Power semiconductor device with soft switching characteristic and manufacturing method for same
View Patent ↗After introducing oxygen into an N − type FZ wafer serving as an N − type first semiconductor layer, a P type second semiconductor layer and an anode are formed on a surface of the FZ wafer. The FZ wafer is irradiated with protons from the side of the anode, introducing crystal defects into the FZ wafer. By performing heat treatment to recover the crystal defects in the FZ wafer, the net doping concentration of a portion within the first semiconductor layer is made higher than the initial net doping concentration of the FZ wafer, and a desired broad buffer structure is formed. Accordingly, a semiconductor device with fast operation and low losses, and having soft switching characteristics, can be manufactured inexpensively using FZ bulk wafers, with good controllability and yields.
1. A manufacturing method for the semiconductor device comprising:
introducing oxygen into a semiconductor substrate of a first conduction type which serves as a first semiconductor layer of a semiconductor device;
irradiating a first main face or second main face of the semiconductor substrate with protons with a proton dose of 1×10 11 atoms/cm 2 or higher and 1×10 14 atoms/cm 2 or lower and introducing crystal defects into the first semiconductor layer; and
performing heat treatment to recover crystal defects introduced into the first semiconductor layer, thereby causing a net doping concentration of a portion within the first semiconductor layer to be higher than the initial net doping concentration of the semiconductor substrate.
2. The manufacturing method for a semiconductor device according to claim 1 , further comprising:
after introducing oxygen into the semiconductor substrate, prior to charged particle irradiation, forming a second semiconductor layer of a second conduction type having higher concentration than the semiconductor substrate on a side of the first main face of the semiconductor substrate;
grinding the second main face of the semiconductor substrate after recovery of crystal defects by the heat treatment; and
forming a third semiconductor layer of the first conduction type having higher concentration than the first semiconductor layer on the ground second main face.
3. The manufacturing method for a semiconductor device according to claim 1 , further comprising:
introducing first conduction type impurities together with oxygen at the time of introduction of oxygen into the semiconductor substrate, and forming a third semiconductor layer of the first conduction type with higher concentration than the semiconductor substrate over a second surface of the semiconductor substrate; and
after the introduction of oxygen and the first conduction type impurities into the semiconductor substrate, and before charged particle irradiation, forming a second semiconductor layer of the second conduction type, with higher concentration than the first semiconductor layer, on a first surface of the first semiconductor layer into which the first conduction type impurities have not been introduced.
4. The manufacturing method for a semiconductor device according to any one of claim 1 , 2 or 3 , characterized in that, after introduction of crystal defects by charged particle irradiation, the heat treatment is performed at a temperature of 250° C. or higher and 500° C. or lower.
5. The manufacturing method for a semiconductor device according to any one of claim 1 , 2 or 3 , characterized in that, after introduction of crystal defects by charged particle irradiation, the heat treatment is performed at a temperature of 300° C. or higher and 450° C. or lower.
6. The manufacturing method for a semiconductor device according to any one claim 1 , 2 or 3 , characterized in that, after introduction of crystal defects by charged particle irradiation, the heat treatment is performed at a temperature of 350° C. or higher and 420° C. or lower.
7. The manufacturing method for a semiconductor device according to any one of claim 1 , 2 or 3 , wherein the concentration of the oxygen atoms is 1.0×10 16 (atoms/cm 3 ) or higher.
8. The manufacturing method for a semiconductor device according to claim 1 , wherein the concentration of the oxygen atoms is 1.0×10 16 (atoms/cm 3 ) and 1×10 18 atoms/cm 3 or lower.
9. A semiconductor device comprising:
a first semiconductor layer of a first conduction type;
a second semiconductor layer of a second conduction type having a higher concentration than the first semiconductor layer, which is formed on a side of a first main face of the first semiconductor layer; and
a third semiconductor layer of the first conduction type having a higher concentration than the first semiconductor layer, which is formed on a side of a second main face of the first semiconductor layer;
wherein there exists at least one location in the first semiconductor layer at which an impurity concentration in the first semiconductor layer is a maximum, and the impurity concentration in the first semiconductor layer decreases from the location of the maximum impurity concentration toward both the second semiconductor layer and the third semiconductor layer, and
wherein at least the location of the maximum impurity concentration in the first semiconductor layer comprises oxygen atoms and hydrogen atoms, and wherein the concentration of the oxygen atoms is 1.0×10 16 (atoms/cm 3 ) or higher.
10. A semiconductor device according to claim 9 , wherein the concentration of oxygen is 1×10 16 atoms/cm 3 or higher and 1×10 18 atoms/cm 3 or lower.