Substrate container with purge gas diffuser - Patent Application 20070122997

Abstract

A wafer container adapted for storing or transporting semiconductor wafers in a clean environment is described, including a container including a purge gas delivery device and a method for purging the environment within the container. In one aspect, the invention relates to a diffuser including an elongated body having a top end, a bottom end, a front wall, a rear wall, side walls, a height between the top and bottom ends, a width between the side walls, and a channel; a diffuser inlet that allows gas to flow into the channel; a diffuser outlet that has one or more openings in the front wall, the side wall, or both the front and side walls; a non-porous channel surface that has a non-porous rear wall surface and a non-porous side wall surface; and a flow control structure within the channel that directs the flow of gas along the length of the channel between the diffuser inlet and the diffuser outlet.

Description

[Technical Field]

[0001] The present disclosure relates to substrate containers ("wafer containers") useful for storing or transporting semiconductor wafers in a clean environment, and more particularly to containers that include a diffusion gas delivery device within the container and methods for purging the environment within the container. [Background technology]

[0002] Semiconductor wafers and the microelectronic devices formed on them are prepared by a series of precise processing steps, each performed under extremely clean conditions. Between these processing steps, the wafers may be moved from one processing location to another, for example, within a clean room or between two different clean rooms, using extremely clean conditions for the wafer during the move.

[0003] During wafer transfer between processing steps, specialized containers are used to hold and transport wafers during processing in a manner that prevents damage to the wafers and avoids the introduction of particle or environmental contamination (e.g., moisture) to the wafer surface. These specialized containers, sometimes called "wafer containers" or "wafer carriers," are designed to safely move semiconductor wafers in a manner that prevents physical damage to the wafers and avoids the introduction of particle or environmental contamination to the wafers. Exemplary wafer containers are sometimes called "SMIF pods" (standard mechanical interface pods), "FOUPs" (front-opening unified pods), or "FOSBs" (front-opening shipping boxes). In use, these containers enclose a space for containing multiple semiconductor wafers in an atmosphere that may be evacuated (i.e., under reduced pressure) or may contain a gas other than air, such as an inert gas.

[0004] A wafer container typically includes a multi-sided container body (e.g., a "shell") that defines the container interior, an opening to the interior on one side of the container body, a removable door adapted to cover the opening, and a means for creating a seal between the door and the container body, such as a gasket. One or more gas inlets and gas outlets are typically included as part of the container to allow for the introduction of desired gases into the interior to control the gaseous atmosphere within the container.

[0005] As microelectronic devices become smaller and the number of microelectronic features per wafer area increases, the devices become more sensitive to particles and environmental contaminants. The smaller the contaminant, the greater its impact on the microelectronic circuitry, and even molecular-level contaminants can cause yield loss. Therefore, constantly improving control of particle contamination is required during all stages of semiconductor wafer manufacturing, processing, transportation, and storage.

[0006] When a wafer container is used to transport wafers, the wafers are placed in the wafer container at a location within a clean room. A door is placed over the opening to seal the opening and enclose the interior. To control the atmosphere inside the carrier, the carrier typically includes valves and gas flow devices between the interior and exterior to allow gas to be removed from or added to the carrier interior. Thus, after the container is closed and sealed with wafers inside, the atmosphere inside the carrier can be evacuated, reduced pressure, or replaced with a desired atmosphere, such as an inert gas, as desired.

[0007] There is an increasing need to control the gaseous environment within wafer containers during handling in order to achieve or maintain high levels of cleanliness. Summary of the Invention

[0008] Wafer containers (also known as "substrate containers") typically include gas flow devices that introduce gases into the container interior to control the atmosphere within the container. The gas flow devices may include design and operation features that control or reduce the amount of contaminants that will be present within the container. For example, during the insertion or removal of wafers from the wafer container and the opening and closing of the door, trace amounts of environmental contaminants, such as dust, gaseous impurities, or moisture (water vapor), may be introduced from outside the container into the interior of the wafer container. If these impurities come into contact with wafers, the potential result is a reduced product yield of the resident wafers.

[0009] Wafer containers typically include gas flow openings or valves called "ports" that allow gas to enter the container interior. One purpose of the ports is to allow gas to be distributed into the container to fill the container interior with a desired atmosphere. A clean inert gas (purge gas) may be distributed into the container interior to replace the previous atmosphere. These ports may include an inlet port for injecting the purge gas into the container interior and an outlet port for exhausting the purge gas from the container.

[0010] For certain steps using a wafer container, purge gas may be distributed into the container interior from a diffuser device installed at the inlet port. For a given purpose, a particular flow profile of gas from the diffuser device may be advantageous. For many functions, it may be useful for the gas flow to be uniformly distributed along the length of the diffuser device. For other functions, a non-uniform flow of gas from the diffuser device (i.e., a non-uniform flow profile) may be desirable, for example, to distribute a greater amount of gas in a particular location of the container, such as an upper or lower portion of the container, compared to a lesser amount of gas in a different location of the container.

[0011] In some cases, it may be desirable to design the flow of gas dispensed from the diffuser device for particular conditions or for changing conditions or events that occur during use of the container. As an example, the diffuser may be designed to dispense gas with a particular gas flow profile during container opening, i.e., while the door is removed from a closed container.

[0012] In one aspect, the present invention relates to a front-opening wafer container. The container includes a container interior bounded by a bottom wall, a top wall, side walls, and a front opening, a door for sealingly closing the front opening, and a diffuser therein adapted to distribute gas therein. The diffuser includes an elongated body including a top end, a bottom end, a front wall, a rear wall, side walls, a height between the top and bottom ends, a width between the side walls, and a channel; a diffuser inlet that allows gas to flow into the channel; a diffuser outlet with one or more openings in the front wall, one side wall, or both the front wall and one side wall; and a flow control structure in the channel that directs the flow of gas along the length of the channel between the diffuser inlet and the diffuser outlet.

[0013] In another aspect, the invention relates to a diffuser that includes an elongated body including an upper end, a lower end, a front wall, a rear wall, side walls, a height between the upper and lower ends, a width between the side walls, and a channel; a diffuser inlet that allows gas to flow into the channel; a diffuser outlet that includes one or more openings in the front wall, one of the side walls, or both the front wall and one of the side walls; a non-porous channel surface that includes a non-porous rear wall surface and a non-porous side wall surface; and a flow control structure within the channel that directs the flow of gas along the length of the channel between the diffuser inlet and the diffuser outlet. [Brief explanation of the drawings]

[0014] [Figure 1A] 1 shows a diagram of one exemplary diffuser device described. [Figure 1B] 1 shows a diagram of another exemplary diffuser device as described. [Figure 1C] 10 shows a diagram of yet another exemplary diffuser device as described. [Figure 1D] 10A-10C show different views of yet another exemplary diffuser device described. [Figure 1E] 1 shows one view of yet another exemplary diffuser device described. [Figure 1F] 10 shows another view of yet another exemplary diffuser device described. [Figure 2A-2B] 1 shows an exemplary top view of the rear plate of an exemplary diffuser device, a side view of an exemplary diffuser device, and a flow profile of an exemplary diffuser device. [Figures 2C-2D] 1 shows an exemplary top view of the rear plate of an exemplary diffuser device, a side view of an exemplary diffuser device, and a flow profile of an exemplary diffuser device. [Figure 3A] 1 shows an exemplary substrate container as described; [Figure 3B] 1 shows an exemplary substrate container as described; DETAILED DESCRIPTION OF THE INVENTION

[0015] All figures are schematic and not to scale.

[0016] Described below is a wafer container that includes a container body having an interior and an opening for accessing the interior, a door for covering the opening, and one or more diffusers therein for distributing gas to the interior. The diffuser is a type of diffuser known as a "directional" gas diffuser, which is a type of diffuser used to distribute gas (e.g., "purge gas") to the interior of the wafer container with directional specificity relative to the diffuser. The diffuser includes a housing, a diffuser inlet, a diffuser outlet, and an open internal "channel" within the housing that connects the diffuser inlet to the diffuser outlet and allows fluid communication from the inlet through the channel to the outlet. The diffuser further includes one or more flow control structures within the channel, such as baffles, diverters, or cowls, that affect the flow of gas through the channel and through the diffuser between the inlet and outlet to provide a desired flow profile of the gas through the outlet.

[0017] The present disclosure also relates to a particular diffuser assembly, a wafer container including the diffuser assembly, and a method of using the diffuser as part of a wafer container including the diffuser.

[0018] The wafer container includes a multi-sided container body (sometimes referred to as a "shell") that defines a container interior adapted to house and support one or more semiconductor wafers. The body includes an opening (the "container opening") on one side of the container body that allows access to the container interior. The container also includes a door adapted to cover the opening and form a seal across the opening between the interior and exterior of the container.

[0019] A wafer container may typically include at least one inlet port for injecting gas, such as a "purge gas," into the container interior and at least one outlet port for evacuating gas from the container.

[0020] According to this specification, a wafer container includes an inlet including a diffuser device, or multiple inlets each including a diffuser device. The diffuser device or "diffuser" has a diffuser inlet that receives gas flowing into the diffuser, a diffuser outlet, and a channel extending into the housing between the diffuser inlet and the diffuser outlet to allow the gaseous fluid to flow into the diffuser, through the channel, and then through the diffuser outlet. The gas flow enters the diffuser inlet, flows through the channel due to induction from flow control structures in the channel, and then flows through the diffuser outlet to diffuse (disperse) the gas as it is distributed from the diffuser outlet into the wafer container.

[0021] The diffuser may be designed to distribute gas into the container according to a specific flow profile of the gas dispensed from the diffuser outlet for a particular wafer container design or for a particular step in which the wafer container is used. In certain circumstances, the diffuser may be adapted to distribute the flow of gas into the wafer container with high uniformity of the gas dispensed along the length of the diffuser and diffuser outlet. In other variations, it may be desirable for the gas dispensed from the diffuser to be delivered according to a flow profile from the diffuser outlet that varies along the length of the diffuser outlet. For example, the diffuser may be designed to deliver a larger flow of gas through one portion of the diffuser outlet, e.g., an end portion, and a relatively smaller flow of gas through a different portion of the diffuser outlet, e.g., a middle portion. The diffuser may deliver a larger flow of gas to an upper portion of the container and a relatively smaller flow of gas to a lower portion of the container, or vice versa, a smaller flow of gas to an upper portion of the container and a relatively larger flow of gas to an upper portion of the container.

[0022] In certain examples, the diffuser may distribute the flow of gas from the diffuser outlet according to a flow profile designed to provide a desired effect during a step of using the wafer container, such as in response to changing conditions or flow events occurring within the container during use.

[0023] One event that changes the conditions inside the container is the step of opening and closing the door to the container. When the door of a wafer container is removed during use, gas inside the container (the container "internal gas") and gas outside the container (the container "external gas") flow between the inside and outside of the container, with a simultaneous exchange of the internal and external gases occurring at the door opening. The external gas may contain higher levels of contaminants compared to the internal gas. Contaminants may include particles, chemical vapors (e.g., molecules of organic compounds, sometimes referred to as "volatile organic compounds"), and environmental vapors such as water vapor (humidity).

[0024] When the door is removed from the container opening, a natural exchange of gas occurs at the opening with the internal gas flowing out of the container through the opening while the external gas flows from the outside to the inside. An example of a useful flow profile of the gas distributed from the diffuser can be a flow profile that reduces the amount of external gas flowing from the outside to the inside of the container during the step of removing the door from the wafer container. The flow can exhibit any useful profile along the height or width of the diffuser. The flow can be uniform along the height, with the gas flow distributed to the upper, lower, and middle portions of the diffuser being substantially equal. Alternatively, the flow profile along the height of the diffuser can be non-uniform, with a higher flow rate from the upper end of the diffuser and a lower flow rate from the lower end of the diffuser, or a lower flow rate from the upper end of the diffuser and a higher flow rate from the lower end of the diffuser.

[0025] The particular flow profile from the diffuser can be selected based on the conditions within the substrate container or the process being performed within the substrate container, such as whether the door is open or closed, or the type of gas being introduced through the diffuser. Gas can be introduced through the diffuser at a profile useful for filling the container interior with a gaseous atmosphere. Alternatively, gas can be introduced through the diffuser at a flow profile useful for purging the atmosphere from the interior, which can be done with either the door open or the door closed.

[0026] The described diffusers include a diffuser housing (also referred to herein as the "diffuser body") that includes a first end (e.g., an upper end), a second end (e.g., a lower end), a front wall (which may include a diffuser outlet), a rear wall, side walls, and a diffuser inlet. The body defines a length between the first and second ends (which is the height when the body is oriented vertically, e.g., installed in a container), and a width between the side walls. Within the housing is an interior space, which may be called a "channel" (also called an open interior "passage" or "opening"), that connects the diffuser inlet and the diffuser outlet, and is defined by the interior surfaces of the front wall, rear wall, side walls, and ends, and by flow control structures, creating and enabling fluid communication between the diffuser inlet and the diffuser outlet.

[0027] Examples of channels may be configured with different interior spaces ("chambers") and structures relative to the interior surfaces of the front wall, side wall, and rear wall of the body, and to the flow control device. Specific spaces and structures include an inlet, an inlet chamber, a flow control device, a plenum chamber, and an outlet.

[0028] An inlet (called a "diffuser inlet" or "channel inlet") allows gas to enter the channel from a location external to the diffuser body. In some exemplary diffuser devices, an interior space called an inlet chamber connected to the inlet is located between the inlet and the flow control device. The flow control device separates the channel into portions including an inlet chamber and an outlet chamber (also called a "plenum chamber"). The plenum chamber is on the opposite side of the flow control device from the inlet chamber and is connected to an outlet (called a "diffuser outlet" or "channel outlet") that allows gas to pass from the channel into the interior of the substrate container containing the diffuser.

[0029] The inlet may be located anywhere along the length of the diffuser, such as at an end or along the length between the first and second ends. According to a particular example, the inlet may be located at an end of the diffuser or in the middle third of the length of the diffuser, for example, approximately midway between the first and second ends.

[0030] The diffuser outlet comprises one or more openings in a wall (front or side wall) of the housing or an end structure, such as in the front or side wall of the housing, in any useful form. In one example, the outlet may comprise a plurality of individual openings evenly distributed along the length of the front wall. Alternatively, the diffuser outlet may comprise a longitudinal slot extending (e.g., uniformly) along part or all of the length of the front or side wall. In these examples, the outlet may be a set of uniform (size and spacing) openings or a single uniform opening substantially uniformly distributed along the length of the diffuser through the side or front wall.

[0031] In other examples, the diffuser outlet may include one or more openings distributed non-uniformly along the length of the diffuser body on the front wall or side wall, e.g., with more or fewer, or larger or smaller, openings located in one portion of the front wall or side wall compared to another portion of the front wall or side wall based on the position along the length between the first and second ends. For example, the diffuser outlet may include more or larger openings near the first end or near the second end and fewer or smaller openings near the middle of the length of the front wall or side wall to cause the diffuser outlet to distribute a larger volume of gas from one or two ends of the diffuser and less gas in the middle portion of the length of the diffuser. In certain exemplary diffusers, an intermediate portion of the length of the diffuser body may not include any openings, for example, the central 1 / 5, 1 / 4, or 1 / 3 of the length of the diffuser body may not include openings and may not include a portion of the diffuser outlet, with the diffuser outlet being located only in the remaining end portions of the length of the diffuser body.

[0032] Additionally or alternatively, the diffuser outlets may include openings in the front wall that are distributed either uniformly or non-uniformly along the width of the front wall. When positioned vertically within a wafer container, the diffuser may be considered to include a front portion of the width (toward the front opening of the container), a rear portion of the width (toward the rear of the container interior), and an intermediate portion of the width (between the front and rear portions). The front portion may be the front half of the width, the front third of the width, or the front quarter of the width. The rear portion may be the rear half of the width, the rear third of the width, or the rear quarter of the width. The front wall may optionally include openings in only one of these portions, for example, the front half, the front third, or the front quarter of the width of the front wall.

[0033] Also optionally, the diffuser outlet may include openings that direct flow in a direction non-perpendicular to the surface of the diffuser body. The openings may pass through the front or side wall at a non-perpendicular angle to direct flow through the front or side wall toward the front of the vessel or toward the rear of the vessel when the diffuser is oriented vertically within the vessel.

[0034] To generate a desired flow profile from the diffuser, the diffuser body may include a diffuser outlet in the form of one or more openings of various sizes, positioned exclusively in the forward portion, exclusively in the rearward portion, or exclusively in an intermediate portion between the forward and rearward portions. As an example, for a diffuser positioned in the forward portion of the vessel near the vessel opening, the front wall of the diffuser may include a diffuser outlet opening only in the forward portion of the diffuser width. The diffuser outlet opening may be oriented toward or through the vessel opening, and the gas flow from the diffuser is designed to reduce the exchange of external and internal gases through the vessel opening during the step of removing the vessel door.

[0035] The diffusers herein are of a type called a "directional" diffuser, which is a type of diffuser used to distribute gas (e.g., "purge gas") in a directional manner. Directional diffusers include features that distinguish them from other common types of diffusers, such as "showerhead" diffusers, "tube" diffusers, "disk" diffusers, and "plate" diffusers. Directional diffusers have a configuration that includes an elongated diffuser body having a length between two ends, and a diffuser outlet on one side of the diffuser body, but not on all sides, that extends along the length of the body between the first and second ends.

[0036] The diffuser outlet may optionally include a diffuser membrane, a porous solid body that allows gaseous fluid flow through the porous body while being somewhat resistant to gas flow, allowing gas under moderate pressure to flow through the membrane as a dispersed or "diffused" flow directed from only one side of the diffuser housing. Gas enters the diffuser housing at the inlet, flows through channels along the length of the housing, is controlled, influenced, or diverted by flow control structures within the channels, and then exits the housing through the diffuser outlet and optional porous diffuser membrane on one or more sides of the diffuser body that do not surround the periphery of the diffuser body. The remainder of the housing (the sides not including the diffuser outlet) is a non-porous surface that surrounds the internal channel between the first and second ends along the length of the housing.

[0037] The diffuser is described as "directional" because gas is distributed directionally about the periphery of the diffuser when viewing the diffuser in the direction of the diffuser length. Gas flow from the diffuser outlet does not occur in all directions around the periphery (i.e., all 360 degrees around the periphery). Instead, the diffuser outlet is positioned on only a portion of the periphery, sometimes referred to as the outlet side of the housing. The portion of the housing where lateral flow occurs may be less than half of the entire periphery; for example, flow may occur over up to 180 degrees around the periphery, e.g., between 10 and 170 degrees, or between 20 and 150 degrees, or between 40 and 120 degrees.

[0038] A benefit of directional flow from a diffuser over less than the entire perimeter is the ability to control the direction and positioning of the gas flow into the chamber. The flow can be directed for the purpose of avoiding direct flow of gas into areas inside the chamber where particle contamination may be present. Direct flow of gas toward particle accumulation in areas inside the chamber can disturb and disperse the particles within the chamber, which is preferably avoided.

[0039] The directional diffuser has a length dimension between a first end and a second end, a width perpendicular to the length, and a depth perpendicular to the length and width. The directional diffuser is elongated, with the length being greater than the width and greater than the depth. Exemplary directional diffusers can have a length that is at least 2, 4, 5, 10, 12, 15, 20, or 30 times the depth or width, or both, measured at the exterior surface of the housing.

[0040] According to this specification, a diffuser includes a channel within a housing and a wall of the channel that includes a flow control structure, which may be the rear wall, the front wall, or both the rear and front walls. The wall of the channel includes a "base surface" that covers a majority of the wall surface. The rear wall may include a rear wall base surface and may include one or more flow control structures that extend into the channel from the base surface a distance above the base surface. The base surface of the rear wall extends substantially continuously along the width of the diffuser between the first and second ends, optionally interrupted by other structures such as flow control structures and inlet openings in the rear wall. The base surface may be flat (substantially planar) or slightly curved along the width dimension or along the length dimension.

[0041] As an alternative to, or in addition to, flow control structures on the inner surface of the rear wall, the diffuser may include flow control structures that are part of the inner surface of the front wall. The front wall may also include a "base surface" that covers most of the inner surface of the front wall and may include one or more flow control structures that extend from the front wall base surface toward the channels a distance above the base surface. The base surface of the front wall extends substantially continuously along the width of the diffuser between the first and second ends, interrupted by optional flow control structures and other structures, such as one or more outlet openings in the front wall. The base surface may be flat (substantially planar) or slightly curved along the width or length dimension.

[0042] The flow control structure may be any structure that extends into the channel in a direction from the base surface of the front or rear wall toward the channel and is effective to contact, impede, or divert the flow of gas directed through the channel along the base surface. The flow control structure may be any shape or form of structure that directs the flow of gas along the base surface. Examples of flow control structures include baffles, diverters, walls, cowls, or the like. The flow control structure affects the flow of gas at the base surface, which affects the flow of gas within the channel, which may affect the level (volume, velocity, or both) of flow through different portions of the channel and diffuser outlet to provide a desired flow profile of gas through the diffuser outlet.

[0043] The flow control structure can generate a desired flow profile of gas through the diffuser outlet. The desired effect of the flow control structure can be to generate a flow profile through the diffuser outlet that is uniform along the length of the outlet. Alternatively, the desired effect of the flow control structure can be to generate a flow profile through the diffuser outlet that is non-uniform along the length or width of the outlet, such as greater flow at one end of the diffuser outlet and less at a second end of the diffuser outlet, or greater flow at one portion of the diffuser width (e.g., a forward portion) and less at a different portion of the width (e.g., a rearward portion), etc.

[0044] The flow control structure can be of any form, shape, height, or length, and can be fixed or movable (relative to the base surface, the channel, or both) based on a spring (biased by a spring), or mechanically and remotely movable by a remote control device.

[0045] As an example, a type of flow control structure is a fixed, vertical (relative to the base surface held horizontally) "wall" structure extending from a base surface into a channel. Wall-type flow control surfaces can have a straight or curved configuration along the length of the wall and base surface, a height in the direction of the channel, and a width dimension along the base surface that is perpendicular to the length. Exemplary wall structures can have a substantially rectangular cross-section when viewed along the length of the structure. The width may be a minimum, e.g., less than 5, 3, or 2 millimeters.

[0046] The height of the wall-type flow control structure can be made as desired to divert gas flow along the base surface. The height of the flow control structure (wall-type or other style) can be sufficient to extend from the base surface to the inner surface of the front wall to minimize the space between the flow control surface and the front wall and maximize the flow diversion effect of the flow control surface. The channel can be considered to have a depth that is the distance from the rear wall base surface to the inner surface or base of the front wall. The height of the flow control structure can be at least 75%, 80%, or 90% of the channel depth.

[0047] Referring to FIG. 1A, an example of the described diffuser is shown. Diffuser 100 includes a front plate 102 and a rear plate 104. The front and rear plates may be assembled by positioning the front plate in contact with the rear plate to form a diffuser housing that defines a channel between the front and rear plates. Front plate 102, rear plate 104, and the housing formed from the assembled plates each include a first end (e.g., top end) 110, a second end 112, a front wall 114, a rear wall 116, and side walls 118. The housing defines a length (“l”) between first end 110 and second end 112 and a width (“w”) between side walls 118. When the front plate 102 and rear plate 104 are assembled and in contact with each other at the side walls and edges, the opposing plates form a channel 120 within them defined by the inner surfaces of the front plate, rear plate, side walls, and edges.

[0048] Diffuser 100 includes an inlet (referred to as the "diffuser inlet" or "channel inlet") 130 that allows gas to enter channel 120 from a location external to the diffuser body, and an outlet (referred to as the "diffuser outlet" or "channel outlet") that includes multiple outlet openings 132, as shown, each of which allows gas to pass from channel 120 to the exterior of diffuser 100 (see arrows), e.g., into a wafer container housing diffuser 100. The illustrated inlet 130 is located approximately midway between ends 112 and 110. The outlet openings 132 are positioned at regular intervals along the length of diffuser 100 between first end 110 and second end 112.

[0049] The rear wall 116 includes a base surface 142, which is a substantially flat plane between the side wall 118 and the end of the rear wall 116. The base surface 142 is interrupted by the inlet 130 and further by the flow control structure 140. The flow control structure 140 is in the form of a curved, circular wall or ring that extends from the base surface 142 to a height within the channel 120. Gas entering the inlet 130 enters the channel 120 and flows from the inlet 130 toward the ends 110 and 112. As the gas flows within the channel 120 toward the ends 110 and 112, the direction of the gas is diverted by the flow control structure 140. The gas exits the channel 120 through an outlet opening and enters the interior of the wafer container. Optionally, although not shown, the interior surface of the front wall 114 can also include a flow control surface extending into the channel 120 to control or divert the flow of fluid through the channel 120.

[0050] 1B, another example of the described diffuser is shown. Diffuser 200 includes a front plate 202 and a rear plate 204. The front and rear plates may be assembled by positioning the front plate in contact with the rear plate to form a diffuser housing that defines a channel 220 between the front and rear plates. Front plate 202, rear plate 204, and the housing formed from the assembled plates each include a first end (e.g., top end) 210, a second end 212, a front wall 214, a rear wall 216, and side walls 218. The housing defines a length between first end 210 and second end 212 and a width between side walls 218. When the front plate 202 and rear plate 204 are assembled and in contact with each other at the side walls and edges, the opposing plates form a channel 220 within them defined by the inner surfaces of the front plate, rear plate, side walls, and edges.

[0051] Diffuser 200 includes an inlet 230 that allows gas to enter the channel from a location external to the diffuser body, and a diffuser outlet 232. As shown, outlet 232 forms a longitudinal opening or slot that extends between ends 210 and 212, allowing gas to pass from channel 220 to the exterior of diffuser 200 (see arrows).

[0052] Rear wall 216 includes a base surface 242 that is a substantially flat plane between the sidewalls and the end of rear wall 216. Base surface 242 is interrupted by inlet 230 and by flow control structure 240. Flow control structure 240 is an annular ring that surrounds inlet 230. Gas entering inlet 230 enters channel 220 and flows from inlet 230 toward ends 210 and 212. As gas flows within channel 220 toward ends 210 and 212, the gas can pass through outlet 232 along its length.

[0053] 1C , another example of the described diffuser is shown. Diffuser 300 includes a front plate 302 and a rear plate 304, which can be assembled by positioning the front plate in contact with the rear plate to form a diffuser housing that defines a channel 320 between the front and rear plates. Front plate 302, rear plate 304, and the housing formed from the assembled plates each include a first end (e.g., top end) 310, a second end 312, a front wall 314, a rear wall 316, and side walls 318. The housing defines a length between first end 310 and second end 312 and a width between side walls 318. When the front plate 302 and rear plate 304 are assembled and in contact with each other at the side walls and ends, the opposing plates form a channel 320 within them defined by the inner surfaces of the front plate, rear plate, side walls, and ends.

[0054] Diffuser 300 includes an inlet 330 that allows gas to enter channel 320 from a location external to diffuser 300. Diffuser 300 includes a diffuser outlet 332 as part of faceplate 302. As shown, outlet 332 comprises a series of circular openings that extend along a length portion of diffuser 302 between ends 310 and 312. The openings allow gas to pass from channel 320 to the exterior of diffuser 300 (see arrows).

[0055] Rear wall 316 includes a base surface 342, which is a substantially flat plane between the side wall and the end of rear wall 316. Base surface 342 is interrupted by inlet 330 and by flow control structure 340 adjacent to inlet 330. Flow control structure 340 includes an annular ring surrounding inlet 330 and a semicircular cowl disposed on one side of inlet 330 between inlet 330 and side wall 318. Gas entering channel 320 through inlet 330 flows from the inlet 330 toward ends 310 and 312. As gas flows within channel 320 toward ends 210 and 212, the gas can pass through individual openings that make up outlet 332 along its length. The openings in outlet 332 are positioned in two regions along the length of front plate 314: Region I between end 310 and a midpoint of front plate 314 along its length, and Region II between end 312 and a midpoint of front plate 314. The front plate 314 does not include an opening in region III in the middle portion of the front plate 314 , which is included in the portion of the plate 314 opposite the inlet 330 .

[0056] 1D shows a top view of rear plate 304 and a side perspective cutaway view of assembled diffuser 300 created by engaging rear plate 304 and front plate 302 at sidewalls 318 to form an interior containing channels 320. Gas enters diffuser inlet 330, enters channels 320, and flows along channels 320 toward ends 310 and 312 through individual openings in diffuser outlet 332.

[0057] 1E and 1F show another example of a diffuser including a channel with flow control structures for directing fluid flow from an inlet to an outlet and through the channel through the inlet and outlet chambers. Referring to FIG. 1E, a diffuser 350 can include a front plate and a rear plate (not specifically shown in FIG. 1E) that can be assembled to form a diffuser housing that defines a channel 370 including an inlet chamber 370a and an outlet chamber (or "plenum chamber") 370b. The diffuser 350 includes a housing formed from the assembled plates, a first end (e.g., top end) 360, a second end 362, a front wall, a rear wall, and side walls. The housing defines a length between the first end 360 and the second end 362 and a width between the side walls.

[0058] Diffuser 350 includes an inlet 380 at end 362 that connects to inlet chamber 370a of channel 370, allowing gas to enter channel 370 at inlet chamber 370a from a location external to diffuser 350. Also connected to channel 370, and specifically to outlet chamber 370b, is a diffuser outlet 382. As shown, outlet 382 comprises a series of circular openings that extend along the length of diffuser 350 between ends 360 and 362. Outlet 382 allows gas to pass from outlet chamber 370b of channel 370 to the exterior of diffuser 350 (see arrows).

[0059] More specifically, diffuser 350 includes a flow control structure that directs the flow of gas from inlet 380 into and through inlet chamber 370a of channel 370 that extends longitudinally from inlet 380 to an intermediate portion (based on length) 384 of diffuser 350. Inlet chamber 370a is defined in part by wall (e.g., sidewall) 368 and by flow control structure 364a, i.e., wall 364a.

[0060] Wall 364a extends lengthwise within channel 370 from end 362 to intermediate portion 384. A second wall section 364b extends lengthwise within channel 370 from end 360 to intermediate portion 384. Although both wall sections 364a and 364b extend to intermediate portion 384, the two wall sections do not connect, instead forming a flow gap 390 as part of channel 370 connecting inner chamber 370a to outer chamber 370b.

[0061] In use, gas flows through inlet 380 and enters inlet chamber 370a at end 362 of diffuser 350. The gas flows through inlet chamber 370a to middle portion 384 of diffuser 350. From inlet chamber 370a, gas flows through gap 390 into outer chamber 370b and finally flows through outlet 382.

[0062] 2A-2D, these figures show an example of a diffuser 400 that includes a bottom plate 404 and a front plate (also called a top plate, not shown). The top window of each figure shows a top view of the bottom plate 404. The bottom window of each figure shows a side view of the diffuser 400 and a top view of the diffuser 400 of the flow profile of gas flowing through the diffuser outlet of the top plate of the diffuser 400, based on detected humidity levels in the flow measured by computational fluid dynamics ("CFD") techniques.

[0063] Each diffuser 400 includes the structure found in the diffusers described above, including ends 410 and 412, a front plate and a rear plate that form the assembled diffuser housing, a diffuser inlet, and a diffuser outlet. The housing defines a length between the first end 410 and the second end 412, a width between the sidewalls, and a channel within the assembled housing. The rear plate has a base surface 424, an inlet 430 in a central region (approximately midway between the ends and midway between the sidewalls), and a flow control structure 440 in the central region.

[0064] 2A shows a diffuser bottom plate 404 including a base surface 424 having inlets 430. The bottom plate 404 is assembled with a top plate (not shown) having slot-type openings extending uniformly and continuously along portions I, II, and III of the top plate, similar to, for example, the top plate 218 shown in FIG. 1B. The base surface 424 does not include flow control structures and is considered a "control" example for comparison to other base surfaces that include flow control structures according to this specification.

[0065] As gas flows through the diffuser 400 of Figure 2A (through the inlet 430, through the internal channels of the diffuser 400, and then through the diffuser outlet), the gas flows through the slotted diffuser outlet in the profile shown by the bottom window in Figure 2A. The gas enters the channel by passing through the inlet 430 in the central portion of the base surface 424, builds backpressure in the internal channel between the top and bottom plates, and then exits through the slotted outlet that extends uniformly along the front wall at portions I, II, and III.

[0066] The flow profile in Figure 2A (bottom) shows non-uniform flow of gas from the diffuser outlet based on position along the length of the diffuser. Low or no gas flow occurs from the middle third of the length of the diffuser 400 (section III). Higher levels of flow occur at end sections I and II (e.g., approximately one-third of the diffuser's length at each end), with substantially all of the flow from the diffuser 400 occurring at end sections I and II along the entire length of the diffuser, and very little flow from the middle section III of the length.

[0067] 2B shows a different example of a diffuser bottom plate 404 including a base surface 424 having an inlet 430 and a flow control structure 440. The top plate (not shown), which is assembled with the bottom plate 404 to form the assembled diffuser device, has an outlet in the form of a narrow slot extending along the length of the top plate between two ends, as shown, for example, in top plate 218 in FIG. 1B. The flow control structure 440 is a semicircular, fixed wall that partially surrounds the inlet 430 and extends from the base surface 424 into the channel 420 toward the front wall, optionally touching or nearly touching the front wall. The flow control surface 440 diverts the flow of gas from the inlet 430 toward one side of the channel 420 and inhibits or prevents direct gas flow from the inlet 430 to the other side of the channel 420.

[0068] The flow profile of gas flowing through the diffuser 400 of Figure 2B is shown in the bottom window of Figure 2B. As gas flows through the diffuser 400 (through the inlet 430, through the channels 420 of the diffuser 400, and then through the diffuser outlet), it is diverted by the flow control structure 440 and evenly directed to the end portions of the diffuser 400. The flow profile shows the flow of gas from the slotted diffuser outlet (not shown) based on position along the length of the diffuser. The middle portion III and end portions I and II of the diffuser length each have slightly different gas flow through the diffuser outlet. While the flow varies somewhat along the length, as indicated by the length of the arrows, the flow can be considered substantially uniform along the length of the diffuser device.

[0069] 2C shows another example of a diffuser bottom plate 404 that includes a base surface 424 with an inlet 430 and a flow control structure 440. A top plate (not shown), which is assembled with the bottom plate 404 to form the assembled diffuser device, has an outlet in the form of a narrow slot extending along the length of the top plate between two ends, as shown, for example, in top plate 218 in FIG. 1B.

[0070] Flow control structure 440 includes a fixed semicircular wall portion 440a that partially surrounds inlet 430 and a straight portion 440b that is connected to semicircular wall portion 440 and extends to and connects to a side wall of diffuser 400. Wall portion 440 extends toward the front wall, optionally contacting or nearly contacting the front wall. Flow control structure 440 diverts the flow of gas from inlet 430 toward one side of channel 420 and toward one end of channel 420, and inhibits direct flow of gas from inlet 430 to the other side of channel 420 or the opposite end of channel 420.

[0071] Flow control structure 440 is attached to the sidewall of 404 and directs the flow of gas within the channel toward the two ends at different amounts, creating a significantly non-uniform outlet flow profile between the two ends and the intermediate portion of the outlet. A non-uniform outlet flow profile can be useful, for example, to direct specific types of gas to specific locations within the substrate container toward different locations of substrates (wafers) housed within the substrate holder, depending on whether the gas is denser or less dense than the atmosphere being replaced (e.g., a purge gas may be lighter or heavier than the air atmosphere within the substrate container). Mechanism 440 may be movable or adjustable to redirect gas in real time.

[0072] The flow profile of gas flowing through the diffuser 400 of Figure 2C is shown in the bottom window of Figure 2C. As gas flows through the diffuser 400 (through the inlet 430, through the internal channels of the diffuser 400, and then through the diffuser outlet), the gas is diverted by the flow control structure 440 and directed toward one end portion (II) of the diffuser 400, preventing it from flowing directly to the opposite end portion (I). The flow profile shows the uneven flow of gas from the diffuser outlet based on position along the length of the diffuser. The maximum amount of gas flows through length portion II toward one end of the diffuser 400 (end 410). A lower flow rate occurs at length portion I at the opposite end of the diffuser 400. The lowest flow rate occurs at the middle portion III near end II.

[0073] FIG. 2D shows a diffuser 400 with a structure comparable to that of the diffuser 400 of FIG. 2C. The difference between the diffuser 400 of FIG. 2C and the diffuser 400 of FIG. 2D is the width of the slots forming the outlets in the top plate (not shown). The width of the outlet slots can affect the velocity of the purge gas through the outlets. Narrower outlet slots tend to act like nozzles, diffusing the gas at higher velocities than wider outlet slots. The different slot opening widths at the diffuser outlets of the diffusers of FIG. 2C and FIG. 2D result in different pressures on the gas as it flows through the respective diffuser channels, creating different flow profiles, as shown in the bottom windows of each of FIG. 2C and FIG. 2D.

[0074] 3A and 3B, an exemplary wafer container 30 adapted to hold and transport one or more substrates 32 is shown. The substrate container 30 includes two opposing side portions 34, a top portion 36, a bottom portion 38, and a back portion (rear wall) 42. The front portion 44 includes a door frame 46 defining an opening 48. A door 52 is configured to sealably cover the opening 48. The opening 48 lies in a plane substantially parallel to a vertical direction 54. The substrates 32 may be any of a variety of different generally flat structures that are typically transported within a container such as the container 30 for safe and clean handling to avoid damage or contamination. Exemplary structures include semiconductor wafer structures, precursors thereof, derivatives thereof, and in-process versions of any of these, including semiconductor wafers, in-process microelectronic devices, EUV (extreme ultraviolet) reticle pods, panels, or other structures known to be carried or housed within the carriers described herein, any of which may be generally referred to as a "wafer" or "substrate."

[0075] A pair of slotted sidewalls 66, each adjacent a respective one of the side portions 34, are disposed within the substrate container 30. The slotted sidewalls 66 are aligned with the slots facing each other to define a plurality of slot locations 68, and are spaced apart to allow a plurality of substrates 32 to be supported therebetween.

[0076] The substrate vessel 30 further includes at least one diffuser assembly 70 disposed within the substrate vessel 30 and operably coupled to a gas source (not shown) for distributing gas within the substrate vessel 30 .

[0077] 3B, an exemplary wafer container 30 is shown adapted to accommodate wafers 32 having a diameter of 300 millimeters and includes two diffuser assemblies 70a and 70b. Diffuser 70a is located in the front third of the container 30 near the opening 48. Diffuser 70b is located in the rear third of the container 30 near the back portion 42.

[0078] The diffuser, as described, can be used in a wafer container to hold and transport one or more semiconductor wafers or any other substrates inside the container. The container interior (sometimes called the "microenvironment") can be evacuated or filled with a desired gaseous atmosphere, for example, an inert gas such as nitrogen, clean dry air, or another desired gas.

[0079] During use, one or more wafers are positioned inside the container. The wafers and container are typically located in a clean room with a controlled atmosphere and very low particle levels and environmental contaminants. A wafer container door is positioned over the opening of the wafer container, and a sealed closure between the door and the container opening prevents gas flow between the inside and outside of the container. The container can be moved, for example, between locations within a clean room or from one clean room to another. In an exemplary container, the container includes a diffuser as described herein located in the front portion of the container, for example, in the front half or front third of the interior (measured from the opening frame toward the back wall).

[0080] After the door is closed, the gaseous environment within the enclosed interior may remain the same, i.e., the environment of the clean room where the wafers were loaded into the container and the container was closed. Alternatively, the internal gas atmosphere may be removed from the interior (i.e., replaced with a different gas), and the container interior may be held at a reduced pressure at a partial vacuum. Optionally, the interior may be filled with a gas different from the original internal gas by dispensing a gas (e.g., a "purge gas") into the interior from a diffuser herein. The purge gas may be an inert gas (e.g., at least 99 percent enriched nitrogen or helium) or clean, dry air (air with a relative humidity of less than 5 percent or less than 1 percent).

[0081] After the container is moved to its destination, the substrates (e.g., semiconductor wafers) within the container can be removed from the container by first removing the door from the container. During or before the step of removing the door from the container, a purge gas may be distributed into the container interior via a diffuser as described above. The gas may be distributed while the door is being removed and for a period of time after the door is removed from the container opening. In an open-door purge method, the door is opened and purge gas is flowed into the substrate container interior to exchange the internal atmosphere.

[0082] In the closed door purge method, the door is held in place as purge gas is flowed into the substrate container, and the container outlet is opened to allow the gaseous internal atmosphere to be purged from the inside of the container and replaced with the purge gas. The door is opened after the purge gas has been added to the inside of the container to substantially purge the previous atmosphere.

Claims

1. A front-opening wafer container comprising: a container interior bounded by a bottom wall, a top wall, a side wall, and a front opening; a door for sealingly closing the front opening; a diffuser in the interior adapted to distribute gas into the interior, the diffuser comprising: an elongate body having a top end, a bottom end, a front wall, a rear wall, side walls, a height between the top end and the bottom end, a width between the side walls, and a channel; a diffuser inlet to allow gas flow into the channel; a diffuser outlet comprising one or more openings in the front wall, one side wall, or both the front wall and the one side wall; a flow control structure within the channel that directs the flow of gas along the length of the channel between the diffuser inlet and the diffuser outlet. Front-opening wafer container.

2. 10. The container of claim 1, wherein the container interior comprises a front portion adjacent the front opening and a rear portion adjacent a rear sidewall, the diffuser being vertically oriented and disposed within the front portion.

3. 3. The vessel of claim 1, wherein the front wall of the diffuser includes a width including a forward portion and an aft portion, and the diffuser outlet is located in the forward portion.

4. 4. The vessel of claim 3, wherein the diffuser front wall extends along the height and comprises an upper portion, a lower portion, and an intermediate portion, and the diffuser outlet is located in the upper portion and the lower portion but not in the intermediate portion.

5. 5. The vessel of claim 1, wherein the diffuser comprises a rear wall having a base surface and a flow control device extending from the base surface into the channel.

6. The container of claim 5 , wherein the flow control device comprises a wall extending from the base surface toward an inner surface of the front wall.

8. 7. The vessel of claim 1, wherein the diffuser outlet includes a directional opening that directs the flow of gas through the opening in a direction non-perpendicular to the surface of the front wall.

9. 9. A method of using a container according to any one of claims 1 to 8, said method comprising: Positioning one or more wafers in a container; closing the door to seal the front opening; Distributing gas into the interior through the diffuser. A method comprising:

10. the container interior having a front portion adjacent the front opening and a rear portion adjacent a rear sidewall, the diffuser being disposed within the front portion of the container, and the method comprising: distributing the gas through the diffuser while the door is open; Distributing the gas toward the front opening to cause a flow of the gas through the front opening and reduce a flow of external gas from outside the container to inside the container; 10. The method of claim 9, comprising:

11. an elongate body having a top end, a bottom end, a front wall, a rear wall, side walls, a height between the top end and the bottom end, a width between the side walls, and a channel; a diffuser inlet to allow gas flow into the channel; a diffuser outlet comprising one or more openings in the front wall, the side wall, or both the front wall and the side wall; a non-porous channel surface comprising a non-porous rear wall surface and a non-porous side wall surface; a flow control structure within the channel that directs the flow of gas along the length of the channel between the diffuser inlet and the diffuser outlet; A diffuser comprising:

12. the front wall has a width including a forward portion and an aft portion, and the diffuser outlet is located in the forward portion and not in the aft portion. The diffuser of claim 11.

13. 13. The diffuser of claim 11 or 12, wherein the front wall of the diffuser extends along the height and comprises an upper portion, a lower portion, and an intermediate portion, and the diffuser outlets are located in the upper portion and the lower portion but not in the intermediate portion.

14. 14. The diffuser of any one of claims 11 to 13, wherein the diffuser comprises a rear wall having a base surface, and a flow control device extending from the base surface into the channel.

15. 15. A diffuser according to any one of claims 11 to 14, wherein the diffuser outlet includes a directional opening that directs the flow of gas through the opening in a direction non-perpendicular to the surface of the front wall.

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