Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2001-03-01
2003-05-06
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S062000, C438S406000, C438S455000, C438S458000
Reexamination Certificate
active
06558990
ABSTRACT:
This application claims Paris Convention priority of Japanese Application No. Hei 11-189100 filed Jul. 2, 1999 and International Application No. PCT/JP00/04376 filed Jun. 30, 2000, the complete disclosure of which are hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to a SOI (Silicon-On-Insulator) substrate including a silicon substrate and an insulating layer buried in the silicon substrate, and to a manufacturing method therefor. More particularly, the present invention relates to a SOI substrate manufactured by a SIMOX (Separation by Implanted Oxygen) technique and a manufacturing method therefor, as well as a semiconductor device utilizing the SOI substrate.
BACKGROUND ART
The SIMOX method as one of SOI substrate manufacturing methods is to bury an insulating layer into a silicon substrate. Concretely, as shown in FIG.
8
(
a
), the SOI substrate
1
is obtained by dosing oxygen ions at a higher concentration into a silicon substrate
2
, and thereafter annealing the silicon substrate
2
at a higher temperature to thereby form a buried silicon oxide layer
3
in a region at a predetermined depth from the surface of the silicon substrate
2
, in which a SOI layer
2
a
at the top surface side of the layer
3
is used as an active area.
However, cross-sectional end peripheries
3
a,
3
a
of the buried silicon oxide layer
3
of the SOI substrate
1
are not buried within the substrate, and are exposed at substrate side surfaces. Thus, upon etching during a semiconductor device manufacturing process such as by a hydrofluoric acid aqueous solution, the exposed end peripheries
3
a,
3
a
of the oxide layer
3
are removed by etching. As a result, those cross-sectional end surfaces
2
b
of the SOI layer
2
a
corresponding to an upper layer are brought into an overhung state like a canopy, as shown in FIG.
8
(
b
). Since these overhung portions
2
b,
2
b
have such a small thickness on the order of 0.05 to 0.3 &mgr;m, these portions are poor in mechanical strength and are chipped and/or peeled off during subsequent processes. Silicon fragments caused thereby become particles which adhere onto the surface of the SOI layer
2
a
as the active area. Devices formed on the SOI layer
2
a
having adhered particles lead to a cause of defects such as of patterning and in various deposition films, thereby problematically lowering a product yield.
As a SIMOX method to improve such a problem, there has been known a manufacturing method of a semiconductor substrate in which cross-sectional both end surfaces of a silicon substrate are coated by a resist, and oxygen ions are dosed from the exposed main surface of the silicon substrate into the interior of the silicon substrate to thereby form a buried silicon oxide layer within the silicon substrate (Japanese Patent Application Laid-Open No. HEI-129267(129267/1992)).
In the manufacturing method of a semiconductor substrate according to the aforementioned conventional SIMOX method, however, ion dosing is performed in a state where the resist exists at both end surfaces. Thus, those ions having higher energies also impinge the resist constituted of organic matters containing impurities such as metals, so that those organic matters struck out from the resist upon ion dosing tend to spatter to thereby adhere onto the surface of the SOI layer as the active area. This leads to such a problem that the surface of the SOI layer as the active area is contaminated by impurities such as metals.
Meanwhile, silicon substrates are sometimes provided with marking characters thereon, for identifying the substrates themselves. Those marking characters are mainly provided by laser irradiation, and as shown in
FIG. 2
, marking characters
16
a
(such as “ABC-XYZ”) are provided in a marking character area
16
at an end periphery of one of the main surfaces of a substrate
11
. In manufacturing a SOI substrate
1
shown in FIG.
9
(
b
) from a silicon substrate
2
provided with marking characters
4
as shown in FIG.
9
(
a
), oxygen ions I are dosed into the interior of the silicon substrate
2
similarly to the aforementioned SIMOX method, followed by an anneal processing at a higher temperature so as to form a buried silicon oxide layer
3
in a region at a predetermined depth from the surface of the silicon substrate
2
. The marking characters by laser irradiation generally reach a depth of about 1 &mgr;m from the substrate surface. Further, the buried silicon oxide layer is formed at a sub-micron depth from the substrate surface. Thus, when a SOI substrate is manufactured after providing marking characters at the end periphery of the main surface of the silicon substrate, or, when marking characters are provided at the end periphery of the main surface after the SOI substrate is manufactured in an unshown manner, the marking character portion and the buried oxide layer overlap with each other, thereby causing a problem of dust occurrence from the marking character portion.
It is therefore an object of the present invention to provide a manufacturing method of a SOI substrate, which prevents particles and impurities such as metals in a resist, from adhering onto a SOI layer as an active area, to thereby improve a product yield.
It is another object of the present invention to provide a manufacturing method of an SOI substrate for preventing dust occurrence due to marking characters.
It is yet another object of the present invention to provide a SOI substrate which noway causes dust occurrence due to marking characters.
It is still another object of the present invention to provide a semiconductor device adopting a SOI substrate having extremely lesser adherence such as of particles and impurities onto a SOI layer as an active area.
DISCLOSURE OF THE INVENTION
The invention of claim
1
as shown in
FIG. 1
is a manufacturing method of a SOI substrate comprising the steps of: forming an oxide film
12
at cross-sectional both main surfaces and both end surfaces of a silicon substrate
11
; forming a resist layer
13
on the oxide film
12
at cross-sectional both end surfaces of the substrate
11
; removing the oxide film
12
at those portions which are left from the covering of the resist layer
13
, to thereby expose the both main surfaces of the silicon substrate
11
; removing the resist layer
13
to thereby leave the oxide film
12
at the both end surfaces of the substrate
11
; dosing oxygen ions I into the substrate
11
from one of the exposed both main surfaces, followed by an anneal processing to thereby form an oxide layer
14
in a region at a predetermined depth from the one main surface of the substrate
11
; and removing the oxide film
12
left on the both end surfaces of the substrate
11
.
According to the invention of claim
1
, oxygen ions I are dosed into the exposed silicon substrate
11
in a state where the resist layer
13
is removed from the oxide film
12
, and the anneal processing is conducted. Thus, there can be avoided adherence of impurities such as metal into the SOI layer
11
a
as an active area. Further, since cross-sectional both end surfaces of the silicon substrate
11
are coated by the oxide film
12
upon ion dosing, dust occurrence from the end surfaces of the SOI layer
11
a
as the active area can be avoided during the subsequent device manufacturing process so that contamination due to particles onto the surface of the device is avoided.
The invention of claim
2
as shown in
FIGS. 4 and 5
is a manufacturing method of a SOI substrate of claim
1
, wherein the silicon substrate
11
includes a marking character area
16
for carrying marking characters for identifying the substrate
11
at an end periphery of the one of the both main surfaces of the substrate
11
, and wherein the resist layer
13
covers the marking character area
16
, when the resist layer
13
is formed on the oxide film
12
at the both end surfaces of the substrate
11
.
According to the invention of claim
2
, since the resist layer
13
covers the marking character area
16
, the marking charact
Iwamatsu Toshiaki
Katakura Takashi
Naruoka Hideki
Takamatsu Masaru
Elms Richard
Luu Pho M.
Mitsubishi Materials Silicon Corporation
Reed Smith LLP
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