US 9,097,971 B2  42  41  Among these, as the radical polymerization initiator (I),  compounds represented by the formulae (Il) to (I5) are pref› erable, and the compound represented by the formula (I 1) is  particularly preferable.  As the organic cation for M+, organic cations represented  by the aforementioned formulae ( c-1) to ( c-3) are preferable,  and an organic cation represented by the aforementioned  formula ( c-1) is particularly preferable.  As an another method of producing the polymeric com› pound of the present invention, a method in which by using a  compound (IO) represented by general formula (IO) shown  below as a radical polymerization initiator, a polymeric com› pound (polymeric compound precursor) which has a group  represented by general formula (I-01) shown below on at least  one terminal of the main chain, and thereby, a group  "-(OCO)q-R$^{2}$-(CF$_{2}$)r-So$_{3}$-A+" (wherein q, R 2 ,  rand  A+ are the same as defined above) is introduced on the termi› nal of the main chain of the polymeric acid precursor (that is,  the hydrogen atom on the terminal of the main chain is sub- stituted with the aforementioned group).  As the compound (IO), a known compound can be used.  The introduction of the group "-(OCO)q-R $^{2 }$-(CF  $_{2}$)r› S03 -A+" can be performed by a conventional method, and for  example, can be conducted by reacting the polymeric com- pound precursor with a compound (i-02) represented by gen› eral formula (i-02) shown below. The reaction can be per› formed as in the method explained in relation to the method of  producing a compound (I) of the third aspect.  [Chemical Formula 22]  (10)  (1-01)  (i-02)  In the formulae, R1, Z, X, Q, p, q, R 2 ,  r, M+, B$^{1 }$and B$^{2 }$are  the same as defined above.  The resist composition of the fifth aspect of the present  invention includes a polymeric compound of the fourth  aspect. By including the polymeric compound of the present  invention, a resist film formed using the resist composition  has an ability to generate acid upon exposure.  Therefore, by including the polymeric compound of the  present invention, a resist film can form a pattern using a  component which exhibits changed solubility by the action of  acid, even when the resist film does not contain an acid  generator. In the case where an acid generator is included in  addition to the polymeric compound of the present invention,  sensitivity can be improved, as compared to the case where  the polymeric compound of the present invention is not  included.  The resist composition of the fifth aspect of the present  invention may include the polymeric compound of the fourth  aspect of the present invention as a resin component which  constitutes a base component that exhibits changed solubility  in a developing solution by the action of acid, or may include  the polymeric compound of the fourth aspect of the present  invention in addition to a resin component which constitutes  a base component. That is, the polymeric compound con› tained in the resist composition of the present invention may  be a polymeric compound which exhibits changed solubility  Here, the term "base component" refers to an organic com› pound capable of forming a film, and is preferably an organic  compound having a molecular weight of 500 or more. When  the organic compound has a molecular weight of 500 or more,  the film-forming ability is improved, and a resist pattern of  nano level can be easily formed. The "organic compound  having a molecular weight of 500 or more" which can be used  as a base component is broadly classified into non-polymers  and polymers. In general, as a non-polymer, any of those  which have a molecular weight in the range of 500 to less than  4,000 is used. Hereafter, a non-polymer having a molecular  weight in the range of 500 to less than 4,000 is referred to as  a low molecular weight compound. As a polymer, any of  those which have a molecular weight of 1,000 or more is  generally used. Hereafter, a polymer having a molecular  weight of 1,000 or more is referred to as a polymeric com› pound. With respect to a polymeric compound, the "molecu› lar weight" is the weight average molecular weight in terms of  the polystyrene equivalent value determined by gel perme› ation chromatography (GPC). Hereafter, a polymeric com› pound is frequently referred to simply as a "resin".  As described above, in a chemically amplified resist com› position, a base component which exhibits changed solubility  in a developing solution under action of acid is generally  used.  In general, a chemically amplified resist composition  includes a base component which exhibits changed solubility  in a developing solution under action of acid, and an acid  generator component which generates acid upon exposure.  When the resist composition is subjected to exposure, acid is  generated from the acid generator component, and the action  of that acid causes a change in the solubility of the base  component in a developing solution. As a result, in the for› mation of a resist pattern, when a resist film obtained using  the resist composition is subjected to selective exposure, the  solubility in the developing solution of the exposed portions  of the resist film changes (the solubility is increased in the  case of positive tone, whereas the solubility is decreased in  the case of negative tone) whereas the solubility in the devel› oping solution of the unexposed portions remains unchanged.  By developing the resist film, a resist pattern can be formed.  The resist composition of the present invention can be used  as a non-chemically amplified resist composition or a chemi- cally amplified resist composition. In the present invention, it  is particularly preferable to use the resist composition as a  chemically amplified resist composition in terms of forming  a resist pattern with high sensitivity and high resolution.  In the present specification, a resist composition which  forms a positive pattern by dissolving and removing the  exposed portions is called a positive resist composition, and a  resist composition which forms a negative pattern by dissolv› ing and removing the unexposed portions is called a negative  resist composition.  The resist composition of the present invention may be  either a negative resist composition or a positive resist com› position.  0  M  <<Resist Composition>> 