Power semiconductor rectifier having broad buffer structure and method of manufacturing thereof
View Patent ↗Impurity concentration (N d (X)) in an n-drift layer in a diode is at a maximum at a position at a distance Xp from an anode electrode in a direction from the anode electrode to a cathode electrode, and gradually decreases from the position toward each of the anode electrode and the cathode electrode. A ratio of the peak impurity concentration N p to an averaged impurity concentration N dm in the n-drift layer is in the range of 1 to 5. This provides a diode and a manufacturing method thereof by which oscillations in voltage and current at reverse recovery are inhibited to achieve enhancement both in high speed and low-loss characteristics and in soft recovery characteristics.
1. A method of manufacturing a semiconductor device comprising the steps of:
providing a semiconductor substrate of a first conductivity type as a first semiconductor layer;
forming a second semiconductor layer of a second conductivity type on a first principal surface of the first semiconductor layer;
implanting light ions into the first semiconductor layer by penetrating into one of the first semiconductor layer or the second semiconductor layer with light ions;
thinning a second principal surface of the first semiconductor layer;
implanting on the thinned second principal surface of the first semiconductor layer with impurity ions of the first conductivity type; and
heat treating to form a third semiconductor layer with an ion-implanted layer on the second principal surface of the first semiconductor layer, and to electrically activate a region implanted with the light ions in the first semiconductor layer between the second semiconductor layer and the third semiconductor layer.
2. The method of manufacturing a semiconductor device as claimed in claim 1 , wherein the light ions exist in a direction from the second semiconductor layer to the third semiconductor layer up to positions respectively reaching the second semiconductor layer and the third semiconductor layer.
3. The method of manufacturing a semiconductor device as claimed in claim 1 , wherein the light ions exist in a direction from the second semiconductor layer to the third semiconductor layer up to positions respectively apart from the second semiconductor layer and the third semiconductor layer.
4. The method of manufacturing a semiconductor device as claimed in claim 1 , 2 , or 3 , wherein the light ions are protons.
5. The method of manufacturing a semiconductor device as claimed in claim 1 , 2 , or 3 , wherein an amount of the implanted light ions is between 1×10 11 cm −2 and 1×10 14 cm −2 .
6. The method of manufacturing a semiconductor device as claimed in claim 1 , 2 , or 3 , wherein a temperature of the heat treatment is between 300° C. and 600° C.
7. A method of manufacturing a semiconductor device comprising:
a first semiconductor layer of a first conductivity type;
a second semiconductor layer of a second conductivity type formed on one principal surface of the first semiconductor layer with an impurity concentration higher than that of the first semiconductor layer; and
a third semiconductor layer of a first conductivity type formed on the other principal surface of the first semiconductor layer with an impurity concentration higher than that of the first semiconductor layer,
wherein the first semiconductor layer has an impurity concentration becoming a relative maximum at a plurality of positions in a direction from the second semiconductor layer to the third semiconductor layer, and
wherein the impurity concentration of the first semiconductor layer decreases from the positions at each of which the impurity concentration becomes the relative maximum with an inclination toward each of the second semiconductor layer and the third semiconductor layer,
the method comprising the steps of:
providing a semiconductor substrate of the first conductivity type as the third semiconductor layer;
forming the first semiconductor layer of the first conductivity type on the third semiconductor layer by an epitaxial growth, while holding the impurity concentration of the first conductivity type constant, and epitaxially growing to a specified position in a direction opposite to the third semiconductor layer while gradually increasing the impurity concentration of the first conductivity type, and then carrying out epitaxial growth while gradually decreasing the impurity concentration of the first conductivity type from the specified position; and
forming the second semiconductor layer by diffusing impurities of the second conductivity type on a surface of the finally formed epitaxial layer.
8. The method of manufacturing a semiconductor device as claimed in claim 7 , wherein the epitaxial growth is carried out while stepwisely increasing and decreasing the impurity concentration of the first conductivity type.