JPH0699128B2 - Silane refining agent and refining 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 silane refining agent and a refining method used for forming a semiconductor thin film, an amorphous solar cell, and a photosensitive drum, and a phosphine contained in a raw material silane gas as a trace impurity. A novel product that can efficiently remove arsine, diborane, etc. is provided.

[0002]

2. Description of the Related Art Generally, raw material silane gas is mixed with water, oxygen, carbon dioxide gas and the like during the production raw material and the production process. Therefore, these have conventionally been removed by a treating agent containing zeolite as a main component.

[0003]

However, the raw material silane gas contains hydrides such as phosphine, arsine, and diborane as trace impurities in addition to these, which adversely affect the electrical characteristics of the thin film formed on the wafer. It is necessary to remove it from the raw material gas for some reason, but it could not be effectively removed with the above zeolite treating agent.

On the other hand, the above-mentioned phosphine, arsine, diborane, etc. are used in an alkali absorption tower such as sodium hydroxide solution or F
It is possible to remove the FeCl ₃ absorption tower filled with the eCl ₃ adsorbent, but the method using the alkali absorption tower has a problem in that the entire apparatus is wet and the removal efficiency is low. Further, the method using the FeCl ₃ absorption tower is more efficient than the above-mentioned alkaline method, but the impurity content concentration in the raw material silane gas is a trace amount of sub-ppm order, and it is possible to eliminate the influence on the above electrical characteristics. It is not easy to remove even below ppb order. The present invention has a technical problem of precisely removing these minute amounts of impurity hydrides.

[0005]

Means for achieving the above object will be described below. In the present invention 1, gaseous hydrides such as phosphine, arsine and diborane contained as trace impurities are removed from a raw material silane gas. And a purification agent for silane, which is characterized in that it contains a mixture of copper oxide and zinc oxide as a main component. The present invention 2 is a method in which a raw material silane gas is brought into contact with a refining treatment agent subjected to silane passivation by adsorbing and saturation a mixture of copper oxide and zinc oxide with sufficient silane, and phosphine and arsine contained as trace impurities in the raw material gas A method for purifying silane, which comprises adsorbing a gaseous hydride such as diborane to selectively remove the hydride that is the trace amount of impurities from the raw material silane gas to purify silane.

[0006]

A mixture of copper oxide and zinc oxide is disclosed in JP-A-61-
As disclosed in Japanese Patent No. 90726, since it has a function of removing a gaseous silicon compound such as silane and silicon fluoride,
When the raw material silane gas is brought into contact with the purification treatment agent containing the mixture as a main component, silane is first adsorbed and saturated in the purification treatment agent. When the raw material silane gas is subsequently contacted, silane is no longer adsorbed on the purification treatment agent, and a small amount of hydride such as phosphine contained in the raw material gas is adsorbed on the purification treatment agent. The phosphine adsorbed on the purification treatment agent is oxidatively fixed from the hydride to the oxide by the catalytic action of the metal oxide of the treatment agent (for example, AsH ₃ → As
₂ O ₃ ). As a result, a small amount of the above-mentioned impurity hydride is removed from the raw material silane gas, and the silane is efficiently purified.

[0007]

The above-mentioned publication only discloses the removal of gaseous silicon compounds such as silane, and the treatment agent containing a mixture of copper oxide and zinc oxide as a main component is treated with a trace amount of impurities such as phosphine. The technology for purifying silane by applying it to the removal of hydrides of is completely new. Moreover, this silane purification agent is a combination of ordinary oxides and can be implemented at low cost, and can be satisfactorily removed even if the impurity hydrogenation content is very small. Further, in the refining method, since the raw material silane gas is simply brought into contact with the refining agent, the refining operation can be simply and quickly performed.

[0008]

EXAMPLE A sodium nitrate or the like is added to copper nitrate and zinc nitrate to form a precipitate, which is then calcined to form copper oxide,
A participating zinc mixture was obtained. After crushing this, it is mixed with a binder composed of graphite, gelatin, etc., and the mixed powder is molded into a spherical shape with a tablet molding machine to prepare a silane purification treatment agent with a component ratio of 50 wt% copper oxide and 45 wt% zinc oxide. did. In this case, copper oxide and zinc oxide may be commercially available products,
Instead of molding both of them as they are, it is also possible to impregnate a porous substance such as activated carbon or silica gel with a copper nitrate aqueous solution and a zinc nitrate aqueous solution, respectively, and evacuate or heat them to support both oxides on the porous substance.

When the raw material silane gas is continuously brought into contact with the obtained purification treatment agent, first, silane in the raw material silane gas is adsorbed and saturated with the purification treatment agent, and no further adsorption is possible. After that, when the raw material silane gas is subsequently contacted, gaseous hydrides such as phosphine, arsine, and diborane, which are contained as trace impurities in the raw material silane gas, are adsorbed to the purification treatment agent, and these impurity hydrides are selectively removed. To do. However, in the actual silane refining device, the zeolite-filled reaction tube shown in the above-mentioned prior art is connected in series on the downstream side of the reaction tube filled with the silane refining treatment agent, and the raw material silane gas further contains water and carbon dioxide gas. , Configured to remove oxygen, etc. in this case,
One reaction cylinder may be divided into a packing chamber for the purification treatment agent and a packing chamber for the zeolite.

Therefore, a test example using the present purification treatment agent will be described. A reaction cylinder having a passage cross-sectional area of 2.2 cm ² and a passage length of 135 cm was charged with 49 g of the above-mentioned purification treatment agent, and the raw material silane gas was used as the reaction cylinder temperature: room temperature, gas pressure of 760 Torr, and gas empty velocity of 5
The gas was passed through the reaction tube under the condition of 00 hr- ¹ and the concentration of each hydride of phosphine, arsine and diborane in the gas passing through the reaction tube was measured with a gas chromatograph over time. However, as raw materials, phosphine 3000ppm, arsine 1
Silane gas containing 700 ppm and 300 ppm of diborane was used.

As a result, at the same time when the raw material silane gas was started to flow, the outlet impurity concentration became ND. When the concentration measurement was continued, breakthrough of the above-mentioned purification treatment agent was confirmed after 32 hours. In this case, the total amount of impurity hydride removed per unit weight was estimated to be 49 Nl / Kg.

Claims (2)

[Claims] 1. A treatment agent for purifying silane by removing gaseous hydrides such as phosphine, arsine, and diborane contained as trace impurities from a raw material silane gas, and containing a mixture of copper oxide and zinc oxide as a main component. A silane refining treatment agent characterized by: 2. A raw material silane gas is brought into contact with a purification treatment agent subjected to silane passivation by adsorbing and saturation a mixture of copper oxide and zinc oxide with sufficient silane, and phosphine and arsine contained as trace impurities in the raw material gas. A method for purifying silane, which comprises adsorbing a gaseous hydride such as diborane to selectively remove the hydride that is the trace amount of impurities from the raw material silane gas to purify silane.