Wafer debonding using flashlamp

Abstract

A method for attaching and detaching electronics structures during integrated circuit manufacturing is disclosed. A stack is formed including a carrier and an electronics structure. Between the carrier and electronics structure, a broadband absorber layer is provided. The broadband absorber layer includes broadband absorber material and polymer. A layer of ultraviolet (UV) light curable adhesive is also provided between the carrier and the electronics structure. UV light is directed through the carrier in order to cure the UV curable adhesive. The electronics structure can be processed while secured to the carrier. The electronics structure is removable from the carrier by transmitting a light pulse from a flashlamp through the carrier to heat the broadband absorber layer. The heat can decompose the polymer to permit removal of the electronics structure from the carrier.

Description

[0001] 3530742.006402

[0002] - 1 -

[0003] WAFER DEBONDING USING FLASHLAMP

[0004] Cross-Reference to Related Applications

[0005] This application is based on and claims priority to U.S. Provisional Application Serial No. 63 / 686,157 fded on August 22, 2024, which is hereby incorporated herein by reference.

[0006] Background

[0007] The present application relates to electronics manufacturing in general, and, in particular, to equipment and methods for attaching, processing, and detaching electronics structures (e.g., chips or wafers) during integrated circuit manufacturing.

[0008] During electronics manufacturing, electronics structures such as integrated circuit chips and wafers with metal and / or semiconductor components can be subjected to various processing steps, such as backside thinning, e.g., to reduce the thickness of a semiconductor layer or to deposit and / or bond backside electronic components. Prior to the processing steps (e.g., thinning), a base portion of the electronics structure can be bonded to a rigid carrier. For example, attaching a semiconductor wafer to a carrier substrate can be accomplished by placing an adhesive (e.g., an adhesive layer) directly between the semiconductor wafer and the carrier substrate. After the desired processing steps are complete, the processed semiconductor wafer is then detached from the carrier so that it can progress through further manufacturing stages (e.g., in different locations and / or involving different equipment).

[0009] Summary

[0010] In accordance with one example, a method for attaching and detaching wafers comprises disposing a broadband absorber layer comprising a broadband light absorbing material and a polymer on a carrier. Additionally, a layer of UV curable adhesive is disposed on a wafer. Then, the wafer with the UV curable adhesive layer is placed in contact with the broadband absorber layer to form a carrier stack. Then, the UV curable adhesive layer is cured by directing a UV light through the carrier. Then, the wafer is processed. Then, a light pulse from a flashlamp is sent through the carrier to facilitate separation of the wafer from the carrier.

[0011] In accordance with another example, a method for processing an electronics structure comprises providing a bonded stack comprising: a temporary carrier comprising a carrier body; a broadband absorber layer disposed on a first surface of the temporary carrier, the broadband absorber layer comprising at least a broadband light absorbing material and a

[0012] CORE / 3530742.006402 / 231151624.1 3530742.006402

[0013] - 2 - polymer; an electronics structure; and a UV-cured adhesive layer disposed between the broadband absorber and a first surface of the electronics structure. The method further comprises processing the electronics structure. The method further comprises, after processing the electronics structure, transmitting one or more pulses of light through the carrier body from a second side of the temporary carrier to reduce a cohesive strength of the polymer in the absorber layer.

[0014] In accordance with yet another example, a method for processing an electronics structure comprises providing an electronics structure and a temporary carrier comprising a carrier body that is substantially transparent to light emitted by the UV light source and by the pulsed light source. The method further comprises forming an absorber layer on a first side of the temporary carrier, the absorber layer being formed of at least a broadband light absorbing material and a polymer. The method additionally comprises disposing a layer of UV curable adhesive on a first side of the electronics structure. The method further comprises, after the steps of forming the absorber layer on the first side of the temporary carrier and disposing the layer of UV curable adhesive on the first side of the electronics structure, placing the layer of UV curable adhesive on the absorber layer. The method then comprises curing the UV curable adhesive by transmitting UV light through the carrier body from a second side of the temporary carrier, the second side generally opposing the first side of the temporary carrier. The method then comprises processing the electronics structure. The method further comprises, after processing the electronics structure, transmitting one or more pulses of light through the carrier body from a second side of the temporary carrier to reduce a cohesive strength of the polymer in the absorber layer

[0015] All features and advantages of the structures and methods provided herein will become apparent in the following detailed written description.

[0016] Brief Description of the Drawings

[0017] Figure 1 is a flow diagram of a method for attaching and detaching an electronics structure (e.g., wafer) from a carrier, according to one embodiment;

[0018] Figure 2A is a diagram of a carrier stack made by the method depicted in Figure 1;

[0019] Figure 2B shows the wafer being released from the reusable carrier from Figure 2 A;

[0020] Figure 3 is a block diagram of an apparatus for attaching and detaching an electronics structure (e.g., wafer) from a carrier, according to one embodiment; and

[0021] CORE / 3530742.006402 / 231151624.1 3530742.006402

[0022] - 3 -

[0023] Figure 4 illustrates a vacuum table for holding down a carrier stack, according to one embodiment.

[0024] Detailed Description

[0025] The present disclosure relates to improved methods for attaching electronics structures to carriers and detaching electronics structures from carrier in electronics manufacturing operations where the electronics structures are temporarily supported by carriers for processing.

[0026] Referring now to the drawings, and in particular to Figure 1, there is depicted a method for attaching a reusable carrier (broadly, a carrier) to a wafer (broadly, an electronics structure) and for detaching the reusable carrier from the wafer, according to one embodiment. It will be appreciated that the wafer is mentioned by way of example without limitation, and the method can be used in conjunction with electronics structures other than wafers without departing from the scope of the present application.

[0027] Starting at block 100, a layer 260 of broadband absorber (e.g., carbon black or other suitable broadband absorbing agent) in a polymer matrix (e.g., comprising one or more resins, such as a resin including cellulose, polyvinyl, polyester, and / or silicone material), referred to as broadband absorber material with polymer (broadly, an absorber layer), is disposed on a reusable carrier 280, as shown in block 110. As discussed in greater detail below, the reusable carrier 280 can have a transparent or at least partially light-transmissive body suitable for the methods discussed below. The absorber layer can be deposited on reusable carrier 280 using a variety of deposition techniques, including liquid form such as spin coating, casting, etc. and subsequently cured, and this can be followed by a drying step to remove excess solvent. Before or after the absorber layer is deposited on the carrier 280, a layer 270 of UV-curable adhesive is disposed on a wafer 290 (broadly, an electronics structure), as depicted in block 120. UV-curable adhesive layer 270 may be deposited on a side of the wafer 290 (e.g., a first side opposite a backside of the wafer) using a variety of techniques. For example, deposition of the UV-curable adhesive layer 270 can be achieved by directly depositing UV-curable adhesive layer 270 in liquid form on the first side of wafer 290 using spin coating, casting, etc. The layer 260 is at least partially transparent to UV light (e.g., a wavelength or wavelength spectrum generated by a suitable UV light source).

[0028] Desirably, the reusable carrier 280 is rigid and is thermally stable beyond 400°C. In addition, desirably the reusable carrier 280 is transparent to at least some or most (e.g., greater than 50%) of the light emitted by a flashlamp configured to emit broadband light

[0029] CORE / 3530742.006402 / 231151624.1 3530742.006402

[0030] - 4 - in wavelengths between about 200 nm and about 1.5 microns. It will be appreciated that, unless otherwise specified, the term “transparent” as used and described herein means at least partially light transmissive, and should be understood to encompass substantial transparency (e.g., greater than 50%) as well as absolute or near-absolute transparency (e.g., approximately 100%).

[0031] The reusable carrier 280 may be made of glass, such as Eagle XG glass made by Corning, Inc. or D263 glass made by Schott Glass, Inc. The reusable carrier 280 may also made of quartz or a ceramic material such as an oxide, nitride, or carbide, or a high- temperature polymer. The shape of the reusable carrier 280 can be round, rectangular, or any other shape.

[0032] Next, the wafer 290 (electronics structure) to which the UV-curable adhesive layer 270 has been deposited is placed on the reusable carrier 280 to which the absorber layer 260 has been deposited, such that the absorber layer 260 is adjacent to the adhesive layer 270 as depicted in block 130 and shown in Figure 2A. More broadly, the carrier 280 and electronics structure 290 are arranged in a stack with the adhesive layer 270 and absorber layer 260 therebetween. It will be appreciated that the adhesive layer 270 may be applied to the absorber layer 260 on the carrier followed by engaging the electronics structure with the adhesive layer to form the stack. Other methods and configurations can be used without departing from the scope of the present disclosure. For example, the stack can include other materials and / or layers.

[0033] The shape of the wafer 290 can be round, rectangular, or any other shape. The wafer 290 may comprise one or more semiconductor materials such as silicon or gallium arsenide. The wafer 290 may also comprise glass, quartz, ceramic, polymer, or a composite material. A vacuum or other source of positive or negative pressure may be applied to assist in bonding. Other configurations (e.g., other types of electronics structures) can be used without departing from the scope of the present disclosure.

[0034] UV light is then applied to cure the UV-curable adhesive layer 270. When the adhesive layer 270 is cured, the wafer 290 is attached to the reusable carrier 280, forming a temporarily bonded wafer stack, as depicted in block 140. As shown in Figure 2A, UV light from a UV source is directed from one side of the reusable carrier 280 (e.g., the side of the carrier to which the absorber layer 260 is not deposited) and at least partially through the absorber layer 260, to reach the UV-curable adhesive layer 270, as shown in Figure 2A.

[0035] CORE / 3530742.006402 / 231151624.1 3530742.006402

[0036] - 5 -

[0037] The UV light can be light between 150 nm and 500 nm. The source of UV light can be a light-emitting diode, a mercury arc lamp, an excimer lamp, a flashlamp, or other suitable source. At this point, the reusable carrier 280 is temporarily bonded (e.g., adhered) to wafer 290. As an alternative to UV curing, a suitable adhesive layer may be thermally cured such as by using an oven. Compression of the wafer stack may also be applied during thermal curing.

[0038] After the bonded stack is formed (e.g., when wafer 290 has been temporarily adhered to the reusable carrier 280), the backside of wafer 290 can be processed, as shown in block 150. Non-limiting examples of processing steps contemplated herein include wafer thinning, redistribution layer (RDL) buildup, deep reactive ion etching (DRIE), photolithography, sputtering, via formation, plating, device building, etc.

[0039] After all the desired wafer processing has been completed on wafer 290, wafer 290 is now ready to be debonded (e.g., detached) from the reusable carrier 280. This is accomplished by sending at least one light pulse (e.g., multiple light pulses) from a flashlamp 350 to heat up the absorber layer 260 for detaching wafer 290 from reusable carrier 280, as depicted in block 160. The broadband absorber material within the absorber layer 260 absorbs energy from the light pulse(s) from flashlamp 350 to generate heat and subsequently heats the polymer within the absorber layer 260. The heating of the polymer reduces the cohesive strength of broadband absorber material with polymer layer 260, thereby debonding the wafer 290 from the reusable carrier 280. The heating causes the polymer and / or broadband absorber material to decompose. It is possible that residue 220 from the decomposition of the polymer within the absorber layer 260 remains on portions of the reusable carrier 280 and / or the adhesive layer 270.

[0040] As shown in Figure 2B, the light pulse(s) can be emitted from one side of the reusable carrier 280 (e.g., the same nominal side of the carrier as the side where UV light was directed for curing the adhesive). After the light pulse(s), the reusable carrier 280 can be detached from wafer 290. The reusable carrier 280 can then be cleaned so the carrier is ready to be utilized again for another wafer after it has been sufficiently cleaned, e.g., in accordance with the steps described herein. It will be appreciated that the light pulse can be repeated one or more times and / or one or more light pulses can be modulated (e.g., intensity, duration) to generate a desired amount of heat for the debonding without causing damage to the other components in the stack, such as the wafer 290.

[0041] CORE / 3530742.006402 / 231151624.1 3530742.006402

[0042] - 6 -

[0043] Referring now to Figure 3, there is depicted a block diagram of an apparatus for performing detachment of a wafer (e.g., wafer 290) from a carrier (e.g., reusable carrier 280), according to one embodiment. As shown, an apparatus 300 includes a flashlamp control unit 301 and detaching unit 302. Flashlamp control unit 301 includes a capacitor-bank-charging power supply 310, a capacitor bank 320, an insulated gate barrier transistor (IGBT)-based switching device 330, a position sensor 340, a photodiode 360, a bolometer 370, an integrator 380, and a computer 390. Computer 390 includes a processor and various storage devices (e.g., including computer-readable non-transitory tangible storage medium) that are well-known to those skilled in the art. The capacitors in capacitor bank 320 are, for example, electrolytic capacitors. The capacitors in capacitor bank 320 may also be pulse discharge capacitors. Capacitor bank 320 may alternatively be switched with a silicon-controlled rectifier (SCR) switching device.

[0044] Capacitor bank 320 can be charged by capacitor-bank-charging power supply 310. Current from capacitor bank 320 is then discharged into flashlamp 350 via IGBT-based switching device 330 while IGBT-based switching device 330 is being switched on-and-off by position sensor 340 during the discharge. Position sensor 340 controls the gating of IGBT- based switching device 330 that, in turn, controls the switching of the discharge. The on-and- off switching of IGBT-based switching device 330 is intended to modulate the current flow from capacitor bank 320 to flashlamp(s) 350, which in turn switches flashlamp(s) 350 on-and- off. In other words, the switching of light pulses emitted by flashlamp(s) 350 is dictated by position sensor 340.

[0045] Detaching unit 302 includes a wafer feeding robot 352, a vacuum table 354, and a vacuum gripper 356. Prior to detaching, a dicing tape 410 may be attached to a bonded wafer stack (e.g., comprising the reusable carrier 280, absorber layer 260, adhesive layer 270, and wafer 290 shown in Figure 2A) with a film frame 420 to form a bonded wafer assembly, as shown in Figure 4. Wafer feeding robot 352 conveys the bonded wafer assembly to vacuum table 354. A vacuum is then applied on dicing tape 410 from vacuum table 354. Then, a light pulse from flashlamp 350 is utilized to illuminate the bonded wafer assembly from the side of reusable carrier 280 to detach processed wafer 290 from reusable carrier 280 in accordance with the methods described above.

[0046] At the separation station, vacuum gripper 356 separates reusable carrier 190 from the bonded wafer assembly, while the wafer 290 mounted on dicing tape 410 is being held down by vacuum table 354. Both reusable carrier 280 and wafer 20 on dicing tape 410 are

[0047] CORE / 3530742.006402 / 231151624.1 3530742.006402

[0048] - 7 - conveyed to a cleaning station to remove any residual adhesive. Residual adhesive may be removed with a wet process via solvent or a dry process with plasma and / or may be peeled off mechanically.

[0049] At this point, wafer 280 is fragile and the vacuum being applied to wafer 280 can be distributed across wafer 280 so as not to break it during removal. This may be accomplished with multiple suction cups 430 distributed across the surface of wafer 280, as depicted in Figure 4. Alternatively, the vacuum may be applied by a distributed vacuum, such as a vacuum table with perforated holes or grooves. Vacuum table 354 may have a polymer on its surface so that wafer 280 is not damaged during handling. As an alternative to a vacuum table and a vacuum gripper, an electrostatic chuck and electrostatic gripper may be used instead.

[0050] Further details about equipment for UV curing and debonding of carrier stacks is provided in U.S. Patent Application No. 18 / 605,697, fded on March 14, 2024, the contents of which are incorporated herein by reference in their entirety.

[0051] As has been described, the present disclosure provides methods for bonding electronics structures to carriers and for debonding electronics structures from carriers during manufacturing operations such as integrated circuit manufacturing.

[0052] While has aspects of the disclosure have been particularly shown and described with reference to example embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure.

[0053] CORE / 3530742.006402 / 231151624.1

Claims

3530742.006402- 8 -CLAIMSWhat is claimed is:

1. A method for attaching and detaching electronics structures comprising: disposing a broadband absorber layer comprising a broadband light absorbing material and a polymer on a carrier; disposing a layer of UV curable adhesive on an electronics structure; placing said electronics structure with said UV curable adhesive layer in contact with said broadband absorber layer to form a carrier stack; curing said UV curable adhesive layer by directing a UV light through said carrier; processing said electronics structure; and sending at least one light pulse from a flashlamp through said carrier to heat the broadband absorber layer to facilitate separation of said electronics structure from said carrier.

2. The method of claim 1, wherein the broadband absorber material is configured to generate heat upon absorbing the at least one light pulse to reduce the cohesive strength of the polymer in the absorber layer.

3. The method of claim 2, wherein the polymer is configured to decompose upon being heated when the at least one light pulse is transmitted.

4. The method of claim 1, wherein the at least one light pulse comprises a plurality of light pulses sent through said carrier to facilitate separation of said wafer from said carrier.

5. The method of claim 1, wherein the at least one light pulse is emitted by a flashlamp emitting broadband light in a spectrum ranging from approximately 200 nm to approximately 1.5 microns.

6. The method of claim 5, wherein the carrier is transparent to greater than 50% of the light emitted by the flashlamp.

7. A method for processing an electronics structure comprising: providing a bonded stack comprising:CORE / 3530742.006402 / 231151624.13530742.006402- 9 - a temporary carrier comprising a carrier body; a broadband absorber layer on a first side of the temporary carrier, the broadband absorber layer comprising at least a broadband light absorbing material and a polymer; an electronics structure; and a UV-cured adhesive layer disposed between the broadband absorber layer and a first surface of the electronics structure; and transmitting one or more pulses of light from a flashlamp through the carrier body from a second side of the temporary carrier to reduce a cohesive strength of the polymer in the broadband absorber layer.

8. The method of claim 7, wherein the broadband light absorbing material is configured to generate heat upon absorbing the one or more pulses of light to reduce the cohesive strength of the polymer in the absorber layer.

9. The method of claim 8, wherein the polymer is configured to decompose upon being heated when the one or more pulses of light are transmitted.

10. The method of claim 7, wherein the one or more pulses of light comprises multiple pulses of light from the flashlamp.

11. The method of claim 10, wherein the one or more pulses of light are emitted by the flashlamp emitting broadband light in a spectrum ranging from approximately 200 nm to approximately 1.5 microns.

12. The method of claim 11, wherein the carrier is transparent to greater than 50% of the light emitted by the flashlamp.

13. The method of claim 7, wherein the carrier body is substantially transparent to UV light.

14. A method for processing an electronics structure comprising: providing an electronics structure and a temporary carrier comprising a carrier body;CORE / 3530742.006402 / 231151624.13530742.006402- 10 - forming an absorber layer on a first side of the temporary carrier, the absorber layer being formed of at least a broadband light absorbing material and a polymer; disposing a layer of UV curable adhesive between the temporary carrier and the electronics structure; curing the UV curable adhesive to secure the electronics structure and temporary carrier in a stack by transmitting UV light through the carrier body from a second side of the temporary carrier, the second side generally opposing the first side of the temporary carrier; processing the electronics structure; and after processing the electronics structure, transmitting one or more pulses of light from a flashlamp through the carrier body from a second side of the temporary carrier to reduce a cohesive strength of the polymer in the absorber layer.

15. The method of claim 14, wherein the broadband light absorbing material is configured to generate heat upon absorbing the one or more pulses of light to reduce the cohesive strength of the polymer in the absorber layer.

16. The method of claim 15, wherein the polymer is configured to decompose upon being heated when the one or more pulses of light are transmitted.

17. The method of claim 14, further comprising detaching the electronics structure from the temporary carrier after the cohesive strength of the absorber layer is reduced.

18. The method of claim 14, wherein reducing the cohesive strength of the absorber layer causes the electronics structure to detach from the temporary carrier.

19. The method of claim 14, wherein the one or more pulses of light comprises multiple pulses of light from the flashlamp.

20. The method of claim 14, wherein the one or more pulses of light are emitted by the flashlamp emitting broadband light in a spectrum ranging from approximately 200 nm to approximately 1.5 microns.CORE / 3530742.006402 / 231151624.13530742.006402- 11 -21. The method of claim 20, wherein the carrier is transparent to greater than 50% of the light emitted by the flashlamp.CORE / 3530742.006402 / 231151624.1

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