Semiconductor device with selectively diffused regions

• US 6,552,414 B1
• Filed: 08/27/1999
• Issued: 04/22/2003
• Est. Priority Date: 12/24/1996
• Status: Expired due to Term

• Current Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International)
• Original Assignee: IMEC International
• Inventors: Szlufcik, Jozef, Horzel, Jörg, Honoré, Mia, Nijs, Johan
• Primary Examiner(s): Jackson, Jerome
• Assistant Examiner(s): Ortiz, Edgardo
• Application Number:
  US09/331,932
• Time in Patent Office: 1,334 Days
• Field of Search: 257/607, 257/608, 257/609, 257/610, 257/611, 257/612, 257/437, 257/461, 257/462, 257/463
• US Class Current: 257/655
• CPC Class Codes: H01L 21/67109 mainly by convection
• CPC Class Codes: H01L 21/67115 mainly by radiation
• CPC Class Codes: H01L 31/022425 for solar cells
• 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 31/0684 double emitter cells, e.g. bifacial solar cells
• 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

The present invention describes a method of manufacturing a semiconductor device, comprising a semiconductor substrate (2) in the shape of a slice, the method comprising the steps of: step 1) selectively applying a pattern of a solids-based dopant source to a first major surface of said semiconducting substrate (2); step 2) diffusing the dopant atoms from said solids-based dopant source into said substrate (2) by a controlled heat treatment step in a gaseous environment surrounding said semi-conducting substrate (2), the dopant from said solids-based dopant source diffusing directly into said substrate (2) to form a first diffusion region (12) and, at the time, diffusing said dopant from said solids-based dopant source indirectly via said gaseous environment into said substrate (2) to form a second diffusion region (15) in at least some areas of said substrate (2) not covered by said pattern; and step 3) forming a metal contact pattern (20) substantially in alignment with said first diffusion region (12) without having etched said second diffusion region (15) substantially.

Claims

1. A semiconductor device comprising:

a semiconducting substrate in the shape of a slice, a first and a second doped region in one major surface of the semiconductor substrate, the first doping region having a higher surface dopant concentration than the second doped region; and

a metal contact pattern substantially in alignment with said first doped region, wherein the surface dopant concentration of said second doped region increases with distance from within said second doped region towards said first doped region the increasing gradient in the surface concentration of the dopant facilitating carrier transport towards the metal contact pattern substantially along the length of the second doped region.

2. A semiconductor device according to claim 1, wherein the increase of surface dopant concentration is monotonic.

3. The semiconductor device according to claim 1, wherein the increase of surface dopant concentration is over a distance of about 1 mm.

4. The semiconductor device according to claim 1, wherein said substrate is of the first conductivity type and the dopant of said first doped region is of a second conductivity type.

5. The semiconductor device according to claim 1, further comprising a passivating layer over said first and second doped regions.

6. The semiconductor device according to claim 5, where said passivating layer is an oxide layer.

7. The semiconductor device according to claim 1, wherein the surface of said semiconducting substrate is texturised.

8. The semiconductor device according to claim 1, further comprising an anti-reflection coating.

9. The semiconductor device according to claim 1, wherein said second doped region forms an emitter or collector region in said semiconductor substrate.

10. The semiconductor device according to claim 1, wherein the ratio of the surface dopant concentrations between first and second doped regions is at least five and preferably about 10 or more.

11. The semiconductor device according to claim 1, wherein the second doped region has a central region of substantially uniform surface dopant concentration.

12. The semiconductor device according to claim 1, wherein said metal contact pattern forms an ohmic contact with said first doped region.

13. The semiconductor device according to claim 1, wherein the first and second doped regions are formed by diffusing dopant atoms from a solids-based dopant source into said substrate by a controlled heat treatment step in a gaseous environment surrounding said semiconducting substrate, the dopant from said solids-based dopant source diffusing directly into said substrate to form the first doped region in said substrate immediately beneath said solids-based dopant source and, at the same time, said dopant from said solids-based dopant source diffusing indirectly via said gaseous environment into said substrate to form the second doped region.