content_image/941802.jpg content_image/941795.jpg content_image/941796.jpg content_image/941797.jpg content_image/941798.jpg
n represents an integer of0 to 3, preferably an integer of0 to 2, more preferably 0 or 1, and most preferably 1. 

When the structural unit is included in the component (Al’) the amount of the structural unit (al) based on the combined total of all structural units constituting the component (Al’) is preferably 10 to 80 mo! %, more preferably 20 to 70 mo! %, and still more preferably 25 to 60 mo!%. When the amount of the structural unit (al) is at least as large as the lower limit of the above-mentioned range, a pattern can be easily formed using a resist composition prepared from the component (Al). On the other hand, when the amount of the structural unit (al) is no more than the upper limit of the above-men› tioned range, a good balance can be achieved with the other structural units. 

(Structural Unit (a2)) 

The component (Al’) may also have a structural unit (a2) derived from an acrylate ester containing a lactone-contain› ing cyclic group, as long as the effects of the present invention are not impaired. 

The term "lactone-containing cyclic group" refers to a cyclic group including one ring containing a -O----C(O)› structure (lactone ring). The term "lactone ring" refers to a single ring containing a---0-C(O)-structure, and this ring is counted as the first ring. A lactone-containing cyclic group in which the only ring structure is the lactone ring is referred to as a monocyclic group, and groups containing other ring structures are described as polycyclic groups regardless of the structure of the other rings. 

When the component (Al’) is used for forming a resist film, the lactone-containing cyclic group of the structural unit (a2) is effective in improving the adhesion between the resist film and the substrate, and increasing the compatibility with the developing solution containing water. 

As the structural unit (a2), there is no particular limitation, and an arbitrary structural unit may be used. 

Specific examples of lactone-containing monocyclic groups include a group in which one hydrogen atom has been removed from a 4- to 6-membered lactone ring, such as a group in which one hydrogen atom has been removed from ~-propiolatone, a group in which one hydrogen atom has been removed from y-butyrolactone, and a group in which one hydrogen atom has been removed from 1\-valerolactone. Fur› ther, specific examples of lactone-containing polycyclic groups include groups in which one hydrogen atom has been removed from a lactone ring-containing bicycloalkane, tricy› cloalkane or tetracycloalkane. 

More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2- 1) to (a2-5) shown below. 

[Chemical Formula 50] 

<img src='content_image/941802.jpg'>

(a2-1) 

<img src='content_image/941795.jpg'>

<img src='content_image/941796.jpg'>

<img src='content_image/941797.jpg'>

<img src='content_image/941798.jpg'>

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; each R’ independently represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms or----COOR", wherein R" represents a hydrogen atom or an alky I group; R $^{29 }$represents a single bond or a divalent linking group; s" represents an integer of0 to 2; A" represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom; and m represents 0 or 1. 

In general formulas (a2-1) to (a2-5), R is the same as defined for R in the structural unit (al). 

Examples of the alkyl group of 1 to 5 carbon atoms for R’ include a methyl group, an ethyl group, a propyl group, an n-butyl group and a tent-butyl group. 

-continued 

(a2-2) 

(a2-3) 

(a2-4) 

(a2-5) 

