Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Reexamination Certificate
2000-09-28
2002-09-10
Smith, Duane S. (Department: 1724)
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
C095S133000, C095S141000, C095S143000, C096S153000, C423S245100, C502S244000, C502S345000
Reexamination Certificate
active
06447576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cleaning agent and a cleaning process for cleaning a harmful gas containing a harmful organometallic compound represented by the general formula:
Rm—M—Hn
wherein R is alkyl, M is As, P, S, Se or Te, and m and n are each positive integer satisfying the relation: m+n=valence of M. More particularly, the invention relates to a cleaning agent and a cleaning process for cleaning a harmful gas from MOCVD (metal organic chemical vapor deposition) process or other CVD processes in the production of semiconductors.
2. Description of the Prior Art
The recent development in semiconductor industries promotes the high integration and miniaturization of semiconductor devices. This brought about an increased use of organometallic compound gases such as t-butylarsine, t-butylphosphine, t-butylthiol, isopropylarsine and isopropylphosphine in place of arsine hydride gas, phosphine hydride gas, etc. which have been conventionally used. The use of such organometallic compound gases as a feed gas, a doping gas or a gas for forming thin metal films comes to be essential particularly in CVD process.
However, many of these organometallic compounds represented by the general formula:
Rm—M—Hn
wherein R, M, m and n are as defined above (hereinafter may be referred to merely as “alkylmetal hydride”) are highly toxic or doubtful about their safety, and most thereof are highly flammable. Therefore, these alkylmetal hydrides have been required to be removed from an exhaust gas prior to its discharge into atmosphere.
Known cleaning process for harmful gases containing an alkylmetal hydride includes a wet process in which the harmful gases is absorbed and decomposed by a scrubber, and a dry process using a porous adsorbent such as activated carbon and inorganic compounds. In the wet process, since the alkylmetal hydrides are not soluble in water, no effective absorbing solution has been proposed. In the dry process, since the adsorption on activated carbon is a physical process, the desorption of the adsorbed gas is likely to occur. In view of these circumstances, the inventors have proposed various cleaning agents and cleaning processes for cleaning a harmful gas containing an alkylmetal hydride in dry process.
For instance, Japanese Patent Application Laid-Open No. 7-68128 proposes a process of cleaning a harmful gas containing a harmful alkylmetal hydride of arsenic, phosphorus, sulfur, serene or tellurium by contacting the harmful gas with a cleaning agent comprising a metal oxide, which is mainly composed of copper (II) oxide and manganese dioxide, incorporated with an alkali metal compound. Japanese Patent Application Laid-Open No. 7-60054 proposes a process of cleaning a harmful gas containing the alkylmetal hydride by contacting the harmful gas with a cleaning agent comprising a metal oxide, which is mainly composed of copper (II) oxide and manganese dioxide, incorporated with a cobalt (II) compound.
The above known cleaning processes have been developed for the purpose of attaining a high cleaning efficiency (removed amount of alkylmetal hydride per unit amount of cleaning agent) in the cleaning of a harmful gas containing the alkylmetal hydride by a cleaning agent basically made of a two-component system of copper (II) oxide and manganese dioxide. In the process of cleaning the harmful gas, a hopcalite catalyst has been used as the metal oxide mainly composed of copper (II) oxide and manganese dioxide due to its easy availability. However, since the alkylmetal hydride-containing harmful gas from semiconductor manufacturing process usually contains hydrogen, the cleaning agent which is substantially the two-component system of copper (II) oxide and manganese dioxide is liable to be reduced by hydrogen, thereby making the cleaning agent ineffective. Therefore, to make the cleaning agent resistant to reduction, it has been proposed to add another component to the two-component system of copper (II) oxide and manganese dioxide.
In the process using a cleaning agent comprising a metal oxide mainly composed of copper (II) oxide and manganese dioxide added with an alkali metal compound, it is intended to inhibit the reduction of the cleaning agent by incorporating the alkali metal compound. However, this process in turn fails to attain a satisfactory cleaning efficiency. In the process using a cleaning agent comprising a metal oxide mainly composed of copper (II) oxide and manganese dioxide added with a cobalt (II) compound, a high cleaning efficiency can be attained since the cobalt (II) compound not only acts as an inhibitor against the reduction by hydrogen but also reacts with the alkylmetal hydride to form a complex. However, it has been found that the alkylmetal hydride once adsorbed on the cleaning agent is desorbed when allowed to stand for a long time because the complex is unstable.
Accordingly, an object of the present invention is to provide a cleaning agent and a cleaning process for cleaning a harmful gas containing an organometallic compound represented by the general formula: Rm—M—Hn wherein R, M, m and n are as defined above, which are excellent in the cleaning efficiency and free from desorption of the organometallic compounds adsorbed on the cleaning agent.
SUMMARY OF THE INVENTION
As a result of extensive research in view of the above object, the inventors have found that a one-component cleaning agent containing, as the main component, copper (II) oxide having a BET specific surface area of 10 m
2
/g or greater or a two-component cleaning agent containing, as the main component, 0.3 part by weight or less of manganese dioxide having a BET specific surface area of 130 m
2
/g or greater per 1 part by weight of copper (II) oxide having a BET specific surface area of 10 m
2
/g or greater show a high cleaning efficiency without causing reduction by hydrogen and desorption of the harmful components adsorbed on the cleaning agent, in the face of art recognition that a one-component agent containing only copper (II) oxide having a relatively small specific surface area generally employed in the known cleaning agents, and a two-component mixture containing copper (II) oxide and manganese dioxide each having a relatively small specific surface area are ineffective as the cleaning agent due to their low cleaning efficiency. The present invention has been accomplished on the basis of this finding.
Thus, in a first aspect, the present invention provides a cleaning agent for cleaning a harmful gas containing, as a harmful component, an organometallic compound represented by the general formula:
Rm—M—Hn
wherein R is alkyl; M is As, P, S, Se or Te; and m and n are each positive integer satisfying the relation: m+n=valence of M, the cleaning agent comprising, as an effective component, copper (II) oxide having a BET specific surface area of 10 m
2
/g or greater.
In a second aspect of the present invention, there is provided a cleaning agent for cleaning a harmful gas containing, as a harmful component, an organometallic compound represented by the general formula:
Rm—M—Hn
wherein R is alkyl; M is As, P, S, Se or Te; and m and n are each positive integer satisfying the relation: m+n=valence of M, the cleaning agent comprising, as effective components, 0.3 part by weight or less of manganese dioxide having a BET specific surface area of 130 m
2
/g or greater per 1 part by weight of copper (II) oxide having a BET specific surface area of 10 m
2
/g or great.
In a third aspect of the present invention, there is provided a process for cleaning a harmful gas containing, as a harmful component, an organometallic compound represented by the general formula:
Rm—M—Hn
wherein R is alkyl; M is As, P, S, Se or Te; and m and n are each positive integer satisfying the relation: m+n=valence of M, the process comprising:
contacting the harmful gas with a cleaning agent comprising, as an effective component, copper (II) oxide having a BET specific surface area of 10 m
2
/g or greater.
Amijima Yutaka
Hasemi Ryuji
Nawa Youji
Otsuka Kenji
Japan Pionics Co., Ltd.
Smith Duane S.
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