JPH10125603A - Working of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent contamination of an epitaxial wafer and to improve its life time value top the level of a mirror wafer. SOLUTION: A method for work a semiconductor wafer comprises a step S1 of depositing a silicon film 9 on a susceptor 6 for taking contaminants D into the silicon film 9, a step S2 of removing the silicon film 9 containing the contaminates D, a step S3 of repeating the above at last once, a step S4 of forming a silicon coating on a supporting surface 6a, and a step S5 of applying an epitaxial growth treatment to the semiconductor wafer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for processing a semiconductor wafer, and more particularly to a technique effective for preventing contamination of a semiconductor wafer having a silicon thin film formed by epitaxial growth.

[0002]

2. Description of the Related Art Along with higher integration, higher performance, and larger diameter of devices, epitaxial wafers in which a silicon thin film is grown while inheriting the crystallinity of an underlying substrate are required to have higher precision and larger thickness and resistivity. Various requirements are imposed, such as caliber and cost reduction. One of such demands is to reduce pollution. That is, if there is contamination in the semiconductor wafer, the lifetime (= the average time during which electrons or holes in the semiconductor are maintained in a charged state) is shortened, and carriers are immediately recombined, and carriers are recombined. This is because the concentration is greatly reduced.

As an example describing in detail the epitaxial growth of a semiconductor wafer, see, for example, “Silicon LSI and Chemistry” (published by Dainippon Tosho Co., Ltd.)
Issued on March 10) and P175 to P177.

[0004]

However, an epitaxial wafer on which a silicon thin film is grown has a problem in that surrounding contaminants are incorporated into the crystal during the growth process.
The lifetime value is much lower than that of a mirror-finished mirror wafer. Specifically, in the case of a p-type semiconductor wafer, the lifetime value of the mirror wafer is 300
On the other hand, the lifetime value of the epitaxial wafer is only about 1/30 of that, ie, about 10 μs.

[0005] Such adverse effects due to the contamination of the semiconductor wafer have been a problem not only in the case of epitaxial growth but also in the whole wafer process.

An object of the present invention is to provide a technique capable of preventing contamination of a semiconductor wafer in a wafer process.

[0007] The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0008]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, in the method of processing a semiconductor wafer according to the present invention, a step of depositing a silicon film on a holding surface of a susceptor holding a semiconductor wafer to take in contaminants of the susceptor into the silicon film, , A step of repeating these steps one or more times, a step of applying silicon coating on the holding surface, and a step of mounting a semiconductor wafer on the holding surface and performing a predetermined process on the semiconductor wafer after the silicon coating step. It is characterized by including.

In this semiconductor wafer processing method, in the processing of a semiconductor wafer, a silicon thin film is formed on a mirror wafer by epitaxial growth to obtain an epitaxial wafer. The material of the susceptor is carbon or S
An iC coating can be applied.

According to the above-described means, wafer contamination in the wafer process in which the semiconductor wafer is held on the susceptor is prevented. Thus, for example, in the case of epitaxial growth, contamination of the epitaxial wafer is largely prevented, and its lifetime value can be raised to a level equivalent to that of the mirror wafer.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, the same members are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is a schematic view showing an epitaxial growth apparatus for forming an epitaxial thin film on a semiconductor wafer.
3 is a flowchart showing a processing procedure of the semiconductor wafer in the epitaxial growth apparatus of FIG. 1, and FIGS. 3 to 5 are graphs showing lifetime measurement results of the semiconductor wafer obtained by the flow of FIG. 2.

The epitaxial layer shown in FIG.
i ". ) The growth apparatus includes a bell jar 1 made of quartz or metal in which SiH ₄ , SiH ₂ Cl ₂ , SiHCl ₃ ,
A reaction gas G ₁ such as SiCl ₄ is introduced, and a silicon thin film identical to the base substrate is grown on the semiconductor wafer 2 by utilizing a chemical reaction in a high-temperature gas phase of 1000 ° C. or more under normal pressure or reduced pressure of several hundred Torr. Batch type vertical vapor phase E
Pi growth device.

At the center of a reaction chamber 4 formed by the base 3 and the bell jar 1, a nozzle 5 made of, for example, quartz is provided.
Is installed so as to protrude from the base 3, and the above-described reaction gas G ₁ is introduced from the nozzle 5 into the reaction chamber 4.

A disk-shaped carbon susceptor 6 coated with silicon carbide (SiC) is provided so as to surround the nozzle 5, and the semiconductor wafer 2 is held on a holding surface 6a. A work coil 7 for inductively heating the semiconductor wafer 2 by flowing a high-frequency current is disposed under the susceptor 6 so as to be covered with a quartz cover 8, and the semiconductor wafer 2 is heated by heat conduction through the susceptor 6. Is done.

[0017] Incidentally, the base 3 for discharging the reaction gas G ₁ after the silicon thin film growth by introducing a purge gas G ₂ in a room to the outside, a purge gas introduction hole 3a and an exhaust hole 3b is opened.

Semiconductor wafer 2 by this Epi growth apparatus
Will be described with reference to FIG.

First, a gas containing silicon atoms is introduced into the reaction chamber 4 heated to a high temperature of, for example, 1000 ° C. or more, and a silicon film 9 is deposited on the holding surface 6a of the susceptor 6 (S ₁ ). Specifically, for example, when a polycrystalline silicon film is formed, SiH ₄ or Si ₂ H ₆ (during thermal decomposition), SiHCl ₃ or SiH ₂ Cl ₂ (during a hydrogen reduction reaction) is converted into, for example, silicon oxide. When forming a film, oxygen, carbon dioxide, nitrogen oxide, and water vapor are further introduced. Then, as shown in the figure, the contaminant D existing in the susceptor 6 is diffused and taken into the silicon film 9 (P ₁ ).

After the silicon film 9 is formed, it is removed by high-temperature gas etching utilizing a chemical reaction of, for example, HCl or H ₂ (S ₂ ). As a result, the contaminants taken into the silicon film are also removed (P ₂ ). The silicon coating 9 may be removed by reactive ion etching, plasma etching, or the like.

Here, the contaminant D of the susceptor 6 is not sufficiently diffused / removed by one cleaning / depositing / etching of the silicon film 9. That is, as shown in FIG. 3, in the case of a p-type Epi wafer, the lifetime value when cleaning of the susceptor 6 is performed only once (the lifetime value increases as the degree of contamination decreases as described above). ) Is about 200 μs, but the step is increased to 250 μs when performed twice, and further improved as the number of times is increased (about 300 μs, which is the same level as the mirror wafer in six times). This is the susceptor 6
If the cleaning is performed a plurality of times, it means that the contamination of the Epi wafer is greatly improved. Therefore,
The process of depositing the silicon film 9 and taking in and removing the contaminant D is repeated twice or more (S ₃ ). In FIG. 3, "REF" indicates a lifetime value of a mirror wafer as a comparative example.

After the contaminants D of the susceptor 6 are sufficiently removed by performing the cleaning a plurality of times as described above, a silicon coating 9 is formed on the holding surface 6a, and the silicon coating is applied (S ₄ ). As a result, the contaminant D
Even if a little remains, it is trapped and its separation is prevented, and the surface becomes extremely clean (P ₄ ).

After that, the semiconductor wafer 2 is mounted and epitaxial growth is performed (S ₅ , P ₅ ), and the silicon thin film inheriting its crystallinity is transferred to the mirror wafer in a state where the contaminant D is prevented from being detached from the susceptor 6. To form an Epi wafer.

Here, Ep depending on the presence or absence of the silicon coat
Fig. 4 shows the evaluation results of the lifetime value of the i-wafer (p-type).
FIG. 5 shows the transition of the lifetime value of the Epi wafer (n-type) depending on the number of start batches. In FIG. 4, the number n of samples of the Epi wafer is four in each case, and the number n of samples of the mirror wafer as the comparative example is two.

As shown in FIG. 4, the lifetime is 247 .mu.s for the Epi wafer when the susceptor 6 is not coated with silicon, whereas it is significantly improved to 358 .mu.s for the Epi wafer when silicon coated. This value was close to 397 μs of the mirror wafer shown as a comparative example. Further, as shown in FIG. 5, even when the number of batches to be started increased, a lifetime value equivalent to that of the mirror wafer was always obtained. Therefore, once the above-described series of processes of cleaning and coating is performed, a high lifetime value can be maintained for a long period of time in Epi growth.

As described above, according to the present embodiment, the silicon coating is performed on the susceptor 6 after repeating the step of depositing and etching the silicon film twice or more.
Thereafter, contamination of the Epi wafer created by mounting the semiconductor wafer 2 on the holding surface 6a is largely prevented. This makes it possible to improve the lifetime value of the Epi wafer to a level equivalent to that of the mirror wafer.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the embodiment, and various modifications may be made without departing from the gist of the invention. It goes without saying that it is possible.

For example, in the present embodiment, the susceptor 6
After the cleaning / silicon coating is performed, the semiconductor wafer 2 is subjected to an Epi growth process. However, when a silicon oxide film is formed on the semiconductor wafer 2 or when dry etching is performed, the semiconductor wafer 2 is subjected to a process other than the Epi growth. Can be applied to the technique of performing the above processing.

Therefore, the susceptor in the present invention is a general term for a wafer holder, and is not limited to the susceptor of the Epi growth apparatus.

[0030]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) In other words, according to the semiconductor wafer processing method of the present invention, the susceptor is coated with silicon after repeating the silicon film deposition / etching process twice or more times. Wafer contamination in the holding wafer process is prevented.

(2) Therefore, when the present invention is applied to the epitaxial growth technique, contamination of the epitaxial wafer is largely prevented, and its lifetime value can be raised to the same level as that of the mirror wafer.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an epitaxial growth apparatus for forming an epitaxial thin film on a semiconductor wafer.

FIG. 2 is a flowchart showing a processing procedure of a semiconductor wafer in the epitaxial growth apparatus of FIG.

FIG. 3 is a view showing a semiconductor wafer obtained by the flow shown in FIG. 2;
It is a graph which shows the measurement result of the lifetime value by the number of cycles of silicon deposition and etching.

FIG. 4 shows a semiconductor wafer obtained by the flow of FIG.
It is a graph which shows the measurement result of the lifetime value by the presence or absence of a silicon coat.

FIG. 5 shows a semiconductor wafer obtained by the flow of FIG.
FIG. 6 is a graph showing a change in a lifetime value after cleaning.

[Explanation of symbols]

1 bell jar 2 semiconductor wafer 3 base 3a purge gas introduction hole 3b exhaust hole 4 reaction chamber 5 nozzle 6 silicon film susceptors 6a holding surface 7 work coil 8 quartz cover 9 D contaminants G ₁ reaction gas G ₂ purge

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisashi Arakawa 3-3-2 Fujibashi, Ome-shi, Tokyo Inside Hitachi Tokyo Electronics Co., Ltd. No. 1 Semiconductor Company, Hitachi, Ltd.

Claims (3)

[Claims] 1. A method for processing a semiconductor wafer, comprising the following steps (a) to (e). (A) depositing a silicon film on a holding surface of a susceptor holding a semiconductor wafer to incorporate contaminants of the susceptor into the silicon film; (b) removing the silicon film containing the contaminants; (C) The above (a)
A step of repeating the step and the following step (b) one or more times, (d) after the step (c), applying a silicon coating to the holding surface, and (e) after the step (d), Mounting the semiconductor wafer on the holding surface and subjecting the semiconductor wafer to a predetermined process; 2. The method for processing a semiconductor wafer according to claim 1, wherein the semiconductor wafer is provided in the step (e).
A method for processing a semiconductor wafer, wherein a silicon thin film is formed on a mirror wafer by epitaxial growth to form an epitaxial wafer. 3. The method for processing a semiconductor wafer according to claim 1, wherein the material of said susceptor is carbon.