Substrate container system and method for purging substrate containers

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 a substrate container useful for holding or transferring a "substrate" (e.g., a semiconductor wafer, etc.) in a clean environment, which is sometimes referred to as a "substrate carrier" or "wafer container", and a method of using the substrate container.

Background Art

[0002] Microelectronic devices are fabricated on a semiconductor substrate through a series of precise processing steps, each performed under extremely clean conditions. Between processing steps, the "substrate" on which microelectronic devices are being formed may be transferred from one processing location to a different processing location.

[0003] To transfer a substrate between processing steps or separate processing locations, the substrate is held in a dedicated container designed to prevent damage to the substrate while shielding the substrate from contamination. Exemplary substrate containers may be referred to as "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 accommodating a plurality of semiconductor wafers or other substrates within an atmosphere that may be evacuated (i.e., under reduced pressure) or may contain a gas different from air, such as an inert gas.

[0004] The substrate container may be in the form of a multi-faced container body (e.g., a "shell") that defines the interior of the container. The container body includes an opening on one side that allows a plurality of 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 (inlet or outlet) 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 unit area of ​​semiconductor devices increases, the devices become more sensitive to particles and environmental contaminants. In smaller microelectronic devices, even smaller contaminants, and even molecular-sized contaminants, can disrupt the performance of the microelectronic device. As a result, continuous improvement in particle contamination control is required throughout all stages of semiconductor substrate processing, including during substrate transport between process steps.

[0006] To maintain a high level of cleanliness and avoid contamination of substrates during handling, there is a growing need for continuously improving systems and methods to control the gaseous environment within substrate containers. [Overview of the project]

[0007] During use of a substrate container, the gaseous atmosphere inside the container may need to be replaced with a fresh gaseous atmosphere for various reasons. To enable this, the container may include gas ports (i.e., openings or "inlets") that can deliver gas into or remove gas from the container.

[0008] As an example, a high-purity, clean, dry gas (called a "purge gas") can be distributed into the container to replace (i.e., displace) the previous atmosphere. When substrates are inserted into the container, they may contain moisture on their surfaces, which can enter the container atmosphere. At any desired time before the substrates are removed from the container, either before or after the container door is removed, the container atmosphere may be replaced with a new, moisture-free gaseous atmosphere, i.e., the inside of the container is "purged" with a dry atmosphere. Some purging methods use nitrogen as the dry purge gas to replace the container atmosphere. Other purging methods use clean, dry air as the purge gas.

[0009] The choice of whether to use nitrogen or clean, dry air as the 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 purging step may be to remove water vapor from the container. Both nitrogen and clean, dry air are effective in removing moisture. However, some processes are sensitive to the presence of oxygen. In these processes, nitrogen gas has the advantage of lowering the oxygen level in the container, as opposed to clean, dry air which contains oxygen. Nevertheless, clean, dry air is a 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 exorbitant. To the applicant's knowledge, commercial processes use either nitrogen or clean, dry air, or the other, but never use 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 favorably increases throughput and overall efficiency.

[0011] A commercial process, as determined by the applicant, that uses either nitrogen gas (pure nitrogen) or clean dry air, or the other, alone, without considering the density of the selected purge gas, produces uneven purging of the substrate container between the upper and lower container positions. This uneven purging leads to an increased time required to complete the purging 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. Dry air as a purge gas is denser than the moist air in the container atmosphere, so it tends to flow rapidly through the lower part of the substrate container, while requiring a significantly longer time to eventually replace the less dense, moist atmosphere at the upper container location. Conversely, nitrogen as a purge gas is lighter than moist air and rapidly replaces the atmosphere at the upper container location, but requires a significantly longer time to replace the atmosphere at the lower part of the container.

[0013] As determined by the applicant, the uniformity of the purge gas flow through the upper and lower portions inside the substrate container can be improved by controlling the density of the purge gas by using a purge gas with a density approximately the same as that of the container atmosphere. A purge gas with a density approximating that of the humid air inside the container replaces the humid air at the upper and lower container locations with significantly more uniformity. The more uniform flow of the purge gas through the container reduces the time required for the purging step compared to the time required when using a purge gas with 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 vessel in order to improve the uniformity of the flow of the purge gas through the vessel and reduce the time required to complete the purging step. The density of the purge gas may also be controlled by selecting a composition of the purge gas that has a density approximating the density of the humid air contained inside the vessel. The purge gas may be a mixture of two different types of purge gases, such as clean dry air or a mixture of oxygen and nitrogen (pure nitrogen), the mixture may have a density approximately equal to the density of the humid air in the vessel 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 humid air in the vessel atmosphere.

[0015] In one embodiment, the present invention relates to a method for purging a substrate container with a purge gas. The substrate container comprises a container body including an opening, a door fitted to cover the opening, an interior defined by the container body, a substrate supported inside, a container atmosphere inside, and one or more purge gas inlets inside. The method comprises distributing a purge gas into the interior through 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 embodiment, the present invention relates to a method for purging a substrate container with a purge gas. The substrate container includes a container body including an opening, a door fitted to cover the opening, an interior defined by the container body, a substrate supported inside, a container atmosphere inside, a purge gas inlet inside, and a source of purge gas. The method includes 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 the purge gas into the interior through the inlet.

[0017] In yet another embodiment, the present invention relates to a substrate container system comprising a container body having an opening; a door adapted to be positioned over and removable 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 located within the interior; and a purge gas source 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] In another embodiment, the present invention relates to a substrate container system comprising a container body including an opening; a door adapted to be positioned over and removable from the opening; an interior defined by the container body; a purge gas inlet connected to the interior; a relative humidity sensor; a purge gas supply source; and a control system for controlling the density of the purge gas distributed into the interior through the purge gas inlet.

[0019] In yet another aspect, the present invention relates to a method comprising distributing a purge gas mixture through the inlet of a substrate container, wherein the purge gas mixture comprises a combination of clean, dry air and nitrogen gas. [Brief explanation of the drawing]

[0020] [Figure 1] This is a perspective view of the exemplary wafer container described. [Figure 2] This is a side cross-section view of an exemplary wafer container. [Figure 3A] This is a side cross-section view of a wafer container and a conventional method for purging wafer containers. [Figure 3B] This is a side cross-section view of a wafer container and a conventional method for purging wafer containers. [Figure 3C] This is a side cross-section view of a wafer container and a conventional method for purging wafer containers. [Figure 4A] This is a side cross-section view of an exemplary wafer container as described herein. [Figure 4B]It is a side cutaway view of an exemplary wafer container according to the present specification. [Figure 4C] It is a side cutaway view of an exemplary wafer container according to the present specification. [Figure 5A] It is a side cutaway view of an exemplary wafer container described in the present specification and a method for purging a wafer container. [Figure 5B] It is a side cutaway view of an exemplary wafer container described in the present specification and a method for purging a wafer container. [Figure 6A] It is a side cutaway view of a wafer container and a conventional method for purging a wafer container. [Figure 6B] It is a side cutaway view of a wafer container and a conventional method for purging a wafer container. [Figure 6C] It is a side cutaway view of a wafer container and a conventional method for purging a wafer container. [Figure 7A] It is a side cutaway view of the described exemplary wafer container and a method for purging a wafer container. [Figure 7B] It is a side cutaway view of the described exemplary wafer container and a method for purging a wafer container. DETAILED DESCRIPTION OF EMBODIMENTS

[0021] All drawings are schematic and are not drawn to scale.

[0022] Hereinafter, a substrate container including a container body having an interior, an opening for accessing the interior provided on one side of the body, and a door adapted to cover and seal the opening is described. The container also includes one or more gas ports including 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”) which includes other devices, structures, or sources of raw materials used with the substrate container to handle the substrate in a clean environment. Exemplary components of a substrate container system include one or more of the following: a source of purge gas; optionally, separate sources of two or more different types of purge gas; sensors for measuring the state of the container, system, or process material (purge gas), e.g., a temperature sensor, a pressure sensor, or a humidity sensor; control devices, e.g., a temperature control device for controlling the temperature and thereby the density of the purge gas delivered into the container, or a flow control device for controlling the flow of a single purge gas, two different purge gases, or a mixture of two or more different purge gases (“purge gas mixture”); a process control system for controlling the conditions and process steps of the purging process, etc.

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

[0025] In exemplary methods, the purge gas may contain a mixture of two or more different types of purge gas supplied from two or more separate gas sources. For example, the system may deliver two different types of purge gas into the container, the two types being clean dry air as one type of purge gas and nitrogen gas as the second type of purge gas, with the clean dry air supplied from a source of clean dry air and the nitrogen gas supplied from a source of pure nitrogen gas. In another example, instead of clean dry air and nitrogen as the 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 the 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 as a mixture, optionally.

[0026] As used herein, the term “nitrogen gas” refers to pure nitrogen gas, meaning nitrogen gas containing at least 99.9 or 99.99 mole percent of nitrogen and less than 0.01 mole percent or less than 0.001 mole percent of moisture. The term “clean dry air” refers to a gaseous composition that is considered clean dry air, sufficiently pure and moisture-free for use in commercial steps processing semiconductors or microelectronic substrates, and includes gases containing about 78 mole percent of nitrogen (N2), about 21 mole percent of oxygen (O2), and less than 0.01 mole percent or less than 0.001 mole percent of moisture. An example of a clean dry air product is ultra-high purity extremely clean dry air (XCDA®) available from Entegris Inc., Billerica MA. The term “oxygen gas” refers to pure oxygen gas, meaning oxygen gas containing at least 99.9 or 99.99 mole percent of oxygen and less than 0.01 mole percent or less than 0.001 mole percent of moisture.

[0027] In these or other examples, the system may handle and process the purge gas (e.g., heating or cooling) to bring it to a desired density when it is delivered into the container. A useful purge gas density may be a density that approximates the density of the container atmosphere being replaced by the purge gas, for example, the purge gas may have a density of no more than 10 percent, or no more than 5 percent, or no more than 2 or 1 percent of the density of the container atmosphere. The purge gas may be a single type of purge gas, such as pure nitrogen ("nitrogen gas") or clean dry air, or a purge gas mixture prepared from two different types of purge gases, for example, by combining a flow of nitrogen gas from a nitrogen gas source and a flow of clean dry air from a clean dry air source.

[0028] A wafer container includes a multifaceted container body (sometimes called a “shell”) that defines the interior of the container, which is 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 interior of the container. The container also includes a door adapted to cover the opening and to form a seal that covers the opening between the interior and exterior of the container. A substrate container typically includes at least one inlet port adapted to allow a gas, e.g., “purge gas”, to be delivered into the interior of the container, and at least one (optional) outlet port that allows the gas from the interior of the container to flow out from the interior to the exterior. Optionally, a delivery device, sometimes called a “diffuser”, may be connected to the inlet port. The diffuser may be used to distribute the purge gas throughout the interior of the container, for example, by distributing the purge gas along the length of the diffuser, where the diffuser is positioned vertically along the height of the interior of the container.

[0029] The substrate container is adapted to accommodate multiple substrates. “Substrate” may be any of a variety of different generally flat structures known to be of a type commonly housed or transported in a substrate container apparatus to enable safe and clean handling and transport of substrates without causing damage or contamination of the substrates. Exemplary substrates include semiconductor wafers, their precursors, their derivatives, and in-process versions of any of these, e.g., in-process semiconductor wafers, in-process microelectronic devices, EUV (extreme ultraviolet) reticles, panels, or other structures known to be supported or housed on carriers as described herein, any of which may generally be referred to as “wafer” or “substrate.”

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

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

[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 in 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 container described is a component of a system, e.g., a “substrate container system,” which includes the substrate container and one or more accessories that can engage with the substrate container during use, for example, between steps such as opening or closing the substrate container, inserting a substrate into or removing a substrate from the container, or adding a gaseous atmosphere to the container. Accessories that can be incorporated into a system called a “load port” may include: one or more sources of purge gas; a purge gas control unit which may include a flow control unit for controlling the volume or amount of the purge gas flow, a temperature control unit for controlling the temperature of the purge gas, and a mixing control unit for combining two flows of different purge gases into a single purge gas mixture; a measuring system for measuring or monitoring the state of the container (e.g., temperature, pressure, or humidity inside the container or the atmosphere); and a control system which communicates with the substrate container system to affect or control the state inside the container, or to control the state (e.g., temperature) or flow rate of the purge gas.

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

[0035] In an exemplary system, one or more sensors may be positioned relative to the substrate container system to measure the temperature, pressure, relative humidity, or two or more of these of the container atmosphere. The sensors may be located inside the container, at the inlet to measure the state of the gas flowing into the container, at the outlet to measure the state of the gas flowing out of the container, at the purge gas source, or at any other effective location. The process control system may receive one or more measurements from the system and use this information to select the composition, temperature, or density of the purge gas delivered into the container. The density of the purge gas may be controlled based on the composition (chemical composition) 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 in memory to perform one or more flow or temperature control functions. One example of a useful method is for a process control system to measure the temperature, pressure, relative humidity, or a combination thereof of the container atmosphere. The control system houses software or hardware programmed to determine (or approximate) the density of the container atmosphere (i.e., "container atmosphere density" or "container atmosphere density value") using the measured conditions of the container atmosphere.

[0037] One method allows a control system to be programmed to use one or more measured container conditions (e.g., temperature, pressure, and relative humidity of the container atmosphere) as input to calculations that determine or approximate the density of the container atmosphere. 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 the humid air and the measured temperature, pressure, and relative humidity values ​​to determine the container 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 humid air to values ​​of conditions such as temperature, pressure, and relative humidity of the humid air. These correlations may be determined empirically, based on multiple calculations performed (optionally and iteratively), or by any other effective method. By any useful method, the system uses the measured conditions of temperature, pressure, or relative humidity, or a combination thereof, and correlates one or more of the measured conditions to the density of humid air in the container atmosphere, i.e., approximates the container atmosphere density.

[0039] Once the control system determines the container atmosphere density value, it can distribute the purge gas into the container while controlling the purge gas density ("purge gas density") to be approximately the same as the container atmosphere density value, for example, within 10 or 5 percent of the container atmosphere density value. The 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 into the container according to a novel method that differs from conventional methods and systems using a single purge gas, without controlling the temperature of the purge gas or evaluating or controlling the density of the purge gas.

[0041] In one exemplary method, the purge gas is supplied from two different sources, each supplying a different type (chemical composition) of purge gas. In this method, the two different types of purge gas may be delivered separately into the container, or they may be combined and delivered into the container as a purge gas mixture.

[0042] In different exemplary ways, a purge gas or purge gas mixture can be delivered into a container while controlling the temperature of a single type of purge gas or purge gas mixture, thereby controlling the density of the purge gas delivered into the container. The temperature of the purge gas or purge gas mixture can be controlled by any method or apparatus, for example, by a cooling or heating device that removes or adds thermal energy to the purge gas or purge gas mixture, such as a heat exchanger, or by pressurizing the purge gas or purge gas mixture through an orifice to expand it and lower its temperature.

[0043] For comparison with previous purging systems and methods, Figure 2 shows an example of a substrate container as part of a substrate container system, which does not include, but may be adapted to include, the features of the substrate container and system described herein. System 100 includes a substrate container 102 having an (internal) FOUP door 118 and an external (mechanical standard for front opening interface, FIMS) door 122, which may be part of a separate device such as a load port, and also houses a plurality of substrates 104 held within the interior 106. The container 102 includes an inlet 110 that allows gas to flow into the interior 106 and an outlet 116 that allows gas to flow out of the container 102 as exhaust 130 from the interior 106. 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 container 102 also includes an opening (not shown) that allows access to the interior 106 through one side of the container, and a door (not shown) that may be selectively positioned over the opening or selectively 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] During use, the container 102 is used, for example, to hold a substrate 104 for transport. The substrate 104 can first be placed inside the container 106 with the container door 118 removed. After the substrate 104 is placed inside, the door 118 is placed over the opening to seal the inside of the container with the substrate inside. While the substrate is placed inside, the atmosphere inside the container 106 is the atmosphere of the environment of the substrate and container, and is typically a cleanroom atmosphere. A typical cleanroom atmosphere for processing semiconductors and microelectronic products has a relative humidity in the range of less than 60 percent, for example less than 50 percent, for example 20 to 60 percent, for example 40 to 50 percent, at room temperature, for example about 22°C (e.g., 20-25°C) and ambient pressure (about 1 atmosphere). When the door is placed over the opening, the inside of the container contains this cleanroom atmosphere and the moisture content of the cleanroom environment.

[0045] When a substrate is placed inside a container, the substrate may have moisture on its surface (e.g., adsorbed moisture). The cleanroom atmosphere inside the container may also contain moisture. Once the 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 the substrate is contained inside the sealed container, moisture from the substrate surface equilibrium 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 relative humidity, such as relative humidity greater than 2 percent and up to 100 percent (at 21°C), for example, relative humidity that can range from 5, 10, 20, or 30 percent to 50, 60, 70, 80, 90, or 100 percent at room temperature, for example at 22°C.

[0046] For various reasons, and at different stages of handling substrates in a substrate container, the container atmosphere may be changed with a different atmosphere, often a gas atmosphere that does not contain a significant amount of moisture. For example, the container atmosphere may be purged with a dry gas while the substrate container door is open or before it is opened. As another example, the container atmosphere may be purged at a point between process steps, or after the container is closed and has exited the load port. Alternatively, the container atmosphere may be purged when removing the container while the door is detached from the container, after the storage and movement of wafers held in the container.

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

[0048] Conventional methods for purging moist air from substrate containers containing microelectronic or semiconductor substrates involve purging the interior with either nitrogen gas or clean, dry air as the purge gas. Users of substrate containers in the microelectronic and semiconductor processing industries select either nitrogen gas or clean, dry air as the purge gas. To the best of 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] The applicant has identified that the limited choice of using either nitrogen gas or clean, dry air as the purge gas results in relatively inefficient purging of a humid air container atmosphere. This inefficiency may arise from the difference in density between either of these types of purge gases and the humid air container atmosphere.

[0050] The difference in density between the purge gas and the container atmosphere can cause significant non-uniformity in the flow of the purge gas through the container at various vertical locations within the container. A purge gas with a higher density than the container atmosphere may, at least initially, flow along the bottom of the container and below the container atmosphere, displacing the container atmosphere located at the bottom first and displacing the container atmosphere located at the top of the container ("upper portion") more slowly. Conversely, a purge gas with a lower density than the container atmosphere may, at least initially, flow along the top of the container and above the container atmosphere, displacing the container atmosphere located at the top of the container first and displacing the container atmosphere located at the bottom portion or bottom of the container more slowly.

[0051] In a typical process of purging moist air from inside a substrate container housing substrates used in semiconductor or microelectronic processing, the container atmosphere is at room temperature and has a relative humidity in the range of 2 to 100 percent. In many such processes, the density of the moist air is in the range of 1.1 to 1.25 kilograms per cubic meter, for example, 1.15 to 1.21 kilograms per cubic meter. According to the method described, the purge gas may have a density that approximates or matches the density of the moist air, or may be within this range of densities. The purge gas may have any composition and may be prepared, processed, and handled in any useful way to have a density that approximates or matches the density of the moist air in the container atmosphere.

[0052] According to exemplary techniques, the density of the purge gas may be controlled by controlling the chemical composition of the purge gas. In one example, the purge gas may contain a combination of two different types of purge gases, i.e., a purge gas mixture, the chemical composition of which is selected to have a density approximating that 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 that of moist air, and more generally, by combining a large amount of clean dry air with a small amount of nitrogen gas, a purge gas mixture having the density of moist air can be produced. A 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 exemplary method described, the amount of nitrogen gas added to the clean dry air may be sufficient to produce a purge gas mixture having approximately the same density as the moist air in the container atmosphere being purged.

[0053] In a typical process of purging moist air from inside a substrate container housing a semiconductor or microelectronic substrate, a purge gas mixture prepared from (or consisting of) a combination of clean dry air and nitrogen gas may contain 50–97 mol percent of clean dry air and 3–50 percent of nitrogen gas (with less than 0.01 or 0.001 mol percent of 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 to a maximum of 98.5 mole percent of nitrogen and 20.5 or 20 to 0.5 mole percent of oxygen (with less than 0.01 or 0.001 mole percent of water). Such a purge gas mixture 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 gases.

[0055] As an additional or alternative method for controlling the density of a purge gas, the density can be controlled by controlling the temperature of the purge gas. For example, nitrogen gas at room temperature has a lower density than humid air at room temperature. To control the density of nitrogen gas to be approximately the same as that of humid 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 humid air in the container atmosphere (at a common ambient pressure). In a typical process of purging humid air from inside a substrate container housing a semiconductor or microelectronic substrate, 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 higher density than humid air at room temperature. Because clean, dry air has approximately the same density as humid air (for example, 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 be higher than the temperature of the humid air in the container atmosphere. In a typical process of purging humid air from inside a substrate container housing 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 Figure 3A, the system 100 is shown to have a container atmosphere 140 (shaded) of moist air filling the internal space, including the upper portion or top 106a and the lower portion or bottom 106b. In the examples of Figures 3A, 3B, and 3C, both the (inner) FOUP door 118 and the outer (mechanical standard, FIMS) door 122 of the front opening interface are closed. Figure 3B shows the step of delivering clean, dry air from a source of clean, dry air to the interior 106 through the inlet 110. The clean, dry air flows through the interior 106 and exits the interior 106 as exhaust 130. The clean, dry air (dark shading) 142, which does not contain moisture, has a higher density than the moist air 140 of the container atmosphere. The higher the density, the more likely the clean, dry air 142 is 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 down the replacement of moist air 140 by the clean, dry air 142 in the upper portion 106a.

[0058] Figure 3C shows a different example of an inefficient purging step using nitrogen gas 144. Referring again to Figure 3A, the conventional system 100 is shown to have a container atmosphere (shaded) 140 of moist air filling the internal space 106, which includes an upper portion or top 106a and a lower portion or bottom 106b. Figure 3C shows the step of delivering nitrogen gas 144 from a nitrogen gas source 120 through an inlet 110 into the interior 106. The nitrogen gas 144 has a lower density than 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 106b, slowing down the replacement of the container atmosphere 140, which is moist air, by the nitrogen gas 144 at the bottom 106b.

[0059] The methods and systems described herein can perform the step of purging a moist air atmosphere in a substrate container in a manner that improves the uniformity of the flow between the upper and lower parts of the container. A purging step with improved uniformity of the flow of the purge gas through different parts of the substrate container (upper and lower) can be more efficient and can be completed in a shorter time, for example, compared to a purging step with non-uniform flow of the purge gas in different upper and lower parts of the container. In exemplary methods and systems, the density of the purge gas used to replace the container atmosphere, which is moist air, is controlled to approximate the density of the container atmosphere being replaced.

[0060] In an exemplary system, the substrate container system may include sensors and process control systems adapted to determine (e.g., evaluate or approximate) the density value of the container atmosphere being replaced 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 that density value, control the density of the purge gas that enters the container and replaces the container atmosphere.

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

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

[0063] An exemplary system of this specification is shown in Figure 4A. A system 200 is shown, which includes a substrate container 202 housing 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 the gas to flow out of the container 202 as exhaust 230. The container 202 also includes an opening (not shown) that passes through one side of the container, allowing access to the interior 206, and an inner door 218 that may be selectively positioned above the opening or selectively removed from the opening. An outer door 222 of a load port, for example, may 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 sources of any two different purge gases, such as a nitrogen gas source and a clean, dry air source. Flow meters 224a and 224b independently control the flow of the two different purge gases from sources 220a and 220b to the inlet 210 and the interior 206. As shown in the figure, the two different purge gases flowing from the two different purge gas sources 220a and 220b combine to form a single combined purge gas (or “purge gas mixture”) that flows into the inlet 210.

[0065] The substrate container system 200 also includes a control system, which includes a microprocessor 250 connected to the sensors and flow control devices of the system 200. The microprocessor 250 is connected to both flow control devices 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 in the container atmosphere inside 206. The process control system can measure the conditions of the container atmosphere and determine the density value of the container atmosphere, and based on the density value, can deliver a purge gas mixture having a density approximating the density value of the container atmosphere, which is humid air, to the inside 206. 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 approximating the density value of the container atmosphere.

[0066] As a different example, the system 200 in Figure 4B similarly includes two separate purge gas sources 220a and 220b, and further includes a temperature control device 232 which can be used to control the temperature of the purge gas mixture produced by combining a certain amount 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 the interior 206.

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

[0068] The illustrated substrate container system 200 includes a control system, which includes a microprocessor 250 connected to the sensors and flow control devices of the system 200. Referring to Figure 4A, the microprocessor 250 is connected to both flow control devices 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 in the container atmosphere contained within the interior 206. The process control systems of the exemplary substrate container systems 200 in Figures 4B and 4C are equivalent except that: the control system in Figure 4B further communicates with a temperature control device 232, and the control system in Figure 4C communicates with the temperature control device 232 but only with a single flow meter 224.

[0069] Each example process control system can measure the conditions of the container atmosphere and determine the density value of the container atmosphere (by any useful method or approximation), and based on the density value, deliver a purge gas or purge gas mixture to the interior 206 having a density approximating the density value of the container atmosphere, and the exemplary system controls the density of the purge gas by controlling the composition of the purge gas mixture (Figure 4A), by controlling the temperature of a single type of purge gas (Figure 4C), or by controlling both the temperature and composition of the purge gas mixture (Figure 4B).

[0070] During use, the container 202 of each example holds a substrate 204 for transporting the substrate. While the substrate 204 is placed inside 206, the atmosphere inside 206 is the atmosphere of the substrate and container environment, which is typically a cleanroom atmosphere. The substrate 204 may have moisture on its surface (e.g., adsorbed moisture), and this moisture becomes moisture in the container atmosphere. When the container is opened, the container atmosphere may have any relative humidity above 2 percent (at room temperature, e.g., 22°C), e.g., somewhere between 5 and 100 percent (at room temperature, e.g., 22°C), typically 40 to 50 percent relative humidity. To remove the moist air from the container atmosphere, the inside of the container is purged with a dry purge gas.

[0071] Referring to Figure 5A, the system 200 in Figure 4B is shown to have a container atmosphere 240 (shaded) filling the internal space 206, which includes an upper portion or top 206a and a lower portion or bottom 206b. Figure 5B shows the step of delivering a purge gas mixture 246 (lightly shaded), prepared by combining two different sources of purge gas, e.g., a source of clean, dry air 220b and a source of nitrogen 220a, into the interior 206 via the inlet 210.

[0072] In Figure 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), 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, the 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 Figure 4C), or by controlling only the composition of the purge gas (see Figure 4A).

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

[0074] The exemplary systems and methods may also be useful for performing a container purging step while the doors 118 and 122 are in the open position, the front opening of the container is not covered, and it is possible to remove wafers from the interior 106, as shown in Figures 6A, 6B, and 6C.

[0075] Referring to Figure 6A, the conventional system 100 is shown to have a container atmosphere 140 (shaded) of moist air filling the internal space, including the upper portion or top 106a and the lower portion or bottom 106b. In Figure 6A, the FOUP door 118 and the 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 inside.

[0076] Figure 6B shows the step of delivering 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 through the uncovered front opening (see arrow). The clean, dry air (darkly shaded) 142, which does not contain moisture, has a higher density than the humid air of 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 clean, dry air 142 through the upper portion 106a, slowing down the replacement of the container atmosphere 140 by the clean, dry air 142 in the upper portion 106a.

[0077] Figure 6C shows a different example of an inefficient purging step using nitrogen gas 144. Referring again to Figure 6A, the conventional system 100 is shown to have a container atmosphere 140 (shaded) of moist air filling the internal space, including the upper portion or top 106a and the lower portion or bottom 106b. Figure 6C shows the step of delivering nitrogen gas 144 from the nitrogen gas source 120 through the inlet 110 into the interior 106. The nitrogen gas 144 flows through the interior 106 and exits the interior 106 through the uncovered front opening (see arrow). The nitrogen gas 144 has a lower density than 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 106b, slowing down the replacement of the container atmosphere 140 with nitrogen gas 144 at the bottom 106b.

[0078] Referring to Figure 7A, the system 200 is shown to have a container atmosphere 240 (shaded) of moist air filling the internal space 206, which includes an upper portion or top 206a and a lower portion or bottom 206b. Figure 7B shows the step of delivering a purge gas mixture 246 (lightly shaded), prepared by combining two different sources of purge gas, e.g., a source of clean, dry air 220b and a source of nitrogen 220a, into the interior 206 via the inlet 210.

[0079] In Figure 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), 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, the 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 Figure 4C), or by controlling only the composition of the purge gas (see Figure 4A).

[0080] Pattern:

[0081] Embodiment 1. A method for purging a substrate container with a purge gas, wherein the substrate container is The container body including the opening, A door fitted to cover the opening, The interior defined by the container body, A substrate supported inside, The atmosphere inside the container, One or more purge gas inlets inside and Equipped with, and the method, Distributing purge gas into the interior through one or more inlets, the purge gas is Clean dry air received from a source of clean dry air, and Nitrogen gas received from the nitrogen gas supply source including Methods that include...

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

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

[0084] Embodiment 4. Combining clean dry air and nitrogen gas to produce a purge gas mixture having a gas mixture density, Distributing the purge gas mixture through the inlet, Controlling the density of the purge gas mixture to approximate the density of the container atmosphere and The method according to any one of embodiments 1 to 3, including the method described above.

[0085] Embodiment 5. The purge gas mixture is Clean, dry air with a concentration of 50-97 mole percent, 3-50 mole percent nitrogen gas and The method according to embodiment 4, including the method described in embodiment 4.

[0086] Embodiment 6. The purge gas mixture is Approximately 78.5 mole percent to 98.5 mole percent nitrogen, Approximately 20.5 mole percent to 0.5 mole percent of oxygen and The method according to embodiment 4, including the method described in embodiment 4.

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

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

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

[0090] Embodiment 10. The method according to 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 according to any one of Embodiments 1 to 10, wherein the door is removed and the opening is not covered.

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

[0093] Embodiment 13. A method for purging a substrate container with a purge gas, wherein the substrate container is The container body including the opening, A door fitted to cover the opening, The interior defined by the container body, A substrate supported inside, The atmosphere inside the container, The purge gas inlet located inside, Sources of purge gas and Equipped with, and the method, Measuring the relative humidity of the container atmosphere, Controlling the density of the purge gas based on the relative humidity of the container atmosphere, Distributing purge gas into the interior through the inlet Includes, method.

[0094] Embodiment 14. The source of the purge gas is A source of clean, dry air, Sources of nitrogen gas and The purge gas contains, The flow of clean, dry air received from a source of clean, dry air, The flow of nitrogen gas received from the nitrogen gas supply source and It contains a purge gas mixture containing and The method according to embodiment 13, wherein the method includes 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 according to 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 according to Embodiment 13, wherein the purge gas consists of clean dry air, and the method includes controlling the density of the clean dry air by controlling the temperature of the clean dry air.

[0097] Embodiment 17. The method according to Embodiment 13, wherein the purge gas is nitrogen gas, and the method includes controlling the density of the nitrogen gas by controlling the temperature of the nitrogen gas.

[0098] Embodiment 18. The method according to 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 according to any one of Embodiments 13 to 18, comprising controlling the purge gas density to within 10 percent of the container atmosphere density.

[0100] Embodiment 20. The method according to any one of Embodiments 13 to 19, wherein when the purge gas is distributed internally, the purge gas has a density in the range of 1.15 to 1.21 kilograms per cubic meter.

[0101] Embodiment 21. Measuring the humidity, pressure, and temperature of the container atmosphere, The density of the purge gas is controlled based on the relative humidity, pressure, and temperature of the container atmosphere. The method according to any one of embodiments 13 to 20, including the method described above.

[0102] Embodiment 22. The method according to any one of Embodiments 13 to 21, wherein the door is removed and the opening is not covered.

[0103] Embodiment 23. The method according to any one of Embodiments 13 to 21, wherein the door is removed and the opening is not covered.

[0104] Embodiment 24. A container body including an opening, A door adapted to be positioned above an opening and to be removed from the opening, The interior defined by the container body, A substrate supported inside, The atmosphere inside the container, The purge gas inlet located inside, A source of clean, dry air, and Nitrogen gas supply source A source of purge gas containing, A purge gas flow control system that combines a flow of clean, dry air and a flow of nitrogen gas to generate a purge gas mixture. A substrate container system equipped with the following features.

[0105] Embodiment 25. The control system, A first flow meter controls the flow of clean, dry air to the purge gas inlet, A second flow meter controls the flow of nitrogen gas to the purge gas inlet. A substrate container system according to embodiment 24, comprising the above.

[0106] Embodiment 26. The substrate container system according to Embodiment 24 or 25, further comprising a temperature control device for controlling the temperature of the purge gas.

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

[0108] Embodiment 28. A substrate container system according to any one of Embodiments 24 to 27, comprising a relative humidity sensor, wherein a 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] Embodiment 29. A container body including an opening, A door adapted to be positioned above an opening and to be removed from the opening, The interior defined by the container body, A purge gas inlet connected to the inside, Relative humidity sensor and Source of purge gas, A control system that controls the density of the purge gas distributed inside through the purge gas inlet. A substrate container system equipped with the following features.

[0110] Embodiment 30. The substrate container according to Embodiment 29, wherein the control system includes a mechanical orifice in the flow of purge gas, and the temperature of the purge gas decreases as the purge gas flows through the mechanical orifice.

[0111] Embodiment 31. The source of the purge gas is A source of clean, dry air, Sources of nitrogen gas and including and control system, A flow meter that controls the flow of clean, dry air to the purge gas inlet, A flow meter that controls the flow of nitrogen to the purge gas inlet and A substrate container according to embodiment 27 or 28, comprising the above.

[0112] Embodiment 32. The substrate container according to Embodiment 30 or 31, wherein the purge gas supply source is a supply source of clean dry air, and the control system includes a temperature control device for controlling the temperature of the clean dry air.

[0113] Embodiment 33. The substrate container according to Embodiment 30 or 31, wherein the purge gas supply source is a nitrogen gas supply source, and the control system includes a temperature control device for controlling the temperature of the nitrogen gas.

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

[0115] Embodiment 35. The purge gas mixture is Clean, dry air with a concentration of 50-97 mole percent, 3-50 mole percent nitrogen gas and The method according to embodiment 34, including the method described in embodiment 34.

[0116] Embodiment 36. The method according to 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 according to any one of embodiments 34 to 36, wherein the door is removed and the opening is not covered.

[0118] Embodiment 38. The method according to any one of embodiments 34 to 36, wherein the door is removed and the opening is not covered.

Claims

1. The container body including the opening, A door adapted to be positioned above the opening and to be removable from the opening, The interior defined by the container body, The substrate supported within the above interior, The container atmosphere inside the aforementioned interior, The purge gas inlet located inside the aforementioned interior, A source of clean, dry air, and Nitrogen gas supply source A source of purge gas containing, A purge gas flow control system that generates a purge gas mixture by combining the flow of clean, dry air and the flow of nitrogen gas. A substrate container system comprising the purge gas flow control system, wherein the purge gas mixture density is controlled to approximate the density of the container atmosphere.

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

3. The substrate container system includes a temperature control device for controlling the temperature of the purge gas, or The substrate container system includes a mechanical orifice as a temperature control device for controlling the temperature of the purge gas. The substrate container system according to claim 1.

4. Equipped with a relative humidity sensor, The substrate container system according to any one of claims 1 to 3, wherein the purge gas flow control system selects the flow rate of the clean dry air, the flow rate of the nitrogen gas, or the flow rates of the clean dry air and the nitrogen gas based on the measured relative humidity of the container atmosphere.

5. A method for purging a substrate container with a purge gas, wherein the substrate container is The container body including the opening, A door fitted to cover the aforementioned opening, The interior defined by the container body, The substrate supported within the above interior, The container atmosphere inside the aforementioned interior, One or more purge gas inlets located inside the aforementioned The method comprises, Through one or more of the aforementioned purge gas inlets, into the interior, Clean dry air received from a source of clean dry air, and Nitrogen gas received from the nitrogen gas supply source Distributing a purge gas containing, The clean, dry air and the nitrogen gas are combined to produce a purge gas mixture having a purge gas mixture density, Distributing the purge gas mixture through one or more purge gas inlets, Controlling the density of the purge gas mixture to approximate the density of the container atmosphere. Methods that include...

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