JP2840164B2 - Quartz glass boat and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass boat for heat treatment of semiconductors, and more particularly to a quartz glass boat with little deterioration in life time.

[0002]

2. Description of the Related Art Machines, equipment, containers, tubes, and the like used in semiconductor manufacturing are required to have high heat resistance and high chemical purity. These members must be members that do not react with the wafer under any conditions or give any element, even traces, to the wafer. Conventionally, quartz glass has been used as a material that meets these requirements. Examples of the quartz glass include quartz glass obtained by melting and vitrifying crystalline quartz by an electric melting method, quartz glass melted and vitrified by an oxyhydrogen flame method, and synthetic quartz glass manufactured by a sol-gel method or a soot method.
However, the quartz glass obtained by melting by the oxyhydrogen flame method has a drawback that the quartz glass contains a large amount of OH groups and is crushed or deformed when used at a high temperature for a long time. Synthetic quartz glass is not used in actual processes because it has a lower viscosity than quartz glass obtained from crystalline quartz powder. For this reason, conventionally, as a jig for the semiconductor industry, quartz glass (hereinafter referred to as electro-fused quartz glass) obtained exclusively by an electro-melting method has been used particularly in a process in which the heat treatment temperature is 1100 ° C. or higher.

However, this electrofused quartz glass has a drawback that contamination from a structure such as a heater, particularly an alkali metal element impurity having a high diffusion rate easily diffuses in quartz glass. Therefore, as means for solving this drawback, a multilayer structure in which a specific amount of OH groups is contained in the thickness direction of the jig has already been proposed. These multilayer structures are suitable for members having a simple structure such as a furnace core tube, but have been considered to be unsuitable so far in a structure such as a boat having a complicated structure, particularly in a structure having a groove for mounting a wafer. Was.
For this reason, electrofused silica glass containing no OH group has been used exclusively for wafer boats.

[0004]

As described above, electro-fused quartz glass has been used exclusively as a material for a wafer boat, but recently, a wafer heat-treated with this electro-fused quartz glass boat has a lifetime below a standard value. It turns out that many things occur. The present inventors have conducted intensive studies on the cause, and found that the decrease in the lifetime is due to heavy metal impurities such as iron, chromium, nickel, and copper. It has been found that the contamination of heavy metal impurities can be efficiently reduced by doping OH groups, particularly a specific amount of OH groups, into the electro-fused quartz glass.

Further, the inventors of the present invention can easily dope a quartz glass boat by heating it in a hydrogen atmosphere or by bringing it into contact with an oxyhydrogen flame or a propane gas flame. I also discovered what could be done. The present invention has been completed based on these findings, and an object of the present invention is to provide a quartz glass boat with less deterioration in lifetime.

It is another object of the present invention to provide a method for manufacturing a quartz glass boat with less deterioration of the lifetime.

[0007]

According to the present invention, there is provided a quartz glass boat formed by forming a quartz glass member obtained by electromelting crystalline quartz powder, wherein a portion in contact with a wafer has an OH group-containing layer having at least 5 μm. Having a content of 80
ppm or more, a quartz glass boat,
And heat treatment of an electrofused quartz glass boat formed of a quartz glass member obtained by electromelting the crystalline quartz powder in a hydrogen atmosphere, or by contacting with an oxyhydrogen flame or a propane gas flame to form an OH group. The present invention relates to a method for manufacturing a quartz glass boat which has less deterioration in life time by being contained in quartz glass.

In the above description, “crystalline quartz powder” means a glass material obtained by finely pulverizing natural crystalline silicon dioxide such as quartz. Further, “electric melting” means melting using heating means using electricity for vitrification. The particle size range of the crystalline quartz powder is 10 to 1000 μm.
m, preferably 50 to 500 μm. Particle size is 10μ
m or less, fine bubbles are generated, and the particle size is 1000 μm.
Above m, it is difficult to purify and impurities are likely to be mixed.

The content of the OH group contained in the OH group-containing layer in the electro-fused quartz glass boat is at least 80 p.
pm. And the thickness of the layer containing the OH group is
It must be at least 5 μm and at most １ ／ of the thickness of the entire boat material. When the content of the OH group is 80 ppm or less, the effect of suppressing contamination of heavy metal impurities is small, and is almost the same as the conventional quartz glass boat. On the other hand, if the OH group-containing layer is 5 μm or less, the effect of suppressing wafer contamination by heavy metal impurities cannot be achieved, and if the layer is １ ／ or more of the boat material, the heat resistance of the boat deteriorates and the boat cannot be used.

In order to make the electrofused quartz glass boat contain OH groups in the above-defined range, a boat made of a quartz glass material is placed in a hydrogen atmosphere at 600 to 800 ° C.
By heating for 1 to 2 hours, or by baking the formed boat with an oxyhydrogen gas burner or a propane gas burner. However, in the latter case, it is necessary to be careful that the boat will be deformed if it is baked with a burner.

When the electrofused quartz glass boat is reused, heavy metal impurities adhere during the heat treatment of the wafer. Therefore, it is necessary to wash the boat with a hydrofluoric acid solution and dope OH groups again.

Hereinafter, the present invention will be described in detail with reference to Examples.

(Measurement method of lifetime) A method of measuring the lifetime in a wafer surface using LIFE TECH-88R manufactured by Semitex.

(Measurement method of OH group content) A method of measuring the OH group content of a layer 50 μm from the surface by infrared spectrophotometry.

[0015]

EXAMPLE A crystalline quartz powder was electromelted to form a quartz glass rod having a diameter of 12 mm. Using this quartz glass rod, three boats for wafer heat treatment were produced. A 5 ″ wafer was set in this boat, and inserted into the quartz furnace core tube.
Heat treatment was performed at 00 ° C. for 5 hours. The wafer after the heat treatment was taken out, its lifetime was measured, and the ratio of the portion where the standard value was 100 μsec or less was determined.
Further, the content of OH groups at 50 μm from the surface of each boat was measured.

On the other hand, as a comparative example, a boat was formed using quartz glass obtained by melting crystalline quartz powder with oxyhydrogen.
A wafer was set in this boat and subjected to a heat treatment in the same manner as described above. The results are shown in Table 1.

[0017]

[Table 1] * The percentage of the lifetime within the wafer surface below the specified value.

In Comparative Example 2, since the OH group content at the center of the surface was as large as 180 ppm, the wafer was subjected to heat treatment at 1200 ° C. for 5 hours, and the wafer support rod of the boat was deformed. For this reason, when the next heat treatment was performed, 50% of the wafers could not be properly placed on the wafer support bar and could be normally heat-treated.

[0019]

As shown in the above Table 1, the proportion of the wafer which has been subjected to the heat treatment using the electro-fused quartz glass boat of the present invention is significantly reduced as shown in Table 1 above. That is, it can be seen that the electro-fused quartz glass boat of the present invention is a boat that can easily manufacture a wafer having an excellent lifetime without lowering the heat resistance.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kimura 2-13-60 Kitafu, Takefu-shi, Fukui Prefecture Shin-Etsu Quartz Co., Ltd. Takefu Factory (56) References JP-A-62-268129 (JP, A) 62-1722 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/22 501 H01L 21/22 511 H01L 21/205

Claims (3)

(57) [Claims] 1. A quartz glass boat formed by molding a quartz glass member obtained by electromelting crystalline quartz powder, wherein a portion to be in contact with a wafer has an OH group-containing layer of at least 5 μm, and the OH A quartz glass boat having a low life time deterioration, wherein the base content is 80 ppm or more. 2. The method for producing a quartz glass boat according to claim 1, wherein a quartz glass boat formed of a quartz glass member obtained by electromelting crystalline quartz powder is heat-treated in a hydrogen atmosphere. 3. The quartz glass boat according to claim 1, wherein a quartz glass boat formed of a quartz glass member obtained by electromelting crystalline quartz powder is treated with an oxyhydrogen flame or a propane gas flame. Production method.