Method of inspecting semiconductor substrate

Details Method of inspecting semiconductor substrate Method of inspecting semiconductor substrate

2000-06-26

2001-10-09

Lebentritt, Michael (Department: 2824)

Semiconductor device manufacturing: process

With measuring or testing

C438S022000, C438S768000, C438S770000

Reexamination Certificate

active

06300147

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of inspecting a crystal defect or the like in a surface semiconductor layer of an SOI (silicon on insulator or semiconductor on insulator) substrate serving as a semiconductor substrate.
2. Description of the Background Art
An SOI substrate is generally manufactured by a bonding method or an SIMOX (separation by implanted oxygen) method.
In general, a surface silicon layer of an SOI substrate manufactured by the bonding method (hereinafter also referred to as “bonding SOI substrate”) has defects such as voids (hollow defects) referred to as COPs (crystal originated particles) and an oxygen precipitate intrinsic to a bulk substrate employed as the raw material as well as an oxygen precipitate and stacking faults induced in steps of manufacturing the SOI substrate.
In an SOI substrate manufactured by the SIMOX method (hereinafter also referred to as “SIMOX substrate”), on the other hand, thin regions or surface depressions, for example, may be caused on the surface silicon layer in manufacturing steps in addition to COPs intrinsic to a silicon substrate employed as the raw material. When carrying out an oxygen implantation step on the surface silicon layer of the silicon substrate still having particles and the like, portions located under such particles and the like are reduced in thickness as compared with the remaining portions of the same layer since the depth of oxygen ions implanted into these portions is smaller than that in the remaining portions. Further, the amount of the oxygen ions implanted into the portions located under the particles and the like is also smaller than that in the remaining portions. When performing heat treatment after oxygen implantation for forming an embedded oxide (silicon oxide) layer, therefore, the amounts of expansion of the silicon oxide vary with the different amounts of oxygen implantation and the regions located under the particles into which oxygen is implanted in a smaller amount, i.e., in which the silicon oxide expands by a smaller amount, are depressed with respect to the peripheral regions.
In addition to the aforementioned inconveniences caused in the surface silicon layer itself in the initial stage, inconveniences such as an oxygen precipitate and stacking faults resulting from each manufacturing process are induced in the surface silicon layer after the SOI substrate is introduced into the manufacturing steps.
A hydrofluoric acid dipping method (HF dipping method) is widely employed as a method of inspecting such inconveniences of the surface silicon layer. The conventional inspection method is now described.
FIG. 14A
is a longitudinal sectional view of an SOI substrate
1
not yet subjected to hydrofluoric acid dipping. As shown in
FIG. 14A
, the SOI substrate
1
comprises a substrate support part
30
, an embedded oxide layer
20
formed on the support part
30
and a surface silicon layer
10
formed on a surface
20
S of the embedded oxide layer
20
opposite to the support part
30
.
FIGS. 14A and 14B
typically illustrate COPs
51
a
to
51
d
(hereinafter also generically referred to as “COPs
51
”), an oxygen precipitate
52
and a locally thin region
53
as defects
50
which are initial inconvenient portions of the silicon layer
10
.
The SOI substrate
1
in the state shown in
FIG. 14A
is dipped in a hydrofluoric acid solution. Then, the hydrofluoric acid solution erodes the embedded oxide layer
20
through the COP
51
a
reaching the aforementioned surface
20
S from an exposed surface
10
S of the surface silicon layer
10
, as shown in FIG.
14
B. Thus, an embedded oxide layer
21
having an eroded part
21
a
under the COP
51
a
is defined. The density etc. of the COP
51
a
in the SOI substrate
1
can be recognized by observing the eroded part
21
a
. Thus, the hydrofluoric acid dipping method enables visual inspection of an SOI substrate with an optical microscope or the like by visualizing defects of sizes generally unobservable with an optical microscope.
The hydrofluoric acid dipping method, which visualizes the defect of the surface silicon layer
10
by eroding the embedded oxide layer
20
with hydrofluoric acid, is applicable to a part such as the COP
51
a
shown in
FIG. 14A
where the hydrofluoric acid solution can reach the embedded oxide layer
20
, i.e., a part not formed with the surface silicon layer
10
but exposing the embedded oxide layer
20
. In other words, only a defect reaching the surface
20
S of the embedded oxide layer
20
from the exposed surface
10
S of the surface silicon layer
10
can be detected with the hydrofluoric dipping method. More specifically, the hydrofluoric acid dipping method is inapplicable to inspection/evaluation of defects (hereinafter also generically referred to as “inner defects
5
ON”) such as (I) the COP
51
b
not reaching the surface
20
S, (II) the COP
51
c
not reaching the surface
10
S, (III) the COP
51
d
and the oxygen precipitate
52
reaching neither of the surfaces
10
S and
20
S and (IV) the thin region
53
shown in FIG.
14
A.
When forming a semiconductor element or the like on the surface silicon layer
10
in general, the thickness of the surface silicon layer
10
is reduced into a level suitable for the semiconductor element before the same is introduced into the manufacturing steps. If the inner defects
50
N can be inspected before reducing the thickness of the surface silicon layer
10
, therefore, reduction of the manufacturing yield can be prevented beforehand. In the hydrofluoric acid dipping method which is a conventional inspection method, however, the inner defects
50
N of the SOI substrate
1
cannot be sufficiently grasped in advance of introduction into the manufacturing steps. Even if the SOI substrate
1
is determined as non-defective through inspection by the hydrofluoric acid dipping method before introduction into the manufacturing steps, therefore, it is impossible to avoid such a situation that the inner defects
50
N appear after reducing the thickness of the surface silicon layer
10
to remarkably lower the manufacturing yield.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a method of inspecting a semiconductor substrate comprising steps of (a) preparing a semiconductor substrate comprising a dielectric layer and a semiconductor layer formed on the dielectric layer, whose surface opposite to the dielectric layer is exposed, (b) thermally oxidizing the exposed surface of the semiconductor layer for forming a thermal oxide film, (c) etching the thermal oxide film and (d) etching the dielectric layer through the thermal oxide film perforated in the step (c).
According to the first aspect, the thermal oxide film formed in the step (b) has a shape reflecting a defect when the semiconductor layer is defective, and the defect is transferred to the thermal oxide film and the semiconductor layer. The transferred part of the thermal oxide film can be opened by etching for exposing the dielectric layer in the step (c) by executing the aforementioned thermal oxidation so that the transferred part of the thermal oxide film comes into contact with the dielectric layer. The aforementioned defect can be transferred to the dielectric layer by eroding the dielectric layer through the aforementioned opening in the step (d). According to this inspection method, therefore, not only a COP reaching the dielectric layer from the exposed surface of the semiconductor layer but also an inner defect undetectable by the conventional hydrofluoric acid dipping method can be visualized and detected.
Consequently, the level of quality control can be improved as compared with the case of applying the conventional inspection method by utilizing this inspection method for quality control of a semiconductor substrate, for obtaining a semiconductor substrate of high quality. Further, the manufacturing yield and reliability of a semiconductor device can be improved by employing the semiconductor substrate of h

Affiliated with

Also associated with

Rating

Method of inspecting semiconductor substrate does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of inspecting semiconductor substrate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of inspecting semiconductor substrate will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2603972