Mitsubishi Denki Kabushiki Kaisha

Takeshi Kuragaki

Kazuhiko Sato

Katsuya Kosaki

Kenichi Harada

Osamu Ishihara

Akiyoshi Kudo

An apparatus for adhering a wafer to a supporting substrate includes a chamber having a lower part including a wafer stage having a planar surface on which a wafer having a surface covered with an adhesive is mounted with the adhesive facing upward, an upper part for covering the planar surface of the wafer stage, an evacuation port for evacuating the chamber, and a pressure plate opposite a supporting substrate disposed on the wafer and movable downward so that the pressure plate presses the supporting substrate toward the wafer. At least three gauge blocks having a thickness larger than that of the wafer are disposed on the planar surface of the wafer stage, surrounding a wafer and sandwiched between the supporting substrate and the planar surface when the supporting substrate is pressed toward the wafer. Heaters for heating the wafer and the supporting substrate are embedded in the lower and upper parts of the chamber. A gap between the wafer and the supporting substrate and filled with the adhesive is uniform within the area of the wafer surface.

Apparatus for adhering wafer to supporting substrate

A method of fabricating a thin film piezoelectric device includes preparing a semiconductor substrate having a surface; forming an etch stopping layer having an etching rate on the surface of the semiconductor substrate; forming a first semiconductor layer having an etching rate higher than the etching rate of the etch stopping layer on the etch stopping layer; forming a first electrode on a region of the first semiconductor layer; forming a piezoelectric film on the first electrode; forming a second electrode on the piezoelectric film; and etching a portion of the first semiconductor layer where the first electrode, the piezoelectric film, and the second electrode overlap, from the surface of the first semiconductor layer, selectively with respect to the etch stopping layer, thereby forming a cavity in the first semiconductor layer. Even when a compound semiconductor is employed as the substrate, the etching forming a cavity is stopped at the etch stopping layer in the direction perpendicular to the surface of the first semiconductor layer so that a cavity having a uniform depth is produced with high controllability.

Method of fabricating thin film piezoelectric device

A method for producing a semiconductor device includes growing a collector layer, a base layer, and an emitter layer on a substrate; forming an emitter electrode, a tungsten film, and a silicon film services as an etching stopper on a prescribed region of the emitter layer; etching the emitter layer using the above-described films as a mask to expose the base layer; forming side walls on opposite side surfaces of the silicon film, tungsten film, emitter electrode, and emitter layer; forming a zinc oxide layer serving as an impurity diffusion source on the base layer and performing a diffusion to produce high purity concentration regions in the base layer; removing the zinc oxide layer by wet etching using hydrofluoric acid as an etchant; depositing a base metal on the base layer and removing an unnecessary portion of the base metal by ion milling for form base electrodes; selectively removing the silicon film; and forming an electrode in contact with the tungsten film. Since the silicon film is not etched by hydrofluoric acid when the zinc oxide layer is removed, the emitter electrode is not adversely affected by the ion milling in removing the base metal, resulting in an HBT with a reliable emitter electrode.

Growing community of inventors

Tokyo, Japan

Takeshi Kuragaki