content_image/913137.jpg content_image/913139.jpg content_image/913140.jpg content_image/913141.jpg content_image/913142.jpg content_image/913143.jpg content_image/913144.jpg content_image/913138.jpg content_image/913151.jpg
<img src='content_image/913137.jpg'>

<img src='content_image/913139.jpg'>

<img src='content_image/913140.jpg'>

<img src='content_image/913141.jpg'>

Each of formulas (L4-1) to (L4-4), (L4-3-l) and (L4-3-2), and (L4-4-1) to (L4-4-4) collectively represents an enanti› omer thereof and a mixture of enantiomers. 

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-l) and (L4-3-2), and (L4-4-1) to (L4-4-4), the bond 35 direction is on the exo side relative to the bicyclo[2.2.1] heptane ring, which ensures high reactivity for acid catalyzed elimination reaction (see JP-A 2000-336121). In preparing these monomers having a tertiary exo-alkyl group ofbicyclo [2.2.1 ]heptane skeleton as a substituent group, there may be 40 contained monomers substituted with an endo-alkyl group as represented by the following formulas (L4-1-endo) to (L4-4- endo ). For good reactivity, an exo proportion of at least 50 mo! % is preferred, with an exo proportion of at least 80 mo! 45 % being more preferred. 

<img src='content_image/913142.jpg'>

<img src='content_image/913143.jpg'>

<img src='content_image/913144.jpg'>

<img src='content_image/913138.jpg'>

Illustrative examples of the acid labile group of formula (L4) are given below. 

<img src='content_image/913151.jpg'>

Examples of the tertiary C$_{4}$ -C$_{20 }$alkyl groups, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms, and C$_{4}$ -C$_{20 }$oxoalkyl groups are as exemplified for RL 04 . 

An appropriate proportion "s" of repeat units having acid labile group RsA is 0<ss0.8, and more preferably 0.1 <ss0.5. A proportion "r" of the acid labile group-containing repeat units of formula (1) or (2) and a proportion "s" ofrepeatunits having acid labile group RsA are preferably so related to provide the range: 0.1 <r+ss0.8, and more preferably 0.2<r+ ss0.65. Although values of rands outside the range need not be positively excluded, sometimes a balance of properties required of resist material may be broken. 

RsB has a lactone structure as its partial structure and pref- erably stands for a group containing a 5 or 6-membered lactone ring. Exemplary groups are shown below, but not limited thereto. 

