US 10,007,180 B2  152  151  ing power (run) was defined as the limiting resolving power  (minimum line width permitting the separation and resolu› tion of a line and a space (line:space=l: 1 )) in the exposure  amount in which a 50 run line width 1: 1 line and space resist  pattern was resolved.  [Pattern Shape]  The smaller the value, the more favorably smaller the  performance change by temperature change.  [Evaluation of PED (Post-Exposure Time Delay) Stabil› ity]  The shape of cross section of each 50 run line width 1: 1  line and space pattern in the exposure amount exhibiting the  above sensitivity was observed by means of a scanning  electron microscope (model S-4300, manufactured by  Hitachi, Ltd.). The shape of cross section of each line pattern  when the ratio of [line width of line pattern at its top portion  (surface portion)/line width of line pattern at its middle  portion (position at half of the height of the line pattern)]  was 1.2 or greater was graded into "inverted taper"; that  when the ratio was in the range of 1.05 to less than 1.2 was  graded into "slightly inverted taper"; and that when the ratio  was less than 1.05 was graded into "rectangle."  [Line Edge Roughness (LER)]  The smaller the value, the more favorable the perfor› mance exhibited. The value was used as an index of PED  stability.  Exposure was performed in the exposure amount in which  the dimension of the 50 run line width  1:  1 line and space  pattern was 50 run. Immediately thereafter, PEB was per› formed, and the line width dimension (0 h) was measured.  Separately, PEB was performed two hours after the expo- lO sure, and the line width dimension (2.0 h) on the wafer was  measured. The line width change ratio was calculated by the  following formula:  A 50 run line width 1: 1 line and space pattern was formed  in the exposure amount exhibiting the above sensitivity. At  arbitrary 30 points within 50 µmin  the longitudinal direction  of the pattern, the distance between actual edge and a  reference line on which edges were to be present was  measured by means of a scanning electron microscope  (model S-9220, manufactured by Hitachi, Ltd.). The stan› dard deviation of measured distances was determined, and  3a  was computed therefrom. The smaller the value thereof,  the more favorable the performance exhibited.  From the results of Table 4, it is apparent that the  compositions of the present invention exhibit enhanced  sensitivity, resolving power, pattern shape and LER perfor› mance, and realizes low dependence on PEB temperature  and excellent PED stability, in the exposure to EUV.  [Dependence on PEB Temperature]  The optimum exposure amount was defined as the expo› sure amount in which a 1: 1 line and space of 50 run mask  size was reproduced upon post-exposure bake (PEB) at 110°  C. for 90 seconds. The exposure in the optimum exposure  amount was followed by subsequent bakes at two tempera› tures, one being the above temperature+2°  C. (namely 112°  C.) and the other being the above temperature-2°  C.  (namely 108°  C.). The resultant line and space patterns were  measured, thereby determining line width L1 and line width  L2 thereof. The dependence on PEB temperature (PEBS)  was defined as the variation of line width per PEB tempera› ture change 1 °  C., and was calculated by the following  formula:  (1) Preparation of Resist Composition and Formation of  Resist Film  Each of the compositions indicated in Table 5 below was  precision filtered through a membrane filter of 0.1  µm  pore  diameter, thereby obtaining a resist composition.  Each of the obtained resist compositions was applied onto  a 6-inch Si wafer having been treated with hexamethyldisi› lazane (HMDS) by means of a spin coater Mark 8 manu› factured by Tokyo Electron Limited, and dried on a hot plate  at 100°  C. for 60 seconds, thereby obtaining a 50 run-thick  resist film.  (2) Exposure to EB and Development  Each of the wafers coated with resist films that were  obtained in section (1) above was patternwise exposed to  electron beams by means of an electron beam lithography  system (HL 750 manufactured by Hitachi, Ltd., acceleration  voltage 50 KeV). The lithography was performed so as to  Examples 1 C to 6C and Comparative Examples 1 C  and 2C: Exposure to EB; Negative; Organic  Solvent Development  TABLE 4  (EUV exposure; negative; alkali developer)  LIS resolving  Sensitivity  power  Pattern  LER  Dependence on  Ex.  Comp.  (mJ/cm 2 )  (nm)  shape  (nm)  PEB temp  PED stability  lF  Nl0  2F  N15  3F  N16  4F  N17  SF  N18  6F  N19  Comparative Comparative  Ex. lF  comp. Nl  Comparative Comparative  Ex. 2F  comp. N2  Comparative Comparative  Ex. 3F  comp. N3  Comparative Comparative  Ex. 4F  comp. N4  15.8  15.7  15.8  15.6  15.8  15.5  15.5  15.6  15.5  15.6  20  Rectangle  4.1  0.2  0.2  20  Rectangle  4.0  0.2  0.2  20  Rectangle  4.1  0.2  0.2  20  Rectangle  4.2  0.2  0.2  20  Rectangle  4.0  0.2  0.2  20  Rectangle  4.1  0.2  0.2  30  Inverted taper  5.2  2.5  2.5  30  Inverted taper  5.1  2.4  2.5  30  Slightly  5.1  0.8  0.9  inverted taper  30  Slightly  5.2  0.8  0.9  inverted taper  Line width change ratio (%)~L\.CD(2.0 h-0 h)nm/50  nm  Dependence on PEB temperature (nm/ 0  C.)~IL1- L21/4 