Bipolar semiconductor device and manufacturing method

A planar IGBT, comprising in a vertical cross-section:

• an emitter electrode;
• a collector electrode arranged below the emitter electrode;
• two p-type body regions;
• an insulated gate electrode arranged above the body regions;
• two p-type body contact regions each of which electrically connects a respective body region with the emitter electrode,
• an n-type drift region forming respective pn-junctions with the body regions;
• a p-type collector region arranged on the collector electrode;
• and
• two embedded structures arranged above the collector region and selected from a group consisting of a porous semiconductor region, a cavity, an insulating region, and a semiconductor region comprising additional scattering centers for holes;
• and
• where each of the embedded structures are arranged below a respective body contact region such that each of the two embedded structures overlaps, in a horizontal projection, with the respective body contact region.

A trench IGBT, comprising in a vertical cross-section:

• an emitter electrode;
• a p-type body region;
• an n-type drift region forming a pn-junction with the body region;
• an insulated gate electrode arranged in a vertical trench extending through the p-type body region into the drift region;
• a p-type body contact region electrically connecting the body region with the emitter electrode,
• a p-type collector region arranged below the drift region;
• and
• an embedded structure arranged above the collector region and selected from a group consisting of a porous semiconductor region, a cavity, and a semiconductor region comprising additional scattering centers for holes,
• the embedded structure being arranged below the body contact region such that the embedded structure and the body contact region overlap in a horizontal projection.

A method for forming a bipolar semiconductor device, comprising:

• providing a semiconductor substrate comprising a main horizontal surface, an n-type first semiconductor region, a p-type second semiconductor region and a pn-junction;
• forming a p-type third semiconductor region comprising a third doping concentration such that the first semiconductor region and the third semiconductor region form a further pn-junction above the pn-junction;
• forming an embedded structure above the pn-junction, the embedded structure comprising a hole mobility which is lower than the hole mobility of adjoining semiconductor regions;
• and
• forming a p-type fourth semiconductor region comprising a fourth doping concentration which is higher than the third doping concentration in electrical contact with the p-type third semiconductor region such that the fourth semiconductor region and the embedded structure are arranged in two vertical cross-sections which are orthogonal to each other and to the main surface.