US 10,781,276 B2  42  41  TABLE I-continued  400 mg of any of the above polymers is dissolved in a  mixed solvent of 4 ml of y-butyrolactone and 4 ml of  cyclohexanone to prepare resist composition samples 1 to 10 40  of Examples 1 to 8 and Comparative Examples 1 and 2. The  polymers used are described in Table 2.  A developer modified for each polymer is prepared by  mixing pure water, methanol, isopropyl alcohol, acetonitrile,  tetrahydrofuran and methyl ethyl ketone, so that 15% by  mass of the polymers 1 to 19 is dissolved therein. A content  of each component is in the range of  O  to 70% by mass.  The resist composition sample 1 is spin-coated on a  silicon wafer modified with hexamethylenedisilazane in  advance. This is prebaked on a hot plate at 110°  C. for 1  minute to obtain a substrate on which a coating film having  a thickness of 200 nm forms. To the coating film on the  substrate, a line and space pattern of 2 µm  is drawn by an  electron beam of30 keVusing an electron beam lithography  system (JSM-6500F, JEOL Ltd.). After irradiation with the  electron beam, the substrate is developed with the developer  for 1 minute and then rinsed with pure water to obtain the  line and space pattern of 2  µm. The irradiation dose at this  time is defined as  Emax  [µC/cm 2 ],  and the sensitivity to the  irradiation with the electron beam is evaluated.  The sensitivity evaluation is also performed on Samples 2  to 10 in the same procedure as above. The results are  described in Table 2.  According to Examples 1 to 3 in Table 2, it is found that  when the polarity conversion of the onium salt is utilized, no  significant difference in sensitivity is observed regardless of  whether compound Al or compound A3 having different  acid strength. On the other hand, when the compound A4  having a hexafluoroantimonate anion is used, since a density  of the film is largely increased by including antimony, the  sensitivity to the electron beam is improved. This is because  the metal atom such as antimony has a greater absorption of  the electron beam than organic atoms such as hydrogen,  carbon, oxygen and fluorine. Therefore, the same effect can  be expected for EUV.  According to the comparison of Examples 1 to 2 and  Comparative Examples 1 to 2, it is found that the sensitivity  of Examples 1 to 2, having both unit A and unit B, is greatly  TABLE 2  UnitD  UnitE  UnitA  Composition  Ratio  (mo!%)  UnitB  Composition  Ratio  (mo!%)  Unite  Composition  Ratio  (mo!%)  Composition Composition  Unit F  Composition Ratio  (mo!%)  Ratio  Ratio  (mol %)  (mol %)  Polymer 3  Compound A3  Compound Bl  20  25  Polymer 4  CompoundA4 Compound Bl  20  25  Polymer 5  Compound  AS  Compound Bl  20  25  Polymer 6  Compound A6  Compound Bl  20  25  Polymer 7  Compound Al  Compound B4  20  25  Polymer 8  Compound Al  Compound B5  20  25  Polymer 9  Compound Al  Compound B6  20  25  Polymer 10  Compound Al  Compound Bl  20  25  Polymer 11  Compound Al  Compound Bl  20  25  Polymer 12  Compound Al  Compound Bl  20  25  Polymer 13  Compound Al  Compound Bl  20  25  Polymer 14  Compound Al  Compound Bl  20  25  Polymer 15  Compound Al  Compound Bl  20  25  Polymer 16  CompoundA4 Compound Bl  20  25  Polymer 17  Compound A6  Compound Bl  20  25  Polymer 18  Compound Al  40  Polymer 19  Compound Al  40  Compound C2  10  Compound C2  10  Compound Cl  10  Monomer D  10  Monomer D  10  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2 Monomer F3  15  30  10  Monomer Fl Monomer F2  15  30  Monomer Fl Monomer F2 Monomer F5  25  30  10  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  25  30  Monomer Fl Monomer F2  15  30  Monomer El Monomer Fl Monomer F2  15  15  15  Monomer Fl Monomer F2  30  30  Monomer Fl Monomer F2  30  30  Resist  Composition  Sensitivity  (Emaxl  Sample  Polymer  [µC/cm 2 ]  Example 1  Sample 1  Polymer 1  50.0  Example 2  Sample 2  Polymer 3  50.0  Example 3  Sample 3  Polymer 4  42.5  Example 4  Sample 4  Polymer 7  42.5  Example 5  Sample 5  Polymer 10  45.0  Example 6  Sample 6  Polymer 12  45.0  Example 7  Sample 7  Polymer 13  40.0  Example 8  Sample 8  Polymer 17  37.5  Comparative  Sample 9  Polymer 18  120  Example 1  Comparative  Sample 10  Polymer 19  125  Example 2  <Preparation of Resist Composition>  <Preparation of Developer>  <Evaluation of Electron Beam Sensitivity> 