TWI704608B - Wafer processing method - Google Patents

Abstract

The subject of the present invention is to provide a wafer processing method, which can be used in the laser processing of a wafer in which at least one of the planned dividing lines is formed discontinuously, and the end of the one planned dividing line and the other divided planned The line becomes the T-shaped road and collides near the intersection point, which prevents the laser beam from being irradiated to the modified layer that has been formed, prevents the reflection or scattering of the laser beam on the modified layer, and prevents the leakage of light The damage of the components. The solution is a wafer processing method in which at least the second planned dividing line among the first planned dividing line and the second planned dividing line formed by intersecting perpendicularly is a non-continuously formed wafer divided into individual element wafers. It includes a first direction-modifying layer forming step of forming a first-direction reforming layer inside the wafer along the first planned dividing line, and a step of forming a second-direction reforming layer inside the wafer along the second planned dividing line The second direction reforming layer forming step. The second direction-modified layer forming step includes a T-shaped path processing step, which is formed inside the second planned line of division that intersects with the first planned division line on which the first-direction modified layer is formed into a T-shaped path The second direction modified layer. The wafer processing method is to perform a light-shielding treatment step before performing the T-shaped circuit processing step, which is to perform light-shielding treatment on the region of the element on the extension line of the second planned dividing line where the T-shaped circuit is formed on one side of the element and intersected.

Description

Wafer processing method Invention field

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

Background of the invention

The silicon wafer, sapphire wafer, and other wafers formed on the surface of IC, LSI, LED, etc., which are divided into multiple components with predetermined dividing lines, are divided into individual component chips by processing equipment, and Divided device chips are widely used in various electronic devices such as mobile phones and personal computers.

For wafer dicing, a cutting method using a cutting device called a dicing saw is widely used. In the dicing method, a cutting blade with a thickness of about 30μm by fixing abrasive grains such as diamonds with metal or resin is rotated at a high speed of about 30,000 rpm and cut into the wafer, thereby cutting the wafer and dividing the wafer Into a component wafer.

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

The first processing method is a method of positioning the condensing point of a laser beam with a wavelength penetrating into the wafer inside the wafer corresponding to the planned dividing line, and irradiating the laser along the planned dividing line The beam is used to form a modified layer inside the wafer, and then an external force is applied to the wafer by a dividing device, and the wafer is divided into individual device chips using the modified layer as the starting point for division (see, for example, Japanese Patent No. 3408805 ).

The second processing method is a method of irradiating a laser beam of a wavelength (for example, 355 nm) that is absorptive to the wafer to a region corresponding to the planned dividing line to form a processing groove by ablation processing, After that, an external force is applied to divide the wafer into individual element wafers with the processing groove as the starting point for division (see, for example, Japanese Patent Laid-Open No. 10-305420).

In the above-mentioned first machining method, there is no generation of machining chips, and compared with the cutting performed by conventional cutting tools that have been generally used so far, it has the advantages of minimizing the cut line and waterless machining, and it is universal The ground is used.

In addition, in the cutting method performed by the irradiation of the laser beam, there is an advantage that the predetermined dividing line (street) used for the projection wafer (projection wafer) can be discontinuous Structure wafer processing (see, for example, Japanese Patent Laid-Open No. 2010-123723). In the processing of wafers where the planned dividing line is discontinuous, the laser beam output is set to ON/OFF according to the setting of the planned dividing line.

Prior art literature Patent literature

Patent Document 1: Japanese Patent No. 3408805

Patent Document 2: Japanese Patent Laid-Open No. 10-305420

Patent Document 3: Japanese Patent Laid-Open No. 2010-123723

Summary of the invention

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

(1) A T-shaped path is formed on the first planned dividing line in which the first modified layer is formed in the first planned dividing line parallel to one side of the element, and a second planned dividing line is formed inside the intersecting second planned dividing line. When the modified layer is modified, as the condensing point of the laser beam approaches the intersection of the T-shaped path, a part of the laser beam for processing the second planned division line is irradiated on the first modified layer that has been formed, and produces The reflection or scattering of the laser beam causes the light to leak to the device area, and there is a problem that the leaked light causes damage to the device and reduces the quality of the device.

(2) Conversely, before forming the modified layer on the first planned dividing line parallel to one side of the element, form a T-shaped path along the first planned dividing line and hit the second planned dividing line first on the wafer When a modified layer is formed inside the T-shaped road, the modified layer that blocks the cracks (crack) generated from the modified layer formed near the intersection of the T-shaped road does not exist at the intersection of the T-shaped road. There are the following problems: the crack is extended from the intersection of the T-shaped circuit by about 1 to 2 mm and reaches the component, which reduces the quality of the component.

The present invention was made in view of such problems, and its object is to provide a wafer processing method that can perform laser processing on a wafer in which at least one planned dividing line is formed discontinuously. The end of the planned dividing line on one side and the planned dividing line on the other side form a T-shaped path and collide near the intersection point, which prevents the laser beam from being irradiated to the already formed modified layer and prevents thunder in the modified layer. The reflection or scattering of the beam, and prevent damage to the components caused by the leaked light.

According to the present invention, it is possible to provide a method for processing a wafer that divides a wafer into individual element wafers. The wafer is formed on a plurality of first predetermined dividing lines formed in a first direction and formed on and Elements are formed in each area divided by a plurality of second planned dividing lines in the second direction intersecting the first direction, and at least the second planned dividing line among the first planned dividing line and the second planned dividing line The line is formed discontinuously, and the wafer processing method is characterized by comprising: a first directionally modified layer forming step, along the first planned division line, a laser beam with a wavelength penetrating the wafer The light is condensed on the inside of the wafer from the back side of the wafer and irradiated to form a plurality of first-direction reforming layers along the first planned dividing line inside the wafer; the second-direction reforming layer forming step, After the step of forming the first direction-modified layer is performed, the laser beam with a wavelength penetrating the wafer is focused on the inside of the wafer from the back side of the wafer along the second planned dividing line. Irradiating to form a plurality of second-direction reforming layers along the second planned dividing line inside the wafer; and the dividing step, in which the first-direction reforming layer forming step and the second-direction reforming layer are performed After the forming step, an external force is applied to the wafer, and the first directional modified layer and the second directional modified layer are used as breaking starting points, and the wafer is broken along the first planned dividing line and the second planned dividing line The second-direction modified layer forming step includes a T-shaped path processing step, and the T-shaped path processing step is performed in accordance with the first division plan on which the first-direction modified layer is formed. The inside of the second planned dividing line where the line becomes a T-shaped road and intersects is irradiated with a conical laser beam to form a second direction modification layer. The wafer processing method is further equipped with a light-shielding process step. Before performing the T-shaped path processing step, the area of the element on the extension line of the second planned division line is subjected to a light shielding process to shield the penetration of the laser beam.

Preferably, the shading treatment step is to irradiate the aforementioned area with laser light having an absorptive wavelength to process it into a rough surface, and the rough surface scatters the laser beam with a penetrating wavelength to shield light.

In addition, the aforementioned area can be processed into a rough surface by abrasive grains such as sandblasting, and the rough surface scatters a laser beam with a penetrating wavelength to shield light. Alternatively, a mask may be laminated in the aforementioned area to block the laser beam with a penetrating wavelength by the mask.

According to the wafer processing method of the present invention, since the light shielding treatment step is performed before the T-shaped processing step is performed, and the light shielding treatment is performed on the area of the element on the extension line of the second planned dividing line, the The area subjected to this shading treatment blocks the penetration of the laser beam, so the problem of damage to the component caused by the laser beam attacking the component can be solved. Therefore, the quality of the element will not be reduced, and an appropriate modified layer can be formed inside the wafer along the planned dividing line.

2‧‧‧Laser processing device

4‧‧‧Stationary abutment (base)

6, 16‧‧‧Guide rail

8‧‧‧Y-axis moving block

10, 20‧‧‧Ball screw

11‧‧‧wafer

11a‧‧‧surface

11b‧‧‧Back

12, 22‧‧‧Pulse motor

13a‧‧‧First dividing line

13b‧‧‧Second dividing line

14‧‧‧Y axis feed mechanism

15‧‧‧Component

15a‧‧‧Shading treatment part

17‧‧‧The first direction modified layer

18‧‧‧X axis moving block

19‧‧‧The second direction modified layer

21‧‧‧Component chip

24‧‧‧Working clamp

25‧‧‧Suction and retention department

26‧‧‧Fixture

28‧‧‧X axis feed mechanism

30‧‧‧Cylindrical support member

32‧‧‧Pillars

34‧‧‧Laser beam irradiation unit

35‧‧‧Laser beam generating unit

36‧‧‧Shell

38‧‧‧Concentrator

40‧‧‧Camera unit

42‧‧‧Laser oscillator

44‧‧‧Repeat frequency setting equipment

46‧‧‧Pulse width adjustment equipment

48‧‧‧Power adjustment equipment

50‧‧‧Splitting device

52‧‧‧Frame holding equipment

54‧‧‧Tape expansion equipment

56‧‧‧Frame holding member

56a‧‧‧Mounting surface

58‧‧‧Fixture

60‧‧‧Expansion cylinder

62‧‧‧Lid

64‧‧‧Support flange

66‧‧‧Drive equipment

68‧‧‧Cylinder

70‧‧‧Piston rod

F‧‧‧Ring frame

LB‧‧‧Laser beam

T‧‧‧Cutting tape

X1‧‧‧Arrow

X, Y, Z‧‧‧direction

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

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

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.

Fig. 6 is a schematic plan view showing a T-shaped path processing step.

Fig. 7 is a schematic diagram showing the steps of masking processing.

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

9(A) and (B) are cross-sectional views showing the dividing step.

The form used to implement the invention

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

The Y-axis moving block 8 uses a Y-axis feed mechanism (Y-axis feed device) 14 composed of a ball screw 10 and a pulse motor 12 to move in the indexing feed direction (That is, the Y axis direction) moves. A pair of guide rails 16 elongated in the X-axis direction are fixed to the Y-axis moving block 8.

The X-axis moving block 18 uses an X-axis feed mechanism (X-axis feed device) 28 composed of a ball screw 20 and a pulse motor 22, and is guided by the guide rail 16 and moves in the processing feed direction (that is, the X-axis Direction) to move.

A work clamp table 24 is mounted on the X-axis moving block 18 through a cylindrical support member 30. The work clamp table 24 is provided with a plurality of clamps 26 (four in this embodiment) capable of clamping the ring frame F shown in FIG. 4.

A pillar 32 is erected on the rear of the base 4. The housing 36 of the laser beam irradiation unit 34 is fixed on the pillar 32. The laser beam irradiation unit 34 includes a laser beam generating unit 35 housed in the casing 36 and a condenser (laser head) 38 installed at the front end of the casing 36. The condenser 38 is mounted to the housing 36 in a manner that can be slightly moved in the vertical direction (Z-axis direction).

As shown in FIG. 2, the laser beam generating unit 35 includes: a YAG laser oscillator or a YVO4 laser oscillator 42 that can oscillate a pulsed laser with a wavelength of 1342nm, a repetition frequency setting device 44, The pulse width adjustment device 46, the power adjustment device 48 that can adjust the power of the pulse laser beam generated by the oscillation of the laser oscillator 42.

The front end of the casing 36 of the laser beam irradiation unit 34 is provided with an imaging unit 40 equipped with a microscope and a camera for imaging the wafer 11 held on the work chuck 24. The condenser 38 and the imaging unit 40 are arranged in a row in the X-axis direction.

3, it shows the surface side of a semiconductor wafer (hereinafter sometimes referred to as a wafer) 11 suitable for processing by the wafer processing method of the present invention Stereograph. On the surface 11a of the wafer 11 are formed a plurality of first planned dividing lines 13a continuously formed in the first direction, and a plurality of first planned dividing lines 13a formed discontinuously in a direction perpendicular to the first planned dividing line 13a. The planned dividing line 13b is divided into two, and an element 15 such as an LSI is formed in an area divided by the first planned dividing line 13a and the second planned dividing line 13b.

The wafer processing method suitable for the implementation of the embodiment of the present invention is to make the wafer 11 into a frame unit in which the surface of the wafer 11 is attached to the dicing tape T which has been attached to the ring frame F with the outer peripheral part thereof. In the form of the frame unit, the wafer 11 is placed on the work clamp table 24 and held by suction via 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 wafer 11 attracted and held on the work chuck table 24 is first positioned directly under the imaging unit 40 of the laser processing device 2, and By imaging the wafer 11 by the imaging unit 40, the alignment of the first planned dividing line 13a and the condenser 38 in the X-axis direction is performed.

Next, after rotating the work clamp table 24 by 90°, the same calibration is performed on the second planned dividing line 13b extending in the direction perpendicular to the first planned dividing line 13a, and the calibration data is stored in the laser processing The RAM of the controller of device 2.

Since the imaging unit 40 of the laser processing apparatus 2 is usually equipped with an infrared camera, the infrared camera can penetrate the wafer 11 from the back surface 11b side of the wafer 11 to detect the first and second divisions formed on the surface 11a. Schedule lines 13a, 13b.

After the calibration is performed, the first direction-modifying layer forming step of forming the first direction-modifying layer 17 inside the wafer 11 along the first planned dividing line 13a is performed. In the step of forming the first direction-modifying layer, as shown in FIGS. 4 and 5, the laser beam with a wavelength (for example, 1342nm) that is transparent to the wafer is condensed by the condenser 38. Positioned inside the wafer 11, and by irradiating the first planned dividing line 13a from the back side 11b of the wafer 11, the work chuck 24 is processed and fed in the direction of arrow X1 in FIG. In the inside of 11, a first direction reforming layer 17 is formed along the first planned dividing line 13a.

Preferably, the concentrator 38 is moved upward in stages to form a plurality of layers of the first-direction reforming layer 17 along the first planned dividing line 13a in the inside of the wafer 11, for example, a five-layer first Direction modification layer 17.

The modified layer 17 refers to a region where the density, refractive index, mechanical strength, or other physical properties have become different from the surroundings, 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 excitation Q switch Nd: YVO4 pulse laser

Wavelength: 1342nm

Repetition frequency: 50kHz

Average output: 0.5W

Condenser point diameter: φ 3μm

Processing feed speed: 200mm/sec

After the first direction-modified layer formation step is performed, the second direction-modified layer formation step is performed. The second direction-modified layer formation step is that the end along the extension direction (elongation direction) is aligned with the first planned dividing line 13a becomes a T road and touches Reaching the second planned dividing line 13b, a laser beam with a wavelength (for example, 1342 nm) that is transparent to the wafer 11 is focused on the inside of the wafer 11 and irradiated to form a laser beam along the inside of the wafer 11 The second-direction reforming layer 19 is divided into two planned lines 13b.

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

The second direction-modified layer forming step includes a T-shaped road processing step. The T-shaped road processing step is a T-shaped road that intersects with the first planned dividing line 13a on which the first directionally modified layer 17 is formed. The second direction-modified layer 19 is formed inside the planned split line 13b.

In the wafer processing method of the present invention, the second direction is formed inside the second planned dividing line 13b that forms a T-shaped path on the first planned dividing line 13a on which the first-direction modified layer 17 is formed Before the T-shaped processing step of the modified layer 19, as shown in FIG. 7, a light-shielding processing step is performed. The light-shielding processing step is performed on the area 15a on the back side of the element 15 on the extension of the second planned dividing line 13b. Shading treatment for penetration shading of laser beams.

The first embodiment of this light-shielding processing step is to irradiate the region 15a of the element 15 with a laser beam having an absorptive wavelength (for example, 355nm) for the wafer 11 and process the region 15a into a rough surface. The rough surface scatters and shields the laser beam with penetrating wavelength.

In other embodiments of the shading treatment step, the area 15a can be processed into a rough surface by making abrasive grains collide with the area 15a of the element 15 by sandblasting, and the rough surface can make the laser with penetrating wavelength The light beam is scattered to block the light. Alternatively, it can also be made into a laminated mask, which blocks the penetration of the laser beam of a wavelength that has penetrability to the region 15a of the element 15.

After the above-mentioned light-shielding processing steps have been performed, as shown in the schematic plan view of FIG. 6, a T-shaped path processing step is performed. The T-shaped path processing step is performed on the first planned division line 13a on which the first direction reforming layer 17 is formed. The second direction reforming layer 19 is formed inside the second planned dividing line 13b that forms the T-shaped path and intersects.

Preferably, the first direction reforming layer 17 and the second direction reforming layer 19 are each formed in plural layers. In the T-shaped path processing step included in the second directionally modified layer forming step, as shown in FIG. 7, the T-shaped path is formed on one side of the element 15 and intersected on the extension of the second planned dividing line 13b. The area 15a of the element 15 is subjected to light-shielding treatment, so the laser beam in the T-shaped path forming step will be blocked by this light-shielding treatment part, and the element 15 will not be substantially damaged. Therefore, the quality of the element 15 will not be degraded, and appropriate modified layers 17 and 19 can be formed inside the wafer 11 along the planned dividing line.

After performing the first direction-modified layer forming step and the second direction-modified layer forming step, a dividing step is performed. The dividing step is to apply an external force to the wafer 11 and change the modified layer 17 and the second direction in the first direction. The quality layer 19 serves as a breaking point, and the wafer 11 is broken along the first planned dividing line 13a and the second planned dividing line 13b to be divided into individual element wafers.

In this dividing step, a dividing device (expansion device) 50 as shown in FIG. 8 is used for implementation. The dividing device 50 shown in FIG. 8 includes a frame holding device 52 that holds a ring frame F, and a tape expanding device that expands the dicing tape T mounted on the ring frame F held by the frame holding device 52 54.

The frame holding device 52 is composed of a ring-shaped frame holding member 56 and a plurality of jigs 58 as fixing devices arranged on the outer periphery of the frame holding member 56. A mounting surface 56a on which the ring frame F is mounted is formed on the upper surface of the frame holding member 56, and the ring frame F can be mounted on this mounting surface 56a.

In addition, the ring-shaped frame F that has been placed on the placement surface 56 a is fixed to the frame holding device 52 by the clamp 58. The frame holding device 52 thus constituted is supported by the tape expansion device 54 so as to be movable in the vertical direction.

The tape expansion device 54 includes an expansion cylinder 60 arranged inside the ring-shaped frame holding member 56. The upper end of the expansion cylinder 60 is closed by a cover 62. The expansion cylinder 60 has an inner diameter smaller than the inner diameter of the ring frame F and larger than the outer diameter of the wafer 11 attached to the dicing tape T attached to the ring frame F.

The expansion cylinder 60 has a support flange 64 integrally formed at its lower end. The tape expansion device 54 further includes a drive device 66 that moves the ring-shaped frame holding member 56 in the vertical direction. The driving device 66 is composed of a plurality of air cylinders 68 arranged on the supporting flange 64, and the piston rod 70 thereof is connected to the lower surface of the frame holding member 56.

The drive device 66 composed of a plurality of air cylinders 68 sets the ring-shaped frame holding member 56 at the reference position where the mounting surface 56a and the surface of the cover 62 which is the upper end of the expansion cylinder 60 become substantially the same height and the ratio The expansion cylinder 60 moves in the vertical direction between expansion positions by a predetermined amount below the upper end.

With reference to FIG. 9, the step of dividing the wafer 11 performed using the dividing device 50 configured as described above will be described. As shown in FIG. 9(A), the ring-shaped frame F supporting the wafer 11 through the dicing tape T is placed on the placement surface 56a of the frame holding member 56 and fixed to the frame holding member 56 by a clamp 58 . At this time, the frame holding member 56 positions its placement surface 56a at a reference position that is approximately the same height as the upper end of the expansion cylinder 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, the ring frame F fixed on the mounting surface 56a of the frame holding member 56 is lowered, so the dicing tape T mounted on the ring frame F will abut against the upper end edge of the expansion cylinder 60 and mainly face The radial direction is expanded.

As a result, the tensile force acts radially on the wafer 11 attached to the dicing tape T. When the tensile force is radially applied to the wafer 11 in this way, the first directional reforming layer 17 formed along the first planned dividing line 13a and the formed along the second planned dividing line 13b The second direction reforming layer 19 serves as the starting point of division, and the wafer 11 is broken along the first planned division line 13 a and the second planned division line 13 b to be divided into individual element wafers 21.

In the above-mentioned embodiment, although the semiconductor wafer 11 that becomes the processing object of the processing method of the present invention is described as a wafer, the wafer that becomes the processing object of the present invention is not limited to this. For sapphire The processing method of the present invention can be similarly applied to other wafers such as optical device wafers that are substrates.

13a‧‧‧First dividing line

13b‧‧‧Second dividing line

15‧‧‧Component

15a‧‧‧Shading treatment part

Claims (4)

A method for processing a wafer, which can divide the wafer into individual element wafers. The wafer is formed on a plurality of first dividing lines formed in a first direction and formed at an intersection with the first direction. Elements are formed in each area divided by a plurality of second planned dividing lines in the second direction, and at least the second planned dividing line among the first planned dividing line and the second planned dividing line is formed discontinuously , The wafer processing method is characterized by comprising: a first directionally modified layer forming step, along the first planned dividing line, the laser beam having a wavelength penetrating the wafer from the back side of the wafer The light is concentrated on the inside of the wafer and irradiated to form a plurality of first-direction reforming layers along the first planned dividing line inside the wafer; the second-direction reforming layer forming step is performed in the first direction After the reforming layer formation step, along the second planned dividing line, the laser beam with a wavelength that is transparent to the wafer is condensed into the inside of the wafer from the back side of the wafer and irradiated to the wafer A plurality of second direction reforming layers along the second planned dividing line are formed inside; and the dividing step, after performing the first direction reforming layer forming step and the second direction reforming layer forming step, the crystal The circle imparts external force, and the first direction modified layer and the second direction modified layer are used 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 one Device wafers, the second direction reforming layer forming step includes a T-shaped path processing step, the The T-shaped path processing step is to irradiate a conical laser beam into the inside of the second planned line of division that intersects with the first planned line of division on which the first direction-modifying layer is formed to form a T-shaped path to form a second Directional modification layer, the wafer processing method is further equipped with a light-shielding processing step, the light-shielding processing step is to perform the laser beam on the area of the element on the extension line of the second planned dividing line before the T-shaped processing step The shading treatment of penetrating shading. The wafer processing method of claim 1, wherein the light-shielding treatment step is to irradiate the aforementioned area of the device with laser light having an absorptive wavelength to process the area into a rough surface, and the rough surface is used to make the The laser beam of transparent wavelength is scattered to block light. The wafer processing method of claim 1, wherein the shading treatment step is to process the aforementioned area into a rough surface by abrasive grains, and the rough surface is used to scatter a laser beam with a penetrating wavelength to shield light. The wafer processing method of claim 1, wherein the light-shielding processing step is to laminate a mask in the aforementioned area to shield a laser beam with a transparent wavelength.

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