Kabushiki Kaisha Toshiba

Yoshinari Uetake

Tsuneo Ogura

Yoshio Yokota

Kazuo Watanuki

Mitsuhiko Kitagawa

Kazunobu Nishitani

Hiromichi Ohashi

Hiroshi Okamura

Hideo Matsuda

Takashi Fujiwara

Yasunori Usui

Shinjiro Kojima

Masami Iwasaki

Mituhiko Kitagawa

Youichi Araki

Phosphorus is doped into one of the major surfaces of an n-type silicon semiconductor substrate, and boron is doped into the other major surface. Thereafter, the structure is diffused into the surface regions of the substrate at a high temperature and for a long time, so that an n-buffer layer is formed in the first major surface, and a p-base layer is formed in the second major surface. Impurity of n-type is diffused into the p-base layer, to form an n-emitter layer. Impurity of p-type is diffused into the n-buffer layer, to selectively form p-emitter layer. Further, n-type impurity is diffused into the n-buffer layer, to form n-type anode short layer.

Method of making a semiconductor device of a high withstand voltage

A semiconductor switching device includes a high resistance first base layer of n-type formed on a first emitter layer of p-type through a low resistance buffer layer of n.sup.+ -type, second base layer of p-type formed on the first base layer, second emitter layers of n.sup.+ -type separately formed on the second base layer, anode and cathode main electrodes formed in contact with the first and second emitter layers, and a gate electrode formed in contact with the second base layer. Part of the low resistance buffer layer is exposed to the surface of the first emitter layer and is made contact with the anode main electrode to constitute a shorting portion. The width of the shorting portion is set smaller than one tenth of that of the second emitter layer in a longitudinal direction.

Semiconductor switching device with anode shortening structure

A press-contact flat type semiconductor device is disclosed which, without alloy-bonding a silicon pellet to a molybdenum or tungsten disc, assures a uniform press contact because a warp on the silicon pellet is largely reduced in comparison with a conventional device. A silver sheet is omitted between an anode electrode post and the silicon pellet to absorb a warp on the pellet. It is only necessary to insert a molybdenum or tungsten disc there, instead, which is thinner than a counterpart of the conventional device. Between the cathode electrode of the silicon pellet and a cathode electrode post use is made of, in the place of a conventional molybdenum foil and silver cap, an annealed soft copper cap of better malleability and, in the place of conventional molybdenum disc, an inexpensive hard copper sheet of adequate thickness and rigidity, not annealed, which can assure uniform press contact with the cathode electrode surface which oppositely confronts a gate lead connection circuit of a cathode electrode post. Since the silicon pellet is not alloy-bonded to the molybdenum or tungsten disc, it is simple and easy to form a bevelled structure, and to perform a silicone insulating rubber coating operation, so as to obtain the anode-to-cathode withstand voltage of the silicon pellet. Thus an inexpensive press-contact flat type semiconductor device of a long life can be provided which ensures more uniform press contact than a conventional semiconductor device.

Press-contact flat type semiconductor device

In a power semiconductor device according to the present invention, a sheet, formed of a soft metal such as Ag, is provided on that portion of a pressing control electrode which is brought into contact with an Al gate electrode of a pellet. By means of this sheet, it is possible both to apply a strong pressing power to the Al gate electrode and to reduce the contact resistance between the two electrode. Since an excessive amount of heat is not produced on account of the contact resistance, the semiconductor device can be protected against being damaged.

Power semiconductor device

A mesa type power semiconductor device comprising a mesa groove disposed on the bottom thereof with separated gate electrodes leaving the central portion of the groove bottom free from a gate electrode. This construction is effective in preventing occurrence of an insulator breakdown between a cathode and a gate electrode.

Power semiconductor device with mesa type structure

Growing community of inventors

Sagamihara, Japan

Yoshinari Uetake