Semiconductor device manufacturing: process – Gettering of substrate
Reexamination Certificate
2000-03-31
2001-08-21
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Gettering of substrate
C438S476000, C438S764000, C438S795000
Reexamination Certificate
active
06277712
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayered wafer having a thick sacrificial layer, which is obtained by forming a sacrificial layer of oxidized porous silicon or porous silicon and growing an epitaxial polysilicon layer on the sacrificial layer, and a fabrication method thereof.
2. Description of the Related Art
FIG. 1
is a cross-sectional view illustrating the stacked structure of a conventional silicon on insulator (SOI) wafer. As shown in
FIG. 1
, the conventional SOI wafer has a stacked structure in which an oxide layer
3
is formed on a substrate wafer
1
and a single crystal silicon wafer
6
is formed on the oxide layer
3
. Here, the oxide layer
3
, which is a sacrificial layer, is formed by thermal oxidization, so it is difficult to form a sacrificial layer having a thickness of 1 &mgr;m or more. Thus, when the oxide layer is used to make a structure such as a cantilever or a bridge, a completed structure frequently sticks to a substrate which lies under the structure, since the gap between the structure and the substrate is narrow. Also, in the case of a moving structure, great air damping is produced due to the short distance between the structure and the substrate. Also, since the silicon oxide layer is formed by thermal oxidization, it takes a long time to fabricate the structure. Furthermore, since the structure is fabricated by attaching another silicon wafer onto oxidized substrate silicon, that is, since two wafers are used, the fabrication cost is increased.
SUMMARY OF THE INVENTION
To solve the above problems, an objective of the present invention is to provide a multilayered wafer obtained by forming a porous silicon layer having a thickness of several tens of micrometers on a p
+
-type or n
+
-type substrate doped at a high concentration through anodic bonding of the surface of the substrate and growing an epitaxial polysilicon on the porous silicon, or a multilayered wafer having a thick sacrificial layer, which is obtained by depositing a polysilicon seed layer on oxidized porous silicon by chemical vapor deposition (CVD) and growing an epitaxial polysilicon layer on the polysilicon seed layer.
To achieve the above objective, a multilayered wafer with a thick sacrificial layer according to an embodiment is provided, including: a silicon wafer for use as a substrate; a sacrificial layer formed of porous silicon on the silicon wafer; and a polysilicon layer formed on the sacrificial layer.
In the multilayered wafer, the silicon wafer is preferably doped with p
+
-type or n
+
-type impurities, and the sacrificial layer and the polysilicon layer may be stacked several times.
To achieve the above objective, a method of fabricating the multilayered wafer with a thick sacrificial layer according to an embodiment is provided, including: (a) preparing for a p
+
-type or n
+
-type wafer as a substrate wafer; (b) forming a porous silicon layer having a predetermined thickness by anodic bonding the substrate wafer; and (c) growing an epitaxial polysilicon layer on the porous silicon layer.
In this method, the thickness of the porous silicon layer in the step (b) is preferably several micrometers to several tens of micrometers, and the steps (b) and (c) may be repeated.
To achieve the above objective, a multilayered wafer with a thick sacrificial layer according to another embodiment is provided, including: a silicon wafer for use as a substrate; a sacrificial layer formed of porous silicon oxide on the silicon wafer; and a polysilicon layer formed on the sacrificial layer.
In this multilayered wafer, the silicon wafer is preferably doped with p
+
-type or n
+
-type impurities, and the sacrificial layer and the polysilicon layer may be stacked several times.
To achieve the above objective, a method of fabricating the multilayered wafer with a thick sacrificial layer according to another embodiment, is provided including: (a) preparing for a p
+
-type or n
+
-type wafer as a substrate wafer; (b) forming a porous silicon layer having a predetermined thickness by anodic bonding the substrate wafer; (c) forming a porous silicon oxide layer by oxidizing the porous silicon layer; (d) forming a polysilicon seed layer on the porous silicon oxide layer; and (e) growing an epitaxial polysilicon layer on the porous silicon oxide layer.
In this method, the thickness of the porous silicon layer is preferably several micrometers to several tens of micrometers, and the steps (b) through (e) may be repeated.
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patent: 5569626 (1996-10-01), Kurtz
patent: 5598026 (1997-01-01), Kapoor
patent: 5616519 (1997-04-01), Ping
patent: 5639692 (1997-06-01), Teong
patent: 5932919 (1999-08-01), Schwalke
patent: 6077776 (2000-06-01), Cho
patent: 6126847 (2000-10-01), Thakur
Document ID: JP 2000332223 A, Author: J. Choi, H Geong, S Kang, K B Lee, Tittle: Multilayered wafer with thick sacrificial layer used, Source:Derwent—ACC-No. 2000-674016, pp: 1-5.
Choi Jae-joon
Jeong Hee-moon
Kang Sung-gyu
Lee Ki Bang
Burns Doane Swecker & Mathis L.L.P.
Niebling John F.
Samsung Electronics Co,. Ltd.
Stevenson André C
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