content_image/913087.jpg content_image/913086.jpg content_image/913085.jpg
<img src='content_image/913087.jpg'>

[0344] As seen from the results of Table 3, the resist compositions comprising sulfonium compounds within the scope of the invention offer advantages including a high sensitivity, a good balance of LWR and MEF, and minimal defects. These data demonstrate that the inventive resist compositions are useful in the ArF immersion lithography. 

## [5] EUV Lithography Test 

## Examples 4-1 to 4-3 and Comparative Examples 3-1 to 3-3 

[0345] Each resist composition (R13 to R15 or R26 to R28) was spin coated on a silicon substrate having a 20-nm coating of silicon-containing spin-on hard mask SHB-A940 (silicon content 43 wt%, Shin-Etsu Chemical Co., Ltd.) and prebaked on a hot plate at 105° C. for 60 seconds to form a resist film of 60 nm thick. Using an EUV scanner NXE3300 (ASML, NA 0.33, a 0.9/0.6, quadrupole illumination), the resist film was exposed to EUV through a mask bearing a hole pattern having a pitch 46 nm+20% bias ( on-wafer size). The resist film was baked (PEB) on a hotplate at 100° C. for 60 seconds and developed in a 2.38 wt % TMAH aqueous solution for 30 seconds to form a hole pattern having a size of 23 nm. 

[0346] The resist pattern was observed under CD-SEM (CG-5000, Hitachi High-Technologies Corp.). The exposure dose that provides a hole pattern having a size of 23 nm is reported as sensitivity. The size of 50 holes was measured, from which a size variation (30) was computed and reported as CDU. 

[0347] The resist composition is shown in Table 4 together with the sensitivity and CDU of EUV lithography. 

<img src='content_image/913086.jpg'>

[0348] It is demonstrated in Table 4 that resist composi› tions comprising sulfonium compounds within the scope of the invention offer a high sensitivity and improved CDU. The inventive resist compositions are also useful in the EUV lithography. 

## [6] EB Writing Test 

[0349] Examples 5-1 to 5-2 and Comparative Examples 4-1 to 4-2 Using a coater/developer systemACT-M (Tokyo Electron Ltd.), each of the resist compositions R16, Rl 7, R29 and R30 was spin coated onto a mask blank of 152 mm squares having the outermost surface of silicon oxide (vapor primed with hexamethyldisilazane) and prebaked on a hot› plate at 110° C. for 600 seconds to form a resist film of 80 nm thick. The thickness of the resist film was measured by an optical film thickness measurement system Nanospec (Nanometrics Inc.). Measurement was made at 81 points in the plane of the blank substrate excluding a peripheral band extending 10 mm inward from the blank periphery, and an average film thickness and a film thickness range were computed therefrom. 

[0350] The coated mask blank was exposed to EB using an EB writer system EBM-5000Plus (NuFlare Technology Inc., accelerating voltage 50 kV), then baked (PEB) at 110° C. for 600 seconds, and developed in a 2.38 wt% TMAH aqueous solution, thereby yielding a negative resist pattern. 

[0351] The patterned mask blank was observed under a top-down scanning electron microscope (TD-SEM). The optimum exposure (Eop) was defined as the exposure dose (µC/cm 2 ) which provided a 1: 1 resolution of a 200-nm 1: 1 line-and-space pattern. The maximum resolution of the resist was defined as the minimum line width of a LIS pattern that could be resolved at the optimum exposure. The LER of a 200-nm LIS pattern was measured under SEM. The resist pattern was visually observed and judged whether or not the pattern profile was rectangular. 

[0352] Evaluation of Development Residue Defects 

[0353] A resist film was formed under the same conditions as above. The resist film was directly (i.e., imagewise exposure omitted) baked at 110° C. for 600 seconds and developed in a 2.38 wt% TMAH aqueous solution. Using a mask defect monitor M2351 (Lasertec Corp.), development residues were counted. The total count of defects after development was determined. The sample was rated good when the total count of defects is less than 300, or poor when the total count of defects is equal to or more than 300. 

[0354] The test results are shown in Table 5. 

<img src='content_image/913085.jpg'>

[0355] As seen from the data in Table 5, the resist com› positions containing sulfonium compounds within the scope of the invention as PAG exhibit advantages including high maximum resolution, improved LER, satisfactory pattern 

