Central Research Institute of Electric Power Industry

The Kansai Electric Power Co., Inc.

Ryosuke Ishii

Hidekazu Tsuchida

Koji Nakayama

Yoshitaka Sugawara

Isaho Kamata

Toshiyuki Miyanagi

Tomonori Nakamura

Masahiro Nagano

In a bipolar semiconductor device such that electrons and holes are recombined in a silicon carbide epitaxial film grown from the surface of a silicon carbide single crystal substrate at the time of on-state forward bias operation; an on-state forward voltage increased in a silicon carbide bipolar semiconductor device is recovered by shrinking the stacking fault area enlarged by on-state forward bias operation. In a method of this invention, the bipolar semiconductor device in which the stacking fault area enlarged and the on-state forward voltage has been increased by on-state forward bias operation, is heated at a temperature of higher than 350&#xb0; C.

Method for recovering an on-state forward voltage and, shrinking stacking faults in bipolar semiconductor devices, and the bipolar semiconductor devices

In a bipolar silicon carbide semiconductor device in which an electron and a hole recombine with each other during current passage within a silicon carbide epitaxial film grown from a surface of a silicon carbide single crystal substrate, an object described herein is the reduction of defects which are the nuclei of a stacking fault which is expanded by current passage, thereby suppressing the increase of the forward voltage of the bipolar silicon carbide semiconductor device. In a method for producing a bipolar silicon carbide semiconductor device, the device is subjected to a thermal treatment at a temperature of 300&#xb0; C. or higher in the final step of production. Preferably, the above-mentioned thermal treatment is carried out after the formation of electrodes and then the resulting bipolar silicon carbide semiconductor device is mounted in a package.

Process for producing silicon carbide semiconductor device

Bipolar semiconductor devices have a Zener voltage controlled very precisely in a wide range of Zener voltages (for example, from 10 to 500 V). A bipolar semiconductor device has a mesa structure and includes a silicon carbide single crystal substrate of a first conductivity type, a silicon carbide conductive layer of a first conductivity type, a highly doped layer of a second conductivity type and a silicon carbide conductive layer of a second conductivity type which substrate and conductive layers are laminated in the order named.

Bipolar semiconductor device, method for producing the same, and method for controlling Zener voltage

In a SiC bipolar semiconductor device with a mesa structure having a SiC drift layer of a first conductive type and a SiC carrier injection layer of a second conductive type that are SiC epitaxial layers grown from a surface of a SiC single crystal substrate, the formation of stacking faults and the expansion of the area thereof are prevented and thereby the increase in forward voltage is prevented. Further, a characteristic of withstand voltage in a reverse biasing is improved. An forward-operation degradation preventing layer is formed on a mesa wall or on a mesa wall and a mesa periphery to separate spatially the surface of the mesa wall from a pn-junction interface. In one embodiment, the forward-operation degradation preventing layer is composed of a silicon carbide low resistance layer of a second conductive type that is equipotential during the application of a reverse voltage. In another embodiment, the forward-operation degradation preventing layer is composed of a silicon carbide conductive layer of a second conductive type, and a metal layer that is equipotential during the application of a reverse voltage is formed on a surface of the silicon carbide conductive layer. In still another embodiment, the forward-operation degradation preventing layer is composed of a high resistance amorphous layer.

Silicon carbide bipolar semiconductor device

A silicon carbide Zener diode is a bipolar semiconductor device that has a mesa structure and includes a silicon carbide single crystal substrate of a first conductivity type, formed thereon, a silicon carbide conductive layer of a first conductivity type, and a silicon carbide conductive layer of a second conductivity type formed on the silicon carbide conductive layer of a first conductivity type, wherein a depletion layer that is formed under reverse bias at a junction between the silicon carbide conductive layer of a first conductivity type and the silicon carbide conductive layer of a second conductivity type does not reach a mesa corner formed in the silicon carbide conductive layer of a first conductivity type.

Growing community of inventors

Osaka, Japan

Ryosuke Ishii