Patent Publication Number: US-2009225287-A1

Title: Reticle pod and method for keeping reticle clean and dry

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a reticle pod and a method for keeping a reticle clean and dry with the reticle pod. 
     2. Description of Related Art 
     Recent years see rapid development of semiconductor technology, including photolithography that plays an important role therein, as photolithography is indispensable to patterning. When it comes to semiconductor, photolithography involves fabricating a transparent reticle with a specific shape in accordance with an intended circuit, and projecting a light source through the reticle to form a specific pattern on a silicon wafer by exposure and development. Any dust and particles (such as microparticles, powder, and organic matter) attached to the reticle can deteriorate the quality of imaging, and thus the reticle has to be kept clean when used in patterning. In general, a wafer process is performed in a clean room to prevent contamination by airborne particles. However, clean rooms nowadays are not absolutely free of dust. 
     Hence, contamination-free reticle-holding devices, commonly known as reticle pods, for preserving and delivering reticles are used in a semiconductor process nowadays in order to keep the reticles clean during the semiconductor process. During a semiconductor process, a reticle-holding device (hereinafter referred to as a reticle pod) holds a reticle, allows the reticle to be moved and delivered between machines, insulates the reticle from ambient air, and prevents the reticle from contamination and being changed thereby. Hence, advanced semiconductor foundries usually endeavor to assure the cleanliness of standard mechanical interface (SMIF) reticle pods, that is, the reticle pods should have a Class 1 or sub-Class 1 rating for cleanliness. Hence, a gas-fillable reticle pod is one of the solutions in use. 
     To fill a gas into a reticle pod, the reticle pod must have at least one gas inlet port for connection with a gas-supplying device which supplies the gas to the reticle pod. The present invention provides a reticle pod and a method for keeping a reticle clean and dry, to improve the prior art regarding the position of a gas inlet port of the reticle pod, and regarding a method for introducing a gas into the reticle pod to remove moisture therefrom and carrying contaminated gas away from the reticle pod. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method for keeping a reticle clean and dry and a gas-fillable reticle pod, wherein the reticle pod holds at least one reticle having a pellicle side provided with a frame. The reticle pod comprises: a first cover; a second cover for being assembled with the first cover to form an inner space therebetween for receiving the reticle, wherein the second cover has a central region; at least one fixing element disposed on the second cover for supporting and positioning the reticle; at least one gas inlet port disposed on the second cover and outside a projection region of the reticle; and at least one gas outlet port disposed on the second cover and opposite the gas inlet port with respect to the central region. 
     It is a primary objective of the present invention to provide a reticle pod wherein a gas enters the reticle pod via a gas inlet port thereof and diffuses in a rippling manner. 
     Another objective of the present invention is to provide a reticle pod wherein a gas enters the reticle pod via a gas inlet port thereof and removes moisture between a reticle and a pellicle disposed thereon. 
     Yet another objective of the present invention is to provide a reticle pod, in which a major amount of gas enters the reticle pod via a gas inlet port thereof and flows along a side of a reticle where a pellicle is disposed to substitute for contaminated gas and moisture originating from the pellicle. 
     A further objective of the present invention is to provide a reticle pod, in which once a gas enters the reticle pod via a gas inlet port thereof, a minor amount of the gas will reach a side of the reticle opposite to where a pellicle is disposed to substitute for contaminated gas and moisture originating from the reticle. 
     A further objective of the present invention is to provide a reticle pod having a joint element, in which once a gas enters the reticle pod via a gas inlet port thereof, an excessive amount of the gas exits through a gas outlet port or from between the pressure-releasing joint element and the joint element keeps the reticle pod airtight and dust-free when a pressure inside the reticle pod does not exceed a preset value. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a reticle pod according to the present invention; 
         FIG. 2  is a top view showing a second cover of the reticle pod according to the present invention; 
         FIG. 3  is a side elevation view showing a reticle positioned above the second cover of the reticle pod according to the present invention; 
         FIG. 4  is a schematic view showing a fastening element optionally provided on the reticle pod according to the present invention; 
         FIGS. 5A and 5B  are schematic views showing a first joint element and a second joint element optionally provided on the reticle pod according to the present invention; and 
         FIG. 6  is a schematic view illustrating a method for keeping the cleanliness and dry of the reticle according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention discloses a reticle pod and a method for keeping the cleanliness and dry of a reticle. Processes adapted for manufacturing or processing the reticle or the reticle pod are based on the prior art, and thus a detailed description of the processes is omitted herein. In addition, drawings referred to below are not drawn to scale as they are intended to demonstrate features of the present invention only. 
     Referring to  FIG. 1 , which is a perspective view of a reticle pod  1  according to the present invention, the reticle pod  1  includes a first cover  11  and a second cover  12 , in which the first cover  11  and the second cover  12  are joined to form an inner space therebetween for receiving a reticle. 
     Referring to  FIG. 2 , which is a top view showing the second cover  12  of the reticle pod according to the present invention, the second cover  12  has a central region  121  centrally disposed thereon. At least one fixing element  122  is disposed on the second cover  12  for supporting and positioning the reticle. At least one gas inlet port  21  is disposed on the second cover  12  and outside a projection region  123  of the reticle, so as to allow a gas to enter the reticle pod  1 . At least one gas outlet port  22  is disposed on the second cover  12  and opposite the gas inlet port  21  with respect to the central region  121 , so as to allow the gas to exhaust out of the reticle pod  1 . Referring to  FIG. 3 , which is a side elevation view showing a reticle  3  positioned above the second cover  12  of the reticle pod  1  according to the present invention, the reticle  3  has a pellicle side  31  that provided with a frame  33  that prevent the pellicle side  31  from contamination and being changed thereby, and allowing a gas conversion with the gas filled in the reticle pod  1  to remove moisture and contaminants from the reticle  3 . 
     Referring to  FIG. 4 , at least one fastening element  111  is optionally provided on a side of the first cover  11  facing the inner space so as to support an edge of the reticle  3 . An edge of the fastening element  111  itself extends to above the gas inlet port  21 , not only to guide a major portion of the gas entering the reticle pod  1  via the gas inlet port  21  to flow towards the frame  33  on the pellicle side  31  of the reticle  3  and thereby carry moisture and contaminants away from the reticle pod  1 , but also to guide a minor portion of the gas to flow towards a glass side  32  of the reticle  3  and thereby carry moisture and a contaminated gas away from the reticle pod  1 . 
     Referring to  FIGS. 5A and 5B , a reticle pod  1 ′ is optionally provided with joint elements  41 ,  42  for dust prevention. Likewise, the reticle pod  1 ′ includes a first cover  11 ′ and a second cover  12 ′, in which the first cover  11 ′ and the second cover  12 ′ are being assembled to form an inner space therebetween for receiving a reticle  3 ′. At least one fixing element  122 ′ is disposed on the second cover  12 ′ for supporting and positioning the reticle  3 ′. Most importantly, the first cover  11 ′ and the second cover  12 ′ are circumferentially solid joint to the first joint element  41  and the second joint element  42  respectively. The joint elements  41 ,  42  are made of a resilient material. Or alternatively, a joint portion  43  of the second joint element  42  for solid joint with the first joint element  41  is suspended, so that in the event of excessive pressure inside the inner space of the reticle pod  1 ′ due to an excessive amount of gas therein, the gas will drain out from the middle of the joint elements  41 ,  42  to maintain an appropriate pressure inside the inner space and prevent the reticle  3 ′ from damage. If the pressure inside the inner space of the reticle pod  1 ′ does not exceed a preset value, the joint elements  41 ,  42  will provide airtight solid joint and keep the reticle pod  1 ′ airtight, leak-free, and dust-free. Furthermore, the first cover  11 ′ may be provided with a first plate  51  such that the first joint element  41  is clamped therebetween, as shown in  FIG. 5A , while the second cover  12 ′ may be provided with a second plate  52  such that the second joint element  42  is clamped therebetween, as shown in  FIG. 5A . Alternatively, if necessary, the first joint element  41  may be integrally formed with the first cover  11 ′, as shown in  FIG. 5B , while the second joint element  42  may be integrally formed with the second cover  12 ′, as shown in  FIG. 5B . 
     Referring to  FIG. 6 , which is a schematic view illustrating a method for cleaning and drying a reticle  3  according to the present invention. A pellicle side  31  of the reticle  3  is provided with a frame  33  for preventing the reticle  3  from contamination. The frame  31  absorbed the moisture that is generated from the reticle  3 , and the gas is transformed with a gas inside the reticle pod  1  so as to the moisture and contaminants cane be removed from the reticle  3 . 
     First, a reticle pod  1  is provided, which includes a first cover  11 ; a second cover  12 ; at least one fixing element  122  that is disposed on the second cover  12  for supporting and positioning the reticle  3 ; at least one gas inlet port  21 ; and at least one gas outlet port  22 . The second cover  12  has a central region  121  that centrally disposed thereon. The gas inlet port  21  is disposed on the second cover  12  and outside a projection region of the reticle. The gas outlet port  22  is disposed on the second cover  12  and opposite the gas inlet port  21  with respect to the central region  121 . 
     Then, the reticle  3  is disposed on the fixing element  122  and the pellicle side  31  is provided for the frame  33  of the reticle  3  is disposed toward the second cover  12 . Thus, the first cover  11  is jointed tightly with the second cover  12 , and the gas is flowed into the reticle pod  1  and diffused over the reticle pod  1  via the rippling. Amount of gas is flowed through the pellicle side  31  that is provided for the frame  33  of the reticle  3  to replace the contaminated gas and the gas is exhausted outside from the gas outlet port  22  to remove the dust and the moisture. Otherwise, the gas can be exhausted outside from the gap  13 . Also, the gas would flow through the glass side  32  of reticle  3  without the frame  33  to remove the dust and the moisture. Alternatively, the gas would not flow through the reticle  3 , but is exhausted outside from the gap  13  of the reticle pod  1  directly 
     The above description in intended to illustrate the preferred embodiment of the present invention and did not to limit the scope of the present invention. Moreover, as the content disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent modifications and variations made thereby without departing from the spirit of the present invention should fall within the scope of present invention defined by the appended claims.