JP2627324B2 - Silane purification method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for purifying silane, and more particularly, to a method for purifying silane capable of removing oxygen contained in silane as an impurity to an extremely low concentration.

Silane is important as a raw material for manufacturing silicon semiconductors and a gas for ion implantation, etc., and its usage is increasing year by year, and at the same time, with the high integration of semiconductors, the content of impurities is extremely low. Things are required.

2. Description of the Related Art In general, silanes used in the production of semiconductors are commercially available in a form diluted with hydrogen gas or inert gas in addition to pure silane. These silanes contain oxygen, moisture and the like as impurities, of which the moisture can be removed by a dehumidifier such as synthetic zeolite.

The oxygen content in commercially available purified silane is usually 10 ppm or less, but some of the recent silanes in cylinders have a relatively low oxygen content of 0.1 to 0.5 ppm, and are commercially available.

There are few known techniques for efficiently removing oxygen contained in silane.

[Problems to be solved by the invention]

However, if the oxygen content is less than 1 ppm, it is not possible to sufficiently respond to the demands in recent semiconductor manufacturing processes, and it is strongly desired that the oxygen content be 0.1 ppm or less.

In addition, since these gases may be contaminated by impurities such as air during the supply process to the semiconductor manufacturing apparatus such as when connecting cylinders or switching pipes, it is desirable that these gases be finally removed immediately before the apparatus.

[Means for solving the problem]

The present inventors have conducted intensive studies to efficiently remove oxygen contained in silane to an extremely low concentration, and as a result, by bringing silane into contact with nickel silicide, the oxygen concentration is 0.1 ppm or less, furthermore Has been found to be able to remove to 0.01 ppm or less, and completed the present invention.

That is, the present invention is a method for purifying silane, comprising contacting a crude silane with a silicide of nickel to remove oxygen contained in the crude silane.

The present invention is applicable to silane alone, hydrogen (based on hydrogen gas) and inert gas such as nitrogen and argon (based on inert gas).
This is applied to the removal of oxygen contained in silane diluted with (hereinafter referred to as crude silane).

In the present invention, nickel silicide is Ni ₃ Si, Ni ₂ S
Nickel silicide and nickel generally known as Ni _X Si _Y such as i, Ni ₃ Si ₂ , and Ni ₂ Si _3, and silicon bonded to nickel in various other forms.

There are various ways to obtain nickel silicide,
Among these, silicide can be easily obtained by contacting nickel with monosilane as a simple method. In this case, the nickel may be any one containing a nickel compound which is easily reduced such as metallic nickel or nickel oxide as a main component. Further, a material containing a small amount of copper, chromium, iron, cobalt, or the like as a metal component other than nickel may be used.

These nickels may be used alone or in a form supported on a catalyst carrier or the like, but are usually supported on a catalyst carrier or the like for the purpose of increasing the contact efficiency between the nickel surface and the gas. It is used in the form which was made.

As a method of supporting nickel on a carrier, for example,
A carrier powder such as diatomaceous earth, alumina, silica alumina, aluminosilicate and calcium silicate is dispersed in an aqueous solution of a nickel salt, and an alkali is added to deposit a nickel component on the carrier powder, followed by filtration, if necessary. The cake obtained by washing with water is dried at 120-150 ° C, and then calcined at 300 ° C or more, and the calcined product is pulverized, or inorganic salts such as NiCO ₃ , Ni (OH) ₂ , Ni (NO ₃ ) ₂ , NiC
After baking and pulverizing an organic salt such as ₂ O ₄ , Ni (CH ₃ COO) ₂ , a heat-resistant cement is mixed with this, and baking is performed.

These are usually formed into a molded body by extrusion molding, tablet molding, or the like, and are used as they are, or crushed to an appropriate size as needed. As a molding method, a dry method or a wet method can be used, and in that case, a small amount of water, a lubricant, or the like may be used.

Further, as a nickel-based catalyst, for example, a steam conversion catalyst,
C11-2-03 (NiO-cement), C11-2-06 (NiO-refractory), C11-2 (Ni-calcium aluminate), C11
-9 (Ni-alumina); hydrogenation catalyst, C46-5 (Ni-silica alumina), C46-6 (Ni-calcium silica), C
46-7 (Ni-diatomaceous earth), C46-8 (Ni-silica), C36
(Ni-Co-Cr-alumina); gasification catalyst, XC99 (Ni
O); Hydrotransformation catalyst, C20-7 (Ni-Mo-alumina)
[The above are manufactured by Toyo CCI Co., Ltd.] and hydrogenation catalyst, N-111
(Ni-diatomaceous earth); various catalysts such as gasification catalyst, N-174 (NiO); gasification catalyst, N-185 (NiO) (all manufactured by JGC Corporation) are commercially available. An appropriate one may be selected from the above and used.

In short, any form may be used as long as reduced nickel, nickel oxide, and the like are finely dispersed and have a large surface area and a high contact efficiency with gas.

The specific surface area of the catalyst is usually 10 to 300 m ² / g by the BET method.
, Preferably in the range of 30 to 250 m ² / g.

The content of nickel is usually 5 to 95% by weight, preferably 20 to 95% by weight in terms of metallic nickel.

If the content of nickel is less than 5 wt%, the deoxidizing ability is reduced. If the content is more than 95 wt%, sintering may occur during reduction with hydrogen and the activity may be reduced.

The siliconization of nickel can be usually carried out by bringing silane into contact with reduced nickel, nickel oxide or the like. In the case of nickel oxide or the like, however, it is preferable to reduce hydrogen in advance by hydrogen reduction. Hydrogen reduction can be performed, for example, by passing a hydrogen-nitrogen mixed gas at a cylinder linear velocity (LV) of about 1 cm / sec at about 350 ° C. or less, but care must be taken to prevent a sudden rise in temperature due to the exothermic reaction. is there. Further, by performing the reduction with hydrogen-based silane, siliconization can be performed at the same time, which is advantageous.

Usually, siliconization is carried out by filling a cylinder such as a purification cylinder with nickel or a carrier obtained by supporting nickel or the like, and passing silane or a silane-containing gas through the cylinder.

The concentration of silane used for siliconization is usually 0.1% or more,
Preferably, 1% or more is used. Silane concentration
If it is lower than 0.1%, it takes time to complete the reaction, which is uneconomical.

Although siliconization can be performed at room temperature, it is an exothermic reaction, and the temperature is easily raised as the silane concentration is higher, so that the gas flow rate is usually adjusted to 200 ° C or lower, preferably 100 ° C or lower. It is preferable to perform while doing.

The end of the siliconization can be known from a decrease in the calorific value and an increase in the amount of silane flowing out from the outlet of the cylinder.

In the present invention, siliconized nickel may be charged into another purification cylinder again, and oxygen may be removed and purified through crude silane. Preferably, siliconization is performed in a silane purification column from the beginning, and after completion of siliconization, crude silane is continuously supplied to perform oxygen removal purification.

The purification of silane is usually performed by flowing crude silane through a purification cylinder filled with nickel silicide, and oxygen contained as impurities in crude silane by contacting the crude silane with nickel silicide. Is removed.

The oxygen concentration in the crude silane applied to the present invention is usually 10
It is 0 ppm or less. If the oxygen concentration is higher than this, the calorific value increases, so that a gradual heating means is required depending on the conditions.

The filling length of silicide of nickel to be filled in the purification cylinder is
In practice, it is usually 50 to 1500 mm. If the filling length is shorter than 50 mm, the oxygen removal rate may be reduced.
If it is longer than 00 mm, the pressure loss may be too large.

The cylinder linear velocity (LV) of the crude silane at the time of refining differs depending on the oxygen concentration in the supplied silane and the operating conditions and cannot be specified unconditionally, but is usually 100 cm / sec or less, preferably 30 cm / sec or less. .

The contact temperature between the silane and the silicide of nickel is the temperature of the gas supplied to the inlet of the refining column, which is about 200 ° C. or lower, preferably 0 to 100 ° C., which is usually room temperature and requires special heating and cooling. do not do.

Atmospheric pressure is not particularly limited to the pressure, vacuum, although it is possible either process the pressure is usually 20 Kg / cm ² abs or less, preferably 0.1~10Kg / cm ² abs.

Further, even if a small amount of water is contained in the silane, the deoxygenation ability is not particularly adversely affected, and when a carrier or the like is used, the water is also removed depending on the type.

In the present invention, it is also possible to appropriately combine a water removing step with a dehumidifier such as a synthetic zeolite as needed in the oxygen removing step using silicon silicide, whereby water is completely removed, and extremely high purity is obtained. Can be obtained.

〔The invention's effect〕

According to the present invention, oxygen in silane, which was conventionally difficult to remove, can be removed to an extremely low concentration of 0.1 ppm or less, and even 0.01 ppm or less. It has become possible to obtain purified silane.

〔Example〕

Example 1 (Reduction treatment of nickel) A commercially available nickel catalyst (N-111, manufactured by JGC Corporation) was used. Its composition is in the form of Ni + NiO,
5 ~ 47wt%, Cr2 ~ 3wt%, Cu2 ~ 3wt%, diatomaceous earth 27 ~ 29wt
% And graphite of 4 to 5 wt%, and is a molded body having a diameter of 5 mm and a height of 4.5 mm.

85 ml of this nickel catalyst crushed to 8-10 mesh is filled into a quartz purification cylinder with an inner diameter of 19 mm and a length of 400 mm, and a filling length of 300 mm
(1.0 g / ml packing density).

Hydrogen at normal pressure, temperature 150 ° C, flow rate 595cc / min (LV =
(3.6cm / sec) for 3 hours,
Cooled to room temperature.

(Silicide of nickel) 510cc of hydrogen containing 10vol% silane is added to this purifying cylinder.
/ min (LV = 3 cm / sec) to siliconize nickel. At this time, the room temperature was 25 ° C., but the temperature of the gas at the outlet of the cylinder rose to about 80 ° C. due to the heat generated by siliconization. Thereafter, the temperature of the outlet gas gradually decreased, and after 1.5 hours, returned to room temperature, and the siliconization treatment was completed.

(Purification of silane) Subsequently, a hydrogen-based crude silane containing 10 vol% of silane and 0.15 ppm of oxygen as an impurity was flowed at 1700 cc / min (LV = 10 cm / sec) into the purifier, and the yellow phosphorus emission type oxygen analyzer was used. When the oxygen temperature in the outlet gas was measured using (lower limit of measurement: 0.01 ppm), no oxygen was detected.
m or less. After 100 minutes from the start of the purification, even if the gas flow rate was increased four times to 6800 cc / min (LV = 40 cm / sec), the oxygen concentration of the outlet gas was 0.01 ppm or less. 300 in this state
After holding for 1 minute, the gas was switched to a hydrogen-based crude silane containing 10 ppm by volume of oxygen at a silane concentration of 10 vol%, and the flow rate was returned to 1700 cc / min (LV = 10 cm / sec), and the gas continued to flow for 300 hours. The oxygen in the outlet gas was 0.01 ppm or less.

Comparative Example 1 Activated carbon (yago shell charcoal) crushed to 8 to 24 mesh 48g
300 mm (packing density 0.5
7 g / ml), and heat-treated in a helium stream at 270 to 290 ° C. for 4 hours, and then cooled to room temperature.

10 vol% of the same silane used in Example 1
A hydrogen-based crude silane containing 0.15 ppm of oxygen as an impurity was flowed at 1700 cc / min (LV = 10 cm / sec), and the oxygen temperature in the outlet gas was measured to be 0.10 ppm. Although the flow was continued, no change in the oxygen concentration was observed.

Example 2 (silicide of nickel) Reduced nickel was prepared in a purification cylinder in the same manner as in Example 1, and 100% silane was added to this at 51 cc / min (LV = 0.3 cm / sec).
For 2 hours to siliconize nickel.

(Purification of silane) When silane (100%) containing 0.05 ppm of oxygen as an impurity was flowed at 850 cc / min (LV = 5 cm / sec) into this purifier and the oxygen concentration in the outlet gas was measured, it was 0.01 ppm. It was below. In this state, the flow was continued for 10 hours, but oxygen in the outlet gas was 0.01 ppm or less.

Example 3 (Siliconide of Nickel) Reduced nickel was prepared in a purification cylinder in the same manner as in Example 1, and nitrogen containing 10 vol% of silane was added thereto at 510 cc / min.
(LV = 3 cm / sec) for 3 hours to siliconize nickel.

(Purification of silane) 10 vol% of silane and 0.2
850cc / mi of nitrogen-based crude silane containing 0ppm oxygen
When the oxygen concentration in the outlet gas was measured by flowing at n (LV = 5 cm / sec), it was 0.01 ppm or less. In this state, the flow was continued for 10 hours, but the oxygen in the outlet gas was 0.01 ppm or less.

Example 4 (Preparation of Nickel Catalyst) 454 g of Al (NO ₃ ) ₃ .9H ₂ O was dissolved in water of No. ₃ and cooled to 5 to 10 ° C. in an ice bath. While stirring vigorously, add Na
A solution of 200 g of OH dissolved in 1 water and cooled to 5 to 10 ° C. was added dropwise over 2 hours to obtain sodium aluminate.

Then dissolved _{Ni (NO 3) 2 · 6H} 2 O101g of water 600 ml,
To this was added 45 ml of concentrated nitric acid, cooled to 5-10 ° C., and added to the sodium aluminate solution over 1 hour with vigorous stirring.

The precipitate formed is filtered and the precipitate obtained is diluted with 2
The operation of stirring for minutes and washing was repeated six times to make the mixture neutral.
The obtained precipitate was subdivided, dried in an air bath at 105 ° C. for 16 hours, and then pulverized, and sieved to collect 12 to 24 mesh. This is 29.5wt% nickel oxide (Ni
O).

(Silicide of nickel) 85 ml of this was placed in the same purification cylinder as used in Example 1.
(65g) (filling density 0.77g / ml)
After reducing the nickel by flowing at a temperature of 1.0 ° C. and a linear velocity (LV) of 1.0 cm / sec for 16 hours, the silicon was siliconized under the same conditions as in Example 1.

(Purification of silane) 10vol% of silane and 0.17p as impurities
1700cc / min of hydrogen-based crude silane containing pm oxygen
(LV = 10 cm / sec), and the oxygen concentration in the outlet gas was measured and found to be 0.01 ppm or less. In this state, flowing was continued for 10 hours, but oxygen in the outlet gas was always 0.01 ppm or less.

Claims (1)

(57) [Claims] 1. A method for purifying silane, comprising contacting a crude silane with a silicide of nickel to remove oxygen contained in the crude silane.