High voltage semiconductor devices and methods of making the devices
A multi-cell MOSFET device including a MOSFET cell with an integrated Schottky diode is provided. The MOSFET includes n-type source regions formed in p-type well regions which are formed in an n-type drift layer. A p-type body contact region is formed on the periphery of the MOSFET. The source metallization of the device forms a Schottky contact with an n-type semiconductor region adjacent the p-type body contact region of the device. Vias can be formed through a dielectric material covering the source ohmic contacts and/or Schottky region of the device and the source metallization can be formed in the vias. The n-type semiconductor region forming the Schottky contact and/or the n-type source regions can be a single continuous region or a plurality of discontinuous regions alternating with discontinuous p-type body contact regions. The device can be a SiC device. Methods of making the device are also provided.
1. A multi-cell MOSFET device comprising:
an n-type drift layer on an n-type substrate;
a plurality of MOSFET cells, each of the MOSFET cells comprising:
first and second p-type well regions in spaced relation on the n-type drift layer;
an n-type JFET region on the n-type drift layer between the first and second p-type well regions, wherein each of the first and second p-type well regions has a channel region adjacent the JFET region;
first and second n-type source regions on each of the first and second p-type well regions and adjacent the channel regions opposite the JFET region, wherein the first and second n-type source regions have a higher dopant concentration than the n-type drift layer;
source ohmic contacts on each of the first and second n-type source regions;
a gate dielectric layer on the JFET region and channel regions;
a gate layer on the gate dielectric layer;
an interlayer dielectric layer on the gate layer; and
first and second p-type body contact regions on the n-type drift layer and adjacent the first and second n-type source regions opposite the channel regions, wherein the first and second p-type body contact regions have a higher dopant concentration than the first and second p-type well regions;
one or more n-type Schottky regions on the n-type drift layer adjacent one or more of the MOSFET cells;
a source metal layer on and in contact with the source ohmic contacts; and
a Schottky metal layer on and in contact with the one or more n-type Schottky regions, the Schottky metal layer forming a Schottky contact with the one or more n-type Schottky regions; wherein
each of the one or more n-type Schottky regions is adjacent and between the p-type body contact regions of adjacent MOSFET cells;
the first and second p-type well regions are elongate regions spaced from one another in an x direction and extending in a y direction perpendicular to the x direction;
the n-type JFET region is an elongate region extending in the x direction between the first and second p-type well regions;
the first and second p-type body contact regions are elongate regions extending in the y direction;
a p-type body contact region of a first of the plurality of MOSFET cells is connected to an adjacent p-type body contact regions of a second of the plurality of MOSFET cells by lateral p-type body contact regions spaced in the y-direction and extending in the x direction; and
the Schottky region between the first and second MOSFET cells comprises a plurality of separate Schottky regions between the lateral p-type body contact regions in the y direction and between the p-type body contact regions of the first and second MOSFET cells in the x direction.
2. The multi-cell MOSFET device of claim 1 , wherein the one or more n-type Schottky regions have a different dopant concentration than the n-type drift layer.
3. The multi-cell MOSFET device of claim 1 , wherein the n-type JFET region has a different dopant concentration than the n-type drift layer.
4. The multi-cell MOSFET device of claim 1 , further comprising a dielectric material over the source ohmic contacts and the one or more n-type Schottky regions, the device further comprising:
one or more source vias formed through the dielectric material over the source ohmic contacts; and
one or more Schottky vias formed through the dielectric material over the one or more n-type Schottky regions;
wherein the source metal layer is on the dielectric material and in the source and Schottky vias and wherein the source metal layer contacts the Schottky regions at the bottom of the Schottky vias and the source ohmic contacts at the bottom of the source vias.
5. The multi-cell MOSFET device of claim 1 , further comprising dielectric material in the first and second p-type body contact regions.
6. The multi-cell MOSFET device of claim 4 , further comprising dielectric material in the first and second p-type body contact regions.
7. The multi-cell MOSFET device of claim 1 , wherein the device comprises one n-type Schottky region for each of the MOSFET cells.
8. The multi-cell MOSFET device of claim 1 , wherein the device comprises less than one n-type Schottky region for each MOSFET cell.
9. The multi-cell MOSFET device of claim 1 , wherein the device comprises an even number of MOSFET cells and one n-type Schottky region for every two MOSFET cells.
10. The multi-cell MOSFET device of claim 1 , wherein the device is a SiC device.