Patent Description:
Many semiconductor tools and clean rooms are situated in locations, such as in particular Taiwan, in which landfill space and disposal of manufacturing equipment is expensive. Because the available landfill space is very limited, the Taiwan Environmental Protection Agency (EPA) has adopted a strategy favoring combustion as the primary method of municipal solid waste treatment to be complemented by landfilling. Therefore, starting from <NUM>, the Taiwan government set up a long term plan for the construction of WTE (Waste to Entergy) plants. According to the Engineering Project for the Construction of WTE plants in Taiwan, <NUM> WTE plants were to be constructed by the government by <NUM>.

Plastic has a very high heat value, and therefore it is very wasteful to bury it in landfill. However, in general, Airborne Molecular Contamination (AMC) filters used in semiconductor tool and clean room applications are typically constructed of absorbing media permanently bonded to metal housings, which makes it difficult to dispose of, recycle or reuse such filters. Conventionally, labor is expended in separating the metal cases of such filters from the glued-in filter media.

Some filter designs attempt to address the need for re-usability by using loose granular adsorbent, which is re-used by pouring the granular adsorbent out of a re-used metal housing and pouring in fresh adsorbent. Other attempts have been to regenerate filter media.

There is, however, an ongoing need to address concerns and reduce costs involved in the disposal of AMC filters for semiconductor tools and clean room applications
<CIT> discloses a filter pack in which multiple insertion pieces are inserted between the pleats of a folded filter medium. <CIT> discloses an air purification filter having a casing and a filter part. The filter part if a flexible filter and is detachable from the casing. <CIT> discloses a regenerable pleated media and filter elements for use in a clean room environment for removal of airborne molecular contamination.

The present invention provides a filter cartridge system for control of airborne molecular contamination according to the claims.

The present disclosure is directed to filters suitable for use in semiconductor tool and clean room applications to control airborne molecular contamination (AMC). The filter cartridge system includes a filter cartridge having a non-woven fiber and at least one adsorbent. In some embodiments, the filter cartridge is constructed of substantially combustible materials to support its end of service destruction.

The substantially combustible filter cartridge is placed into a reusable case to complete the filter cartridge system. Non-limiting factors considered in designing the reusable case include weight, durability, shape retention, handling, and flame resistance, among others. In one embodiment, the also reusable case for the filter cartridge is metal. In application and use, the filter cartridge is readily separable from the reusable case for disposal.

The preceding summary is provided to facilitate an understanding of some of the innovative features unique to the present disclosure and is not intended to be a full description. A full appreciation of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings, in which:.

Conventional filters for molecular contaminants used in semiconductor tool and clean room applications are usually constructed of adsorbing media bonded to metal housings. This makes recycling the metal and plastic media expensive or impossible. Also, the cost of the filter is high because the metal housing is not reused.

In accordance with a version of the invention, there is provided an AMC filter made out of substantially combustible materials, which is used in conjunction with a reusable housing, and preferably a metal housing. Such a filter system provides the advantage, for example, of permitting disposal of the substantially combustible filter by incineration, while the metal housing can be reused. Further advantages can include, for example, that the filter system can reduce the cost of ownership, reduce the number of parts needed in filter assembly, reduce the labor involved in disposal and reduce environmental impact.

<FIG> is a diagram of a filter cartridge system <NUM> in accordance with a version of the invention, which provides a disposable filter cartridge <NUM> that can fit into a reusable metal frame <NUM> (shown in <FIG>).

<FIG> is a diagram showing a reusable metal frame <NUM> with which a disposable filter cartridge <NUM> (see <FIG>) may be used, in accordance with a version of the invention. <FIG> shows placement of a bottom metal screen <NUM>, which can be used beneath the filter pleat pack, inside the metal frame <NUM>, in accordance with a version of the invention. A top metal screen 204may also be used, above the filter pleat pack, and may slide as shown in <FIG> into the top of the metal frame <NUM>. The metal screens <NUM>, <NUM> of <FIG> may include a thin layer of scrim material on the metal screens, and may include closed-cell polyethylene foam around the edges of the screens. The metal frame <NUM> may for example meet semiconductor manufacturing specifications, and may for example comprise an anodized aluminum frame. In another version according to the invention, the filter cartridge <NUM> may be secured into the metal frame <NUM> using clamps, such as toggle clamps, which can be used in conjunction with matching indents in a glue bed of the filter cartridge <NUM>.

<FIG> is an exploded view diagram of a filter cartridge system in accordance with a version of the invention. The filter cartridge system includes a filter pleat pack <NUM>, filter pleat comb separators <NUM>, side panels <NUM>, hot melt glue <NUM> and a screen <NUM>. The filter pleat comb separators <NUM> can be made, for example, of a plastic such as laser-cut polypropylene.

<FIG> is a diagram illustrating a process for potting (or casting) a filter cartridge in accordance with a version of the invention. The filter is potted in a mold with no extra components, relying on the glue bed itself for structure. The mold uses a PTFE coated aluminum sheet <NUM> as the base, which can include hinges <NUM> to assist with removal of the filter from the mold after curing. The PTFE coating produces a smooth surface and makes the mold durable. An alignment fixture <NUM> is also used, which suspends the filter pleat pack in space so that it fits into the ultimate shape, and ensures that the filter is square when potted on the other side. In accordance with one version of the invention, the potting material may be Hot Melt Polyethylene (HMGE), such as nitrogen-foamed polyethylene, although other types of hot melt glue may be used. The glue is poured into a pan lined, for example, with Teflon-reinforced fiberglass cloth and steel bars. When the glue cools and hardens, the filter is pealed out of the mold.

<FIG> are diagrams illustrating use of an alignment fixture <NUM> in potting (or casting) a filter cartridge in accordance with a version of the invention. The glue bed <NUM> from potting the first side is aligned with locator pins <NUM> in the frame. The frame is then aligned with the jig using locator pins <NUM>.

In accordance with a version of the invention, a membrane, such as a screen <NUM> (see <FIG>), is used to separate the filter pleat pack from the outside of the mold. The main goals are to disguise the exposed carbon of the filter pleat pack for aesthetic purposes; to contain any carbon that may have breached the potting bed; and to assist with meeting flammability requirements. <FIG> is a diagram of a screen <NUM> used as such a membrane in accordance with a version of the invention. The screen <NUM> offsets the exposed carbon of the filter pleat pack from the edge of the cartridge, and disguises the pleat pack. A screen mesh opening size of, for example, less than about <NUM>, such as about <NUM>, and a screen thickness of less than about <NUM>, may be used. To affix the screen <NUM> to the filter pleat pack, pushing the screen through the glue with the pleat pack, after the glue has been poured, may be used, with results as shown in <FIG>.

In accordance with a version of the invention, edge sealing of the filter pleat pack media may be used, for example edge sealing of scrim materials on the pleat edges of the pleat pack. This permits retaining of the carbon in the filter media where no particle screen barriers are used on the filter pleat pack. The pleat pack may include one or more layers of scrim, surrounding one or more layers of high loft. Both the scrim and the high loft may include non-woven materials, such as polyester fibers, and a binder. The high loft material may include an adsorbent, such as a carbon or ion exchange adsorbent, and may include mixed adsorbents. As used herein, "edge sealing" of the filter pleat pack media comprises sealing the pleat edges of a non-woven fiber material. Such "edge sealing" differs from the "four-sided seal" referred to herein and below, which latter term refers to an air seal around the filter pleat pack, for example formed using a single component hot melt material.

As used herein, "substantially combustible materials" can, for example, include greater than about <NUM>% by weight of combustible materials, or greater than about <NUM>% by weight of combustible materials, or greater than about <NUM>% by weight of combustible materials, greater than about <NUM>% by weight of combustible materials, or greater than about <NUM>% by weight of combustible materials, or greater than about <NUM>% by weight of combustible materials, or only combustible materials.

In accordance with a version of the invention, non-woven materials used in the filter pleat pack can be any of a variety of different possible material types, fiber sizes and binding material. Polyester fiber, of varying sizes, using ethyl-vinyl-chloride as a binder can be used. This polyester fiber can be randomly oriented or machine oriented, for example by being carded. Other types of fibers can be used, including bi-component fibers, such as bi-component fibers that include a polyethylene outer shell and a polyester core. Bi-component fibers can be used without binder.

In accordance with a version of the invention, adsorbents used in the filter pleat pack can, for example, be single granular material type, or mixes of different types of granular material types. For example, activated carbon mixed with ion exchange can be used. Activated carbon can be treated with a variety of different possible chemistries, each of which target different contaminants. An example of a mix ratio that can be used is <NUM>% granular activated carbon with <NUM>% ion exchange resin. Another mix ratio that can be used is <NUM>% base treated granular activated carbon with <NUM>% ion exchange.

In accordance with a version of the invention, the walls of the filter cartridge can be formed using hot melt material in molds. Other adhesives can be used. The hot melt adhesive can, for example, be a low temperature melting adhesive of a single material such as polyethylene. Other hot melt materials used can be other types of polyolefin. In accordance with a version of the invention, the material should be low out-gassing for pure air applications. The hot melt adhesive can be injected with nitrogen gas and foamed, to reduce weight and cost. Hot melt adhesive can provide the advantage of solidifying in a minimal time period. In accordance with a version of the invention, the hot melt material does not adhere to Teflon, so that the molded parts can be readily removed from molds.

In accordance with a version of the invention, the filter cartridge can include any of the materials taught in <CIT>, the entire teachings of which are hereby incorporated herein by reference, for example, in particular, the filter cartridge can include non-woven materials and adsorbents taught therein.

In accordance with a version of the invention, a side panel is used to provide enough rigidity to maintain gasket pressure along the entire perimeter of the filter. A strong, lightweight, inexpensive material may be used for the side panel, such as about <NUM> corrugated polypropylene panel.

<FIG> illustrates a technique of attaching the side panel <NUM> in accordance with a version of the invention. The side panel <NUM> is attached while laying the bead flap. This provides clean corners, and uses no direct attachment to the glue bed. <FIG> are diagrams illustrating a technique of reinforcing the side panel to accommodate lifting force, by embedding the ends of the pleat separators <NUM> into the bead <NUM>, which has been found to add significant strength to the filter cartridge. In <FIG>, it can be seen that pleat separator combs <NUM> include a feature that grips the glue bead <NUM>.

<FIG> is a cross-sectional view of a filter cartridge system in accordance with a version of the invention, showing potting of the filter bead flap side combs to the side panel of the filter. Flood filling of glue <NUM> is used on either side of the filter bead flap <NUM>. This permits a large glue surface area to connect to the filter, and helps to stiffen the panel and improve gasket pressure distribution. In addition, flood-filling of the filter pleat pack in a solidifying bath of hot melt, to form a four-sided seal around the filter pleat pack, can, for example, be used. In accordance with a version of the invention other techniques of forming a four-sided seal around the filter pleat pack can be used, which may, for example, include forming the four-sided seal with a single-component hot melt material, or by using a multi-component adhesive or other adhesive to form the four-sided seal.

In accordance with a version of the invention, one or more steps of molding and sealing the filter cartridge can, for example, be performed in a different order, for example by forming at least a portion of a four-sided seal prior to molding at least a portion of the filter cartridge. In one example, the filter cartridge is molded prior to forming the four-sided seal.

<FIG> is a diagram showing a handle <NUM> for the side panel <NUM> of the filter cartridge, in accordance with a version of the invention. The top-placed blind handle <NUM> is die cut and punched from the corrugate of the side panel <NUM>. Such a handle provides a simple design, at low cost in high volume; with a large profile, ergonomic design. The side panel <NUM> is reinforced by the glue and filter pleat separator comb <NUM>, which extends along the length of the pleat pack <NUM> to the side panel (not shown) on the opposite side of the filter cartridge, thereby tying the side panels <NUM> to the filter pleat pack and acting as a structural member for the cartridge. To manufacture the handle <NUM>, the handle <NUM> can, for example, be die cut to form a flap that folds upward. The side panel <NUM> is placed on a potting fixture, where a steel die forces the handle into the right shape. The pleat separators <NUM> are glued onto the glue strips (see <FIG>).

In accordance with a version of the invention, the filter cartridge is one that achieves superior outgas and particle discharge results for use in applications such as, for example, reduction of Airborne Molecular Contamination (AMC). For example, the filter cartridge system may be one that passes International Organization for Standardization (ISO) <NUM>-<NUM> Cleanroom Standards at the Class <NUM>, Class <NUM>, Class <NUM>, Class <NUM> or even Class <NUM>, level for particle discharge. The entire teachings of the ISO <NUM>-<NUM> Cleanroom Standards are hereby incorporated herein by reference, including particularly the particle discharge standards at the Class <NUM>, Class <NUM>, Class <NUM>, Class <NUM> and Class <NUM> levels. The following table (Table <NUM>) illustrates particle discharge requirements that may be met by the filter cartridge system:
<IMG>.

For example, for ISO Class <NUM>, the filter cartridge system discharges less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> micron; and less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns. For ISO Class <NUM>, the filter cartridge system discharges less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> micron; and less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns. For ISO Class <NUM>, the filter cartridge system discharges less than about <NUM>,<NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns; less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> micron; and less than about <NUM> particles per cubic meter with a particle size greater than or equal to about <NUM> microns. Other ISO Classes may be met, in accordance with Table <NUM>, by having the filter discharge less than about the number of particles per cubic meter that are shown in Table <NUM> for each class, with a particle size greater than or equal to about the particle sizes shown in columns in Table <NUM>. In addition, the filter cartridge may reduce total airborne molecular contaminant concentrations from about <NUM> to about <NUM> ppb upstream of the filter cartridge system to less than about <NUM> ppb to about <NUM> ppb downstream of the filter cartridge system. Further, the filter cartridge may achieve a removal efficiency of at least about <NUM>% or greater at inlet contaminant concentrations of up to about <NUM> ppb, such as about <NUM>% or greater for specified contaminants.

<FIG> is a schematic diagram illustrating contexts in which an AMC filter system in accordance with a version of the invention may be used. The filter system may be used in semiconductor manufacturing and cleanroom contexts; and may be used both in the plenum <NUM>, as a clean room ceiling chemical air filter <NUM>, and as a tool-level AMC filter <NUM> on the fabrication level; and can be used for any tool (such as a baking tool, an etch tool, etc.).

In accordance with a version of the invention, one advantage that can be achieved is that no expensive injection molds need to be built. This reserves potential to use a universal mold fixture for other filter sizes and applications. Another advantage is that a durable metal housing can be re-used, thereby reducing cost. The cartridge can, if desired, be used without the re-usable metal case in less critical applications, which means that the same cartridge element can be used for both critical tool and general clean room applications. The re-usable metal housing can allow the meeting of flammability requirements, such as fire codes. Overall, the filter cartridge system can reduce costs for a user, while affecting the environment less than traditional filters.

In accordance with the invention, the cartridge filter is made out of substantially combustible materials, for example only combustible materials, and is used in conjunction with a re-usable metal housing to save cost while maintaining specifications for durability, particle discharge, aesthetics, and fire rating.

In accordance with a version of the invention, a filter element, made out of substantially combustible materials, which may be only combustible materials, is used in conjunction with a re-usable metal housing. Materials in the cartridge are plastic and substantially combustible media such as carbon and resin. This cartridge enclosure is molded using low cost hot melt glue molded in low cost open molds. In order to maintain structural integrity, plastic pleat separators are joined to the hot melt and joined to the plastic corrugated side panels. To prevent media exposure, plastic screen mesh is used as a separator that keeps media internal to hot melt adhesive. Stick-on plastic membranes may be employed for aesthetic value and to encapsulate media.

In accordance with a version of the invention, the filter cartridge is used in conjunction with a re-usable metal case, though it could be used without. The re-usable metal case assists with requirements for aesthetics, particle discharge, cost, and durability. In order to reduce cost further, media protective metal screens can be loosely assembled via a slot and flange in the metal case for easy removal.

It must also be noted that as used herein and in the appended claims, the singular forms "a", "an", and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to a "filter pleat pack" is a reference to one or more filter pleat packs and equivalents thereof known to those skilled in the art, and so forth. All numeric values herein can be modified by the term "about," whether or not explicitly indicated.

Claim 1:
A filter cartridge system for control of airborne molecular contamination, the filter cartridge system (<NUM>) comprising:
a filter cartridge (<NUM>) comprising a non-woven fiber and at least one adsorbent, the filter cartridge comprising combustible materials, wherein the filter cartridge comprises a filter pleat pack (<NUM>); characterised in that:
the filter pleat pack has a four-sided seal formed by solidification of a single-component hot melt material (<NUM>),
wherein the filter cartridge further comprises plastic pleat separators (<NUM>) and plastic side panels (<NUM>), wherein the plastic pleat separators are joined to the hot melt material and joined to the plastic side panels; and
a reusable case for the filter cartridge, the filter cartridge being separable from the reusable case for disposal.