Method for removing polysilicon protection layer on a back face of an IGBT having a field stop structure

• US 9,607,851 B2
• Filed: 07/25/2013
• Issued: 03/28/2017
• Est. Priority Date: 07/26/2012
• Status: Active Grant

• Current Assignee: CSMC Technologies FAB1 Company Limited (CSMC Manufacturing Company Limited)
• Original Assignee: Cmsc Technologies Fab1 Co., Ltd.
• Inventors: Rui, Qiang, Zhang, Shuo, Wang, Genyi, Deng, Xiaoshe
• Primary Examiner(s): Dulka, John P
• Assistant Examiner(s): Peters, Charles R
• Application Number:
  US14/411,978
• Publication Number:
  US 20150155182A1
• Time in Patent Office: 1,342 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/32105 Oxidation of silicon-containing layers
• CPC Class Codes: H01L 21/32137 of silicon-containing layers
• CPC Class Codes: H01L 29/66325 controlled by field-effect, e.g. insulated gate bipolar transistors [IGBT]
• CPC Class Codes: H01L 29/66333 Vertical insulated gate bipolar transistors
• CPC Class Codes: H01L 29/7395 Vertical transistors, e.g. vertical IGBT

Abstract

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.

Claims

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 SiO₂ layer; and

removing the formed SiO₂ 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 SiO₂.

6. The method of claim 1, wherein termination of oxidation of the polysilicon protection layer is due to a barrier effect of SiO₂.

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 SiO₂, 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 SiO₂; and

terminating oxidation of the polysilicon protection layer due to a barrier effect of the SiO₂.

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 SiO₂ layer;

b) removing the formed SiO₂ 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 SiO₂ 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 SiO₂.

15. The method of claim 10 wherein termination of oxidation of the polysilicon protection layer is due to a barrier effect of SiO₂.

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 SiO₂, 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 SiO₂; and

terminating oxidation of the polysilicon protection layer due to a barrier effect of the SiO₂.

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 SiO₂ layer; and

removing the formed SiO₂ 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 SiO₂ layer;

b) removing the formed SiO₂ 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 SiO₂ 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.