Feb.4,2021  102  US 2021/0033969 Al  2013-080033 (U.S. Pat. No. 8,574,817) and JP-A 2013- 083821 (U.S. Pat. No. 8,846,303).  [0108]  Typical of the acid labile group are groups of the  following formulae (AL-1) to (AL-3).  [0109]  In formulae (AL-1) and (AL-2),  RL 1  and  RL 2  are  each independently a C$_{1 }$-C$_{40 }$hydrocarbyl group which may  contain a heteroatom such as oxygen, sulfur, nitrogen or  fluorine. The hydrocarbyl groups may be saturated or  unsaturated and straight, branched or cyclic. Of the hydro› carbyl groups, C$_{1 }$-C$_{40}$ , especially C $_{1 }$-C$_{20 }$ alkyl groups are  preferred. In formula (AL-1), "a" is an integer of Oto 10,  preferably 1 to 5.  [0110]  In formula (AL-2),  RL 3  and  RL 4  are each indepen› dently hydrogen or a C$_{1 }$-C$_{20 }$hydrocarbyl group which may  contain a heteroatom such as oxygen, sulfur, nitrogen or  fluorine. The hydrocarbyl groups may be saturated or  unsaturated and straight, branched or cyclic. Of the hydro› carbyl groups, C$_{1 }$-C$_{20 }$alkyl groups are preferred. Any two of  RL 2 ,  RL $^{3 }$and  RL $^{4 }$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.  [0111]  In formula (AL-3),  RL 5 ,  RL 6  and  Rn  are each  independently a C$_{1 }$-C$_{20 }$hydrocarbyl group which may con› tain a heteroatom such as oxygen, sulfur, nitrogen or fluo› rine. The hydrocarbyl groups may be saturated or unsatu› rated and straight, branched or cyclic. Of the hydrocarbyl  groups, C$_{1 }$-C$_{20 }$alkyl groups are preferred. Any two of  RL 5 ,  RL 6  and  RL 7  may bond together to form a ring, typically  alicyclic, with the carbon atom to which they are attached,  the ring containing 3 to 20 carbon atoms, preferably 4 to 16  carbon atoms.  [0112]  The base polymer may further comprise recurring  units (b) having a phenolic hydroxyl group as an adhesive  group. Examples of suitable monomers from which recur› ring units (b) are derived are given below, but not limited  thereto. Herein  RA  is as defined above.  [0113]  Further, recurring units ( c) having another adhesive  group selected from hydroxyl (other than the foregoing  phenolic hydroxyl), lactone ring, sultone ring, ether bond,  ester bond, sulfonate bond, carbonyl, sulfonyl, cyano, and  carboxyl groups may also be incorporated in the base  polymer. Examples of suitable monomers from which recur› ring units ( c) are derived are given below, but not limited  thereto. Herein  RA  is as defined above.  (AL-1)  (AL-2)  (AL-3)  -continued  IRA  ()  HO  OH 