidized wafers with a 1 wt % solution of ps - b - p ( mtmsma ) in toluene . the wafers were then annealed under a saturated atmosphere of acetone or thf overnight in a covered glass petri dish . the resulting films were analyzed via afm , and the images show both parallel ( fig1 ) and perpendicularly ( fig1 ) oriented cylinders depending on the solvent and film thickness . the size of the cylinders in these images is approximately 50 nm , which is consistent with the saxs data . 1 . ross , c . a . 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