Power semiconductor rectifier having broad buffer structure and method of manufacturing thereof
AssigneeFuji Electric Co., Ltd.
InventorMichio Nemoto
Life of this patent
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Abstract
Impurity concentration (Nd(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 Np to an averaged impurity concentration Ndm 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.
Claims8
A method of manufacturing a semiconductor device comprising the steps of:
- preparing a semiconductor substrate of a first conduction type as a first semiconductor layer;
- forming a second semiconductor layer of a second conduction 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 and the second semiconductor layer with light ions;
- thinning a second principal surface of the first semiconductor layer;
- implanting on the thinned surface of the first semiconductor layer with impurity ions of the first conduction type;
- and
- heat treating to form a third semiconductor layer with an ion-implanted layer on the 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.
In a method of manufacturing a semiconductor device comprising:
- a first semiconductor layer of a first conduction type;
- a second semiconductor layer of a second conduction 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 conduction 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:
- preparing a semiconductor substrate of the first conduction type as the third semiconductor layer;
- forming the first semiconductor layer of the first conduction type on the third semiconductor layer by an epitaxial growth, while holding the content of the impurities of the first conduction type constant, and epitaxially growing to a specified position in a direction opposite to the third semiconductor layer while gradually increasing the content of the impurities of the first conduction type, and then carrying out epitaxial growth while gradually decreasing the content of the impurities from the specified position;
- and
- forming the second semiconductor layer by diffusing impurities of the second conduction type on a surface of the finally formed epitaxial layer.
Dependencies are inferred from the claim text.