Superjunction structures for power devices and methods of manufacture

A power device comprising:

• an active region;
• a termination region surrounding the active region;
• a plurality of pillars of a first conductivity type;
• and
• a plurality of pillars of a second conductivity type, the plurality of pillars of the first conductivity type and the plurality of pillars of the second conductivity type being alternately arranged in the active region and the termination region, a pillar of the plurality of pillars of the second conductivity type including:
• a first implant region of the second conductivity type;
• a second implant region of the second conductivity type disposed above, and vertically aligned with the first implant region of the second conductivity type,
• a trench;
• and
• a semiconductor material of the second conductivity type disposed in the trench, the trench being disposed above, and vertically aligned with the second implant region of the second conductivity type,
• the plurality of pillars of the second conductivity type including a pillar in the active region having a number of implant regions of the second conductivity type that is less than a number of implant regions of the second conductivity type of a pillar of the plurality of pillars of the second conductivity type in the termination region.

A method for forming a power device including pillars of alternating conductivity type, the method comprising:

• forming a semiconductor region on a substrate, the semiconductor region including a plurality of epitaxial layers of a first conductivity type;
• defining an active region of the power device in the semiconductor region;
• defining a termination region of the power device in the semiconductor region, the termination region surrounding the active region;
• forming a plurality of pillars of a second conductivity type in the active region and the termination region, the forming a pillar of the plurality of pillars of the second conductivity type including:
• forming a plurality of implant regions of the second conductivity type, each of the plurality of implant regions of the second conductivity type being disposed in at least one epitaxial layer of the plurality of epitaxial layers of the first conductivity type;
• forming a trench extending into an upper-most epitaxial layer of the plurality of epitaxial layers;
• and
• forming a semiconductor material of the second conductivity type in the trench,
• the plurality of implant regions of the second conductivity type and the trench being vertically aligned such that the semiconductor material of the second conductivity type and the plurality of implant regions of the second conductivity type define a pillar of the second conductivity type, the plurality of pillars of the second conductivity type in the active region including a pillar having a number of implant regions of the second conductivity type that is less than a number of implant regions of the second conductivity type of a pillar of the plurality of pillars of the second conductivity type in the termination region,
• the forming the plurality of pillars of the second conductivity type defining a plurality of pillars of the first conductivity type in the active region and the termination region, the plurality of pillars of the first conductivity including portions of the plurality of epitaxial layers disposed between the plurality of pillars of the second conductivity type.

A method for forming a power device including pillars of alternating conductivity type, the method comprising:

• forming a semiconductor region on a substrate, the semiconductor region including a plurality of epitaxial layers of a first conductivity type;
• defining an active region of the power device in the semiconductor region;
• defining a termination region of the power device in the semiconductor region, the termination region surrounding the active region;
• forming a plurality of pillars of a second conductivity type in the active region and the termination region, the forming a pillar of the plurality of pillars of the second conductivity type including:
• forming a plurality of implant regions of the second conductivity type, each of the plurality of implant regions of the second conductivity type being disposed in at least one epitaxial layer of the plurality of epitaxial layers of the first conductivity type;
• forming a trench extending into an upper-most epitaxial layer of the plurality of epitaxial layers;
• and
• forming a semiconductor material of the second conductivity type in the trench,
• the plurality of implant regions of the second conductivity type and the trench being vertically aligned such that the semiconductor material of the second conductivity type and the plurality of implant regions of the second conductivity type define a pillar of the second conductivity type, the plurality of pillars of the second conductivity type in the active region including a pillar having a lateral width that is greater than a lateral width of a pillar of the plurality of pillars of the second conductivity type in the termination region,
• the forming the plurality of pillars of the second conductivity type defining a plurality of pillars of the first conductivity type in the active region and the termination region, the plurality of pillars of the first conductivity including portions of the plurality of epitaxial layers disposed between the plurality of pillars of the second conductivity type.