DIRECT CURRENT ION IMPLANTATION FOR SOLID PHASE EPITAXIAL REGROWTH IN SOLAR CELL FABRICATION

• US 20120122273A1
• Filed: 11/17/2011
• Published: 05/17/2012
• Est. Priority Date: 11/17/2010
• Status: Abandoned Application

• Current Assignee: Intevac
• Original Assignee: Intevac
• Inventors: CHUN, Moon, ADIBI, Babak
• Application Number:
  US13/299,292
• Publication Number:
  US 20120122273A1
• Time in Patent Office: Days
• US Class Current: 438/98
• CPC Class Codes: H01L 21/2236 from or into a plasma phase
• CPC Class Codes: H01L 21/324 Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering H01L21/20 - H01L21/288 and H01L21/302 - H01L21/322 take precedence
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1864 Annealing
• CPC Class Codes: H01L 31/1872 Recrystallisation
• 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

An apparatus and methods for ion implantation of solar cells. The disclosure provide enhanced throughput and recued or elimination of defects after SPER anneal step. The substrate is continually implanted using continuous high dose-rate implantation, leading to efficient defect accumulation, i.e., amorphization, while suppressing dynamic self-annealing.

Claims

1. A method for fabricating solar cells using ion implantation, comprising:

introducing a substrate into an ion implantation chamber;

generating a continuous stream of ions to be implanted in the substrate;

directing the stream of ions toward the surface of the substrate to cause continuous ion bombardment of the surface of the substrate to thereby implant ions into the substrate while amorphizing a layer of the substrate.

2. The method of claim 1, wherein the step of generating a continuous stream of ion comprises generating a beam of ions having a cross section sufficiently large to enable simultaneous implantation over the entire surface of the substrate.

3. The method of claim 1, further comprising:

defining an area of the substrate to be implanted; and

,

wherein the step of generating a continuous stream of ion comprises generating a beam of ions having a cross section sufficiently large to enable simultaneous implantation over the entire area of the substrate to be implanted.

4. The method of claim 1, wherein the step of generating a continuous stream of ion comprises:

sustaining plasma using gas containing species to be implanted;

extracting a beam of ions of said species, wherein the beam has a cross section sufficiently large to enable simultaneous implantation over the entire surface of the substrate.

5. The method of claim 1, wherein the implant energy is 5-100 keV.

6. The method of claim 1, wherein the implant energy is 20-40 keV.

7. The method of claim 1, wherein the dose rate is higher than 1 E¹⁵ ions/cm⁻

2/second.

8. The method of claim 2, further comprising annealing the substrate using rapid thermal processing.

9. The method of claim 8, wherein the annealing is performed at 600-1000°

C. for about 1-10 seconds.

10. The method of claim 1, further comprising:

subsequent to the ion implantation process, and without performing an anneal step, fabricating a metallization layer on the substrate; and

,

subsequent to forming the metallization layer annealing the substrate to simultaneously anneal the metallization layer, recrystallize the amorphized layer, and activate implanted dopants.

11. A method for ion implantation of a substrate, comprising:

introducing a substrate into an ion implantation chamber;

generating a continuous stream of ions to be implanted in the substrate;

directing the stream of ions toward the surface of the substrate to cause continuous ion bombardment of the surface of the substrate while preventing self-anneal of the substrate.

12. The method of claim 11, wherein preventing self-anneal of the substrate comprises causing continuous bombardment of ion species over the entire surface to be implanted.

13. The method of claim 12, further comprising completely amorphizing a layer of the substrate to be implanted.

14. The method of claim 12, wherein the entire front surface of the substrate is implanted simultaneously.

15. The method of claim 11, wherein the step of generating a continuous stream of ion comprises:

sustaining plasma using gas containing species to be implanted;

extracting a column of ions of said species, wherein the column has a cross section sufficiently large to enable simultaneous implantation over the entire surface of the substrate.

16. The method of claim 15, wherein the step of extracting a column of ions comprises extracting a plurality of ion beams from the plasma and enabling the plurality of ion beams to combine inot a single column of ions.

17. The method of claim 16, wherein the implant energy is 5-100 keV.

18. The method of claim 16, wherein dose rate is designed so as to completely amorphize a designated layer of the substrate.

19. The method of claim 18, wherein the dose rate is higher than 1 E¹⁵ ions/cm⁻

2/second.

20. The method of claim 18, wherein the average dose is 5E14-5E16 cm⁻

2.

21. A method for ion implantation of a substrate, comprising:

introducing a substrate into an ion implantation chamber;

generating a continuous stream of ions to be implanted in the substrate;

directing the stream of ions toward the surface of the substrate to cause continuous ion bombardment of the surface of the substrate to thereby amorphize the entire surface of the substrate simultaneously.

22. The method of claim 21, wherein the step of generating a continuous stream of ion comprises:

sustaining plasma using gas containing species to be implanted;

extracting a column of ions of said species, wherein the column has a cross section sufficiently large to enable simultaneous implantation over the entire surface of the substrate.