Patent Application
20240034912
Not applicable.
The invention relates generally to microfiber arrays providing enhanced friction to surfaces. More specifically, the invention relates to an array of micro- and nano-scale fiber arrays that have fibers with roughened tips that provide friction characteristics and controllable weak normal adhesion useful in the handling of smooth and flat objects, such as the handling of semiconductor devices during the fabrication process.
Semiconductor manufacturing involves several processing steps. For example, a silicon wafer being fabricated into a die may undergo cleaning, passivation, photolithography, etching, deposition, polishing, grinding, dicing, chip/die packaging, etc. Each of these steps is performed in a dedicated piece of equipment within a larger fabrication environment. Careful handling of the wafers, dies, and other semiconductor devices is required during and between each processing step to reduce/prevent particle contamination, maintain high yields, and reduce the footprint of equipment in the fabrication area. In addition, increasing the speed in which the semiconductor devices are moved from one processing area to another can improve throughput. More specifically, in one typical wafer handling process, a semiconductor wafer will be rapidly accelerated by machinery in contact with the backside of the wafer. The maximum possible rate of acceleration without slippage depends on the friction between the end effector of the machine and the wafer. With greater friction, the device can be accelerated more rapidly, increasing the process throughput, and thus its profitability. While efficiency is critical, wafers must also be able to be released easily, with near zero vertical adhesion between the wafer and end effector pad. If adhesive forces at this interface are too high, there is increased risk of: (1) semiconductor device damage, (2) semiconductor device mis-alignment, and (3) residual contamination from the end effector which reduces the yield of the semiconductor.
Many manufacturers use elastomer pads with or without vacuum clamping on the end effector of the machinery used to move or transfer the semiconductor device. However, elastomer pads can introduce contamination as the soft rubber materials wear, leaving microscopic particles on the semiconductor device. Similarly, vacuum clamping can introduce contamination or damage thin or curved surfaces of some semiconductor devices. They can also be expensive to operate and maintain. Pressure sensitive adhesives are not often used because they can leave residue on the semiconductor device and require increased effort to release from the end effector. Therefore, novel materials which demonstrate high friction with surfaces such as those on a semiconductor wafer or device while minimizing normal adhesion at this interface will overcome the limitations of conventional solutions and have significant commercial value.
One embodiment of the present invention is a microfiber array having fibers with roughened tips capable of providing a controlled amount of friction when in contact with smooth flat surfaces and patterned surfaces, such as the surface of a silicon wafer while maintaining controllable near zero adhesion at the interface of the roughened fiber tips and the contacting surface. The microfiber array, in one embodiment, comprises a plurality of micro- or nano-scale fibers extending from a surface, where the fibers have an enlarged, shaped tip with a rough surface. The tips make contact with the surface of the wafer or other object and provide a friction force, but little to no adhesion. With controllable low adhesion, a semiconductor device in contact with the microfiber array can be moved rapidly from one manufacturing process to the next, while easily released from the surface in the vertical direction.
In one example embodiment, as shown in
The stem 103 and tip 104 are symmetrical about a symmetry axis, such that radius of the stem 103 (up to the point of connection 105 with the tip 104) is constant along the length of the stem 103. However, in alternative embodiments, the radius of the stem 103 can vary along its length, including one embodiment where the radius of the stem 103 near the backing layer 102 is enlarged. The tip 104 can be symmetrical and fixed in a radial direction to enable increased contact with the surface of the semiconductor device, such as a silicon wafer, chip, die, semiconductor package, or other similar device. In one embodiment, the surface of the tip 104 and the cross-section of the stem 103 are circular. In other embodiments, however, an oval or elliptical shape and/or cross-section may be used. The shape of the sides on the underside of the mushroom tip 104 is linear but, alternatively, can be convex or concave with respect to the stem axial direction and tip surface. In the example embodiment shown in
In one embodiment, the microfiber array 100 is disposed on the surface of an end effector (i.e. the part of the robotic machinery used to move the semiconductor device). The microfiber array 100 can be formed then adhered to the end effector or, alternatively, molded directly to the surface of the end effector. A wafer can be placed on top of the microfiber array 100 with the weight of the wafer supported by the end effector. While supported by the end effector, the wafer can be moved with the microfiber array 100 providing sufficient friction to prevent the wafer from displacements out of the process specification relative to the end effector. The frictional properties of the microfiber array 100 minimizes contact between the end effector and the semiconductor device. Once transferred to a subsequent location, the wafer can be easily removed from the end effector in the vertical (i.e. normal) direction. Because the microfiber array 100 provides controllable, near-zero adhesion, the release of the device is accurate and repeatable. While this example embodiment discusses handling of semiconductor devices, the array 100 is suitable for handling a variety of objects with smooth and flat (or slightly curved) surfaces that are difficult to grip with conventional tools. Such objects may include optical components, lenses, glass, and sensitive or fragile objects.
The microfiber array 100 is fabricated using a molding process, where a curable polymer is poured into a mold having negative cavities in the shape of the fibers shown in
In one embodiment, the molded fiber array 100 with roughened tips 104 is produced from a perfluorinated elastomer, conventionally used in semiconductor fabrication environments. In other embodiments, the product may be produced from one of the following:
A. Thermosets:
B. Thermoplastics
The roughened surface can include plastic, metal, glass, or a natural surface. Moreover, the surface can be treated to produce an appropriate surface texture. Treatments can include machining, sawing, milling, cutting, planing, additive manufacturing processes, boring, broaching, turning, grinding, sanding, sand-blasting, sand-casting, perm mold casting, investment casting, hot rolling, forging, extruding, cold rolling, flame cutting, chemical milling, EDM, and plasma etching. After placed in contact with the roughened surface, the polymer is cured, with the tips 104 retaining the rough texture of the roughened surface. In one example embodiment, the roughened surface 106 of the tips 104 can have an Ra of 1-20 μm, where Ra is the profile roughness (or roughness average) of the surface 106. However, a person having skill in the art will appreciate that the surface roughness can be varied to alter the coefficient of friction of the microfiber array 100. In addition to surface roughness, the tip diameter, stem diameter, stem length, fiber spacing, tip height, and other parameters can be altered to adjust the coefficient of friction and adhesion of the microfiber array 100.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiments described herein.
Protection may also be sought for any features disclosed in any one or more published documents referred to and/or incorporated by reference in combination with the present disclosure.
This application claims the benefit under 35 U.S.C. § 119 of U.S. Provisional Application No. 63/128,903, filed Dec. 22, 2020, which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/064935 | 12/22/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63128903 | Dec 2020 | US |
