Method for fabricating laterally insulated integrated circuit chips

• US 10,643,856 B2
• Filed: 07/12/2018
• Issued: 05/05/2020
• Est. Priority Date: 07/13/2017
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Rouviere, Mathieu, Boufnichel, Mohamed, Laconde, Eric
• Primary Examiner(s): Kebede, Brook
• Application Number:
  US16/033,334
• Publication Number:
  US 20190019687A1
• Time in Patent Office: 663 Days
• Field of Search: 438700
• CPC Class Codes: B81C 2201/0112 Bosch process
• CPC Class Codes: H01J 2237/3341 Reactive etching
• CPC Class Codes: H01L 21/30655 comprising alternated and repeated etching and passivation steps, e.g. Bosch process
• CPC Class Codes: H01L 21/308 using masks H01L21/3063, H01L21/3065 take precedence
• CPC Class Codes: H01L 21/3105 After-treatment
• CPC Class Codes: H01L 21/78 with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304

Abstract

Laterally insulated integrated circuit chips are fabricated from a semiconductor wafer. Peripheral trenches are formed in the wafer which laterally delimit integrated circuit chips to be formed. A depth of the peripheral trenches is greater than or equal to a desired final thickness of the integrated circuit chips. The peripheral trenches are formed by a process which repeats successive steps of a) ion etching using a sulfur hexafluoride plasma, and b) passivating using an octafluorocyclobutane plasma. Upon completion of the step of forming the peripheral trenches, lateral walls of the peripheral trenches are covered by an insulating layer of a polyfluoroethene. A thinning step is performed on the lower surface of the wafer until a bottom of the peripheral trenches is reached. The insulating layer is not removed.

Claims

1. A method for fabricating laterally insulated integrated circuit chips from a semiconductor wafer, comprising the following successive steps:

forming peripheral trenches laterally delimiting each of the integrated circuit chips to be formed, wherein a depth of the peripheral trenches is greater than or equal to a desired final thickness of the integrated circuit chips, wherein forming comprises repeating successive steps of;

a) ion etching the semiconductor wafer using a sulfur hexafluoride plasma to form a peripheral trench portion; and

b) passivating the peripheral trench portion using an octafluorocyclobutane plasma such that, upon completion of the step of forming, lateral walls of the peripheral trenches are covered by an insulating layer made of a polyfluoroethene; and

thinning the semiconductor wafer via a lower face until reaching a bottom of the peripheral trenches, without performing a prior step of removing said insulating layer.

2. The method according to claim 1, wherein a duration of a last passivating step is longer than a duration of any passivating step by at least 50%.

3. The method according to claim 2, wherein the duration of the last passivating step is between 10 seconds and 7 minutes.

4. The method according to claim 1, wherein a thickness of the insulating layer is between 100 nm and 3 μ

m.

5. The method according to claim 1, wherein a depth of the peripheral trenches is greater than the desired final thickness of the integrated circuit chips by 10 to 50 μ

m.

6. The method according to claim 1, wherein a width of the peripheral trenches is between 5 and 80 μ

m.

7. An electronic integrated circuit chip, comprising:

a semiconductor substrate;

one or more electronic components formed in the semiconductor substrate; and

an insulating layer of polyfluoroethene, having a thickness that is between 100 nm and 3 μ

m, that covers lateral faces of the semiconductor substrate which define an outer perimeter of the integrated circuit chip.

8. A method, comprising:

performing the following steps to form a peripheral trench in a semiconductor wafer that laterally delimits an integrated circuit chip area;

a) ion etching the semiconductor wafer using a sulfur hexafluoride plasma to form a peripheral trench portion;

b) passivating the peripheral trench portion using an octafluorocyclobutane plasma to cover lateral walls of the peripheral trench portion with an insulating layer made of a polyfluoroethene; and

c) repeating steps a) and b) a plurality of times such that a combined depth of the peripheral trench portions is greater than or equal to a desired final integrated circuit chip thickness;

thinning the semiconductor wafer via a lower face until reaching a bottom of the peripheral trench to release an integrated circuit chip from the semiconductor wafer; and

leaving the insulating layers made of the polyfluoroethene in place to laterally insulate the released integrated circuit chip.

9. The method of claim 8, further comprising mounting the released integrated circuit chip to a support substrate using a solder material, said polyfluoroethene that laterally insulates the released integrated circuit chip preventing the solder material from forming a short circuit to a semiconductor substrate of the released integrated circuit chip.

10. The method of claim 8, wherein a duration of a last step of passivating is longer than a duration of any preceding step of passivating by at least 50%.

11. The method of claim 10, wherein the duration of the last step of passivating is between 10 seconds and 7 minutes.

12. The method of claim 8, wherein a thickness of the polyfluoroethene is between 100 nm and 3 μ

m.

13. The method of claim 8, wherein a depth of the peripheral trench is greater than the desired final integrated circuit chip thickness by 10 to 50 μ

m.

14. The method of claim 8, wherein a width of the peripheral trench is between 5 and 80 μ

m.