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## 5) ArF Lithography Patterning Test #2: Evaluation of LIS and Trench Patterns 

## Examples 3-1 to 3-14 and Comparative Examples 3-1 to 3-10 

On a substrate, a spin-on carbon film ODL-50 (Shin-Etsu Chemical Co., Ltd.) having a carbon content of 80 wt% was deposited to a thickness of 200 nm and a silicon-containing spin-on hard mask SHB-A940 (Shin-Etsu Chemical Co., Ltd.) having a silicon content of 43 wt % was deposited thereon to a thickness of 35 nm. On this substrate for trilayer process, each of the resist compositions (Inventive R-1 to R-14 or Comparative R-15 to R-24) was spin coated and baked on a hot plate at 100° C. for 60 seconds to form a resist film of 100 nm thick. Using an ArF excimer laser immersion lithography scanner NSR-610C (Nikon Corp., NA 1.30, a 0.98/0.78, 4/5 annular illumination), pattern exposure was performed through Mask A or B described below. 

Mask A is a 6% halftone phase shift mask bearing a line pattern with a pitch of 100 nm and a line width of 50 nm (on-wafer size). After exposure through Mask A, the wafer was baked (PEB) for 60 seconds and developed. Specifi› cally, butyl acetate was injected from a development nozzle 25 for 3 seconds while the wafer was spun at 30 rpm, which was followed by stationary puddle development for 27 seconds. As a result, the unexposed regions which had been masked with Mask A were dissolved in the developer, that is, image reversal took place to form a line-and-space (LIS) pattern 30 with a space width of 50 nm and a pitch of 100 nm. 

Mask B is a 6% halftone phase shift mask bearing a line pattern with a pitch of 200 nm and a line width of 45 nm (on-wafer size). After exposure through Mask B, the wafer was baked (PEB) for 60 seconds and developed. Specifi- cally, butyl acetate was injected from a development nozzle for 3 seconds while the wafer was spun at 30 rpm, which was followed by stationary puddle development for 27 seconds. As a result, the unexposed regions which had been masked with Mask B were dissolved in the developer, that is, image reversal took place to form an isolated space pattern (re› ferred to as "trench pattern", hereinafter) with a space width of 45 nm and a pitch of 200 nm. 

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Evaluation of Sensitivity 

As an index of sensitivity, the optimum dose (Eop, mJ/cm 2 ) which provided an LIS pattern with a space width of 50 nm and a pitch of 100 nm on exposure through Mask A was determined. 

Evaluation of Pattern Profile 

The profile of a pattern printed at the optimum dose was examined and judged good or not according to the following criterion. 

Good: rectangular pattern profile with perpendicular side› wall 

NG: tapered pattern profile with largely slanted sidewall, or rounded top profile due to top loss 

Evaluation of MEF 

An LIS pattern was formed by exposure in the optimum dose ( determined in the sensitivity evaluation) through Mask A with the pitch fixed and the line width varied. MEF was calculated from variations of the mask line width and the pattern space width according to the following equation: 

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wherein b is a constant. A value closer to unity (1) indicates better performance. 

Evaluation of DOF Margin 

The exposure dose and DOF which ensured to form a trench pattern with a space width of 35 nm on exposure through Mask B were defined as the optimum exposure dose and the optimum DOF, respectively. The depth over which focus was changed that could form a resist pattern with a space width of35 nm–10% (i.e., 31.5 nm to 38.5 nm) was determined and reported as DOF. A larger value indicates a smaller change of pattern size with a change of DOF and hence, better DOF margin. 

Evaluation of Defect Density 

Further, defects in the pattern as developed were inspected by a flaw detector KLA2800 (KLA-Tencor). A defect density (count/cm 2 ) was computed by dividing the total number of detected defects by a detection area. The pattern formed was an iterated 50-nm 1:1 LIS pattern. The defect inspection conditions included light source UV, inspected pixel size 0.28 µm, and cell-to-cell mode. In this test, the sample was rated good for a defect density of less than 0.05 defect/cm 2 and NG for a density of equal to or more than 0.05 defect/cm 2 . 

## The results are shown in Table 7. 

