JPH0699129B2 - 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 content concentration of the impurity hydride in the raw material silane gas is a sub-ppm level, and these influences on the above electrical characteristics are eliminated. It is not easy to remove the ppb order or less as possible. 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. A processing agent for purifying silane by using a mixture of zinc oxide and alumina 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 zinc oxide and alumina with sufficient silane, and phosphine, arsine, and diborane contained as trace impurities in the raw material gas. The method for purifying silane is characterized by adsorbing a gaseous hydride such as, for example, to selectively remove the hydride that is the trace impurity from the raw material silane gas to purify silane.

[0006]

When the raw material silane gas is brought into contact with the refining agent containing a mixture of zinc oxide and alumina as a main component, silane is first adsorbed and saturated in the refining 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 oxidized and 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 technique for purifying silane by applying a treating agent containing a mixture of zinc oxide and alumina as a main component to remove hydrides such as phosphine which is a trace amount of impurities is completely novel. Moreover, this silane purification agent is a combination of ordinary oxides and can be implemented inexpensively, and can be satisfactorily removed even if the impurity hydride content is 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]

[Examples] Sodium carbonate and the like were added to an aqueous solution of zinc nitrate and aluminum sulfate to form a precipitate, which was calcined to obtain a mixture having a component ratio of 10 wt% zinc and 90 wt% alumina. This was crushed and then molded into a spherical shape with a tablet molding machine to prepare a silane purification treatment agent. In this case, as the zinc oxide and the alumina, commercially available products may be used, or instead of molding both of them as they are, an aqueous solution of zinc nitrate is impregnated in the alumina gel and heated to support the zinc oxide on the alumina gel. It doesn't matter.

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 contained in the raw material silane gas as trace impurities are adsorbed to the refining treatment agent, and these trace content impurities such as hydride are removed. Selectively remove. 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 present 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 filled with 26 g of the above-mentioned purification treatment agent, and the raw material silane gas was used as a 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, phosphine 3000ppm and arsine 17 as raw materials
Silane gas containing 00 ppm and 300 ppm diborane was used.

As a result, the concentration of the outlet impurities became ND at the same time when the raw material silane gas was started to flow. When the concentration measurement was continued, the above-mentioned purification treatment agent was confirmed to break through after 0.52 hours. In this case, the total amount of impurity hydride removed per unit weight was estimated to be 1.5 Nl /
It was 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 zinc oxide and alumina as a main component. A silane refining treatment agent characterized by the above. 2. A phosphine contained as a trace impurity in the raw material gas by bringing the raw material silane gas into contact with a refining treatment agent subjected to silane passivation by adsorbing and saturation a mixture of zinc oxide and alumina with sufficient silane,
A method for purifying silane, which comprises adsorbing a gaseous hydride such as arsine or diborane to selectively remove the hydride that is the trace impurity from the raw material silane gas to purify silane.