TWI719225B - Wafer processing method - Google Patents

Abstract

[Problem] The formation of the wafer can be divided into the corners of the device chip without defects. [Solution] is to irradiate a laser beam with a wavelength penetrating the wafer from the back side of the wafer, and form two or more layers of modification inside the wafer along the first and second dicing paths Floor. After the formation of the modified layer, a grinding action of grinding is performed from the back surface of the wafer, and the modified layer is used as a starting point to divide the wafer into device wafers along the first and second scribe lanes. In the formation of the reforming layer, the lowermost reforming layer on the front side of the wafer in the first dicing lane is turned in the direction orthogonal to the first dicing lane for each adjacent element in the first dicing lane Stagger to form. Thereby, it is formed so that the corners of adjacent element wafers do not rub against each other on the diagonal during division.

Description

Wafer processing method

Invention field

The present invention relates to a processing method for dividing a wafer into a plurality of device wafers.

Background of the invention

When a cutting blade is used to cut a wafer having a thicker thickness of, for example, 300 [μm] or more, there is a problem that chipping on the back side becomes larger. Therefore, a method using SDBG (Stealth Dicing Before Grinding) combining laser processing and grinding processing has been proposed (see, for example, Patent Document 1). In SDBG, a laser beam with a wavelength penetrating the wafer is irradiated along the predetermined dividing line of the wafer to form a modified layer with reduced intensity at a predetermined depth of the wafer. After that, the backside of the wafer is ground to thin the wafer to a finished thickness, and the wafer is divided into individual element wafers by grinding pressure with the modified layer as the starting point for division.

Prior art literature Patent literature

Patent Document 1: International Publication No. 2003/077295

Summary of the invention

However, when a modified layer is formed inside the wafer with SDBG, when it is divided into individual wafers, there will be no gaps between adjacent corners in the diagonal direction of the wafer, which results in corners of the wafer. Rubbing against each other can easily cause defects in the corners.

The present invention is an invention made in view of the aforementioned points, and its object is to provide a wafer processing method that can divide the wafer into individual element chips without causing defects at the corners.

The wafer processing method of the present invention is to divide the front surface of the wafer by a plurality of first dicing lanes elongated in a first direction, and a plurality of second scribe lanes elongated in a second direction orthogonal to the first direction. A method for processing a wafer including a wafer with a plurality of elements in each area divided by a dicing lane, characterized by including: a step of forming a modified layer, irradiating a wavelength that is transparent to the wafer from the back side of the wafer Laser beam, and form two or more modified layers inside the wafer along the first and second scribe lanes; and the dividing step, after the modified layer forming step has been implemented, borrow from the back of the wafer The grinding unit is used to grind the wafer to the thickness of the finished product, and use the modified layer as a starting point to divide the wafer along the first and second scribe lanes. In the step of forming the modified layer, at least the first dicing The lowermost modified layer on the front side of the wafer in the lane is formed by staggering each adjacent element in the first dicing lane toward the second direction, so as to prevent the corners of adjacent element wafers from being diagonally opposite to each other during division. Rubbing on the line.

According to this configuration, since the lowermost modified layer on the front side of the wafer in the modified layer forming step is staggered in the dicing lane for each adjacent element instead of being formed continuously, it can be formed on the element wafer A gap is formed between adjacent corners in the diagonal direction of the wafer. Thereby, it is possible to reduce the friction between the corners of the element wafers in the dividing step, and it is possible to reduce the defects in the corners.

According to the present invention, the wafer can be divided so that no defects are generated at the corners of the element wafer.

10: Laser processing device

11: Abutment

12: Laser processing unit

13: hold the stage

14: Work clamp table moving mechanism

16: Standing arm

17: Arm

20: Indexing feed component

21: Processing feed components

23, 30: rail

24: Y-axis table

25: Ball screw

26: drive motor

31: movable part

32: X axis table

33: Linear motor

35: Magnetic plate

38: Theta workbench

39: Fixture Department

40: Processing head

51: control components

60: Grinding device

61: work clamp

62: Grinding wheel

W: Wafer

W1: front

W2: back

WA: component layer

L1: First cutting lane

L2: Second cutting lane

C: angle

D: Components

DC: component chip

T: Protective tape

F: ring frame

S: Adhesive sheet

R, R1, R2, R3: modified layer

Y1, Y2: Y-axis direction position

s1, s2: interval

X, Y, Z: direction

a: part

Fig. 1 is a schematic perspective view of a processed product of this embodiment.

Fig. 2 is a schematic perspective view of the laser processing apparatus of the embodiment.

Fig. 3 is an explanatory diagram showing the holding procedure of the present embodiment.

Fig. 4 is an explanatory diagram showing a step of forming a modified layer of the present embodiment.

Fig. 5 is an explanatory diagram showing a step of forming a modified layer of the present embodiment.

6A to 6C are explanatory diagrams showing the steps of forming a modified layer in this embodiment.

7A to 7C are explanatory diagrams showing the steps of forming a modified layer in this embodiment.

Fig. 8 is an explanatory diagram showing the division step of the present embodiment.

Fig. 9 is an explanatory diagram showing the division step of the present embodiment.

Fig. 10 is a partial enlarged view of the wafer after the dividing step viewed from the front side.

The form used to implement the invention

Hereinafter, the processing method of the wafer of this embodiment will be described with reference to the attached drawings. First, referring to FIG. 1, the wafer processed by the wafer processing method of this embodiment will be described. Fig. 1 is a schematic perspective view of a wafer of this embodiment.

As shown in FIG. 1, the wafer W is formed in a substantially disc shape, and an element layer WA is provided on the front surface W1. On the front surface W1 of the wafer W, a first scribe lane L1 extending in one direction and a plurality of second scribe lanes L2 extending in a direction orthogonal to the first scribe lane L1 are formed. A plurality of elements D are formed in the area partitioned by these first and second scribe lanes L1 and L2. In addition, a protective tape T for protecting the device D is attached to the front surface of the wafer W. As shown in FIG. 2, the lower surface side of the wafer W is attached to the adhesive sheet S which has been stretched on the ring-shaped ring frame F, and is held on the ring frame F. As shown in FIG.

The wafer W has a thickness of, for example, 300 [μm] or more, and is divided into individual element wafers by combining SDBG formed by laser processing and grinding processing. In this case, after the modified layer is formed in the wafer W by laser processing, the wafer W is ground to the thickness of the finished product by grinding processing, and the modified layer is used as the starting point for dividing the wafer W. Furthermore, the wafer W may also be a semiconductor wafer in which semiconductor elements such as IC and LSI are formed on a semiconductor substrate such as silicon or gallium arsenide, or it may be formed on an inorganic material substrate such as sapphire or silicon carbide. Optical element wafers with optical elements such as LEDs.

Next, referring to FIG. 2, a laser processing apparatus used in the wafer processing method of this embodiment will be described. Figure 2 shows the laser of this embodiment A schematic perspective view of the processing device. In addition, the laser processing apparatus of this embodiment is not limited to the configuration shown in FIG. 2. The laser processing device can have any structure as long as it can form a modified layer on the wafer.

As shown in FIG. 2, the laser processing apparatus 10 is configured such that the laser processing unit 12 irradiating laser light and the holding table 13 holding the wafer W on the upper surface are relatively moved to process the wafer W.

The laser processing device 10 has a cuboid base 11. The upper surface of the base 11 is provided with a work chuck table for processing and feeding the holding table 13 in the X-axis direction (first direction) and indexing and feeding in the Y-axis direction (second direction orthogonal to the first direction). Movement mechanism 14. A standing wall 16 is erected behind the work clamp table moving mechanism 14. An arm 17 protrudes from the front of the standing wall 16, and the laser processing unit 12 is supported on the arm 17 to face the holding table 13.

The work chuck table moving mechanism 14 is provided with an indexing feed assembly 20 that relatively moves the holding table 13 and the laser processing unit 12 in the indexing feed direction (Y-axis direction), and an indexing feed assembly 20 that moves in the processing feed direction (X-axis direction). ) The processing feed assembly 21 that moves relative to each other.

The indexing feed assembly 20 includes a pair of guide rails 23 parallel to the Y-axis direction arranged on the upper surface of the base 11 and a motor-driven Y-axis table 24 slidably arranged on the pair of guide rails 23. On the lower surface side of the Y-axis table 24, a nut part not shown is formed, and a ball screw 25 is screwed into these nut parts. In addition, by rotating and driving the drive motor 26 connected to one end of the ball screw 25, the Y-axis table 24, the processing feed assembly 21, and the holding table 13 can be moved along the guide rail 23 in the Y-axis direction.

The processing feed assembly 21 is provided with a pair of guide rails 30 parallel to the X-axis direction arranged on the upper surface of the Y-axis table 24, and a movable part that can move in the processing feed direction (X-axis direction) through the guide rails 30 31. The movable portion 31 has an X-axis table 32 that guides sliding movement in the X-axis direction by the guide rail 30 and a linear motor (motor) 33 provided at the lower part of the X-axis table 32. The linear motor 33 includes an electromagnetic coil (not shown) that faces a magnet plate 35 arranged along the X-axis direction between the guide rails 30. The electromagnetic coil is, for example, a three-phase alternating current is sequentially energized by shifting the phases to form a moving magnetic field that moves the linear motor 33 itself and the X-axis table 32 in a reciprocating direction that is the X-axis direction. In addition, the processing feed unit 21 is not limited to the above-mentioned units, and may be changed to a structure using, for example, a ball screw that is rotationally driven such as the indexing feed unit 20.

The holding table 13 is held on the upper surface of the X-axis table 32. The holding table 13 is formed in a disc shape, and is rotatably provided on the upper surface of the X-axis table 32 through the θ table 38. On the upper surface of the holding table 13, an adsorption surface is formed by a porous ceramic material. Around the holding table 13, four clamp parts 39 are provided through the support arm. By driving the four clamp parts 39 with an air actuator (not shown), the ring frame F around the wafer W can be clamped and fixed from four directions.

The laser processing unit 12 has a processing head 40 as a laser beam irradiating component provided at the front end of the arm portion 17. The optical system of the laser processing unit 12 is provided in the arm 17 and the processing head 40. The processing head 40 condenses the laser beam generated by the oscillator not shown by the condensing lens, and irradiates the laser beam to the wafer W held on the holding table 13 to Perform laser processing. In this case, the laser beam has a wavelength that is penetrative to the wafer W, and is adjusted to be positioned inside the wafer W in the optical system.

The laser beam is irradiated to form a modified layer R (see FIG. 4) as the starting point of division in the inside of the wafer W. The modified layer R refers to a state in which the density, refractive index, mechanical strength, and other physical properties inside the wafer W become different from the surroundings by the irradiation of the laser beam, and the intensity is also lower than that of the surroundings. area. The modified layer R may be, for example, a melt-processed area, a cracked area, a dielectric breakdown area, or a refractive index change area, or a mixed area of these areas. The laser beam irradiated by the processing head 40 is formed so that the height of the condensing position where the modified layer R is formed can be controlled.

The laser processing device 10 is provided with a control unit 51 that integrates the components of the control device. The control component 51 is composed of a processor that executes various processes. The detection results from various detectors not shown in the figure can be input to the control component 51. The control unit 51 can output control signals to the drive motor 26, the linear motor 33, the processing head 40, and the like.

Hereinafter, referring to FIGS. 3 to 9, the wafer processing method will be described. What each shows is that FIG. 3 is an explanatory diagram of the holding step of this embodiment, FIGS. 4 to 7 are explanatory diagrams of the modified layer forming step of this embodiment, and FIGS. 8 and 9 are explanatory diagrams of the dividing step. In addition, in this embodiment, although the description is an example of applying the wafer processing method to SDRG, it can also be applied to other methods of dividing the inside of the wafer with the modified layer as a starting point.

As shown in Figure 3, the holding step is first implemented. In the holding step, the wafer W to which the protective tape T is attached is sucked and held on the holding table 13 via the protective tape T.

As shown in FIG. 4, after the holding step is performed, the reforming layer forming step is performed. In the reforming layer forming step, first, the holding table 13 is moved and rotated to position the wafer W so that, for example, the first scribe lane L1 is parallel to the X-axis direction (first direction), and the second scribe lane is extended. L2 and the Y-axis direction (second direction) become parallel and extend. Next, with respect to the wafer W on the holding table 13, the processing head 40 is positioned on the first scribe lane L1 parallel to the X-axis direction. After that, while irradiating the laser beam to the back side W2 of the wafer W, the holding table 13 and the processing head 40 are relatively moved in parallel to the X-axis direction (processing feed). Thereby, the laser beam can be irradiated along the first scribe lane L1, and the modified layer R along the first scribe lane L1 can be formed inside the wafer W.

After forming the modified layer R along the target first scribe lane L1, the irradiation of the laser beam is stopped, and the holding table 13 and the processing head 40 are relatively moved in the Y-axis direction corresponding to the interval of the first scribe lane L1 ( Indexing feed). Thereby, the processing head 40 can be aligned with the first scribe lane L1 adjacent to the first scribe lane L1 of the object.

Next, the same modified layer R is formed along the adjacent first scribe lane L1. This action is repeated to form the modified layer R along all the first cutting lanes L1 extending in the X-axis direction. After that, the holding table 13 is rotated 90° around the rotation axis and along the Y-axis The second scribe lane L2 (refer to FIG. 5) extending in the direction forms the modified layer R.

The modified layer R is based on each pulse according to the wavelength of the laser beam The pulse pitch is modified, and the modified layers that are elongated in the cross-sectional view are continuous and juxtaposed in the processing feed direction (X-axis direction). The formation of the reforming layer R by the laser beam is repeated twice or more as described later to form two or more reforming layers R inside the wafer W.

FIG. 6 is an explanatory diagram about the main points of forming the first modified layer in the step of forming the modified layer, and FIG. 6A is an enlarged view of a part of FIG. 5. In the reforming layer forming step, when two or more reforming layers R are formed, as shown in FIG. 6A, the first reforming layer R1 in the first scribe lane L1 is parallel to the X-axis direction. It is not located on a straight line but formed in a discontinuous manner. To form the modified layer R1 in the first scribe lane L1, first, in the positioning of the first scribe lane L1 by the processing head 40 (refer to FIG. 4), the condensing point is set to, for example, the position in the Y-axis direction is positioned The position Y1 in FIG. 6B, and the position in the Z-axis direction is the position in FIG. 6B where the modified layer R1 is to be formed. In addition, during the processing and feeding of the wafer W, the irradiation of the laser beam and the irradiation stop are repeated every other element D in the X-axis direction. Thereby, in the Y-axis direction position Y1 in the first scribe lane L1, for each element D adjacent in the X-axis direction, the region formed by the modified layer R and the region not formed are alternately provided.

After the modified layer R1 is formed at the position Y1 in the Y-axis direction, the wafer W is indexed and fed so that the condensing point moves in the Y-axis direction in the first scribe lane L1 by an interval s1, and the condensing point is set Position Y2 in the Y-axis direction. After that, while processing and feeding the wafer W in the X-axis direction, the area in the first scribe lane L1 where the modified layer R is not formed on the Y-axis direction position Y1 is irradiated at the Y-axis direction position Y2. Laser beam. Therefore, here the laser beam During the irradiation, the laser beam irradiation and irradiation stop may be repeated every other element D in the X-axis direction. In other words, in the Y-axis direction position Y2, for each adjacent element D in the X-axis direction, the region formed by the modified layer R1 and the region not formed may be alternately provided. Thereby, the modified layer R1 formed at the Y-axis direction position Y1 and the modified layer R1 formed at the Y-axis direction position Y2 can be combined, and the first cut is made for each adjacent element D in the X-axis direction. The lane L1 is shifted in the Y-axis direction by the interval s1 to form a modified layer R1.

In addition, in the formation of the reforming layer R1 of the first scribe lane L1, at a position sandwiching the reforming layer R1 formed on the second scribe lane L2, the reforming layer R1 is made to be in the region of the space s2 Non-formed. In other words, it is not formed continuously in the extending direction of the first scribe lane L1, but is formed intermittently. Here, in the case of the interval s1, as long as it can fall within the range of the first dicing lane L1, it is preferable to be wider. Preferably, the Y-axis positions Y1 and Y2, which are the formation positions of the modified layer R1, are set at the same distance from the center of the first scribe lane L1 in the width direction, which can be exemplified as follows: the interval s1 is set to 10-40[ μm], and the distance from the center in the width direction of the first scribe lane L1 to the Y-axis direction positions Y1 and Y2 is set to 5-20 [μm]. Moreover, in the case of the interval s2, it is preferable to set the center in the width direction of the second scribe lane L2 as the center, and it can be exemplified as 20 [μm].

As described above, the modified layer R1 of the first layer is formed along all the first scribe lanes L1 extending in the X-axis direction, and then along the second scribe lane L2 extending in the Y-axis direction as described above The first modified layer R1 is formed. The modified layer R1 of the second cutting lane L2 is The cutting lane L2 is formed in a straight line continuous at the center position in the width direction.

Fig. 6B is a cross-sectional view taken along line b-b of Fig. 6A, and Fig. 6C is a cross-sectional view taken along line c-c of Fig. 6A. As shown in FIGS. 6B and 6C, the first modified layer R1 is formed on the front side W1 of the wafer W as the lowermost layer.

FIG. 7 is an explanatory diagram of the main points of the formation of the second and subsequent modified layers in the modified layer forming step. Fig. 7A is an enlarged view of part a of Fig. 5, Fig. 7B is a cross-sectional view taken along line d-d of Fig. 7A, and Fig. 7C is a cross-sectional view taken along line e-e of Fig. 7A. As shown in FIGS. 7B and 7C, the formation position of the second modified layer R2 is set at a predetermined distance from the back W2 side (upper side) of the first modified layer R1, and the third layer The formation position of the modified layer R3 is set at a position separated from the back W2 side of the second modified layer R2 by a predetermined distance. Therefore, although three modified layers R1 to R3 are formed in this embodiment, when four or more modified layers are formed, they are formed so that the modified layer formed just before faces the back surface W2. The side is separated by a predetermined distance.

As shown in FIG. 7A, the second and third modified layers R2 and R3 in the first scribe lane L1 are located at the center of the width direction of the first scribe lane L1 to extend from the first scribe lane L1 It is formed in a straight line that is continuous in the direction. In addition, the second and third modified layers R2 and R3 in the second scribe lane L2 are also at the center position in the width direction of the second scribe lane L2 so as to be in the extending direction of the second scribe lane L2. It is formed in a continuous linear manner. In this way, three modified layers R1 to R3 are formed from the front W1 side of the wafer W to the back W2 side, and these modified layers R1 to R3 are formed inside the wafer W along each cut The starting point of the division of lanes L1 and L2.

As shown in FIG. 8 and FIG. 9, the dividing step may be performed after the reforming layer forming step is performed. In the dividing step, the wafer W is held on the work chuck table 61 of the grinding device 60 with the protective tape T interposed therebetween. By rotating the grinding wheel (grinding assembly) 62 while bringing it close to the work chuck 61, the grinding wheel 62 is brought into contact with the back surface W2 of the wafer W in rotation, thereby grinding the wafer W to a thickness of the finished product. . With this grinding action, the grinding pressure is applied from the grinding wheel 62 to the modified layers R1 to R3, so that the cracks are extended in the thickness direction of the wafer W starting from the modified layers R1 to R3. Thereby, the wafer W is divided along the first scribe lane L1 and the second scribe lane L2 to form individual element wafers DC (not shown in FIG. 8).

Fig. 10 is a partial enlarged view of the wafer after the dividing step viewed from the front side. As shown in FIG. 10, the wafer W is placed on the front W1 side, and the corners (corners) C of the element wafers DC adjacent in the Y-axis direction are arranged at approximately the same position. The angles C of the element wafers DC adjacent to each other in the direction are located at positions separated by an interval s1 in the Y-axis direction. The corners C of the element wafers DC adjacent to each other in the diagonal direction of the element wafer DC are not at the same position but at a separate position. Since the corners C are positioned at positions separated from each other in this way, it can be formed in the dividing step so that the corners of adjacent element wafers DC do not rub against each other on the diagonal. Here, in the case of using, for example, a wafer W formed in particular in a direction inclined by 45° with respect to the cleavage direction of the wafer W, the dicing lanes L1 and L2 will change when it is divided by grinding pressure or the like. It is easy to produce defects in the diagonal direction of the element wafer DC. In this embodiment, since the corners C of the element wafers DC adjacent in the diagonal direction are separated from each other without rubbing Therefore, even if the crystal direction is inclined as described above, it is still possible to prevent the occurrence of defects or cracks in the corner C. Thereby, the wafer W can be well divided into individual element wafers DC along the dicing lanes L1 and L2.

In addition, the first modified layer R1 of the first scribe lane L1 is provided with a non-formed region of the modified layer R1 at the aforementioned interval s2, so that the corners of adjacent element wafers DC can be prevented more effectively. The situation of friction on the diagonal.

Furthermore, in this embodiment, since the modified layer R formed on the second scribe lane L2 is formed at the center position in the width direction of the second scribe lane L2, the upper and lower ends of the element D in FIG. 10 are adjacent to each other. The distance between the upper end and the lower end of these element wafers DC is formed to be approximately the same. Therefore, the pads used for electrical connection with the element D can be provided such that the assembly formed along the upper and lower ends of the element wafer DC can be performed in the same way as the assembly at the upper end and the assembly at the lower end. To maintain workability.

In addition, the present invention is not limited to the embodiment described above, and can be implemented with various modifications. In the above-mentioned embodiment, the size, shape, etc. illustrated in the drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, as long as it does not deviate from the scope of the object of the present invention, it can be implemented with appropriate changes.

For example, in the above-mentioned embodiment, although the first modified layer R1 of the first scribe lane L1 is formed to be non-continuous for each adjacent element D, the second scribe lane L2 may be similarly non-continuous. Continuously formed. Even in this case, it is still possible to set the corners C adjacent in the diagonal direction of the element D to be separated from each other. Furthermore, in component D, only in In the case where bonding pads are formed along one of the first scribe lane L1 and the second scribe lane L2, the dicing lanes L1 and L2 where the bonding pads are not formed are formed to be discontinuous as described above. The modified layer R is divided. Thereby, it becomes possible to perform bonding without changing the processing conditions such as the bonding position of the distance from the bonding pad while keeping the distance between the bonding pad and the outer edge of the element wafer constant.

Industrial availability

As explained above, the present invention has the effect that it is possible to divide wafers well without causing cracks or defects on the divided device wafers, especially when dividing semiconductor wafers or optical device wafers into The wafer processing method of individual wafers is particularly useful.

Y1, Y2‧‧‧Y axis position

L1‧‧‧The first cutting pass

L2‧‧‧Second cutting pass

D‧‧‧Component

R, R1‧‧‧Modified layer

s1, s2‧‧‧interval

X, Y‧‧‧direction

W‧‧‧wafer

W1‧‧‧Front

W2‧‧‧Back

Claims (1)

A method of processing a wafer by dividing the front surface of the wafer by a plurality of first dicing lanes elongated in a first direction, and a plurality of second dicing lanes elongated in a second direction orthogonal to the first direction A method for processing a wafer including a wafer with a plurality of elements in each area divided by the road is characterized by comprising: a step of forming a modified layer, irradiating a wavelength that is transparent to the wafer from the back side of the wafer Laser beam, and form two or more modified layers inside the wafer along the first scribe lane and the second scribe lane; and the dividing step, after performing the modified layer forming step, from the back of the wafer Grinding components to be thinned to the thickness of the finished product, and using the modified layer as a starting point to divide the wafer along the first scribe lane and the second scribe lane, in the step of forming the modified layer, At least the lowermost modified layer on the front side of the wafer in the first dicing lane is formed by staggering each adjacent element in the second direction in the first dicing lane to avoid damage to adjacent element wafers. The corners rub against each other on the diagonal when they are divided.

Images