US 12,426,290 B2
Semiconductor device and method for manufacturing the same
Katsumi Nakamura, Tokyo (JP)
Assigned to Mitsubishi Electric Corporation, Tokyo (JP)
Filed by Mitsubishi Electric Corporation, Tokyo (JP)
Filed on Apr. 3, 2024, as Appl. No. 18/625,604.
Application 18/625,604 is a division of application No. 17/457,320, filed on Dec. 2, 2021, granted, now 12,009,413.
Claims priority of application No. 2021-036331 (JP), filed on Mar. 8, 2021.
Prior Publication US 2024/0274699 A1, Aug. 15, 2024
Int. Cl. H10D 12/00 (2025.01); H10D 12/01 (2025.01)
CPC H10D 12/481 (2025.01) [H10D 12/01 (2025.01)] 4 Claims
OG exemplary drawing
 
1. A method for manufacturing a semiconductor device, the method comprising:
a step of preparing a semiconductor substrate, the semiconductor substrate including:
a first main surface,
a second main surface opposite to the first main surface,
a drift layer of a first conductivity type provided between the first main surface and the second main surface, and
a buffer layer of a first conductivity type provided on a second main surface side with respect to the drift layer and having a larger number of atoms of impurities per unit volume than the drift layer; and
a step of implanting respective first impurities and second impurities from the second main surface, and forming, on the second main surface side with respect to the buffer layer, a dual-layer semiconductor layer comprising a first semiconductor layer and a second semiconductor layer which are arranged in this order in a direction from the second main surface toward the first main surface,
wherein the step of forming the first semiconductor layer and the second semiconductor layer includes:
implanting the second impurities for forming the second semiconductor layer from the second main surface;
implanting the first impurities for forming the first semiconductor layer from the second main surface into a region shallower than the second semiconductor layer so that the number of atoms of the first impurities per unit volume is smaller than the number of atoms of the second impurities per unit volume in the second semiconductor layer; and
diffusing the first impurities and the second impurities into the semiconductor substrate by laser annealing,
the first impurities and the second impurities have conductivity types identical to each other, and
the dual-layer semiconductor layer has two consecutive peaks for the number of atoms of impurities per unit volume from the second main surface side of the dual-layer semiconductor layer toward the first main surface side of the dual-layer semiconductor layer, each of the first semiconductor layer and the second semiconductor layer having one of the two peaks.