Abstract:
An air cabinet for photomask box is disclosed. A plurality of laminates each formed with punching holes are provided in the air cabinet. These laminates are arranged in parallel with the punching holes of the upper one facing the punching holes of the lower one, so that the caused laminar flow improves the cleanliness of the photomask box and ensures the mask inside the box against pollution when air flow through these punching ho

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The prevent invention relates to an air cabinet, and more particularly to an air cabinet for storing photomask boxes. 
         [0003]    2. Description of the Related Art 
         [0004]    In semiconductor fabrication, photomask boxes are used for carrying photomasks to isolate the photomasks from the contact of air and prevent from the fogging effect occurring on the surface of photomasks. Especially under current requirement of SMIF, there is a need to effectively improve the isolation of photomasks inside the photomask box from the air in order to extend the duration of photomasks and further decrease the factory manufacturing cost and improve the product yield. 
         [0005]    It is well known that a photomask box is usually put in an ordinary cabinet or anywhere in the IC manufacturing process; however, this may cause the nitrogen inside the photomask box to become diluted and the effect of isolating air cannot be achieved so that the photomask inside the photomask box contacts air, fogging effect occurs on its surface, and the photomask is unusable and regarded as scrap. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The air cabinet of the prevent invention is applied in semiconductor industry to provide a storing space of low humidity, wherein a laminar flow and circulation of air in the air cabinet are used to maintain the environment for long-term storage of photomask pieces. 
         [0007]    A plurality of laminates formed with punching holes are disposed inside the body of air cabinet of the present invention. The laminates are parallel to each other and a plurality of punching holes are disposed on each of the laminates. The punching holes on the upper laminate and the punching holes on the bottom laminate are vertically opposite to each other to allow the air to pass through. Specifically, the air passing through the vertically opposite punching holes on the laminates results in laminar flow circulating inside and filling the air cabinet. Thus, the isolation of photomask box from the atmosphere can be improved and the objects inside the photomask box can be protected from being polluted. 
         [0008]    In one embodiment of the present invention, the air cabinet further comprises an ULPA filtering unit which includes a fan and an ULPA filtering screen for filtering larger molecules in the air to further improve the cleanliness inside the air cabinet. In another embodiment, the air cabinet of the present invention comprises not only an ULPA filtering unit but also a chemical filter for removing the chemical substances mixed in the air to improve the isolation of photomask box from the atmosphere and prevent objects inside the photomask box from being polluted. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic diagram showing an air cabinet for photomask box according to the first embodiment of the invention. 
           [0010]      FIG. 2  is a schematic diagram showing the composition of the control unit of the air cabinet for photomask box according to the first embodiment of the invention. 
           [0011]      FIG. 3  is a schematic diagram showing the laminates with punching holes placed inside the air cabinet for photomask box according to the first embodiment of the invention. 
           [0012]      FIG. 4  is a schematic diagram showing an air cabinet for photomask box according to the second embodiment of the invention. 
           [0013]      FIG. 5  is a schematic diagram showing the composition of the control unit of the air cabinet for photomask box according to the second embodiment of the invention. 
           [0014]      FIG. 6  is a schematic diagram showing the laminates with punching holes placed inside the air cabinet for photomask box according to the second embodiment of the invention. 
           [0015]      FIG. 7  is a schematic diagram showing an air cabinet for photomask box according to the third embodiment of the invention. 
           [0016]      FIG. 8  is a schematic diagram showing the laminates with punching holes placed inside the air cabinet for photomask box according to the third embodiment of the invention. 
           [0017]      FIG. 9  is a schematic diagram showing the bottom laminate and the punching holes thereof of the air cabinet for photomask box according to the third embodiment of the invention. 
           [0018]      FIG. 10  is a schematic diagram showing an ULPA filtering screen of the air cabinet for photomask box according to the second and the third embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring to  FIGS. 1 ,  4  and  7 , the air cabinet for storing photomask boxes according to various embodiments of the present invention used in semiconductor industry is disclosed. 
         [0020]    Referring to  FIGS. 1 ,  2  and  3 , the air cabinet  1  for storing photomask boxes according to first embodiment of the present invention includes an air cabinet body  10 , a pressure gage  11 , a control unit  12 , a plurality of laminates  14  each formed with punching holes and an air exhausting valve  19 , wherein the control unit  12  is mounted on the air cabinet body  10  and the laminates  14  are placed inside the air cabinet body  10 . The control unit  12  includes therein a timer  121 , indicating lamps  122  and  123 , a first buzzer  124 , a second buzzer  125 , an air cabinet power switch  126 , an air extracting button  127  and a flowmeter  128  such as an electronic flowmeter. 
         [0021]    The control unit  12  is used to control the flow and the entrance of the air in the air cabinet body. In the present embodiment, when the air cabinet power switch  126  in the control unit  12  is switched ON, the indicating lamp  122 , a green lamp for example, lights to show that an inflow is in action. The flowmeter knob  1281  is adjustable that the float inside the flowmeter  128  can reach a required position. The air exhausting valve  19  below the air cabinet body  10  is in charge of exhausting the surplus air when the pressure gage  11  shows that the pressure inside the air cabinet body  10  is overloaded. The first buzzer  124  rings and the counting of the timer  121  starts when the air extracting button  127  is pressed. Afterward, the indicating lamp  122  lights and the air starts to flow into the cabinet after the 15-second assurance that the door of the cabinet is closed. In addition, every time when the door of the cabinet is going to be opened, the user must press the air extracting button  127  first to prevent a lot of air from pouring out to avoid possible damages to human bodies. If the door is not completely closed after it is opened, the second buzzer  125  rings and the indicating lamp  123 , a red lamp for example, lights until the door is closed. 
         [0022]    A plurality of laminates  14  each formed with punching holes  141  are placed inside the air cabinet body  10 . Especially, the laminates  14  are transversely placed inside the air cabinet body  10  and parallel to each other, whereas the punching holes  141  are vertically opposite to each other to allow the air to pass through. Specifically, the air passes through the punching holes  141  and can result in laminar flow circulating inside the air cabinet  10  when air enters the air cabinet body  10 . In one embodiment of the present invention, there can be at least six layers of laminates  14 , each layer with one laminate, or thirty-six punching-hole-plates inside the air cabinet  10  for each laminate  14  being composed of six pieces of punching-hole-plate. 
         [0023]    On the other hand, the air cabinet body  10  includes a plurality of glass windows  13  for observing the placement of the photomask box (not shown) inside the air cabinet body  10 . In addition, there are adjustable foot anchors  151  and actuating wheel  152  under the air cabinet body  10 , in which the adjustable foot anchors  151  have anti-slip and electrically conductive iron chain for eliminating static electricity of the air cabinet body  10 , and the actuating wheel  152  facilitates the movement of the air cabinet. 
         [0024]    Referring then to  FIGS. 4 ,  5  and  6 , the air cabinet  2  for photomask boxes according to the second embodiment of the present invention includes an air cabinet body  20 , a temperature-hydrometer  21 , a control unit  22 , an ultra low penetration air (ULPA) filtering unit  27 , two air return tubes  28 , an air exhausting valve  29  and a plurality of laminates  24  each formed with punching holes. 
         [0025]    The control unit  22  according to the present embodiment is used to control the flow and the entrance of the air and includes a timer  221 , an indicating lamp  222 , an indicating lamp  223 , a buzzer  224 , an air cabinet power switch  225 , a air extracting button  226  and a flowmeter  228  such as an electronic flowmeter, a pressure gauge, or a hydrometer. The ULPA filtering unit  27  including a fan  271  and an ULPA filtering screen  272  such as shown in  FIG. 10  is mounted above the air cabinet body  20 . The ULPA filtering unit  27  is used to filter and dry the air before the air enters the cabinet body  20  so that the molecule of the air entering air cabinet is less than 0.5 μm in diameter. When a photomask box is stored in this air cabinet, since the laminar flow effect caused by the air fills the air cabinet body with air at any time, the effect of isolating the photomask from the atmosphere can be enhanced. Thus, not only can the photomask box be stored in a dry, airy environment, objects inside the mask can also be protected from pollution. In addition, the present invention does not limit the kind of air filled in the air cabinet. Thus the air can be an inert gas, nitrogen, carbon dioxide, etc. Even air mixed with the above air at certain percentages can also be applied in the present invention. 
         [0026]    The indicating lamp  222 , a green lamp for example, lights when a user turns on the air cabinet power switch  225  to show that an inflow is in action. At the same time, the power switch  273  for the ULPA filtering unit  27  and the tachometer  274  for controlling the speed of the fan  271  can be activated to adjust the air flow into the air cabinet body  20 . The fan  271  draws in the air, which goes through the ULPA filtering screen  272 , and then the dried and uniforms air is emitted. The temperature-hydrometer  21  on the air cabinet is used to monitor the temperature and the humidity inside the air cabinet body and can thus ensure certain low humidity state. When the entering air flow is too much, the user can adjust the flowmeter knob  2281 , a throttle valve for example, to let the float of the flowmeter  228  reach the required position, and the surplus air can be exhausted from the air exhausting valve  29  below the cabinet body  20 . 
         [0027]    A plurality of laminates  24  each formed with punching holes  241  are placed inside the air cabinet body  20 . Especially, each of the laminates  24  is composed of six pieces of punching-hole-plate and is transversely placed inside the air cabinet body  20  and parallel to each other. The punching holes  241  are vertically opposite to each other to allow the air to pass through. In the present embodiment, there can be at least six layers of laminates and two laminates for each layer or seventy-two punching-hole-plates inside the air cabinet  10  for each laminate  24  being composed of six pieces of punching-hole-plate. 
         [0028]    On the other hand, two air return tubes  28  are respectively mounted on two sides (such as left and right sides, or front and back sides, or two adjacent sides) of the air cabinet body  20 . The air passes through the ULPA filtering screen  272 , enters the air cabinet body  20 , passes downward through the punching holes  241  and then passes the air return tubes  28  to form a cycle inside the air cabinet  1 . Furthermore, there are a plurality of reed switches  26  mounted on the inner side of each door of the air cabinet body  20 . The timer  221  starts to count when the cabinet door is opened and the buzzer  224  rings and the indicating lamp  223 , a red lamp for example, lights to show that the cabinet door is in an open state if the cabinet door is opened for a time exceeding a set period, 15 seconds for example. In this way, the open state of the cabinet door of the air cabinet  20  can be monitored to prevent the air from escaping out of the cabinet and affecting the condition of storage. There are also a plurality of electrically conductive glass windows  23  disposed on the air cabinet body  20  for observing the placement of the photomask box inside the cabinet and eliminating the static electricity of the air cabinet body  20 . In addition, there are adjustable foot anchors  251  and actuating wheel  252  disposed under the air cabinet body  20 , wherein the adjustable foot anchors  251  have anti-slip and electrically conductive iron chain for eliminating static electricity of the air cabinet body  20  and the actuating wheel  252  facilitates the movement of the air cabinet  2 . 
         [0029]    Referring to  FIGS. 7 ,  8  and  9 , the air cabinet  3  for photomask boxes according to the third embodiment of the present invention includes an air cabinet body  30 , a control unit  32 , a chemical filter  38 , an ULPA filtering unit  37 , and a plurality of laminates  34  each formed with punching holes. The control unit  32  according to this embodiment not only includes the elements described in the second embodiment such as the timer  221 , the indicating lamp  222 , the indicating lamp  223 , the buzzer  224 , the air cabinet power switch  225 , the air extracting button  226 , and the flowmeter  228  but also integrates the elements such as the tachometer  274  and the power switch  273  of the ULPA filtering unit as shown in the second embodiment. The control unit  32  is used to control the flow and the entrance of the air inside the air cabinet body  30 , and the way of controlling is the same as that described in second embodiment and is omitted here. 
         [0030]    The chemical filter  38  and the ULPA filtering unit  37  are mounted above the air cabinet body  30 . The ULPA filtering unit  37  including a fan  371  and an ULPA filtering screen  372  is the same as that in the second embodiment and is used to filter and dry the air before the air enters the cabinet body  30  so that the molecule of the air entering air cabinet is less than 0.5 μm in diameter. The chemical filter  38  and the ULPA filtering unit  37  are connected to each other via a connector  39  mounted above the head of the ULPA filtering unit  37 . Since there is more or less some chemical particles or moisture in the air and the molecule weight of moisture is smaller than that of air, the chemical filter  38  is in charge of eliminating certain chemical substances in the air or changing the air into air without chemical ingredients and allows dried and uniformed air to be emitted after the air passes through the ULPA filtering screen  372  and decreases the humidity inside the air cabinet body  30  through double filtering. In this way, the effect caused by the air on the goods storing in the cabinet can be reduced due to the removal of the moisture inside the air cabinet body  30  and the decrease of the frequency of collision between the air molecule and the surface of the stored objects. 
         [0031]    A plurality of laminates  34  each formed with punching holes  341  are placed inside the air cabinet body  30 . Especially, the laminates  34  are composed of six pieces of punching-hole-plate and transversely placed inside the air cabinet body  30  and parallel to each other, while the punching holes  341  are vertically opposite to each other to allow the air to pass through. According to this embodiment, there are six layers of laminates including the bottom laminate  34   a  in the air cabinet  3 , two laminates for each layer, and thus there will be twelve laminates with punching holes or seventy-two punching-hole-plates for each laminate  34  or  34   a  is composed of six pieces of punching-hole-plate. The bottom laminate  34   a  in the air cabinet body  30  is also disposed with punching holes  341   a  and the punching holes  341  and the punching holes  341   a  are vertically opposite to each other to allow the outside air to enter the air cabinet body  30  after the air is filtered by the chemical filter  38  and the ULPA filtering unit  37  mounted above the air cabinet body  30 . Therefore, the air passes through the punching holes  341  and  341   a  to produce laminar flow effect inside the air cabinet and fill the air cabinet with air. 
         [0032]    On the other hand, there are a plurality of electrically conductive glass windows  33  on the air cabinet body  30  for observing the inside of the air cabinet  30  and eliminating the static electricity of the air cabinet body  30 . In addition, there are adjustable foot anchors  351  and actuating wheel  352  under the air cabinet body  30 , wherein the adjustable foot anchors  351  have anti-slip and electrically conductive iron chain and the actuating wheel  352  facilitates the movement of the air cabinet. 
         [0033]    As shown in the above, the present invention has been clearly illustrated by different embodiments and related drawings. However, it should be understood by one skilled in the art that the embodiments of the present invention demonstrated here are only exemplary rather than limiting. For instance, in the above embodiments, some pieces are not indicated, but it does not mean that these pieces cannot be applied in other embodiments. For example, the temperature-hydrometer  21 , reed switch  26 , and the air exhausting valve  29  according to the second embodiment can be mounted on the air cabinet according to the third embodiment. For another example, the pressure gage  11  according to the first embodiment can be mounted on the air cabinets according to the second and the third embodiments; and the temperature-hydrometer  21  and the reed switch  26  according to the second embodiment can be mounted on the air cabinet according to the first embodiment. In addition, what is to be emphasized is that, the air used in the air cabinet described in the present invention is not limited to air. Generally speaking, as long as the air is inert gas, such as helium, neon, argon, krypton, xenon, and radon, nitrogen, carbon dioxide, or even air mixed with the above air at certain percentage, it can be applied in the present invention. Accordingly, all such changes and modifications of various elements are encompassed by the present invention without departing from the spirit and scope of the present invention, which is limited only to the appended claims.