Abstract:
The invention features an apparatus for mounting a pellicle to a reticle. The apparatus includes: a base; a first holder coupled to the base and including two edges positioned to support a first object below its center of gravity and secure the first object in substantially vertical alignment with the base, the first object including one of the pellicle and the reticle; a second holder slidably coupled to the base and including two edges positioned to support a second object below its center of gravity and secure the second object in substantially vertical alignment with the base, the second object including the other of the pellicle and the reticle; and a pressure applicator assembly slidably coupled to the base to adjustably apply pressure to a periphery of the second object held in the second holder and drive it against a corresponding periphery of the first object held in the first holder. In additional embodiments, the apparatus provides automated mounted of the pellicle and reticle.

Description:
TECHNICAL FIELD 
     This invention relates to a pellicle mounting apparatus. 
     BACKGROUND 
     A reticle plate, usually made of glass or quartz, can be used as a mask as part of the process of producing various semiconductor devices such as integrated circuits. If any dust or particles fall onto the surface of the mask, this will produce an inaccurate reproduction from the mask including spots representing the dust or particles. To protect the mask from dust or other particles, a pellicle (which consists of a thin transparent membrane) is positioned adjacent to and spaced from the mask so that any dust or other particles will fall onto the membrane rather than the mask. Thus, the dust and other particles will be out of focus when the mask is used. 
     Pellicles are generally formed with a frame member supporting the periphery of the membrane. The frame member is attached to the reticle by an adhesive so that the membrane is maintained in a fixed relationship with the mask. The frame member itself is extremely fragile and susceptible to damage or distortion by any direct pressure or flexing of the pellicle. 
     A pellicle frame tray, such as a MicroLithography Inc. Pellicle Tray (Part Number “CAN34P0061”), is often used in assembling a reticle to a framed pellicle. The use of the tray provides some additional reinforcement of the pellicle frame member during assembly. 
     SUMMARY 
     In general, in one aspect, the invention features an apparatus for mounting a pellicle to a reticle. The apparatus includes: a base; a first holder coupled to the base and including two edges positioned to support a first object below its center of gravity and secure the first object in substantially vertical alignment with the base, the first object including one of the pellicle and the reticle; a second holder slidably coupled to the base and including two edges positioned to support a second object below its center of gravity and secure the second object in substantially vertical alignment with the base, the second object including the other of the pellicle and the reticle; and a pressure applicator assembly slidably coupled to the base to adjustably apply pressure to a periphery of the second object held in the second holder and drive it against a corresponding periphery of the first object held in the first holder. 
     In some embodiments, the apparatus further includes a bi-directional actuator coupled to the pressure applicator assembly to drive and retract the pressure applicator assembly in relation to the base. For example, during operation the actuator can drive the pressure applicator assembly against the second object to cause the second holder to slide towards the first holder. 
     In general, in another aspect, the invention features an automated apparatus for mounting a pellicle to a reticle. The apparatus includes: a base; a first holder coupled to the base and positioned to support a first object in substantially vertical alignment to the base, the first object including one of the pellicle and the reticle, the first holder including at least one sensor for determining the presence or absence of the first object in the first holder; a second holder slidably coupled to the base and positioned to support a second object in substantially vertical alignment with the base, the second object including the other of the pellicle and the reticle, the second holder including at least one sensor for determining the presence or absence of the second object in the second holder; a pressure applicator assembly slidably coupled to the base to adjustably apply pressure to a periphery of the second object held in the second holder and drive it against a corresponding periphery of the first object held in the first holder; and an actuator coupled to the pressure applicator assembly and responsive to the sensors in the first and second holder to drive the pressure applicator assembly towards the first holder for a time interval when the first and second object are in the first and second holders. 
     For example, the sensors can include retroflective light sensors or mechanical sensors. In some embodiments, a user sets the time interval. Alternatively, a controller coupled to the actuator can set the time interval in an automated fashion. Furthermore, during operation the actuator can retract the pressure applicator assembly away from the first holder after the time interval. 
     In general, in another aspect, the invention features an apparatus for mounting a pellicle to a reticle. The apparatus includes: a base; a first holder coupled to the base and positioned to support a first object in substantially vertical alignment to the base, the first object including one of the pellicle and the reticle; a second holder slidably coupled to the base and positioned to support a second object in substantially vertical alignment with the base, the second object including the other of the pellicle and the reticle; and a pressure applicator assembly slidably coupled to the base to adjustably apply pressure to a periphery of the second object held in the second holder and drive it against a corresponding periphery of the first object in the first holder. The pressure applicator assembly includes: a slidable bracket coupled to the base; a back plate rigidly attached to the slidable bracket; an intermediate plate pivotally coupled to the back plate along at least one axis; and a front plate pivotally coupled to the intermediate plate along at least one other axis, the front plate having a plurality of contact points configured to align with the periphery of the second object held in the second holder. 
     In some embodiments, the pressure applicator assembly further includes a first at least one tensioning device positioned to apply tension to the pivotal coupling between the back plate and the intermediate plate, and a second at least one tensioning device positioned to apply tension to the pivotal coupling between the front plate and the intermediate plate. For example, the first and second tensioning devices can include a plurality of springs. 
     In general, in another aspect, the invention features an apparatus for mounting a pellicle to a reticle. The apparatus includes: a base; a first holder coupled to the base and positioned to support a first object in substantially vertical alignment to the base, the first object including one of the pellicle and the reticle; a second holder slidably coupled to the base and positioned to support a second object in substantially vertical alignment with the base, the second object including the other of the pellicle and the reticle; a pressure applicator assembly slidably coupled to the base to adjustably apply pressure to a periphery of the second object held in the second holder and drive it against a corresponding periphery of the first object held in the first holder; and a laminar air flow source configured to provide air flow along the substantially vertically aligned first and second objects. 
     Embodiments of any of the different aspects of the invention described above can include any of the following features. 
     The pressure applicator assembly can be configured to adjust to the orientation of the periphery of the second object and apply uniform pressure to the periphery of the second object. 
     The first object can include a pellicle tray supporting the pellicle. Alternatively, the first object can be the pellicle, e.g., a framed pellicle. Furthermore, the pellicle can include an adhesive along the periphery of one of its faces. 
     The first holder can be rigidly coupled to the base and include a backing plate positioned to support a back periphery of the first object. Moreover, the first holder can further include: an upright bracket coupled to the base; and a translation frame rigidly coupled to the upright bracket and to the backing plate, the translation frame configured to allow adjustment of the backing plate in a substantially vertical plane relative to the base. Alternatively, the first holder can be slidably coupled to the base, and the apparatus can further includes a backing plate rigidly secured to the base and extending substantially vertically from the base, wherein the backing plate is configured to support a back periphery of the first object. 
     The actuator can be a bi-directional cylinder, e.g., a pneumatic cylinder, configured to drive the pressure applicator assembly towards the first holder and alternately to retract the pressure applicator assembly away from the first holder. 
     The apparatus can further include a shock absorber coupled to at least one of the pressure applicator and the second holder and positioned between the pressure applicator and the second holder. Moreover, the apparatus can further include a shock absorber coupled to at least one of the first holder and the second holder and positioned between the first holder and the second holder. 
     Embodiments of the invention may include many advantages. 
     For example, the apparatus can allow mounting of a framed pellicle to a reticle with minimal distortion or damage to the individual or completely assembled parts. The reticle holder and pellicle tray holder both utilize support edges that provide support below their center of gravity, thus the reticle and pellicle are supported vertically without mechanical or pneumatic pressure. Furthermore, the pressure applicator can uniformly apply pressure to the periphery of the reticle and pellicle during assembly. Moreover, the apparatus can also provide for integrated laminar airflow to remove contaminants during mounting and assembly. 
     Furthermore, embodiments of the apparatus can be automated to provide highly accurate alignment of the framed pellicle to the reticle over repeated mountings. Also, the use of a pellicle tray can accommodate the use of different sized pellicle frames. 
     Other features, objects, and advantages of an embodiment will be apparent from the following description and drawings, and from the claims. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is a sectional view of an embodiment. 
     FIG. 2 is an overhead sectional view of an embodiment. 
     FIG. 3 is a sectional view showing a pellicle holder and pressure applicator assembly. 
     FIG. 4 is a side-angle view of an embodiment. 
     FIG. 5 is a side-angle view of an embodiment. 
     FIG. 6 is a perspective of a pellicle tray. 
     FIGS. 7A-7C are cross-sectional views of a pellicle tray, a pellicle frame and a reticle in un-assembled and assembled views. 
     FIG. 8 is a sectional view of an embodiment in an “Open” position. 
     FIG. 9 is a cut-away sectional view of an embodiment in the “Open” position. 
     FIG. 10 is a sectional view of an embodiment in the “Support Contact” position. 
     FIG. 11 is a sectional view of an embodiment in the “Closed” position. 
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring to FIG. 1, in an embodiment of a pellicle mounting apparatus  100  includes a pellicle holder brace  104  fixed to a base frame  102 . An adjustable translation stage  108  is attached to the upright portion of pellicle holder brace  104 . Pellicle tray holder plate  110  is attached to the face of adjustable translation stage  108 . Referring to FIG.  4  and FIG. 1, adjustment means  109 A, 109 B allow the pellicle tray holder plate  110  to be translated relative to the upright portion of pellicle holder brace  104 , in the two planes parallel to the upright portion of pellicle holder brace  104 . 
     Referring again to FIG. 1, a pressure applicator brace  118  includes three pressure adjustment plates: a back plate  120 , a middle plate  122 , and a front plate  124 . Back plate  120  is rigidly attached to the pressure applicator brace  118 . Referring to FIG.  2  and FIG. 1, middle plate  122  is attached with two pivot pins  128 A, 128 B to back plate  120 . Pivot pins  128 A, 128 B allow middle plate  122  to tilt in one axis relative to the upright portion of pressure applicator brace  118  and a reticle holder  114 . Front plate  124  is attached with two pivot pins  126 A, 126 B to middle plate  122 . Pivot pins  126 A, 126 B allow front plate  124  to tilt in another axis relative to the upright section of pressure applicator brace  118  and reticle holder  114 . In a preferred embodiment, the front plate tilt axis is approximately 90 degrees away from the tilt axis of middle plate  122 . 
     Referring to FIG.  3  and FIG. 1, spring plungers  130 A,  130 B are positioned to provide spring tension between the middle plate  122  and the back plate  120 . Spring plungers  132 A, 132 B are positioned to provide spring tension between front plate  120  and middle plate  122 . Bottom plates  150  and  152  are attached to the lower sections of reticle holder  114  and pressure applicator brace  118  respectively. Bearing blocks  320 A, 320 B are attached to bottom plates  150  and  152 . Slide rails  154 A, 154 B are attached to the lower section of base frame  102 . The bearing blocks  320 A, 320 B and slide rails  154 A, 154 B allow for the reticle holder  114  and pressure applicator brace  118  to slide back and forth relative to the base frame and relative to the pellicle tray holder plate  110 . Reticle holder  114  includes two stop blocks  170 , 172  fixed to the bottom of the reticle holder and in line to contact shock absorbers  180  and  182  respectively, as will be explained. 
     FIG. 2 shows another view of an embodiment from above the pellicle mounting apparatus  100  and includes cross-sectional references C—C, D—D, E—E. FIG. 3 shows the view C—C from FIG. 2, which is a cross-section of reticle holder  114 . Referring to FIG.  2  and FIG. 3, reticle holder  114  includes reticle edge supports  204 A, 204 B and reticle retaining clips  206 A, 206 B rigidly attached to reticle holder  114  to form two grooves for supporting a reticle in a vertical position. Reticle retaining clip  206 C rigidly attached to reticle holder  114  forms a pocket for supporting a corner of a reticle in a vertical position. Pressure applicator pins  140 A- 140 -H are rigidly attached to the pressure applicator front plate  124 . 
     Referring to FIG.  4  and FIG. 5, pellicle tray holder plate  110  includes two pellicle tray edge supports  200 A, 200 B and two pellicle tray retaining clips  112 A, 112 B which are rigidly attached to pellicle tray holder  110  and form two grooves for supporting a pellicle tray in a vertical position. 
     FIG. 6 shows a pellicle tray  600 . 
     FIGS. 7A-7C shows a pellicle tray  600 , a framed pellicle  602  and a reticle  604  before assembly (FIG.  7 A), during assembly (FIG. 7B) and after assembly and separation (FIG.  7 C). The framed pellicle  602  includes a layer of adhesive material  606  on the surface of the framed pellicle  602 . 
     In one embodiment, the pellicle tray holder is implemented to hold a pellicle tray, with a framed pellicle contained therein. The use of the pellicle tray, therefore, allows for a variety of pellicle frame sizes to be accommodated. In another embodiment, the pellicle tray holder could be implemented to hold the framed pellicle without the use of the pellicle tray. 
     FIG.  8 . shows a view of an embodiment in the “Open” position, with a reticle  604  loaded into reticle holder  114 , and a pellicle tray  600  and framed pellicle  602  loaded into pellicle tray holderplate  110 . The cut away view of base frame  102  shows hydraulic cylinder  802  connected to base frame  102  with attachment means  830 . Attachment means  830  can be one or more pins, screws, or bolts to enable an essentially rigid connection for hydraulic cylinder  802  to the base frame  102 . Piston rod  804  extends from cylinder  802  and is connected to pressure applicator brace  118  with coupling  806  and down rod  808 . Retention spring  160  is attached to reticle holder  114  and pressure applicator brace  118 . 
     FIG. 9 shows a “cut off” view of an embodiment in the “Open” position. Reticle holder down tab  304  is rigidly attached to the bottom of bearing plate  150 . Reticle holder stop block  302  is rigidly attached to base frame  102 . In operation, pressure is applied to cylinder  802  extending piston rod  804  which pushes pressure applicator brace  118  to the “Open” position along guide rail  154 . Retention spring  160  is stretched as pressure applicator brace  118  slides to the “Open” position while reticle holder  114  remains stationary due to down tab  304  coming into contact with stop block  302 . As a result, a wider gap  810  is created between reticle holder  114  and pressure applicator brace  118 . Flexible retention cable  210 , shown in FIG. 2, is connected to both reticle holder  114  and pressure applicator  118 . In operation, as cylinder  802  forces pressure applicator  118  away from reticle holder  114 , flexible retention cable assists in preventing an over-extension of retention spring  160 . Once in the “Open” position, a reticle  604  can be loaded into reticle holder  114  without interference from pressure applicator pins  140 A- 140 H. 
     FIG. 10 shows a view of invention in the “Support Contact” position. In operation, to achieve the “Support Contact” position from the “Open” position, pressure is released from cylinder  802 , piston rod  804  retracts and pressure applicator brace  118  travels towards reticle holder  114 . Pressure applicator brace  118  includes a shock absorber  180  attached near the bottom of brace  118  so that as the brace travels towards reticle holder  114 , shock absorber  180  contacts stop block  170 . The shock absorber reduces the initial impact of pressure applicator pins  140 A- 140 H against the reticle  604  and allows a period of time for the pressure applicator pins to adjust in relation to the reticle and thereby allow an even application of pressure to the reticle. In the preferred embodiment, the pressure applicator, which includes the three pressure adjustment plates, provides a uniform application of pressure at the periphery of the reticle as the apparatus is brought into the “Support Contact” position. The combined effect of the pivoting plates and spring plungers is to allow the pressure applicator pins to adjust as contact as made with the reticle and allow all of the applicator pins to make contact with the reticle before any significant force is applied. 
     FIG. 11 shows a view of invention in the “Closed” position. In operation, to achieve the “Closed” position from the “Support Contact” position, pressure is released from cylinder  802 , piston rod  804  retracts causing pressure applicator brace  118 , which is now in contact with reticle holder through shock absorber  180  and stop block  170 , to slide along guide rail  154  towards pellicle tray holder  110 . Next, shock absorber  182 , mounted on pellicle tray holder  110  comes into contact with stop block  172  of reticle holder. Shock absorber  182  reduces the initial impact of the combined reticle holder  114  and pressure applicator brace  118  as it slides against pellicle frame holder  108  and the framed pellicle  602  and pellicle tray  600 . In the “Closed” position pressure is maintained through pressure applicator brace  118 , pressure applicator pins  140 A- 140 H, reticle  604 , adhesive layer  606 , pellicle  602 , pellicle frame  600  and against pellicle tray holder  110 . The apparatus remains in the “Closed” position according to a user definable time interval. The time interval required is defined by the requirements of the adhesive applied to the reticle and/or pellicle. Once this time interval has passed the apparatus can return to the “Open” position by reversing the cylinder  802  to extend the piston rod  804  which allows for the removal of the pellicle tray  600 , and reticle  602 /framed pellicle package to be removed individually (as shown in FIG.  7 C). 
     In one embodiment, the user can define the time interval for the apparatus to remain in the “Closed” position. In another embodiment, an external device can set the time interval. In another embodiment the time interval can be a fixed time period that is not adjustable. 
     The embodiments, as described above, provides for a simple yet efficient vertical mounting and support of a reticle and pellicle tray. The two edge supports of the holders provide mechanism for supporting each object below their center of gravity, without mechanical means. Therefore, the reticle and pellicle tray can be held vertically without the risk of distorting them before, during and after the mounting of the fragile reticle to the framed pellicle. Also, the vertical mounting fixtures provide a mechanism for simple loading and un-loading of the pellicle tray, framed pellicle, reticle and final assembled parts. 
     Referring to FIG.  4  and FIG. 1, adjustment means  109 A,  109 B allow the pellicle tray holder plate  110  to be translated in two planes relative to the upright portion of pellicle holder brace  104 . With the pellicle mounting apparatus at or near the “Closed” position, an operator can adjust the position of pellicle holder plate  110  relative to the to the reticle holder  114  and a reticle  604  (if loaded). The adjustment means  109 A,  109 B together with the mounting of the pellicle holder plate  110  in relation to the reticle holder  114 , allow for finely tunable adjustment which is maintainable through repeated mounting operations. 
     Referring again to FIG. 2, exemplary air flow holes are shown, including top frame air flow hole  220  and holder air flow hole  222 . Referring to FIG. 3, additional exemplary air flow holes are shown, specifically bottom frame air flow holes  350 A, 350 B. The exemplary air flow holes represent a multiplicity of air flow holes in the top frame, bottom frame and holders. The combined effect of using vertical mounting fixtures along with the exemplary air flow holes is to allow for an airflow to be applied vertically past the reticle and framed pellicle during the assembly process. The air source may be provided by a laminar air flow chamber. The vertical air flow provides a benefit of reducing the framed pellicle and reticle to contaminant exposure during assembly. 
     Referring again to FIG. 1, holder full sensors  190 A, 190 B, are mounted on reticle holder  114  and pellicle holder brace  104 , respectively. Sensors  190 A,  190 B can be utilized in an automated assembly process to detect the presence or absence of a framed pellicle or reticle to assure that the mounting operation does not occur until both elements are present in the apparatus. Examples of sensors  190 A,  190 B include retroflective light sensors which reflecting a light source at a location and use the reflected light information to determine the presence of absence in that location. 
     In an alternative embodiment, a mechanical sensor, or sensors, could be used to detect the absence or presence of an object in the reticle holder or the pellicle tray holder. For example, a weight sensor could be used. 
     In another embodiment, the role of each of the holders could be reversed. That is the the first holder (the reticle holder as described above) and the second holder (the pellicle tray holder as described above) could each be used to hold either a reticle or pellicle. The operation of the machine would remain essentially the same, with the pressure applicator contacting the object held in the first holder first, then apply pressure through the first object to the second object held in the second holder. In another embodiment, both the second holder could also be slidably coupled to the frame. 
     Cylinder  802  can be implemented as a hydraulic cylinder or a pneumatic cylinder. 
     A number of embodiments of an embodiment have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of an embodiment. Accordingly, other embodiments are within the scope of the following claims.