Method for making a semiconductor substrate comprising a variant porous layer

• US 6,759,310 B2
• Filed: 02/04/2002
• Issued: 07/06/2004
• Est. Priority Date: 12/26/1997
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tayanaka, Hiroshi
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): DUONG, KHANH B
• Application Number:
  US10/067,486
• Publication Number:
  US 20020153595A1
• Time in Patent Office: 883 Days
• Field of Search: 438/455, 438/406, 438/409, 438/458, 438/459, 438/507, 438/478, 438/466, 438/759, 438/485
• US Class Current: 438/458
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: H01L 21/02126 the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
• CPC Class Codes: H01L 21/02203 the layer being porous
• CPC Class Codes: H01L 21/02238 silicon in uncombined form, i.e. pure silicon
• CPC Class Codes: H01L 21/02258 formation by anodic treatment, e.g. anodic oxidation
• CPC Class Codes: H01L 21/02337 treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/02356 treatment to change the morphology of the insulating layer, e.g. transformation of an amorphous layer into a crystalline layer
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02502 consisting of two layers
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/31695 Deposition of porous oxides or porous glassy oxides or oxide based porous glass
• CPC Class Codes: H01L 21/76259 with separation/delamination along a porous layer
• CPC Class Codes: H01L 29/16 including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 29/20 including, apart from doping materials or other impurities, only AIIIBV compounds

Abstract

A semiconductor substrate includes a porous semiconductor having: a porous layer, with an impurity concentration on varying in the depth direction, or having a porous semiconductor containing an impurity with a content of 1×10¹⁸cm⁻³ or more, or provided by pore formation in an epitaxial growth layer. A method of making a semiconductor substrate; includes forming a variant impurity layer with an impurity concentration varying in the depth direction on one surface of a supporting substrate, and converting the variant impurity layer into a porous layer having a variant porosity in the depth direction. A method of making a thin-film semiconductive member; includes forming a semiconductive thin film on the supporting substrate and separating it by cleavage in the porous phase, in addition to the method for making the semiconductor substrate.

Claims

1. A method of making a semiconductor substrate comprising:

forming a variant impurity layer with an impurity concentration varying in a depth direction on one surface of a supporting substrate by means other than anodic oxidation, wherein a variant impurity layer including at least two sublayers having different impurity concentrations is formed in said variant layer forming step; and

forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that a porosity in the porous layer varies in the depth direction, wherein a porous layer including at least two sublayers having different porosities is formed in said porous layer forming step.

2. A method of making a semiconductor substrate according to claim 1, wherein at least two sublayers having different impurity concentrations are formed on one surface of the supporting substrate in said variant layer forming step.

3. A method of making a semiconductor substrate according to claim 1, wherein, in said variant layer forming step, a growth layer is deposited on one surface of the supporting substrate, and then an impurity is diffused into the growth layer so as to form at least two sublayers having different impurity concentrations.

4. A method of making a semiconductor substrate comprising:

forming a variant impurity layer with an impurity concentration varying in a depth direction on one surface of a supporting substrate by means other than anodic oxidation, wherein, in said variant layer forming step, a low-impurity sublayer comprising a semiconductor having a low impurity concentration is formed and a high-impurity sublayer comprising a semiconductor having a high impurity concentration is formed on the surface, away from the supporting substrate, of the low-impurity sublayer; and

forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that a porosity in the porous layer varies in the depth direction.

5. A method of making a semiconductor substrate according to claim 4, wherein, in said variant layer forming step, each of said supporting substrate and said variant impurity layer comprises p-type silicon containing a p-type impurity, the low-impurity sublayer has a p-type impurity concentration of 1×

10¹⁹ cm<sup>−

3</sup> or more, and the high-impurity sublayer has a p-type impurity concentration of less than 1×

10¹⁹ cm<sup>−

3</sup>.

6. A method of making a semiconductor substrate comprising:

forming a variant impurity layer with an impurity concentration varying in a depth direction on one surface of a supporting substrate by means other than anodic oxidation;

forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that a porosity in the porous layer varies in the depth direction; and

forming a semiconductive thin film on the surface, away from the supporting substrate, of the porous layer.

7. A method of making a semiconductor substrate according to claim 6, wherein said semiconductive thin film is formed of a single crystal provided by epitaxial growth.

8. A method of making a semiconductor substrate according to claim 6, wherein said semiconductive thin film comprises a semiconductor selected from the group consisting of a semiconductor containing at least one of silicon and germanium, a semiconductor containing gallium and arsenic, a semiconductor containing gallium and phosphorus, and a semiconductor containing gallium and nitrogen.

9. A method of making a semiconductor substrate comprising:

forming a variant impurity layer with an impurity concentration varying in a depth direction on one surface of a supporting substrate by means other than anodic oxidation;

forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that a porosity in the porous layer varies in the depth direction; and

heating the porous layer for recrystallization.

10. A method of making a semiconductor substrate comprising:

forming a high-impurity layer comprising a semiconductor having an impurity concentration of 1×

10¹⁸ cm<sup>−

3</sup> or more on one surface of a supporting substrate by means other than anodic oxidation, wherein in said high-impurity layer forming step, the high-impurity layer is formed by epitaxial growth; and

forming pores in the high-impurity layer by anodic oxidation to form a porous layer having different porosities in a depth direction.

11. A method of making a thin-film semiconductive member comprising:

forming a variant impurity layer with an impurity concentration varying in a depth direction on one surface of a supporting substrate by means other than anodic oxidation;

forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that a porosity in the porous layer varies in a depth direction;

forming a semiconductive thin film on the surface, away from the supporting substrate, of the porous layer; and

separating the semiconductive thin film from the supporting substrate by cleavage in a porous phase.

12. A method of making a thin-film semiconductive member comprising:

forming a high-impurity layer comprising a semiconductor having an impurity concentration of 1×

10¹⁸ cm<sup>−

3</sup> or more on one surface of a supporting substrate by means other than anodic oxidation;

forming pores in the high-impurity layer by anodic oxidation to form a porous layer having different porosities in a depth direction;

forming a semiconductive thin film on the surface, away from the supporting substrate, of the porous layer; and

separating the semiconductive thin film from the supporting substrate by cleavage in a porous phase.