Boron diffusion in silicon devices

• US 7,790,574 B2
• Filed: 12/13/2005
• Issued: 09/07/2010
• Est. Priority Date: 12/20/2004
• Status: Expired due to Fees

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Rohatgi, Ajeet, Kim, Dong Seop, Rounsaville, Brian, Nakayashiki, Kenta
• Primary Examiner(s): Graybill; David E
• Application Number:
  US11/301,527
• Publication Number:
  US 20060183307A1
• Time in Patent Office: 1,729 Days
• Field of Search: None
• US Class Current: 438/460
• CPC Class Codes: H01L 21/2255 the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

Claims

1. A process for boron diffusion in a wafer, comprising the steps of:

applying a boric oxide solution to a surface of the wafer;

heating the wafer during a first heating cycle at a ramp-up rate greater than 10°

C. per second to;

form a borosilicate glass on the surface of the wafer;

release an amount of boron underneath the borosilicate glass; and

heating the wafer during a second heating cycle to;

diffuse the released boron into the wafer;

wherein the first heating cycle and the second heating cycle occur consecutively during a single heating process.

2. The process of claim 1, further comprising the step of cleaning the surface of the wafer so that the surface is hydrophilic.

3. The process of claim 1, further comprising the step of cleaning the surface of the wafer so that the surface is hydrophobic.

4. The process of claim 1, wherein the boric oxide solution further comprises boric acid.

5. The process of claim 1, wherein the boric oxide solution further comprises the boric oxide in a solvent taken from a group consisting of ethanol and Isopropanol (IPA).

6. The process of claim 3, wherein the boric oxide solution further comprises a solvent that promotes the uniform coating of the boric oxide solution on the hydrophobic surface.

7. The process of claim 1, wherein heating the wafer during the first heating cycle further comprises the steps of:

evaporating a solvent component of the boric oxide solution;

minimizing evaporation of the boric oxide; and

facilitating a reaction between the boric oxide and the silicon to release the amount of boron underneath the borosilicate glass.

8. The process of claim 7, wherein the reaction between the boric oxide and the silicon forms a boron-silicon alloy due to a partial diffusion of the boron into the wafer.

9. The process of claim 8, wherein the borosilicate glass is removed from the surface of the wafer.

10. The process of claim 1, further comprising controlling a thickness of the borosilicate glass by adjusting a concentration of an amount of boric oxide in the boric oxide solution applied to the surface of the wafer.

11. The process of claim 1, wherein the wafer is heated during the first heating cycle at a rate of about 30°

C. per second.

12. The process of claim 1, wherein the first heating cycle comprises an operating temperature that falls within a range of 400°

C. to 1000°

C.

13. The process of claim 1, wherein the boric oxide solution is applied to the surface of the wafer by spraying the boric oxide solution onto the surface of the wafer.

14. The process of claim 1, wherein the boric oxide solution is applied to the surface of the wafer by dipping the wafer into the boric oxide solution.

15. The process of claim 1, wherein the boric oxide solution is applied to the surface of the wafer by spinning the boric oxide solution onto the wafer.

16. A process for boron diffusion in a silicon wafer, comprising the steps of:

applying a boric oxide solution to a surface of the wafer;

heating the wafer during a first heating cycle at a ramp-up rate greater than 10°

C. per second to;

form a borosilicate glass on an outer surface of the wafer;

release boron from the boric oxide into the silicon; and

form a boron-silicon alloy underneath the borosilicate glass;

heating the wafer during a second heating cycle to diffuse boron from the boron-silicon alloy into the wafer; and

wherein the first heating cycle and the second heating cycle occur consecutively during a single heating process.