JPS621566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying silane, and in particular to a method for purifying silane to the high level of purity required for the production of electronic grade (ultra-high purity) silicon or amorphous silicon. Traditionally, minimizing impurities in silane sources has involved using highly pure chemical reactants in the silane manufacturing process, using systems that exclude air or water vapor in closed systems, or using various complexities. The use of traps and distillers have been proposed. Although these proposals have been used for many years, there is still a constant search for ways to remove even only a few ppm of impurities in order to meet industrial requirements. In view of the above prior art, the present invention provides a method for purifying silane that can meet the highest purity standards required by the electronics industry. That is, the present invention provides continuous or intermittent (once silane is stored) system using activated hydrogen storage metal or metal hydride that stores hydrogen as the main adsorbent. This is a high-purity purification method in which impurities in the mixture are removed by passing through a mixture of silane and impurities.More specifically, the present invention utilizes a metal powder for hydrogen storage activated by hydrogenation as an adsorbent. Alternatively, gaseous impurity-containing silane is introduced at around room temperature into an adsorption cylinder zone containing metal hydride powder, and is adsorbed or occluded by the adsorbent to adsorb and remove only the impurities.
Alternatively, it includes a step of concentrating and then purging and removing impurities in the upper part of the space. A typical process silane introduced into the purification method of the present invention contains about 99.0% by weight silane and the balance impurities. The impurities to be removed by applying this method are () fluorine, carbon dioxide,
Oxygen, nitrogen, water vapor, intermediate molecular weight silicone, siloxane, chlorosilane, silicon tetrachloride, arsine (AsH ₃ ), diborane (B ₂ H ₆ ), phosphine (PH ₃ ), etc., and impurities () are few ppm. ~
0.1% by weight, and impurities () are mixed in units of 0.1 to 1% by weight. In general, metal materials that have been hydrogen-activated by repeating hydrogen storage-desorption cycles at least once, preferably multiple times, are brittle and become powdered as the cycles are repeated, increasing their surface area. The inventors thus demonstrated that once hydrogenated,
Dehydrogenated metal materials or metal materials containing some hydrogen are very active and act very favorably as adsorbents and occluding materials for impurities in the silane, as described below, and have excellent properties. It was found that this product has a purifying effect. In particular, metal hydrides used as adsorbents with an equilibrium storage pressure of 10 atm or less at room temperature (approximately 20°C) have a particularly high ability to absorb impurities.
It was extremely active and showed excellent properties. Typical examples are Ti-Mn alloy, Ti-Zr-Mn alloy, Zr-Mn
It was a hydrogenation-dehydrogenation alloy such as a series alloy. The metal hydride powder or hydrogen storage metal material activated in this way has a size of 0.1 μm to several 100 μm.
This powder has a high surface area and adsorbs and removes impurities in crude silane gas. This powdery substance is
The granular form itself can also be used;
In order to ensure good circulation of the silane gaseous mixture in the zone, it can also be used as a porous material in combination with conventional fillers, by sintering, etc. Further, in this method, it is preferable that the raw material gas is introduced at a high pressure of about 10 atm or less and passed through the adsorption cylinder. Examples of the present invention will be described below. Example 1 The outline of the configuration of the purification apparatus of this example is shown in FIG. 1. As the adsorbent 2 shown in Figure 1, the average particle size is approximately
A ZrMn ₂ alloy pulverized into 20 meshes is stored in an adsorption cylinder 1. First, the adsorbent pretreatment process will be described. Gas take-off valve 5
Connect the tip of the pump to an exhaust device consisting of an oil rotary pump, oil diffusion pump, etc. to degas the system in advance. The temperature at this time may be room temperature, but the higher the temperature, the more active it is against impurities and the greater the purification effect. Next, about 90% of high-purity hydrogen gas is supplied from the raw material gas introduction valve 4.
Hydrogen is introduced to atmospheric pressure, and then purge valve 6
The hydrogenation-dehydrogenation cycle is repeated 10 times in which hydrogen is purged further and hydrogen is released from the gas take-off valve 5 by the exhaust device. Through this hydrogen activation treatment of the adsorbent, the adsorbent 2 has an average particle diameter of approximately 0.4μ.
The surface area was increased. The activation pretreatment is completed by the multiple hydrogen release treatment steps,
At this time, the adsorbent became extremely effective in adsorbing and removing impurities. In addition, in the figure, 3
is a filter for preventing the adsorbent 2 from flowing out from the adsorption column 1, and is made of a porous metal material. Impurity-containing silane was introduced into the adsorption cylinder 1 pretreated as described above through the raw material gas introduction valve 4 at room temperature, and the entire system was closed. The raw material silane introduced contained the following components.

[Table] All of the equipment in which the silane and impurity mixture came into contact was made from SUS316 stainless steel. Approximately 5 minutes after the system was closed, a very small amount of silane was instantly purged from the purge valve 6, and the purified gas was analyzed by gas chromatography and mass spectrometry, and the silane content was approximately 99.999% by weight or more. It can be seen that the purification effect is high. Example 2 A TiMn _1.5 alloy pulverized to an average particle size of ₁₀₀ mesh was formed into a plate shape by a sintering method using a conventional binder to improve gas flow, and an adsorbent 12 was prepared.
The configuration of the apparatus shown in FIG. 2 was used. After repeating hydrogen activation at room temperature and about 30 atmospheres using the same means as in Example 1, the raw material gas is continuously introduced into the adsorption column 11 from the raw material gas introduction valve 14 and purified continuously. The gas was taken out from the gas take-off valve 15. 13 is a filter. The purity of the raw material gas in this example was 99.9% by weight, and the remainder was impurities ranging from several ppm to several tens of ppm, namely oxygen, nitrogen, carbon, fluorine, and water vapor. Similar to the previous example, as a result of analyzing the purified gas,
It showed a purity of 99.9999% by weight, confirming that it has an extremely excellent purification effect. Example 3 FIG. 3 shows a schematic vertical cross-sectional view of the apparatus of this example. A Ti _{0 .5} Zr _{0 .5} Mn _{1 .7} alloy pulverized to a diameter of about 0.1 mm was solidified and formed into a porous plate shape, which was housed in an adsorption cylinder 21 as an adsorbent 22 . Furthermore, porous plates 26 made of a non-adsorbent material were arranged between the plate-shaped adsorbents so that gas could flow smoothly. The activation treatment with hydrogen was performed under the same conditions as in Example 1, and the subsequent operations were as in Example 2, in which raw silane gas was continuously introduced through the inlet valve 24 and purified silane gas was continuously introduced through the outlet valve 25. We used the method of extracting from.
In the figure, 23 is a filter. As a result of analyzing the purity of the purified gas in the same manner as in the previous example, it was found that in this example as well, the purity of the silane gas was improved and there was an excellent purification effect. Example 4 In order to increase the purification capacity, as shown in Fig. 4,
The apparatus system described in Example 2 was multistaged. As shown in the figure, a porous metal material 36 made of sintered metal is used as a partition wall, and Zr-Mn-based metal hydride powder 32 activated by a hydrogenation-dehydrogenation process is placed between them, and an adsorption column is used as an adsorbent. I stored it in 31.
Reference numeral 37 is a heater for degassing regeneration to remove adsorbed impurities and for enhancing the adsorption effect, and can be used as necessary. 3
3 is a filter for preventing outflow and scattering of the adsorbent powder, 34 is a raw gas inlet valve, and 35 is a purified gas outlet valve. In this example, it was confirmed that the rate of continuous flow of the raw material gas could be increased, and the silane purification effect was higher than in the previous example. The equipment and other materials used in this method, other than the adsorbent, are inert to silane and impurities, can withstand the temperatures and pressures applied to each zone, and do not release impurities into the system. Various materials that do not release, such as stainless steel SUS304 and
SUS316 and alloys containing a large proportion of nickel and a small proportion of copper are used. As described above, the present invention is a method for purifying silane using a metal material for hydrogen storage as an adsorbent, which uses a device with a simple configuration, and achieves excellent purification effects with simple operation and at a relatively low cost. It is something that can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of a purification apparatus having an intermittent system, which is one embodiment of the present invention, and FIGS. FIG. 4 is a schematic vertical cross-sectional view of another embodiment of an apparatus in which three stages of the embodiment of FIG. 2 are connected in series in order to further enhance the purification effect. 1...Adsorption cylinder, 2...Adsorbent, 3...Filter, 4...Material gas introduction valve, 5...Gas extraction valve,
6...Purge valve.

Claims (1)

[Scope of Claims] 1. A silane characterized in that the silane is purified by using a metal material for hydrogen storage or a metal hydride activated by hydrogenation-dehydrogenation treatment as the main adsorbent for impurities contained in the silane. Purification method. 2 The room temperature of the material used as the adsorbent (approximately 20
2. The method for purifying silane according to claim 1, wherein the hydrogen storage equilibrium pressure at 10°C (°C) is 10 atm or less.