ELECTROSTATIC CHUCKING OF COVER GLASS WITH IRREGULAR SURFACE FLATNESS

Abstract

An electrostatic chuck apparatus for chucking glass includes a substantially rigid chassis with a plurality of apertures extending from one side of the chassis to another side of the chassis. A plurality of electrostatic chuck pins extend through the openings and are resiliently mounted to the chassis such that the extent to which the electrostatic chuck pins extend through the chassis is individually variable. With this construction, the electrostatic chuck pins maintaining contact with the surface of the glass despite the presence of some variation in the localized surface flatness of the glass.

Claims

1. An electrostatic chuck apparatus for chucking glass, the apparatus comprising: a substantially rigid chassis having a plurality of apertures extending from one side of the chassis to another side of the chassis; and a plurality of electrostatic chuck pins extending through at least a portion of the plurality of the apertures and being resiliently mounted to the chassis such that the extent to which the electrostatic chuck pins extend through the chassis is individually variable, whereby the chuck pins contour to a surface of the glass.

2. The electrostatic chuck apparatus of claim 1, wherein the surface of the glass comprises a localized surface flatness in the range from about 10 m to about 100 m.

3. An electrostatic chuck apparatus as claimed in claim 1 wherein the electrostatic chuck pins are spring-mounted to the chassis.

4. An electrostatic chuck apparatus as claimed in claim 1 wherein the chassis comprises a resilient sheet attached to a rigid panel, and wherein the electrostatic chuck pins are mounted to the resilient sheet.

5. An electrostatic chuck apparatus as claimed in claim 4 further comprising a second rigid panel attached to the resilient sheet such that the resilient sheet is sandwiched between the two rigid panels.

6. An electrostatic chuck apparatus as claimed in claim 1 wherein the electrostatic chuck pins are substantially cylindrical.

7. An electrostatic chuck apparatus as claimed in claim 1 wherein the electrostatic chuck pins each comprise first and second electrodes separated from one another by a dielectric which maintains a gap between the electrodes.

8. An electrostatic chuck apparatus as claimed in claim 7 wherein the electrodes are positioned within a ceramic cylinder.

9. An electrostatic chuck apparatus as claimed in claim 1 wherein the apparatus is adapted to withstand operating temperatures of up to about 260 degrees centigrade or more.

10. An electrostatic chuck apparatus as claimed in claim 4 wherein the resilient sheet comprises PFA fluoropolymer film with a thickness of between about 0.3 millimeters and about 0.5 millimeters.

11. An electrostatic chuck apparatus as claimed in claim 1 wherein the openings are cylindrical with a diameter of between about 5 millimeters and about 8 millimeters and the pins are cylindrical with a diameter of between about 2 millimeters and about 4 millimeters.

12. An electrostatic chuck apparatus as claimed in claim 3 wherein the apparatus is adapted to withstand operating temperatures of up to about 850 degrees centigrade.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0021] FIG. 1 is a schematic illustration of a number of a chucking apparatus according to one or more embodiments of the present disclosure.

[0022] FIG. 2A is a schematic, detailed perspective illustration of a portion of the chucking apparatus of FIG. 1.

[0023] FIG. 2B is a schematic, detailed partially cutaway illustration of a portion of the chucking apparatus of FIG. 2A.

[0024] FIG. 3 is a schematic, detailed, partially cutaway perspective illustration of a portion of the chucking apparatus of FIG. 1.

[0025] FIG. 3A is a schematic, detailed illustration of a portion of the chucking apparatus of FIG. 3.

[0026] FIG. 4A is a schematic, perspective view of a portion of a chucking apparatus according to one or more embodiments of the present disclosure.

[0027] FIG. 4B is a schematic, perspective view of a portion of a chucking apparatus according to one or more embodiments of the present disclosure.

[0028] FIG. 5 is a schematic, perspective view of a chucking apparatus according to one or more embodiments of the present disclosure.

[0029] FIG. 6 is a schematic, detailed perspective illustration of a portion of the chucking apparatus of FIG. 5.

[0030] FIG. 6A is a schematic, detailed partially cutaway illustration of a portion of the chucking apparatus of FIG. 5.

DETAILED DESCRIPTION

[0031] Referring now in detail to the various drawing figures, in which like reference characters represent like parts throughout the several views, FIGS. 1-3A show an electrostatic chuck apparatus 10 for chucking glass and including a substantially rigid chassis 12 with a plurality of apertures 15 extending from one side of the chassis to another side of the chassis. A plurality of electrostatic chuck pins 21 extend through the openings and are resiliently mounted to the chassis 12 such that the extent to which the electrostatic chuck pins 21 extend through the chassis 12 is individually variable. In other words, the chuck pins 21 can be moved up and down, side to side, and pitch and yaw to conform to localized surface irregularity. With this construction, surface contours of the glass can be followed by the electrostatic chuck pins 21, with the electrostatic chuck pins 21 maintaining contact with the surface of the glass despite some variation in localized surface flatness of the glass.

[0032] In one or more embodiments, the chassis 12 includes a resilient sheet 13 attached to a rigid panel 14, and the electrostatic chuck pins 21 are mounted to the resilient sheet 13. Optionally, a second rigid panel 16 can be attached to the resilient sheet 13 such that the resilient sheet 13 is sandwiched between the two rigid panels 14, 16. The resilient sheet 13 acts as a suspension to movably attach the pins to the chassis, while allowing the pins to move about as needed to conform to localized surface irregularities. As shown in the figures, the apparatus includes a flexible matrix of miniature pogo-like electrostatic chucks embedded in a flexible mounting.

[0033] In one or more specific embodiments, the electrostatic chuck pins 21 are substantially cylindrical bi-polar chucks and they have first and second electrodes 22, 23 separated from one another by a dielectric 24 which maintains a gap between the electrodes. In some embodiments, the electrodes 22, 23 are positioned within a ceramic cylinder 26. The cylinder 26 can bear a circumferential groove 27 about its midpoint for receiving the resilient sheet 13 therein. The size of the aperture in the resilient sheet may be closely matched to the diameter of the cylinder 26 in the bottom of the groove 27. The size of the aperture in the resilient sheet 13 can be slightly larger than, nominally smaller than, or the same size as the size of the diameter of the cylinder in the bottom of the groove 27. Thus, the resilient sheet 13 securely holds the electrostatic chuck pins 21 firmly in place. This construction also facilitates a rapid and inexpensive assembly of the device in that the individual electrostatic chuck pins can be attached, and accurately positioned, simply by pushing an electrostatic chuck pin 21 into a corresponding opening in the resilient sheet 13. Thus, to make the chuck apparatus, a large number of chuck pins can be inserted one at a time into the chassis (or gang assembled). As the pins are pushed into the chassis, the resilient nature of the resilient sheet 13 permits the chuck pins to be pushed in easily until the chuck pins are captured as the resilient sheet 13 is engaged in and captured by the groove 27 formed in the pin 21.

[0034] The apparatus according to one or more embodiments of the present disclosure compensates for the irregularity of the substrate surface needs to be achieved. Described in another way, the one or more embodiments described herein may incorporate a number of small pogo-like electrostatic chucks 21, which collectively can provide a substantial clamping force to hold a work piece securely in place. In one or more embodiments, the apparatus includes the electrostatic chuck pins 21, which each consists of two hemispheres of silver, with each hemisphere having an area of about 1.882 mm2. The two hemispheres are mounted into a 3 mm diameter ceramic aluminaAl2O3cylinder as shown in FIGS. 2A-2B. The two silver hemispheres are coated with a 60 m thick coating of aluminaAl2O3coating and polished to a flatness <10 m. The two silver electrodes are separated by a 1 mm gap (39.37 mil) 31 which has 418 volts per mil and should be able to withstand 16,456 VDC. A maximum of 3.6 kVDC is applied to each of the electrodes in the pogo electrostatic chuck. Two silver rods (positive and negative leads) 28, 29 are connected to each electrode 23, 24 and passed down through two separate holes in the ceramic cylinder 26.

[0035] FIG. 3 shows in detail the pogo-like electrostatic chucks 21 pressed into the compliant sheet 13, such as a PFA fluoropolymer film and arranged in a matrix to cover large areas of a substrate. Using a compliant material in the sandwich of the chassis 12 (i.e., the resilient sheet 13 sandwiched between the two rigid panels 14, 16) allows each pogo-like element 21 to translate independently of one another in the vertical direction, as well as to tilt in all directions in order to optimize surface contact with the substrate (work piece) at discreet element locations. Each pogo is capable of withstanding a process temperature of 850 C. around the middle of the ceramic cylinder a groove is cut for the purpose of the cylinder being retained by a flexible sheet as shown in FIG. 3. The capture of the flexible sheet allows the pogo to tilt and adjust vertically to compensate for the variation in localized surface flatness of the substrate. The flexible sheet is made from a high temperature polymer such as (but not limited to) PFA fluoropolymer film and is 0.3 mm to 0.5 mm thick depending on the elasticity of the selected material to provide the right degree of flexibility. To retain the flexible sheet a sandwich of thicker material such as (but not limited to) PFA fluoropolymer film which has a service temperature range of up to 260 C. (which sets the temperature operational range of this flexible electrostatic chuck) is used to provide the control over how much flexibility the sheet sandwiched between the thicker matrix of holes has. Larger diameter holes provide the most leverage for tilt and up and down motion. The diameter of these guide holes may be in the range of 5 mm to 8 mm.

[0036] In one or more embodiments, the apparatus is adapted to withstand operating temperatures of up to about 260 degrees centigrade or more. Optimally, the apparatus is adapted to withstand operating temperatures of up to about 850 degrees centigrade.

[0037] Optionally, the resilient sheet comprises a PFA fluoropolymer film with a thickness of between about 0.3 millimeters and about 0.5 millimeters and the openings are cylindrical with a diameter of between about 5 millimeters and about 8 millimeters and the pins are cylindrical with a diameter of between about 2 millimeters and about 4 millimeters.

[0038] FIG. 4 shows an optional guide laminate structure 40 to retain a compliant flexible gasket, which in turn retains the pogo-like electrostatic chucks. Some optional configurations can include flat and rigid, flat and flexible, formed and rigid, formed and flexible, etc. In particular, FIG. 4 shows a curved guide laminate structure 40, while FIG. 4A shows a flat guide structure 45.

[0039] Optionally, as shown in FIGS. 5-6A, the electrostatic chuck pins 121 of the apparatus 110 can be spring-mounted to the chassis 112. In this alternative embodiment, a similar construct of the pogo is shown in FIG. 1, but instead of using a flexible sheet to permit a range of motion, a dual spring mechanism is used to retain the pogo-like chuck pins 121. The pogo-like electrostatic chuck pins 121 in this embodiment have only a vertical motion capability, substantially without tilt, and in most cases the tilt is not required to overcome the variation in localized surface flatness of substrates. The pogo-like electrostatic chuck pin 121 is press fit into a rigid dielectric block 112, such as aluminaAl2O3with a matrix of holes 115 as shown in FIGS. 5 and 6. Mechanical springs 131, 132 allow each pogo-like element 121 to translate independently in a vertical direction (transverse to the plane of the retaining block/plate 112), sliding within bores 115 formed in the rigid structure of the retaining block/plate 112. The advantage of this arrangement is that the temperature capability of this matrix of pogo electrostatic chucks is greatly enhanced and can operate in temperatures up to 850 C.

[0040] While the disclosure has been described in terms of various illustrative embodiments, those skilled in the art will appreciate that various changes, additions, deletions, and modifications can be made therein without departing from the spirit and scope of the disclosure as defined in the appended claims. For example, the various aspects of the disclosure may be combined according to the following exemplary embodiments.

Embodiment 1

[0041] An electrostatic chuck apparatus for chucking glass, the apparatus comprising:

[0042] a substantially rigid chassis having a plurality of apertures extending from one side of the chassis to another side of the chassis; and

[0043] a plurality of electrostatic chuck pins extending through at least a portion of the plurality of the apertures and being resiliently mounted to the chassis such that the extent to which the electrostatic chuck pins extend through the chassis is individually variable, whereby the chuck pins contour to a surface of the chucking glass.

Embodiment 2

[0044] The electrostatic chuck apparatus of embodiment 1, wherein the surface of the chucking glass comprises a localized surface flatness in the range from about 10 m to about 100 m.

Embodiment 3

[0045] An electrostatic chuck apparatus as in Embodiment 1 or Embodiment 2 wherein the electrostatic chuck pins are spring-mounted to the chassis.

Embodiment 4

[0046] An electrostatic chuck apparatus as in any one of Embodiments 1-3 wherein the chassis comprises a resilient sheet attached to a rigid panel, and wherein the electrostatic chuck pins are mounted to the resilient sheet.

Embodiment 5

[0047] An electrostatic chuck apparatus as in Embodiment 4 further comprising a second rigid panel attached to the resilient sheet such that the resilient sheet is sandwiched between the two rigid panels.

Embodiment 6

[0048] An electrostatic chuck apparatus as in any one of Embodiments 1-5 wherein the electrostatic chuck pins are substantially cylindrical.

Embodiment 7

[0049] An electrostatic chuck apparatus as in any one of Embodiments 1-6 wherein the electrostatic chuck pins each comprise first and second electrodes separated from one another by a dielectric which maintains a gap between the electrodes.

Embodiment 8

[0050] An electrostatic chuck apparatus as in Embodiment 7 wherein the electrodes are positioned within a ceramic cylinder.

Embodiment 9

[0051] An electrostatic chuck apparatus as in any one of Embodiments 1-8 wherein the apparatus is adapted to withstand operating temperatures of up to about 260 degrees centigrade or more.

Embodiment 10

[0052] An electrostatic chuck apparatus as in Embodiment 4 wherein the resilient sheet comprises PFA fluoropolymer film with a thickness of between about 0.3 millimeters and about 0.5 millimeters.

Embodiment 11

[0053] An electrostatic chuck apparatus as in any one of Embodiments 1-10 wherein the openings are cylindrical with a diameter of between about 5 millimeters and about 8 millimeters and the pins are cylindrical with a diameter of between about 2 millimeters and about 4 millimeters.

Embodiment 12

[0054] An electrostatic chuck apparatus as in Embodiment 3 wherein the apparatus is adapted to withstand operating temperatures of up to about 850 degrees centigrade.