JP2812382B2 - Method of monitoring buried diffusion layer of diffusion-coupled SOI substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for monitoring a buried diffusion layer of a diffusion-coupled SOI substrate.

[0002]

2. Description of the Related Art SOI substrate 47 having a buried diffusion layer
As shown in FIG. 4, p-type dopant (for example,
After forming an impurity doped layer 42 into which boron (boron) or an n-type dopant (for example, antimony) is introduced, it is bonded to a mirror wafer 43 (hereinafter, referred to as a base wafer) on which an oxide film 45 is formed by thermal oxidation or the like. ,
It is manufactured by performing a bonding heat treatment (also serving as diffusion (drive-in)) in an oxidizing atmosphere or an inert gas atmosphere.
At this time, the impurity doped layer 42 sandwiched between the bond wafer and the base wafer becomes a buried diffusion layer 44 due to diffusion of the introduced dopant in the layer 42.

In order to monitor the buried diffusion layer 44, the same impurity-doped layer 42 'as the impurity-doped layer 42 is formed on a mirror wafer 41' (the same as the mirror wafer 41), and then a bonding heat treatment of the SOI substrate is performed. When the same heat treatment as described above is performed, the diffusion layer 44 'after the heat treatment is different from the buried diffusion layer 44 according to the gas atmosphere at the time of the bonding heat treatment, and is not suitable as a monitor of the buried diffusion layer of the SOI substrate. .

When the bonding heat treatment atmosphere is an oxidizing atmosphere, the sheet resistance (ρs) is high and the diffusion depth (Xj) is deep due to the influence of oxygen (FIGS. 5 and 6). When the bonding heat treatment atmosphere is an inert gas atmosphere, the surface dopant concentration becomes low due to outward diffusion (FIG. 7).

[0005] Therefore, the diffusion layer monitor wafer is made of SO
Bonding must be performed in the same manner as the I-substrate. In order to measure the inspection value (sheet resistance, diffusion depth, etc.) of the diffusion layer, a mirror wafer having the bonded oxide film formed on one side (described above) (Corresponding to the base wafer 43).

[0006]

According to the above-mentioned prior art, in order to measure the inspection value of the diffusion layer, it is necessary to remove the bonded wafer on one side by grinding, polishing, etching or the like. Extremely bad.

The present invention has the above-mentioned problems of the prior art, that is, it is necessary to remove, by grinding, polishing, etching or the like, a mirror wafer having an attached oxide film on one side in order to measure a diffusion layer inspection value. It is an object of the present invention to solve the problem that the work efficiency is extremely poor, and to provide a method for easily and efficiently monitoring a buried diffusion layer of an SOI substrate with high accuracy.

[0008]

In order to solve the above-mentioned problems, in the method of monitoring a buried diffusion layer of a diffusion-coupled SOI substrate according to the present invention, an impurity-doped layer is formed on a mirror wafer and then the surface of the impurity-doped layer is formed. Was capped with a CVD film and then subjected to the same heat treatment as the bonding heat treatment of the SOI substrate to produce a monitor wafer. Using this monitor wafer, the embedded diffusion layer of the SOI substrate after the bonding heat treatment was monitored. .

In the case where the above-mentioned bonding heat treatment is performed in an oxidizing atmosphere, a CVD nitride film having a thickness of 50 nm is used as the cap CVD film.
m or more, or after forming a CVD oxide film, a CVD nitride film may be formed to a thickness of 50 nm or more, or a CVD oxide film may be formed to a thickness of 1000 nm or more.

When the above-mentioned bonding heat treatment is performed in an inert gas atmosphere, a CVD nitride film or a CVD oxide film is preferably formed to a thickness of 10 nm or more as a cap CVD film.
A VD oxide film and a CVD nitride film may be formed, and the entire CVD film thickness may be 10 nm or more.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIG. First, the mirror wafer 11
The boron doped layer 12 is formed on (CZ-N type). Next, the surface of the boron-doped layer 12 is coated with a 50 nm thick CVD.
Diffusion layer monitor wafer 14 capped with nitride film 13
Is prepared.

On the other hand, a boron-doped layer 12 '(formed in the same batch as the boron-doped layer 12) is formed on the bond wafer 11' (the same as the mirror wafer 11), and a 1 μm oxide film 16 is formed by thermal oxidation. ) To form an SOI substrate 17.

With respect to the diffusion layer monitor wafer 14 and the SOI substrate 17 manufactured by the above procedure, w
EtO ₂ , bonding heat treatment at 1100 ° C. for 120 minutes is performed.

Diffusion layer monitor wafer 1 after bonding heat treatment
Sheet resistance (ρs) and diffusion depth (Xj) of the diffusion layer 18 of No. 4 and the diffusion layer (buried heat treatment layer) 18 ′ of the SOI substrate
Was measured, and the comparison results are shown in FIGS.

As is clear from the results of FIGS. 2 and 3,
Sheet resistance (ρs) and diffusion depth (Xj) of the diffusion layer of the diffusion layer monitor wafer manufactured by the method of the present invention.
And the sheet resistance of the buried diffusion layer of the SOI substrate (ρ
s) and diffusion depth (Xj) show good correlation.

In the procedure of the above embodiment, the thickness 50
An experiment was performed in the same procedure as described above except that a CVD oxide film was formed and then a 50-nm thick CVD nitride film was formed instead of forming the CVD nitride film 13 with a thickness of 10 nm. Obtained.

In the procedure of the above embodiment, the thickness 50
An experiment was performed in the same procedure as described above except that a CVD oxide film was formed to a thickness of 1000 nm instead of forming the CVD nitride film 13 having a thickness of 10 nm.

In the procedure of the above embodiment, the thickness 50
An experiment was performed in the same procedure as described above except that a CVD nitride film was formed to a thickness of 10 nm and a bonding heat treatment was performed in an Ar atmosphere instead of forming the CVD nitride film 13 having a thickness of 10 nm. I got

In the procedure of the above embodiment, the thickness 50
An experiment was performed in the same procedure as described above except that a CVD oxide film was formed to a thickness of 10 nm and a bonding heat treatment was performed in an Ar atmosphere instead of forming a CVD nitride film 13 having a thickness of 10 nm. I got

In the procedure of the above embodiment, the thickness 50
Instead of forming the CVD nitride film 13 nm in thickness, a CVD oxide film and a CVD nitride film were formed in a thickness of 5 nm each, and the bonding heat treatment was performed in an Ar atmosphere. The same result as in the example was obtained.

[0021]

As described above, the diffusion layer of the diffusion layer monitor wafer manufactured by the method of the present invention is equivalent to the buried diffusion layer of the SOI substrate, and the diffusion layer monitor wafer has the SOI structure as in the prior art. Even without this, the buried diffusion layer of the SOI substrate can be monitored with high accuracy,
Since the inspection value (sheet resistance, diffusion depth, etc.) of the diffusion layer can be measured only by removing the surface CVD film, the following advantages are provided.

(1) Since treatment can be performed in the same batch as the bonding heat treatment of the SOI substrate, management and assurance of the buried diffusion layer of the SOI substrate after the bonding heat treatment can be easily performed.

(2) As in the prior art, the buried diffusion layer of the SOI substrate can be monitored without the need for the diffusion layer monitor wafer having the SOI structure, so that the operation of setting the diffusion conditions can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a procedure of an embodiment of a method of the present invention.

FIG. 2 is a graph showing a correlation between a sheet resistance (ρs) of a diffusion layer of a monitor wafer and a buried diffusion layer of an SOI substrate manufactured by the method of the present invention.

FIG. 3 is a graph showing the correlation between the diffusion depth (Xj) of the diffusion layer of the monitor wafer and the buried diffusion layer of the SOI substrate manufactured by the method of the present invention.

FIG. 4 is an explanatory view showing a general manufacturing procedure of an SOI substrate having a buried diffusion layer.

FIG. 5 is a graph showing a difference in sheet resistance (ρs) between a buried diffusion layer of an SOI substrate and a diffusion layer of a mirror wafer when heat treatment is performed in an oxidizing atmosphere.

FIG. 6 is a graph showing a difference in diffusion depth (Xj) between a buried diffusion layer of an SOI substrate and a diffusion layer of a mirror wafer when heat treatment is performed in an oxidizing atmosphere.

FIG. 7 is a graph showing a state of SO when heat treatment is performed in an inert gas atmosphere;
4 is a graph showing a difference in surface concentration between a buried diffusion layer of an I substrate and a diffusion layer of a mirror wafer.

[Explanation of symbols]

 41,11 'mirror wafer (bond wafer) 42,12' impurity doped layer 43,15 mirror wafer (base wafer) 44 18 'buried diffusion layer 45,16 oxide film 47,17 SOI substrate 11 mirror wafer 12 boron doped layer 13 CVD Nitride film 14 Diffusion layer monitor wafer 18 Diffusion layer

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masatake Katayama 2-3-1-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Semiconductor Isobe Research Laboratories (58) Field surveyed (Int. Cl. ⁶ , DB name) ) H01L 27/12

Claims (6)

(57) [Claims] 1. A method of monitoring a buried diffusion layer of a diffusion-coupled SOI substrate, comprising: forming an impurity-doped layer on a mirror wafer;
Capping with a film, and then performing the same heat treatment as the bonding heat treatment of the SOI substrate to produce a monitor wafer, and using this monitor wafer, monitoring the buried diffusion layer of the SOI substrate after the bonding heat treatment. Method. 2. When the bonding heat treatment is performed in an oxidizing atmosphere, a CVD nitride film is used as a cap CVD film.
The method according to claim 1, wherein the thickness is 0 nm or more. 3. The method according to claim 1, wherein when the bonding heat treatment is performed in an oxidizing atmosphere, a CVD nitride film is formed as a cap CVD film, and then a CVD nitride film is formed to a thickness of 50 nm or more. . 4. When the bonding heat treatment is performed in an oxidizing atmosphere, one CVD oxide film is used as a cap CVD film.
2. The method according to claim 1, wherein the thickness is set to 000 nm or more. 5. The method according to claim 1, wherein when the bonding heat treatment is performed in an inert gas atmosphere, a CVD nitride film or a CVD oxide film is formed as a cap CVD film to a thickness of 10 nm or more. 6. When the bonding heat treatment is performed in an inert gas atmosphere, a CVD oxide film and a CVD nitride film are formed as a cap CVD film, and the total CVD film thickness is 10 nm.
The method of claim 1 wherein: