Die bonding apparatus and method for positioning die using die bonding apparatus

Abstract

To provide a die bonding method for accurately positioning a die before bonding.SOLUTION: A die bonding apparatus 10 includes a linear motor and a carriage 12 arranged to be driven by the motor along a traveling direction. The carriage 12 includes a bond head 14 that picks up a die 50, and a first camera 16 that detects a target position for positioning the die 50. The first camera 16 and the bond head 14 are attached to the carriage 12 along the traveling direction of the carriage 12 at a first distance D1 between the optical axis of the camera 16 and the central axis of the bond head 14.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the semiconductor industry, and more particularly to a die bonding method for accurately positioning a die prior to bonding, and a die bonding apparatus for carrying out the die bonding method. The die bonding apparatus and method are particularly suitable for hybrid bonding applications requiring high-precision die placement with a placement error of ±50 nm or less. [Background technology]

[0002] Die bonding is widely used to attach or bond semiconductor chips, also known as dies, onto substrates or packages. Die bonding can be performed using a variety of techniques, including wire bonding, flip-chip bonding, and adhesive bonding. Die bonding plays a key role in creating the electrical connections necessary for the functionality of semiconductor devices. Precise positioning of the die is a fundamental aspect of semiconductor manufacturing to achieve optimal electrical performance, functionality, reliability, and uniformity in the final semiconductor device.

[0003] As shown in FIGS. 1-1c, a conventional die bonding system includes a bond head BH and a carriage C equipped with a downward-facing camera DLC that can measure the position of pads on a PCB to improve die placement accuracy. The downward-facing camera DLC and bond head BH are mounted on the carriage C at a fixed distance D, as shown in FIG. 1. The carriage C is slidably engaged with a rail so as to move along an encoder scale ES. The movement of the carriage C is measured by a single encoder head EH attached to the carriage C and positioned to move along and above the encoder scale ES. While the carriage C moves to track the central axis of the bond head BH and the optical axis of the camera DLC, the distance D between the downward-facing camera DLC and the bond head BH is measured using an encoder and an upward-facing camera ULC. The downward-facing camera DLC is used to measure the exact position of the pad on the PCB to which the die must be attached. The camera DLC measures the alignment error ΔX between the target position TP and the optical axis of the downward camera DLC, as shown in Figure 1a. Then, the carriage C is moved by a distance D+ΔX so that the bond head BH is positioned above the target position to position the die as shown in Figures 1b and 1c.

[0004] The placement accuracy of these systems is not optimal due to the potential for different placement errors. In particular, heat generated by the motor causes thermal expansion of the encoder scale beyond D+ΔX, as well as thermal expansion of the carriage C, which directly impacts the spacing D between the bondhead and camera. Scale etch defects beyond D+ΔX also adversely affect the placement accuracy of these systems.

[0005] However, hybrid bonding applications use small copper-to-copper connections and involve dies stacked on top of each other within a package, thus requiring the utmost die placement accuracy with placement tolerances of ±50 nm or less.

[0006] Positioning systems equipped with two encoder heads to compensate for measurement errors due to thermal expansion of the encoder scale are also known. Patent Document 1, for example, relates to a measuring machine equipped with a system for compensating for measurement errors due to thermal expansion of the scale of a linear transducer. To compensate for the thermal expansion of the scale, the encoder heads are used to calculate a magnification factor based on the distance between the two encoder heads and their respective measurements.

[0007] Patent Document 2 discloses a thermally compensated positioning system including a scale support that supports a scale, a carriage arranged to move along the scale, and two encoder heads spaced apart from each other by a predetermined interval along the traveling direction of the carriage. These two encoder heads are configured to detect reference marks, respectively, and supply two signals related to the reference marks to an evaluation unit, and to compensate for thermal expansion of the encoder scale by using the relative interval between the two encoder heads, which changes with temperature.

[0008] Other thermally compensated positioning systems with two encoder heads are disclosed, for example, in U.S. Pat. Nos. 5,629,997, 5,729,963, 5,733,147, 5,896,152, and 5,929,163. These positioning systems typically rely on multiple sensing units on the same scale to compensate for temperature or to calibrate the scale. Scale mapping is typically used for thermal expansion compensation, which is tedious and time-consuming. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent Application Publication No. 2636991 [Patent Document 2] DE 19919042 [Patent Document 3] German Patent Application Publication No. 102021118091 [Patent Document 4] German Patent Application Publication No. 102021118092 [Patent Document 5] European Patent Application Publication No. 2527797 [Patent Document 6] European Patent Application Publication No. 3982088 Summary of the Invention [Problem to be solved by the invention]

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a die bonding apparatus and a method for accurately positioning a die before bonding that avoids the above limitations.

[0011] More particularly, it is an object of the present invention to provide a die bonding apparatus for highly accurate die positioning to within a placement error of ±50 nm or less.

[0012] Another object of the present invention is to provide a method of positioning the die whereby the placement of the die is not affected by thermal expansion, particularly of the encoder scale.

[0013] It is a further object of the present invention to provide a method for positioning the die in which die placement is not affected by scale etching defects. [Means for solving the problem]

[0014] These objects are achieved, inter alia, by a die bonding apparatus comprising: a linear motor; a carriage arranged to be driven by the linear motor along a direction of travel; a linear encoder having an encoder scale extending along the direction of travel of the carriage; at least one first and second encoder head attached to the carriage; and a control device arranged to move the carriage as a function of values ​​read by the respective first and second encoder heads so as to align the bond head with a target position. The carriage comprises a bond head configured to pick up a die and a camera configured to detect the target position for positioning the die and for measuring an alignment error between the optical axis of the camera and the target position. The central axis of the bond head and the optical axis of the camera are spaced apart from each other along the direction of travel by a first distance. The first and second encoder heads are spaced apart from each other along the direction of travel by a second distance corresponding to the first distance and an offset corresponding to an alignment error between the first encoder head and the second encoder head and an offset corresponding to an alignment error between the central axis of the bond head and the optical axis of the camera, respectively.

[0015] In one embodiment, the first and second encoder heads are aligned with a central axis of the bond head and an optical axis of the camera, respectively, with an alignment error.

[0016] In one embodiment, when the bond head is brought to position the die over the target location, the central axis of the bond head intersects the center of the die.

[0017] In one embodiment, the die bonding apparatus further includes a transverse beam and two additional axes of motion slidably engaged with and extending perpendicular to the transverse beam. The carriage is slidably mounted along the transverse beam. The linear encoder is a 1D plus encoder including a linear scale having an incremental track and an additional track, and first and second sets of encoder heads positioned corresponding to the bond head and camera of the carriage, respectively. Each set of encoder heads includes a Y encoder head positioned to scan the incremental track and at least one X encoder head positioned to scan the additional track for position correction of the transverse beam using the additional axes of motion.

[0018] In one embodiment, each set of encoder heads includes two X encoder heads for bondhead and camera angle correction.

[0019] In one embodiment, the X encoder heads of the first and second sets of encoder heads are located on either side of the respective bondhead and camera.

[0020] In one embodiment, the Y encoder heads of the first and second encoder head sets are aligned with a central axis of the bondhead and an optical axis of the camera, respectively, with an alignment error.

[0021] Another aspect of the present invention is a method of positioning a die using a die bonding apparatus according to any of the above-described embodiments, comprising the steps of: The method comprises the following steps: a) finding a target position for positioning the die using a camera on the carriage; b) measuring or recording the alignment error between the camera optical axis and the target position; c) recording the difference between the first interval and the second interval; d) recording the position of the carriage with a first encoder head; e) an aligning step, comprising: (i) the outputs of the first and second encoder heads; (ii) the recorded difference, and if necessary, the alignment error; aligning the bond head with the target location by moving the carriage as a function of f) actuating the bond head in the Z direction to place the die at the target position; Includes.

[0022] In one embodiment, a method for positioning a die comprises the following steps: performing micro-alignment according to camera feedback to reduce alignment errors as much as possible, preferably below 10 nm; moving the vehicle to position the second encoder head at the position recorded by the first encoder head, with an offset corresponding to the recorded difference; Equipped with.

[0023] In one embodiment, a method for positioning a die comprises the following steps: recording an alignment error between the camera optical axis and the target position; moving the carriage with a second encoder head to the position recorded by the first encoder head with an offset equal to the recorded difference between the first and second intervals plus the alignment error; Equipped with.

[0024] In one embodiment, the die bonding apparatus further comprises an upward-facing camera positioned below the target location and oriented facing the carriage. The method for positioning the die further comprises a calibration step performed before starting to place the die at the target location. The calibration step comprises the following steps: driving the carriage to move the camera and bond head above the upward-facing camera to enable the upward-facing camera to measure the first distance; further driving the carriage in the same direction to move the first and second encoder heads across a reference mark on the encoder scale to measure a second distance to determine an encoder head alignment error as a function of the measured first distance; It consists of:

[0025] In one embodiment, an offset between the central axis of the bond head and the center of the die carried by the bond head is measured using an upward-facing camera, and the offset is used to correct the carriage position to accurately position the die at the target location, regardless of the offset amplitude.

[0026] Another aspect of the present invention is a method for positioning a die using a die bonding apparatus, the method comprising the steps of: Finding a target position with a camera for positioning the die; recording a positional deviation between the camera optical axis and the target position; moving the carriage as a function of signal outputs obtained by each of the first and second sets of encoder heads to align the bond head with a target position along the XY directions and about the Z axis; driving the die bond head in a Z direction to place the die at a target position; Includes.

[0027] The invention will be better understood from the description of some embodiments given by way of example and illustrated in the drawings. [Brief explanation of the drawings]

[0028] [Figure 1] 1 shows a schematic diagram of a die bonding apparatus according to the prior art; [Figure 1a] A series of operations for placing a die at a target position using the die bonding apparatus of FIG. 1 is shown. [Figure 1b] A series of operations for placing a die at a target position using the die bonding apparatus of FIG. 1 is shown. [Figure 1c] A series of operations for placing a die at a target position using the die bonding apparatus of FIG. 1 is shown. [Figure 2] 1 shows a schematic diagram of a die bonding apparatus according to an embodiment; [Figure 2a] 3 illustrates a sequence of operations in a method according to one embodiment for placing a die at a target location using the die bonding apparatus of FIG. 2. [Figure 2b] 3 illustrates a sequence of operations in a method according to one embodiment for placing a die at a target location using the die bonding apparatus of FIG. 2. [Figure 2c] 3 illustrates a sequence of operations in a method according to one embodiment for placing a die at a target location using the die bonding apparatus of FIG. 2. [Figure 3] 1 shows a schematic diagram of a bonding apparatus according to another embodiment; [Figure 4] 1 shows a schematic diagram of a die bonding apparatus according to a further embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0029] 2, a die bonding apparatus 10 includes a linear motor (not shown) and a carriage 12 arranged to be driven by the motor along a direction of travel. The carriage 12 includes a bond head 14 configured to pick up a die 50 (FIG. 2a) and a first camera 16 configured to detect a target position 30 for positioning the die 50. The camera 16 and bond head 14 are mounted on the carriage 12 along the direction of travel of the carriage 12 with a first distance D1 between the optical axis of the camera 16 and the central axis of the bond head 14.

[0030] The die bonding apparatus 10 further includes a linear encoder having a scale 20 extending along the traveling direction of the carriage 12, first and second encoder heads 22a, 22b attached to the carriage 12, and a control device configured to move the carriage 12 as a function of values ​​read by the first and second encoder heads 22a, 22b, respectively, to align the die 50 to the target position 30. The first and second encoder heads 22a, 22b are spaced apart from each other along the traveling direction of the carriage 12 by a second distance D2, as shown in FIG.

[0031] In a preferred embodiment, the two encoder heads 22a, 22b are positioned to align as closely as possible with the camera optical axis and the bond head central axis, respectively. However, there is always an encoder head alignment error δ with the camera 16 and bond head 14, respectively, that must be taken into account for maximally accurate die positioning. Thus, the second spacing D2 between the two encoder heads 22a, 22b corresponds to the first spacing D1 plus an offset corresponding to the encoder head alignment error δ, as depicted in FIG. 2.

[0032] As mentioned above, linear encoders are sensitive to thermal expansion, particularly due to heat generated by the motor. Generally, the encoder scale 20 extends in the longitudinal direction thereof during operation of the bonding apparatus 10, which can cause measurement errors on the scale. The first distance D1 between the optical axis of the camera 16 and the central axis of the bond head 14 can also change due to thermal expansion of the carriage 12. The scale 20 can also have etching defects. All of these parameters must be considered for the most accurate placement of the die 50 at the target location 30.

[0033] Advantageously, the placement of the die by the die positioning method described below is not affected by these parameters.

[0034] A calibration step is required before starting die placement to measure the first distance D1 and the second distance D2 and to determine the alignment error δ of the encoder head.

[0035] In this regard, the die bonding apparatus 10 further includes a second camera 18 positioned below the target position 30 and oriented to face the carriage 12, as shown in FIG. 2a. The carriage is driven to move the first camera 16 and bond head 14 above the second camera 18, allowing the second camera to measure the first distance D1. The carriage 12 is then further driven in the same direction to move the first and second encoder heads 22a, 22b across the reference mark "0" on the encoder scale 20 to measure the second distance D2 to determine the encoder head alignment error δ as a function of the measured first distance D1.

[0036] 2a, once the calibration step is completed, the method for positioning the die involves driving the carriage 12 to align the optical axis of the first camera 16 with the target position 30. More specifically, the camera 16 measures the alignment error ΔX between the camera optical axis and the target position 30. The signal output of the camera 16 is sent to a motor controller to drive the motor to perform several micro-alignments to reduce the alignment error ΔX as much as possible, preferably to less than 10 nm.

[0037] The first encoder head 22a then reads position P1 on the encoder scale 20. As a function of the signal outputs of the first and second encoder heads 22a and 22b and in response to the encoder head alignment error δ, the motor controller drives the motor to move the carriage 12 so that the second encoder head 22b moves to position P1-δ. Thus, the central axis of the bond head 14 is aligned with the target position 30 with an accuracy of less than 10 nm. The bond head 14 is then actuated in the Z direction to bond the die 50 onto the other die with the utmost precision.

[0038] Therefore, it is readily apparent that any thermal expansion and / or etching defects of encoding scale 20 do not affect the placement accuracy of die 50, because the discrete position P1 to which second encoder head 22b is brought remains at a fixed point regardless of the thermal expansion / etching defect parameters. This also emphasizes the need to make encoder head alignment error δ as small as possible, so that the target position P1-δ of second encoder head 22b is as close as possible to position P1.

[0039] In another embodiment, a die positioning method aligns the bond head 14 with the target position 30 without performing the above-described step of micro-aligning the camera axis. Instead, the alignment error ΔX between the camera axis and the target position 30 is first recorded, and the motor controller drives the carriage 12 so that the second encoder 22b moves to position P1-δ+ΔX as a function of the signal outputs of the first and second encoder heads 22a and 22b, respectively, and in response to the encoder head alignment error δ. This embodiment of the die positioning method has the advantage of being faster at the expense of accuracy. In fact, the accuracy achieved is a local accuracy exceeding ΔX, which means that any thermal expansion and / or scale etching error occurring beyond ΔX directly affects the die placement accuracy.

[0040] 3, camera 16 and bond head 14 are mounted on carriage 12 with a distance D1 between the camera optical axis and the bond head central axis along the direction of travel of carriage 12. First encoder head 22a and second encoder head 22b are mounted on carriage 12 so as to be offset relative to the camera optical axis and the bond head central axis along the direction of travel. However, the distance D2 between encoder heads 22a, 22b remains the same as the first distance D1 with an offset corresponding to the alignment error δ.

[0041] However, given that the portion of the carriage 12 within the interval D1 may have slightly different behavior compared to the portion of the carriage 12 within the interval D2 due to thermal expansion when exposed to the heat of the motor, in this embodiment, positioning the die 50 at the target position 30 may be less accurate.

[0042] In a preferred embodiment, an offset between the central axis of the bond head 14 and the center of the die 50 carried by the bond head 14 is measured using an upward-facing camera 18 to position the die at the target position 30. The measured offset is then fed to a motor controller to correct the position of the carriage 12. This ensures accurate positioning of the die 50 when the center of the die is misaligned with the bond head central axis.

[0043] According to another embodiment, which is depicted diagrammatically in FIG. The die bonding apparatus 10 includes: a Y beam 130 slidably engaged with two axes of motion 140 in the X direction; and a carriage 12 mounted for movement along the Y beam and comprising a bond head 14, a camera 16 and two sets of encoder heads arranged to read a 1D plus scale 120 featuring an incremental track 120a along the Y direction and an additional track 120b providing information necessary for compensation and angular correction in the vertical direction; Equipped with.

[0044] The first set of encoder heads comprises a Y encoder head 122a disposed on the incremental track 120a of the 1D plus scale 120 and two X encoder heads 122b, 122c disposed on the additional track 120b on either side of the bond head 14. The second set of encoder heads comprises a Y encoder head 124a disposed on the incremental track 120a of the 1D plus scale 120 and two X encoder heads 124b, 124c disposed on the additional track 120b on either side of the camera 16.

[0045] Alignment of the bond head 14 along the Y direction is performed by moving the carriage 12 using the first and second sets of Y encoder heads 122a, 124a, respectively, according to the die positioning method described in connection with the embodiment of Figures 2-2c. The two X encoder heads 112b, 112c, 124b, 124c are positioned to compensate for alignment errors in the X direction and angular errors in the Rz direction using the axis of motion 140.

[0046] While the present invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered schematic or exemplary and not restrictive. Those skilled in the art will understand that changes and modifications may be made within the scope of the claims. For example, a method for positioning a die using a die bonding machine may be adapted to a six-degree-of-freedom positioning system with multiple encoders. [Explanation of symbols]

[0047] 10 Die bonding equipment 12 carts 14 Bondhead 16 Camera 1 18 Second Camera 20 Encoder Scale 22a, 22b: first encoder head, second encoder head 120 1D Plus Encoder Scale 120a Incremental Track 120b additional track First Encoder Assembly 122a Y encoder head 122b, 122c Two X encoder heads Second Encoder Assembly 124a Y encoder head 124b, 124c Two X encoder heads 130 Y beam 140 motion axis 30 Target position ΔX Camera alignment error with target position δ is the alignment error of the encoder head with each camera and bondhead D1 Distance between camera and bondhead D2 Distance between two encoder heads 50 Die

Claims

1. A die bonding apparatus (10) comprising a linear motor and a carriage (12) arranged to be driven by the linear motor along a traveling direction, The carriage (12) includes a bond head (14) configured to pick up a die (50); a camera (16) configured to detect a target position (30) for positioning the die (50) and for measuring an alignment error (ΔX) between the optical axis of the camera (16) and the target position (30); a central axis of the bond head (14) and an optical axis of the camera (16) are spaced apart from each other by a first distance (D1) along the traveling direction; The die bonding apparatus (10) a linear encoder having an encoder scale (20) extending along the traveling direction of the carriage (12); At least one first and second encoder heads (22a, 22b; 122a, 122b, 122c, 124a, 124b, 124c) attached to the carriage (12); a control device arranged to move the carriage (12) as a function of values ​​read by the respective first and second encoder heads (22a, 22b) so as to align the bond head (50) with the target position (30); Furthermore, the first and second encoder heads are spaced apart from each other along the direction of travel by a second distance (D2) corresponding to the first distance (D1) and an alignment error (δ) between the first and second encoder heads and the central axis of the bond head (14) and the optical axis of the camera (16), respectively; A die bonding apparatus (10) characterized by:

2. 2. The die bonding apparatus (10) of claim 1, wherein the first and second encoder heads (22a, 22b) are aligned with a central axis of the bond head (14) and an optical axis of the camera (16), respectively, with an alignment error (δ).

3. 3. The die bonding apparatus (10) of claim 1, wherein a central axis of the bond head (14) intersects the center of the die (50) when the die is carried by the bond head for positioning on the target position (30).

4. A die bonding apparatus (10) further comprising a lateral beam (130) and two axes of motion (140) slidably engaged with the lateral beam (130) and extending perpendicular to the lateral beam (130), The carriage (12) is slidably mounted along the cross beam (130); the linear encoder is a 1D plus encoder, the 1D plus encoder comprising a linear scale (120) having an increment track (120a) and an incremental track (120b), and a first and second set of encoder heads arranged corresponding to the bond head (14) and the camera (16) of the carriage, respectively; Each set of encoder heads comprises a Y encoder head (122a, 124a) arranged to scan the incremental track (120a) and at least one X encoder head (122b, 122c; 124b, 124c) arranged to scan the additional track (120b) for position correction of the lateral beam (130) using the motion axis (140). A die bonding apparatus (10) according to any one of claims 1 to 3.

5. 5. The die bonding apparatus (10) of claim 4, wherein each set of encoder heads comprises two X encoder heads (122b, 122c; 124b, 124c) for angle correction (RZ) of the bond head (14) and the camera (16).

6. 6. The die bonding apparatus (10) of claim 5, wherein the X encoder heads (122b, 122c; 124b, 124c) of the first and second sets of encoder heads are located on either side of a respective bond head (14) and camera (16).

7. The die bonding apparatus (10) of any one of claims 4 to 6, characterized in that the Y encoder heads (122a, 124a) of the first and second encoder head sets are aligned with a central axis of the bond head (14) and an optical axis of the camera (16), respectively, with an alignment error (δ).

8. A method for positioning a die using a die bonding apparatus (10) according to any one of claims 1 to 7, comprising: The method comprises the following steps: a) finding a target position (30) for positioning a die (50) with a camera (16) on a carriage (12); b) measuring or recording the alignment error (ΔX) between the camera optical axis and said target position (30); c) recording the difference (δ) between the first interval (D1) and the second interval (D2); d) recording the position (P1) of the carriage (12) with a first encoder head (22a; 122a); e) an alignment step, comprising: (i) the outputs of the first and second encoder heads (22a, 22b; 122a, 124a); (ii) the recorded difference (δ); and (iii) If necessary, the alignment error (ΔX) and aligning the bond head (14) with the target location (30) by moving the carriage (12) as a function of f) actuating the bond head (14) in the Z direction to place the die at the target position (30); 10. A method for positioning a die, comprising:

9. - performing micro-alignment according to the feedback of said camera (16) in order to reduce the alignment error (ΔX) as much as possible, preferably to less than 10 nm; moving the carriage (12) to position the second encoder head (22b; 124a) at the position recorded by the first encoder head (22a, 122a), with an offset corresponding to the recorded difference (P1-δ); 9. The method of claim 8, comprising:

10. recording the alignment error (ΔX) between the camera optical axis and the target position (30); moving the carriage (12) to the position recorded by the first encoder head (22a, 122a) with an offset equal to the recorded difference (δ) and the alignment error (ΔX); 9. The method of claim 8, comprising:

11. The die bonding apparatus (10) further comprises an upward-facing camera (18) positioned below the target position (30) and oriented facing the carriage (12); A calibration step is performed before starting the die placement, and the calibration step includes the following steps: driving the carriage (12) to move the camera (16) and bond head (14) above the upward-facing camera (18) to enable the upward-facing camera (18) to measure a first distance (D1); further driving the carriage (12) in the same direction so that the first and second encoder heads (22a, 22b) move across a reference mark ("0") on the encoder scale (20) to measure a second distance (D2) to determine an encoder head alignment error (δ) as a function of the measured first distance (D1); The method for positioning a die according to any one of claims 8 to 10, characterized in that it comprises:

12. an offset between a central axis of the bond head (14) and a center of a die (50) carried by the bond head (14) is measured using the upward-facing camera (18); The offset value is used to correct the position of the carriage (12) to accurately position the die (50) at the target position (30), regardless of the amplitude of the offset value.

12. The method for positioning a die according to claim 11.

13. Finding a target position with a camera (16) for positioning the die; recording a misalignment between a camera optical axis and the target position; moving the carriage (12) as a function of signal outputs obtained by each of the first and second sets of encoder heads to align the bond head (14) with the target position (30) along the X-Y directions and about the Z-axis (Rz); Driving the die bond head (14) in the Z direction to place the die at the target position; A method for positioning a die using a die bonding apparatus (10) according to any one of claims 4 to 7, characterized in that it comprises:

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