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As apparent from Table 4 above, in Comparative Examples 2-1 and 2-2 using Resin (Ab’-1) and Resin (Ab’-2) containing the repeating unit represented by formula ( 1) but not contain› ing the repeating unit represented by formula (A), the sensi› tivity and the resolution of an isolated line pattern were poor, the pattern profile was reverse tapered, the PEB temperature dependency was high, and the etching resistance was low. In Comparative Examples 2-3 and 2-4 using Resin (Ab’-3) and (Ab’-4) containing the repeating unit represented by formula (A) but not containing the repeating unit represented by for- mula (1 ), the PEB temperature dependency was high in par› ticular, the pattern profile was tapered, and the resolution of an isolated line pattern was poor. 

On the other hand, in all of Examples 2-1 to 2-30 using the resin (P) containing the repeating unit represented by formula (1) and the repeating unit represented by formula (A), the resolution of an isolated line pattern was excellent, the PEB temperature dependency was low, the pattern profile was rectangular, and the sensitivity and etching resistance were high. 

[Examples 3-1 to 3-30 and Comparative Examples 3-1 to 3-4; Extreme-ultraviolet Ray (EUV) Exposure, Organic Solvent Development, Evaluation of Isolated Line] 

(5) Preparation and Coating of Coating Solution of Actinic Ray-Sensitive or Radiation-Sensitive Resin Composition 

A coating solution composition having a solid content concentration of 1.5 mass % according to the formulation shown in Table 5 below was microfiltered through a mem› brane filter having a pore size of0.05 µm to obtain an actinic ray-sensitive or radiation-sensitive resin composition (resist composition) solution. 

This actinic ray-sensitive or radiation-sensitive resin com› position was coated on a 6-inch Si wafer previously subjected to a hexamethyldisilazane (HMDS) treatment, by using a spin coater, Mark 8, manufactured by Tokyo Electron Ltd. and dried on a hot plate at 100° C. for 60 seconds to obtain a resist film having a thickness of 50 nm. 

(6) EUV Exposure and Organic Solvent Development 

The resist film-coated wafer obtained in (5) above was patternwise exposed by using an EUV exposure apparatus (Micro Exposure Tool, manufactured by Exitech, NA: 0.3, X-dipole, outer sigma: 0.68, inner sigma: 0.36) through an exposure mask (line/space=5/1). After the irradiation, the resist film was heated on a hot plate at 100° C. for 90 seconds, then developed by puddling the organic developer shown in Table 5 below for 30 seconds, rinsed by using the rinsing solution shown in the Table below, spun at a rotation speed of 4,000 rpm for 30 seconds and baked at 95° C. for 60 seconds to obtain a resist pattern ofa 1: I line-and-space pattern having a line width of 50 nm. 

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(7) Evaluation of Resist Pattern 

Using a scanning electron microscope (S-9380II, manu› facture by Hitachi Ltd.), the obtained resist pattern was evalu› ated for sensitivity, pattern profile, resolution in isolated line pattern, PEB temperature dependency and etching resistance by the following methods. 

(7 -1) Sensitivity 

The irradiation energy below which the pattern of line/ space= 1: 1 with a line width of 50 nm cannot be resolved was taken as the sensitivity (Eop ). A smaller value indicates higher performance. 

(7-2) Evaluation of Pattern Profile 

The cross-sectional profile of the 1: 1 line-and-space pat› tern with a line width of 50 nm formed at the irradiation dose giving the above-described sensitivity was observed using a scanning electron microscope and evaluated on a scale of three grades of rectangular, tapered and reverse tapered. 

(7-3) Resolution in Isolated Line Pattern 

The limiting resolution (the minimum line width below which a line and a space cannot be separated and resolved) of an isolated line pattern (line/space= 1: 5) formed at Eop above was determined. This value was taken as "resolution (nm)". A smaller value indicates higher performance. 

(7-4) PEB Temperature Dependency 

The exposure dose for reproducing a line-and-space 1/1 mask pattern with a mask size of 50 nm when post-baking was performed at 100° C. for 90 seconds, was taken as an optimal exposure dose. After performing exposure at the optimal exposure dose, post-baking was performed at two tempera› tures of +2° C. and -2° C. with respect to the post-baking temperature (that is, 102° C. and 98° C.), and respective line-and-space patterns obtained were measured for the length to determine the line widths L$_{1 }$ and L$_{2}$ . The PEB temperature dependency was defined as the fluctuation ofline width per PEB temperature change of 1 ° C. and calculated according to the following formula. 0 

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A smaller value indicates less change in performance due to temperature change and is better. 

(7 -5) Etching Resistance 

A resist film having a thickness of 200 nm was formed on a wafer and then subjected to plasma etching under the con› dition of a temperature of 23 ° C. over 30 seconds by using a mixed gas of C$_{4}$F $_{6 }$ (20 mL/min) and 0 2 ( 40 mL/min). There› after, the residual film amount was determined, and the etch› ing rate was calculated. The etching resistance was evaluated based on the following criteria. 

(Evaluation Criteria) 

A: When the etching rate is less than 15 A/sec. 

B: When the etching rate is 15 A/sec or more. 

