	US 12,191,359 B2
	Method of manufacturing silicon carbide semiconductor device and silicon carbide semiconductor device
Yu Kurioka, Matsumoto (JP)
Assigned to FUJI ELECTRIC CO., LTD., Kawasaki (JP)
Filed by FUJI ELECTRIC CO., LTD., Kawasaki (JP)
Filed on May 31, 2022, as Appl. No. 17/829,065.
Claims priority of application No. 2021-117038 (JP), filed on Jul. 15, 2021.
Prior Publication US 2023/0018824 A1, Jan. 19, 2023
Int. Cl. H01L 29/78 (2006.01); H01L 21/336 (2006.01); H01L 29/16 (2006.01); H01L 29/36 (2006.01); H01L 29/66 (2006.01)

CPC H01L 29/36 (2013.01) [H01L 29/1608 (2013.01); H01L 29/66068 (2013.01); H01L 29/7813 (2013.01)]

5 Claims

1. A method of manufacturing a silicon carbide semiconductor device, the method comprising:

preparing a silicon carbide semiconductor substrate of a first conductivity type, the silicon carbide semiconductor substrate having a first surface and a second surface that are opposite to each other;

forming a first semiconductor layer of the first conductivity type on the first surface of the silicon carbide semiconductor substrate, the first semiconductor layer having an impurity concentration that is lower than an impurity concentration of the silicon carbide semiconductor substrate, the first semiconductor layer having a first surface and a second surface that are opposite to each other, the second surface of the first semiconductor layer facing the silicon carbide semiconductor substrate;

forming a second semiconductor layer of a second conductivity type on the first surface of the first semiconductor layer, the second semiconductor layer having a first surface and a second surface that are opposite to each other, the second surface of the second semiconductor layer facing the silicon carbide semiconductor substrate;

selectively forming a plurality of first semiconductor regions of the first conductivity type in the second semiconductor layer, at the first surface of the second semiconductor layer;

forming a plurality of trenches that penetrate through the first semiconductor regions and the second semiconductor layer, and reach the first semiconductor layer;

forming a gate insulating film in the trenches, along sidewalls and bottoms of the trenches;

forming a plurality of gate electrodes on the gate insulating film in the trenches;

forming a first electrode on surfaces of the first semiconductor regions and the first surface of the second semiconductor layer; and

forming a second electrode on the second surface of the silicon carbide semiconductor substrate, wherein

forming the gate insulating film includes forming the gate insulating film using a nitriding heat treatment that has a first stage and a second stage, by

performing the first stage of the nitriding heat treatment by a first gas containing oxygen and nitrogen,

depositing an oxide film after performing the first stage of the nitriding heat treatment, and

performing the second stage of the nitriding heat treatment by a second gas containing nitric oxide and nitrogen, after depositing the oxide film;

an amount of the nitrogen at a treatment starting point of the first stage of the nitriding heat treatment is greater than an amount of the nitrogen at a treatment starting point of the second stage of the nitriding heat treatment; and

an amount of the nitrogen at a treatment ending point of the second stage of the nitriding heat treatment is greater than an amount of the nitrogen at a treatment ending point of the first stage of the nitriding heat treatment.

4. A silicon carbide semiconductor device, comprising:

a silicon carbide semiconductor substrate of a first conductivity type, the silicon carbide semiconductor substrate having a first surface and a second surface that are opposite to each other;

a first semiconductor layer of the first conductivity type, provided on the first surface of the silicon carbide semiconductor substrate, the first semiconductor layer having an impurity concentration that is lower than an impurity concentration of the silicon carbide semiconductor substrate, the first semiconductor layer having a first surface and a second surface that are opposite to each other, the second surface of the first semiconductor layer facing the silicon carbide semiconductor substrate;

a second semiconductor layer of a second conductivity type, provided on the first surface of the first semiconductor layer, the second semiconductor layer having a first surface and a second surface that are opposite to each other, the second surface of the second semiconductor layer facing the silicon carbide semiconductor substrate;

a plurality of first semiconductor regions of the first conductivity type, selectively provided in the second semiconductor layer, at the first surface of the second semiconductor layer;

a plurality of trenches that penetrate through the first semiconductor regions and the second semiconductor layer, and reach the first semiconductor layer;

a gate insulating film provided in the trenches, along bottoms and sidewalls of the trenches;

a plurality of gate electrodes provided on the gate insulating film in the trenches;

a first electrode provided on surfaces of the first semiconductor regions and the first surface of the second semiconductor layer; and

a second electrode provided on the second surface of silicon carbide semiconductor substrate, wherein

the silicon carbide semiconductor device has a peak nitrogen concentration at interfaces between the gate insulating film and the first semiconductor regions and between the gate insulating film and the second semiconductor layer, in a range of 1×10²⁰atoms/cm³to 1×10²¹atoms/cm³.