JPH10144698A - Silicon wafer and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reducing oxygen concentration in a surface layer of a boron-containing silicon wafer while maintaining boron concentration in its surface layer, and to provide a silicon wafer having a boron-containing non-oxygen layer, substantially not including oxygen products, as its front surface, and a silicon wafer having an epitaxial layer on the surface of a boron- containing non-oxygen layer. SOLUTION: Annealing is performed by using a silicon wafer, manufactured by Czochralski method, with boron as dopant, in an argon atmosphere at 800-1300 deg.C for a minute or longer. The silicon wafer manufacturing method performs the annealing to selectively diffuse oxygen outwardly, from oxygen and boron included in the front surface of the wafer. Further, the silicon wafer manufactured by this method has a boron-containing non-oxygen layer as its front surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a silicon wafer used for manufacturing semiconductor devices and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Single crystal silicon pulled up by the Czochralski method generally contains oxygen. This oxygen grows as an oxygen precipitate during the device process.

[0003] Oxygen precipitates (BMD) existing in the bulk portion of a wafer are useful as a carrier of the intrinsic gettering effect if the size and density are appropriately controlled.

However, the BMD existing on the surface of the wafer
Is not preferred because it causes device defects and is taken into the epitaxial layer as an impurity when the epitaxial layer is formed.

[0005]

Therefore, the present applicant has
A method has been proposed in which heat treatment is performed in a hydrogen atmosphere to outward diffuse oxygen in the wafer surface layer to form an oxygen-free (defect-free) layer, and then perform device processing or epitaxial growth.

However, when heat treatment is performed in a hydrogen atmosphere, not only oxygen but also the dopant is diffused outward, and a steep distribution of the dopant may not be obtained.

For example, P contained in a silicon wafer
Boron is used as the type impurity. When a silicon wafer using boron as a dopant is annealed in a hydrogen atmosphere, not only oxygen but also boron in the surface layer of the wafer is diffused out together. For this reason, it was difficult to realize a steep boron distribution near the wafer surface layer.

If the heat treatment time in a hydrogen atmosphere is reduced,
Outward diffusion of boron can be suppressed. However, in that case, outward diffusion of oxygen was insufficient, and a high-purity epitaxial layer could not be formed.

In view of the problems of the prior art described above, the present invention provides a method for reducing the oxygen concentration in the surface layer of a boron-containing silicon wafer while maintaining the boron concentration in the surface layer, and an oxygen deposition method. It is an object of the present invention to provide a silicon wafer in which a boron-containing oxygen-free layer substantially free of substances is formed on a surface layer portion, and a silicon wafer in which an epitaxial layer is formed on the surface of the boron-containing oxygen-free layer.

[0010]

According to the first invention of the present application, a silicon wafer manufactured by the Czochralski method and using boron as a dopant is used at 800 ° C. in an argon atmosphere.
A gist of the present invention is a method for producing a silicon wafer, wherein annealing is performed at 1300 ° C. for 1 minute or more, and oxygen out of oxygen and boron contained in the wafer surface layer is selectively diffused outward.

According to a second invention of the present application, in a silicon wafer manufactured by the above method, a boron-containing oxygen-free layer is formed on the surface layer of the wafer, and the boron concentration is 1-4 × 10 ¹⁸ cm.
^-3 , a silicon wafer characterized in that the oxygen precipitate (BMD) is substantially zero.

[0012] The third invention of the present application is directed to a silicon wafer characterized in that an epitaxial layer is formed on the surface of a boron-containing oxygen-free layer in the silicon wafer.

[0013]

Embodiments of the present invention will be described below in detail.

The present invention utilizes the fact that the outward diffusion of boron contained as a dopant in a silicon wafer depends on the annealing atmosphere.

That is, the present inventors have conducted intensive studies and found that when a silicon wafer containing boron is annealed in an argon atmosphere, boron hardly diffuses outward, and only oxygen selectively diffuses outward. I found something to be done. In other words, it has been found that by annealing a boron-containing silicon wafer in an argon atmosphere, only the oxygen in the surface layer of the wafer can be outwardly diffused without substantially changing the boron distribution.

The present inventors have considered the reason why boron contained in a wafer diffuses in a hydrogen atmosphere and hardly diffuses in an argon atmosphere as follows.

The atomic radius of boron is 75% of that of silicon atoms.
And the change in volume of the silicon lattice with boron atoms at the silicon lattice position is approximately −6 (± 2 × 10 ^24).
cm ^-3 ). Therefore, it is considered that the chemical free energy due to the concentration difference is offset by the image force due to the change in the volume of the boron atom silicon lattice near the surface. As a result, when the foreign atoms at the silicon lattice position are larger than the silicon atoms, it is expected that the limit conditions governing the outward diffusion of boron will be different.

Whether or not oxygen can be diffused outward is governed by the degree of oxygen saturation in the silicon wafer and the boundary conditions of the wafer at a constant heat treatment temperature, and the oxygen distribution due to outward diffusion is represented by a normal error function.

The present invention is particularly advantageous when applied to epitaxial technology. Generally, when an epitaxial process is performed on a silicon wafer, a hydrogen-containing gas is used. However, as described in the section of the prior art, when heat treatment is performed in a hydrogen atmosphere, not only oxygen but also boron in the surface layer of the wafer is diffused outward. When the heat treatment time is long, a steep dopant (boron) distribution cannot be obtained.

Therefore, in the present invention, the silicon substrate is first heat-treated in an argon gas atmosphere to diffuse only oxygen outward without substantially changing the boron concentration to form an oxygen-free layer (DZ layer) on the surface layer. .

Thereafter, if an epitaxial treatment is performed, an epitaxial layer containing almost no oxygen can be formed. And a silicon epitaxial wafer having a steep boron concentration distribution can be realized.

In the present invention, the heat treatment temperature is set at 800 to 1300 ° C.
The reason is that when the processing temperature is lower than 800 ° C., diffusion of oxygen is too slow, and when the processing temperature is higher than 1300 ° C., a burden is imposed on the quartz furnace core tube and the life is shortened. is there. The reason why the heat treatment time is set to 1 minute or more is to sufficiently diffuse oxygen.

The preferred boron concentration of the boron-containing oxygen-free layer is from 1 × 10 ¹⁸ atoms / cm ³ to 1 × 10 ¹⁹ atoms.
s / cm ³ , and the preferred thickness of the boron-containing anoxic layer is 10 to 30 μm.

The boron concentration and the thickness of the boron-containing anoxic layer are limited to the above ranges in order to obtain a sharp boron distribution.

If the BMD concentration of the boron-containing oxygen-free layer exceeds the above range, a high-quality device cannot be formed. Also, when an epitaxial layer is formed on the surface, oxygen is taken in, so that a high-purity epitaxial layer cannot be formed.

The oxygen concentration and the thickness of the boron-containing oxygen-free layer can be adjusted to desired values by appropriately setting the annealing temperature and the annealing time within the above ranges.

Hereinafter, Embodiment 1 of the present invention will be described.

The sample used in Example 1 had a boron concentration of 3.5.
× 10 ¹⁸ cm ^-3 , oxygen concentration 1.3 × 10 ¹⁸ cm ^-3 , (1
00), a CZ silicon wafer. After washing this sample as standard, a heat treatment was performed at 1200 ° C. for 2 hours in an argon atmosphere. And SIM (secondary ion)
The distribution of boron and oxygen in the depth direction was measured by mass spectrum), and is shown in FIG.

On the other hand, the same silicon wafer as in Example 1 was used as Comparative Example 1 except that the heat treatment was not performed, and the distributions of boron and oxygen in the depth direction were measured in the same manner.

As can be seen from FIG. 1, in Example 1 where the treatment was performed in an argon atmosphere, the boron concentration was hardly reduced and the boron distribution was not substantially changed. On the other hand, oxygen was diffused outward, and the oxygen concentration within a range of 4 μm from the surface was approximately 0.2 × 10 ¹⁷ cm ⁻³ .

On the other hand, in Comparative Example 1, not only the oxygen concentration but also the boron concentration were significantly reduced.

[0032]

According to the present invention, a silicon wafer having a boron-containing oxygen-free layer on its surface can be easily manufactured.

When the silicon wafer is subjected to an epitaxial treatment, a silicon wafer having a steep boron concentration can be obtained.

Using a high quality silicon wafer manufactured as described above, it is possible to manufacture a highly integrated device with a high yield.

The present invention is not limited to the above embodiment. The present invention relates to heteroepitaxial (e.g., Si-Ge
System).

[Brief description of the drawings]

FIG. 1 is a graph showing the state of boron distribution and oxygen distribution before and after heat treatment in an example of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshio Kirino 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. (72) Inventor Hiroshi Shirai 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. In-house (72) Inventor Kenro Hayashi 30 Soya, Hadano-shi, Kanagawa Prefecture Toshiba Ceramics Co., Ltd.

Claims (4)

[Claims] A silicon wafer manufactured by the Czochralski method and using boron as a dopant is annealed at 800 ° C. to 1300 ° C. for 1 minute or more in an argon atmosphere to obtain oxygen and boron contained in the surface layer of the wafer. A method of manufacturing a silicon wafer, wherein oxygen is selectively diffused outward. 2. Using a silicon wafer manufactured by the Czochralski method and using boron as a dopant, annealing is performed at 800 ° C. to 1300 ° C. for 1 minute or more in an argon atmosphere to obtain oxygen and boron contained in the wafer surface layer. A method of manufacturing a silicon wafer, wherein oxygen is selectively outwardly diffused, and thereafter, epitaxial treatment is performed. 3. A silicon wafer manufactured by the method according to claim 1, wherein a boron-containing oxygen-free layer is formed on the surface of the wafer, and the boron concentration is 1 to 4 × 10 ¹⁸ atom.
ms / cm ³ , and a substantially zero oxygen precipitate (BMD). 4. The silicon wafer according to claim 3, wherein an epitaxial layer is formed on the surface of the boron-containing oxygen-free layer.