Sharp Kabushiki Kaisha Corporation

Kazuo Sugimoto

Satoshi Morishita

Kouichiro Adachi

Shinya Takagi

Masaharu Yoshikawa

Masuo Kamitaka

Hiroyuki Yoshida

A method for diagnosing a function of plasma etching apparatuses and a method for estimating selectivity in an actual etching process in fabrication of semiconductor devices involves generating plasma of a gas mixture including halogen and oxygen in a predetermined condition. An intensity of one of first emissions from the plasma at a first wavelength and an intensity of one of second emissions from the plasma at a second wavelength is measured A ratio of the intensity of the one of first emissions to that of the one of second emissions is obtained. The obtained emission intensity ratio is compared with an emission intensity ratio which is previously measured for a plasma condition when the plasma etching apparatus operates normally.

Dry etching method

Silicon material layers formed on an oxide underlayer are attached using a plasma including a gas mixture of a halogen and oxygen. Intensities of first emissions from the plasma at a first wavelength and second emissions from the plasma at a second wavelength are measured. A ratio of the first emissions intensity to the second emissions intensity is determined. The selectivity of silicon layers to oxide underlayers is measured for various conditions of the plasma under which the emissions intensity ratio is obtained. A correlation between the emissions intensity ratio and the selectivity is then established for various etching parameters. A plasma condition to obtain a desired selectivity may then be appropriately set using the established correlation.

A refrigerator comprising a refrigeration cycle which comprises a compressor, condenser, first capillary tube and first cooler connected into a loop, and a quick freezing refrigerant circuit connected in parallel with the first cooler and comprising a second capillary tube and a second cooler connected in series therewith. The refrigerant is passed through the first cooler for usual operation, or alternatively through the quick freezing circuit for quick freezing. During quick freezing, the first cooler is held out of operation, and the refrigerant has its pressure reduced in two steps by the first and second capillary tubes and is evaporated in the second cooler only, giving a low temperature effective for quick freezing. During usual operation, no refrigerant flows into the second cooler, which therefore remains free of frosting. The frost deposited on the second cooler during quick freezing disappears during the usual operation. Thus, the second cooler is substantially free from frost.

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Tenri, Japan

Kazuo Sugimoto