DARK CURRENTS AND REDUCING DEFECTS IN IMAGE SENSORS AND PHOTOVOLTAIC JUNCTIONS

• US 20100110239A1
• Filed: 10/28/2009
• Published: 05/06/2010
• Est. Priority Date: 10/31/2008
• Status: Active Grant

• Current Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Original Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Inventors: Rodier, Dennis, Ramappa, Deepak
• Granted Patent: US 8,815,634 B2
• Time in Patent Office: Days
• US Class Current: 348/243
• CPC Class Codes: H01L 21/76237 introducing impurities in trench side or bottom walls, e.g. for forming channel stoppers or alter isolation behavior
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14683 Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof not peculiar thereto H01L21/00
• 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

Dark currents within a photosensitive device are reduced through improved implantation of a species during its fabrication. Dark currents can be caused by defects in the photo-diode device, caused during the annealing, implanting or other processing steps used during fabrication. By amorphizing the workpiece in the photo-diode region, the number of defects can be reduced thereby reducing this cause of dark current. Dark current is also caused by stress induced by an adjacent STI, where the stress caused by the liner and fill material exacerbate defects in the workpiece. By amorphizing the sidewalls and bottom surface of the trench, defects created during the etching process can be reduced. This reduction in defects also decreases dark current in the photosensitive device.

Claims

1. A method of reducing dark current in a photosensitive device on a workpiece, comprising:

etching a shallow trench in said workpiece, said trench comprising sidewalls and a bottom surface;

performing an oxidation or nitridation step to create a layer on said sidewalls and said bottom surface of said trench;

amorphizing said sidewalls and bottom surface of said trench;

filling said trench with material; and

forming said photosensitive device adjacent to said trench.

2. The method of claim 1, wherein said amorphizing is performed before said oxidation or nitridation step.

3. The method of claim 1, wherein said amorphizing is performed after said oxidation or nitridation step.

4. The method of claim 1, wherein said amorphizing is performed at least partially during said oxidation or nitridation step.

5. The method of claim 1, wherein said amorphizing comprises implanting ions in said workpiece at an implant energy between 0.5 keV and 20 keV.

6. The method of claim 1, wherein said amorphizing comprises implanting ions in said workpiece at a dose of between 1E11 and 1E15.

7. The method of claim 1, wherein said amorphizing comprises implanting ions of a non-doping species.

8. The method of claim 7, wherein said non-doping species is selected from the group consisting of helium, hydrogen, argon, krypton, neon, xenon, silicon, germanium, oxygen and nitrogen.

9. The method of claim 1, wherein said amorphizing is performed at temperatures below +30°

C.

10. The method of claim 1, wherein said amorphizing is performed at temperature between 60°

C. and 900°

C.

11. The method of claim 1, wherein said forming comprises implanting ions of one species to create a P-type region and implanting ions of a second species to create an N-type region beneath said P-type region.

12. A method of reducing dark current in a photosensitive device on a workpiece, comprising:

implanting ions of a first species into said workpiece to form a first doped region, wherein said implant of said first species is performed at a temperature that is dependent on the desired dosage of said first species; and

implanting ions of a second species into said workpiece to form a second doped region above said first region, wherein said implant of said second species is performed at a temperature that is dependent on the desired dosage of said second species.

13. The method of claim 12, wherein said photosensitive device comprises an image sensor.

14. The method of claim 12, wherein said photosensitive device comprises a photovoltaic device.

15. The method of claim 12, wherein said implant of said first species is performed at between 60°

C. and 900°

C. if the dose rate of said first species is less than an amorphization threshold of workpiece.

16. The method of claim 12, wherein said implant of said first species is performed at between +30°

C. and −

200°

C. if the dose rate of said first species is greater than an amorphization threshold of workpiece.

17. The method of claim 12, wherein said implant of said second species is performed at between 60°

C. and 900°

C. if the dose rate of said second species is less than an amorphization threshold of workpiece.

18. The method of claim 12, wherein said implant of said second species is performed at between +30°

C. and −

200°

C. if the dose rate of said second species is greater than an amorphization threshold of workpiece.

19. The method of claim 12, wherein said temperature of said implant of said first species is dependent on the mass of said first species, and said temperature of said implant of said second species is dependent on the mass of said second species.