Method for removing polysilicon protection layer on a back face of an IGBT having a field stop structure
Disclosed is a method for removing a polysilicon protection layer ( 12 ) on a back face of an IGBT having a field stop structure ( 10 ). The method comprises thermally oxidizing the polysilicon protection layer ( 12 ) on the back face of the IGBT until the oxidation is terminated on a gate oxide layer ( 11 ) located above the polysilicon protection layer ( 12 ) to form a silicon dioxide layer ( 13 ), and removing the formed silicon dioxide layer ( 13 ) and the gate oxide layer ( 11 ) by a dry etching process. The method for removing the protection layer is easier to control.
1. A method for removing a polysilicon protection layer on a back face of an IGBT having a field stop structure, comprising:
thermally oxidizing the polysilicon protection layer on the back face of the IGBT until the oxidation is terminated on a gate oxide layer located above the polysilicon protection layer to form a SiO 2 layer; and
removing the formed SiO 2 layer and the gate oxide layer by a dry etching process.
2. The method of claim 1 , wherein the gate oxide layer is removed after the oxidation is terminated.
3. The method of claim 1 , wherein oxidation of the polysilicon protection layer is terminated after complete oxidation of the polysilicon protection layer.
4. The method of claim 3 , wherein oxidation of the polysilicon protection layer is terminated due to contact with the gate oxide layer.
5. The method of claim 1 , wherein thermally oxidizing the polysilicon protection layer includes gradually transforming the polysilicon protection layer on the back face of the IGBT into SiO 2 .
6. The method of claim 1 , wherein termination of oxidation of the polysilicon protection layer is due to a barrier effect of SiO 2 .
7. The method of claim 1 , wherein thermal oxidation of the polysilicon protection layer is terminated due to contact with the gate oxide layer after polysilicon has been completely oxidized.
8. The method of claim 1 , wherein the gate oxide layer is a dielectric layer formed by SiO 2 , and further wherein method further comprises creating a barrier effect with the gate oxide layer to terminate oxidation.
9. The method of claim 1 , wherein the step of thermally oxidizing includes:
gradually transforming polysilicon on the back face into SiO 2 ; and
terminating oxidation of the polysilicon protection layer due to a barrier effect of the SiO 2 .
10. A method for removing a polysilicon protection layer on a back face of an IGBT having a field stop structure, comprising the following steps:
a) thermally oxidizing a portion of the polysilicon protection layer to form a SiO 2 layer;
b) removing the formed SiO 2 layer by a dry etching process;
c) repeating the steps a) and b), until the thermal oxidation process in step a) is terminated on a gate oxide layer located above the polysilicon protection layer; and
removing the last formed SiO 2 layer and the gate oxide layer by a dry etching process.
11. The method of claim 10 , wherein the gate oxide layer is removed after the oxidation is terminated.
12. The method of claim 10 , wherein oxidation of the polysilicon protection layer is terminated after complete oxidation of the polysilicon protection layer.
13. The method of claim 12 , wherein oxidation of the polysilicon protection layer is terminated due to contact with the gate oxide layer.
14. The method of claim 10 , wherein thermally oxidizing the polysilicon protection layer includes gradually transforming the polysilicon protection layer on the back face of the IGBT into SiO 2 .
15. The method of claim 10 wherein termination of oxidation of the polysilicon protection layer is due to a barrier effect of SiO 2 .
16. The method of claim 10 , wherein thermal oxidation of the polysilicon protection layer is terminated due to contact with the gate oxide layer after polysilicon has been completely oxidized.
17. The method of claim 10 , wherein the gate oxide layer is a dielectric layer formed by SiO 2 , and further wherein method further comprises creating a barrier effect with the gate oxide layer to terminate oxidation.
18. The method of claim 10 , wherein the step of thermally oxidizing includes:
gradually transforming polysilicon on the back face into SiO 2 ; and
terminating oxidation of the polysilicon protection layer due to a barrier effect of the SiO 2 .
19. A method comprising:
removing a polysilicon protection layer on a back face of an IGBT having a field stop structure by:
thermally oxidizing the polysilicon protection layer on the back face of the IGBT until the oxidation is terminated on a gate oxide layer located above the polysilicon protection layer to form a SiO 2 layer; and
removing the formed SiO 2 layer and the gate oxide layer by a dry etching process; and
forming an IGBT structure by:
implanting ions into a face where the polysilicon protection layer and the gate oxide layer have been removed so as to form a P+ layer; and
depositing a metal formed layer on the formed P+ layer.
20. A method comprising:
removing a polysilicon protection layer on a back face of an IGBT having a field stop structure by:
a) thermally oxidizing a portion of the polysilicon protection layer to form a SiO 2 layer;
b) removing the formed SiO 2 layer by a dry etching process;
c) repeating the steps a) and b), until the thermal oxidation process in step a) is terminated on a gate oxide layer located above the polysilicon protection layer; and
d) removing the last formed SiO 2 layer and the gate oxide layer by a dry etching process; and
forming an IGBT structure by:
implanting ions into a face where the polysilicon protection layer and the gate oxide layer have been removed so as to form a P+ layer; and
depositing a metal formed layer on the formed P+ layer.