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was resolved at the optimum exposure dose. The edge rough› ness of a 100-nm line-and-space pattern was measured by SEM. 

For a particular resist composition, an optimum PEB tem› perature for EB writing, sensitivity, and resolution are reported in Table 15. 

<img src='content_image/901584.jpg'>

As seen from Table 15, the resist compositions within the scope of the invention exhibit a high sensitivity and high resolution as compared with the comparative resist composi› tions. The optimum PEB temperature for the inventive resist compositions is lower than that for the comparative resist compositions, indicating that the inventive resist composi› tions have a higher sensitivity. Examples 3 to 24 exhibit better resolution than Examples 1 and 2, indicating that copolymer› ization of indene or acenaphthylene units provides a higher contrast. 

Evaluation of ArF Excimer Laser Lithography 

Each of positive resist compositions (Examples 25 to 50 and Comparative Examples 7 to 12) was spin coated on a silicon wafer having an antireflective coating (ARC-29A, Nissan Chemical Industries, Ltd.) of78 nm thick and baked at 110° C. for 60 seconds, forming a resist film of 120 nm thick. The coated wafer was exposed by means of an ArF excimer laser stepper (Nikon Corp., NA 0.85), post-exposure baked 

## TABLE 15 

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(PEB) for 60 seconds, and puddle developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution for 30 seconds, forming a 1: 1 line-and-space pattern and a 1: 10 isolated line pattern. During the PEB, an optimum tempera› ture for each resist composition was employed. 

The patterned wafer was observed under a top-down scan- ning electron microscope (TDSEM). The optimum exposure (Eop) was defined as the exposure dose (mJ/cm 2 ) which provided a 1: 1 resolution at the top and bottom of a 80-nm 1: 1 line-and-space pattern. The maximum resolution of the resist was defined as the minimum line width (on-mask size, in increments of 5 nm) of a 1: 1 line-and-space pattern that was resolved and separated at the optimum exposure, with smaller values indicating better resolution. The 1: 10 isolated line pattern at the optimum exposure was also observed for deter› mining an actual on-wafer size of the isolated line pattern with an on-mask size of 140 nm, which was reported as mask fidelity ( on-wafer size, a larger size being better). The pattern was visually observed to see whether or not its profile was rectangular. 

Table 16 tabulates the test results (maximum resolution, mask fidelity and profile) of the inventive and comparative resist compositions. 

## TABLE 16 

