Phenolic polymers and photoresists comprising same

Abstract

The present invention relates to new polymers that contain phenolic groups spaced from a polymer backbone and photoacid-labile group. Preferred polymers of the invention are useful as a component of chemically-amplified positive-acting resists.

Claims

1. A photoresist composition comprising a photoactive component and a resin, the resin comprises a structure of the following formula: ##STR00015## wherein each Z is the same or different bridge unit; X comprises one or more alkyl, oxygen or sulfur atoms; each R.sup.1 is the same or different non-hydrogen substituent; and m is an integer of from zero to 4; AL is a moiety that comprises a photoacid-labile group; Y is a moiety that is distinct from the spaced phenolic group or moiety that comprises AL, and Y is selected from the group consisting of phenyl; phenyl substituted with halogen, cyano, alkyl or alkoxy; an ester that does not undergo a photoacid-indueed cleavage reaction during exposing and developing of the photoresist layer; an alicyclic group; and a lactone; and a, b and c are mole percents of the respective polymer units based on total repeat units in the polymer and a, b and c are each greater than zero.

2. A photoresist composition of claim 1 wherein X consists essentially of one or more alkyl or oxygen atoms.

3. A photoresist composition of claim 1 wherein Y is selected from the group consisting of phenyl; phenyl substituted with halogen, cyano, alkyl or alkoxy; an ester that does not undergo a photoacid-induced cleavage reaction during exposing and developing of the photoresist layer.

4. A photoresist composition of claim 1 wherein the resin comprises a structure of the following formula ##STR00016## each R is the same or different and is hydrogen or optionally substituted alkyl; each Z is the same or different bridge unit; X comprises one or more alkyl, oxygen or sulfur atoms; each R.sup.1 is the same or different non-hydrogen substituent; m is an integer of from zero to 4; P is a moiety that provides a photoacid-labile ester; Y is a moiety that is distinct from the spaced phenolic group or moiety that comprises P, and Y is selected from the group consisting of phenyl; phenyl substituted with halogen, cyano, alkyl or alkoxy; an ester that does not undergo a photoacid-induced cleavage reaction during exposing and developing of the photoresist layer; an alicyclic group; and a lactone; and a, b and c are mole percents of the respective polymer units based on total repeat units in the polymer and are each greater than zero.

5. A photoresist composition of claim 4 wherein X consists essentially of one or more alkyl or oxygen atoms.

6. A photoresist composition of claim 4 wherein the resin comprises polymerized units of hydroxyphenylmethacrylate; methyl methacrylate; and tert-butyl acrylate.

7. A photoresist composition of claim 4 wherein the resin comprises polymerized units of hydroxyphenylmethacrylate; styrene; and tert-butyl acrylate.

8. A photoresist composition of claim 4 wherein Y is selected from the group consisting of phenyl; phenyl substituted with halogen, cyano, alkyl or alkoxy; an ester that does not undergo a photoacid-induced cleavage reaction during exposing and developing of the photoresist layer.

Description

EXAMPLE 1

Preparation of Methacrylic Acid Anhydride/methacrylic Acid Mixture

(1) Acetic anhydride was added by dropwise addition to an excess of methacrylic acid (4:1) while simultaneously distilling acetic anhydride from the mixture. The reaction was carried out at 95 Oc and 300 mmHg, catalyzed by 1 mole % amberlyst-15 (A-15), and inhibited with 3000 ppm PTZ and 1000 MEHQ pppm, 8% O.sub.2. At the end of the reaction, excess methacrylic acid was recovered by distillation under reduced pressure and the catalyst was recovered by filtration.

EXAMPLE 2

Monomer Synthesis; Preparation of Hydroxyphenyl Methacrylate

(2) To a mechanically stirred solution of 2 moles of hydroxyquinone dissolved in 3 moles of methacrylic acid at 120 C. and atmospheric pressure was added dropwise (30 min) 1 mole of methylacrylic acid anhydride and the mixture was maintained at 120 C. with stirring for additional 4 hrs (NMR analysis). Throughout the course of the reaction 8% oxygen was admitted to the system. At the end of the reaction, the methacrylic acid was recovered by distillation under reduced pressure (110 C. and 200 mmHHg), and the unreacted excess hydroquinone was precipitated out by the addition of toluene (1 liter) to the reaction mixture. A low level (1-2%) of the monomer 2-methyl-5-methylenehexanedioic acid was formede. This monomer was separated from the mixture by a washing step with distilled water. After phase separation, the desired 4-hydroxyphenyl methacrylate was obtained at 97% yield by the distillation of toluene under reduced pressure. {mp. (Uncorrected) 120 C.; Anal. Calcd. For C.sub.10H.sub.10O.sub.3: C, 67.41: H, 5.66; O, 26.94. Found: C, 67.37; H, 5.62}.

EXAMPLE 3

Monomer Synthesis; Preparation of Hydroxyphenyl Methacrylate through Mono-Ester Intermediate

(3) A large excess of hydroquinone is reacted with acetic acid anhydride in the presence of acetic acid to provide the mono-acetate phenolic compound 1,4-C.sub.6H.sub.4(OH)(OOCCH.sub.3). Excess starting materials are recovered, and the intermediate compound 1,4-C.sub.6H.sub.4(OH)(OOCCH.sub.3) is reacted with methacylic acid in the presence of acetic acid to provide hydroxyphenyl methacrylate.

EXAMPLE 4

Polymer Synthesis

(4) ##STR00013##

(5) To a 500 mL, 3 neck round bottom flask equipped with a condenser, thermometer, magnetic stirrer and external oil heating bath, was added the following: 4-hydroxyphenyl methacrylate (HPhMA) (16.56 g, 0.093 mol), methyl methacrylate (MMA) (15.54 g, 0.155 mol), and tert-butyl acrylate (TBA) (7.95 g, 0.062 mol). Methanol (270 mL) was added and the resulting solution heated to reflux (67 C.). Once at reflux, a solution of initiator 2,2-azobis-2,4-dimethylpentanenitrile (1.54 g, 0.006 mol) in methanol (17.5 mL). The solution was held for 2 hours at reflux, after which another charge of initiator was added to the flask (0.77 g, 0.003 mol) in methanol (9 mL). The solution was held at reflux for 16 hours. After cooling, the polymer solution in methanol was washed with heptanes (3300 mL). The solution was concentrated on a rotary evaporator to remove residual heptanes and then precipitated into DI water (2 liters). The wet cake was air dried for 24 hours and then dried at 60 C. under vacuum for 18 hours. The yield was 90%.

EXAMPLE 5-6

Additional Polymer Synthesis

(6) Additional HPhMA:MMA:TBA terpolymers were prepared by the procedures of Example 4 above, but varying amount of monomers employed. In Table 1 below which follows Example 9, the ratio of each of the monomer units (as determined by .sup.13C NMR analysis of the formed polymer), weight average molecular weight (Mw) and polydispersity (PD) are provided for the HPhMA:MMA:TBA terpolymers formed in Examples 5 and 6.

EXAMPLES 7

Additional Polymer Synthesis

(7) ##STR00014##

(8) To a 500 mL, 3 neck round bottom flask equipped with a condenser, thermometer, magnetic stirrer and external oil heating bath, was added the following: 4-hydroxyphenyl methacrylate (HPhMA) (27.94 g, 0.157 mol), styrene (STY) (10.89 g, 0.105 mol), and tert-butyl acrylate (TBA) (11.17 g, 0.087 mol). Methanol (340 mL) was added and the resulting solution heated to reflux (67 C.). Once at reflux, a solution of initiator 2,2-azobis-2,4-dimethylpentanenitrile (1.73 g, 0.007 mol) in methanol (20 mL). The solution was held for 2 hours at reflux, after which another charge of initiator was added to the flask (0.87 g, 0.004 mol) in methanol (10 mL). The solution was held at reflux for 16 hours. After cooling, the polymer solution in methanol was washed with heptanes (3300 mL). The solution was concentrated on a rotary evaporator to remove residual heptanes an then precipitated into DI water (2.5 liters). The wet cake was air dried for 24 hours and then dried at 60 C. under vacuum for 18 hours. The yield was 90%.

EXAMPLE 8-9

Additional Polymer Synthesis

(9) Additional HPhMA:STY:TBA terpolymers were prepared by the procedures of Example 7 above, but varying amount of monomers employed. In Table 1 below, the ratio of each of the monomer units (as determined by .sup.13C NMR analysis of the formed polymer), weight average molecular weight (Mw) and polydispersity (PD) are provided for the HPhMA:STY:TBA terpolymers formed in Examples 8 and 9.

(10) TABLE-US-00001 TABLE 1 Polymer Characterization Composition Example Polymer Description (13C-NMR) Mw PD 4 HPhMA/MMA/TBA 32/51/17 15400 2.7 5 HPhMA/MMA/TBA 42/40/18 18300 2.9 6 HPhMA/MMA/TBA 55/27/18 20200 3.1 7 HPhMA/STY/TBA 44/26/30 15300 2.6 8 HPhMA/STY/TBA 50/34/16 13100 2.3 9 HPhMA/STY/TBA 54/33/13 13700 2.3

EXAMPLE 10

Dissolution Rate Studies

(11) Polymers of the above examples were coated to approximately equal dried (soft bake) coating layers over a wafer substrate. Dissolution rates were measured of those polymer coating layers with a 0.26 N alkaline aqueous developer. Dissolution rates are set forth in Table 2 below. Measured Tg values also are set forth in Table 2 below.

(12) TABLE-US-00002 TABLE 2 Polymer Characterization OD DR (A/sec) in Tg at 248 nm 0.26N Example Polymer Description ( C.) (1/) TMAH 4 HPhMA/MMA/TBA 116 0.53 1.2 5 HPhMA/MMA/TBA 125 0.67 16.6 6 HPhMA/MMA/TBA 130 0.78 115 7 HPhMA/STY/TBA 106 0.63 0.36 8 HPhMA/STY/TBA 117 0.73 2.0 9 HPhMA/STY/TBA 122 0.79 7.8

EXAMPLE 11

Optical Density Evaluations

(13) Polymers of the above examples were coated to approximately equal dried (soft bake) one micron thick coating layers over a wafer substrate. Polymer layer thickness was measured by ellipsometry. The absorbance of the films on quartz was determined by UV spectrophotometry. The absorbance was measured against a blank quartz wafer. Optical density (OD) was calculated at 248 nm using thickness and absorbance measurements. Measured OD values are set forth in Table 3 below.

(14) TABLE-US-00003 TABLE 3 Polymer Characterization OD at 248 nm Example Polymer Description (1/) 4 HPhMA/MMA/TBA 0.53 5 HPhMA/MMA/TBA 0.67 6 HPhMA/MMA/TBA 0.78 7 HPhMA/STY/TBA 0.63 8 HPhMA/STY/TBA 0.73 9 HPhMA/STY/TBA 0.79

EXAMPLE 12

Photoresist Preparation and Lithographic Processing

(15) A photoresist of the invention is prepared by admixing the following components in the specified amounts:

(16) TABLE-US-00004 Resist component Amount Resin to provide 11.4 wt. % total solids liquid formulation Photoacid generator 3.5 wt. % of resin component Basic additive 0.1 wt. % of polymer Surfactant 0.05 wt. % of total solids.

(17) In that resist, the polymer is a HPhMA:MMA:TBA terpolymer prepared as described in Example 4. The photoacid generator of the resist is di-tertbutylphenyliodonium camphorsulfonate. The basic additive is the lactate salt of tetremethylammoniium hydroxide. The surfactant is the commercially available material sold under the name R08. The solvent is ethyl lactate.

(18) That photoresist composition is spin coated onto 200 min silicon wafers having a coating of an organic antireflective composition. The applied photoresist later is soft-baked at 90 C. for 60 seconds and exposed through a photomask to 248 nm radiation. The exposed resist coating layer is then baked at 100 C. for 90 seconds and developed using an alkaline aqueous developer.

EXAMPLE 13

Additional Photoresist Preparation and Lithographic Processing

(19) A photoresist of the invention is prepared by admixing the following components in the specified amounts:

(20) TABLE-US-00005 Resist component Amount Resin to provide 11.4 wt. % total solids liquid formulation Photoacid generator 3.53 wt. % of resin component Basic additive 0.12 wt. % of polymer Surfactant 0.05 wt. % of total solids.

(21) In that resist, the polymer was a HPhMA:STY:TBA terpolymer prepared as described in Example 7. The photoacid generator of the resist is di-tertbutylphenyliodonium camphorsulfonate. The basic additive is the lactate salt of tetremethylammoniium hydroxide. The surfactant is the commercially available material sold under the name R08. The solvent is ethyl lactate.

(22) That photoresist composition is spin coated onto 200 mm silicon wafers having a coating of an organic antireflective composition. The applied photoresist later is soft-baked at 90 C. for 60 seconds and exposed through a photomask to 248 nm radiation. The exposed resist coating layer is then baked at 100 C. for 90 seconds and developed using an alkaline aqueous developer.