JP2002282712A - Purging vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such weak points of the conventional method for purging the contents of a vessel such as a glove box that a large quantity of the gas to be purged is consumed, it takes a long time and it costs too much to purge the contents and the operation is complicated. SOLUTION: Substance-permeable screens are arranged on both or one of the side faces of the upstream and downstream ends of a purge gas stream in the glove box or the other vessels. A purge gas introducing port is arranged in a wafer conveying/storing vessel for supplying the purge gas. As a result, the floating particulates or gaseous molecules in the vessel can be purged in a short time while the consumption of the purge gas is restrained. High- performance purge gas environment can be created without using the expensive evacuating glove box whose operation is complicated. Clean environment far cleaner than the conventional super clean environment can be created though the screen-arranged vessel is inexpensive and the product yield can be enhanced extremely at the step to manufacture a semiconductor device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for isolating a human body from a product or a substance to be worked on, such as harmful gas molecules, harmful suspended fine particles, harmful microorganisms, deleterious substances, and genetic manipulation, from the viewpoint of avoiding harmful effects on the human body. Related to the technical field of utilizing. Further, the present invention, on the contrary, relates to a technical field related to work in which the atmosphere or the human body has a bad influence on a work target and a general isolation technology thereof. As a specific representative example, the present invention relates to a method and an apparatus for manufacturing industrial products such as elements and precision instruments typified by semiconductor devices and the like which require cleaning, and a cleaning technique. Further, a technology for manufacturing a lithium battery in which oxygen in the atmosphere affects the operation is one of the related technical fields. Further, the present invention relates to an environmental control technology, an ecology-related technology, an energy saving technology, and a cost reduction technology, which are expected to be developed in the future, since the present invention is a basic technology for purging efficiently. Industrial fields related to the present invention include a semiconductor industry field, a precision machine field, a chemical industry field, a medical field, a biotechnology field, a nanotechnology field, an aerospace field, and a food production field. Specific examples of industrial products include glove boxes that allow human hands and arms to operate in containers, containers for transporting or storing wafers in the semiconductor industry (hereinafter, wafer transport / storage containers). Abbreviated) and other closed containers are typical examples.
They relate to the present invention. As described above, the present invention is a basic technology relating to product manufacture in all industries and general advanced technology.

[0002]

2. Description of the Related Art Laminar flow is generated by supplying gas through a material-permeable screen, such as a plate or a sheet of cloth made of a porous material, and making the pressure uniform over the entire supply surface. A mechanism for causing this has existed conventionally. Specifically, there is such a technique in a method of supplying clean air from the ceiling in a clean room. Examples thereof are proposed in Japanese Patent Application Laid-Open No. 62-288433 and Japanese Patent Application Laid-Open No. Hei 8-23426 which is an improved patent thereof. Ordinary clean rooms that do not use such ingenuity, such as class
3 In the high-performance clean room of about (ISO standard, corresponds to the case where particles larger than 0.1micron is 1E3 cells / m ^3), usually,
The ULPA filter and its outlet are located almost entirely on the ceiling except for the fluorescent light installation. As described above, the laminar flow method is already in practical use. The merit of spreading the screen is that the number of ULPA filters can be reduced and the construction cost can be reduced. A chemical filter is also provided. Chemical filters need to be changed once every few months,
The effect of reducing the number of installations is not so significant. As described above, in a large clean room ordinary clean room, the introduction of a screen for generating a laminar flow system was not so significant.

[0003] On the other hand, in a local environment such as in a container, the use of laminar flow has been extremely limited. Because of the extremely small volume, it has been believed that the gas replacement can be easily performed, and the completeness of the gas replacement in the container, that is, the residual concentration of the purge of the unnecessary gas and the unnecessary particles is not much. No stringent requirements.

[0004] However, as environmental problems become more serious, it is necessary to distinguish and isolate the environment necessary for manufacturing from the environment that is friendly to the human body. One specific technical trend is that the demand for reduction of construction and operation costs at semiconductor factories has become more stringent. Due to this change in situation, the movement to introduce local clean technology in factories has become a reality. Also, in advanced fields such as nanotechnology, the potential needs to locally create an environment are increasing. Considering these trends, in a local environment, especially in a small container where the human body cannot enter, such as a small container, a special environment such as a high-purity gas atmosphere or a super clean environment is immediately formed. The technology to be retained will be an essential fundamental technical element in the future.

[0005] Here, the current method of purging the inside of the container can be roughly classified into a method by gas purging and a method by gas purging.
There is a method by evacuation. The gas purging is characterized in that the unnecessary particles and gas in the container are removed only by introducing another gas, so that the structure is simple and low-cost, and the purging operation is simple. However, in order to completely purge unnecessary particles and gas in the container, it is necessary to continuously introduce a large amount of purge gas over a long period of time, which has a disadvantage that it is not very efficient. A method to compensate for this is the vacuum purge method. In this method, since the inside of the container is once evacuated to a vacuum, there is an advantage that the required volume of the gas filling the inside of the container after that is the same as the volume in the container. However, in order to withstand vacuum evacuation, it is necessary to have a container strength that can withstand atmospheric pressure, and it cannot be used in applications that cannot be evacuated to vacuum.
In addition, an exhaust system for evacuation is also required, which has the disadvantage of high cost and complicated operation. further,
Since the evacuation itself takes time, the purging cannot be performed in such a short time.

[0006] As a method for reducing the above problem, there is a method of devising a purge. However, in general, when purging the inside of a container in various types of containers in general, there is almost no technique for devising such a purging method itself. The only exception is the purging technique in a glove box, which keeps the interior handling the radiation powder at a negative pressure. In this technical example, a patent having a structure devised to adjust the flow of a gas flow in a certain direction has been proposed (Japanese Patent Laid-Open No. 6-347592). One of the features is that forced exhaust by pump or fan is required to maintain negative pressure. In addition, as an application thereof, a porous plate is disposed on the inlet side and the outlet side of the purge gas so as not to hinder the gravitational drop of the powder generated in the apparatus, and the gas flow in the apparatus is vertically laminarized. A patent on the structure has been filed (Japanese Patent Laid-Open No. 9-16
8993). However, in Japanese Patent Application Laid-Open No. 9-168993, since the influence of gravity is a dominant factor,
It is necessary to have a structure in which gas flows vertically, and
In this method, since a powder subject to the influence of gravity is a target, almost no advantage can be found from a physical point of view how efficiently the purge time can be reduced by the laminar flow. Laminar flow generation in this technology is disclosed in
It is mainly used for removing powder accumulated in the corners of a container as described in the specification. Further, a gas line is required to blow off and remove the powder accumulated below the porous plate. Due to the turbulence and pressure caused by the powder blowing gas at the bottom of this porous plate,
Smooth gas discharge from the working chamber to the lower porous plate is hindered, and as a result, there is a disadvantage that it is difficult to maintain a laminar flow in the working chamber.

[0007] As described above, although there is a problem, an efficient purging technique has been proposed for powder, but is there any possibility that the purging of fine particles and gas molecules is not affected by gravity? Since it is so small that it can be neglected, it is worthwhile to consider a purging method and a container structure utilizing such characteristics, but no technical proposal has been made so far.

[0008] The prior art relating to the purging has been described above. As an individual application example, a technique relating to a semiconductor wafer transport / storage container will be described below. Conventionally, until around 1997, semiconductor devices have been manufactured in a simple clean room. In order to improve the normal operation rate in terms of the number of product chips, that is, the yield, most device chips have been manufactured in a very clean room of a class 3-5, which is called a super clean room. However, recently, the increase in factory construction cost and operation / maintenance / chip manufacturing cost has exceeded the burden imposed on the manufacturing company, and it has become essential to reduce various costs related to manufacturing. As the most effective means of reducing costs and improving yield, local cleaning technology is being introduced. Specifically, for 200 mm wafers, a wafer transport container named SMIF (Standard Mechanical Interface) is used, and the results are increasing.
For 300mm wafers, which appeared last year since 2000, the specifications have been almost standardized so that containers called FOUPs (Front Opening Unified Pods) can be used.

Unfortunately, however, these wafer transfer containers have only been developed and are technically immature, and cannot completely prevent particles from the outside and particles generated during transfer. Moreover, all commercially available FOUPs are equipped with a pressure relief port, and have no sealing function for gas. Without this, a pressure difference between the inside and outside of the container occurs when the lid is opened and closed, causing a vortex of gas to be generated, and a lot of particles are generated. In the case of SMIF, no special sealing structure is applied to the container itself, and it cannot be said that the container is a completely protective container for particles. Therefore, as long as such a container is used, there is naturally a limit to intentionally lowering the cleanliness (performance) of the clean room.

[0010]

As described above, the conventional in-vessel purging method has drawbacks such as large consumption of purge gas, long purging time, high cost, and complicated operation. The problem to be solved by the present invention is inefficient purging in a container, specifically, a problem of a purge time that takes a long time in principle, a problem of a large consumption of purge gas, and a complicated operation. An object of the present invention is to solve the problem of purging and the problem of purging that requires an exhaust system. Also, in particular,
The task is to solve the inefficient purge problem for suspended particulates and gas molecules that are not affected by gravity or are negligible.

[0011] Further, with respect to the semiconductor wafer transfer / storage container, from the viewpoint of reducing the cost of the clean room and improving the yield, the wafer container is required to have more complete protection performance against generation of particles and gas.

[0012] Further, in the glove box application, there is a problem in that the usual purge type requires a long purge time and a large amount of purge gas is consumed. Further, a vacuum-exhaust type glove box has been used in applications requiring higher performance purging performance, that is, high-speed gas replacement and low concentration of residual gas after the replacement. In this case, a vacuum device is required, and there is a problem that operation and structure are complicated and manufacturing cost is high, and further, there is a problem that it cannot be used in an application that cannot be evacuated to a vacuum. These problems are also problems that the present invention seeks to solve.

[0013]

As a means for solving the problems, a material-permeable sheet or plate screen is arranged on two opposing sides in the container. Thereby, a uniform flow rate independent of the location in the container is obtained, and as a result, the purging is performed with high efficiency. A necessary function of the screen is that the substance is transmitted through the entire effective area of the screen. Any screen structure may be used as long as it satisfies this. Examples include membranes, fibrous cloths, plates with countless holes, sponges having a spongy structure, and sintered bodies.

Further, by providing the above-mentioned screen for the semiconductor wafer transport / storage container, it is possible to make it difficult for particles to adhere to the wafer. Further, a gas supply connector is provided so that a purge gas for performing such a purge is supplied from a counterpart such as a manufacturing apparatus to which the container is connected.

[0015] Furthermore, in glove box applications, the provision of the screen promotes laminar flow,
A significant reduction in purge time and purge gas consumption is achieved.

[0016] In the present invention, in regard to suspended particulates and gas molecules in which the influence of gravity can be neglected, the adverse effect of their remaining accumulation further downstream of the downstream screen can be neglected. No need.

[0017]

[Function] Unlike large particles, such as powders, which are strongly affected by gravity, suspended particles or gas molecules that are not affected by gravity or can be ignored are very easily mixed with other gas molecules. . Therefore, it is extremely difficult to discharge the gas during the gas purge in the container.

[0018] When the size of the container volume is V [liter],
Assuming that the inflow purge gas amount per unit time is S [liter / min], it means that the gas of exactly the volume is introduced at time t when V = St (t is time [min]). At this time, if the introduced purge gas is in a state of being completely mixed at the molecular level with the suspended particulates and gas molecules at the beginning, at time t when V = St, particles and contaminant gas molecules are
Assuming that the initial contaminant concentration is N ₀ , the concentration is reduced to N / 2. When the state of this ideal mixing is represented by an equation, N is a concentration,

(Equation 1) Becomes (1) According to the formula, for example, when performing a purge corresponding to 10 times replacement, suspended particulates and gas molecule concentration is being reduced to N = N _0/1024, 10V purge gas [lit
er] consumes and requires time t = 10V / S [min]. Against 20 times replacement time can be reduced to N = N _0/10 ^6, consumption purge gas there is a 20V [liter], t = 20V / S [m
in] time.

On the other hand, when the complete mixing at the molecular level is not performed, the effect of being swept away by the flow of the purge gas flow appears, so that the gas is exhausted in a shorter time, and the exhaust of the suspended particulates and gas molecules is performed. Is much faster than N / 2. in this case,

(Equation 2) Becomes Here, Ns is included in the purge gas itself,
This is the sum of the concentration of residual suspended particulates and gas molecules leaking from the outside of the container. C is a constant representing the degree of mixing related to the size of the fine particles, where 0 <C <1. In the case of ideal mixing, C = 1. Since Ns appears as a saturation value when the first term on the right side becomes considerably small, the main behavior of the purge is determined by the first term on the right side. C in equation (2)
Is less than 1, in principle, the maximum time is required in the case of the ideal mixing (1) for suspended particulates and gas molecules. Figure 1 shows this trend.

[0020] Further, in the case of particles which are much larger and the influence of gravity becomes dominant, the particles tend to remain in the container due to the influence of gravity, and the behaviors of equations (1) and (2) no longer hold. As shown in FIG. 1, the attained particle concentration tends to be saturated. In such a particle exhaust, the flushing force becomes more important than the total amount of the purge gas, and the purge flow rate S itself is one of the controlling factors for the exhaust time. For particles that are not affected by gravity,
The lighter the light, the more the mixing progresses and the more difficult it is to exhaust. However, particles dominated by the influence of gravity have the opposite property that the heavier the light, the harder it is to exhaust. FIG. 2 shows the relationship between the total amount St [liter] of the purge gas required for the purge target to reach a predetermined residual concentration and the purge speed S [liter / min]. In the case of the non-ideal mixed purge, it can be seen that as the particle size increases, the total purge gas consumption decreases and efficient purging is performed.However, when the particles become larger and become affected by gravity, When the flow rate of the purge gas is low, there is a tendency that the gas is not exhausted.

Now, consider the case where the laminarization purge is introduced into a closed vessel. In this case, ideally, if the same purge gas as the internal volume of the container is introduced, all the gases are exchanged, so that the residual amount of the suspended particulates and gas molecules drops at once to the saturation value Ns, and is saturated there. Ns is the initial value
If N has a concentration of 10 ^-6 with respect to N ₀ , gas of 20 V is consumed in the equation (1), whereas in the case of laminarization purging, only V is required. 1/20 will be enough. FIG. 2 shows the effect of the laminarization purge. Since the introduction of V is sufficient, the purge time is also greatly reduced. This is shown in FIG.

By the way, even when laminarization is completely performed, some gas mixing occurs near the boundary between the tip of the introduced purge gas and the gas already containing suspended particulates and gas molecules. Requires slightly more gas volume and purge time than V. However, it is a minor effect in principle. The relationship between the elapsed purge time due to laminarization and the concentration is as shown in FIG.

In the case of particles in which the influence of gravity is dominant, the effect of laminarization can hardly be expected as shown in FIGS. 1 and 2, or conversely, the particles adhering to the wall due to turbulent flow Because the effect cannot be expected, the factor of the adverse effect cannot be ignored from the viewpoint of the ultimate residual concentration. For such particles, a large area of the outlet is the main effect of improving the efficiency.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows the structure of a closed container used to demonstrate the present invention. A material-permeable screen is provided on each of the upstream side surface and the downstream side surface of the purge gas flow in the container. The purge gas is supplied to the inlet 6
Introduced into the container and passed through the upstream screen 5,
It is led to the work / storage space 2. Then the purge gas is
The gas passes through the downstream screen 4 and is discharged from the purge gas discharge port 7. Arrows indicate the gas flow. In the work / storage space 2, the purge gas flows in a laminar flow due to the action of the upstream and downstream screens 5, 4.

[0025] The state of reduction of suspended fine particles (airborne particles in English) usually called particles by the purge gas was measured. FIG. 4 shows the change over time. Before starting the measurement, the lid 3 is opened, and external particles are drawn into the container. The time on the horizontal axis is the time measured from when the lid is closed. The particle change in the case where the screens 4 and 5 are not used is an actually measured value indicated by “(turbulence)” in the drawing. The data of 0.1, 0.2, and 0.3 micron are values obtained by measuring the amount of particles for particles having a larger particle diameter, respectively. The ideal mixing formula (1) is also shown. It can be seen that as the particle size increases, the amount of particles decreases faster than in the ideal mixing method. This tendency is the same result as the conceptual diagram of FIG.

When the screens 4 and 5 are mounted, the screen shown in FIG.
As shown by the data described as 1 micron (laminar flow),
Particles are quickly purged. The internal volume of the container used for this measurement was about 100 liters, and the nitrogen purge rate was 30
Because it is liter / min, it takes about 3 minutes and 1 volume (1V)
Although the purge gas is being consumed, actual data shows that the purge is slightly slower, with a four-digit reduction in purge. In the turbulence method using no screen, it takes about 40 minutes to obtain a four-digit reduction amount. Therefore, it is demonstrated that the turbulence method has a purging capability as high as one digit. Such high-speed performance is equal to or higher than that of the vacuum evacuation and the subsequent gas introduction system.

In the present embodiment, no particles were measured after being left for one hour. This is far better than the current highest performance super clean room class 3 of a semiconductor factory. In more detailed measurements, it was demonstrated that the structure according to the present invention can easily construct a surprising environment of class 1 or less, that is, 1/100 or less of a super clean room.

Next, FIG. 5 shows an embodiment in which a laminar flow method is applied to a wafer transfer / storage container. In the structure shown, the screen is arranged only on the inner surface of the container. Since the transfer container is used, the purge gas is supplied from the manufacturing apparatus connected to the wafer transfer / storage container 31 via the detachable connector 36. When the connector is separated from the counterpart connector on the manufacturing apparatus side, the inside of the connector is contaminated with the surroundings, so that a filter 35 is provided between the purge gas inlet 34 and the connector 36 so that the partially contaminated gas does not enter the container. Has been inserted.

When the container is connected to the manufacturing apparatus, the connector 36 is connected to the mating connector at the same time or at the same time, so that purge gas can be introduced. Immediately before the container lid (not abbreviated and not shown in FIG. 5) is taken into the manufacturing apparatus and the container is opened, a purge gas is introduced. Thereby, particles and unnecessary gas generated in connection with opening and closing of the lid of the container are exhausted into the apparatus without entering the container.

As described above, although the very simple structure of the purge gas introduction port and the laminar flow generation screen is simply added to the ordinary container, the conventional wafer transfer / storage container described above is used. The present invention is extremely patentable because the disadvantages can be overcome at once.

FIG. 6 shows an embodiment of the glove box structure.
In this structure, screens are arranged on both left and right sides. The gas flows from the purge gas inlet 60 to the upstream screen 52, the work / storage space 54, and the downstream screen 5.
3 and is discharged from the purge gas discharge port 61. In the working / storage space 54 between the upstream and downstream screens, since the purge gas flows in a laminar flow, unnecessary
Discharge of suspended particulates is performed very efficiently, as shown in FIG. When the screen has deteriorated, in this embodiment, the lid 57 can be opened and replaced with a new one. In the present invention, there is an advantage of simplicity that it is sufficient to simply attach the screen to various commercially available glove boxes.

[0032]

The present invention is effective in many industrial fields in which local cleaning has been considered technically difficult or its usefulness has not been noticed. The reason for this is that the present invention points out and proposes a technical element that can form a local environment quickly while being extremely simple. The present invention will trigger the introduction of local environmental technologies into various fields. This makes it easy to separate the environment required for humans from the environment required for the object to be manufactured in all manufacturing processes. This is an important idea for the future of production technology in general, and it is the direction to be taken.

Two specific application examples of the present invention have been proposed as extremely practical techniques.

First, the ripple effect of the wafer transfer / storage container for semiconductor will be described. In SMIF and FOUP wafer transfer containers actually used in semiconductor factories at present, since there is no gas introduction mechanism from the container side according to the present invention, particles and gases enter the container to some extent. This was the most alarming drawback of the prior art.
In the present invention, such a problem is greatly reduced by the gas flow from the container side. Furthermore, due to the laminar flow towards the device, the effect reduces particle and gas contamination to a negligible level.

More importantly, the pressure relief port, which has been provided to prevent a pressure difference from occurring inside and outside the container,
The present invention obviates the need in principle. This is because the pressure can be controlled via the connector 36.
Thereby, the sealing performance of the lid on the front surface of the container can be ensured, and by solving the two technical problems, a completely sealed container can be actually realized and used. This advantage means overcoming the most important technical challenges for wafer carriers. In addition, it directly means that it is possible to separate the wafer atmosphere environment from the environment for the human body in the clean room for the first time from the viewpoint of the gas environment. According to the present invention, a significant change can be brought about in a production system of a semiconductor chip manufacturing factory. As a result, the cost of constructing and operating a semiconductor chip factory and the cost of a semiconductor manufacturing process can be greatly reduced, and the yield can be greatly improved.

[0036] In the glove box application, the present invention is equivalent to a general-purpose product of a vacuum exhaust type glove box, which has been sold at about 10 times the price of the purge type, and the cost is equal to that of the purge type. Such glove boxes will be widely used. This will make working in local clean environments much more widely used in the future.

[0037] In the nanotechnology / biotechnology field, the local cleaning technology has not been actively used so far. This is because these advanced fields are still at the starting line as an industry. However, when these advanced technology fields are applied to industry in the future, they will be required to control the clean environment and environmental gas because they are essentially microscopic technologies. become. For these new technologies, semiconductor factory manufacturing is clearly unsuitable, and local clean technologies will be used as infrastructure. The present invention provides technical elements that will be essential in the near future.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between purge target particles and a purge elapsed time.

FIG. 2 is a diagram showing a purge gas flow rate dependency of a total purge gas consumption amount.

FIG. 3 is a perspective view showing an example of a laminarization purge container structure.

FIG. 4 is a diagram of Example 1 showing a relationship between purge target particles and a purge elapsed time.

FIG. 5 is a perspective view of a second embodiment showing an example of a wafer transfer / storage container structure.

FIG. 6 is a perspective view of Example 3 showing an example of a glove box structure.

[Explanation of symbols]

 Reference Signs List 1 container 2 work / storage space 3 lid 4 material-permeable downstream screen 5 material-permeable upstream screen 6 purge gas inlet 7 purge gas outlet 8, 10 direction of purge gas flow 9 direction of purge gas flow (laminar flow) 31 container 32 Container front surface 33 Material permeable screen 34 Purge gas inlet 35 Filter 36 Purge gas inlet connector 37 Pipe support plate 38 Wafer 51 Glove box 52 Material permeable upstream screen 53 Material permeable downstream screen 54 Work / storage space 55, 56 Gloves Mounting hole 57 Lid 58, 59 Fastener 60 Purge gas inlet 61 Purge gas outlet

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65G 49/00 B65G 49/00 A F24F 7/06 F24F 7/06 C F-term (Reference) 3C007 AS09 AS24 XJ05 3E070 AA40 AB40 PA01 RA01 RA30 3L058 BD06 BE02 BF03 BG01 BG03 4G057 AA07 5F031 CA02 DA08 NA03 NA04 NA15 NA16

Claims (5)

[Claims] Claims 1. A substance-permeable screen is disposed at an upstream end and / or a downstream end of a flow of suspended particulates or gas molecules in a container to purge the suspended particulates or gas molecules in the container. A purge container characterized by having a mechanism. 2. In a container for transporting and storing wafers, a material-permeable screen is disposed on both or one of the side surfaces of the gas flow at the upstream end and the downstream end, so that suspended particulates or gas in the container are disposed. A purge container having a mechanism for purging molecules. In a container for transporting and storing a wafer, a material-permeable screen is disposed on both or one of the upstream and downstream ends of the gas flow, and a detachable gas supply connector is provided. A purge container having a mechanism for purging suspended particulates or gas molecules in the container by providing a gas supply pipe for gas purging. 4. A container having a glove-fitting hole, in which a material-permeable screen is disposed on one or both sides of a gas upstream end and a downstream end, so that floating particles in the container or A purge container having a mechanism for purging gas molecules. 5. A container having a glove-fitting hole, in which a mechanism in which the direction of a purge gas flow is horizontal is provided, and a side which is an upstream end of the gas flow and another side which is a downstream end thereof. A purging container having a mechanism for purging suspended particulates or gas molecules in the container by disposing a material-permeable screen on both or one of the side surfaces.