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pattern by a first step of exposure and etching, shifting the position, processing a second underlay formed below the first underlay by a second step of exposure through the 1 :3 isolated left pattern, for forming a half-pitch 1: 1 pattern. 

A further embodiment of the invention provides a photo- mask blank comprising a chromium compound film and a coating of the positive resist composition deposited thereon. In this embodiment, a pattern may be formed by heat treating the photomask blank, subjecting the resist coating to pattern- wise exposure to high-energy radiation through a photomask or patternwise exposure to high-energy beam, optionally heat treating the exposed resist coating, and developing it with a developer. The chromium compound film may be of CrO, CrC, CrN, CrON, CrOC, CrONC, CrNC or the like. 

Examples of the invention are given below by way of 20 illustration and not by way of limitation. The copolymer composition is expressed in molar ratio. The abbreviation Me is methyl, AIBN is azobisisobutyronitrile, NMR is nuclear magnetic resonance. Mw is a weight average molecular weight, Mn is a number average molecular weight, both as 25 measured by gel permeation chromatography (GPC) versus polystyrene standards, and Mw/Mn is a molecular weight dispersity. 

A 100-mL flask was charged with 13. 0 g of acetoxystyrene, 4.1 g ofa monomerof formula (20) below, and 20 g of toluene as a solvent. The reactor was cooled to - 70° C. in a nitrogen atmosphere, whereupon vacuum deaeration and nitrogen flow were repeated three times. The reactor was warmed up to room temperature, 1.4 g of AIBN was added as a polymer› ization initiator, and the reactor was further heated to 55° C., at which reaction was effected for 40 hours. 

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The reaction solution was concentrated to a ‰ volume and precipitated in 5.0 L of methanol. The resulting white solids were filtered and vacuum dried at 40° C., obtaining 15 .5 g of a white polymer. The polymer was dissolved in a mixture of 0.4 L methanol and 0.5 L tetrahydrofuran again, to which 140 g of triethylamine and 30 g of water were added. The reactor was heated to 60° C., allowing deprotection reaction to occur. The reaction solution was neutralized with acetic acid, con› centrated, dissolved in 0.5 L ofacetone, and precipitated in 10 L of water. Filtration and drying in the same way as above gave 12.4 g of a white polymer. 

The polymer was analyzed by $^{13}$C-NMR, $^{1}$H-NMR and GPC, with the analytical results shown below. 

## EXAMPLES 

## Synthesis Example 1 

Copolymer Compositional Ratio 

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Mw=6,500 Mw/Mn=l.65 This polymer is designated Poly-I. 

Synthesis was carried out by the same procedure as in Synthesis Example 1 aside from using 4.6 g of a monomer of formula (21) instead of the monomer of formula (20). There was obtained 12.4 g of a white polymer. 

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The polymer was analyzed by $^{13}$C-NMR, $^{1}$H-NMR and GPC, with the analytical results shown below. 

Copolymer Compositional Ratio 

<img src='content_image/902284.jpg'>

Mw=7,400 Mw/Mn=l.76 This polymer is designated Poly-2. 

Synthesis was carried out by the same procedure as in Synthesis Example 2 except that 2.4 g of indene was further added. There was obtained 13.0 g of a white polymer. 

The polymer was analyzed by $^{13}$C-NMR, $^{1}$H-NMR and GPC, with the analytical results shown below. 

## Synthesis Example 2 

## Synthesis Example 3 

