Adaptive die attachment tool, die attachment system, and method of using the same

Abstract

A die attachment system is provided. The die attachment system comprises: a support structure for supporting a substrate; a die supply source comprising a plurality of dies for attachment to a substrate; and a bond head for bonding the die from the die supply source to the substrate. The bond head comprises a bond tool having a contact portion for contacting the die during transfer from the die supply source to the substrate. The bond head comprises a spring portion coupled to the bond tool, wherein the spring portion is configured to be compressed while pressing the die against the substrate using the contact portion of the bond tool.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 727,395 filed September 5, 2018, the contents of which are incorporated herein by reference.

[0003] The present invention relates to a system and method for attaching a die to a substrate, and in particular to an improved compliant die attachment tool used in relation to attaching a die to a substrate without picking the die from a die supply source. Background Technology

[0004] With regard to the placement of dies on a substrate (e.g., semiconductor die attachment operations), many conventional applications utilize a "pick and place" operation. In such an operation, a die is "picked" from a semiconductor wafer or another die supply source, and then the die is moved to a target substrate (and "placed" thereon). This operation may also utilize one or more transfer sections between a "pick" tool and a "place" tool.

[0005] In other die attachment operations, a die supply source (e.g., a wafer containing multiple dies) may be positioned between the bond tool and the substrate. The bond tool may be used to press the die against the substrate while the die is still secured to the film / foil of the die supply source. Thus, the die attachment operation is performed without any "picking" or "placement" actions. However, this operation tends to suffer from numerous defects, such as poor control of the bond force between the bond tool and the die during the bonding operation.

[0006] Therefore, it would be desirable to provide an improved die attachment system and a related method to overcome one or more defects of conventional die attachment systems.

[0007] According to an exemplary embodiment of the present invention, a die attachment system is provided. The die attachment system comprises: a support structure for supporting a substrate; a die supply source comprising a plurality of dies for attachment to a substrate; and a bond head for bonding the die from the die supply source to the substrate. The bond head comprises a bond tool having a contact portion for contacting the die during transfer from the die supply source to the substrate. The bond head comprises a spring portion coupled to the bond tool, wherein the spring portion is configured to be compressed while pressing the die against the substrate using the contact portion of the bond tool.

[0008] According to another exemplary embodiment of the present invention, a method for attaching a die to a substrate is provided. The method comprises the steps of: providing a die supply source comprising a plurality of dies for attachment to a substrate, wherein the die supply source is positioned between a support structure supporting the substrate and a bond tool; and moving a bond tool, which is carried by a bond head, downward so that a contact portion of the bond tool contacts the die, in order to transfer the die from the die supply source to the substrate. The bond head comprises a spring portion coupled to the bond tool, wherein the spring portion is configured to be compressed while pressing the die against the substrate using the contact portion of the bond tool. Brief explanation of the drawing

[0009] The present invention is best understood through the following detailed description when read in conjunction with the accompanying drawings. In accordance with general convention, it is emphasized that the various features of the drawings are not scaled. Conversely, the dimensions of the various features are arbitrarily enlarged or reduced for clarity. FIGS. 1a to 1c are block diagrams illustrating elements of a die attachment system according to an exemplary embodiment of the present invention. FIGS. 2a to 2d are a series of side cross-sectional views of a part of a die attachment system according to an exemplary embodiment of the present invention. Specific details for implementing the invention

[0010] Specific die attachment applications do not utilize pick-and-place operations. For example, a die supply source (e.g., a wafer containing multiple dies, such as an LED wafer, or another source of LED dies) may be located between the bond tool and the substrate. The dies contained in the die supply source (e.g., LED dies) may be attached to a film / foil, etc.

[0011] According to a specific exemplary aspect of the present invention, after alignment between a bond tool, a die to be attached, and a placement location on a substrate, the bond tool presses the die against the placement location on the substrate. An adhesive on the lower surface of the die (and / or the placement location on the substrate) is then provided to secure the die to the substrate. Such a bond tool may include a plurality of pins for contacting the die (e.g., operable pins that can operate independently of each other) in connection with transfer from the die supply source to the substrate.

[0012] As used herein, the term “die” is intended to refer to any structure comprising (or configured to be included in at a later stage) a semiconductor chip or die. Exemplary “die” elements include a bare semiconductor die comprising a bare LED semiconductor die, a semiconductor die on a substrate (e.g., a lead frame, PCB, carrier, semiconductor chip, semiconductor wafer, BGA substrate, semiconductor element, etc.), a packaged semiconductor device, a flip chip semiconductor device, a die embedded in a substrate, etc.

[0013] According to a specific exemplary embodiment of the present invention, in a die attachment system, a bond head is used to attach a die to a substrate. The bond head includes a holder (e.g., a shaft portion) and a bond tool (e.g., a needle) coupled to the holder. The bond tool may be suspended from the housing of the bond head and may move in at least one direction (e.g., along the vertical z-axis of the die attachment system). In this way, the housing portion of the bond head is separated from the bond tool. The bond head includes a detection system (e.g., a sensor for detecting the amount of compression of a spring portion while bonding a die to a substrate) to detect (e.g., measure) the movement of the bond tool relative to the bond tool housing. The die attachment system controls the movement of the bond tool based on a signal transmitted by the detection system. In a specific embodiment of the present invention, such a detection system or sensor is not used. For example, control of the bond tool may be achieved using other information that may be available. For example, the motor current of a z-actuator (as part of a motion system, driving the bond head along the z-axis—see element (124) in FIG. 2a through 2d) can be used to determine the height of the bond tool and / or to control the movement of the bond tool.

[0014] An exemplary situation for the use of a die attachment system includes (i) a bond head that may include a detection system capable of measuring the relative position between the bond tool housing and the bond tool; and (ii) a situation in which the bond head may be used without such a detection system.

[0015] An exemplary objective of various embodiments of the present invention comprises one or more of: (i) reducing the impact mass applied by a bond tool to a die while attaching a die to a substrate; (ii) controlling the force applied by the bond tool to the die being attached; (iii) controlling the amount of compression of a spring portion of a bond head; (iv) determining the point of impact of the die on the substrate during die attachment; and (v) determining the height of impact of the die on the substrate.

[0016] FIG. 1a illustrates a die attachment system (100). The die attachment system (100) comprises a support structure (102) for supporting a substrate (104), a die supply source (106) comprising a plurality of dies (106a) configured to be attached to the substrate (104), and a bond head (108) configured to be driven along the z-axis using a motion system (124), wherein the bond head (108) comprises a bond tool (120) for contacting the die (106a) during the transfer of the die (106a) from the die supply source (106) to the substrate (104). The die attachment system (100) also comprises a bond head support (126) and a supply support (128). A bond head support (126) and a supply support (128) are each mounted on a machine structure (130) so that the bond head support (126) and the supply support (128) can move independently relative to the machine structure (130). The bond head support (126) supports an intermediate support structure (132) (movable relative to the bond head support (126)), and the intermediate support structure (132) supports a movable bond head (108). The intermediate support structure (132) carries a camera (134) (and other vision system components) for use in connection with alignment and / or inspection operations. A die supply source (106) is movably mounted on the supply support (128). In an exemplary embodiment of the invention illustrated in FIG. 1a (and refer to FIG. 1b), during the die attachment operation, the die supply source (106) is positioned between the bond tool (120), which is supported by the support structure (102), and the substrate (104). FIG. 1b is a side cross-sectional view of an element of the die attachment system (100), in which the camera (134) and the bond tool (120) are positioned on the substrate (104). Two "bonded" dies (106a') are bonded to the substrate (104) at their respective bonding locations, and the bond tool (120) is illustrated as being bonded to another die (106a) at a third individual bonding location on the substrate (104).FIG. 1c illustrates a block diagram of an example of a bond tool (120). More specifically, the bond tool (120) may include at least one pin (120b) for contacting the die (106a) in connection with transfer from the die supply source (106) to the substrate (104). Additionally, as shown in FIG. 1c, the bond tool (120) may include a plurality of pins (120b) for contacting the die (106a) in connection with transfer from the die supply source (106) to the substrate (104). Each of the plurality of pins (120b) may be movable (e.g., along a vertical axis) relative to the rest of the bond tool (120), either detachably or collectively, to transfer the die (106a) to the substrate (104). Of course, a bond tool (120) comprising one or more pins (120b) (as illustrated in FIG. 1c) is an example of a bond tool (120). In another embodiment of the invention, the bond tool (120) may not include pins (120b), but may be able to deliver a die (106a) without pins (120b). Furthermore, FIGS. 2a through 2d illustrate a bond tool (120) without pins (120b), in which a single structure is driven along the z-axis. In an embodiment of the invention in which the bond tool (120) comprises a plurality of pins (120b), these pins may include additional actuator(s) for moving the pins (120b) separately (or together) as needed to achieve die delivery.

[0017] FIGS. 2a through 2d are a series of side cross-sectional views of specific configurations of elements of a die attachment system (100). As provided above, the die attachment system (100) includes a support structure (102) for supporting a substrate (104) and a die supply source (106) comprising a plurality of dies (106a) for attaching to the substrate (104) (e.g., the die supply source comprises an LED wafer and the plurality of dies are a plurality of LED dies). For example, the die supply source (106) comprises a flexible film (106b), wherein the plurality of dies (106a) are attached to the flexible film (106b). The die attachment system (100) includes a bond head (108) for bonding the dies (106a) from the die supply source (106) to the substrate (104). The bond head (108) includes a bond tool (120) having a contact portion (120a) for contacting the die (106a) during transfer from the die supply source (106) to the substrate (104) (e.g., including a needle, a pin, a plurality of pins individually movable along a vertical axis, etc.) (wherein the bond tool (120), such as a plurality of pins, contacts the die (106a) in connection with transfer from the die supply source (106) to the substrate (104). The bond head (108) includes a spring portion (118) coupled to the bond tool (120), wherein the spring portion (118) is configured to compress during the pressing of the die (106a) against the substrate (104) using the contact portion (120a) of the bond tool (120). Thus, the bond tool (120) is spring-loaded. In the example illustrated in FIGS. 2a through 2d, the connection between the spring portion (118) and the bond tool (120) is made through a shaft portion (114) (e.g., a needle holder) included in the bond head (108). The bond tool (120) is fixed (directly or indirectly) to the shaft portion (114). The shaft portion (114) is configured to move along a vertical axis (e.g., the z-axis of the die attachment system (100)).

[0018] More specifically, the bond head (108) includes a z-actuator portion (110) coupled (directly or indirectly) to the bond tool housing (112). The bond head (108) forms an internal opening (108a) that enables movement of the shaft portion (114) along the aforementioned vertical axis. A spring portion (118) is coupled to a portion of the shaft portion (114). A plurality of linear guides (116) (e.g., play-free, frictionless linear guides) are coupled between the shaft portion (114) and the bond tool housing (112). A stepped portion (114b) of the shaft portion (114) is configured to move within a portion of the internal opening (108a). The shaft portion (114) includes a pretensioned conical portion (114a) configured to rest against an angled inner surface of the internal opening (108a). More specifically, the pretensioned conical portion (114a) is under "tension" due to the force provided by the spring portion (118) pushing against the other stepped portion (114c) of the shaft portion (114).

[0019] Referring particularly to FIG. 2a, the bond tool (120) is positioned over one of the plurality of dies (106a) (i.e., the die supply source (106) is positioned between the substrate (104) and the bond tool (120). In FIG. 2a, the bond tool (120) (coupled directly or indirectly to the shaft (114)) is in a lower position within the range of motion of the bond tool (120) relative to the bond tool housing (112). In FIG. 2b, the bond head (108) is moved downward so that the contact portion (120a) of the bond tool (120) contacts the die (106a) of the die supply source (106). The bond head (108) continues to move downward so that the film (106b) begins to move downward toward the substrate (104) (i.e., flex). The spring portion (118) uses the contact portion (120a) of the bond tool (120) to begin compression during contact between the contact portion (120a) and the die (106a) before pressing the die (106a) against the substrate (104) (i.e., the compression of the spring portion (118) is shown as the difference between FIG. 2b and FIG. 2c).

[0020] FIG. 2c illustrates a die (106a) that is pressed against a substrate (104) by a bond tool (120) (e.g., the force is equal to the product of the displacement of the bond tool (120) and the spring constant of the spring part (118). That is, the bond tool (120) (which is directly or indirectly coupled to the shaft (114)) is now in an upper position within the range of motion relative to the bond tool housing (112). The displacement of the bond tool (120) is measured by a displacement measuring device (122) included in the z-actuator part (110) (e.g., the displacement measuring device may include a position sensor). A displacement signal (provided, for example, by a displacement measuring device (122)) is used by a motion system (124) (for moving the bond head (108)) to stop the z-axis movement of the bond head (108) at a position corresponding to a predefined downward pressure (i.e., the position shown in FIG. 2c). It should be understood that such a displacement signal can be used in "real time" (in relation to the current die attachment operation) or that such a displacement signal can be used in relation to a subsequent die attachment operation.

[0021] After the bonding time (also referred to as the "dwell" time, i.e., the time while the bond tool (120) maintains a preset downward pressure), the motion system (124) begins to raise the bond head (108) upward as shown in FIG. 2d. The die (106a) is now bonded to the substrate (104) (e.g., by a holding force by an adhesive contained on the substrate (104) and / or the die (106a)) (wherein at least one of the bonding positions of the die (106a) and the substrate (104) contains an adhesive for securing the die (106a) to the bonding position after transfer from the die supply source (106) to the substrate (104)). That is, when the bond tool (120) is moved upward (carried by the bond head (108)), the die (106a) is released from the film (106b) through the "jerk" movement of the bond tool (120). This jerk movement of the bond tool (120) is caused by the upward movement of the bond tool (120) as it returns to a lower position within the range of motion relative to the bond tool housing (112) due to spring force.

[0022] The die attachment system (100) is configured to control the lowering of the bond tool (120) (included in the bond head (108)) while bonding the die (106a) to the substrate (104) based on feedback from the displacement measuring device (122). For example, the displacement measuring device (122) includes a position sensor for detecting the amount of compression of the spring part (118) during the bonding of the die (106a) to the substrate (104).

[0023] The displacement measuring device (122) may vary within the scope of the present invention and may operate in relation to the motion system (124). Additionally, predetermined data may be used in relation to the operation of the motion system (124). Such predetermined data may be related to (i) the amount of compression of the spring portion (118) to provide a desired bonding of the die (106a) to the substrate (104), the amount of compression being related to at least one z-axis position of (a) a portion of the bond head (108) and (b) a portion of the bond tool (120); and / or (ii) the magnitude of the bonding force to be applied to provide a desired bonding of the die (106a) to the substrate (104), the magnitude of the bonding force being related to at least one z-axis position of (a) a portion of the bond head (108) and (b) a portion of the bond tool (120).

[0024] Exemplary advantages of conventional tools (and related die attachment systems) may include: (i) reducing the force applied to the die during die attachment; (ii) optimizing output by minimizing travel distance; (iii) enabling accurate height teaching in the system; and (iv) detecting irregular height changes that may cause process errors. Examples include the detection of defects on the substrate, the detection of missing dies on the source / substrate, and the detection of system malfunctions.

[0025] Although the present invention has been described and illustrated primarily in relation to die attachment operations without a "pick" operation, it is not limited thereto. The present invention has broad applicability in the semiconductor bonding industry, including die attachment machines (sometimes referred to as die bonders) or other packaging machines (e.g., flip-chip machines / operations, advanced packaging operations, etc.).

[0026] Although the present invention has been described and illustrated with respect to exemplary embodiments, it should be understood by those skilled in the art that various other modifications, omissions, and additions may be made without departing from the concept and scope of the invention. Rather, various modifications may be made in detail within the scope and range of the equivalents of the claims without departing from the invention.

Claims

Claim 1 A die attachment system comprising: a support structure for supporting a substrate; a plurality of dies for attaching to the substrate; a bond head for bonding the die from the die supply source to the substrate, wherein the bond head comprises a bond tool having a contact portion for contacting the die during transfer from the die supply source to the substrate, and the bond head comprises a spring portion coupled to the bond tool, wherein the spring portion is configured to be compressed while pressing the die against the substrate using the contact portion of the bond tool; and a sensor for detecting the amount of compression of the spring portion while the die is bonded to the substrate, wherein the die supply source is located between the substrate and the bond tool, and the die is compressed against the substrate by the bond tool in relation to the bonding operation. Claim 2 A die attachment system according to claim 1, wherein the spring portion begins compression during contact between the contact portion and the die before pressing the die against the substrate using the contact portion of the bond tool. Claim 3 delete Claim 4 A die attachment system according to claim 1, wherein the die attachment system is configured to control the lowering of the bond tool while the die is bonded to the substrate based on feedback from the sensor. Claim 5 A die attachment system according to claim 1, wherein predetermined data is determined, and said predetermined data is related to the compression amount of said spring portion to provide a preferred bonding of said die to said substrate. Claim 6 In claim 5, the compression amount is a die attachment system associated with at least one z-axis position of (i) a part of the bond head and (ii) a part of the bond tool. Claim 7 A die attachment system according to claim 1, wherein predetermined data is determined, and said predetermined data is related to the magnitude of a bond force to be applied to provide a desirable bonding of the die to the substrate. Claim 8 A die attachment system according to claim 7, wherein the magnitude of the bonding force is associated with at least one z-axis position of (i) a part of the bond head and (ii) a part of the bond tool. Claim 9 A die attachment system according to claim 1, wherein the bond tool comprises at least one pin for contacting the die in connection with transfer from the die supply source to the substrate. Claim 10 A die attachment system according to claim 1, wherein the bond tool comprises a plurality of pins for contacting the die in connection with transfer from the die supply source to the substrate. Claim 11 A die attachment system according to claim 1, wherein the die supply source comprises an LED wafer, and the plurality of dies are a plurality of LED dies. Claim 12 A die attachment system according to claim 1, wherein at least one of (i) the die and (ii) a bonding location of the substrate configured to receive the die comprises an adhesive for fixing the die to the bonding location after transfer from the die supply source to the substrate. Claim 13 delete Claim 14 A method for attaching a die to a substrate, the method comprising: providing a die supply source including a plurality of dies for attachment to the substrate, wherein the die supply source is located between a support structure supporting the substrate and a bond tool; moving the bond tool, which is carried by a bond head, downward so that a contact portion of the bond tool contacts the die, in order to transfer the die from the die supply source to the substrate, wherein the bond head includes a spring portion coupled to the bond tool, wherein the spring portion is configured to be compressed while pressing the die against the substrate using the contact portion of the bond tool, and the die supply source is located between the substrate and the bond tool, and the die is compressed against the substrate by the bond tool in relation to the bonding operation; and detecting the amount of compression of the spring portion while the die is bonded to the substrate using a sensor. Claim 15 A die attachment method according to claim 14, wherein the spring portion is compressed during contact between the contact portion and the die in connection with the transfer of the die to the substrate using the contact portion of the bond tool. Claim 16 delete Claim 17 A die attachment method according to claim 14, further comprising the step of controlling the lowering of the bond tool during the moving step based on feedback from the sensor.

Images