based on the weight of the imaging polymer. The resists  were spin coated onto respective HMDS-primed wafers. The  resist-coated wafers were baked on a hot plate at 110°  C. for  1 minute. The resist-coated wafers were exposed using an  IBM-built 25 kV Gaussian-beam system (FELS). After  exposure, resists were baked at 110°  C. for 1 minute before  being developed with 0.263 N TMAH for 60s. The follow› ing table lists profiles for 150 nm and 200 nm 1/s images with  different TPS TRF and DMPHS PFBUS loadings at both 1.5  µC/cm 2  and 2.0 µC/cm 2 .  imaging polymer. The resists were spin coated onto respec› tive HMDS-primed wafers. The wafers were baked on a hot  plate at 110°  C. for 1 minute. The resist-coated wafers were  exposed at 25 kV on ElectronCure™-200M flood exposure  tool manufactured by Electron Vision Group. After expo› sure, resists were baked at 110°  C. for 1 minute before being  developed with 0.263 N TMAH for 60s. The following table  lists the doses to clear large square exposed with different  DMPHS PFBUS loadings.  Resist formulations were obtained in the manner of  Example 4 except that a combination ofDMPHS PFBUS of  Example 1 and DMPS from Example 2 was substituted for  TPS TRF. The loading of the acid generators is indicated in  the table below based on the weight of the imaging polymer.  The resists were spin coated onto respective HMDS› primed wafers. The resist-coated wafers were baked on a hot  plate at 110°  C. for 1 minute. The resist-coated wafers were  exposed using an IBM-built 25 kV Gaussian-beam system  (FELS). After exposure, resists were baked at 110°  C. for 1  minute before being developed with 0.263 N TMAH for 60s.  The following table lists the doses to resolve 150 nm 1/s  images with different DMPS PFBUS and DMPHS PFBUS  loadings and image profiles.  A study of resist performance characteristics ( e.g., dose  latitude, resist profile as related to unexposed dissolution,  sensitivity, and E$_{0}$/Ecn) was performed to determine an  optimal composition using the imaging polymer of Example  3 and the combination of acid generators of Example 7.  From this study, it appears that a composition having 0.28  wt.% TBAH, 7 wt.% TPS TRF and 7.37 wt.% DMPHS  PFBUS provided the best overall performance (31 % dose  latitude, 7.4 A/second unexposed dissolution rate, an E$_{0}$ /  Es,ze of 0.74, and a sensitivity of 3.9 mC/cm 2  with vertical  resist profiles).  Wafers coated with this formulation in the manner of  Example 4 were then imaged on a soft x-ray (1.1 nm  wavelength) lithography tool from JMAR Technologies Inc.  Using soft x-ray, the resist of the invention required a dose  of less than 15 mJ/cm 2 .  Commercial resists would have an  exposure dose requirement in the range of 50-90 mJ/cm $^{2 }$for  the same soft x-ray exposure process.  What is claimed is:  1.  A resist composition comprising (a) an imaging poly› mer, and (b) a radiation sensitive acid generator component,  said radiation sensitive acid generator component compris› ing:  (i) a first radiation sensitive acid generator selected from  the group consisting of dissolution-inhibiting acid gen› erators, and  (ii) a second radiation sensitive acid generator selected  from the group consisting of unprotected acidic group› functionalized radiation sensitive acid generators.  2.  The resist composition of claim  1  wherein said imaging  polymer comprises a ketal-functionalized acid sensitive  polymer.  3.  The resist composition of claim  1  wherein said second  radiation-sensitive acid generator is an acidic group-func- Resist formulations were obtained in the manner of  Example 4 except that a combination ofDMPHS PFBUS of  Example 1 and TPS TRF was substituted for TPS TRF. The  loading of the acid generators is indicated in the table below  DMPS  DMPHS  Dose to  PFBUS  PFBUS  resolve  Image  Sample  loading  loading  100 nm 1/s  profile  2x DMPS  1.49 wt.%  Owt. %  4.5 µC/cm 2  undercut  (1/0)  (comparison)  Mix a (3/1)  0.56 wt.%  0.82 wt.%  5 µC/cm 2  square and  straight  Mix b (1/1)  0.74 wt.%  1.64 wt.%  5 µC/cm 2  square and  straight  Mix c (1/3)  0.37 wt.%  2.45 wt.%  5 µC/cm 2  square and  straight  4x DMPHS  Owt. %  3.27 wt.%  5 µC/cm 2  slightly  (0/1)  rounding  (comparison)  on top  DMPHS  Image  Image  TPS TRF  PFBUS  profile at  profile at  Sample  loading  loading  1.5 µC/cm 2  2.0 µC/cm 2  8x TPS TRF  5.6 wt.%  Owt. %  undercut  undercut  (1/0)  (comparison)  Mix d (3/1)  4.2wt. %  3.28 wt.%  slightly  slightly  undercut  undercut  Mix e (1/1)  2.8 wt.%  6.55 wt.%  square and  square and  straight  straight  Mix f(l/3)  1.4wt. %  9.83 wt.%  square and  slightly  straight  rounding and  straight  16x DMPHS  Owt. %  13.10 wt.%  severe  severe  PFBUS (0/1)  rounding and rounding and  (comparison)  film loss  film loss  DMPHS PFBUS loading E$_{0}$ ,  dose to clear  0.82 wt. %  12 µC/cm 2  3.28 wt. %  4 µC/cm 2  4.91 wt. %  3 µC/cm 2  6.55 wt. %  2.5 µC/cm 2  8.19 wt. %  2.1 µC/cm 2  12.28 wt. %  1.5 µC/cm $^{2 }$(start to see extra thinning)  EXAMPLE6  Resist with Mixed Acid Generators (DMPS PFBUS  and DMPHS PFBUS) According to the Invention  EXAMPLE 8  Optimized Formulation  EXAMPLE 7  Resist with Mixed Acid Generators (TPS TRF and  DMPHS PFBUS) According to the Invention  10  US 7,314,700 B2  9 