Method for making thin film semiconductor

• US 6,194,245 B1
• Filed: 12/07/1999
• Issued: 02/27/2001
• Est. Priority Date: 03/18/1996
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tayanaka, Hiroshi
• Primary Examiner(s): Bowers, Charles
• Assistant Examiner(s): LEE, HSIEN MING
• Application Number:
  US09/455,844
• Time in Patent Office: 448 Days
• Field of Search: 438/57, 438/458, 438/459, 438/455, 438/464, 257/461, 136/252
• US Class Current: 438/57
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/0245 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02488 Insulating materials
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02658 Pretreatments cleaning in general H01L21/02041
• CPC Class Codes: H01L 21/02664 Aftertreatments planarisation in general H01L21/304
• CPC Class Codes: H01L 21/3063 Electrolytic etching
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 21/76251 using bonding techniques
• CPC Class Codes: H01L 21/76259 with separation/delamination along a porous layer
• CPC Class Codes: H01L 2221/68318 Auxiliary support including means facilitating the separation of a device or wafer from the auxiliary support
• CPC Class Codes: H01L 2221/6835 used as a support during build up manufacturing of active devices
• CPC Class Codes: H01L 2221/68359 used as a support during manufacture of interconnect decals or build up layers
• CPC Class Codes: H01L 2221/68363 used in a transfer process involving transfer directly from an origin substrate to a target substrate without use of an intermediate handle substrate
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/03921 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/048 : Encapsulation of modules
• CPC Class Codes: H01L 31/049 : Protective back sheets
• CPC Class Codes: H01L 31/077 : the devices comprising monocrystalline or polycrystalline materials
• CPC Class Codes: H01L 31/1804 : comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1892 : methods involving the use of temporary, removable substrates
• CPC Class Codes: H01L 33/0054 : for devices with an active region comprising only group IV elements
• CPC Class Codes: H01L 33/346 : containing porous silicon
• 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
• CPC Class Codes: Y10S 438/928 : Front and rear surface processing
• CPC Class Codes: Y10S 438/96 : Porous semiconductor
• CPC Class Codes: Y10S 438/977 : Thinning or removal of substrate

Abstract

The present invention provides new and improved methods for making crystalline semiconductor thin films which may be bonded to different kinds of substrates. The thin films may be flexible. In accordance with preferred methods, a multi-layer porous structure including two or more porous layers having different porosities is formed in a semiconductor substrate. A semiconductor thin film is grown on the porous structure. Electrodes and/or a desired support substrate may be attached to the grown film. The grown film is separated from the semiconductor substrate along a line of weakness defined in the porous structure. The separated thin film attached to the support substrate may be further processed to provide improved film products, solar panels and light emitting diode devices. These thin film semiconductors are excellent in crystallinity and may be inexpensively produced, thereby enabling production of solar cells and light emitting diodes at lower cost.

Claims

1. A method for making a solar cell comprising the steps of:

providing a semi-conductor substrate having a surface;

forming a porous structure adjacent the surface of the substrate including a first porous layer adjacent the surface having a first porosity, a second porous layer adjacent the first porous layer opposite the surface having a second porosity greater than said first porosity and a third porous layer in or adjacent to the second porous layer having a third porosity greater than said second porosity;

forming an epitaxially grown film semi-conductor structure on the surface including at least one hetero junction;

forming a SiO₂ insulating layer on an exposed surface of the film semi-conductor structure;

patterning and etching the insulating layer to define holes;

depositing a metal film on the insulating layer to form a metal film layer;

patterning and etching the metal film layer to form electrodes disposed in the holes;

attaching elongated conductors having at least one extending end portion to the electrodes;

attaching a support substrate to the surface overlying the electrodes and conductors with a binder material; and

thereafter, separating the film semi-conductor structure and support substrate from the semi-conductor substrate along one of;

a line of relative weakness defined in the third porous layer, at an interface defined between said third porous layer and the second porous layer, or adjacent an interface defined between said third porous layer and the second porous layer.

2. A method for making a solar cell as defined in claim 1, wherein the epitaxially grown film semi-conductor structure comprises a p⁺/p⁻

/n⁺ film semiconductor structure.

3. A method for making a solar cell as defined in claim 1 further comprising the step of applying a metal electrode to a surface of the separated film semiconductor structure opposite the support substrate.

4. A method for making a solar cell as defined in claim 1, wherein the support substrate comprises metal, glass, ceramic or polymer.

5. A method for making a solar cell as defined in claim 1, wherein the support substrate is a flexible subtrate.

6. A method for making a solar cell as defined in claim 1, wherein the support substrate and binder are transparent.

7. A method for making a semiconductor film comprising the steps of:

providing a semiconductor substrate having a surface;

forming a porous layer adjacent said surface, the porous layer comprises a first porous layer having a first porosity and a second porous layer having a second porosity higher than said first porosity and a third porous layer having a third porosity higher than said second porosity;

forming at least one semiconductor film on said surface; and

separating semiconductor film from said semiconductor substrate.

8. The method as claimed in claim 7, wherein said first porous layer is formed by anodization.

9. The method as claimed in claim 7, wherein said second porous layer is formed by anodization.

10. The method as claimed in claim 7, wherein said third porous layer is formed by anodization.

11. The method as claimed in claim 7 further comprising the step of:

after said porous layer forming step and prior to said semiconductor film forming step, annealing said semiconductor substrate in a hydrogen atmosphere.