JPH0645447B2 - Purification method of silicon hydride - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silicon hydride represented by the general formula SinH _{2n + 2} (n is 1, 2, 3 or 4), particularly monosilane (SiH ₄ ),
A small amount of phosphine (PH ₃ ) contained in disilane (Si ₂ H ₆ ).
And a method for purifying silicon hydride.

BACKGROUND ART In recent years, with the development of the electronics industry, demand for semiconductor silicon such as polycrystalline silicon or amorphous silicon has been rapidly increasing. Silicon hydride has recently become more important as a raw material for manufacturing such silicon for semiconductors, and it is expected that demand will increase in the future.

As a method for producing these silicon hydrides, several methods such as those shown below are known, but whichever method is adopted, the amount of silicon hydride gas usually synthesized is very small. PH ₃ included. Although the content varies depending on the production method, for example, PH ₃ having a concentration of about 100 ppm is contained in the silicon hydride produced by the above method. The effect of PH ₃ as an impurity in silicon hydride used as a semiconductor gas is large, and its content is usually 10 ^−9.
It should be below (ppb or less).

Prior Art As a method for removing a trace amount of PH ₃ in silicon hydride such as SiH ₄ , it is common to use an adsorbent,
For example, the following methods are known. That is, the one using synthetic zeolite A or the synthetic zeolite X as the adsorbent (Japanese Patent Publication No. 36-1774) and the exchangeable positive catalyst in the zeolite having a uniform pore size that hardly adsorbs silane (for example, synthetic zeolite 3A, 4A). Ions exchanged with divalent cations, especially zinc and lead (Japanese Patent Publication No. 48-41437, 48-41439), sodium ions in synthetic zeolite 4A exchanged with divalent cations or silver ions. (JP-A-48-7
5475, JP-A-59-30711, combined use of activated carbon and synthetic zeolite-4A (JP-A-58-69).
715, 58-172220), using a hydrogen storage metal material or a metal hydride (JP-A-58-120).
511) and other methods have been reported. However, these adsorbents have various problems such as a small adsorption capacity, a large silane adsorption loss, and an inability to be regenerated.

The present inventors have made diligent efforts to develop an adsorbent capable of selectively removing phosphine in silicon hydride, and found that these problems can be solved by using a zeolite having a large silica content as the adsorbent, The present invention has been completed.

SUMMARY OF THE INVENTION The present invention provides silicon hydride containing phosphine
₂ and Al ₂ O ₃ as constituent components, and the molar ratio of SiO ₂ and Al ₂ O ₃ contained (SiO ₂ / Al ₂ O ₃ ).
_A method for purifying silicon hydride, which comprises treating with a synthetic or natural zeolite adsorbent other than mordenite having a _{molar ratio} of 5 or more.

Detailed Disclosure of the Invention Hereinafter, the present invention will be described in detail.

The silicon hydride that is the object of the present invention has the general formula Si _n H _{2n + 2}
(N is 1, 2, 3 or 4),
Particularly, SiH ₄ is most preferable. Of course, these may be a mixture or may contain a gas other than PH ₃ .

The adsorbent in the present invention means SiO ₂ and Al ₂ O _3.
And the molar ratio of SiO ₂ and Al ₂ O ₃ (SiO 2
A natural or artificial zeolite other than mordenite _{having a 2} / Al ₂ O ₃ ) _{molar ratio} of 5 or more. The chemical composition of zeolites is an aluminosilicate containing alkali metals, alkaline earth metals or other metals. (SiO ₂ / Al ₂ O ₃ )
_In recent years, many kinds of so-called high-silica zeolites having a higher _{molar ratio} than the conventional ones can be synthesized.

Specifically, for example, using organic bases such as quaternary ammonium compound amines from a silica source and an alumina source, Mobile Oil Co., Union Carbide Co., ICI Co., Ltd.
Z synthesized by Teijin Oilification, New Fuel Oil Development Technology Research Association, etc.
Those represented by zeolites such as SM, NU, EU, TPZ, and ISI (for example, US Pat3308069, US Pat370
2886, USPat 3950496, JP-A-56-73618, JP-B-56-49850, JP-A-57-200218, JP-A-57-149819, JP-A-57-95821); alcohols, ethers, ketones instead of organic bases. , High silica zeolite synthesized by organic compounds such as ester, carboxylic acid, etc. by ICI, Mitsubishi Heavy Industries, New Fuel Oil Development Technology Research Association, etc .; ZSM-5 as seed crystal, alkali metal hydroxide, etc. Mobile Oil Company using an inorganic base,
High silica zeolites synthesized by Idemitsu Kosan (for example, JP-A-56-37215 and JP-A-57-7819); and zeolites rich in silica by dealumination treatment can all be suitably used. Further, all or part of the exchangeable cations of the above-mentioned zeolite are magnesium ions, causium ions, manganese ions, zinc ions,
It may be an aluminosilicate containing a divalent cation such as lead ion or cobalt ion, or one exchanged with a proton, and a polyvalent cation such as titanium ion or boron ion. The exchange of cations by protons is the usual method,
That is, it can be carried out in an aqueous solution of hydrochloric acid or ammonium chloride.

The zeolite applied to the present invention is SiO ₂ in zeolite.
Zeolite other than mordenite in which the composition ratio of Al ₂ O ₃ and Al ₂ O ₃ is 5 or more, and its crystal structure is not particularly limited.

The present invention is to treat and purify silicon hydride containing phosphine with a zeolite adsorbent other than mordenite _having a (SiO ₂ / Al ₂ O ₃ ) _{molar ratio of} ≦ 5 as described above.
Next, the conditions for purification using zeolite will be described.

The adsorption treatment can be carried out under reduced pressure or under pressure, but is preferably atmospheric pressure or higher. Silicon hydride may be in a gas phase or a liquid phase, but it is usually preferable to carry out in a gas phase. The adsorption treatment temperature is not particularly limited in the present invention, but it varies depending on the type of silicon hydride, and is preferably -80 to 30 ° C for SiH ₄ , -30 to 50 ° C for Si ₂ H ₆ , and Si ₃
It is 0 to 100 ° C. for H ₈ and 0 to 150 ° C. for Si ₄ H ₁₀ . At temperatures lower than this range, adsorption of silicon hydrogen, particularly monosilane becomes remarkable, which is not preferable, and at high temperatures, the amount of PH ₃ adsorbed decreases, which is not preferable.

The content of PH ₃ in silicon hydride is not particularly limited,
It is usually 1% or less, particularly 0.1% or less. Further, silicon hydride may contain a gas other than PH ₃ (for example, hydrogen, nitrogen, rare gas, methane, etc.).

It is also possible to use together with an adsorbent other than the present invention.

The novel adsorbent for removing PH ₃ in the present invention is characterized by having a larger adsorption capacity than conventionally known adsorbents.

Hereinafter, the present invention will be described with reference to examples.

<Example 1> Zeolite TSZ-is placed in an adsorption tube having an inner diameter of 3 mm and a length of 42 mm.
320NAA (Toyo Soda Co., Ltd. (SiO ₂ / Al ₂ O ₃ ) _{molar ratio}
= 5.6, faujasite structure, 30 to 60 mesh). After treatment in helium at 400 ° C for 1 hour and under reduced pressure (0.2mmHg) for 2 hours, the temperature of the adsorption tube was set to -20 ° C and SiH ₄ gas containing 279ppm of PH ₃ was supplied at a flow rate of 36ml / min (line). Speed 8.5 cm / sec, contact time
It was distributed in 0.49 sec). PH _{3 in} the exit gas from the adsorption tube
The concentration was sequentially analyzed by gas chromatography using FPD as a detector. The low-concentration PH ₃ was analyzed by the concentration analysis method proposed by the present inventors.

The results are shown in Fig. 1. From Fig. 1, the adsorption capacity (the point where the pH ₃ concentration at the adsorption tube outlet is 10 ppb, the same applies hereinafter) is approximately 4 mg.
・ It was found to be a PH ₃ / g adsorbent.

<Example 2-8> Example 1, which was synthesized according to Example 16 of the zeolite ZSM-5 (Mobil Oil Shatoku HirakiAkira 56-73618 _{adsorbent; (SiO 2 / Al 2 O} 3) _{molar ratio} = 65, pentasil structure, 30 to 60 mesh) 0.25 g,
ZSM-12 (Mobile Oil Company, JP-A-56-7361
Synthesized according to Example 9 of 8; (SiO ₂ / Al ₂ O ₃ ).
_{Molar ratio} = 338, 30 to 60 mesh) 0.25 g,
NU-10 (synthesized according to Example 7 of JP-A-57-200218 by ICI; (SiO ₂ / Al ₂ O ₃ ) _{molar ratio} = 8
7, ZSM-22 type structure, 30 to 60 mesh) 0.
25 g, EU-7 (ICI company, JP-A-59-88310
According to Example 1 which were synthesized _{(SiO 2 / Al 2 O 3} ) _{molar ratio}
= 60) 0.25 g, TPZ-2 (synthesized according to Example 1 of Teijin Yuka Kogyo, JP-A-57-149819;
(SiO ₂ / Al ₂ O ₃ ) _{molar ratio} = 100, ZSM-23 type structure, 30 to 60 mesh) 0.25 g ISI-2 (New Fuel Oil Development Technology Research Association, Example 2 of JP-A-59-73428) Synthesized: (SiO ₂ / Al ₂ O ₃ ) _{molar ratio} =
76, ZSM-39 type structure, 30 to 60 mesh)
0.25 g, LZ-132 (UCC, JP-A-58-1)
81720 synthesized according to Example 1 (SiO ₂ / Al ₂ O
₃ ) _{Molar ratio} = 27, ZSM-45 type structure, 30 to 60
Example 1 except that 0.25 g of each mesh was used.
An experiment was conducted in the same manner as in.

The adsorption capacities in these cases were as shown in Table 1, respectively.

<Comparative Examples 1 to 3> Molecular Sieve 3A (manufactured by Nishio Industry Co., Ltd. (SiO ₂ / Al
₂ O ₃ ) _{Molar ratio} = 1.0, 48% of exchangeable cations of 30 to 60 mesh) exchanged with zinc ions;
Molecular Siboo 4A (made by Union Carbide,
82% of the exchangeable cations of (SiO ₂ / Al ₂ O ₃ ) _{molar ratio} = 1.0 30 to 60 mesh were exchanged with silver ions; and Molecular Sieve 13X (manufactured by Devison Co., Ltd., (SiO 2 Example 2 except that 0.25 g of each of ₂ / Al ₂ O ₃ ) _{molar ratio} = 1.4 and 30 to 60 mesh) was used.
Pretreatment was carried out in the same manner as above, and an adsorption experiment was conducted.

The adsorption capacities in these cases were as shown in Table 1, respectively.

<Comparative Example 4> In Comparative Example 1, the molecular sieves 3A exchanged with zinc after the completion of the adsorption test was subjected to a reduced pressure (0.1 mmHg) at 350 ° C.
Was heated and regenerated for 2 hours. After that, the regenerated adsorbent was set at -20 ° C and the same experiment as in Example 1 was conducted.

The results are shown in Table 1, and the adsorption capacity is 1/3 of the first.
Fell below.

Further, this adsorbent was again treated under reduced pressure in the same manner, and the regeneration was repeated twice, resulting in an adsorption capacity of 1 mg / g.adsorbent or less.

EFFECTS OF THE INVENTION The specific adsorbent in the method of the present invention has an excellent adsorption capacity such that it has a large adsorption capacity and can be regenerated as shown in the examples. In particular, there have been almost no reports of adsorbents effective in removing pH _{3 in} Si ₂ H ₆ , Si ₃ H ₈ , and Si ₄ H ₁₀ in the past,
Only by the method of the present invention is an effective pH ₃ removal purification method provided.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the pH ₃ concentration in the adsorption tube outlet gas and the pH ₃ adsorption amount.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-101411 (JP, A)

Claims (2)

[Claims] 1. A silicon hydride containing phosphine is added to S
SiO ₂ and Al ₂ O ₃ are included in the constituents, and SiO
₂ and Al ₂ O ₃ content molar ratio, (SiO ₂ / Al
_A method for purifying silicon hydride, which comprises treating with a synthetic or natural zeolite adsorbent other than mordenite, which has a ₂ O ₃ ) molar ratio of 5 or more. 2. The method according to claim 1, wherein the silicon hydride is silane or disilane.