US 10,323,113 B2  84  83  -continued  The acid labile groups represented by R$^{11 }$and R$^{12 }$in the  recurring units (al) and (a2) may be selected from a variety  of such groups, for example, those groups described in JP-A  2013-080033 (U.S. Pat. No. 8,574,817) and JP-A 2013- 083821 (U.S. Pat. No. 8,846,303).  Typical of the acid labile group are groups of the follow› ing formulae (AL-1) to (AL-3).  (AL-1)  (AL-2)  (AL-3)  In formulae (AL-1) and (AL-2), R 15  and R 18  are each  independently a monovalent hydrocarbon group of 1 to 40  carbon atoms, preferably 1 to 20 carbon atoms, typically  straight, branched or cyclic alkyl, which may contain a  heteroatom such as oxygen, sulfur, nitrogen or fluorine. R 16  and R  1 7  are each independently hydrogen or a monovalent  hydrocarbon group of 1 to 20 carbon atoms, typically  straight, branched or cyclic alkyl, which may contain a  heteroatom such as oxygen, sulfur, nitrogen or fluorine. Al  is an integer of 0 to 10, especially 1 to 5. A pair of R $^{16 }$and  R 17 , R $^{16 }$and R18 , or R $^{17 }$and R$^{18 }$may bond together to form  a ring, typically alicyclic, with the carbon atom or carbon  and oxygen atoms to which they are attached, the ring  containing 3 to 20 carbon atoms, preferably 4 to 16 carbon  atoms.  In formula (AL-3), R 19 , R $^{20 }$and R21 are each indepen› dently a monovalent hydrocarbon group of 1 to 20 carbon 55  atoms, typically straight, branched or cyclic alkyl, which  may contain a heteroatom such as oxygen, sulfur, nitrogen  or fluorine. A pair ofR$^{19 }$and R 20 , R $^{19 }$and R21 , or R $^{20 }$and  R 21  may bond together to form a ring, typically alicyclic,  with the carbon atom to which they are attached, the ring 60  containing 3 to 20 carbon atoms, preferably 4 to 16 carbon  atoms.  The base polymer may further comprise recurring units  (b) having a phenolic hydroxy group as an adhesive group.  Examples of suitable monomers from which recurring units  (b) are derived are given below, but not limited thereto.  Herein  RA  is as defined above.  Rl6  I  -C-O-R 18  I  Rn  Rl9  I  -C-R21  I  R20  25’  OH  00  ~  4~  OH  OH 