Jul.  18,  2019  59  US 2019/0219920 Al  romethyl group, -CH 2 -CF 3 , ----CH 2 ----CF 2 -CF 3 , --CH  (CF 3 ) 2 , ----CH 2 ----CH 2 ----CF 3 , and -CH 2 ----CH 2 ----CF 2 - CF2-CF2-CF3 are most preferable.  [0518]  The weight average molecular weight (Mw) (the  polystyrene equivalent value determined by gel permeation  chromatography) of the component (F) is preferably 1,000  to 50,000, more preferably 5,000 to 40,000, and most  preferably 10,000 to 30,000. When the Mw of the compo› nent (F) is no more than the upper limit of the above› mentioned range, the resist composition exhibits a satisfac› tory solubility in a resist solvent. On the other hand, when  the Mw is at least as large as the lower limit of the  above-mentioned range,  dry  etching resistance and the  cross-sectional shape of the resist pattern becomes satisfac› tory.  [0519]  Further, the dispersity (Mw/Mn) of the component  (F) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and  most preferably 1.2 to 2.5.  [0520]  As the component (F), one type may be used alone,  or two or more types may be used in combination.  [0521]  When the resist composition contains the compo› nent (F), the component (F) is used in an amount within a  range from 0.5 to 10 parts by weight, relative to 100 parts by  weight of the component (A).  [0522]  If desired, other miscible additives can also be  added to the resist composition of the present invention.  Examples of such miscible additives include additive resins  for improving the performance of the resist film, dissolution  inhibitors, plasticizers, stabilizers, colorants, halation pre› vention agents, and dyes.  [0523]  <<Organic Solvent (S)>>  [0524]  The resist composition of the present embodiment  may be prepared by dissolving the resist materials for the  resist composition in an organic solvent (hereafter, referred  to as "component (S)").  [0525]  The component (S) may be any organic solvent  which can dissolve the respective components to give a  homogeneous solution, and any organic solvent can be  appropriately selected from those which have been conven› tionally known as solvents for a chemically amplified resist  composition.  [0526]  Examples of the component (S) include lactones  such as y-butyrolactone; ketones such as acetone, methyl  ethyl ketone,  cyclohexanone,  methyl-n-pentyl  ketone,  methyl isopentyl ketone, and 2-heptanone; polyhydric alco› hols, such as ethylene glycol, diethylene glycol, propylene  glycol and dipropylene glycol; compounds having an ester  bond, such as ethylene glycol monoacetate, diethylene gly› col monoacetate, propylene glycol monoacetate, and dipro› pylene glycol monoacetate; polyhydric alcohol derivatives  including compounds having an ether bond, such as a  monoalkylether (e.g., monomethylether, monoethylether,  monopropylether or monobutylether) or monophenylether  of any of these polyhydric alcohols or compounds having an  ester bond (among these, propylene glycol monomethyl  ether acetate (PGMEA) and propylene glycol monomethyl  ether (PGME) are preferable); cyclic ethers such as dioxane;  esters such as methyl lactate, ethyl lactate (EL), methyl  acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl  pyruvate, methyl methoxypropionate, and ethyl ethoxypro› pionate; aromatic organic solvents such as anisole, ethyl› benzylether, cresylmethylether, diphenylether, dibenzyle› ther,  phenetole,  butylphenylether,  ethylbenzene,  [0536]  Further, by virtue of the acid dissociable group  containing a polar group, solubility in a developing solution  containing an organic solvent may be maintained at a low  level. Therefore, in a solvent developing process, in the case  where the acid dissociable group is not decomposed and  remains at exposed portions of the resist film, or in the case  where a decomposition product remains in the resist film, the  dissolution rate of the exposed portions of the resist film in  an organic developing solution may be suppressed from  being increased, such that film loss of pattern portions may  [0535]  By virtue of the acid dissociable group containing  a quaternary carbon atom (Ya 0 ),  acid dissociability upon  exposure in the formation of a resist pattern may be reliably  improved, as compared to the case where the acid disso› ciable group contains a tertiary carbon atom. Therefore, the  reactivity may be improved, and sensitivity may be  enhanced. In addition, a high dissolution contrast may be  obtained by developing.  [0534]  In the resist composition of the present embodi› ment, as the base component (A), a polymeric compound  (Al) having a structural unit (a0) represented by general  formula (a0-1) is used. The structural unit (a0) has an acid  dissociable group represented by general formula (a0-rl-1)  on the terminal of the side-chain thereof. The acid disso› ciable group contains a quaternary carbon atom (Ya 0 )  and a  polar group.  [0533]  According to the resist composition of the present  embodiment described above, sensitivity may be enhanced  in the formation of a resist pattern, and the shape of the resist  pattern may be further improved.  [0532]  The amount of the component (S) is not particu› larly limited, and is appropriately adjusted to a concentration  which enables coating of a coating solution to a substrate. In  general, the component (S) is used in an amount such that  the solid content of the resist composition becomes within  the range from 1 to 20% by weight, and preferably from 2  to 15% by weight.  [0531]  Further, as the component (S), a mixed solvent of  at least one of PGMEA and EL with y-butyrolactone is also  preferable. The mixing ratio (former:latter) of such a mixed  solvent is preferably from 70:30 to 95:5.  [0530]  Specifically, when EL or cyclohexanone is mixed  as the polar solvent, the PGMEA:EL or cyclohexanone  weight ratio is preferably from 1:9 to 9:1, and more pref› erably from 2:8 to 8:2. Alternatively, when PGME is mixed  as the polar solvent, the PGMEA:PGME weight ratio is  preferably from 1:9 to 9: 1, more preferably from 2:8 to 8:2,  and still more preferably 3:7 to 7:3. Furthermore, a mixed  solvent of PGMEA, PGME and cyclohexanone is also  preferable.  [0529]  Further, among the mixed solvents, a mixed sol› vent obtained by mixing PGMEA with a polar solvent is  preferable. The mixing ratio (weight ratio) of the mixed  solvent can be appropriately determined, taking into con› sideration the compatibility of the PGMEA with the polar  solvent, but is preferably in the range of 1:9 to 9:1, more  preferably from 2:8 to 8:2.  [0528]  Among these, PGMEA, PGME, y-butyrolactone,  EL and cyclohexanone are preferable.  [0527]  The component (S) can be used individually, or in  combination as a mixed solvent.  diethylbenzene, pentylbenzene, isopropylbenzene, toluene,  xylene, cymene and mesitylene; and dimethylsulfoxide  (DMSO). 