37  US 9,958,775 B2  38  -continued  -continued  •:t•  •:x:•  ~~  vy  vy  OH  OH  OH  OH  Cl  OMe  OH  •:t•  ¢  OH  •:t•  •:x:•  ~  ¢o1~  yv  ~  #  OH  OH  OH  OH  The compound (Bl) preferably have a structure in which  a hydrogen atom of a phenolic hydroxyl group is substituted  with a group having an acid-non-decomposable polycyclic  aliphatic hydrocarbon structure due to obtaining the high  glassy-transition temperature (Tg) and becoming excellent  dry etching resistance.  By the compound (Bl) having the specific structure  described before, the glassy-transition temperature (Tg) of  the compound (Bl) becomes higher, and it is possible to  form a very hard resist film and to control the diffusion of an  acid and dry etching resistance. Therefore, since the diffu› sion of an acid is highly controlled at the exposed portion of  actinic rays or radiation such as an electron beam or extreme  ultraviolet rays, resolving power, a pattern shape and LER in  a fine pattern are further improved. In addition, since the  compound (Bl) has an acid-non-decomposable polycyclic  aliphatic hydrocarbon structure, it is considered that this  contributes to further improve dry etching resistance. Also,  although the details are not clearly understood, it is specu› lated that since the polycyclic aliphatic hydrocarbon struc- ture has a high hydrogen radical donating property and  serves as a hydrogen source at the time of the decomposition  of the compound (A) which is a photo-acid generator or (D)  a compound which generates an acid by irradiation with  actinic rays or radiation described later, the decomposition  efficiency of the photo-acid generator is further improved  and the acid generation efficiency is further increased, and it  is considered that this contributes to further excellent sen› sitivity.  In the specific structure described before in which the  compound (Bl) according to the present invention may  have, an aromatic ring such as a benzene ring and a group  having an acid-non-decomposable polycyclic aliphatic  hydrocarbon structure are linked through an oxygen atom  derived from a phenolic hydroxyl group. As described  before, the structure not only contributes high dry etching  resistance but also can increase the glassy-transition tem› perature (Tg) of the compound (Bl), and it is speculated that  higher resolving power is provided due to the effect of this  combination.  In the present invention, acid-non-decomposable means  the property in which the decomposition reaction dose not  occur by an acid generated by the compound (A) and (D) a  compound which generates an acid by irradiation with  actinic rays or radiation described later.  More specifically, a group having an acid-non-decompos› able polycyclic aliphatic hydrocarbon structure is preferably  a group which is stable with respect to an acid and an alkali.  A group which is stable with respect to an acid and an alkali  means a group which does not show acid-decomposable and  alkali-decomposable. Here, acid-decomposable means the  property in which the decomposition reaction occurs by the  action of an acid generated by the compound (A) and (D) a 