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[0222] As seen from Table 5, the onium compounds used in resist compositions of Examples are effective for forming a film with a minimal variation of thickness, indicating that the film functions as a resist film for micropatterning. 

## [5] Resist Composition Evaluation #3: Developer Dissolution Test 

## Examples 4-1 to 4-6 and Comparative Example 4-1 

[0223] Using a coater/developer system Clean Track ACT™ 8 (Tokyo Electron Ltd.), each of the resist compo› sitions (R-06 to R-11, R-23) was spin coated onto a HMDS› primed silicon substrate of 8 inches at 1,500 rpm, and pre-baked on a hotplate at 100° C. for 60 seconds to form a resist film of 50 nm thick. Thereafter, the resist film was puddle developed in 2.38 wt % TMAH aqueous solution for 30 seconds, rinsed with deionized water, and spin dried. Using an ellipsometer Atlas XP+ (Nanometrics Inc.), the thickness of the resist film on the silicon substrate was measured, with the results shown in Table 6. 

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[0224] As seen from Table 6, the unexposed regions of the resist compositions of Examples have a low dissolution rate in the alkaline developer. It is demonstrated that the resist compositions of Examples behave as positive tone resist relative to the alkaline developer. 

## [6] Resist Composition Evaluation #4: Evaluation of Contrast Curve 

## Examples 5-1 to 5-13 and Comparative Example 5-1 

[0225] An antireflective coating solution DUV-42 (Nissan Chemical Industries, Ltd.) was coated onto a silicon sub› strate and baked at 200° C. for 60 seconds to form an antireflective coating of 61 nm thick thereon. Each of the resist compositions (R-1 to R-19, R-24) was spin coated on the ARC, and baked on a hotplate at 100° C. for 60 seconds to form a resist film of 50 nm thick. By means of KrF excimer laser scanner NSR-S206D (Nikon Corp., NA=0.86, conventional illumination), the resist film was subjected to open-frame exposure in a dose varying from 1 mJ/cm 2 to 200 mJ/cm$^{2 }$at a pitch of 1 mJ/cm 2 . The resist film was baked 

(PEB) at the temperature shown in Table 7 for 60 seconds, puddle developed in a 2.38 wt % TMAH aqueous solution for 30 seconds, rinsed with deionized water, and spin dried. Using a spectroscopic film thickness measurement system VM-2200 (Screen Semiconductor Solutions Co., Ltd.), the resist film after development was measured for thickness in the regions subject to different doses. E$_{0 }$ is the dose provid› ing a film thickness of 0. The slope of exposed regions where the film thickness varied from 10 nm to 40 nm was deter› mined and reported as contrast. The results are shown in Table 7. 

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[0226] As seen from Table 7, the resist compos1t10ns within the scope of the invention have a practically accept› able sensitivity and contrast. 

## [7] Resist Composition Evaluation #5: EB Writing Test 

## Example 6-1, Comparative Example 6-1 and Reference Examples 2-1 to 2-2 

[0227] An antireflective coating solution DUV-42 (Nissan Chemical Industries, Ltd.) was coated onto a silicon sub› strate and baked at 200° C. for 60 seconds to form an antireflective coating of 61 nm thick thereon. Each of the resist compositions (R-02, R-26, R-27, R-28) was spin coated on the ARC, and baked on a hotplate at 100° C. for 60 seconds to form a resist film of 50 nm thick. Using an EB lithography system ELS-F125 (Elionix Co., Ltd., accelerat› ing voltage 125 kV), the resist film was exposed to EB so as to write a line-and-space pattern with a size 100 nm and a pitch 200 nm ( on-wafer size) while varying the dose from 50 µC/cm $^{2 }$at a step of 5 µC/cm 2 . After exposure, the resist film was baked (PEB) at the temperature shown in Table 8 for 60 seconds. The resist film was then puddle developed in a 2.38 wt % TMAH aqueous solution for 30 seconds, rinsed with deionized water and spin dried, yielding a positive pattern. The pattern after development was observed under an elec› tron microscope CD-SEM S-9380 (Hitachi High-Technolo› gies Corp.). Sensitivity and LWR were evaluated by the following methods. The results are shown in Table 8. 

## Evaluation of Sensitivity 

[0228] As an index of sensitivity, the optimum dose Eop (µC/cm 2 ) which provided a LIS pattern with a line width of 

