Dry adhesive for temporary bonding of semiconductor device

Abstract

To provide a dry adhesive for use in temporarily bonding a silicon wafer to a carrier during manufacturing and including a fiber array having micro scale or nano scale.SOLUTION: A dry-bonded microfiber array 100 comprising a plurality of fiber with enlarged distal ends is provided, which can be bonded to a surface of a silicon wafer and / or a carrier, and can be de-bonded using no chemicals nor heat, and does not remain on a wafer surface. In addition, adhesive force can be adjusted by introducing liquid such as water or isopropyl alcohol to an interface between a dry adhesive and a semiconductor device. The dry bonded microfiber array includes a plurality of fiber 101 attached to a backing layer, a carrier, or a substrate 102. The fiber is attached to the backing layer, the carrier, or the substrate at a substantially perpendicular angle, and each fiber includes a stem and an enlarged distal end 104.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] <Cross-reference to related applications> This application is a direct sequel to Provisional Application No. 63 / 049,314, filed July 8, 2020, 35 U.S.C. No. 119,999, filed on Oct. 1, 2002, and claims the benefit of S.C. 119, which provisional application is hereby incorporated by reference. Become part of.

[0002] <Statement regarding federally funded research> none.

[0003] The present invention relates generally to dry adhesives. More specifically, the present invention relates to a dry adhesive that is Micro-scale and nano-scale bonding used for temporary bonding of silicon wafers to carriers The present invention relates to a dry adhesive material containing nanoscale fiber arrays. [Background technology]

[0004] Semiconductor manufacturing involves several processing steps. For example, semiconductors are processed into processors. The silicon wafer undergoes cleaning, passivation, photolithography, etching, deposition, These processes include polishing, grinding, dicing, and chip / die packaging. The careful handling of wafers, dies and other semiconductor devices during the process Improve productivity, reduce production equipment footprint, and reduce / prevent particle contamination for high Wafer Level Packaging (WLP) process is required to maintain yield. With the increasing adoption of WLP, the need for proper wafer handling technology is increasing. In this process, die packaging occurs while the die is still on the wafer. The diversity of mobile devices using semiconductor chips / devices is making them thinner. To enable the handling of thin wafers for WLP, the manufacturing process The wafer may be temporarily bonded to a carrier or substrate. Since it is performed on the backside, temporary bonding occurs on the device side of the wafer, To prevent damage to the device side of the wafer, the bonding-debonding process (BD Generally, temporary bonding materials have the following characteristics: adhesion to a large surface, high speed, and Adhesion to the trace substrate and adhesion over a wide temperature range are required.

[0005] Temporary bonding can be accomplished by several techniques. In one example, the wafer and chip are bonded together. A liquid adhesive is used between the carrier. In adhesive bonding, a liquid thermoplastic The adhesive is spin coated onto the device side of the wafer and then heated for approximately 200-250 min. These additional steps reduce throughput and increase overall costs. Furthermore, at the completion of processing, the wafer may be exposed to chemicals, heat, or laser radiation. It must be debonded from the carrier using a method such as chemical debonding. In packaging, the wafers are exposed to solvents and are more likely to become contaminated. This is not time-efficient. Thermal debonding can cause the substrate to bend or warp due to the high temperature. Finally, laser debonding requires the use of transparent Although a carrier is required, the wafer detection and alignment system is mostly visual. This system may require modification to other process steps. In this procedure, pressure-sensitive adhesive tape is used. However, this type of tape is not suitable for debonding. may leave residue after processing, requiring further processing steps to remove the residue from the wafer. Furthermore, many of these existing technologies are limited by the inherent properties of the adhesive materials used. Since the combined strength is determined, it is not easy to adjust for a particular application.

[0006] Therefore, these limits can be adjusted to allow fine tuning of bond strength while minimizing contamination removal and wafer damage. Providing an efficient bonding / debonding process that reduces the chance of scratches It would be beneficial to develop a dry adhesive that overcomes this. Summary of the Invention

[0007] According to one embodiment of the present invention, the dry adhesive is applied to a smooth surface, such as the surface of a silicon wafer. The dry adhesive has an array of fibers that can adhere to any flat or patterned surface. In some embodiments, the substrate comprises an array of microscale or nanoscale fibers extending from a surface. The tip of each fiber is expanded and the tip is in contact with the surface of the wafer. The adhesive is removed by peeling the dry adhesive off the wafer or by This can be done by moving the wafer in a direction parallel to the surface. In addition, the dry adhesive can be moistened to As a result, it is possible to introduce liquids such as water and isopropyl alcohol. By adding a coating, the adhesive properties of the adhesive can be adjusted.

[0008] The dry adhesive may be formed as a thin film, tape, or directly assembled to the surface of the carrier. Dry adhesive debonding involves physically removing the wafer from the carrier. No chemicals or complicated processing steps are required other than the dry adhesive. Since the debonding process is not required, residues remaining on the wafer surface after debonding are significantly reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an image showing the structure of a dry adhesive according to one embodiment.

[0010] [Figure 2] FIG. 2 is a graph showing the adhesive strength of adhesives in dry and wet conditions. DETAILED DESCRIPTION OF THE INVENTION

[0011] In one exemplary embodiment, the dry-adhesive microfiber array 100 includes a backing It comprises a plurality of fibers 101 attached to a layer, carrier, or substrate 102. The fibers 101 are oriented at a substantially perpendicular angle to the backing layer, carrier, or substrate 10. 2. Each fiber has a stem 103 and an enlarged tip 104 (i.e., In one embodiment, the tip 104 is flat. The stem 103 and the tip 104 are arranged in a mushroom-like shape with a smooth surface. The radius a of the stem 103 (up to the connection point 105 with the portion 104) is However, in alternative embodiments, The radius of the stem 103 may vary along its length, with the stem near the backing layer 102 An embodiment is included in which the radius of the shaft 103 is enlarged. The tip 104 also has symmetry. and radially positioned to allow for easy access to silicon wafers, chips, dies, and semiconductor packages. The contact with the surface of the semiconductor device, such as a cage, is enhanced. The surface of 104 and the cross section of stem 103 are circular. However, an oval or elliptical shape and / or cross section may be employed. The shape of the lower side surface of 04 is linear, but alternatively, it may be convex with respect to the stem axial direction and the tip surface. The grooves may be curved or concave.

[0012] In an alternative embodiment, the dry adhesive 100 may have fibers on both sides, such as double-sided tape. In this configuration, the tape 100 is disposed on a carrier. The semiconductor device is then placed on the tape 100. When doing so, the manufacturer may remove the carrier from the device or the device from the carrier. For example, if the wafer is transferred to another carrier for subsequent processing steps, In this case, the wafer and tape 100 are removed from the carrier and placed on the surface of another carrier. The dry adhesive fiber array 100 may be used without losing adhesive strength even when removed. The dry adhesive 100 can be left attached to the wafer and then attached to another carrier. This eliminates handling steps involving the device side of the wafer.

[0013] In the bonding process, the plurality of fibers 101 of the dry adhesive 100 are bonded to the surface of the adhesive 100 by the bonding method of the present invention. As known in the art, they may be attached or otherwise bonded to the surface of the device. Specifically, the tip 104 of the fiber 101 comes into contact with the surface of the device and exerts adhesive force. The bond strength of the dry adhesive 100 is tailored to the specific process. If the device is subjected to a cleaning process that does not involve excessive force or rough handling A smaller bond strength may be used for the debonding. This reduces the chance of damaging the device during coupling. Coupling strength is a parameter of the fiber design. The parameters can be adjusted by changing the meter, and the parameters include fiber length, fiber radius, Backing layer thickness, tip diameter, tip height, angle between tip surface and side, fiber density, material In one exemplary embodiment, the fiber 101 is made of a material selected according to the art. It is made from polyurethane by molding processes known to those of ordinary skill in the art. In this exemplary embodiment, the dry adhesive 100 has a stem radius of 4 μm, a tip radius of 8 μm, and The fiber 101 may have a diameter and a length of 20 μm.

[0014] As explained earlier, the bond strength can be adjusted by changing the fiber properties. The presence of liquids such as water or isopropyl alcohol can also affect the adhesive properties of the dry adhesive 100. Although there is a liquid present, it does not directly bond like glue. Therefore, adhesive 100 is considered a dry adhesive, i.e., the liquid is not an adhesive. Rather, the liquid is reflected at the interface between the surface of the device and the tip 104 of the fiber 101. Figure 2 shows the difference between dry (bottom line) and wetted with isopropyl alcohol. The figure shows the adhesive strength of the dry adhesive 100 in two states: The y-axis of Figure 2 shows normal force in Newtons, and the x-axis shows individual measurements of the same dry adhesive 100. Figure 2 shows a series of 20 measurements followed by an additional 5 measurements 3 days later. Five additional tests were performed to measure the resilience of the fiber after exposure to isopropyl alcohol. As shown in FIG. 2, the presence of isopropyl alcohol inhibits the adhesion of the dry adhesive 100. In comparison, the adhesive strength in the normal direction is increased.

[0015] The difference in adhesive strength between the dry and wet states is utilized in the debonding step to bond the carrier Minimize the force required to remove the device from the The parts are bonded with dry adhesive 100, wetted with isopropyl alcohol, and then pressed. The presence of isopropyl alcohol increases adhesive strength. After processing, the adhesive The adhesive 100 may be dried using a stream of cold or heated air. The force is reduced and the semiconductor device can be easily removed from the carrier.

[0016] The dry adhesive 100 has advantages over existing mechanisms for bonding and debonding. For example, the dry adhesive 100 of the present invention provides bonding and debonding at room temperature. Bondability eliminates unnecessary heat exposure and potential changes in thermal expansion coefficients This prevents defects. Furthermore, every debonding process is different. (i.e., there is no standard debonding process), the ability to adjust bond strength is a valuable advantage. While ensuring that the mechanical removal process does not damage the device side of the wafer, Adhesion strength means that the attachment can be maintained throughout the process. In comparison with existing bonding mechanisms, the dry bond fiber array 100 has the following advantages: Improved throughput, simplified processing, low-temperature bonding process, and high yield do.

[0017] The features disclosed in the above description, the appended claims or the accompanying drawings are not intended to be limiting unless otherwise specified. in any tangible form or means for performing a disclosed function or achieving a disclosed result. are expressed in terms of the methods or processes for achieving them and, where appropriate, their characteristics may be used separately or in any combination to realize the present invention in various forms. In particular, one or more features of any embodiment described herein may be This embodiment may be combined with one or more features of any of the other embodiments described above.

[0018] Also included are one or more of the referenced and / or incorporated by reference in combination with this disclosure. Protection may be sought for any feature disclosed in any of the publications.

Claims

1. 1. An adhesive for temporarily bonding a semiconductor device to a carrier, comprising: A dry-adhesive microfiber array having a plurality of fibers with enlarged tips is provided. And, the tip is configured to contact a surface of the semiconductor device; The tip is configured to be released from the semiconductor device by mechanical action. Needed adhesive.

2. a liquid disposed at an interface between the tip and a surface of the semiconductor device. Item 1. The adhesive according to item 1.

3. 1. A method of bonding a semiconductor device to a carrier, comprising: Dry-bonded microfiber array having multiple fibers terminating in enlarged tips and The tip of the dry adhesive microfiber array is brought into contact with the surface of the semiconductor device. thereby attaching the semiconductor device to the dry-adhesive microfiber array; attaching the dry adhesive microfiber array to the carrier; A method comprising:

4. Mechanical action debonds the microfiber array from the silicon wafer. The method of claim 3 further comprising:

5. The mechanical action peels the microfiber array from the silicon wafer. The method of claim 4, comprising:

6. The mechanical action moves the silicon wafer in a direction parallel to the surface of the carrier.

5. The method of claim 4, comprising:

7. By varying the density of the plurality of fibers on the surface of the backing layer, The method of claim 3, further comprising adjusting the bond strength of the microfiber array. Law.

8. The bonding strength of the microfiber array can be adjusted by changing the surface area of ​​the tip. The method of claim 3 further comprising adjusting.

9. With the semiconductor device adhered to the dry-adhesive microfiber array, The method of claim 3 further comprising manipulating the position of the carrier.

10. 4. The method of claim 1 further comprising wetting the microfiber array to increase adhesion.

3. The method according to claim 3.

11. Drying the microfiber array before removing the semiconductor device from the carrier The method of claim 10 , further comprising:

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