Handling: hand and hoist-line implements – Utilizing fluid pressure – Venturi effect
Reexamination Certificate
1999-05-13
2001-08-28
Kramer, Dean J. (Department: 2167)
Handling: hand and hoist-line implements
Utilizing fluid pressure
Venturi effect
C414S941000
Reexamination Certificate
active
06279976
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to semiconductor processing and, more particularly, to an improved apparatus and method for handling warped semiconductor wafers.
BACKGROUND OF THE INVENTION
Automated wafer handling equipment is heavily employed during the fabrication of semiconductor wafers. Generally speaking, wafer handling equipment includes those devices used to transfer a wafer from one location to the next or to secure a wafer during a particular process. It is critical that these devices engage the wafer in such a way that refrains from damaging the fragile circuits located on the wafer face. One apparatus that satisfies this requirement is a vacuum-assisted coupling device. This device operatively engages the wafer surface with sufficient vacuum pressure to secure the wafer thereto. Although various vacuum-assisted devices are used throughout wafer fabrication, the present invention relates primarily to a vacuum-assisted retaining chuck for securing a wafer during processing and the remainder of the discussion will focus on the same.
The vacuum chuck has a generally planar engaging surface for coupling to the wafer surface. In communication with the engaging surface is a vacuum port. The chuck is brought into contact with a first or face side of the wafer and a vacuum source coupled to the vacuum port is activated. As the vacuum is drawn, the wafer is pulled into contact with the engaging surface. The combination of vacuum pressure and the frictional forces resulting between the wafer and the engaging surface securely retain the wafer relative to the chuck. Vacuum chucks are used on many wafer processing machines including, for example, backgrinders and wafer inspection equipment. Unlike vacuum transfer devices which need only support the wafer during transport, the vacuum chuck rigidly holds the wafer while the latter is subjected to various external forces introduced during wafer processing.
While the vacuum chuck performs more than adequately with flat wafers, problems occur when the wafer is warped. Wafer warpage may result from various thermal, mechanical, and chemical processes. Since a warped wafer cannot lie flat against the engaging surface of the vacuum chuck, vacuum leaks form therebetween. These leaks prevent the chuck from adequately sealing with the wafer. As a result, the wafer may shift or even dislodge from the chuck.
To alleviate this problem, some chucks provide an O-ring seal member proximal the perimeter of the chuck. The O-ring acts as a cushion and can improve sealing against wafers having slight warp. Unfortunately, the O-ring is ineffective in attempting to seal against wafers having significant warp.
Current techniques used to couple warped wafers to the vacuum chuck include, for example, utilizing relative high vacuum pressure. Unfortunately, higher vacuum pressure requires more expensive vacuum sources and more energy to operate. Another wafer coupling technique involves pressing the wafer against the chuck, generally by hand, as the vacuum is drawn. By momentarily deflecting the wafer in this way, the planar surface seals against the wafer and permits an effective vacuum. While effective in some circumstances, this practice is time consuming and requires operator intervention. In addition, this manual technique may cause damage to the wafer surface. Furthermore, if the wafer slips off the chuck, potential injury to the operator may result.
Thus, there are unresolved issues with current wafer vacuum chucks. What is needed is a chuck that can easily couple to a significantly warped wafer. What is further needed is a vacuum chuck that can couple to a warped wafer without operator intervention and while operating at relatively low vacuum pressures.
SUMMARY OF THE INVENTION
A device adapted to vacuum-couple to an object having a non-conforming surface is disclosed. In one embodiment, the device comprises an engaging surface adapted to receive the object and one or more vacuum ports in communication with the engaging surface. The device further includes a conforming sealing member extending around a perimeter of the engaging surface. The sealing member is adapted to form an air-tight seal between the engaging surface and the non-conforming surface and maintain the air-tight seal until the non-conforming surface deflects, under application of vacuum pressure, sufficiently to conform and seal against the engaging surface.
A method of vacuum-coupling a device to an object having an irregular surface is similarly provided. In one embodiment, the method comprises providing a coupling device. The coupling device has an engaging surface with at least one vacuum port in communication therewith and a flexible sealing member extending around a perimeter of the engaging surface. The engaging surface is adapted to receive the object. The method furthermore comprises positioning the engaging surface proximal the object and activating a vacuum source fluidly coupled to the vacuum port to create vacuum pressure at the vacuum port. By deforming the sealing member under vacuum pressure, the sealing member conforms to the irregular surface and seals thereto. By continuing to apply vacuum pressure, the object deflects and is drawn to the engaging surface where the object forms a vacuum seal with the engaging surface.
In another embodiment, a vacuum chuck assembly for receiving and fixedly retaining a semiconductor wafer having a warped surface is provided. The chuck assembly comprises a vacuum chuck having a planar engaging surface adapted to seal against and retain the wafer, and one or more vacuum ports in communication with the engaging surface. The chuck assembly further includes a conforming flexible cup extending around a perimeter of the engaging surface, the cup adapted to form an air-tight seal between the engaging surface and the warped surface. The cup maintains the air-tight seal until the warped surface deflects, under application of vacuum pressure, sufficiently to conform and seal against the engaging surface.
In yet another embodiment, a vacuum chuck assembly for receiving and retaining semiconductor wafers having a warped surface is provided. Here, the chuck assembly comprises a cylindrical vacuum chuck having: a face side, the face side having a planar, ring-shaped engaging surface adapted to contact the wafer and a recessed portion bounded by the engaging surface; and a backside adapted to attach the chuck to a chuck receiving component. The assembly further comprises at least one vacuum port located on the recessed portion wherein the vacuum port is adapted to fluidly couple to a vacuum source. In addition, the assembly includes a conforming flexible cup extending around a perimeter of the engaging surface, the cup adapted to form an air-tight seal between the engaging surface and the warped surface. The cup maintains the air-tight seal at least until the warped surface deflects, under application of vacuum pressure, sufficiently to conform the cup to the engaging surface. The cup further includes a flared lip which extends outwardly from the chuck in a funnel-like manner and terminates at a lip edge.
In still yet another embodiment, a wafer inspection apparatus is provided, comprising: one or more transducers adapted to measure a semiconductor wafer; and a vacuum chuck assembly operatively connected to the apparatus. The chuck assembly comprises: a chuck having an engaging surface and a vacuum port in communication with the engaging surface; and a flexible seal coupled to the chuck and extending around a perimeter of the engaging surface. The flexible seal is adapted to conform to the wafer and permit effective vacuum sealing of the wafer to the engaging surface regardless of surface irregularities in the wafer.
Advantageously, the present invention permits effective vacuum sealing of a semiconductor wafer to a vacuum chuck assembly regardless of wafer warpage. By effectively providing a vacuum seal to the warped wafer surface, manual intervention is not required to ensure coupling to the chuck assembly. Furthermore, the prese
Kramer Dean J.
Micro)n Technology, Inc.
Schwegman Lundberg Woessner & Kluth P.A.
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