TWI701730B - Wafer processing method - Google Patents

Abstract

Provide a method when at least one of the predetermined dividing lines is formed When laser processing is performed on a discontinuous wafer, it is possible to prevent the modified layer formed near the intersection point where the end of one planned dividing line is formed into a T-shaped path on the other side and colliding with the laser beam. A wafer processing method that prevents the reflection or scattering of the laser beam on the modified layer, and prevents component damage caused by light leakage.

Combine the first planned dividing line formed orthogonally with the second dividing line The method of processing a wafer in which at least the second planned dividing line is formed as a discontinuous wafer divided into individual element wafers among the planned cutting lines includes: a step of forming a first-direction reforming layer along the first The planned dividing line forms the first direction-modifying layer inside the wafer; and the second-direction reforming layer forming step is to form the second direction reforming layer inside the wafer along the second planned dividing line. The step of forming the second direction reforming layer includes forming a T-shaped path of the second direction reforming layer inside the second planned line of division where the first planned division line on which the first direction reforming layer is formed is formed as a T-shaped path and intersects Processing steps. The T-shaped path processing step is the end of the second direction modified layer of the plural layers. The lower layer spreads over the upper layer and is formed in an inverted step shape toward the first direction reforming layer formed earlier.

Description

Wafer processing method

The present invention relates to a processing method for silicon wafers, sapphire wafers and other wafers.

ICs, LSIs, LEDs, and other multiple components are divided by a predetermined dividing line, and the silicon wafers, sapphire wafers, and other wafers formed on the surface are divided into individual component chips by processing equipment. The divided component chips are widely used Used in various electronic devices such as mobile phones and personal computers.

A cutting method using a cutting device called a dicing machine is widely used in the wafer division system. In the dicing method, a cutting blade having a thickness of about 30 μm by fixing abrasive grains such as diamonds with metal or resin is rotated at a high speed of about 30,000 rpm while cutting into the wafer. The circle is divided into individual element wafers.

On the other hand, in recent years, a method of dividing a wafer into individual element wafers using a laser beam has been developed and has been put into practical use. As a method of dividing a wafer into individual element wafers using a laser beam, the first and second processing methods described below are known.

The first processing method is to set the wavelength that is transparent to the wafer The focal point of the laser beam (for example, 1342nm) is positioned inside the wafer corresponding to the planned dividing line, and the laser beam is irradiated along the planned dividing line to form a modified layer inside the wafer, and then the dividing device is used , A method in which external force is applied to the wafer, and the modified layer is used as the starting point for dividing the wafer into individual element wafers (see, for example, Japanese Patent No. 3408805).

The second processing method is to irradiate a laser beam with a wavelength (for example, 355nm) that is absorptive to the wafer on the area corresponding to the planned dividing line, form processing grooves by ablation, and then apply external force to make the processing grooves A method of dividing the wafer into individual element wafers by dividing the starting point (see, for example, Japanese Patent Application Laid-Open No. 10-305420).

In the above-mentioned first machining method, no machining chips are generated, and compared with conventional cutting by a generally used cutter, the cutting line is minimized or waterless machining is advantageous, and it is popularly used.

In addition, in the dicing method by laser beam irradiation, there is an advantage that the predetermined dividing line (street) used for the projection wafer can be processed in a non-continuous configuration (see for example Japan Special Publication No. 2010-123723). In the processing of wafers in which the planned dividing line is discontinuous, the laser beam output is turned on/off according to the setting of the planned dividing line.

[Prior technical literature] 〔Patent Literature〕

[Patent Document 1] Japanese Patent No. 3408805

[Patent Document 2] Japanese Patent Application Laid-Open No. 10-305420

[Patent Document 3] JP 2010-123723 A

However, in the vicinity of the intersection point where the planned dividing line extending continuously in the first direction and the planned dividing line extending in the second direction form a T-shaped path and collide, there are the following problems.

(1) If the first planned division line of the first modified layer is formed inside the first planned division line that is parallel to one side of the element, the first planned division line forms a T-shaped path, and the second planned division line that intersects is formed inside the second planned division line. In the modified layer, as the condensing point of the laser beam approaches the intersection of the T-shaped path, the formed first modified layer is irradiated with a part of the laser beam that processes the second planned dividing line to generate a laser beam The reflection or scattering of light leaks in the device area, and there is a problem of damage to the device due to the leakage of light, which reduces the quality of the device.

(2) Conversely, before forming the modified layer on the first planned division line parallel to one side of the element, if the second planned division line that forms a T-shaped path on the first planned division line and abuts against it, the crystal The modified layer is formed inside the circle first, because the modified layer that blocks the progress of the cracks formed in the modified layer near the intersection of the T-shaped road does not exist at the intersection of the T-shaped road, and the intersection of the T-shaped road , The crack stretches about 1~2mm to reach the component, which has the problem of reducing the quality of the component.

The present invention was made in view of the situation as shown above, and its object is to provide a method for preventing at least one planned dividing line from being at the end of one planned dividing line when laser processing is performed on a non-continuous wafer. The modified layer formed near the intersection point where the predetermined dividing line is formed as a T-shaped path on the other side is irradiated with the laser beam, which can prevent the reflection or scattering of the laser beam on the modified layer, and prevent the element caused by light leakage The processing method of damaged wafers.

According to the present invention, a method for processing a wafer is provided, which uses a plurality of first planned dividing lines formed in a first direction and a plurality of second planned dividing lines formed in a second direction intersecting the first direction A method of processing a wafer in which at least the second planned division line is formed into a discontinuous wafer divided into individual element wafers among the first planned division line and the second planned division line to form an element , Characterized in that it includes: a step of forming a first directionally modified layer for condensing a laser beam of a wavelength that is transparent to the wafer from the back side of the wafer along the first planned dividing line The inside of the wafer is irradiated, and a plurality of layers of first-direction reforming layers along the first planned dividing line are formed inside the wafer; the second-direction reforming layer forming step is performed after the first direction reforming After the quality layer formation step, along the second planned dividing line, the laser beam with a wavelength that is transparent to the wafer is condensed from the back side of the wafer to the inside of the wafer and irradiated to form the inside of the wafer. The second direction-modified layer of the plurality of layers along the second planned dividing line; and the dividing step, which is performed after the first direction-modified layer forming step and the second direction-modified layer forming step, the crystal The circle imparts an external force, the first direction modified layer and the second direction modified layer are used as the starting point of fracture, and the wafer is moved along the first planned dividing line and the second planned dividing line. The second direction-modified layer forming step includes the second planned division line formed as a T-shaped path and intersected by the first planned division line on which the first-direction reformed layer is formed. The inside of the wire forms a T-shaped path processing step of the second-direction modified layer. This T-shaped path processing step is when positioning the condensing point of the laser beam from the back of the wafer in a conical shape near the surface. The first modified layer is formed so that a part of the cone-shaped laser beam does not exceed the first modified layer formed in the first direction, and when the second modified layer is formed by overlapping the first modified layer The second modified layer is formed in such a way that part of the conical shaped laser beam does not exceed the first-direction modified layer formed earlier. Similarly, the end of the second-direction modified layer formed sequentially is formed from the lower layer The reforming layer is formed in an inverted step shape across the upper layer toward the first direction formed first.

According to the wafer processing method of the present invention, the ends of the second-direction modifying layer formed sequentially from the lower layer to the upper layer are formed into an inverted stepped shape toward the first-direction modifying layer formed first. In the quality layer, there will be no conflict between the conical laser beam and the first direction modified layer, so there will be no light leakage caused by the scattering or reflection of the laser beam, which can solve the problem of light leakage attacking the component and causing the component The problem of damage. Therefore, the quality of the device will not be degraded, and an appropriate modified layer can be formed inside the wafer along the planned dividing line.

2: Laser processing device

4: Stationary abutment

6: Rail

8: Y axis moving block

10: Ball screw

11: Semiconductor wafer

11a: surface

11b: back

12: Pulse motor

13a: The first planned dividing line

13b: 2nd planned dividing line

14: Y-axis feed mechanism (Y-axis feed means)

15: Components

16: rail

17: Modified layer in the first direction

18: X axis moving block

19: 2nd direction modified layer

20: Ball screw

21: Component chip

22: Pulse motor

24: Suction table

26: Fixture

28: X-axis feed mechanism (X-axis feed means)

30: Cylindrical support member

32: long column

34: Laser beam irradiation unit

35: Laser beam generating unit

36: Shell

38: Condenser (laser head)

40: camera unit

42: Laser oscillator

44: Repetition frequency setting means

46: Pulse width adjustment means

48: Power adjustment means

50: Split device

52: Frame Keeping Means

54: With expansion means

56: Frame holding member

56a: Mounting surface

58: Fixture

60: expansion drum

62: cover

64: Support flange

66: Drive

68: Air cylinder

70: Piston rod

F: ring frame

LB: Laser beam

T: Cutting tape

X1: direction

Fig. 1 is a perspective view of a laser processing device suitable for implementing the wafer processing method of the present invention.

Figure 2 is a block diagram of the laser beam generating unit.

Fig. 3 is a perspective view of a semiconductor wafer suitable for processing by the wafer processing method of the present invention.

Fig. 4 is a perspective view showing a step of forming a first direction reforming layer.

Fig. 5 is a schematic cross-sectional view showing a step of forming a first direction reforming layer.

Figure 6 is a schematic plan view showing the processing steps of the T-shaped road.

Figure 7 is a cross-sectional view showing the processing steps of the T-shaped path.

Fig. 8 is a perspective view of the dividing device.

Fig. 9 is a sectional view showing the division step.

The embodiments of the present invention will be described in detail below with reference to the drawings. Referring to FIG. 1, a perspective view of a laser processing apparatus 2 suitable for implementing the wafer processing method of the embodiment of the present invention is shown. The laser processing device 2 includes a pair of guide rails 6 which are mounted on a stationary base 4 and extend in the Y-axis direction.

The Y-axis moving block 8 is moved by the Y-axis feeding mechanism (Y-axis feeding means) 14 composed of the ball screw 10 and the pulse motor 12 in the indexing feed direction, that is, the Y-axis direction. A pair of guide rails 16 extending in the X-axis direction are fixed to the Y-axis moving block 8.

The X-axis moving block 18 is driven by the ball screw 20 and pulse The X-axis feeding mechanism (X-axis feeding means) 28 formed by the motor 22 is guided to the guide rail 16 to move in the machining feed direction, that is, the X-axis direction.

A suction table 24 is mounted on the X-axis moving block 18 through a cylindrical support member 30. Plural (four in this embodiment) clamps 26 that clamp the ring frame F shown in FIG. 4 are arranged on the suction table 24.

A long column 32 is erected behind the stationary base 4. The housing 36 of the laser beam irradiation unit 34 is fixed to the long column 32. The laser beam irradiation unit 34 includes a laser beam generating unit 35 housed in a housing 36 and a condenser (laser head) 38 installed at the front end of the housing 36. The condenser 38 is attached to the housing 36 so as to be slightly movable in the vertical direction (Z-axis direction).

The laser beam generating unit 35 is shown in FIG. 2 and includes a laser oscillator 42 such as a YAG laser oscillator or a YVO4 laser oscillator that oscillates a pulsed laser with a wavelength of 1342 nm, a repetition frequency setting means 44, The pulse width adjusting means 46 and the power adjusting means 48 for adjusting the power of the pulsed laser beam oscillated by the laser oscillator 42.

An imaging unit 40 is installed at the front end of the housing 36 of the laser beam irradiation unit 34, and the imaging unit 40 includes a microscope and a camera for imaging the semiconductor wafer 11 held by the chuck table 24. The condenser 38 and the imaging unit 40 are arranged in a line in the X-axis direction.

Referring to FIG. 3, a surface side perspective view of a semiconductor wafer (hereinafter referred to simply as a wafer) 11 suitable for processing by the wafer processing method of the present invention is shown. The surface 11a of the semiconductor wafer 11 is formed with a plurality of first planned dividing lines continuously formed in the first direction 13a; and a plurality of second planned dividing lines 13b formed in a non-continuous direction orthogonal to the first planned dividing line 13a, formed in the area divided by the first planned dividing line 13a and the second planned dividing line 13b Components such as LSI15.

When the wafer processing method of the embodiment of the present invention is implemented, the semiconductor wafer 11 is formed in the form of a frame unit of the dicing tape T whose surface is attached to the outer periphery and attached to the ring frame F. In the form of the frame unit, the semiconductor wafer 11 is placed on the chuck table 24 and sucked and held by the dicing tape T, and the ring frame F is clamped and fixed by the clamp 26.

Although not shown in particular, in the wafer processing method of the present invention, the semiconductor wafer 11 sucked and held on the chuck table 24 is first positioned directly under the imaging unit 40 of the laser processing apparatus 2, and the imaging unit 40 takes an image of the semiconductor wafer 11, and performs alignment of the first planned dividing line 13a and the condenser 38 in the X-axis direction.

Next, the second planned division line 13b extended in a direction orthogonal to the first planned division line 13a after rotating the suction table 24 by 90° is also aligned in the same way, and the alignment data is stored in the mine The RAM of the controller of the injection processing device 2.

The imaging unit 40 of the laser processing apparatus 2 is usually equipped with an infrared camera. Therefore, with this infrared camera, the first and second division plans formed on the surface 11a can be detected through the semiconductor wafer 11 from the back surface 11b side of the semiconductor wafer 11 Lines 13a, 13b.

After the alignment is performed, it is performed along the first planned dividing line 13a, The first direction reforming layer forming step of forming the first direction reforming layer 17 inside the semiconductor wafer 11. In the step of forming the first directionally modified layer, as shown in FIGS. 4 and 5, the condensing point of the laser beam with a wavelength (for example, 1342 nm) that is transparent to the wafer is positioned by the condenser 38 The inside of the semiconductor wafer 11 is irradiated from the back side 11b of the semiconductor wafer 11 to the first planned dividing line 13a, and the chuck table 24 is processed and fed in the direction of arrow X1 in FIG. A first-direction reforming layer 17 along the first planned dividing line 13a is formed in the inside of the inner surface.

Preferably, the concentrator 38 is moved upward in steps, and a plurality of layers of first direction modifying layers 17 along the first planned dividing line 13a are formed inside the semiconductor wafer 11, for example, five first direction modifying layers质层17。 Quality layer 17.

The first direction-modified layer 17 refers to a region formed in a state different from the surroundings in density, refractive index, mechanical strength, or other physical properties, and is formed as a melt-resolidified layer. The processing conditions in this first directionally reforming layer forming step are set as shown below, for example.

Light source: LD excited Q switch Nd: YVO4 pulse laser

Wavelength: 1342nm

Repetition frequency: 50kHz

Average output: 0.5W

Spot diameter: φ3μm

Processing feed speed: 200mm/s

After performing the first direction reforming layer forming step, perform The second direction-modified layer forming step is to extend the end portion in the direction (elongation direction) along the second planned division line 13b that becomes a T-shaped path at the first planned division line 13a, and the semiconductor wafer 11 A laser beam with a transmissive wavelength (for example, 1342 nm) is condensed and irradiated inside the semiconductor wafer 11, and a second-direction modifying layer 19 along the second planned dividing line 13b is formed inside the semiconductor wafer 11 .

In this second direction reforming layer forming step, after rotating the chuck table 24 by 90°, a plurality of second direction reforming layers 19 along the second planned dividing line 13b are formed inside the semiconductor wafer 11.

The second direction-modified layer forming step includes a T-shaped road processing step, which is formed as a T-shaped road on the first planned division line 13a on which the first direction-modified layer 17 is formed and intersected by a second planned division line 13b The second direction reforming layer 19 is formed in the inside.

Referring to Fig. 7, the T-shaped path processing steps will be described. First, as shown in FIG. 7(A), in the T-shaped path processing step, the condensing point of the laser beam LB, which is condensed from the back surface 11b of the semiconductor wafer 11 in the shape of a cone on the surface 11a, is positioned. The first and second direction reforming layer 19 elongated in the second direction is formed so that a part of the conical laser beam LB does not extend beyond the first direction reforming layer 17 formed earlier. That is, the irradiation of the laser beam LB is stopped at the position shown in FIG. 7(A). Fig. 6 shows a schematic plan view of Fig. 7(A).

Next, when the second second direction reforming layer 19 is superimposed on the first second direction reforming layer 19, as shown in FIG. 7(B), part of the laser beam LB condensed in the conical shape is not Will exceed the first formed The second direction-modifying layer 19 is formed as the direction-modifying layer 17.

In the same way, a third, second-directional modified layer 19, a fourth, second-directional modified layer 19, and a fifth, second-directional modified layer 19 are sequentially formed, and the ends of the second-directional modified layer 19 The second direction reforming layer 19 is formed so that the lower layer spreads over the upper layer, and the second direction reforming layer 19 is formed in an inverted step shape toward the first direction reforming layer 17 formed earlier.

Here, the number of apertures of the condenser lens built into the condenser 38 is generally set to a large value, so the laser beam LB is condensed as shown in FIGS. 7(A) and 7(B). Cone shape.

After performing the first direction-modified layer forming step and the second direction-modified layer forming step, a dividing step is performed, which applies external force to the semiconductor wafer 11, and modifies the first direction reforming layer 17 and the second direction The layer 19 is the starting point of breaking, and the semiconductor wafer 11 is broken along the first planned dividing line 13a and the second planned dividing line 13b, and divided into individual element wafers.

This dividing step is performed using the dividing device (stretching device) 50 shown in FIG. 8, for example. The dividing device 50 shown in FIG. 8 is provided with a frame holding means 52 for holding the ring frame F; and a tape expanding means for expanding the cutting tape T attached to the ring frame F held by the frame holding means 52 54.

The frame holding means 52 is composed of a ring-shaped frame holding member 56 and a plurality of jigs 58 arranged on the outer periphery of the frame holding member 56 as fixing means. The upper surface of the frame holding member 56 is formed with a mounting surface 56a on which the ring frame F is mounted. The ring frame F is mounted on the mounting surface 56a. 置面56a上.

Next, the ring-shaped frame F placed on the placing surface 56 a is fixed to the frame holding means 52 by the clamp 58. The frame holding means 52 configured as described above is supported by the belt expansion means 54 so as to be movable in the vertical direction.

The belt expansion means 54 is provided with an expansion drum 60 arranged inside the annular frame holding member 56. The upper end of the expansion drum 60 is closed by a cover 62. The expansion drum 60 has an inner diameter smaller than the inner diameter of the ring frame F and larger than the outer diameter of the semiconductor wafer 11 attached to the dicing tape T mounted on the ring frame F.

The expansion drum 60 has a supporting flange 64 integrally formed at its lower end. The belt expansion means 54 is additionally provided with a driving means 66 that moves the ring-shaped frame holding member 56 in the up and down direction. The driving means 66 is constituted by a plurality of air cylinders 68 arranged on the supporting flange 64, and the piston rod 70 of which is connected to the lower surface of the frame holding member 56.

The driving means 66 composed of a plurality of air cylinders 68 is to set the ring-shaped frame holding member 56 on its placement surface 56a as a reference position that is approximately the same height as the upper end of the expansion drum 60, that is, the surface of the cover 62, and The upper end of the expansion drum 60 is between the expansion positions below a predetermined amount, and moves in the up and down direction.

9, a description will be given of the dividing step of the semiconductor wafer 11 implemented using the dividing device 50 configured as above. As shown in FIG. 9(A), the ring-shaped frame F supporting the semiconductor wafer 11 through the dicing tape T is placed on the placement surface 56a of the frame holding member 56 and fixed by the clamp 58 The member 56 is held in the frame. At this time, the frame holding member 56 is positioned at a reference position where the mounting surface 56 a is substantially the same height as the upper end of the expansion drum 60.

Next, the air cylinder 68 is driven to lower the frame holding member 56 to the expanded position shown in FIG. 9(B). Thereby, since the ring frame F fixed on the mounting surface 56a of the frame holding member 56 is lowered, the cutting tape T attached to the ring frame F is brought into contact with the upper end edge of the expansion drum 60. It is mainly expanded in the radial direction.

As a result, a tensile force is applied radially to the semiconductor wafer 11 attached to the dicing tape T. As shown above, if a tensile force is applied radially to the semiconductor wafer 11, the first direction modifying layer 17 formed along the first planned dividing line 13a and the second direction formed along the second planned dividing line 13b The modified layer 19 becomes the starting point of division, and the semiconductor wafer 11 is broken along the first planned dividing line 13 a and the second planned dividing line 13 b, and divided into individual element wafers 21.

In the above embodiment, the semiconductor wafer 11 is described as the wafer to be processed in the processing method of the present invention. However, the wafer to be processed in the present invention is not limited to this. In the case of an optical element using sapphire as a substrate For other wafers such as wafers, the processing method of the present invention can be similarly applied.

11‧‧‧Semiconductor Wafer

11b‧‧‧Back

17‧‧‧The first direction modified layer

19‧‧‧The second direction modified layer

LB‧‧‧Laser beam

T‧‧‧cutting tape

Claims (1)

A method for processing a wafer using a plurality of first planned dividing lines formed in a first direction and a plurality of second planned dividing lines formed in a second direction intersecting the first direction to divide regions A method for forming a device, wherein at least the second planned dividing line among the first planned dividing line and the second planned dividing line is formed as a non-continuous wafer divided into wafers of individual device wafers, characterized in that: Equipped with: a first directionally modified layer forming step, which is performed by condensing a laser beam of a wavelength that is transparent to the wafer from the back side of the wafer to the inside of the wafer along the first planned division line Irradiating, forming a plurality of layers of first direction reforming layers along the first planned dividing line inside the wafer; a second direction reforming layer forming step, which is performed after the first direction reforming layer forming step , Along the second planned dividing line, a laser beam of a wavelength that is transparent to the wafer is condensed from the back side of the wafer to the inside of the wafer to be irradiated, and formed inside the wafer along the second Dividing the plurality of layers of the planned line of the second direction reforming layer; and the dividing step, which is performed after the first direction reforming layer forming step and the second direction reforming layer forming step are performed, an external force is applied to the wafer to The first direction-modified layer and the second direction-modified layer serve as the starting point of breaking, and the wafer is broken along the first planned dividing line and the second planned dividing line to be divided into individual element wafers. The step of forming the two-directional modified layer includes forming the first planned division line on which the first-directional modified layer is formed as a T-shaped path and intersecting the first The T-shaped path processing step in which the second-direction modified layer is formed inside the planned dividing line. This T-shaped path processing step is performed by condensing the laser beam from the back surface of the wafer in a conical shape on the focus point of the laser beam near the surface When positioning, the first modified layer is formed so that part of the cone-shaped laser beam does not exceed the first modified layer formed in the first direction, and the second modified layer is formed on the first modified layer. The second modified layer is also formed in such a way that a part of the conical shaped laser beam does not exceed the first-direction modified layer formed earlier. Similarly, the ends of the second-direction modified layer formed sequentially The portion extends from the lower layer to the upper layer and is formed in an inverted step shape toward the first direction reforming layer formed earlier.

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