Method for compensating for positional errors of wafer dicing blades

Abstract

A method for compensating for positional errors of a wafer dicing blade is provided, comprising: placing a wafer frame with dicing tape adhered to it and a wafer to be diced attached to the tape onto a suction cup; cutting a slit in a blank area of ​​the dicing tape surrounding the wafer using a dicing blade; moving a dicing blade alignment distance using a movable part mounted on the dicing blade, thereby moving a camera above the slit; determining the deviation distance between the center line of the slit and the alignment line in the camera lens; and re-determining the value of the blade alignment distance based on the deviation distance. According to the present invention, the cost of chip manufacturing can be significantly reduced, and the wafer dicing efficiency can be significantly improved.

Description

Technical Field

[0001] This invention relates to chip manufacturing, and more particularly to a method for compensating for positional errors of wafer dicing blades used to dice wafers into individual dies. Background Technology

[0002] In chip manufacturing, dicing tape is adhered to the wafer frame (also known as the die ring), the wafer is then attached to the dicing tape, and finally, in the dicing step, the wafer is cut into individual dies by a wafer dicing machine. Figure 1 A simplified diagram schematically illustrates a portion of a wafer dicing machine. The wafer dicing machine 1 includes a suction cup 5 for supporting a wafer frame 3 to which the wafer is attached, a lead screw 7 with graduations above the suction cup 5, and a moving part 9 movably mounted on the lead screw 7. The moving part 9 is equipped with a camera 11 and a rotating cutting blade 13. The distance between the center line 11c of the camera 11 and the center line 13c of the rotating cutting blade 13 is called the blade alignment distance H. When dicing the wafer, the alignment line in the lens of the camera 11 is first aligned with a feature point on the wafer. Then, the dicing machine control system controls the moving part 9 to move the alignment distance H along the lead screw 7, aligning the blade center line 13c with the cutting line on the wafer, and dicing the wafer along this cutting line. Subsequently, the moving part 9 continues to move along the lead screw 7 a distance equal to the die width (also called the die pitch), and dices the wafer along another cutting line until the entire wafer is diced in a direction parallel to the cutting line.

[0003] Since the dicing blade 13 is a consumable, it needs to be replaced promptly after a period of use. After replacing the dicing blade, the position of the newly installed blade will inevitably have a certain error, causing a change in the blade alignment distance H. Therefore, the positional error of the dicing blade needs to be compensated after each blade replacement; otherwise, the center line of the dicing blade will not align with the dicing line on the wafer, resulting in incorrect dicing of the wafer and damage to the wafer or the obtained die. Existing methods for compensating for the positional error of wafer dicing blades involve attaching a bare silicon wafer (light wafer) to the wafer frame using dicing tape, then manually placing the wafer frame with the attached bare silicon wafer on the dicing machine's suction cup, then using the newly replaced dicing blade to cut a slit in the bare silicon wafer, and moving the camera toward the slit with an alignment distance H. Subsequently, the camera position is manually moved so that the alignment line in the camera lens aligns with the center line of the slit, and the distance the camera is manually moved is measured. This manually moved distance is then input into the control system as a compensation value, allowing the control system to redetermine the alignment distance H of the dicing blade based on this compensation value. Finally, after rinsing the bare silicon wafer, it is removed from the dicing machine, thus completing the compensation or adjustment of the positional error of the wafer dicing blade.

[0004] Since the dicing blade is a consumable item and the positional error of the wafer dicing blade needs to be compensated or adjusted every time it is replaced, this will result in the need to use a lot of bare silicon wafers. Moreover, the storage, retrieval and alignment of the bare silicon wafers are all done manually, which not only significantly increases the cost, but also greatly reduces the production efficiency.

[0005] Therefore, existing methods for compensating for the positional errors of wafer dicing blades need to be improved. Summary of the Invention

[0006] The purpose of this invention is to overcome at least one of the above-mentioned defects in the prior art and to propose an improved method for compensating for the positional error of wafer dicing blades.

[0007] According to the present invention, a method for compensating for positional errors of a wafer dicing blade is provided. The wafer dicing blade is detachably mounted on a moving part of a wafer dicing machine and is used to dicing a wafer placed on a chuck of the wafer dicing machine. The moving part is movably disposed on a graduated lead screw of the wafer dicing machine. A camera is also mounted on the moving part, and the center line of the camera is spaced apart from the center line of the dicing blade by a blade alignment distance. The method includes:

[0008] Place the wafer frame, which has cutting tape adhered to it and on which the wafer to be cut is attached, onto the suction cup;

[0009] The cutting blade is used to cut a notch in the blank area of ​​the cutting tape around the wafer.

[0010] The moving part is moved to align the blade, so that the camera moves above the cut.

[0011] Determine the deviation distance between the centerline of the cut and the alignment line in the lens of the camera; and

[0012] The value of the blade alignment distance is re-determined based on the deviation distance.

[0013] Preferably, re-determining the value of the blade alignment distance based on the deviation distance includes:

[0014] The deviation distance is input as a compensation value into the control system of the cutting machine; and the blade alignment distance is re-determined based on the compensation value.

[0015] Preferably, determining the deviation distance includes:

[0016] Adjust the position of the camera lens so that the alignment line in the lens is aligned with the center line of the cut, and determine the distance the camera lens moves as the deviation distance.

[0017] Preferably, aligning the alignment line in the lens with the center line of the cut includes:

[0018] This aligns the movable lines in the camera lens, which are symmetrically located on both sides of the alignment line and parallel to the alignment line, with the two edges of the cut.

[0019] Preferably, determining the deviation distance includes:

[0020] The centerline of the cut is automatically determined using machine vision, and the deviation distance between the centerline of the cut and the alignment line in the lens of the camera is calculated.

[0021] Preferably, the camera is configured to automatically focus based on the distance from the camera lens to the upper surface of the cutting tape, such that the focus of the camera is located exactly on the upper surface of the cutting tape.

[0022] Preferably, the deviation distance is determined in the region of 80-90% of the entire length of the cut, near the end of the cut.

[0023] Preferably, the method is performed after each change of the cutting blade.

[0024] According to the present invention, the compensation value for the alignment distance of the dicing blade is determined by cutting slits on an existing dicing tape adhered to the wafer frame, thus eliminating the need for an additional medium such as a bare silicon wafer, which significantly reduces the cost of chip manufacturing. Furthermore, by directly using dicing tape adhered to the wafer frame and to which the actual wafer product is attached, many unnecessary additional steps are omitted compared to using a bare silicon wafer, resulting in a significant improvement in wafer dicing efficiency. Attached Figure Description

[0025] Figure 1 A portion of a wafer dicing machine is shown schematically in a simplified diagram;

[0026] Figure 2 The diagram schematically shows a wafer frame on which the wafer is attached by cutting tape;

[0027] Figure 3 The diagram illustrates the deviation between the alignment line in the camera lens and the center line of the cut.

[0028] Figure 4 The diagram illustrates the alignment of the alignment line in the camera lens with the center line of the cut.

[0029] Figure 5 Is with Figure 2 A similar diagram shows the tension on the tape being cut, indicated by arrow A, and a magnified view of the cut on the tape. Detailed Implementation

[0030] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Those skilled in the art should understand that these exemplary embodiments are not intended to limit the present invention in any way.

[0031] Figure 2 The diagram schematically shows a wafer frame on which wafers are attached by cutting adhesive tape. (Example) Figure 2 As shown, a dicing tape 15 is attached to a generally circular wafer frame 3, and a wafer 17 is attached to the dicing tape 15 located inside the wafer frame 3, thus forming a blank area B of the dicing tape between the wafer 17 and the wafer frame 3.

[0032] According to the method for compensating for positional errors of wafer dicing blades of the present invention, after replacing the dicing blade, a wafer frame 3 with the wafer 17 to be diced attached is fed into the suction cup of the dicing machine by a robotic arm.

[0033] Using a cutting blade, a slit K is cut on the blank area B of the cutting tape around the wafer 17. The control system of the cutting machine is used to operate the moving part 9, which is equipped with a camera 11, to move the previous blade alignment distance H, so that the camera 11 moves above the slit K.

[0034] The camera lens displays an alignment line S (usually a solid line) and movable lines M1 and M2 symmetrically located on both sides of the alignment line S and parallel to it. Moving the position of the camera 11 can move the alignment line S and the movable lines M1 and M2 simultaneously. However, if the camera 11 remains stationary, the alignment line S also remains stationary. But the control system can make the movable lines M1 and M2 move symmetrically relative to the alignment line S, either towards or in the opposite direction.

[0035] When camera 11 moves above the cut K, the alignment line in the camera lens should ideally be aligned with the center line of the cut. However, in practice, the alignment line in the camera lens and the center line of the cut are not aligned but offset from each other. Therefore, this will appear on the control screen of the cutting machine. Figure 3 The situation is shown. By manually adjusting the position of the camera lens and operating the control system, the movable lines M1 and M2 can be aligned with the two edges of the cut K, thereby aligning the alignment line in the camera lens with the center line of the cut, as shown. Figure 4As shown. At this time, operate the calibration button on the cutting machine to input the distance the camera was manually moved as a compensation value into the control system, so that the control system can then redetermine the new alignment distance H of the cutting blade based on this compensation value.

[0036] Furthermore, machine vision can be used to enable the cutting machine's control system to automatically determine the cut centerline and calculate the deviation distance between the cut centerline and the alignment line in the camera lens. This deviation distance is then set as a compensation value, allowing the control system to subsequently re-determine the new alignment distance H of the cutting blade based on this compensation value. For example, the cut image can be converted to 256 gray levels, and the cut center position can be determined based on this gray level. If the gap value identified by the pixel distance offset is 0.0014 mm, the control system automatically sets 0.0014 mm as the compensation value.

[0037] Because the cutting tape is transparent, if the camera lens is automatically focused in the existing manner, the focus of the camera lens will inevitably fall on the suction cup under the cutting tape, resulting in an unclear image of the cutting tape and its cut. Therefore, whether the compensation value is determined manually by moving the camera or automatically by means of machine vision, controlling the focus range of the camera lens to ensure a clear image of the cutting tape in the camera lens is crucial. According to the present invention, the camera is configured to automatically focus based on the distance from the camera lens to the upper surface of the cutting tape, ensuring that the camera focus is precisely on the upper surface of the transparent cutting tape, thereby obtaining a clear image of the cutting tape and its cut.

[0038] Due to the tension the cutting tape experiences on the suction cup and the inherent properties of the tape material, the cuts on the cutting tape often deform, and the edges of the cuts are not straight. Figure 5 As shown. In Figure 5 In the diagram, arrow A schematically shows the direction of tension on the cutting tape. Due to the influence of tension, such as... Figure 5 As shown in the enlarged view at the top center, the cut exhibits a shape that is wider in the middle and narrower at both ends. Therefore, the cutting depth / length of the cut on the tape and the location of the cut inspected by the camera are key factors affecting the accuracy of the determined cutting blade position error compensation value. According to the present invention, the last 80-90% of the entire cut length (i.e., the area near the cut end) is defined as the camera inspection area. Within this 10% area, the cut deformation of the tape is minimal, resulting in the highest accuracy of the obtained cutting blade position error compensation value, even achieving the same accuracy as the cutting blade position error compensation value obtained by cutting a slit on a bare silicon wafer.

[0039] According to the present invention, the compensation value for the alignment distance of the dicing blade is determined by cutting slits on an existing dicing tape adhered to the wafer frame, thus eliminating the need for an additional medium such as a bare silicon wafer, which significantly reduces the cost of chip manufacturing. Furthermore, by directly using dicing tape adhered to the wafer frame and to which the actual wafer product is attached, many unnecessary additional steps are omitted compared to using a bare silicon wafer, resulting in a significant improvement in wafer dicing efficiency.

[0040] Although the invention has been described in detail with reference to preferred embodiments, it should be understood that such detailed description is for illustrative purposes only and does not constitute a limitation thereof. The scope of the invention is determined by the technical solutions defined in the claims.

Claims

1. A method for compensating for positional errors of a wafer dicing blade, the wafer dicing blade being detachably mounted on a moving part (9) of a wafer dicing machine (1) and used to dicing a wafer placed on a suction cup (5) of the wafer dicing machine (1), the moving part (9) being movably mounted on a graduated lead screw (7) of the wafer dicing machine (1), and a camera (11) also mounted on the moving part (9), the center line (11c) of the camera (11) being spaced apart from the center line (13c) of the dicing blade (13) by a blade alignment distance (H), the method comprising: Place the wafer frame (3) with the cutting tape adhered to it and the wafer (17) to be cut attached to the cutting tape onto the suction cup (5); Using the cutting blade, a notch (K) is cut on the blank area (B) of the cutting tape around the wafer (17); The moving part (9) is moved to align the blade by a distance (H), so that the camera (11) moves above the cut (K); Determine the deviation distance between the centerline of the cut (K) and the alignment line in the lens of the camera; and The value of the blade alignment distance (H) is re-determined based on the deviation distance.

2. The method for compensating for positional errors of wafer dicing blades as described in claim 1, characterized in that, The value of the blade alignment distance (H) is re-determined based on the deviation distance, including: The deviation distance is input as a compensation value into the control system of the cutting machine; and The blade alignment distance (H) is redefined based on the compensation value.

3. The method for compensating for positional errors of wafer dicing blades as described in claim 1, characterized in that, Determining the deviation distance includes: The position of the camera lens is adjusted so that the alignment line (S) in the lens is aligned with the center line of the cut, and the movement distance of the camera lens is determined as the deviation distance.

4. The method for compensating for positional errors of wafer dicing blades as described in claim 3, characterized in that, Aligning the alignment line (S) in the lens with the center line of the cut includes: This aligns the movable lines (M1, M2) in the camera lens, which are symmetrically located on both sides of the alignment line (S) and parallel to the alignment line (S), with the two edges of the cut (K).

5. The method for compensating for positional errors of wafer dicing blades as described in claim 1, characterized in that, Determining the deviation distance includes: The centerline of the cut is automatically determined using machine vision, and the deviation distance between the centerline of the cut and the alignment line in the lens of the camera is calculated.

6. The method for compensating for positional errors of wafer dicing blades as described in claim 1, characterized in that, The camera is configured to automatically focus based on the distance from the camera lens to the upper surface of the cutting tape, such that the camera's focus is located exactly on the upper surface of the cutting tape.

7. The method for compensating for positional errors of wafer dicing blades as described in claim 1, characterized in that, The deviation distance is determined in the region approximately 80-90% of the entire length of the cut, near the end of the cut.

8. The method for compensating for positional errors of wafer dicing blades as described in claim 1, characterized in that, Perform the method after each change of the cutting blade.

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