Lactone photoacid generators and resins and photoresists comprising same

Abstract

New lactone-containing photoacid generator compounds (“PAGs”) and photoresist compositions that comprise each PAG compounds are provided. These photoresist compositions are useful in the manufacture of electronic device.

Claims

1. A photoacid generator having a formula chosen from ##STR00027## wherein M.sup.+is a cation.

2. A photoresist composition comprising a polymer and a photoacid generator of claim 1.

3. A method for forming a photoresist relief image on a substrate comprising: (a) applying a coating layer of a photoresist composition of claim 2 on a substrate; and (b) exposing the photoresist coating layer to patterned activating radiation and developing the exposed photoresist layer to provide a relief image.

4. A photoacid generator of claim 1 having a formula chosen from ##STR00028## wherein M.sup.+is a cation.

5. A photoresist composition comprising a polymer and a photoacid generator of claim 4.

6. A method for forming a photoresist relief image on a substrate comprising: (a) applying a coating layer of a photoresist composition of claim 5 on a substrate; and (b) exposing the photoresist coating layer to patterned activating radiation and developing the exposed photoresist layer to provide a relief image.

7. A photoacid generator of claim 1 having a formula chosen from ##STR00029## wherein M.sup.+is a cation.

8. A photoresist composition comprising a polymer and a photoacid generator of claim 7.

9. A method for forming a photoresist relief image on a substrate comprising: (a) applying a coating layer of a photoresist composition of claim 8 on a substrate; and (b) exposing the photoresist coating layer to patterned activating radiation and developing the exposed photoresist layer to provide a relief image.

Description

EXAMPLE 1

Photoresist Preparation and Lithographic Processing

(1) A photoresist of the invention is prepared by mixing the following components with amounts expressed as weight percent based on total weight of the resist compositions:

(2) TABLE-US-00001 Resist components Amount (wt. %) Resin binder 15 Photoacid generator 3 Ethyl lactate 81

(3) The resin binder is a terpolymer of 2-methyl-2-adamantyl methacrylate/beta-hydroxy-gamma-butyrolactone methacrylate/cyano-norbornyl methacrylate. The photoacid generator is the compound shown in Scheme 1 above. The resin and PAG components are admixed in ethyl lactate solvent.

(4) The formulated resist composition is spin coated onto an antireflective coating layer disposed on a 150 mm (six inch) silicon wafers and softbaked via a vacuum hotplate at 130° C. for 60 seconds. The resist coating layer is exposed through a photomask at 193 nm, and then the exposed coating layers are post-exposure baked at 130° C. for 90 seconds. The coated wafers are then treated with 0.26N aqueous tetramethylammonium hydroxide solution to develop the imaged resist layer.

EXAMPLE 2

Synthesis of Photoacid Generator PAG-Al

(5) Photoacid generator PAG-Al was prepared by a five-step synthesis as outlined in Scheme 2 and the following paragraphs. The detailed synthetic process is presented below. Starting material 2-anti-hydroxy-4-oxa-5-homoadamatan-5-one (1) was prepared following the procedure published by Helmut Duddeck and coworkers in J. Org. Chem. 1981, 46, 5332-5336.

(6) ##STR00015## ##STR00016##

(7) To a solution of 5-bromo-4,4,5,5-tetrafluoropentanoic acid (2, 10 g, 39.52 mmol) in 100 mL of methylene chloride was added few drops of N,N-dimethyl formamid followed by oxalyl chloride (3, 5 g, 39.50 mmol) and the reaction mixture was stirred at room temperature for 2 hours. The product 5-bromo-4,4,5,5-tetrafluoropentanoyl chloride (4) was not isolated. To the above reaction mixture was added 2-anti-hydroxy-4-oxa-5-homoadamatan-5-one (1, 7.2 g, 39.51 mmol) followed by one equivalent of pyridine. The reaction mixture was stirred at room temperature for 16 hours. The content of the reaction mixture was transferred to a separation funnel and the methylene chloride solution was washed with 100 mL of 1N aqueous HCl, and then washed with water (2×100 mL). The organic phase was separated, dried over MgSO.sub.4, filtered and the solvent was removed under reduce pressure to produce the 14 g of the crude product 5 which was used in the next step without further purification.

(8) Compound 6 was prepared using the following procedure. To a round bottom flask equipped with a thermometer, overhead stirrer and condenser with N.sub.2 gas inlet, 14 g (33.55 mmol) of compound 5 was dissolved in 75 mL of acetonitrile and poured into an solution of sodium dithionite (12.85 g) and sodium hydrogen carbonate (8.40 g) in 100 mL of water. The reaction mixture was heated to 70° C. for about 18 hours and then cooled to room temperature. The aqueous layer was then removed and the acetonitrile solution (upper layer) that contained product 6 was used in the next step assuming 100% conversion. To the acetonitrile solution of the sulfinate derivative 6 was added 50 mL of water followed by 1.5 equivalent of an aqueous solution of hydrogen peroxide and the reaction was stirred at room temperature for 48 hours. Then sodium chloride (50 g) and sodium sulfite (10 g) were added. The mixture was allowed to separate into two layers. The upper acetonitrile layer was separated, dried over MgSO.sub.4, filtered and the solvent was removed under reduced pressure to produce the product 7 as white waxy solid. The overall isolated yield for the conversion of 5 to 7 was 44%.

(9) The synthesis of the photoacid generator PAG-Al (8) was achieved as follows: To a biphase system composed of 50 mL methylene chloride and 50 mL water was added 5 g (11.33 mmol) 7 and 3.9 g (11.36 mmol) of triphenyl sulfonium bromide (TPSBr) and the reaction mixture was stirred at room temperature for 18 hours. The organic phase was separated and washed with deionized water (5×50 mL). The separated organic phase was concentrated and poured into methyl t-butyl ether to produce the target photoacid generator PAG-Al (8). A second precipitation in methyl t-butyl ether produce pure product in 50% isolated yield. Samples of the PAG were assayed for purity using the HPLC MS. The cation purity as detected by UV at 230 nm is 99.8% and the purity detected by positive ion mass spectrometry is 99.4%. The anion purity as measured by negative ion liquid chromatography mass spectrometry (LCMS) was 100%.

EXAMPLE 3

(10) Photoacid generator PAG-A2 was prepared by a five-step synthesis as outlined in Scheme 3 and the following paragraphs. The detailed synthetic process is presented below.

(11) ##STR00017##
To a mixture 2-anti-Hydroxy-4-oxa-5-homoadamatan-5-one (1, 20 g, 0.1 mol) and 2-bromo-2,2-difluoroacetyl chloride (8, 23.34 g, 0.12 mol) in 150 mL of acetonitrile was added pyridine (9.55 g, 0.12 mol) and the reaction mixture was stirred at room temperature for 16 hours. The solvent was completely removed and the remaining residue was dissolved in 150 mL methylene chloride. The methylene chloride solution was transferred to a separation funnel and washed with 100 mL of 1N aqueous HCl, and then washed with water (2×100 mL). The organic phase was separated, dried over MgSO.sub.4, filtered and the solvent was removed under reduce pressure to produce the 36.7 g of the crude product 9 which was used in the next step without further purifications. In the next step compound 10 was prepared using the following procedure. To a round bottom flask equipped with a thermometer, overhead stirrer and condenser w/N.sub.2 gas inlet, 36.7 g (0.1 mol) of 9) was dissolved in 150 mL of acetonitrile and poured into a solution of sodium dithionite (37.6 g, 0.215 mol) and sodium hydrogen carbonate (18.0 g, 0.215 mol) in 150 mL of water. The reaction mixture was stirred at room temperature for 16 hours. .sup.1H-NMR of a sample from the reaction mixture indicated the presence of the expected product 10. Sodium chloride (100 g) was added to the reaction mixture and the aqueous layer was then removed and the acetonitrile solution (upper layer) that contained product 10 was used in the next step assuming 100% conversion. To the acetonitrile solution of the sulfinate derivative 10 was added 50 mL of water followed by 22 g of 30% aqueous solution of hydrogen peroxide and the reaction was stirred at room temperature for 48 hours. Then sodium chloride (50 g) and sodium sulfite (10 g) were added. The mixture was allowed to separate into two layers. The upper acetonitrile layer was separated, dried over MgSO.sub.4, filtered and the solvent was removed under reduced pressure to produce the product 11 as white waxy solid.

(12) The synthesis of the photoacid generator PAG-A2 (12) was achieved as follows: To a biphase system composed of 75 mL methylene chloride and 75 mL water was added 25 g (69.0 mmol) of 11 and 23.6 g (68.7 mmol) of triphenyl sulfonium bromide (TPSBr) and the reaction mixture was stirred at room temperature for 18 hours. The organic phase was separated and washed with deionized water (5×50 mL). The separated organic phase was concentrated and poured into methyl t-butyl ether to produce the target photoacid generator PAG-A2 (12). A second precipitation from acetone solution with methyl t-butyl ether produced 28 g of pure product (67.5%) yield. .sup.1H NMR (acetone-d6) δ: 7.90 (m, 15H), 5.06 (1H, m), 4.32 (1H, m), 2.89 (m, 1H), 2.4-1.5 (10H, complex); .sup.19F NMR (acetone-d6): .sup.19F NMR (acetone-d6) δ: −111.1 (CF.sub.2SO.sub.3).

EXAMPLE 4

Acid Diffusion Measurement

(13) Acid diffusion measurements were taken using a bilayer system. In this process flow, an organic antireflective coating layer was disposed on a silicon substrate. An acid detection layer, composed of a conventional 193 nm photoresist, was disposed on the antireflective coating layer. An acid source layer, which is composed of an acid inert polymer and the photoacid generator in study, was then disposed on the acid detection layer. Upon exposure using a 193 nm wavelength source, a photoacid is generated in the acid source layer. Subsequent heating (post bake exposure or PEB) leads to acid diffusion from the acid source layer to the acid detection layer0, where deprotection and solubility switching events occur. Subsequent development with aqueous base leads to film loss on the exposed area. The diffusivity of the PAG, D, is defined by Fick's law of diffusion: D=(ΔL/2*erfc E.sub.th/E)2/t.sub.PEB, where ΔL is the difference in film thickness between the exposed and unexposed area (also known as the film thickness loss), t.sub.PEB is the PEB time, erfc is the error function complement, E.sub.th is the exposure dose at which film thickness loss was observed for the first time, and E is the exposure dose. Once the diffusivity has been determined, the diffusion length, DL, can then be calculated with the following equation: DL=2*(D*t.sub.PEB).sup.½.

(14) The specific bilayer composition, preparation and process conditions are as follows: the acid detection layer was composed of an acid cleavable polymer A1 (shown below) (5.981% of solution) and tert-butyl 4-hydroxypiperidine-1-carboxylate as a quencher (0.019% of solution) in a 50/50 mix of propylene glycol methyl ether acetate (PGMEA) and methyl 2-hydroxyisobutyrate. The acid source was composed of t-butylacrylate/methylmethacrylate 30/70 copolymer (0.891% of solution) and the PAG (153.40 umol/g of solution) in a 80/20 mixture of 2-methyl-1-butanol and decane. The above solutions were filtered using a PTFE 0.2 μm syringe filter and spin coated onto a silicon wafer coated with a layer of AR™77-840A antireflectant (available from Dow Electronic Materials) using a TEL ATC 8 coater. The acid detection layer was coated first at 1200 Å and prebaked at 110° C. for 60 seconds. After the acid detection layer completed baking, the acid source layer was coated at 300 Å and baked at 90° C. for 60 seconds forming a bilayer system. This stack was then exposed at 193 nm using an ASML 1100 Stepper. The wafer was submitted to a post exposure bake (PEB) of 110° C. for 60 seconds or 120° C. for 60 seconds. During this step, the acid released during exposure in the acid source diffuses into the acid detection layer. Once the PEB is completed, the wafer is developed using 0.26 N aqueous trimethylammonium hydroxide (TMAH). The difference between the film thickness in the unexposed region and the film thickness in the exposed region gives us the total film loss (ΔL). The results are reported in Table 1, where DL=the PAG diffusion length reported in nm.

(15) TABLE-US-00002 TABLE 1 polymer A1 DL (nm) at DL (nm) at Sample PAG Anion structure PEB = 110° C. PEB = 120° C. Comparative 1 Triphenylsulfonium perfluotobutane- sulfonate 67.0  155.1  Inventive 1 PAG-A1 0 16.0  67.0 Inventive 2 PAG-A2  5.38  15.92

(16) As can be seen from Table 1, the acid diffusion measurements showed remarkably shorter acid diffusion length for inventive samples PAG-Al and PAG-A2 compared with the comparative PAG. These results demonstrate the utility of PAGs from the present invention on the manufacturing of highly resolving photoresists with excellent patterning characteristics.

EXAMPLE 5

Lithographic Evaluation

(17) Photoresist preparation: The photoresists were formulated using the components and proportions shown in Table 2. The commercial polymer A2 was used in all examples. Polymer A2 is a pentapolymer that incorporate monomers M1, M2, M3, M4 and M5. The molar ratio of the monomer is M1/M2/M3/M4/M5 is 2/2/3/2/1. The Mw of the polymer was 8000. Note that the PAG (see table), base (t-butyloxycarbonyl-4-hydroxypyridine, TBOC-4HP), and surface leveling agent (surfactant) PF 656, available from Omnova, are each provided below as weight percent based on 100% solids content, with the balance of the solids being the polymer. The solvents used in these formulations are propylene glycol methyl ether acetate (S1) and methyl 2-hydroxyisobutyrate (S2). The final % solids in both examples were 4 wt %. The weight ratio of solvent S1:S2 in the final formulation was 1:1. Photoresist formulation compositions for comparative sample 2 and inventive sample 2 are shown in Table 2 below:

(18) TABLE-US-00003 TABLE 2 M1 M2 M3 M4 M5 PAG Base SLA Sample PAG (wt %) (wt %) (wt %) Comparative 2 Triphenylsulfonium perfluotobutane- sulfonate  9.56 1.03 0.1 Inventive 4 PAG-A1 13.18 1.17 0.1 Inventive 5 PAG-A2 13.18 1.17 0.1

(19) Lithographic evaluation: The above photoresists were lithographically processed as follows. The photoresist was spin coated onto a 200 mm silicon wafer having an organic antireflective coating (AR™77, Dow Electronic Materials) and baked at 110° C. for 60 seconds, to form a resist film 100 nm in thickness. The photoresist was exposed with ArF excimer laser (193 nm) through a mask pattern targeting a line and space pattern (L/S pattern) having a line width of 90 nm and a pitch of 180 nm, using an ArF exposure apparatus ASML-1100 (manufactured by ASML), NA (numerical aperture)=0.75 under annular illumination with outer/inner sigma of 0.89/0.64 with focus offset/step 0.10/0.05. Thereafter, post exposure bake (PEB) was conducted at 100° C. for 60 seconds followed by development with 0.26 N aqueous tetramethylammonium hydroxide (TMAH) solution and subsequent water wash. As a result, in each example, a L/S pattern having a line width of 90 nm and a pitch of 180 nm was formed. Mask Error Factor (MEF), Exposure Latitude (EL) were determined by processing the image captured by top-down scanning electron microscopy (SEM) using a Hitachi 9380 CD-SEM, operating at an accelerating voltage of 800 volts (V), probe current of 8.0 picoamperes (pA), using 200 Kx magnification. Exposure latitude (EL) was defined as a difference in exposure energy to print +/−10% of the target diameter normalized by the sizing energy. Mask Error Factor (MEF) was defined as the ratio of CD change on the resolved resist pattern with the relative dimension change on the mask pattern.

(20) The results form the lithographic evaluation of the above photoresist formulations are reported in Table 3. As can be seen, inventive example 4 and 5, which utilize the PAGs PAG-Al and PAG-A2, respectively, showed improved lithographic performance based on exposure latitude (EL), mask error factor (MEF) and line width roughness (LWR).

(21) TABLE-US-00004 TABLE 3 EL @ 10% of Sample Esize (mJ/cm.sup.2) MEF CD Target LWR 3σ (nm) Comparative 2 30.5 3.86 7.9 11.6 Inventive 4 53.3 3.06 9.9 11.2 Inventive 5 44.2 3.1 9.8 10.8