| 摘要 |
PURPOSE:To remarkably improve the rate of dry etching of chromium boride on a transparent glass substrate by using a gaseous mixture of carbon tetrachloride with chloroform and oxygen as an etching gas. CONSTITUTION:When a photomask blank formed by laminating a chromium film contg. boron on a transparent glass substrate is dry etched with gas plasma, a gaseous mixture of carbon tetrachloride with chloroform and oxygen is used as an etching gas. The composition of the gaseous mixture is composed of, by volume, 5-17% carbon tetrachloride, 17-33% chloroform and 50-72% oxygen. The chromium film contg. boron may further contain nitrogen, oxygen and carbon.
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