Patent Application
20250070080
The present disclosure relates to methods of bonding chips including collectively bonding multiple chips.
Advanced packaging technologies demand precise and accurate control and placement of chips. For increased productivity/throughput, it is desirable in the art to bond multiple source chips to a bonding surface using multiple bonding heads at the same time. However, even when actuating multiple bonding heads as close to the same time as possible, the chip on one of the bonding heads will invariably contact the bonding surface just prior to the other chips on the other bonding heads. This initial contact by one chip on one bonding head will cause the carriage supporting the bonding surface to tilt about a center of gravity. The tilting of the carriage about the center of gravity induces increased or instable alignment for the chips on the remaining bonding heads.
Thus, there is a need in the art for a method and system for bonding multiple source chips to a bonding surface while eliminating or minimizing alignment error due to tilt about a center of gravity of the carriage.
A method for bonding chips includes actuating a first bonding head to apply a first force to a first chip while the first chip is contacting a bonding surface, thereby partially bonding the first chip to the bonding surface, actuating a second bonding head to apply a second force to a second chip while the second chip is contacting the bonding surface, thereby partially bonding the second chip to the bonding surface, and collectively actuating the first bonding head and the second bonding head to apply a third force to the first chip and the second chip such that the first chip and the second chip are completely bonded to the bonding surface. A magnitude of the third force is larger than a magnitude of the first force and a magnitude of the second force.
A system for bonding chips includes a first bonding head, a second bonding head, a substrate chuck configured to hold a substrate having a bonding surface, one or more processors, and one or more memories storing instructions, when executed by the one or more processors, causing the system to: actuate the first bonding head to apply a first force to a first chip while the first chip is contacting the bonding surface, thereby partially bonding the first chip to the bonding surface, actuating the second bonding head to apply a second force to a second chip while the second chip is contacting the bonding surface, thereby partially bonding the second chip to the bonding surface, and collectively actuating the first bonding head and the second bonding head to apply a third force to the first chip and the second chip such that the first chip and the second chip are completely bonded to the bonding surface. The third force is larger than the first force and the second force.
A method of manufacturing a plurality of articles, includes actuating a first bonding head to apply a first force to a first chip while the first chip is contacting a bonding surface, thereby partially bonding the first chip to the bonding surface, actuating a second bonding head to apply a second force to a second chip while the second chip is contacting the bonding surface, thereby partially bonding the second chip to the bonding surface, and collectively actuating the first bonding head and the second bonding head to apply a third force to the first chip and the second chip such that the first chip and the second chip are completely bonded to the bonding surface, wherein the third force is larger than the first force and the second force, and singulating the product substrate to produce the plurality of articles.
Implementations are illustrated by way of example and are not limited in the accompanying figures.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures can be exaggerated relative to other elements to help improve understanding of implementations of the invention.
The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and implementations of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent not described herein, many details regarding specific materials and processing acts are conventional and can be found in textbooks and other sources within the arts.
The chip source section 102 includes one or more sources for chips. For example, as shown in
The chip transfer and activation section 104 includes a transfer robot 126 that is able to lift and carry a substrate 114 to a second substrate chuck 130 in the bonding section 106. As understood in the art, the transfer robot 126 generally includes a hand and a robot arm that provides the degrees of motion to lift, carry, and place a substrate from one location to another, such as from one substrate chuck to another or from a substrate storage location to a substrate chuck. The transfer robot 126 may be any suitable device known in the art, for example robots such as the wafer handling robot RR756L15 provided by Rorze Corporation of Fukuyama-shi, Hiroshima-ken, Japan. The chip transfer and activation device 104 further includes an activation device 128. The activation device 128 is a device that prepares the chips being transferred for hybrid bonding. Hybrid bonding is a chip bonding technique in which electrically insulating (silicon dioxide) chip surfaces with recessed metallic (e.g. copper) pads are brought into contact with each other. The metallic pads are aligned with each other, while the electrically insulating surfaces are bonded to each other via direct contact. Heat is then applied to the bonded structure which causes the metallic pads to expand more relative to the electrically insulating material and contact each other, thus forming electrical connections between the chips. In an example embodiment, the activation device 128 may include a fluid source that applies for example deionized water and possibly a plasma source that activates the surface of the chips prior to them being carried by the transfer robot 126. Due to the materials of the chips (i.e., dielectric), when the activated chip is brought into contact with another chip a fusion bond will occur between the dielectric surfaces of the two chips.
The bonding section 106 includes the second substrate chuck 130 for receiving the substrate 114 that has been carried by the transfer robot 126 and has chips that have been activated by the activation device 128. The second substrate chuck 130 is also referred herein as an intermediate substrate chuck. The bonding section 106 may include a bridge 132 to which the intermediate substrate chuck 130 is attached. In an alternative embodiment, the intermediate substrate chuck 130 is attached to the base 114 instead of the bridge 132. The bonding section 106 also includes a plurality of bonding heads 134 attached to the bridge 132. In an embodiment, the bonding heads 134 may include a perimeter chuck region that holds the back surface of the chip 124 along the perimeter and a center pressure source that bows out a chip 124 held along the perimeter. In an embodiment, the bonding heads 134 may include a chucking portion that holds a chip 124 and a pressurized cavity that behind the chucking portion that bows out the chucking portion which causes the chip 124 held by the chucking portion to also be bowed. In an embodiment, the bonding heads 134 may include one or more actuators that move the chip chuck in at least the z direction towards the product substrate chuck 136. The bonding heads 134 may include one or more actuators that move the chip chuck in at least one of five directions (x, y, tip, tilt, and rotation). The actuators may be voice coil motors, piezoelectric motors, linear motors, nut and screw motors, piezo-actuated stages, brushless DC motor stages, DC motor stages stepper motors, which are configured to move the chip chuck to and from the product substrate chuck 136 and also applied a controlled force to the chip when it is in contact with the bonding surface 140. The chip chuck may hold the chip to the chucking surface using: vacuum; electrostatic forces; electromagnetic forces; mechanical gripping forces; or any other method of releasably holding the chip to the chucking surface of the bonding head 134. The bonding section 106 further includes a product substrate chuck 136 holding a product substrate 138. The product substrate 138 has a bonding surface 140. The bonding surface 140 in the illustrated example embodiment is the upper surface of the product substrate 138. In another example embodiment, the bonding surface may be a surface of a chip already on the product substrate 138. That is, the bonding described herein may be used to bond source chips onto the surface of a product substrate and/or may be used to bond source chips to the surface of a product chip on the product substrate. As shown in
The bonding section 106 may further include a plurality of alignment devices 146 and a plurality of transfer heads 148, all of which are also carried by the carriage 142. Each of the plurality of transfer heads 148, may include any one of a variety of methods of holding the chips including but not limited to: a Bernoulli chuck; a suction nozzle; an electrostatic chuck; an edge gripping chuck; a latching mechanism; or any method of releasably holding a chip. Each of the plurality of transfer heads 148, may include an actuator for moving in at least the z direction towards and away from the bridge 132. The plurality of alignment devices 146 are used to examine the alignment of chips on the plurality of bonding heads 134 after the chips have been transferred to the plurality of bonding heads 134. Each alignment device may be a microscope, a camera, an interferometer, or any sort of measuring device that is capable of measuring the position of each chip on a nanometer scale. The information provided by the plurality of alignment devices 146 will allow the operator to know whether each chip is at a target position within an acceptable amount of error. The plurality of alignment devices 146 may be any suitable device known in the art, for example a 20× microscope with 5 megapixel camera such as a CI-5MGMCL from Canon Inc., of Tokyo Japan. The plurality of transfer heads 148 are used to transfer the chips from the intermediate substrate 116 that is held by the intermediate substrate chuck 130 to the plurality of bonding heads 134. Each of the plurality of transfer heads 148 may include any one of a variety of methods of holding the chips including but not limited to: a Bernoulli chuck; a suction nozzle; an electrostatic chuck; an edge gripping chuck; a latching mechanism; or any method of releasably holding a chip. Each of the plurality of transfer heads 148, may include an actuator for moving in at least the Z direction towards and away from the bridge 132.
The number of bonding heads of the plurality of bonding heads is at least two, but can be as many as 8 or 16. The arrangement of the plurality of bonding heads may be in the form of columns and rows such as one by two, two by one, two by two, one by three, three by one, two by three, three by two, three by three, four by one, one by four, four by two, two by four, three by four, four by three, four by four, etc. In other words, the number of bonding heads may be represented as “m×n” where m is from 1 to 4 and n is from 1 to 4. In the example shown in
The bonding section 106 may further include a first microscope 150 on the carriage 142 and a second microscope 152 on the bridge 132. The first microscope 150, being on the carriage 142, is moveable along the base 144 with the plurality of transfer heads 148, the product substrate chuck 136 and the plurality of alignment devices 146. The first microscope 150 is aimed upwardly in a direction toward the intermediate substrate chuck 130. The first microscope 150 functions to measure positions of the plurality of chips on the intermediate substrate 116. The second microscope 152 faces downward in a direction toward the product substrate chuck 136. The second microscope 152 functions to measure positions of the chips on the product substrate 138. Each of the first and second microscopes may be suitable device known in the art, for example a 20× microscope with a 5 megapixel camera such as a CI-5MGMCL from Canon Inc., of Tokyo Japan.
The bonding system 100 may be regulated, controlled, and/or directed by one or more processors 154 (controller) in communication with one or more components and/or subsystems such as the chip source section 102, the chip transfer and activation section 104, the bonding section 106, the source chuck 110, the FOUP 112, the transfer robot 126, the activation device 128, the intermediate substrate chuck 130, the plurality of bonding heads 134, the product substrate chuck 136, the carriage 142, the plurality of alignment devices 146, the plurality of transfer heads 148, the first microscope 150, and the second microscope 152. The processor 154 may operate based on instructions in a computer readable program stored in a non-transitory computer memory 156. The processor 154 may be or include one or more of a CPU, MPU, GPU, ASIC, FPGA, DSP, and a general-purpose computer. The processor 154 may be a purpose-built controller or may be a general-purpose computing device that is adapted to be a controller. Examples of a non-transitory computer readable memory include but are not limited to RAM, ROM, CD, DVD, Blu-Ray, hard drive, networked attached storage (NAS), an intranet connected non-transitory computer readable storage device, and an internet connected non-transitory computer readable storage device. All of the steps described herein may be executed by the processor 154.
The source substrate 114, having the activated chips 124, is then chucked to the second substrate chuck 130. Next, once the source substrate 114 having the activated chips 124 has been mounted to the second substrate chuck 130, the first microscope 150 may be used to measure the position of the plurality of chips 124. This step may be performed by moving the carriage 142 along the base 144 until the first microscope 150 is beneath the plurality of chips 124. If the feedback from the first microscope 150 shows that the certain chips of the plurality of chips 124 are outside of an acceptable amount of error, then a replacement source substrate 114 would need to prepared. If the feedback from the first microscope 150 shows that the plurality of chips 124 are located at the proper positions within an acceptable amount of error, the method may proceed.
A first set of chips from the source substrate 114 may be then transferred to the plurality of bonding heads 134. This step may be performed by first moving the carriage 142 along the base 144 until the plurality of transfer heads 148 are beneath the plurality of chips 124. The plurality of transfer heads 148 may include the same number of heads with the same pitches as the plurality of bonding heads 134. The plurality of transfer heads 148 are configured to mirror the plurality of bonding heads 134 so that the plurality of transfer heads 148 can transfer up to the same number of chips that the plurality of bonding heads are capable of bonding in a single bonding step. The plurality of transfer heads 148 may pick up a first set of chips from the source substrate 114 by activating a vacuum force, for example. The plurality of transfer heads 148 may maintain the vacuum force while the plurality of transfer heads 148 carrying the first set of chips are moved via the carriage 142 to a position underneath the plurality of bonding heads 134. Either the plurality of transfer heads 148 or the plurality of bonding heads 134 moves toward the other (or both move simultaneously) until the first set of chips are at a position to be transferred to the plurality of bonding heads 134. Once close enough, the vacuum force on the plurality of transfer heads 148 may be terminated and a vacuum force of the plurality of bonding heads 134 may be activated, thereby transferring the first set of chips to the plurality of bonding heads 134. The moment after all of these steps have been performed, which is just prior to step S202, is the moment shown in
With the above-noted initial steps completed, the bonding method 200 is ready to begin the above-noted step S202 of actuating a first bonding head to apply a first force to a first chip while the first chip is contacting a bonding surface. The first force may be applied downwardly in the Z direction. Beginning with step S202, all of the steps occur within a portion 160 of bonding system 100.
Next, the bonding method 400 may proceed to step S404 where each chip of the of the plurality of chip 124 are bowed. The bowing of the chips may be performed by back pressure control either directly applied to the chip or chip holding chuck of each bonding head 134 as described in U.S. patent application Ser. No. 18/326,473 filed on May 31, 2023 which is hereby incorporated by reference.
After all of chips 124 on the bonding heads 134 have been bowed, the method may proceed to step S406 where a first chip 124a of the bowed chips 124 is contacted with the bonding surface 140 with an initial force Fi, without any of the other bowed chips 124b, 124c, 124d contacting the bonding surface. The initial force Fi may be applied downwardly in the Z direction by actuating the bonding head holding the chip.
After completing step S406, which, as noted above is an example embodiment corresponding to the completion of step S202 in
In step S408 another one of the bowed chips comes into contact with the bonding surface with an initial force Fi, without allowing any of the other bowed chips that have not yet come into contact with the bonding surface to come into contact with the bonding surface.
Next, the method may proceed to step S410 where step S408 is repeated until all of the remaining bowed chips not yet partially bonded with the bonding surface are placed into contact with the bonding surface with an initial force Fi. That is, in the example embodiment, the same process of contacting the first chip 124a and the second chip 124b is applied to the third chip 124c and then subsequently applied to the fourth chip 124d, one at a time.
Returning to the overall bonding method 300, after the second chip has been contacted with the bonding surface by applying the second force (i.e., an initial force), or in the case of the example embodiment bonding method 400, after step S410 where all of the bowed chips have been partially bonded with the bonding surface, the bonding method 300 may proceed to step S206 where the first and second bonding heads are collectively actuated (e.g., the first bonding head and the second bonding head are operated together) to apply a third force to the first chip and the second chip such that the first chip and the second chip are completely bonded to the bonding surface, where the third force is larger than the first force and the second force. Completely bonded in the context of hybrid bonding is when the dielectric surface of the chip that is aligned with the dielectric surface of the bonding surface of the product surface is conforming to the dielectric surface of the bonding surface. The chip and the bonding surface includes non-dielectric material that is not bonded while the chip is completely bonded to bonding surface. At a later time the completely bonded chip will be annealed at which point the non-dielectric material will form bonds. That is, the magnitude of the first force is larger than the magnitude of the first force and the magnitude of the second force. Step S206 corresponds to step S412 of the example embodiment bonding method 400. As used herein, “collectively” may include actuating all of bonding heads to apply the third force at the same moment, may include actuating all of bonding heads to apply the same third force within 1 second of each other, may include completely bonding of all chips currently on the bonding heads within 1 to 3 seconds, and may include any amount of time to complete the bonding of all of the chips currently on the bonding heads. That is, whatever amount of time it takes for all of chips of the set of chips on the bonding heads to have completely bonded may be considered collective, as long as the transfer head has not yet brought over another set of chips for bonding.
The third force is a conforming force Fc that is strong enough to fully flatten the bowed chips so that the entire chip surface area bonds to the bonding surface. As noted above, the magnitude of the initial force Fi may be 5-10% of the magnitude of the conforming force Fc (i.e., Fi=0.05Fc to 0.1Fc). The conforming force Fc may be directed downwardly in the Z direction and have a magnitude of 2-5 N per chip for 10 mm by 10 mm and 100 μm Silicon chips. Thus, in the overall bonding method 300, after applying the first force (initial force) to the first chip and applying the second force to the second chip (another initial force), the third force (conforming force) is applied collectively to both the first and second chips. In the example embodiment bonding method 400, in step S412, the conforming force Fc is collectively applied to all of the bowed chips contacting the bonding surface, thereby fully bonding each of the bowed chips to the bonding surface. In particular, in the illustrated embodiment, after all four of the chips 124a, 124b, 124c, 124d have contacted with the bonding surface 140 with in the bowed state using the initial forces to partially bond the chips to the bonding surface, the conforming force is collectively applied to all four of the chips 124a, 124b, 124c, 124d.
In an alternative parallel embodiment, steps S404, S406, and S408 are performed in parallel for each bonding head, and step S412 is only performed once all of the chips have finished step S408. In the alternative parallel embodiment, step S404 may be skipped. In the case where step S404 skipped, the chip is not bowed and the initial force would cause less than the entire surface area of the chip to bond to the bonding surface, while the conforming force would cause the chip to completely conform/bond with the bonding surface.
After all of the chips 124 have been fully bonded to bonding surface after step S412, the bonding method may proceed to step S414 where all of the bonded chips are released from the bonding head. That is, with the chips being bonded on one side of the chip to the bonding surface, the bonding heads may release the opposite side of the chip being held by the bonding heads. Once released, the bonding process has been completed.
After process of bonding chips to bonding surface is complete (which may include many cycles of the bonding method 200, 400 to bond hundreds, thousands, or tens of thousands of chips), the product substrate 138 is removed from the chip bonding section 106 by for example the transfer robot 126 or the like. The product substrate may then be subjected to an annealing process (which may include one or both of heat and pressure) in which the hybrid bonding process is completed. The product substrate may be subjected to additional processes in which additional chips are added to the product substrate before or after the annealing process. The product substrate may then be subjected to additional processes, such as: singulation, testing, encapsulation, etc., which are used to produce a plurality of articles from the product substrate.
Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required and that one or more further activities can be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed. While the above description, was described in the context of hybrid bonding process, other bonding processes may be used such as soldering, flip-chip bonding, ball grid array bonding, or another process that used to form a plurality of electrical connections between chips.
Benefits, other advantages, and solutions to problems have been described above with regard to specific implementations. However, the benefits, advantages, solutions to problems, and any feature(s) that can cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.
The specification and illustrations of the implementations described herein are intended to provide a general understanding of the structure of the various implementations. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Separate implementations can also be provided in combination in a single implementation, and conversely, various features that are, for brevity, described in the context of a single implementation, can also be provided separately or in any subcombination. Further, reference to values stated in ranges includes each and every value within that range. Many other implementations can be apparent to skilled artisans only after reading this specification. Other implementations can be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change can be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.
