Method of manufacturing semiconductor device including insulated gate bipolar transistor and diode

A method of manufacturing a semiconductor device including an IGBT forming region and a diode forming region, the semiconductor device comprising:

• a first conductivity type layer of a first conductivity type disposed in the diode forming region;
• a collector layer of a second conductivity type disposed in the IGBT forming region;
• a drift layer of the first conductivity type disposed above the first conductivity type layer and the collector layer;
• a base region of the second conductivity type disposed above the drift layer;
• a plurality of trenches penetrating the base region into the drift layer so as to divide the base region into a plurality of portions;
• an emitter region of the first conductivity type disposed in one of the plurality of portions of the base region divided by the plurality of trenches and being in contact with a sidewall of one of the plurality of trenches;
• a gate insulating layer disposed on a surface of the plurality of trenches;
• a gate electrode disposed on the gate insulating layer in the plurality of the trenches;
• a first electrode electrically coupled with the base region and the emitter region;
• and
• a second electrode disposed on an opposite side of the collector layer from the drift layer, wherein:
• in the IGBT forming region, the collector layer, the drift layer, the base region, the emitter region, and the gate electrode provide an IGBT;
• in the diode forming region, the first conductivity type layer and the drift layer have a PN junction with the base region so as to provide the diode;
• and
• the IGBT and the diode are integrated,
• the method comprising:
• preparing a semiconductor substrate of the first conductivity type having first and second surfaces opposing each other;
• implanting second conductivity type impurities for forming the collector layer to the second surface of the semiconductor substrate using a mask that has an opening at a portion where the collector layer will be formed;
• forming an oxide layer by enhanced-oxidizing the collector layer;
• implanting first conductivity type impurities for forming the first conductivity type layer to the second surface of the semiconductor substrate using the oxide layer as a mask;
• attaching a support base to a side of the semiconductor substrate where the oxide layer and the first conductivity type layer are formed;
• reducing a thickness of the semiconductor substrate from the first surface in a state where the semiconductor substrate is attached with the support base;
• and
• forming an element part including the base region, the emitter region, the plurality of trenches, the gate insulating layer, the gate electrode, and the first electrode on the first surface of the semiconductor substrate after reducing the thickness of the semiconductor substrate, wherein:
• the implanting the second conductivity type impurities for forming the collector layer is performed using a silicon nitride layer as the mask;
• and
• the forming the oxide layer is performed by enhanced-oxidizing the collector layer using the silicon nitride layer as a mask so that the oxide layer is not formed at a portion covered with the silicon nitride layer.