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## <Preparation of Resist Composition> 

400 mg of any of the above polymers is dissolved in a mixed solvent of 4 ml of y-butyrolactone and 4 ml of cyclohexanone to prepare resist composition samples 1 to 10 40 of Examples 1 to 8 and Comparative Examples 1 and 2. The polymers used are described in Table 2. 

## <Preparation of Developer> 

A developer modified for each polymer is prepared by mixing pure water, methanol, isopropyl alcohol, acetonitrile, tetrahydrofuran and methyl ethyl ketone, so that 15% by mass of the polymers 1 to 19 is dissolved therein. A content of each component is in the range of O to 70% by mass. 

## <Evaluation of Electron Beam Sensitivity> 

The resist composition sample 1 is spin-coated on a silicon wafer modified with hexamethylenedisilazane in advance. This is prebaked on a hot plate at 110° C. for 1 minute to obtain a substrate on which a coating film having a thickness of 200 nm forms. To the coating film on the substrate, a line and space pattern of 2 µm is drawn by an electron beam of30 keVusing an electron beam lithography system (JSM-6500F, JEOL Ltd.). After irradiation with the electron beam, the substrate is developed with the developer for 1 minute and then rinsed with pure water to obtain the line and space pattern of 2 µm. The irradiation dose at this time is defined as Emax [µC/cm 2 ], and the sensitivity to the irradiation with the electron beam is evaluated. 

The sensitivity evaluation is also performed on Samples 2 to 10 in the same procedure as above. The results are described in Table 2. 

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According to Examples 1 to 3 in Table 2, it is found that when the polarity conversion of the onium salt is utilized, no significant difference in sensitivity is observed regardless of whether compound Al or compound A3 having different acid strength. On the other hand, when the compound A4 having a hexafluoroantimonate anion is used, since a density of the film is largely increased by including antimony, the sensitivity to the electron beam is improved. This is because the metal atom such as antimony has a greater absorption of the electron beam than organic atoms such as hydrogen, carbon, oxygen and fluorine. Therefore, the same effect can be expected for EUV. 

According to the comparison of Examples 1 to 2 and Comparative Examples 1 to 2, it is found that the sensitivity of Examples 1 to 2, having both unit A and unit B, is greatly 

TABLE 2 

