BACKGROUND OF THE INVENTION

Semiconductor manufacturing operations require high purity metals, such as tin, and high purity gases, such as hydrogen bromide, that are free from impurities, contaminants, and particulates that can disrupt processes and cause defects in work being produced. The filtration of molten metals in particular requires that filtration be performed at high temperatures and pressures. Filters for the filtration of molten metals must provide leak-proof seals at high temperatures, for example, temperatures greater than 200° C., and high pressures, for example, up to 8000 psig.

The devices and methods taught in the prior art do not necessarily meet the requirements of today's customers in the semiconductor industry. There is a continuing need for filters that provide leak-proof performance at high temperatures and pressures for the filtration of molten metals and gases.

SUMMARY OF THE INVENTION

This invention pertains to high pressure filters, as well as methods of making and using high pressure filters, for removing impurities, contaminants, and particulates that may be present in molten metals or gases.

In a version of the present invention, a high pressure filter comprises a first housing and a second housing, each of the housings having a tapered surface on a first end and a fluid fitting on a second end. The tapered surface of the second housing is tapered complimentary to the tapered surface of the first housing, and a gasket is located between the tapered surfaces of the first and second housings. A filter element is centrally disposed within the first and second housings. At least a portion of the exterior surface of the first housing is threaded and a compression collar is fitted over the second housing and threaded onto the first housing.

In a particular version of the invention, the first and second housings comprise molybdenum. Alternatively, the first and second housings comprise alumina, silicon carbide, stainless steel, nickel, or nickel alloys. The compression collar can comprise molybdenum, stainless steel, nickel, or nickel alloys. The gasket can comprise tantalum, titanium, stainless steel, nickel, or nickel alloys.

In another version of the invention, the tapered surface of the first housing is tapered at an angle different from the tapered surface of the second housing, which can enhance compression of the gasket located between the tapered surfaces. In versions of the present invention, high pressure filters are leak-proof at temperatures of about 200 to about 400° C., or of about 250 to about 300° C. High pressure filters of the present invention can be leak-proof during operation at a pressure of up to about 8000 psig.

In further versions of the invention, the gasket includes a flange, which can prevent slipping or movement of the gasket between the tapered surfaces of the housings. The filter element centrally disposed within the housings can be a sintered powder porous filter element. The fluid fittings can be VCR, Vacuum Coupling Radius seal fittings or compression fittings.

In another version of the invention, a method of filtering a liquid or gas feed comprises providing a high pressure filter, introducing a feed containing contaminants into the high pressure filter, and recovering the feed, purified from contaminants, from the high pressure filter. The feed can travel along a flowpath through the filter element, from the fluid fitting of the first housing to the fluid fitting of the second housing, with the contaminants remaining within the filter element. The feed can be a liquid metal or a gas.

In a further version of the invention, a method of making a high pressure filter comprises heating a first housing of a high pressure filter, fitting a sintered powder porous filter element into the first molybdenum housing, placing a gasket over a tapered surface of the first housing, placing a second housing with a complementary tapered surface in sealing contact with the gasket and the first housing, and threading a compression collar over the second housing and onto at least a portion of the first housing, thereby providing a leak-proof seal between the first and second housings.

