JPH10308387A - Etching of silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a defect in the surface of a silicon wafer in an etching treatment by a method wherein an etching process is constituted of the etching treatment and a rinsing treatment for controlling an etching and an oxidizing material is added to a rinsing liquid, which is used for the rinsing treatment, to form an oxide film on the surface of the silicon wafer. SOLUTION: A silicon wafer 1 is cut out from a silicon ingot and the cut-out silicon wafer 1 is put in a state that it is removed damage inflicted on its surface by an etching treatment. An oxidizing material, such as ozone, is added to a rinsing liquid, which is used for a rinsing treatment, to form an oxide film 2 on the surface of the wafer 1. While the wafer 1 is stored, a contaminant 3, such as a foreign substance, results in adhering on the film 2 formed on the surface of the wafer 1. Thereby, the generation of a defect in the surface of the wafer 1 can be inhibited and the enhancement of the semiconductor device characteristics, yield and the like of the wafer can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for etching a silicon wafer. More specifically, the present invention relates to a method for etching a silicon wafer capable of obtaining a stable silicon wafer surface.

[0002]

2. Description of the Related Art In a manufacturing process of a silicon wafer, particularly, an etching process performed after a silicon wafer is subjected to a lapping process and before a polishing process is to maintain a flat shape while removing damage on the silicon wafer surface. It is becoming an important process. In particular, as the miniaturization of semiconductor devices progresses, the required flatness of the silicon wafer becomes more and more severe, and it is difficult to control the flatness only by the polishing process. Processing is becoming necessary. In order to satisfy these, not only the composition of the etching solution but also the etching apparatus itself have been improved in the etching process.

However, since the purpose of the etching process is to erode the surface of the silicon wafer, a sufficient oxide film is not formed on the surface of the silicon wafer immediately after the etching, in view of the characteristics of silicon. The surface exhibits hydrophobicity. Immediately after the etching, a rinsing process is performed in order to suppress the progress of the etching, and pure water is conventionally used for the rinsing process.
Since pure water has no oxidizing power, the surface of the silicon wafer is kept hydrophobic. In such a state, since the surface of the silicon wafer is activated, foreign matter easily adheres to the surface, and once the foreign matter adheres, the foreign matter comes into direct contact with the silicon wafer and is removed in the subsequent cleaning or the like. It will be difficult to do. If the rinsing is insufficient, or if the subsequent drying is insufficient, the rinsing liquid adheres to the silicon wafer surface in the form of water droplets. Then, when water droplets adhere to the hydrophobic surface of the silicon wafer and this state is maintained, a mark is left as a water mark after air drying.

[0004] This water mark is not only a trace but also a water droplet absorbs oxygen in the atmosphere and partially causes abnormal oxidation, and then the APM liquid (ammonia / hydrogen peroxide diluted with ultrapure water). Cleaning solution)
It cannot be removed. Such defects (defects) are often caused not only in a silicon wafer manufacturing process but also in a semiconductor device process.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and the present invention provides a method for etching a silicon wafer capable of preventing defects from occurring during etching. It is intended to provide.

[0006]

That is, according to the present invention, there is provided a method of etching a silicon wafer, which comprises subjecting a silicon wafer to a lapping step and then to an etching step before a polishing step. And a rinsing process for stopping the etching, wherein an oxide film is formed on the surface of the silicon wafer by adding at least an oxidizing substance to a rinsing liquid used for the rinsing process. , Are provided. In the present invention, in the etching step, an oxidizing substance such as ozone, a neutralizing agent, a surfactant, or a wetting agent is added to a rinsing liquid used for stopping the etching. Oxidation can protect the surface of the silicon wafer with a stable oxide film and prevent the occurrence of defects.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
First, the manufacturing process of a silicon wafer is roughly described.
A silicon ingot made of silicon single crystal is sequentially subjected to a slicing step, a lapping step, an etching step, a polishing (polishing) step, and a cleaning step to obtain a product silicon wafer, which is then used in a semiconductor device manufacturing process. Moved.

The etching step includes an etching process and a rinsing process for stopping the etching. The etching process is performed in order to remove the damage from the surface of the silicon wafer after the lapping process due to slurry or the like. Specifically, hydrofluoric acid (HF), nitric acid (HNO3), acetic acid (CH3C
This is a step of removing a damaged layer on the surface of the silicon wafer using a mixed acid of OOH) and water.

The rinsing process is performed after the etching process. Usually, quick dump rinsing in which high-speed supply and high-speed effluent of pure water are repeated several times, or pure water is supplied from a bottom to a tank containing a silicon wafer for a certain period of time to overflow. For example, an overflow rinse for removing the acid on the silicon wafer while applying the pressure is applied. According to the present invention, in the rinsing process, at least an oxidizing substance such as ozone is added to a rinsing liquid used to suppress etching, and an oxide film is formed on the silicon wafer surface during the rinsing process. Further, in the present invention, it is possible to add a neutralizing agent for stopping the etching reaction to the rinsing liquid or to add a surfactant or a wetting agent to minimize the stain (stain) on the silicon wafer surface. preferable.

The type of the oxidizing substance used for the rinsing treatment in the etching step is not limited, and ozone, hydrogen peroxide, a mixture of ammonium hydroxide and hydrogen peroxide, nitric acid, sulfuric acid and the like may be used. Can be. The concentration of an oxidizing substance such as ozone is 0.5 to 40 pp in pure water.
m is effective in the dissolved form, but from an economic viewpoint,
2 to 20 ppm is desirable. There are various known ozone generation methods, and any of them can be applied. There is no particular limitation on temperature. The types of the neutralizing agent, surfactant, and wetting agent added to the rinsing solution are not particularly limited, and conventionally known ones can be used.

Next, the present invention will be described in more detail based on the illustrated embodiment. FIG. 1 is a schematic diagram showing the state of adhesion of foreign matter in the present invention and a conventional etching method. Here, 1 is a silicon wafer, and a) shows a state immediately after being cut out from a silicon ingot. FIG. 2B shows a state in which the cut-away silicon wafer 1 has been subjected to etching to remove surface damage.

C) The silicon wafer 1 after the rinsing process
In the case of pure water, no oxide film still exists, but when rinsed with pure water to which an oxidizing substance such as ozone is added, the oxide film 2 is formed. To indicate that d) shows the state of attachment of the contaminants 3 such as foreign substances during storage of the silicon wafer 1. In the case of pure water rinsing, the contaminants 3 and the like are directly attached to the silicon wafer 1.

FIG. 2 shows the effect when ozone is added to the rinsing water used for the rinsing process. As is clear from the results of FIG. 2, it is found that the occurrence of silicon wafer defects is reduced when ozone is added as compared with the rinsing treatment using pure water alone. In addition, the defect rate was obtained by detecting a defect on the surface of the silicon wafer by visual inspection under condensing light.

[0014]

As described above, according to the present invention,
In the rinsing process of the etching step, an oxide film is formed on the surface of the silicon wafer by adding at least an oxidizing substance such as ozone to the rinsing liquid, so that generation of defects on the surface of the silicon wafer can be suppressed. There is a remarkable effect that characteristics, yield, and the like can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the state of adhesion of foreign matter in the present invention and a conventional etching method.

FIG. 2 is a graph showing an effect when ozone is added to rinse water used for a rinsing process.

[Explanation of symbols]

 1. Silicon wafer, 2. Oxide film, 3. Contaminant.

Continuation of the front page (72) Inventor Yoshihiro Suzuki 11-2 Kiyohara Industrial Park, Utsunomiya City, Tochigi Prefecture (72) Inventor Kiyotari Ikeda 11-2 Kiyohara Industrial Park, Utsunomiya City, Tochigi Prefecture MMC Co., Ltd.

Claims (4)

[Claims] 1. A method for etching a silicon wafer, comprising subjecting the silicon wafer to a lapping process and then performing an etching process before a polishing process, wherein the etching process comprises an etching process and a rinsing process for stopping the etching. A method for etching a silicon wafer, characterized in that an oxide film is formed on a surface of the silicon wafer by adding at least an oxidizing substance to a rinsing liquid used for a rinsing process. 2. The etching method according to claim 1, wherein the oxidizing substance is ozone, hydrogen peroxide, a mixture of ammonium hydroxide and hydrogen peroxide, nitric acid, or sulfuric acid. 3. The etching method according to claim 1, wherein a neutralizing agent is further added to the rinsing liquid. 4. The etching method according to claim 1, wherein a surfactant or a wetting agent is further added to the rinsing liquid.