Feb.28,2019  72  US 2019/0064665 Al  TABLE 3-continued  TABLE 4  TABLE 5  [0355]  As seen from the data in Table 5, the resist com› positions containing sulfonium compounds within the scope  of the invention as PAG exhibit advantages including high  maximum resolution, improved LER, satisfactory pattern  [0354]  The test results are shown in Table 5.  [0353]  A resist film was formed under the same conditions  as above. The resist film was directly (i.e., imagewise  exposure omitted) baked at 110°  C. for 600 seconds and  developed in a 2.38 wt% TMAH aqueous solution. Using a  mask defect monitor M2351 (Lasertec Corp.), development  residues were counted. The total count of defects after  development was determined. The sample was rated good  when the total count of defects is less than 300, or poor when  the total count of defects is equal to or more than 300.  [0352]  Evaluation of Development Residue Defects  [0351]  The patterned mask blank was observed under a  top-down scanning electron microscope (TD-SEM). The  optimum exposure (Eop) was defined as the exposure dose  (µC/cm 2 )  which provided a 1: 1 resolution of a 200-nm 1: 1  line-and-space pattern. The maximum resolution of the  resist was defined as the minimum line width of a LIS  pattern that could be resolved at the optimum exposure. The  LER of a 200-nm LIS pattern was measured under SEM. The  resist pattern was visually observed and judged whether or  not the pattern profile was rectangular.  [0350]  The coated mask blank was exposed to EB using an  EB writer system EBM-5000Plus (NuFlare Technology Inc.,  accelerating voltage 50 kV), then baked (PEB) at 110°  C. for  600 seconds, and developed in a 2.38 wt% TMAH aqueous  solution, thereby yielding a negative resist pattern.  [0349]  Examples 5-1 to 5-2 and Comparative Examples  4-1 to 4-2 Using a coater/developer systemACT-M (Tokyo  Electron Ltd.), each of the resist compositions R16, Rl 7,  R29 and R30 was spin coated onto a mask blank of 152 mm  squares having the outermost surface of silicon oxide (vapor  primed with hexamethyldisilazane) and prebaked on a hot› plate at 110°  C. for 600 seconds to form a resist film of 80  nm thick. The thickness of the resist film was measured by  an optical film thickness measurement system Nanospec  (Nanometrics Inc.). Measurement was made at 81 points in  the plane of the blank substrate excluding a peripheral band  extending 10 mm inward from the blank periphery, and an  average film thickness and a film thickness range were  computed therefrom.  [0348]  It is demonstrated in Table 4 that resist composi› tions comprising sulfonium compounds within the scope of  the invention offer a high sensitivity and improved CDU.  The inventive resist compositions are also useful in the EUV  lithography.  [0344]  As seen from the results of Table 3, the resist  compositions comprising sulfonium compounds within the  scope of the invention offer advantages including a high  sensitivity, a good balance of LWR and MEF, and minimal  defects. These data demonstrate that the inventive resist  compositions are useful in the ArF immersion lithography.  [0345]  Each resist composition (R13 to R15 or R26 to  R28) was spin coated on a silicon substrate having a 20-nm  coating of silicon-containing spin-on hard mask SHB-A940  (silicon content 43 wt%, Shin-Etsu Chemical Co., Ltd.) and  prebaked on a hot plate at 105°  C. for 60 seconds to form a  resist film of 60 nm thick. Using an EUV scanner NXE3300  (ASML, NA 0.33,  a  0.9/0.6, quadrupole illumination), the  resist film was exposed to EUV through a mask bearing a  hole pattern having a pitch 46 nm+20% bias ( on-wafer size).  The resist film was baked (PEB) on a hotplate at 100°  C. for  60 seconds and developed in a 2.38 wt % TMAH aqueous  solution for 30 seconds to form a hole pattern having a size  of 23 nm.  [0346]  The resist pattern was observed under CD-SEM  (CG-5000, Hitachi High-Technologies Corp.). The exposure  dose that provides a hole pattern having a size of 23 nm is  reported as sensitivity. The size of 50 holes was measured,  from which a size variation (30) was computed and reported  as CDU.  [0347]  The resist composition is shown in Table 4 together  with the sensitivity and CDU of EUV lithography.  [6] EB Writing Test  [5] EUV Lithography Test  Examples 4-1 to 4-3 and Comparative Examples  3-1 to 3-3  Resist  Eop  Maximwn  compo- (µC/ resolution  LER Pattern  De- sition  cm 2 )  (nm)  (nm) profile  feels  Example  5-1  R16  49  39  4.5 rectangular  good  5-2  R17  47  43  4.4 rectangular  good  Compar- 4-1  R29  50  58  5.6 inversely  poor  ative  tapered  Example  4-2  R30  49  60  5.8 inversely  poor  tapered  Resist  Sensitivity  CDU  composition  (mJ/cm 2 )  (nm)  Example  4-1  R13  20  2.5  4-2  R14  19  2.7  4-3  R15  21  2.9  Comparative  3-1  R26  25  3.8  Example  3-2  R27  26  4.0  3-3  R28  26  4.1  Resist  Sensitivity LWR  Defect  composition  (mJ/cm 2 )  (nm)  MEF density  3-3  R3  25  3.0  3.0 Good  3-4  R4  27  3.3  3.6 Good  3-5  RS  26  3.1  3.4 Good  3-6  R6  25  3.0  3.5 Good  3-7  R7  26  3.3  2.9 Good  3-8  RS  30  3.4  3.7 Good  3-9  R9  31  3.5  3.5 Good  3-10  RIO  24  3.1  3.3 Good  3-11  Rll  26  3.3  3.3 Good  3-12  R12  27  2.8  2.9 Good  Comparative  2-1  R18  24  4.5  4.8 NG  Example  2-2  R19  29  5.2  5.0 Good  2-3  R20  38  4.4  4.2 NG  2-4  R21  36  4.3  4.2 NG  2-5  R22  33  4.5  4.0 NG  2-6  R23  36  4.0  4.2 NG  2-7  R24  33  3.9  4.7 Good  2-8  R25  37  4.2  4.8 NG 