Substrate container system and method for purging a substrate container - Patents.com

Abstract

A substrate container useful for holding or transporting substrates such as semiconductor wafers and microelectronic devices in a clean environment, and methods of using the substrate container, are described.

Description

[Technical Field]

[0001] The present disclosure relates to substrate containers (sometimes called "substrate carriers" or "wafer containers") useful for holding or transporting "substrates" (e.g., semiconductor wafers, etc.) in a clean environment, and methods of using the substrate containers. [Background technology]

[0002] Microelectronic devices are prepared on semiconductor substrates by a series of precise processing steps, each performed under extremely clean conditions, and between processing steps, the "substrate" on which the microelectronic devices are formed may be moved from one processing location to a different processing location.

[0003] To move substrates between processing steps or separate processing locations, the substrates are held in specialized containers designed to prevent damage to the substrates while simultaneously shielding them from contamination. Exemplary substrate 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 housing multiple semiconductor wafers or other substrates 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] The substrate container may be in the form of a multi-sided container body (e.g., a "shell") that defines the container interior. The container body includes an opening on one side that allows multiple substrates to be inserted into or removed from the interior. The container also includes a removable door adapted to cover the opening and enclose the interior with an airtight seal. One or more gas ports (inlets or outlets) pass through the body of the container, allowing gas to be introduced into the interior to control the atmosphere within the container.

[0005] As microelectronic devices become smaller and the number of microelectronic features per area of ​​semiconductor device increases, the devices become more sensitive to particles and environmental contaminants. In smaller microelectronic devices, even smaller contaminants, even molecular-scale contaminants, can disrupt the performance of the microelectronic device. As a result, ever-improving control of particle contamination is needed during all stages of semiconductor substrate processing, including during transfer of substrates between process steps.

[0006] There is currently a need for ever-improving systems and methods for controlling the gaseous environment within a substrate container to maintain a high level of cleanliness and avoid contamination of substrates during handling. Summary of the Invention

[0007] During use of a substrate container, the gaseous atmosphere inside the container may be replaced with a new gaseous atmosphere for various reasons. To enable this, the container may include a gas port (i.e., an opening or "inlet") through which gas can be delivered to or removed from the container interior.

[0008] As an example, a high-purity, clean, dry gas (referred to as a "purge gas") can be dispensed into the vessel interior to replace (i.e., displace) the previous atmosphere. When substrates are inserted into the vessel interior, the substrates may contain moisture on their surfaces, which can enter the vessel atmosphere. At a desired time before removing the substrates from the vessel interior, either before or after the vessel door is removed, the vessel atmosphere may be replaced with a new gaseous atmosphere that does not contain moisture, i.e., the vessel interior may be "purged" with a dry atmosphere. Some purge methods use nitrogen as a dry purge gas to replace the vessel atmosphere. Other purge methods use clean, dry air as a purge gas.

[0009] The choice of whether to use nitrogen or clean, dry air as a purge gas may depend on the type of substrate being processed, the type of processing performed on the substrate, and user preference. The purpose of the purge step may be to remove water vapor from the vessel. Either nitrogen or clean, dry air is effective at removing moisture. However, some processes are sensitive to the presence of oxygen. In these processes, nitrogen gas has the advantage of reducing the oxygen level in the vessel, as opposed to clean, dry air, which contains oxygen. Nevertheless, clean, dry air is the purge gas of choice for manufacturing processes that are less sensitive to the presence of oxygen and where the cost of nitrogen gas is relatively high or prohibitive. To the applicant's knowledge, commercial processes use one or the other of nitrogen or clean, dry air, but not a purge gas that is a mixture or combination of clean, dry air and nitrogen.

[0010] In addition to being effective in removing moisture, a preferred commercial purge step should be performed with efficient throughput. The length of time required to perform the purge step can be important in this regard. A longer purge step reduces the throughput and overall efficiency of the manufacturing process, while a shorter purge step advantageously increases throughput and overall efficiency.

[0011] As determined by the applicant, commercial processes using either nitrogen gas (pure nitrogen) or clean dry air alone, without considering the density of the selected purge gas, produce uneven purging of the substrate container between the upper and lower container locations, which causes extended times to complete the purge step.

[0012] More specifically, the container atmosphere contains moisture due to moisture present on the substrate surface when the substrate is placed inside the container, or due to the amount of moisture in the container atmosphere when the atmosphere is sealed inside the container, or both. Because dry air as a purge gas is denser than the moist air of the container atmosphere, the dry air as a purge gas tends to flow quickly through the lower portion of the substrate container interior, while requiring a significantly longer period of time to ultimately replace the less dense moist atmosphere at the upper container location. Conversely, nitrogen as a purge gas is lighter than moist air and quickly replaces the atmosphere at the upper container location, but requires a significantly longer period of time to replace the atmosphere in the lower portion of the container.

[0013] As determined by the present applicant, the uniformity of purge gas flow through the upper and lower portions of the substrate container interior can be improved by controlling the density of the purge gas by using a purge gas having a density approximately the same as that of the container atmosphere. A purge gas having a density approximating the density of the moist air inside the container displaces the moist air at the upper and lower container locations significantly more uniformly. The more uniform flow of purge gas through the container reduces the time required for the purge step compared to the time required when using a purge gas having a density significantly different from that of the container atmosphere.

[0014] As described herein, the density of the purge gas can be selected and controlled to match the density of the atmosphere present inside the substrate container to improve the uniformity of the purge gas flow through the container interior and reduce the time required to complete the purge step. The density of the purge gas may be controlled by selecting a purge gas composition that has a density that approximates the density of the moist air contained inside the container. The purge gas may be a mixture of two different types of purge gas, such as clean dry air or a mixture of oxygen and nitrogen (pure nitrogen), where the mixture can have a density approximately equal to the density of the moist air in the container atmosphere. Alternatively or additionally, the purge gas may be a single type of purge gas (e.g., pure nitrogen gas or clean dry air) or a combination of different purge gas components (e.g., nitrogen and oxygen) at a temperature at which the purge gas has a density approximately equal to the density of the moist air in the container atmosphere.

[0015] In one aspect, the present invention relates to a method for purging a substrate container with a purge gas, the substrate container comprising: a container body including an opening; a door adapted to cover the opening; an interior defined by the container body; a substrate supported within the interior; a container atmosphere within the interior; and one or more purge gas inlets within the interior. The method includes distributing a purge gas into the interior through the one or more inlets, the purge gas comprising clean, dry air received from a source of clean, dry air and nitrogen gas received from a source of nitrogen gas.

[0016] In another aspect, the invention relates to a method for purging a substrate container with a purge gas, the substrate container including a container body including an opening, a door adapted to cover the opening, an interior defined by the container body, a substrate supported within the interior, a container atmosphere within the interior, a purge gas inlet within the interior, and a source of purge gas, the method including measuring a relative humidity of the container atmosphere, controlling a density of the purge gas based on the relative humidity of the container atmosphere, and distributing the purge gas into the interior through the inlet.

[0017] In yet another aspect, the present invention relates to a substrate container system including a container body having an opening, a door adapted to be placed over and removed from the opening, an interior defined by the container body, a substrate supported within the interior, a container atmosphere within the interior, a purge gas inlet within the interior, and a source of purge gas including a source of clean, dry air and a source of nitrogen gas. The system also includes a purge gas flow control system that combines a flow of clean, dry air and a flow of nitrogen gas to produce a purge gas mixture.

[0018] According to yet another aspect, the present invention relates to a substrate container system comprising a container body including an opening, a door adapted to be positioned over and removed from the opening, an interior defined by the container body, a purge gas inlet connected to the interior, a relative humidity sensor, a source of purge gas, and a control system for controlling the density of purge gas dispensed into the interior through the purge gas inlet.

[0019] According to yet another aspect, the present invention relates to a method comprising dispensing a purge gas mixture through an inlet of a substrate container, the purge gas mixture comprising a combination of clean, dry air and nitrogen gas. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view of an exemplary wafer container as described. [Figure 2] FIG. 1 is a side cutaway view of an exemplary wafer container. [Figure 3A] 1 is a side cutaway view of a wafer container and a conventional method of purging the wafer container. [Figure 3B] 1 is a side cutaway view of a wafer container and a conventional method of purging the wafer container. [Figure 3C] 1 is a side cutaway view of a wafer container and a conventional method of purging the wafer container. [Figure 4A] FIG. 2 is a side cutaway view of an exemplary wafer container herein. [Figure 4B]FIG. 2 is a side cutaway view of an exemplary wafer container herein. [Figure 4C] FIG. 2 is a side cutaway view of an exemplary wafer container herein. [Figure 5A] 1 is a side cutaway view of an exemplary wafer container and method of purging the wafer container described herein. [Figure 5B] 1 is a side cutaway view of an exemplary wafer container and method of purging the wafer container described herein. [Figure 6A] 1 is a side cutaway view of a wafer container and a conventional method of purging the wafer container. [Figure 6B] 1 is a side cutaway view of a wafer container and a conventional method of purging the wafer container. [Figure 6C] 1 is a side cutaway view of a wafer container and a conventional method of purging the wafer container. [Figure 7A] 1 is a side cutaway view of an exemplary wafer container and method of purging the wafer container described. [Figure 7B] 1 is a side cutaway view of an exemplary wafer container and method of purging the wafer container described. DETAILED DESCRIPTION OF THE INVENTION

[0021] All figures are schematic and not to scale.

[0022] The following describes a substrate container that includes a container body having an interior, an opening on one side of the body for accessing the interior, and a door adapted to cover and seal the opening. The container also includes one or more gas ports that include an inlet useful for distributing a gas (e.g., a "purge gas") into the interior of the container.

[0023] The container can be used as a component of a system (e.g., a "substrate container system") that includes other devices, structures, or sources of raw materials used in conjunction with the substrate container to handle substrates in a clean environment. Exemplary components of a substrate container system include any one or more of the following: a source of purge gas; optionally, separate sources of two or more different types of purge gas; sensors, such as temperature, pressure, or humidity sensors, that measure conditions in the container, the system, or the process materials (purge gas); controllers, such as a temperature controller that controls the temperature and thereby the density of the purge gas delivered inside the container, or a flow controller that controls the flow of a single purge gas, two different purge gases, or a mixture of two or more different purge gases (a "purge gas mixture"); a process control system that controls the conditions and process steps of the purge process, etc.

[0024] Also described are methods for introducing a purge gas into the interior of a vessel while controlling the purge gas composition, purge gas temperature, purge gas density, or a combination thereof. According to exemplary methods and systems, the purge gas composition, temperature, or density can be selected so that the purge gas displaces ("purges") the atmosphere within the vessel with a high degree of efficiency. In exemplary methods, to achieve efficiency in the purging step, the purge gas may be controlled to have a density that approximates the density of the atmosphere within the vessel being displaced by the purge gas. A purge gas having a density similar to or the same as that of the vessel atmosphere displaces the vessel atmosphere in a substantially uniform manner throughout the vessel interior, while a purge gas having a density significantly different from that of the vessel atmosphere displaces the vessel atmosphere less efficiently, e.g., less uniformly and less rapidly.

[0025] In an exemplary method, the purge gas may contain a mixture of two or more different types of purge gas supplied from two or more separate gas sources. As an example, the system may deliver two different types of purge gas to the interior of the container, the two types including clean, dry air as one type of purge gas and nitrogen gas as a second type of purge gas, with the clean, dry air being supplied from a clean, dry air source and the nitrogen gas being supplied from a pure nitrogen gas source. As another example, instead of clean, dry air and nitrogen as two different types of purge gas, the system may include a source of oxygen gas as one type of purge gas and a source of nitrogen gas as a second type of purge gas. The nitrogen gas from the nitrogen gas source and the oxygen gas from the oxygen gas source can each be delivered to the container, optionally as a mixture.

[0026] As used herein, the term "nitrogen gas" refers to pure nitrogen gas and means nitrogen gas containing at least 99.9 or 99.99 mole percent nitrogen and less than 0.01 or 0.001 mole percent moisture. The term "clean, dry air" refers to a gaseous composition considered to be clean, dry air sufficiently pure and moisture-free for use in commercial processes for processing semiconductor or microelectronic substrates, and includes gas containing approximately 78 mole percent nitrogen (N), approximately 21 mole percent oxygen (O), and less than 0.01 or 0.001 mole percent moisture. An example of a clean, dry air product is Ultra-High Purity, Extra Clean, Dry Air (XCDA®) available from Entegris Inc., Billerica, MA. The term "oxygen gas" refers to pure oxygen gas and means oxygen gas containing at least 99.9 or 99.99 mole percent oxygen and less than 0.01 or 0.001 mole percent moisture.

[0027] In these or other examples, the system may handle and process (e.g., heat or cool) the purge gas to achieve the desired density as it is delivered to the vessel interior. A useful purge gas density may be one that approximates the density of the vessel atmosphere being displaced by the purge gas; for example, the purge gas may have a density within 10 percent, or within 5 percent, or within 2 or 1 percent of the density of the vessel atmosphere. The purge gas may be a single type of purge gas, such as pure nitrogen (“nitrogen gas”) or clean, dry air, or may be a purge gas mixture prepared from two different types of purge gases, for example, by combining a stream of nitrogen gas from a nitrogen gas source and a stream of clean, dry air from a clean, dry air source.

[0028] A 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 ("container opening" or "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 covering the opening between the container interior and the container exterior. Substrate containers typically include at least one inlet port adapted to allow a gas, e.g., a "purge gas," to be delivered into the container interior and at least one (optional) outlet port that allows gas from the container interior to flow out of the interior toward the exterior. Optionally, a delivery device, sometimes referred to as a "diffuser," may be connected to the inlet port. A diffuser may be used to distribute the purge gas throughout the container interior, for example, by distributing the purge gas along the length of the diffuser, where the diffuser is positioned vertically along the height of the container interior.

[0029] The substrate container is adapted to accommodate multiple substrates. A "substrate" may be any of a variety of different generally flat structures known to be of the type typically housed or transported in substrate container apparatus to allow for safe and clean handling and transport of the substrates without causing damage or contamination to the substrates. Exemplary substrates include semiconductor wafers, precursors thereof, derivatives thereof, and in-process versions of any of these, such as in-process semiconductor wafers, in-process microelectronic devices, EUV (extreme ultraviolet) reticles, panels, or other structures known to be carried or housed in carriers described herein, any of which may be generally referred to as a "wafer" or "substrate."

[0030] 1 shows a substrate container that can be used as a component of the described substrate container system. Substrate container 1 includes a container body (e.g., "shell") 2, a front opening 4, an interior 8, a port 10 in the form of an opening through the bottom wall of shell 2, and slots 12 in opposing side walls. Slots 12 are adapted to engage and support the edges of multiple substrates (not shown) when the substrates are held within interior 8. Substrate container 1 also includes a door 6 that can be used to cover opening 4 and close and seal interior 8.

[0031] Substrate container 1 can be used to transport, contain, or store semiconductor wafers (substrates) that are being processed through a series of processing steps (i.e., "in-process" wafers) between the steps. As shown, substrate container 1 is a front-opening container, such as a "front-opening integrated pod," or "FOUP."

[0032] The container body 2 defines an interior 8 within the container 1, and an opening 4 is provided on one side of the container body 2 to allow access to the interior 8. The opening 4 allows multiple wafers to be placed inside the interior 8 of the container body 2 while being supported by slots 12. A door 6 can be used to cover the opening 4. When the opening 4 is covered by the door 6, a seal is formed between the door and the container by a gasket (not shown). The sealed interior of the container 1 is a microenvironment protected from contaminants outside the container 1.

[0033] The substrate containers described are components of a system, e.g., a "substrate container system," that includes the substrate container and one or more accessories that can engage the substrate container during use, e.g., during steps of opening or closing the substrate container, inserting or removing a substrate into or from the container interior, adding a gaseous atmosphere to the container interior, etc. Accessories that can be incorporated into the system, called a "load port," may include: one or more sources of purge gas; a purge gas control that can include a flow controller that controls the volume or amount of purge gas flow, a temperature controller that controls the temperature of the purge gas, and a mixing control that combines two flows of different purge gases into a single purge gas mixture; a measurement system that measures or monitors a condition of the container (e.g., temperature, pressure, or humidity inside the container or in the atmosphere); and a control system that communicates with the substrate container system to affect or control a condition within the container or to control a condition (e.g., temperature) or flow rate of the purge gas.

[0034] An exemplary control system can be adapted to receive input from the substrate container system, such as measurements of the temperature, pressure, or relative humidity of the container atmosphere, and use that information to control the composition, temperature, or density of the purge gas dispensed inside the container. The exemplary control system can perform this function using at least a computerized hardware processor with a memory device operably connected to the processor. The memory can store instructions that are executed by the processor. According to various exemplary systems herein, the control system can include any form of microprocessor as the computer processor, such as a process logic controller (PLC controller) embedded in an application-specific integrated circuit (ASIC), or the like.

[0035] In an exemplary system, one or more sensors can be positioned relative to the substrate container system to measure the temperature, pressure, relative humidity, or two or more of the container atmosphere. The sensors may be located inside the container, at an inlet to measure the condition of gases flowing into the container, at an outlet to measure the condition of gases flowing from the container, at a source of purge gas, or at any other effective location. A process control system can receive one or more measurements from the system and use that information to select the composition, temperature, or density of the purge gas delivered to the container interior. The density of the purge gas may be controlled based on the composition (chemical make-up) of the purge gas, based on the temperature of the purge gas, or a combination thereof.

[0036] To deliver a purge gas having a desired composition, density, or temperature, the processor is adapted to execute instructions stored by the memory to perform one or more flow or temperature control functions. According to one example of a useful method, the process control system measures the temperature, pressure, relative humidity, or a combination thereof, of the vessel atmosphere. The control system contains software or hardware programmed to use the measured conditions of the vessel atmosphere to determine (or approximate) the density of the vessel atmosphere (i.e., "vessel atmosphere density" or "vessel atmosphere density value").

[0037] By one method, the control system can be programmed to use one or more measured vessel conditions (e.g., vessel atmosphere temperature, pressure, relative humidity) as inputs to a calculation to determine or approximate the vessel atmosphere density. As a specific example, the system may be programmed to use the Ideal Gas Law in combination with one or more other chemical relationships between moist air and the measured temperature, pressure, and relative humidity values ​​to identify the vessel atmosphere density value.

[0038] As a different method useful for determining the container atmosphere density value, the memory may include one or more correlation charts or tables relating the density of moist air to values ​​of conditions such as the temperature, pressure, and relative humidity of the moist air. These associations may be determined empirically, based on multiple calculations performed (optionally iteratively), or in any other effective manner. By any useful method, the system uses measured conditions of temperature, pressure, or relative humidity, or a combination thereof, and correlates the measured condition or conditions to, i.e., approximates, the container atmosphere moist air density.

[0039] Once the control system identifies the vessel ambient density value, the control system can distribute the purge gas inside the vessel while controlling the density of the purge gas ("purge gas density") to be approximately the same as the vessel ambient density value, for example, within 10 or 5 percent of the vessel ambient density value. Purge gas density can be controlled by controlling the composition of the purge gas, by controlling the temperature of the purge gas, or by controlling both the composition and temperature of the purge gas.

[0040] The purge gas can be supplied and delivered inside the vessel according to a novel method that differs from conventional methods and systems that use a single purge gas, which do not control the temperature of the purge gas or evaluate or control the density of the purge gas.

[0041] According to one exemplary method, the purge gas is supplied from two different purge gas sources, each source providing a different type (chemical make-up) of purge gas. In this manner, the two different types of purge gas may be delivered separately to the interior of the vessel, or the two different purge gases may be combined and delivered to the interior of the vessel as a purge gas mixture.

[0042] Different exemplary methods allow for the delivery of a single type of purge gas or purge gas mixture into a vessel interior while controlling the temperature of the purge gas or purge gas mixture, thereby controlling the density of the purge gas delivered into the vessel. The temperature of the purge gas or purge gas mixture can be controlled by any method or device, such as a cooling or heating device that removes or adds thermal energy from or to the purge gas or purge gas mixture, such as a heat exchanger, or by forcing the purge gas or purge gas mixture under pressure through an orifice to expand the purge gas or purge gas mixture and reduce its temperature.

[0043] As a comparison to previous purge systems and methods, FIG. 2 illustrates an example of a substrate container as part of a substrate container system that does not include, but can be adapted to include, the features of the substrate containers and systems described herein. The system 100 includes a substrate container 102 having an (inner) FOUP door 118 and an outer (front-opening interface mechanical standard, or FIMS) door 122, which may be part of a separate device such as a load port, and contains multiple substrates 104 held within an interior 106. The container 102 includes an inlet 110 that allows gas to enter the interior 106 and an outlet 116 that allows gas to flow from the interior 106 to the exterior of the container 102 as exhaust 130. The system 100 also includes a purge gas source 120, which may be a source of any useful purge gas, such as nitrogen gas or clean, dry air (e.g., "XCDA"). A flow meter 124 controls the flow of purge gas from the source 120 to the inlet 110 and the interior 106. The vessel 102 also includes an opening (not shown) through one side of the vessel that allows access to the interior 106, and a door (not shown) that can be selectively placed over or removed from the opening. The illustrated system 100 does not include a second type of purge gas, and does not include any device or control system adapted to control the temperature or density of the purge gas delivered to the interior 106.

[0044] In use, the container 102 is used to hold the substrate 104, for example, for transporting the substrate. The substrate 104 can initially be placed within the interior 106 with the container door 118 removed. After the substrate 104 is placed within the interior, the door 118 is placed over the opening to enclose and seal the container interior with the substrate inside. While the substrate is placed within the interior, the atmosphere within the interior 106 is that of the substrate and container environment, typically a clean room atmosphere. A typical clean room atmosphere for processing semiconductor and microelectronic products has a relative humidity in the range of less than 60 percent, e.g., less than 50 percent, e.g., 20-60 percent, e.g., 40-50 percent, at room temperature, e.g., about 22°C (e.g., 20-25°C), and ambient pressure (about 1 atmosphere). When the door is placed over the opening, the container interior contains this clean room atmosphere and includes the moisture content of the clean room environment.

[0045] When a substrate is placed inside the container, the substrate may have moisture (e.g., adsorbed moisture) on the substrate surface. The cleanroom atmosphere inside the container may also contain moisture. When a substrate is placed inside the container, the amount of moisture in the container atmosphere may change due to wetting or drying of the substrate surface. During the period when the substrate is contained inside the sealed container, the moisture from the substrate surface equilibrates with the moisture (humidity) in the container atmosphere. When the container is opened to remove the substrate, the container atmosphere may have a wide range of possible relative humidities, such as greater than 2 percent to 100 percent relative humidity (at 21°C), for example, a relative humidity that may be anywhere from 5, 10, 20, or 30 percent to 50, 60, 70, 80, 90, or 100 percent at room temperature, e.g., 22°C.

[0046] For various reasons and at different stages of handling substrates with a substrate container, the container atmosphere may be exchanged for a different atmosphere, often an atmosphere of a gas that does not contain significant amounts of moisture. For example, the container atmosphere may be purged with a dry gas while or before the substrate container door is open. As another example, the container atmosphere may be purged between process steps or after the container is closed and exits the load port. Alternatively, after storage and transfer of wafers held within the container, the container atmosphere may be purged when the container is removed while the door is removed from the container.

[0047] As part of the process of opening a substrate container to remove substrates of the type used in semiconductor and microelectronic processing, the gaseous atmosphere inside the container may be purged to replace (displace) the moist air container atmosphere with a new dry gaseous atmosphere. Purging the container interior may be used to replace the atmosphere inside the container containing moisture content in the form of humidity. The purging step may be performed with the door open (removed) or with the door closed (attached and covered). The humidity-containing container atmosphere is replaced with a different atmosphere of dry gas, such as clean dry air or nitrogen gas (meaning pure nitrogen), to remove moisture, which, if left with the substrate, can act as a contaminant or impurity on the surface of the substrate and may cause oxidation or other chemical reactions, reducing yield.

[0048] According to conventional methods for purging moist air from substrate containers containing microelectronic or semiconductor substrates, the interior is purged with either nitrogen gas or clean, dry air as a purge gas. Users of substrate containers in the microelectronic and semiconductor processing industries choose either nitrogen gas or clean, dry air as a purge gas. To the applicant's knowledge, no commercially available systems or methods are designed to use a combination of clean, dry air and nitrogen gas together as purge gases.

[0049] Applicant has determined that the limited choice of using either nitrogen gas or clean dry air as a purge gas results in relatively inefficient purging of the moist air container atmosphere. The inefficiency can arise from the difference in density of either of these types of purge gases compared to the density of the moist air container atmosphere.

[0050] The density difference between the purge gas and the container atmosphere can cause the flow of purge gas through the container interior to be significantly non-uniform at various vertical locations within the container interior. A purge gas having a higher density compared to the density of the container atmosphere will tend to flow, at least initially, along the bottom of the container interior, below the container atmosphere, and will tend to displace the container atmosphere located at the bottom first and more slowly displace the container atmosphere located at the top ("upper portion") of the container. Conversely, a purge gas having a lower density compared to the density of the container atmosphere will tend to flow, at least initially, above the container atmosphere, along the top of the container interior, and will tend to displace the container atmosphere located at the top of the container interior first and more slowly displace the container atmosphere located at the lower portion or bottom of the container.

[0051] In a typical process for purging moist air from the interior of a substrate container containing substrates used in semiconductor or microelectronic processing, the container atmosphere is at ambient temperature and has a relative humidity ranging from 2 to 100 percent. In many such processes, the density of the moist air ranges from 1.1 to 1.25 kilograms per cubic meter, e.g., 1.15 to 1.21 kilograms per cubic meter. According to the described method, the purge gas can have a density that approximates or matches the density of moist air, and can also be within these density ranges. The purge gas can be of any composition and may be prepared, processed, and handled in any useful manner to have a density that approximates or matches the density of the moist air in the container atmosphere.

[0052] According to an exemplary technique, the density of the purge gas may be controlled by controlling the chemical composition of the purge gas. In one example, the purge gas can contain a combination of two different types of purge gases, i.e., a purge gas mixture, where the chemical composition of the purge gas mixture is selected to have a density that approximates the density of moist air in the container atmosphere. Clean, dry air is denser than moist air, and nitrogen gas is less dense than moist air. By increasing the concentration of nitrogen in the clean, dry air, the density of the clean, dry air can be reduced to approximate the density of moist air. More generally, by combining a large amount of clean, dry air with a small amount of nitrogen gas, a purge gas mixture with the density of moist air can be produced. The specific density of the purge gas mixture can be controlled by controlling the relative amounts of nitrogen gas and clean, dry air in the purge gas. According to the described exemplary method, the amount of nitrogen gas added to the clean, dry air can be sufficient to produce a purge gas mixture with approximately the same density as the moist air of the container atmosphere being purged.

[0053] In a typical process for purging moist air from the interior of a substrate container containing semiconductor or microelectronic substrates, a purge gas mixture made from (consisting of, or consisting essentially of) a combination of clean, dry air and nitrogen gas may contain 50 to 97 mole percent clean, dry air and 3 to 50 percent nitrogen gas (with less than 0.01 or 0.001 mole percent water).

[0054] Considering the relative amounts of nitrogen and oxygen in the purge gas, an exemplary purge gas mixture may contain 78.5 or 79 up to 98.5 mole percent nitrogen and 20.5 or 20 up to 0.5 mole percent oxygen (with less than 0.01 or 0.001 mole percent water). Such purge gas mixtures can be prepared by combining clean, dry air with nitrogen gas, by combining nitrogen gas with oxygen gas, or by combining any two or more different types of purge gas.

[0055] As an additional or alternative method for controlling the density of the purge gas, the density can be controlled by controlling the temperature of the purge gas. For example, nitrogen gas at room temperature has a density less than that of moist air at room temperature. To control the density of nitrogen gas to be approximately the same as that of moist air (e.g., having a density in the range of 1.1 to 1.25 kilograms per cubic meter), the temperature of the nitrogen can be controlled to be lower than the temperature of the moist air in the container atmosphere (at common ambient pressure). In a typical process for purging moist air from the interior of a substrate container containing semiconductor or microelectronic substrates, the nitrogen gas supplied to the container atmosphere may have a temperature in the range of 11 to 15°C.

[0056] Clean, dry air at room temperature has a density greater than that of moist air at room temperature. Because the clean, dry air has approximately the same density as moist air (e.g., a density in the range of 1.1 to 1.25 kilograms per cubic meter), the temperature of the clean, dry air can be controlled to a temperature higher than the temperature of the moist air in the container atmosphere. In a typical process for purging moist air from the interior of a substrate container containing semiconductor or microelectronic substrates, clean, dry air can be supplied to the container atmosphere at a temperature in the range of 20 to 23°C.

[0057] Referring to FIG. 3A, the system 100 is shown having a container atmosphere 140 (shaded) of humid air filling the interior space, including an upper or top portion 106a and a lower or bottom portion 106b. In the examples of FIGS. 3A, 3B, and 3C, both the (inner) FOUP door 118 and the outer (Front Opening Interface Mechanical Standard, FIMS) door 122 are closed. FIG. 3B illustrates the delivery of clean, dry air from a source of clean, dry air through the inlet 110 to the interior 106. The clean, dry air flows through the interior 106 and exits the interior 106 as exhaust air 130. The moisture-free clean, dry air (dark shaded) 142 has a density greater than the density of the humid air 140 of the container atmosphere. The higher the density, the more the clean, dry air 142 tends to flow through the bottom 106b of the interior 106. This reduces the flow of clean, dry air 142 through the upper portion 106a and slows the replacement of moist air 140 by clean, dry air 142 in the upper portion 106a.

[0058] FIG. 3C illustrates a different example of an inefficient purging step using nitrogen gas 144. Referring again to FIG. 3A, the conventional system 100 is shown having a moist air container atmosphere (shaded) 140 filling the interior space 106, including an upper portion or top portion 106a and a lower portion or bottom portion 106b. FIG. 3C illustrates the delivery of nitrogen gas 144 from a nitrogen gas source 120 through an inlet 110 to the interior 106. The nitrogen gas 144 has a density less than that of the moist air in the container atmosphere 140. The nitrogen gas 144 tends to flow more through the upper portion 106a of the interior 106. This reduces the flow of nitrogen gas 144 through the bottom portion 106b, slowing the replacement of the moist air container atmosphere 140 with nitrogen gas 144 at the bottom portion 106b.

[0059] The methods and systems herein can perform purging of a humid air atmosphere of a substrate container in a manner that improves flow uniformity between the top and bottom of the container's interior. A purge step with improved uniformity of purge gas flow through different portions (top and bottom) of the substrate container can be more efficient and, for example, can be completed in less time compared to a purge step having non-uniform flow of purge gas at different top and bottom portions of the container interior. In exemplary methods and systems, the density of the purge gas used to replace the humid air container atmosphere is controlled to approximate the density of the container atmosphere being replaced.

[0060] In an exemplary system, the substrate container system can include a sensor and a process control system adapted to determine (e.g., estimate or approximate) a density value of the container atmosphere being displaced from inside the container. Using the process control system, the substrate container system can determine the density value of the container atmosphere and, in response to the density value, can control the density of the purge gas entering the container interior to displace the container atmosphere.

[0061] The conditions of the system, including the temperature, pressure, and relative humidity of the vessel atmosphere, can be measured by sensors adapted to measure these conditions. Any one or more of these sensors can be included as part of the system in a location effective to measure the conditions. For example, the sensors may be located inside the vessel or at or near an outlet of the vessel.

[0062] Using one or more of the measured conditions, a density value of the container atmosphere, which is moist air, can be determined or approximated by comparing those conditions with information stored in the memory of the process control system that correlates previously assessed and compiled conditions of moist air pressure, temperature, and relative humidity to a moist air density value. Alternatively, the measured conditions may be used to calculate a value of the moist air density of the container atmosphere using known mathematical equations that can identify a moist air density value based on the measured relative humidity, pressure, temperature, or a combination thereof.

[0063] An exemplary system herein is shown in FIG. 4A. The system 200 is shown including a substrate container 202 containing a plurality of substrates 204 held within an interior 206. The container 202 includes an inlet 210 that allows a purge gas to flow into the interior 206 and an outlet 216 that allows gas to flow from the interior 206 to the exterior of the container 202 as an exhaust 230. The container 202 also includes an opening (not shown) through one side of the container that allows access to the interior 206, and an inner door 218 that can be selectively positioned over or removed from the opening. An outer door 222, for example of a load port, can also be selectively opened and closed to allow access to the inner door 218 and the container 200.

[0064] System 200 also includes two separate purge gas sources 220a and 220b, which may be any two different sources of purge gas, such as a source of nitrogen gas and a source of clean, dry air. Flow meters 224a and 224b independently control the flow of the two different purge gases from sources 220a and 220b to inlet 210 and interior 206. As shown, the two different purge gases flowing from the two different purge gas sources 220a and 220b are combined to form a single combined purge gas (or “purge gas mixture”) that flows into inlet 210.

[0065] The substrate container system 200 also includes a control system including a microprocessor 250 connected to the sensors and flow controllers of the system 200. The microprocessor 250 is connected to both the flow controllers 224a and 224b and to one or more sensors 226 adapted to measure one or more of the pressure, temperature, or relative humidity of the moist air of the container atmosphere in the interior 206. The process control system can measure the conditions of the container atmosphere and determine a density value of the container atmosphere and, based on the density value, deliver a purge gas mixture to the interior 206 having a density that approximates the density value of the moist air container atmosphere. The system can control the density of the purge gas by combining nitrogen gas and clean, dry air in relative amounts to produce a purge gas mixture having a density that approximates the density value of the container atmosphere.

[0066] 4B also includes two separate purge gas sources 220a and 220b and further includes a temperature controller 232 that can be used to control the temperature of a purge gas mixture produced by combining a quantity of nitrogen gas from source 220b with clean, dry air from source 220a. The temperature of the purge gas mixture may be controlled to further control the density of the purge gas mixture delivered to interior 206.

[0067] 4C, system 200 includes only a single purge gas source 220, which can be either a source of nitrogen gas or a source of clean dry air or a different gas. A flow meter 224 controls the flow of purge gas from source 220 to inlet 210 and interior 206. System 200 also includes a temperature control device 232 useful for controlling the temperature, and therefore the density, of the purge gas delivered from source 220 to interior 206.

[0068] The illustrated substrate container system 200 includes a control system including a microprocessor 250 connected to the sensors and flow controllers of the system 200. Referring to Figure 4A, the microprocessor 250 is connected to both the flow controllers 224a and 224b and to one or more sensors 226 adapted to measure one or more of the pressure, temperature, or relative humidity of the humid air of the container atmosphere contained in the interior 206. The process control systems of the exemplary substrate container systems 200 of Figures 4B and 4C are equivalent, with the following exceptions: the control system of Figure 4B additionally communicates with a temperature controller 232, while the control system of Figure 4C communicates with the temperature controller 232 but only with the single flow meter 224.

[0069] The process control system in each example can measure the conditions of the vessel atmosphere, determine (by any useful method or approximation) a density value of the vessel atmosphere, and, based on the density value, deliver a purge gas or purge gas mixture to the interior 206 having a density that approximates the density value of the vessel atmosphere, with the example system controlling the density of the purge gas by controlling the composition of the purge gas mixture (FIG. 4A), by controlling the temperature of a single type of purge gas (FIG. 4C), or by controlling both the temperature and composition of the purge gas mixture (FIG. 4B).

[0070] During use, each example container 202 holds a substrate 204, for example, to transport the substrate. While the substrate 204 is disposed within the interior 206, the atmosphere within the interior 206 is that of the substrate and the container, which is typically a clean room atmosphere. The substrate 204 may have moisture (e.g., adsorbed moisture) on the substrate surface, which becomes moisture within the container atmosphere. When the container is opened, the container atmosphere may have any relative humidity greater than 2 percent (at room temperature, e.g., 22°C), e.g., anywhere from 5 to 100 percent, typically 40 to 50 percent (at room temperature, e.g., 22°C). To remove the moist air from the container atmosphere, the interior of the container is purged with a dry purge gas.

[0071] 5A, the system 200 of FIG. 4B is shown having a vessel atmosphere 240 (shaded) filling the interior space 206, which includes an upper portion or top portion 206a and a lower portion or bottom portion 206b. FIG. 5B illustrates the delivery of a purge gas mixture 246 (lightly shaded) prepared by combining two different sources of purge gas, for example, a source of clean, dry air 220b and a source of nitrogen 220a, into the interior 206 via the inlet 210.

[0072] 5B, the purge gas density can be controlled by controlling the composition of the purge gas mixture 246 (i.e., the relative amounts of nitrogen gas and clean, dry air), or by controlling the temperature of the purge gas mixture 246, or by controlling both the composition and temperature of the purge gas mixture 246. Alternatively, an exemplary system may control the purge gas density of a single type of purge gas (not a mixture) by controlling only the temperature of the purge gas (see FIG. 4C), or by controlling only the composition of the purge gas (see FIG. 4A).

[0073] In each example (FIGS. 4A, 4B, and 4C), the vessel atmosphere 240 has a density that can be determined or estimated by any useful measurement technique, calculation, or comparison of the conditions of the atmosphere 240 with empirical data correlating moist air pressure, temperature, or relative humidity to moist air density. The purge gas (e.g., purge gas mixture) 246 can be controlled to have a composition, temperature, or both that results in a purge gas density approximately equal to the density of the vessel atmosphere 240. This results in a relatively uniform flow of purge gas 246 through the upper and lower portions 206a and 206b, as shown in FIG. 5B.

[0074] The exemplary systems and methods may also be useful for performing a purge step of the container while the doors 118 and 122 are in the open position, the front opening of the container is uncovered, and wafers can be removed from the interior 106, as shown in Figures 6A, 6B, and 6C.

[0075] 6A, a conventional system 100 is shown having a container atmosphere 140 (shaded) of humid air filling an interior space including an upper portion or top 106a and a lower portion or bottom 106b. In FIG. 6A, the FOUP door 118 and outer door 122 are lowered relative to the front of the container to expose the front opening of the container and allow access to the interior 106 and the wafers held therein.

[0076] 6B illustrates the delivery of clean, dry air from a clean, dry air source through the inlet 110 to the interior 106. The clean, dry air flows through the interior 106 and exits the interior 106 through the uncovered front opening (see arrows). The moisture-free clean, dry air (dark shading) 142 has a density greater than the density of the moist air in the container atmosphere 140. The higher the density, the more the clean, dry air tends to flow through the bottom 106b of the interior 106. This reduces the flow of the clean, dry air 142 through the upper portion 106a, slowing the replacement of the container atmosphere 140 with the clean, dry air 142 in the upper portion 106a.

[0077] FIG. 6C illustrates a different example of an inefficient purging step using nitrogen gas 144. Referring again to FIG. 6A, the conventional system 100 is shown having a container atmosphere 140 (shaded) of moist air filling the interior space, including the upper or top portion 106a and the lower or bottom portion 106b. FIG. 6C illustrates the delivery of nitrogen gas 144 from the nitrogen gas source 120 through the inlet 110 to the interior 106. The nitrogen gas 144 flows through the interior 106 and exits the interior 106 through the uncovered front opening (see arrows). The nitrogen gas 144 has a density less than that of the moist air 140 of the container atmosphere. The nitrogen gas 144 tends to flow more through the upper portion 106a of the interior 106. This reduces the flow of nitrogen gas 144 through the bottom portion 106b, slowing the replacement of the container atmosphere 140 with nitrogen gas 144 at the bottom portion 106b.

[0078] 7A, system 200 is shown having a container atmosphere 240 (shaded) of humid air filling interior space 206, including upper portion or top 206a and lower portion or bottom 206b. FIG. 7B illustrates the delivery of a purge gas mixture 246 (lightly shaded) prepared by combining two different sources of purge gas, for example, a source of clean dry air 220b and a source of nitrogen 220a, into interior 206 via inlet 210.

[0079] 7B, the purge gas density can be controlled by controlling the composition of the purge gas mixture 246 (i.e., the relative amounts of nitrogen gas and clean, dry air), or by controlling the temperature of the purge gas mixture 246, or by controlling both the composition and temperature of the purge gas mixture 246. Alternatively, an exemplary system may control the purge gas density of a single type of purge gas (not a mixture) by controlling only the temperature of the purge gas (see FIG. 4C), or by controlling only the composition of the purge gas (see FIG. 4A).

[0080] Aspects:

[0081] Aspect 1. A method of purging a substrate container with a purge gas, comprising: a container body including an opening; a door adapted to cover the opening; an interior defined by a container body; a substrate supported within the interior; The atmosphere inside the container, One or more internal purge gas inlets and The method comprises: Distributing a purge gas therein through one or more inlets, the purge gas being clean, dry air received from a source of clean, dry air; and Nitrogen gas received from a nitrogen gas source Including A method comprising:

[0082] Embodiment 2. The method of embodiment 1, wherein the clean, dry air comprises about 78 mole percent nitrogen (N2) and about 21 mole percent oxygen (O2).

[0083] Embodiment 3. The method of embodiment 1 or 2, wherein the nitrogen gas has a purity of at least 99.99 mole percent nitrogen.

[0084] Aspect 4. Combining clean, dry air and nitrogen gas to produce a purge gas mixture having a gas mixture density; Distributing a purge gas mixture through the inlet; Controlling the purge gas mixture density to approximate the density of the container atmosphere. 4. The method of any one of aspects 1 to 3, comprising:

[0085] Aspect 5. The purge gas mixture comprises: 50 to 97 mole percent clean, dry air; 3 to 50 mole percent nitrogen gas 5. The method of embodiment 4, comprising:

[0086] Aspect 6. The purge gas mixture comprises: about 78.5 mole percent to 98.5 mole percent nitrogen; About 20.5 mole percent to 0.5 mole percent oxygen 5. The method of embodiment 4, comprising:

[0087] Embodiment 7. The method of any one of embodiments 4 to 6, wherein the purge gas mixture density is within 5 percent of the container atmosphere density.

[0088] Embodiment 8. The method of any of embodiments 4 to 7, wherein the purge gas mixture flows with better uniformity between the upper portion of the interior and the lower portion of the interior compared to an equivalent flow of clean dry air alone and compared to an equivalent flow of nitrogen gas.

[0089] Embodiment 9. The method of any of embodiments 4 to 8, comprising measuring the humidity, pressure, and temperature of the container atmosphere, and forming the purge gas mixture from amounts of clean, dry air and nitrogen based on the humidity, pressure, or temperature of the container atmosphere.

[0090] Embodiment 10. The method of any one of embodiments 1 to 10, wherein the purge gas mixture has a density in the range of 1.15 to 1.21 kilograms per cubic meter.

[0091] Embodiment 11. The method of any one of embodiments 1 to 10, wherein the door is removed and the opening is uncovered.

[0092] Embodiment 12. The method of any one of embodiments 1 to 10, wherein the door covers the opening.

[0093] Aspect 13. A method of purging a substrate container with a purge gas, the method comprising: a container body including an opening; a door adapted to cover the opening; an interior defined by a container body; a substrate supported within the interior; The atmosphere inside the container, an internal purge gas inlet; Purge gas source and The method comprises: measuring the relative humidity of the container atmosphere; controlling the density of the purge gas based on the relative humidity of the container atmosphere; and distributing a purge gas therein through the inlet. Including, a method.

[0094] Aspect 14. The source of purge gas comprises: a source of clean, dry air; Nitrogen gas source and and the purge gas comprises a flow of clean, dry air received from a source of clean, dry air; The flow of nitrogen gas received from the nitrogen gas source and and a purge gas mixture containing 14. The method of embodiment 13, wherein the method comprises selecting a flow rate of clean dry air and a flow rate of nitrogen gas to control the density of the purge gas mixture.

[0095] Embodiment 15. The method of embodiment 13 or 14, comprising controlling the temperature of the purge gas mixture to control the density of the purge gas.

[0096] Embodiment 16. The method of embodiment 13, wherein the purge gas comprises clean, dry air, and the method comprises controlling a temperature of the clean, dry air to control the density of the clean, dry air.

[0097] Embodiment 17. The method of embodiment 13, wherein the purge gas comprises nitrogen gas, and the method comprises controlling the temperature of the nitrogen gas to control the density of the nitrogen gas.

[0098] Embodiment 18. The method of embodiment 17, comprising controlling the temperature of the purge gas by flowing the purge gas through an orifice to increase the volume of the purge gas and change the temperature of the purge gas.

[0099] Embodiment 19. The method of any of embodiments 13 to 18, comprising controlling the purge gas density to within 10 percent of the container ambient density.

[0100] Embodiment 20. The method of any one of embodiments 13 to 19, wherein the purge gas has a density in the range of 1.15 to 1.21 kilograms per cubic meter when dispensed therein.

[0101] Aspect 21. Measuring the humidity, pressure, and temperature of the container atmosphere; Controlling the density of the purge gas based on the relative humidity, pressure, and temperature of the vessel atmosphere 21. The method of any of embodiments 13 to 20, comprising:

[0102] Embodiment 22. The method of any one of embodiments 13 to 21, wherein the door is removed and the opening is uncovered.

[0103] Embodiment 23. The method of any one of embodiments 13 to 21, wherein the door is removed and the opening is uncovered.

[0104] Aspect 24. A container body including an opening; a door adapted to be placed over and removed from the opening; an interior defined by a container body; a substrate supported within the interior; The atmosphere inside the container, an internal purge gas inlet; A source of clean, dry air; and Nitrogen gas source a source of purge gas comprising: a purge gas flow control system that combines a flow of clean, dry air with a flow of nitrogen gas to create a purge gas mixture; A substrate container system comprising:

[0105] Aspect 25. A control system comprising: a first flow meter controlling the flow of clean, dry air to the purge gas inlet; a second flow meter controlling the flow of nitrogen gas to the purge gas inlet; 25. A substrate container system according to embodiment 24, comprising:

[0106] Embodiment 26. The substrate container system of embodiment 24 or 25, comprising a temperature control device that controls the temperature of the purge gas.

[0107] Embodiment 27. The substrate container system of embodiment 25, wherein the temperature control device is a mechanical orifice.

[0108] Embodiment 28. A substrate container system according to any of embodiments 24 to 27, comprising a relative humidity sensor, wherein the purge gas flow control system selects a flow rate of clean dry air, or a flow rate of nitrogen gas, or a flow rate of clean dry air and nitrogen gas based on the measured relative humidity of the system.

[0109] Aspect 29. A container body including an opening; a door adapted to be placed over and removed from the opening; an interior defined by a container body; a purge gas inlet connected thereto; a relative humidity sensor; a source of purge gas; a control system for controlling the density of the purge gas distributed therein through the purge gas inlet; A substrate container system comprising:

[0110] Embodiment 30. The substrate container of embodiment 29, wherein the control system comprises a mechanical orifice in the flow of the purge gas, reducing the temperature of the purge gas as it flows through the mechanical orifice.

[0111] Aspect 31. The source of purge gas comprises: a source of clean, dry air; Nitrogen gas source and and a control system comprising: a flow meter for controlling the flow of clean, dry air into the purge gas inlet; a flow meter controlling the flow of nitrogen to the purge gas inlet; 29. The substrate container of embodiment 27 or 28, comprising:

[0112] Embodiment 32. The substrate container of embodiment 30 or 31, wherein the source of purge gas comprises a source of clean, dry air, and the control system comprises a temperature controller that controls the temperature of the clean, dry air.

[0113] Embodiment 33. The substrate container of embodiment 30 or 31, wherein the source of purge gas comprises a source of nitrogen gas, and the control system comprises a temperature controller that controls the temperature of the nitrogen gas.

[0114] Aspect 34. A method comprising distributing a purge gas mixture through an inlet of a substrate container, wherein the purge gas mixture comprises a combination of clean, dry air and nitrogen gas.

[0115] 35. The purge gas mixture comprises: 50 to 97 mole percent clean, dry air; 3 to 50 mole percent nitrogen gas 35. The method of embodiment 34, comprising:

[0116] Embodiment 36. The method of embodiment 34, wherein the purge gas mixture has a density in the range of 1.1 to 1.25 kilograms per cubic meter.

[0117] Embodiment 37. The method of any one of embodiments 34 to 36, wherein the door is removed and the opening is uncovered.

[0118] Embodiment 38. The method of any one of embodiments 34 to 36, wherein the door is removed and the opening is uncovered.

Claims

1. a container body including an opening; a door adapted to be placed over and removed from the opening; an interior defined by the container body; and a substrate supported within the interior; a container atmosphere within the interior; a purge gas inlet in the interior; A source of clean, dry air; and Nitrogen gas source a source of purge gas comprising: a purge gas flow control system that combines the flow of clean, dry air and the flow of nitrogen gas to produce a purge gas mixture; A substrate container system comprising:

2. the control system a first flow meter for controlling the flow of the clean, dry air into the purge gas inlet; a second flow meter controlling the flow of the nitrogen gas to the purge gas inlet; The substrate container system of claim 1 , comprising:

3. The substrate container system of claim 2 , further comprising a temperature control device for controlling the temperature of the purge gas.

4. The substrate container system of claim 2 , wherein the temperature control device is a mechanical orifice.

5. 5. The substrate container system of claim 4, further comprising a relative humidity sensor, wherein the purge gas flow control system selects a flow rate of the clean dry air, or a flow rate of the nitrogen gas, or a flow rate of the clean dry air and the nitrogen gas based on the measured relative humidity of the system.

6. The substrate container system of claim 10 further comprising a pressure sensor and a temperature sensor.

7. 12. The substrate container system of claim 11, wherein the humidity sensor measures the humidity, the pressure sensor measures the pressure, and the temperature sensor measures the temperature of the container atmosphere, and the control system forms a purge gas mixture from the amounts of the clean dry air and the nitrogen based on the humidity, the pressure, or the temperature of the container atmosphere.

8. a container body including an opening; a door adapted to be placed over and removed from the opening; an interior defined by the container body; and a purge gas inlet connected to the interior; a relative humidity sensor; a source of purge gas; a control system for controlling the density of purge gas distributed to the interior through the purge gas inlet; A substrate container system comprising:

9. 10. The substrate container system of claim 8, wherein the control system comprises a mechanical orifice in a flow of purge gas to reduce a temperature of the purge gas as the purge gas flows through the mechanical orifice.

10. the source of purge gas is a source of clean, dry air; Nitrogen gas source and and the control system comprises: a flow meter for controlling the flow of the clean, dry air into the purge gas inlet; a flow meter for controlling the flow of the nitrogen to the purge gas inlet; The substrate container system of claim 9 , comprising:

11. 11. The substrate container system of claim 10, wherein the source of purge gas comprises a source of clean, dry air, and wherein the control system includes a temperature controller for controlling the temperature of the clean, dry air.

12. 11. The substrate container system of claim 10, wherein the source of purge gas comprises a source of nitrogen gas, and the control system includes a temperature controller for controlling a temperature of the nitrogen gas.

13. 1. A method for purging a substrate container with a purge gas, the method comprising: a container body including an opening; a door adapted to cover the opening; an interior defined by the container body; and a substrate supported within the interior; a container atmosphere within the interior; one or more purge gas inlets within said interior; wherein the method comprises: into the interior through the one or more inlets; clean, dry air received from a source of clean, dry air; and Nitrogen gas received from a nitrogen gas source and dispensing a purge gas comprising:

14. combining the clean, dry air and the nitrogen gas to form a purge gas mixture having a gas mixture density; distributing the purge gas mixture through an inlet; controlling the density of the purge gas mixture to approximate the density of the container atmosphere; 14. The method of claim 13, comprising:

15. 15. The method of claim 14, comprising measuring the humidity, pressure, and temperature of the container atmosphere, and forming the purge gas mixture from amounts of clean, dry air and nitrogen based on the humidity, the pressure, or the temperature of the container atmosphere.

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