Local semiconductor wafer thinning
A local thinning process is employed on the backside of a semiconductor substrate such as a wafer in order to improve the thermal performance of the electronic device built on or in the front side of the wafer.
1. A method for thinning a semiconductor substrate, comprising:
providing a semiconductor substrate having a front side on or in which at least one electronic device is disposed, wherein the semiconductor substrate includes an active area and a termination region, the electronic device being formed on or in the active area;
performing a photolithographic process to locally thin the semiconductor substrate, the photolithographic process including:
(i) applying a photolithographic mask to a backside of the semiconductor substrate;
(ii) patterning the photolithographic mask with a selected geometrical pattern; and
(iii) etching the backside of the semiconductor substrate to transfer the selected geometrical pattern from the photolithographic mask to the backside of the semiconductor substrate, wherein the selected geometrical pattern transferred to the backside of the semiconductor substrate includes a plurality of depressions that do not fully extend though the semiconductor substrate such that the semiconductor substrate is not diced into multiple dice, wherein the etching etches the backside of the semiconductor substrate in the active area but not the termination region such that the backside is only thinned in the active area.
2. The method of claim 1 wherein the plurality of depressions include one or more grooves, trenches, holes or combinations thereof.
3. The method of claim 1 further comprising applying a protective layer to the front side of the semiconductor substrate before applying the mask.
4. The method of claim 1 further comprising applying a protective layer to the backside of the semiconductor substrate, wherein the applying the mask includes applying the mask onto the protective layer.
5. The method of claim 1 wherein the mask comprises a polymer material suitable for a photolithography process.
6. The method of claim 1 wherein etching the backside of the semiconductor substrate comprises etching the backside of the semiconductor substrate using a Deep Reactive-Ion Etching process.
7. The method of claim 1 wherein etching the backside of the semiconductor substrate comprises etching the backside of the semiconductor substrate using a Bosch process.
8. The method of claim 1 wherein the electronic device includes a diode.
9. The method of claim 1 wherein the electronic device includes a bipolar transistor.
10. The method of claim 1 wherein the electronic device includes a power field effect transistor.
11. The method of claim 1 wherein the electronic device includes a MOSFET.
12. The method of claim 1 further comprising performing one or more additional processes on the backside of the semiconductor substrate after etching the backside of the semiconductor substrate.
13. The method of claim 12 wherein the one or more additional processes are selected from the group consisting of deposition, photolithography, thermal, mechanical and doping processes.
14. The method of claim 12 wherein the one or more additional processes include a metal deposition process.
15. The method of claim 12 wherein etching the backside of the semiconductor wafer includes forming depressions in the backside of the semiconductor wafer and the one or more additional processes include a conductive material deposition process to fill depressions in the patterned backside structure.
16. The method of claim 15 further comprising depositing a seed layer on the backside of the semiconductor substrate before performing the conductive material deposition additional process.
17. The method of claim 1 wherein the electronic device is selected from the group consisting of an insulated-gate bipolar transistor (IGBT), Field Effect Transistor (FET), MOSFET and a diode.
18. A semiconductor substrate fabricated in accordance with the method set forth in claim 1 .
19. The semiconductor substrate of claim 18 further comprising an electronic device disposed on a front side of the substrate.
20. The method of claim 15 wherein the conductive material is copper and the conductive material deposition process is an electroplating process.
21. The method of claim 15 wherein the one or more additional processes include a chemical vapor deposition process (CVD) or a physical vapor deposition (PVD) process for filling depressions in the patterned backside structure.