JP3356582B2 - Silica glass jig and processing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for heat treatment of a semiconductor made of silica glass manufactured by an electrofusion method, and more particularly to a jig for heat treatment of a semiconductor element which does not deteriorate the dielectric breakdown voltage of an oxide film or the lifetime of a silicon wafer. It relates to a silica glass jig.

[0002]

2. Description of the Related Art Components such as machines, devices, containers, and tubes used in a semiconductor manufacturing process can withstand use at high temperatures and, under any conditions, react with semiconductors or even trace semiconductors. It is required to be formed of a material that does not emit a substance that contaminates. Silica glass is a material that satisfies such requirements, and in particular, highly heat-resistant silica glass obtained by electromelting crystalline silicon dioxide powder has been used as a material for jigs such as furnace core tubes for diffusion furnaces and wafer boats. Was. Even if the high purity and high heat resistance silica glass is used at a temperature exceeding 1000 ° C., a trace amount of impurities contained therein, particularly heavy metal impurities such as iron, chromium, nickel and copper are released, and the semiconductor element is May be contaminated. This has been spotlighted as a major problem in the semiconductor manufacturing process that is becoming increasingly clean. To solve this problem, OH is used to prevent diffusion and release of heavy metal impurities, which are a source of contamination of semiconductor devices, particularly silicon wafers.
Silica glass jigs doped with groups have been proposed. However, the OH group-doped silica glass jig has a surface OH group content of only 200 ppm and is not a jig capable of sufficiently preventing the diffusion and release of heavy metal impurities. Therefore, the innermost layer of the jig is 1000-2000 ppm
For example, Japanese Patent Application Laid-Open No. Hei 6-191873 has proposed a multilayer-structured silica glass jig in which an OH group is contained and the outer layer is formed of high-purity quartz glass. This multilayer silica glass body is suitable as a material for forming a member having a simple structure such as a furnace core tube, but has a complicated structure like a wafer boat, and has a groove for mounting a silicon wafer. The required jigs were difficult to process and were not fully satisfactory. In addition, the multilayer silica glass body has a problem in that a difference in viscosity occurs due to a difference in OH group content between layers, which causes distortion at an interface.

[0003]

To solve the above problems, the inventors of the present invention have conducted intensive studies. As a result, a jig made of silica glass manufactured by an electro-fusion method and doped with an OH group is described as follows. Since the heat resistance is little reduced, the processing is easy, and there is an effect of preventing diffusion of metal impurities, it was concluded that the jig is most suitable as a jig for heat treatment of a semiconductor element. As a result of the superposition, OH groups in the silica glass, when a reducing gas is present, reduce the effect of preventing heavy metal impurities from diffusing, and increase the lifetime of the silicon wafer and the deterioration of the dielectric breakdown voltage of the oxide film. In the absence of gas, the deterioration does not occur, and when OH groups are distributed in the surface layer by 500 ppm or more, diffusion of heavy metal impurities does not occur. It found that Kagarasu jig can be obtained by heat treatment of the conventional silica glass jig under specific conditions, and completed the present invention. Ie

[0004] The present invention does not contain a reducing gas,
It is an object of the present invention to provide a silica glass jig for heat-treating a semiconductor element in which OH groups are distributed in a surface layer by 500 ppm or more.

Another object of the present invention is to provide a silica glass jig for heat-treating a semiconductor device, in which the lifetime of a silicon wafer and the dielectric breakdown voltage of an oxide film are hardly deteriorated.

Another object of the present invention is to provide a novel method for treating a silica glass jig for heat treatment of a semiconductor device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a silica glass jig made of silica glass obtained by electromelting crystalline silicon dioxide powder, wherein the jig contains a reducing gas. From the processing surface of the semiconductor element.
The present invention relates to a silica glass jig for heat treatment of a semiconductor element in which OH groups are distributed at a concentration of 500 ppm or more to a depth of 00 μm and a method for treating the jig.

[0008] The silica glass jig of the present invention is a jig made of silica glass obtained by vitrifying crystalline silicon dioxide powder by an electric melting method, and has a depth of 100 μm from the processing surface of a semiconductor element. This is a silica glass jig in which OH groups are distributed at a content of 500 ppm or more and do not contain a reducing gas. In particular, the distribution of OH groups is gradually reduced from the processing surface of the jig to the semiconductor element to a depth of 100 μm, and
It is preferable that a distribution containing 200 ppm or less of OH groups is formed at the position of m. Due to having the OH group distribution, the silica glass jig for heat treating a semiconductor element of the present invention has no boundary distortion based on a difference in viscosity between a portion having an OH group and a portion having no OH group, and does not cause separation or displacement of an interface. . The “processing surface” of the semiconductor element refers to a part where the semiconductor element contacts the jig and a part where the heat treatment atmosphere contacts. The OH group content of a deep portion (hereinafter referred to as a central portion) exceeding 100 μm from the processing surface of the semiconductor element is 200 ppm or less and at least 300 ppm from the processing surface of the jig.
It is important to have less. OH group content at the center is 20
If it exceeds 0 ppm, the silica glass jig tends to be thermally deformed.

In addition to the above, it is essential that the silica glass jig of the present invention does not contain a reducing gas. The reducing gas refers to a hydrogen gas or a carbon monoxide gas, and the term "does not contain a reducing gas" means that hydrogen gas is not detected by a laser Raman measurement method, and carbon monoxide gas. Means that it is not detected by the measurement method using gas mass spectrometry. The detection limit by the laser Raman method is 5 × 10 ¹⁶ molecules / cm ³ .
The jig in which the reducing gas is detected in the silica glass by the above measurement method causes deterioration of the lifetime of the silicon wafer and the dielectric breakdown voltage of the oxide film. It is thought that the reason is that heavy metal impurities in silica glass are stable when OH groups are present, but the heavy metal impurities are reduced and easily diffused to the outside by the presence of a reducing gas.

[0010] The treatment method of the present invention is preferably carried out by placing a jig such as a silica glass boat or tube made of silica glass obtained by electromelting crystalline silicon dioxide powder in an atmosphere containing water vapor at 800 ° C or higher, preferably at 800 ° C or higher. This is a method of heating at a temperature of 1000 ° C. or higher for 1 to 50 hours. By the above treatment, the silica glass jig does not contain a reducing gas,
At least 500pp within 100μm from the treated surface
m OH groups are distributed. The water used is preferably pure water used in the semiconductor industry. Further, the treatment method of the present invention may employ a wet oxidation method generally used in the semiconductor industry.

The crystalline silicon dioxide powder used for producing the silica glass jig of the present invention is a quartz powder obtained by finely pulverizing natural crystalline silicon dioxide such as natural quartz, a synthetic crystalline dioxide synthesized by a sol-gel method. Silicon powder with a particle size of 10 to 1
000 μm, preferably in the range of 50 to 500 μm. When the particle size of the crystal powder is less than 10 μm, fine bubbles are generated, and when the particle size exceeds 1000 μm, purification is difficult and impurities are easily mixed.

Hereinafter, the present invention will be described in detail with reference to embodiments.
The present invention is not limited to this.

[0013]

The measuring method used in each of the following examples is as follows.

I) Method of measuring lifetime of silicon wafer: A method of measuring the lifetime in a silicon wafer map using a lifetime measuring device to obtain a defect rate.

Ii) Measurement method of dielectric breakdown voltage of oxide film: Forty MOS diodes are formed on a silicon wafer and
A method of determining a defective rate that occurs when a voltage of 0 Mev is applied.

Iii) Method of measuring OH group content: a method of measuring the distribution of the OH group content from the surface to 100 μm every 10 μm by infrared spectrophotometry.

Iv) Method for detecting carbon monoxide gas: 1 cm
A 1 mm thick silica glass sample was set in an infrared gold image furnace and evacuated with a turbo molecular pump for 30 minutes. The degree of vacuum was 1 × 10 ⁻⁵ . Then 50
The sample was heated from room temperature to 1000 ° C. at a rate of ° C./min, and the released gas was measured by a mass filter gas analyzer MSQ-400. A method in which the amount of released gas is detected by using a result measured without setting a sample as a reference, and regarding a difference from the reference as a release amount.

V) Method for detecting hydrogen gas: A 1 cm square silica glass sample having a thickness of 5 mm was set in a laser Raman spectrophotometer and irradiated with an 488 nm Ar gas laser. Raman peak of silica glass at 800 cm ^-1 and 41
A method of measuring the Raman peak of hydrogen gas molecules at 50 cm ^-1 and detecting the content of hydrogen gas molecules in silica glass from the intensity ratio of the peaks.

Example 1 A crystalline silicon dioxide powder was electrofused to prepare a silica glass rod having a diameter of 16 mm, and the silica glass rod was worked to form a silicon wafer heat treatment boat. In addition, the crystalline silicon dioxide powder is electro-melted separately to have an outer diameter of 260.
A vertical furnace core tube having a length of 1200 mm and a length of 1200 mm was manufactured. After the boat was set in the furnace tube, 1000 ml of pure water was put into a silica glass three-necked flask, one side tube was connected to a nitrogen gas tube, and the other side tube was connected to the furnace tube. And a silicone tube. 3
The one-necked flask was heated to 95 ° C., and nitrogen gas was flowed into the flask at 1 liter / minute, and steam generated in the flask was introduced into the furnace core tube. Heat treatment was performed at 24 ° C. for 24 hours, and OH groups were doped on the boat surface and the furnace core tube inner surface. When the OH group content of the treated boat surface and the inner surface of the furnace core tube was measured by infrared spectrophotometry using FT-IR, the OH of the surface layer of each jig was measured.
The group content is gradually reduced to a depth of 50 μm at 1000 ppm, and at a depth exceeding 50 μm, the OH group content is 20 μm.
ppm. The emission gas was measured using a gas mass spectrometer, but the presence of carbon monoxide gas could not be confirmed. Further, measurement was performed using a laser Raman analyzer, but the presence of hydrogen gas could not be confirmed.

Example 2 A boat for heat-treating a silicon wafer and a vertical furnace core tube were prepared in the same manner as in Example 1, and the boat was set in the furnace core tube. Then, steam generated by an external combustion device was introduced into the furnace core tube. It was introduced and heat-treated at 1100 ° C. for 10 hours to dope OH groups. When the OH group content of the treated boat and the furnace core tube jig was measured in the same manner as in Example 1, the OH group content of the surface layer was gradually reduced to a depth of 80 μm at 800 ppm, and at a further depth, The OH group content was 20 ppm. The emission gas was measured using a gas mass spectrometer, but the presence of carbon monoxide gas could not be confirmed.
Furthermore, measurement was performed using a laser Raman analyzer,
The presence of hydrogen gas could not be confirmed.

Comparative Example 1 A boat for silicon wafer heat treatment and a vertical furnace core tube were prepared in the same manner as in Example 1, the boat was set in the furnace core tube, and then heated at 600 ° C. for 2 hours in an atmosphere containing steam. Treated to dope OH groups. The OH group content in the surface layer of the treated boat and the furnace core tube was 150 ppm and was 150 ppm to a depth of 50 μm, and the OH group content in layers deeper than 50 μm was 20 ppm. When the gas released from the jig of the jig was measured using a gas mass spectrometer, a large amount of carbon monoxide gas was detected. When hydrogen gas was confirmed using a laser Raman analyzer, a large amount of hydrogen gas was detected.

Comparative Example 2 A boat for silicon wafer heat treatment and a vertical furnace core tube were prepared in the same manner as in Example 1 except that the treatment in a steam-containing atmosphere was omitted, and the boat surface and the inner surface of the furnace core tube were treated with propane gas. It was baked with a flame and doped with OH groups. OH group content of the surface layer of the treated boat and furnace core tube is 100p
The content of OH groups in layers deeper than 50 μm was 100 ppm to a depth of 50 μm in pm and 20 ppm. When the gas released from the jig of the jig was measured using a gas mass spectrometer, a trace amount of carbon monoxide gas was detected.

Comparative Example 3 In the same manner as in Example 1, a boat for heat treatment of a silicon wafer and a vertical furnace core tube were prepared. OH on silica glass surface
The group content was 20 ppm. Using the gas mass spectrometer and the laser Raman spectrometer for this jig, the presence of carbon monoxide gas and hydrogen gas was not detected.

Example 3 A 6-inch silicon wafer was heat-treated at 1000 ° C. for 1 hour using the silica glass jigs of Examples 1 and 2. The lifetime of the silicon wafer was measured using the processed silicon wafer. In addition, MOS on silicon wafer
Diodes were prepared and the dielectric breakdown voltage characteristics of the oxide film were measured to determine the defect rate. Table 1 shows the results.

The same treatment as in the above example was performed on the silica glass jigs of Comparative Examples 1 to 3, and the lifetime of the silicon wafer and the dielectric breakdown characteristics of the oxide film were measured. Table 1 shows the results.

[0026]

[Table 1]

As shown in Table 1, the jig of the present invention remarkably reduces the defect rate of the lifetime of the silicon wafer and the defect rate of the dielectric breakdown voltage.

[0028]

The silica glass jig for heat treating a semiconductor device according to the present invention has a small decrease in the lifetime of a silicon wafer and the dielectric breakdown voltage of an oxide film, improves the processing yield of the semiconductor device, and improves the reliability of the semiconductor device. Up. Moreover, since the silica glass produced by the electro-fusion method is used as the material, the heat resistance is high, and the silicon wafer which has been increased in size in recent years is hardly deformed by heat treatment.

The silica glass jig for heat treatment of a semiconductor element of the present invention can be prepared by using a conventionally used silica glass jig for heat treatment of a semiconductor at least 800 mm in an atmosphere containing water vapor.
It has the industrial advantage of being able to be manufactured in a simple manner of processing to ° C.

[Brief description of the drawings]

FIG. 1 is a distribution diagram of OH groups contained in a silica glass jig of the present invention. In FIG. 1, a solid line indicates Example 1, a dashed line indicates Example 2, a two-dot chain line indicates Comparative Example 1, a dotted line indicates Comparative Example 2, and a broken line indicates Comparative Example 3.

Continued on the front page (72) Inventor Toru Segawa 88, Kawakubo, Kanaya, Tamura-cho, Koriyama-shi, Fukushima Shin-Etsu Quartz Co., Ltd. Ring 29 Heraus-Kwarzgrass-Ghemmberg Bereich Halperiter (56) References JP-A-62-268129 (JP, A) JP-A-6-37027 (JP, A) (58) Fields studied (Int. . ^7, DB name) H01L 21/68 C03C 3/06

Claims (3)

(57) [Claims] 1. A silica glass jig comprising a crystalline silica glass obtained by electrically melting the silicon dioxide powder, the jig does not contain a reducing gas of hydrogen gas and carbon monoxide gas, yet the semiconductor A silica glass jig for heat treatment of a semiconductor element, wherein OH groups are distributed at a concentration of 500 ppm or more from the element processing surface to a depth of 100 μm. 2. The content of the OH group is 1 from the treated surface of the semiconductor element.
The silica glass jig according to claim 1, wherein the OH group content is gradually reduced to a depth of 00 µm, and the OH group content at a depth of 100 µm is distributed to be 200 ppm or less. 3. The silica glass jig according to claim 1, wherein the OH group content at the center of the jig is at least 300 ppm less than the content on the treated surface of the semiconductor element.