Power semiconductor devices and methods of manufacture
View Patent ↗Various embodiments for improved power devices as well as their methods of manufacture, packaging and circuitry incorporating the same for use in a wide variety of power electronic applications are disclosed. One aspect of the invention combines a number of charge balancing techniques and other techniques for reducing parasitic capacitance to arrive at different embodiments for power devices with improved voltage performance, higher switching speed, and lower on-resistance. Another aspect of the invention provides improved termination structures for low, medium and high voltage devices. Improved methods of fabrication for power devices are provided according to other aspects of the invention. Improvements to specific processing steps, such as formation of trenches, formation of dielectric layers inside trenches, formation of mesa structures and processes for reducing substrate thickness, among others, are presented. According to another aspect of the invention, charge balanced power devices incorporate temperature and current sensing elements such as diodes on the same die. Other aspects of the invention improve equivalent series resistance (ESR) for power devices, incorporate additional circuitry on the same chip as the power device and provide improvements to the packaging of charge balanced power devices.
1. A semiconductor device comprising:
a drift region of a first conductivity type;
a well region extending above the drift region and having a second conductivity type opposite the first conductivity type;
an active trench extending through the well region and into the drift region, the active trench having its sidewalls and bottom lined with dielectric material, and substantially filled with a first conductive layer and a second conductive layer, the second conductive layer forming a gate electrode and being disposed above the first conductive layer and separated therefrom by inter-electrode dielectric material;
source regions having the first conductivity type formed in the well region adjacent the active trench; and
a charge control trench extending deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region.
2. The semiconductor device of claim 1 wherein a source electrode electrically couples a conductive material inside-the charge control trench to the source region.
3. The semiconductor device of claim 1 wherein inside the charge control trench is disposed a plurality of conductive layers stacked vertically and separated from each other and from the trench sidewalls by dielectric material.
4. The semiconductor device of claim 3 wherein the plurality of conductive layers inside the charge control trench are electrically biased to provide vertical charge balancing in the drift region.
5. The semiconductor device of claim 4 wherein the plurality of conductive layers inside the charge control trench are configured to be independently biased.
6. The semiconductor device of claim 3 wherein thicknesses of the plurality of conductive layers inside the charge control trench vary.
7. The semiconductor device of claim 1 wherein the thickness of a first conductive layer that is deeper inside the charge control trench is smaller than the thickness of a second conductive layer that is disposed above the first conductive layer.
8. The semiconductor device of claim 1 wherein the first conductive layer inside the active trench forms a first shield electrode configured to be electrically biased to a desired potential.
9. The semiconductor device of claim 1 wherein the first shield electrode and the source regions are configured to be electrically coupled to substantially the same potential.
10. The semiconductor device of claim 4 wherein the plurality of conductive layers inside the charge control trench are configured to be tied together electrically.
11. The semiconductor device of claim 4 wherein at least one of the plurality of conductive layers is within the drift region.
12. The semiconductor device of claim 4 wherein all of the plurality of conductive layers are within the drift region.
13. The semiconductor device of claim 4 wherein at least one of the plurality of conductive layers is outside of the drift region.
14. The semiconductor device of claim 4 wherein at least one of the plurality of conductive layers is within the p+ heavy body regions.
15. The semiconductor device of claim 4 wherein at least one of the plurality of conductive layers is within the body region.
16. The semiconductor device of claim 4 wherein one of the plurality of conductive layers is located within both the body region and the drift region.
17. The semiconductor device of claim 1 further comprising a second charge control trench located next to the active control trench on the opposite side of the charge control trench wherein the second charge control trench extends deeper into the drift region than the active trench and substantially filled with material to allow for vertical charge control in the drift region.
18. The semiconductor device of claim 17 wherein the charge control trench and the second charge control trench are positioned substantially the same distance away from the active control trench.