194  US 9,703,193 B2  193  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  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:  MEF~(pattem space width)/(mask line width)-b  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.  TABLE 7  Example  Comparative  Example  PEB  Resist  temp.  Eop  DOF Defect  composition  (" c.)  (mJ/cm 2 )  Profile  MEF  (nm) density  3-1  R-1  85  35  Good  2.45  105 Good  3-2  R-2  85  30  Good  2.88  110 Good  3-3  R-3  85  34  Good  2.90  90 Good  3-4  R-4  85  28  Good  2.67  105 Good  3-5  R-5  85  28  Good  2.70  100 Good  3-6  R-6  90  36  Good  2.66  95 Good  3-7  R-7  90  28  Good  3.01  105 Good  3-8  R-8  90  27  Good  3.15  100 Good  3-9  R-9  85  33  Good  3.15  100 Good  3-10  R-10  90  30  Good  3.10  105 Good  3-11  R-11  85  30  Good  2.90  125 Good  3-12  R-12  90  36  Good  3.11  100 Good  3-13  R-13  85  31  Good  3.14  105 Good  3-14  R-14  85  38  Good  2.99  100 Good  3-1  R-15  85  45  NG  3.89  85 NG  3-2  R-16  85  49  NG  3.75  90 NG  3-3  R-17  85  24  NG  3.90  80 NG  3-4  R-18  85  41  NG  4.12  85 NG  3-5  R-19  85  27  NG  3.85  90 NG  3-6  R-20  85  48  NG  3.57  80 NG  3-7  R-21  85  48  NG  4.44  70 NG  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  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. 