Abstract:
A photomask pod and a photomask transport pod are provided for preventing particles in the environment from defiling a photomask as well as charge accumulation on the photomask from causing ESD damage. The photomask pod comprises two covers and the supporters or retainers on at least one of the two covers are made of a static dissipative material, which facilitates reducing charge accumulation and protecting the photomask from ESD damage.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to photomask pods and photomask transport pods and, more particularly, to a photomask pod and a photomask transport pod which can prevent damage caused by ESD. 
         [0003]    2. Description of the Related Art 
         [0004]    In the rapidly developing semiconductor technology, optical lithography plays an important role and wherever pattern definition is conducted, optical lithography is requisite. As to the application of optical lithography relating to semiconductors, a designed circuit pattern is used to produce a light-transparent photomask. Based on the principle of exposure, after a light passes through the photomask to be projected on a silicon wafer, the circuit pattern formed on the photomask can be exposed onto the silicon wafer. Since any dust (such as particles, powders or an organic material) can adversely affect the quality of such projected pattern, the photomask used to produce the pattern on the silicon wafers is required with absolute cleanness. Thus, clean rooms are typically employed in general wafer processes for preventing particles in the air from defiling photomasks and wafers. However, absolute dustless environment is inaccessible even in known clean rooms. Hence, reticle pods that facilitate preventing defilement are implemented in current semiconductor processes for the purpose of storage and transportation of photomasks so as to ensure cleanness of the photomasks. 
         [0005]    Conventional photomask pods are generally made of macromolecular materials, which possess the advantages of easy forming, inexpensiveness and the ability to form transparency. Such macromolecular materials, which are insulating and have high surface resistivity, are liable to induce static due to friction and separation. Especially, in the low-moisture environment of a clean room, photomask pods made of such macromolecular materials are apt to produce and accumulate charges thereon. Additionally, when a photomask is placed in or taken out from a photomask pod, static may easily occur on the surface of the photomask owing to friction. Static on the photomask is attractive to particles in the air and may, even worse, cause electrostatic discharge (ESD) on metal wires of the photomask. Transient currents induced by ESD can bring sparks or arcs that come along with powerful currents and high heat. As such powerful currents and high heat oxidize and melt the metal wires of the photomask, the pattern on the photomask is consequently deformed. 
         [0006]    Many solutions have been introduced to eliminate ESD. The primary solution is to manage the operational environment with proper atmospheric moisture. Clothes having grounding effects for staff and ion fans may be also helpful to eliminate environmental static. However, there are countless factors in the operational environment, and it is actually impossible to completely protect photomasks from being damaged by static. 
         [0007]    An alternative solution is to change the material of the components composing a photomask pod, as disclosed in U.S. Pat. No. 6,513,654, wherein a supporter having a grounding effect is provided so that when the photomask pod contacts a corresponding station, the supporter helps to conduct out charges on the photomask. Furthermore, another solution, provided by U.S. Pat. No. 6,247,599, involves equipping a metal layer on a bottom plate, a cover, or a handle of the photomask pod so as to reduce charge accumulation. While all the aforementioned solutions are dependent on grounded electrically conductive components to release charges, it is to be noted that when static is released by such electrically conductive components, currents are unavoidably generated and discharge can still occur to damage the photomask. 
         [0008]    Therefore, the present invention provides novel supporters or retainers to remedy the above defects of the prior arts. 
       SUMMARY OF THE INVENTION 
       [0009]    To overcome the aforementioned defects of the prior arts, the present invention provides a photomask pod which has supporters or retainers made of a particular material. In the present invention, the supporters or retainers are made of a static dissipative material so that even when charges are generated on the static dissipative material because of friction, an adjacent metal material can instantly conduct out the charges so as to eliminate charge accumulation and ESD. 
         [0010]    It is one objective of the present invention to provide a supporter of a mask, which is made of a static dissipative material to reduce charge accumulation and to protect a photomask from being damaged by static. 
         [0011]    It is another objective of the present invention to provide a supporter of a photomask, which is made of a static dissipative material to continuously conduct out charges so as to protect a photomask from being damaged by high heat resulted from transient discharge. 
         [0012]    It is another objective of the present invention to provide a retainer of photomask, which is made of a static dissipative material to reduce charge accumulation and to protect a photomask from being damaged by static. 
         [0013]    It is another objective of the present invention to provide a retainer of a photomask, which is made of a static dissipative material to continuously conduct out charges so as to protect a photomask from being damaged by high heat resulted from transient discharge. 
         [0014]    The present invention discloses a photomask pod and a photomask transport pod with supporters and retainers which directly contact a photomask and are made of a static dissipative material so as to provide a way for dissipating static. The static dissipative material has a property between conductive and non-conductive. Since the static dissipative material features a slow conductive velocity, discharge is not liable to happen between the supporters or the retainers and the photomask or the photomask pod. Consequently, the photomask can be free from the influence of heat generated by discharge so that the present invention provides superior protection to the photomask while shielding is also presented. As a result, the photomask is protected from the risk of being damaged. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein 
           [0016]      FIG. 1  is a schematic view of a photomask pod; 
           [0017]      FIG. 2  illustrates a supporter and a retainer of the present invention according to one preferred embodiment; 
           [0018]      FIG. 3A  to  FIG. 3D  illustrate a supporter of the present invention according to one preferred embodiment; 
           [0019]      FIG. 4  illustrates the supporter of the present invention; 
           [0020]      FIG. 5A  and  FIG. 5B  illustrate a supporter of the present invention according to another preferred embodiment; 
           [0021]      FIG. 6  illustrates a supporter of the present invention according to another preferable embodiment, and 
           [0022]      FIG. 7  illustrates a supporter and a retainer of the present invention according to another preferred embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0023]    It is to be stated at first that essential components and combining means among the components of the disclosed supporters and retainers made of a static dissipative material in the present invention are well known in the art and need not be discussed at length herein. Meanwhile, the basic structure of photomasks pod and the principle where photomask pods are based on are also well known by those skilled in the art and need not be disclosed in the present invention. Beside, the accompanying drawings are provided for illustration and are not and need not to be drawn in scale. 
         [0024]      FIG. 1  is provided for illustrating a photomask pod or a photomask transport pod. Therein, the photomask pod or photomask transport pod  100  comprises a first cover or a top cover  102  and a second cover or a bottom plate  104 . The first cover or top cover  102  and the second cover or bottom plate  104  can be assembled to enclose an inner space for accommodating a photomask  114  therein. The first cover  102  or the second cover  104  of the photomask pod or photomask transport pod  100  may be made of metal. Alternatively, a metal liner may be additionally equipped in the photomask pod or photomask transport pod  100  to provide the shielding effect so as to insulate an extrinsic interference. The second cover or bottom plate  104  is composed of a body  106 , a conductive panel  108 , a plurality of supporters  112  and a plurality of retainers  110 . The conductive panel  108  is arranged on a surface of the body  106  facing the inner space and is made of a conductive material. The plural retainers  110  and supporters  112  are settled on the conductive panel  108  while the retainers  110  and supporters  112  may be made of different materials or made of an identical material. The supporters  112  are electrically connected to the conductive panel  108  and are made of a static dissipative material having a surface resistivity ranging from about 10 4  to about 10 11 Ω. When the photomask  114  is placed on the supporters  112 , the supporters  112  directly contact the photomask  114 . The static dissipative material helps to continuously conduct out charges so as to protect the photomask from being damaged by high heat resulted from transient discharge. Since the charge accumulation of the photomask is reduced, the photomask is protected from being damaged by static. 
         [0025]      FIG. 2  provides a preferable embodiment of the present invention, showing a plurality of supporters or retainers deposited in a photomask pod. A second cover  104  of the photomask pod  100  comprises of a body  106 , a conductive panel  108 , a photo mask  114 , a plurality of retainers  110  and a plurality of supporters  112 . The first cover  102  or the second cover  104  of the photomask pod  100  may be made of metal. Alternatively, a metal liner may be additionally equipped in the photomask pod or photomask transport pod  100  to provide the shielding effect so as to insulate an extrinsic interference. The conductive panel  108  is settled on the body  106  while the plural retainers  110  or supporters  112  are provided on the conductive panel  108 . Therein, the retainers  110  and supporters  112  are formed by multi-component injection molding and then combined mutually. The supporters  112  are provided as inserting pieces and are made of a static dissipative material having a surface resistivity ranging from about 10 4  to about 10 11 Ω. When being placed in the second cover  104  of the photomask pod  100 , the photomask  114  is supported by a retainer  110  as well as the plural supporters  112  and is retained on the second cover  104  by the retainers  110 . The retainers  110  surrounding the photomask  114  function to reduce possible vibrations occurred in transportation of the photomask pod  100  and for securing the photomask  114  from impact. Hence, the plural retainers  110  and the plural supporters  112  are provided to function collaboratively. 
         [0026]      FIG. 3A  provides another preferred embodiment of the plural supporters in the photomask pod. Therein, a supporter  200  is integrally formed and made of a static dissipative material having a surface resistivity ranging from about 10 4  to about 10 11 Ω. The supporter  200  comprises at least one planar base  202  connecting with a first inclined surface  204  that is further connected with a second inclined surface  206  so that the planar base  202 , the first inclined surface  204  and second inclined surface  206  are formed as the supporter  200  integrally. It is to be stated that the configuration of the first inclined surface  204  and the second inclined surface  206  is not to be limited by the present invention. Therein, the first inclined surface  204  is approximately perpendicular to the planar base  202 . However, the degree of the angle between the first inclined surface  204  and the planar base  202  may vary in alternative embodiments. Another angle is also formed by the second inclined surface  206  and the first inclined surface  204  to provide a surface for smoothly guiding an article to slide on the second inclined surface  206 . Furthermore, two first openings  208  are provided near both lateral sides of the supporter  200 . Each of the first openings  208  is equipped with an upper fastening piece  210  and a lower fastening piece  212 . Thereby, when a photomask  114  is placed in the bottom plate  104  of the photomask transport pod  100  and then the top cover  102  is assembled to the bottom plate  104 , the second inclined surfaces  206  of the supporters  200  helps the photomask  114  to be guided smoothly to a proper position in the photomask transport pod  100  where the photomask  114  can be steadily positioned. Then the upper fastening pieces  210  and the lower fastening pieces  212  help to support and fix the photomask  114 . 
         [0027]    In addition,  FIG. 3A ,  FIGS. 3B ,  3 C and  3 D provide one embodiment of the supporters arranged in the photomask transport pod. The embodiment shown in  FIG. 3B  is featured by a second opening  214  additionally formed at a central portion of the supporter  200 . In different embodiments, this second opening  214  may be set at the central portion of the supporter  200  or alternatively formed on the second inclined surface  206  with a plurality of openings. This design of the second opening  214  diminishes a contact area between the photomask  114  and the supporter  200  so as to reduce the generation of dust and particles.  FIG. 3C  and  FIG. 3D  both represent another embodiment of the supporter  200  of the present invention. The supporter  200  of the present embodiment is characterized in that at least one guiding track  216  is arranged near the central portion. Alternatively, two guiding tracks  216  may be provided at two sides of said second opening  214 . On objective of the guiding track  216  is to further diminish the contact area between the photomask  114  and the supporter  200  when the photomask  114  contacts and slides on the supporter  200  so as to increase the yield of the manufacturing process. Besides, for fixing the supporter  200  in the top cover  102  of the photomask transport pod  100 , a pair of connecting components  218  may be additionally provided at two peripheral portions of a lower surface of the planar base  202  of the supporter  200 , as shown in  FIG. 4 . Thereby, the supporter  200  can be fixed at a side of the top cover  102 . The supporter  200  may be made of a static dissipative material with a surface resistivity ranging from about 10 4  to about 10 11 Ω or made of an elastic material. The static dissipative material is polyetheretherketone. 
         [0028]      FIGS. 5A ,  5 B and  6  provide one more embodiment of the plural supporters in the photomask pod. Therein, a supporter  300  comprises a base  302  and one or plural supporting points  304  arranged on the base  302  so that the base  302  can be fixed at each corner of the top cover  102  of the photomask transport pod  100 . At the meantime, a flexible bent component  306  is connected to the base  302 , wherein the flexible bent component  306  has one end integrally extending from the base  302  and has an opposing end flexibly suspending upon this or the plural supporting points  304 . The flexible bent component  306  further comprises a pressing surface  308  and a propping surface  310  so that when the top cover  102  and bottom plate  104  of the photomask transport pod  100  enclose the photomask  114 , the pressing surface  308  and the propping surface  310  of the flexible bent component  306  can contact and fix the photomask  114 . Additionally, this or the plural supporting points  304  may be configured on the supporter  300  obliquely with an included angle between each said supporting point  304  and the supporter  300 . The included angle may vary in different embodiments. In the present embodiment, the plural supporting points  304  are employed for example. Moreover, the supporter  300  is made of a static dissipative material with a surface resistivity ranging from about 10 4  to about 10 11 Ω and is detachably connected to the top cover  102  of the photomask transport pod  100 . The static dissipative material is polyetheretherketone. 
         [0029]      FIG. 7  illustrates one more embodiment of the plural retainers or supporters provided in the photomask pod. Therein, a photomask pod  100  comprises a first cover  102  and a second cover  104 , which can be assembled to enclose an inner space to accommodate a photomask  114 . The first cover  102  or the second cover  104  of the photomask pod or photomask transport pod  100  may be made of metal. Alternatively, a metal liner may be additionally equipped in the photomask pod or photomask transport pod  100  to provide the shielding effect so as to insulate an extrinsic interference. A plurality of supporters  112  in the photomask pod  100  may be provided in both the forms of the first supporter  112  and the third supporter  300 . The first supporter  112  are arranged on the second cover  104  and the third supporter  300  are deposited on the first cover  102 . A conductive panel  108  is arranged on a body  106  of the second cover  104  and the plural retainers  110  or the first supporter  112  are positioned on the conductive panel  108 , wherein the first supporter  112  are electrically connected to the conductive panel  108 . The retainers  110  and the first supporter  112  may be made of different materials or made of an identical material. Therein, the retainers  110  and the first supporter  112  are formed by multi-component injection molding method and then combined mutually. The first supporter  112  is provided as inserting pieces and is made of a static dissipative material having a surface resistivity ranging from about 10 4  to about 10 11 Ω. The third supporter  300  comprises a base  302  and one or plural supporting points  304  arranged thereon so that the base  302  can be fixed at each corner of the top cover  102  of the photomask pod  100 . Meanwhile, a flexible bent component  306  is connected to the base  302 , wherein the flexible bent component  306  has one end integrally extending from the base  302  and has an opposing end suspending upon the one or plural supporting points  304 . Thereby, when placed in the second cover  104  of the photomask pod  100 , the photomask  114  is supported by the plural retainers  110  and the first supporter  112  and is fixed on the second cover  104  by the retainers  110 . The retainers  110  surrounding the photomask  114  function to reduce possible vibrations occurred in transportation of the photomask pod  100  and to secure the photomask  114  to prevent impact. Hence, the retainers  110  and the first supporter  112  are provided to function collaboratively. When the first cover  102  and the second cover  104  enclose the photomask  114 , a flexible bent component  306  of the third supporter  300  on the first cover  102  further comprises a pressing surface  308  and a propping surface  310  so that the pressing surface  308  and the propping surface  310  of the flexible bent component  306  can contact the photomask  114  to fix it and jointly support the photomask  114 . Besides, since the photomask  114  directly contacts with the first supporters  112  and third supporter  300 , to use the static dissipative material with a surface resistivity ranging from about 10 4  to about 10 11 Ω as the material of the supporters can continuously conduct out charges so as to protect a photomask from being damaged by high heat resulted from transient discharge and to reduce charge accumulation and protect a photomask  114  from being damaged by static. 
         [0030]    One additional embodiment of the present invention is herein provided for illustrating the plural retainers or supporters settled in the photomask transport pod  100 . Therein, a photomask transport pod  100  comprises a top cover  102  and a bottom plate  104 , which can be assembled to enclose an inner space to accommodate a photomask  114 . The photomask transport pod  100  may be made of metal. Alternatively, a metal liner may be settled in the photomask transport pod  100  to provide the shielding effect so as to insulate an extrinsic interference. A plurality of supporters  112  in the photomask pod  100  may be provided in the forms of the first supporter  112 , the second supporter  200  and the third supporter  300 . The first supporters  112  are arranged on the bottom plate  104  and the second supporters  200  as well as the third supporters  300  are deposited on the top cover  102 . At four corners of the top cover  102 , the plural second supporters  200  or the third supporters  300  are provided and are detachably fastened to the corners of the top cover  102  by the connecting components  218  or the one or plural supporting points  304  of the base  302  thereof. The supporters  300  may be further equipped with a plurality of pressing surfaces  308  and propping surfaces  310  to fix and support the photomask  114 . When placed in the bottom plate  104  of the photomask transport pod  100 , the photomask  114  is supported by the plural retainers  110  as well as the first supporters  112  and is retained on the bottom plate  104  by the retainers  110 . When the top cover  102  is assembled to the bottom plate  104 , since the second supporters  200  are provided at the opening of a reversed-U shaped structure of the top cover  102  facing the bottom plate  104 , the second inclined surfaces  206  of the second supporters  200  helps the photomask  114  to be smoothly guided into the position of the reversed-U shaped structure. Meanwhile, because the third supporter  300  are provided at the corners of the top cover  102 , after being guided by the second inclined surfaces  206  of the second supporters  200  to the proper position, the photomask  114  is further jointly supported and fixed by the upper and lower fastening pieces  210  and  212  of the second supporters  200  and the pressing and propping surfaces  308  and  310  on the flexible bent component  306  of the plural third supporters  300 . Besides, since the photomask  114  directly contact with the first, the second and the third supporters  112 ,  200  and  300 , the static dissipative material of these supporters with the surface resistivity ranging from about 10 4  to about 10 11 Ω helps to continuously conduct out charges so as to protect the photomask from being damaged by high heat resulted from transient discharge. Since charge accumulation is reduced, the photomask is protected from being damaged by static. 
         [0031]    All of the features disclosed in this specification may be combined in any combination. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features. 
         [0032]    From the above description, one skilled in the art can easily ascertain the essential characteristics of the present invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, other embodiments are also within the scope of the following claims.