Method of etching backside Si substrate of SOI substrate to expose SiO2 layer using fluonitric acid

Patent metadata

Field	Value
Publication number	US-9240505-B2
Application number	US-201113883828-A
Country	US
Kind code	B2
Filing date	Oct 28, 2011
Priority date	Nov 12, 2010
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

A method of etching capable of rapidly and flatly performing wet etching on a Si substrate using fluonitric acid represented by HF(a)HNO 3 (b)H 2 O(c) (where the unit of a, b and c is wt % and a+b+c=100). The etching rate of an SiO 2 layer with the highly concentrated fluonitric acid is significantly lowered by the appropriate selection of its composition as compared with the etching rate of the Si substrate, and etch the Si substrate until the SiO 2 layer is exposed. In this way, it is possible to rapidly etch the Si substrate and significantly enhance the flatness of the etched surface.

First claim

The invention claimed is:

1. A method of producing a backside illumination type photoelectric conversion module, the method comprising the steps of:
producing a pre-photoelectric conversion module having a photoelectric conversion portion with a plurality of photoelectric conversion elements on the surface Si layer of an SOI substrate comprising an SiO 2 layer between a Si substrate and a surface Si layer; and
etching a free surface of the Si substrate with an etching method comprising a step of exposing a free surface of the Si substrate to a fluonitric acid HF(a) HNO 3 (b) H 2 O(c) (where a, b and c are numerical values representing concentrations, the unit thereof is wt % and a+b+c=100), so that at least a part of the SiO 2 layer is exposed and the etching is stopped on the SiO 2 layer, wherein
a composition of the fluonitric acid satisfies a+b≧50 and
an opening portion that exposes the SiO 2 layer is an entrance surface through which light enters the photoelectric conversion portion.

2. The etching method according to claim 1 , wherein the SiO 2 layer has a stoichiometric composition ratio.

3. The etching method according to claim 1 or 2 , wherein the composition of the fluonitric acid satisfies 19≦a≦42.

4. The etching method according to claim 3 , wherein the composition of the fluonitric acid further satisfies 23≦a≦40.

5. The etching method according to claim 4 , wherein the composition of the fluonitric acid further satisfies 27≦a≦37.

Assignees

• Ohmi Tadahiro
• Ohashi Tomotsugu
• Yoshikawa Kazuhiro
• Yoshida Tatsuro
• Uchimura Teppei
• Soeda Kazuki
• Sugawa Shigetoshi
• Univ Tohoku

Inventors

• Ohmi Tadahiro
• Ohashi Tomotsugu
• Yoshikawa Kazuhiro
• Yoshida Tatsuro
• Uchimura Teppei
• Soeda Kazuki
• Sugawa Shigetoshi

Classifications

• H10P72/0424

  using mainly spraying means, e.g. nozzles · CPC title

• H10P50/642 Primary

  Chemical etching · CPC title

• H10P50/691

  for Group V materials or Group III-V materials · CPC title

• H10P50/00 Primary

  Etching of wafers, substrates or parts of devices · CPC title

• H10D30/6758

  characterised by the insulating substrates · CPC title