Method of producing microcystalline silicon germanium suitable for micromachining
View Patent ↗A method of depositing a structural SiGe layer is presented. The structural SiGe layer may be located on top of a sacrificial layer above a substrate. The substrate may contain a semiconductor device such as a CMOS electronic circuit. The presented method uses a silicon source and a germanium source in a reaction zone to grow the structural SiGe layer. Hydrogen is introduced into the reaction zone and it may be used to dilute the silicon source and the germanium source. The resultant reaction occurs at temperatures below 450 degrees C., thereby preventing degradation of electronic device and/or other devices/materials located in the substrate.
1. A method of forming a structural Silicon Germanium (SiGe) layer, the structural SiGe layer having a predetermined average internal stress, the method comprising:
providing a substrate that includes a sacrificial layer;
providing a silicon source and a germanium source in a reaction zone that contains the substrate, wherein the silicon source and germanium source together are at a first concentration;
diluting the first concentration with hydrogen, wherein the hydrogen is at a second concentration that is at least ten times greater than the first concentration;
reacting the silicon source and the germanium source, wherein the reacting is performed in the presence of a plasma so as to deposit the structural SiGe layer on top of the sacrificial layer; and
removing the sacrificial layer.
2. The method as in claim 1 , wherein a temperature associated with the substrate is below 420 degrees C. during reacting the silicon source and the germanium source.
3. The method as in claim 2 , wherein the concentration of hydrogen is gradually changed during reacting the silicon source and the germanium source.
4. The method as in claim 1 , wherein the concentration of hydrogen is gradually decreased during reacting the silicon source and the germanium source.
5. The method as in claim 1 , wherein the structural SiGe layer has a silicon content that is between 30% and 75%.
6. The method as in claim 1 wherein reacting the silicon source and the germanium source is carried out at a pressure between 0.1 Torr and 20 Torr.
7. The method as in claim 1 , wherein the reaction zone is a deposition chamber.
8. The method as in claim 1 , wherein the plasma is generated by an RF power source at an RF power between 100 Watts and 700 Watts.
9. The method as in claim 1 , wherein the silicon source is silane.
10. The method as in claim 1 , wherein the germanium source is germane.
11. The method as in claim 1 , wherein the reaction zone further comprises:
providing a dopant source in the reaction zone; and
reacting the dopant source with the silicon source and the germanium source.
12. The method as in claim 1 , wherein a temperature associated with the reaction zone is below 400 degrees C.
13. The method as in claim 1 , wherein a temperature associated with the reaction zone is about 400 degrees C.
14. The method as recited in claim 1 , wherein the temperature in the reaction zone is below 350 degrees C.
15. The method as in claim 1 , wherein the substrate includes a CMOS device.
16. The method as in claim 1 , further comprising changing a reaction parameter associated with the reacting the silicon source and the germanium source so as to form a SiGe top layer on top of the structural SiGe layer.
17. The method as in claim 16 , wherein the reaction parameter is selected from the group consisting of a silicon concentration associated with the silicon source, a germanium concentration associated with the germanium source, a deposition pressure, a deposition temperature, and a power associated with the plasma.
18. The method as in claim 17 , wherein changing the parameter includes increasing the silicon concentration.
19. The method as in claim 1 , further comprising subsequent to reacting the silicon source and the germanium source, providing hydrogen in the reaction zone and adjusting at least one of the germanium source and the silicon source, wherein a concentration associated with at least one of the silicon and the germanium source is at an amount that is selected from the group consisting of reduced, negligible, or zero.
20. The method as in claim 1 , further comprising:
reacting the silicon source and the germanium source in the reaction zone so as to grow a second SiGe layer on top of the structural SiGe layer; and
subsequent to reacting the silicon source and the germanium source so as to grow the second SiGe layer, providing hydrogen in the reaction zone and adjusting at least one of the germanium source and the silicon source.