JPS59129421A - Member for heat treatment of semiconductor - Google Patents

Abstract

PURPOSE:To prevent devitrification or deformation even by long time use by using a quartz glass which contains Na, K and Li at 0.05ppm or less respectively, and Cu at 0.05ppm, and has a viscosity of 10<12> poise or more at 1,200 deg.C. CONSTITUTION:The quartz glass for the heat treatment of a semiconductor dislikes devitrification or deformation during use. Even when alkaline metals such as Na, K and Li are restricted to 0.05ppm or less respectively, the devitrification can not be prevented in the case of excess of Cu, and further the viscosity has relation to the deformation by high temperature and long time use. Besides, when alkaline metals or Cu become much, they move through the quartz glass in use at a high temperature and scatter from the surface, thus decreasing the yield by affecting the semiconductor element. The use of the quartz glass which contains Na, K and Li at 0.05ppm or less respectively, and Cu at 0.05ppm, and has the viscosity of 10<12> poise or more at 1,200 deg.C enables to entirely avoid these hindrances, and accordingly the yield of the element improves.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor heat treatment members such as a quartz glass furnace core tube used for heat treatment of semiconductor materials such as 3i, its accessories, and jigs.

BACKGROUND ART Equipment and jig parts made of quartz glass have traditionally been used in semiconductor manufacturing processes, particularly in heat treatment processes, because of their heat resistance and high purity. However, since conventional quartz glass products are made from naturally produced quartz, it is unavoidable that trace elements such as aluminum, alkali, and alkaline earth elements are mixed in. ~31) rll11 was included.

When this type of quartz glass is used as a semiconductor heat treatment component, such as a furnace core tube, at high temperatures during the heat treatment process, the viscosity may decrease, leading to deformation of the furnace core tube, or promoting devitrification of the quartz glass. It was impossible to use it for a long time.

Those that cause these devitrification deformations have a large concentration of impurities in the quartz glass, and conventionally attention has been paid to reducing the total amount of impurities in the quartz glass. However, it was found that among the impurities, alkali metals such as Na, L(, Li, etc.) and copper have a particularly large effect.Also, when alkalis, which are network modifying ions, are contained in quartz glass, the viscosity decreases. , which was a cause of deformation.

In addition, when alkali ions or copper ions with small ionic radii exist in the oxide film of a silicon semiconductor device, these ions move relatively freely in the oxide film, so when the concentration becomes high, the inversion layer This causes the generation of electrostatic capacitance, changes in capacitance, etc., and the device no longer functions. This problem has become particularly important in the case of recent high-density devices. When we investigated which process in semiconductor manufacturing causes alkali and copper contamination of semiconductors, we found that the diffusion furnace used in the heat treatment process is the biggest factor.

In other words, in a diffusion furnace that uses a conventional quartz glass furnace core tube, alkali and copper easily move in the quartz glass as in silicon oxide films, and especially at high temperatures, they jump out from the surface of the quartz glass furnace tube. It was found that it contaminates the semiconductor surface during heat treatment.

In order to compensate for the above drawbacks, the use of a synthetic quartz glass furnace core tube with low alkali and copper content was considered, but this is not only expensive because it is synthetic quartz, but also has low viscosity, so it requires low-temperature heat treatment. Can only be used. Therefore, even if the yield of elements was poor, there was no choice but to use a normal quartz glass furnace core tube -3-.

An object of the present invention is to provide a semiconductor heat treatment member made of quartz glass that does not cause devitrification or deformation even when used for a long time as a semiconductor heat treatment member, and can improve the manufacturing yield of semiconductor devices. .

The gist of the present invention is that Na, K.

The semiconductor heat treatment member is characterized in that it is made of quartz glass having an alkali metal content of 0.5 ppm or less, a Cu content of 0.0511 r1 m or less, and a viscosity of 1012 poise or more at 1200°C.

This invention not only pays attention to the impurities in silica glass for cliff conductor heat treatment as described in the previous article, but also takes into account the amount of impurities in Na, l-i alkali metals, C1, and even viscosity. In order to prevent devitrification and deformation of heat treatment members, the use of quartz glass containing less of the above elements, which easily move in quartz glass at high temperatures, is used for heat treatment of semiconductors. The aim is to improve manufacturing yield.

Heat treatment ■To prevent devitrification and deformation during use with culms,
Not only alkali metals such as Na, Lt, but also Cu
also needs to be regulated.

Even if the alkali metal content is Q and 5ppm or less, CLI
If it is excessive, devitrification cannot be prevented, and it is necessary to regulate both. Furthermore, viscosity is also a major factor in preventing deformation, and the viscosity at 1200°C is 10
If it is not 12 poise or higher, it will deform during use at high temperatures and cannot be used for a long time.

In addition, when the alkali metal and CLI increase, as mentioned above, when used as a semiconductor heat treatment member at high temperatures,
It moves through the quartz glass and scatters from the quartz glass surface, adversely affecting semiconductor devices and reducing manufacturing yield. For this purpose, Na, I-+ is added to 0.5 ppm or less, and Cu is added to 0.5 ppm or less. Q3ppm3pp: Suru must W power. Even if alkali metals are each kept below 0.5flpHl and scattering from the quartz glass surface is prevented, if CU is excessive, C0 will fly out and have an adverse effect, so both alkali metals and C1l should be regulated. It is necessary to.

Example (1) Natural quartz is finely ground, sieved to 150-250#, sharpened, concentrated by flotation method, and further added to a concentrated 5% hydrofluoric acid solution at 60°C or higher. It was soaked for 10 hours and made into refined powder. This was melted for a long time (12 hours) to scatter the CLI and alkali metal, and then molded.
111111 A furnace core tube with a wall thickness of 3 mm and a length of 1820 mm and a wafer port used therein were obtained. Table 1 shows the chemical analysis values of this wafer boat.

Example (2) The refined powder obtained in Example (1) was melted for 7 hours to make an ingot, and the ingot was electrolyzed with a direct current of 10 to 50 kV for 5 hours or more under heating at 1200°C or higher to form an alkali and Move the copper-6- and mold the purified part to an outer diameter of 100mm.
A furnace core tube with a wall thickness of 3 mm and a length of 1820 mm and a wafer port used therein were obtained. Table 1 shows the chemical analysis values of this wafer port.

Comparative Examples (7) and (2) Previous) Furnace core tube and wafer port molded from synthetic quartz in the same shape as Examples (1) and (2) (Comparative Example 1) and natural quartz were pulverized to 50% After sieving to ~250# to remove iron, the ore was concentrated by a flotation method, and the raw material powder treated with hydrofluoric acid was melted and transferred to a conventional high-purity quartz glass furnace core tube and wafer port as described in Example (1). Comparative Example 2 was molded into the same shape as 2).

The chemical analysis values of these products are shown in Table 1.

A wafer port on which a semiconductor element was mounted was installed inside the furnace core tube obtained in Examples (1) (2) and Comparative Examples (1) and (2) described above, and the furnace core tube was subjected to s+ c-st system equalization. Insert the heating tube as a liner tube into the soaking tube attached to the diffusion furnace, and
After one year of continuous heating to manufacture semiconductors at 7-250°C, the condition of each quartz tube was examined. The results are shown in Table 2.

The 5iC-8i soaking tube used here contains Na, lj
The alkali metals treated with high purity, each having an alkali metal content of 1 pI'1m or less, were used.

As is clear from Tables 1 and 2, Na.

If the alkali metals of K and Li are each 0.5 ppm or less, and the Cu content is 0.03 prl11 or less, and the viscosity is 1012 or more at 1200°C, the silica glass furnace core tube will devitrify even if used for one year. The obtained semiconductor had a long lifetime without deformation or deformation, and had a flat band voltage difference [ΔVrnl] of 0.1 or less, and was of extremely high quality.

On the other hand, synthetic quartz (Comparative Example 1) contained less alkali and C1, and the obtained semiconductor was of high quality, but due to its low viscosity, the furnace core tube was removed after 1 to 2 months of use. It became deformed and became unusable. Furthermore, in the conventional quartz glass containing 1 to 3 ppm of alkali-8- and 011 (Comparative Example 2), the quartz glass furnace core tube devitrified within 2 to 3 months after use.
It was transformed again. The obtained semiconductor was also of low quality.

As described in detail above, according to the present invention, the alkali in the quartz glass is reduced to 0. ! Mr+m or less, (l is 0.O3
By controlling the content to ppm or less, devitrification of the quartz glass can be prevented and long-term use becomes possible. Also, Example (1)
As exemplified in (2) above, when a silicon carbide soaking tube is used, by using the heat soaking tube with an alkali metal content of 1 ppm or less (preferably o, 5 ppm or less), the heating time can be maintained even longer. This enables the use of Moreover, the semiconductor obtained is also of high quality.

The quartz glass of the present invention also has the effect of increasing viscosity by reducing alkalis, which are m-order modifying ions.

Furthermore, the quartz glass of the present invention is produced by high purity treatment of raw material powder.
Since it can be obtained by removing alkali and -0-CLI by long-time melting, electrolytically treating a melted ingot, etc., it can be manufactured at low cost.

In the above embodiment, a manufacturing method using long-time melting and ingot electrolysis was shown, but the present invention is not limited to this, and other manufacturing methods can be adopted.

In addition, although it was used together with a silicon carbide soaking tube, it is also possible to make the quartz glass furnace core tube a certain thickness and use it alone with the quartz glass furnace core tube. It is not limited to the quality b, but anything with an alkali content of 1 ppm or less, such as ΔQ20a'M, may be used.

Patent applicant: Toshiba Ceramics Corporation -10-

Claims (1)

[Claims] Alkali metals of Na, Li and 0.5 ppm each
or less, and Cu is 0. O3ppm or less, 120
A member for semiconductor heat treatment characterized by being made of quartz glass having a viscosity of 1012 poise or more at 0°C.