Silicon carbide semiconductor device and method for manufacturing the same

A silicon carbide semiconductor device comprising:

• a drift layer of a first conductivity type above a silicon carbide substrate of the first conductivity type;
• a current spreading layer of the first conductivity type on a top surface of the drift layer, having a higher impurity concentration than the drift layer;
• a base region of a second conductivity type on a top surface of the current spreading layer;
• a gate-bottom protection region of the second conductivity type located in the current spreading layer;
• a base-bottom embedded region of the second conductivity type located in the current spreading layer, separated from the gate-bottom protection region to be in contact with a bottom surface of the base region;
• an insulated-gate electrode structure in a trench penetrating the base region to reach the gate-bottom protection region;
• and
• a lower recombination region in a lower portion of the drift layer and selectively below the base-bottom embedded region, including crystal defects configured to recombine minority carriers injected into the drift layer, and having recombination centers provided with hydrogen or helium as the crystal defects, wherein
• a space between the lower recombination region and another lower recombination region adjacent to the lower recombination region is aligned so as to face the gate-bottom protection region, and
• a width of the space is larger than a width of the gate-bottom protection region, and in a plan view, an end of the lower recombination region is positioned on a side of the gate-bottom protection region between the base-bottom embedded region and the gate-bottom protection region.

A silicon carbide semiconductor device comprising:

• a drift layer of a first conductivity type above a silicon carbide substrate of the first conductivity type;
• a current spreading layer of the first conductivity type on a top surface of the drift layer, having a higher impurity concentration than the drift layer;
• a base region of a second conductivity type on a top surface of the current spreading layer;
• a gate-bottom protection region of the second conductivity type located in the current spreading layer;
• a base-bottom embedded region of the second conductivity type located in the current spreading layer, separated from the gate-bottom protection region to be in contact with a bottom surface of the base region;
• an insulated-gate electrode structure in a trench penetrating the base region to reach the gate-bottom protection region;
• and
• a lower recombination region in a lower portion of the drift layer, including crystal defects configured to recombine minority carriers injected into the drift layer, wherein the lower recombination region has an area density of the crystal defects in a range of 5×1011 cm−2 or more and 2×1012 cm−2 or less, and a thickness in range of 0.5 μm or more and 1.0 μm or less.

A method for manufacturing a silicon carbide semiconductor device comprising:

• forming an element structure in an active area of a silicon carbide substrate of a first conductivity type, the element structure including,
• a drift layer of the first conductivity type epitaxially grown on the silicon carbide substrate,
• a current spreading layer of the first conductivity type on a top surface of the drift layer, having a higher impurity concentration than the drift layer,
• a base region of a second conductivity type on a top surface of the current spreading layer,
• a gate-bottom protection region of the second conductivity type located in the current spreading layer,
• a base-bottom embedded region of the second conductivity type located in the current spreading layer, separated from the gate-bottom protection region to be in contact with a bottom surface of the base region, and
• an insulated-gate electrode structure in a trench penetrating the base region to reach the gate-bottom protection region,
• polishing a bottom surface of the silicon carbide substrate, after forming the element structure;
• and
• selectively implanting hydrogen ions or helium ions into a lower portion of the drift layer from the polished bottom surface of the silicon carbide substrate to selectively form a lower recombination region, which includes crystal defects for recombining minority carriers, in the lower portion of the drift layer;
• and
• selectively implanting ions into an upper portion of the drift layer from the polished bottom surface of the silicon carbide substrate to selectively form an upper recombination region on a bottom surface of the base-bottom embedded region so as to be in direct contact with the bottom surface of the base-bottom embedded region without an intervening layer between an upper surface of the upper recombination region and the bottom surface of the base-bottom embedded region, the upper recombination region including crystal defects for recombining minority carriers.