TW201721729A - Wafer processing method for preventing device damage caused by light leakage - Google Patents

Abstract

The present invention provides a wafer processing method that, during performing laser processing on a wafer by forming the predetermined dividing lines on at least one side as non-continuous, may prevent the modification layer from being irradiated by laser beam, which is formed near the intersection where the end of the predetermined dividing line on one side is formed as a T-junction with the predetermined dividing line on the other side, so as to prevent the reflection or scattering of laser beam on the modification layer and avoid the device damage caused by light leakage.The wafer processing method for dividing a wafer having at least the second predetermined dividing lines among the first predetermined dividing lines and the second predetermined dividing lines that are formed as orthogonal to be formed as non-continuous into each device chip includes: a first direction modification layer forming step for forming the first direction modification layer inside the wafer along the first predetermined dividing lines; and, a second direction modification layer forming step for forming the second direction modification layer inside the wafer along the second predetermined dividing lines. The second direction modification layer forming step includes a T-junction processing step for forming a T-junction for the first predetermined dividing lines formed with the first direction modification layer to be crossed with the second predetermined dividing lines formed with the second direction modification layer therein. The T-junction processing step is to make the ends of a plurality of second direction modification layers from the lower layers to the upper layers formed as an inversed-step shape facing the previously formed first direction modification layers.

Description

Wafer processing method

The present invention relates to a method of processing wafers such as tantalum wafers and sapphire wafers.

A wafer such as an IC, an LSI, or an LED, which is formed by dividing a predetermined line to be formed on a surface, is formed into a wafer of a sapphire wafer or a sapphire wafer by a processing device, and the divided component wafer is widely used. Use in various electronic devices such as mobile phones and personal computers.

In the division of wafers, a cutting method using a cutting device called a cutter is widely used. In the dicing method, a polishing blade such as a diamond is fixed by a metal or a resin to form a cutting blade having a thickness of about 30 μm, and is rotated at a high speed of about 30,000 rpm, and is cut into a wafer to cut the wafer and crystallize the wafer. The circle is divided into individual component 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. The first and second processing methods described below are known as a method of dividing a wafer into individual element wafers by using a laser beam.

The first processing method is a wavelength that is transparent to the wafer. The condensed spot of the laser beam (for example, 1342 nm) is positioned inside the wafer corresponding to the planned dividing line, irradiates the laser beam along the dividing line, forms a modified layer inside the wafer, and then passes through the dividing device. A method of applying an external force to a wafer and dividing the wafer into individual element wafers using the modified layer as a starting point of the division (see, for example, Japanese Patent No. 3408805).

In the second processing method, a laser beam having a wavelength (for example, 355 nm) that is absorptive to a wafer is irradiated onto a region corresponding to a predetermined dividing line, and a processing groove is formed by ablation processing, and then an external force is applied, and the processing groove is used as a processing groove. A method of dividing a wafer into individual element wafers by dividing a starting point (see, for example, Japanese Patent Laid-Open No. Hei 10-305420).

In the first processing method described above, there is an advantage that the machining chips are not generated, and the cutting line is minimized or water-free, which is conventionally used for cutting by a generally used cutting blade, and is widely used.

Further, in the dicing method by the irradiation of the laser beam, there is an advantage that a wafer having a predetermined dividing line (street) which is substituted for the projection wafer can be processed (see, for example, Japanese Special Open 2010-123723). In the processing in which the predetermined dividing line is a discontinuous wafer, the output of the laser beam is turned ON/OFF according to the setting of the dividing line.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent No. 3408805

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

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2010-123723

However, in the dividing line to be continuously extended in the first direction, the predetermined dividing line extending in the second direction is formed in the vicinity of the intersection of the T-shaped road and the following, and the following problems are caused.

(1) The first divided planned line in which the first modified layer is formed first in the first divided planned line parallel to one side of the element forms a T-shaped path, and the inside of the second divided planned line intersects to form the second In the reforming layer, as the condensed point of the laser beam approaches the intersection of the T-shaped path, a portion of the laser beam that has been processed by the second dividing line is irradiated to the formed first modified layer, and a laser beam is generated. The reflection or scattering causes light leakage in the element region, and there is a problem that the element is damaged due to the light leakage, and the quality of the element is lowered.

(2) Conversely, before the modified layer is formed on the first predetermined dividing line parallel to one side of the element, the second dividing line is formed along the first dividing line to form a T-shaped path. The inner layer of the circle first forms a modified layer, and the modified layer that blocks the progress of the crack caused by the modified layer formed at the intersection of the T-shaped path does not exist at the intersection of the T-shaped path, and the intersection of the T-shaped path The crack is elongated by about 1 to 2 mm to reach the component, which has a problem of lowering the quality of the component.

The present invention has been made in view of the circumstances as described above, and an object thereof is to provide an end portion for suppressing a line to be divided at one side when laser processing is performed on a wafer in which at least one of the planned dividing lines is formed as a discontinuous line The modified layer formed near the intersection where the other predetermined dividing line is formed into a T-shaped path is irradiated with the laser beam, which prevents reflection or scattering of the laser beam in the reforming layer, and prevents components caused by light leakage. The processing method of damaged wafers.

According to the present invention, there is provided a method of processing a wafer by using a plurality of first division planned lines formed in a first direction and a plurality of second division planned lines formed in a second direction intersecting the first direction A method of processing a wafer in which each of the first divided line and the second divided line is formed into a discontinuous wafer into wafers of the respective element wafers A first direction reforming layer forming step of concentrating a laser beam having a wavelength that is transparent to a wafer along a first side of the predetermined dividing line from a back side of the wafer to Irradiating inside the wafer, forming a first direction modifying layer along a plurality of layers along the first dividing line in the wafer; and forming a second direction modifying layer in the first direction After the step of forming the layer, the laser beam having a wavelength that is transparent to the wafer is condensed from the back side of the wafer to the inside of the wafer along the second predetermined line, and is formed inside the wafer. The second direction of the plurality of layers along the second dividing line And a dividing step of applying an external force to the wafer after performing the first direction modifying layer forming step and the second direction modifying layer forming step, and modifying the first direction modifying layer and the second layer The direction modifying layer serves as a breaking starting point and advances the wafer along the first dividing line and the second dividing line The second direction reforming layer forming step includes dividing the first dividing line formed in the first direction modifying layer into a T-shaped path and intersecting the second dividing line. Forming a T-shaped path processing step of the second direction modifying layer in the interior of the line, the T-shaped path processing step is to position the spotting point of the laser beam which is converged by the back surface of the wafer in a conical shape near the surface, Forming a first modified layer so that a part of the cone-shaped laser beam does not extend beyond the first-direction modified layer formed first, and when the second modified layer is formed by overlapping the first modified layer A part of the cone-shaped condensed laser beam forms a second modified layer so as not to extend beyond the first-direction modified layer formed first, and the end portion of the second-direction modified layer sequentially formed in the same manner is composed of a lower layer The first direction reforming layer formed first toward the upper layer and formed toward the first direction is formed in an inverted step shape.

According to the wafer processing method of the present invention, the end portions of the second direction reforming layer sequentially formed are formed in an inverted step shape by the lower layer from the upper layer toward the first direction first modified layer, so that the second direction is changed. In the case of the mass layer, there is no case where the cone beam of the cone shape collides with the first direction reforming layer, so that light leakage due to scattering or reflection of the laser beam does not occur, and the light leakage attacking element can be solved to cause the component to be caused. The problem of damage. Therefore, there is no case where the quality of the element is lowered, and an appropriate modified layer can be formed inside the wafer along the dividing line.

2‧‧‧ Laser processing equipment

4‧‧‧Standing abutment

6‧‧‧ rail

8‧‧‧Y-axis moving block

10‧‧‧Rolling screw

11‧‧‧Semiconductor wafer

11a‧‧‧ surface

11b‧‧‧Back

12‧‧‧ pulse motor

13a‧‧‧1st dividing line

13b‧‧‧2nd dividing line

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

15‧‧‧ components

16‧‧‧rails

17‧‧‧1st direction modified layer

18‧‧‧X-axis moving block

19‧‧‧2nd direction modified layer

20‧‧‧Ball screw

21‧‧‧Component chip

22‧‧‧ pulse motor

24‧‧‧Sucker table

26‧‧‧Clamp

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

30‧‧‧Cylindrical support members

32‧‧‧Long column

34‧‧‧Laser beam irradiation unit

35‧‧‧Laser beam generating unit

36‧‧‧Shell

38‧‧‧ concentrator (laser head)

40‧‧‧ camera unit

42‧‧‧Laser oscillator

44‧‧‧Repetition frequency setting means

46‧‧‧ pulse width adjustment means

48‧‧‧Power adjustment means

50‧‧‧Splitting device

52‧‧‧Framework means

54‧‧‧With expansion means

56‧‧‧Frame holding components

56a‧‧‧Loading surface

58‧‧‧Clamp

60‧‧‧Expanding drum

62‧‧‧ Cover

64‧‧‧Support flange

66‧‧‧Drive means

68‧‧‧Air cylinder

70‧‧‧ piston rod

F‧‧‧Ring frame

LB‧‧‧Laser beam

T‧‧‧ cutting tape

X1‧‧‧ direction

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a laser processing apparatus suitable for carrying out the method of processing a wafer 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 the processing steps of the T-shaped path.

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

Figure 8 is a perspective view of the dividing device.

Figure 9 is a cross-sectional view showing the dividing step.

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 carrying out a method of processing a wafer according to an embodiment of the present invention is shown. The laser processing apparatus 2 includes a pair of guide rails 6 that are mounted on the stationary base 4 and elongated in the Y-axis direction.

The Y-axis moving block 8 is moved in the index feeding direction, that is, in the Y-axis direction by the Y-axis feeding mechanism (Y-axis feeding means) 14 composed of the ball screw 10 and the pulse motor 12. 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 is driven by the ball screw 20 and the pulse The X-axis feed mechanism (X-axis feed means) 28 constituted by the motor 22 is guided to the guide rail 16 to move in the machining feed direction, that is, in the X-axis direction.

The chuck table 24 is loaded through the cylindrical support member 30 on the X-axis moving block 18. A plurality of (four in the present embodiment) jigs 26 sandwiching the annular frame F shown in Fig. 4 are disposed on the chuck table 24.

A long post 32 is attached to the rear of the base 4. The outer casing 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 the casing 36, and a concentrator (laser head) 38 attached to the front end of the casing 36. The concentrator 38 is attached to the outer casing 36 in a fretting direction in the vertical direction (Z-axis direction).

As shown in FIG. 2, the laser beam generating unit 35 includes a laser oscillator 42 such as a YAG laser oscillator or a YVO4 laser oscillator that oscillates a pulsed laser having 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 provided at the front end of the outer casing 36 of the laser beam irradiation unit 34. The imaging unit 40 includes a microscope that images the wafer 11 held by the chuck table 24, and a camera. The concentrator 38 and the imaging unit 40 are arranged in a line in the X-axis direction.

Referring to Fig. 3, a perspective view of a surface side of a semiconductor wafer (hereinafter simply referred to as a wafer) 11 suitable for processing by the wafer processing method of the present invention is shown. a plurality of first division planned lines 13a formed in the first direction to be continuous in the surface 11a of the wafer 11; And a plurality of second division planned lines 13b which are formed in a direction orthogonal to the first division planned line 13a, and an LSI or the like is formed in a region partitioned by the first division planned line 13a and the second division planned line 13b. Element 15.

When the wafer processing method according to the embodiment of the present invention is carried out, the wafer 11 is formed into a frame unit whose surface is adhered to the adhesive tape which is attached to the annular frame F at the outer peripheral portion, that is, the dicing tape T. In the form of the frame unit, the wafer 11 is placed on the chuck table 24, sucked and held by the dicing tape T, and the annular frame F is fixed by being clamped by the jig 26.

Although not specifically illustrated, in the wafer processing method of the present invention, first, the wafer 11 sucked and held by the chuck table 24 is positioned directly under the image pickup unit 40 of the laser processing apparatus 2, by the image pickup unit 40. The wafer 11 is imaged, and alignment of the first division planned line 13a and the condenser 38 in the X-axis direction is performed.

Then, after the chuck table 24 is rotated by 90°, the second dividing line 13b that is extended in a direction orthogonal to the first dividing line 13a is also subjected to the same alignment, and the aligned data is stored in the mine. The RAM of the controller of the processing device 2.

Since the imaging unit 40 of the laser processing apparatus 2 is usually provided with an infrared camera, the infrared camera can detect the first and second division planned lines 13a formed on the surface 11a by passing the wafer 11 from the back surface 11b side of the wafer 11. , 13b.

After the alignment is performed, the first direction modification is performed along the first division planned line 13a to form the first direction modifying layer 17 inside the wafer 11. Layer formation step. In the first direction reforming layer forming step, as shown in FIGS. 4 and 5, the condensing point of the laser beam having a wavelength (for example, 1342 nm) that is transparent to the wafer is positioned by the concentrator 38. In the inside of the wafer 11, the first divided planned line 13a is irradiated from the back surface 11b side of the wafer 11, and the chuck table 24 is processed and fed in the direction of the arrow X1 in Fig. 5, thereby forming the inside of the wafer 11. The layer 17 is modified along the first direction of the first division planned line 13a.

Preferably, the concentrator 38 is moved stepwise upward, and a first direction modifying layer 17 along a plurality of layers along the first dividing line 13a is formed inside the wafer 11, for example, a fifth layer is modified in the first direction. Layer 17.

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

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

Wavelength: 1342nm

Repeat frequency: 50kHz

Average output: 0.5W

Converging spot diameter: φ3μm

Processing feed rate: 200mm/s

After the first direction reforming layer forming step is performed, the second direction modifying layer forming step is performed, and the end portion extending in the direction (elongating direction) is brought into a T-shaped path along the first dividing planned line 13a to be in contact with each other. 2nd The predetermined line 13b is divided, and a laser beam having a wavelength (for example, 1342 nm) that is transparent to the wafer 11 is condensed and irradiated inside the wafer 11, and a predetermined line along the second dividing line 13b is formed inside the wafer 11. The second direction is the modified layer 19.

In the second direction reforming layer forming step, after the chuck table 24 is rotated by 90°, the second direction modifying layer 19 along the plurality of layers of the second dividing line 13b is formed inside the wafer 11.

The second direction reforming layer forming step includes a T-shaped path processing step in which the first dividing planned line 13a in which the first direction modifying layer 17 is formed is formed as a T-shaped path and intersects the second dividing line 13b. The second direction reforming layer 19 is formed inside.

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

Next, when the second modified layer 19 is formed on the first modified layer 19, as shown in FIG. 7(B), a part of the laser beam LB collected in a conical shape does not exceed the first direction formed first. The second modified layer 19 is formed in such a manner as to modify the layer 17.

Similarly, the third modified layer 19 and the fourth modified form are sequentially formed. In the layer 19 and the fifth modified layer 19, the second direction is modified so that the end portion of the modified layer 19 in the second direction is formed by the lower layer extending over the upper layer and toward the first direction, and the modified layer 17 is formed in an inverted step shape. Layer 19.

Here, the number of openings of the condensing lens built in the concentrator 38 is generally set to a large value, and therefore the laser beam LB is condensed as shown in FIG. 7(A) and FIG. 7(B). Conical shape.

After performing the first direction reforming layer forming step and the second direction modifying layer forming step, a dividing step is performed to apply an external force to the wafer 11 and the first direction modifying layer 17 and the second direction modifying layer Reference numeral 19 denotes a breaking starting point, and the wafer 11 is broken along the first dividing line 13a and the second dividing line 13b, and is divided into individual element wafers.

This dividing step is carried out using, for example, a dividing device (stretching device) 50 shown in Fig. 8. The dividing device 50 shown in FIG. 8 includes a frame holding means 52 for holding the annular frame F, and a belt expanding means for expanding the dicing tape T attached to the annular frame F held by the frame holding means 52. 54.

The frame holding means 52 is composed of an annular frame holding member 56 and a plurality of jigs 58 which are disposed as fixing means on the outer periphery of the frame holding member 56. A mounting surface 56a on which the annular frame F is placed is formed on the upper surface of the frame holding member 56, and the annular frame F is placed on the mounting surface 56a.

Next, the annular frame F placed on the placing surface 56a is fixed to the frame holding means 52 by the jig 58. The frame holding means 52 constructed as shown above can be moved up and down by the belt expanding means 54 Support the mobile site.

The belt expansion means 54 is provided with an expansion drum 60 disposed 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 annular frame F and larger than the outer diameter of the wafer 11 attached to the dicing tape T attached to the annular frame F.

The expansion drum 60 has a support flange 64 integrally formed at a lower end thereof. The belt expanding means 54 is further provided with a driving means 66 for moving the annular frame holding member 56 in the vertical direction. The driving means 66 is composed of a plurality of air cylinders 68 disposed on the support flange 64, and the piston rod 70 is coupled to the lower surface of the frame holding member 56.

The driving means 66 composed of the plurality of air cylinders 68 is a reference position at which the annular frame holding member 56 has substantially the same height as the upper surface of the expansion drum 60, that is, the surface of the cover 62, and the mounting surface 56a. It moves between the upper and lower directions than the upper end of the expansion drum 60 between the expansion positions below the predetermined amount.

Referring to Fig. 9, a division step using the wafer 11 constructed by the dividing device 50 as described above will be described. As shown in FIG. 9(A), the annular frame F supporting the wafer 11 through the dicing tape T is placed on the mounting surface 56a of the frame holding member 56, and is fixed to the frame holding member 56 by the jig 58. At this time, the frame holding member 56 is positioned at a reference position at which the mounting surface 56a 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, as it will be fixed Since the annular frame F on the mounting surface 56a of the frame holding member 56 is lowered, the dicing tape T attached to the annular frame F abuts on the upper end edge of the expansion drum 60 and is mainly expanded in the radial direction.

As a result, the tensile force is radially applied to the wafer 11 attached to the dicing tape T. As described above, when the tensile force is radially applied to the wafer 11, the first direction reforming layer 17 formed along the first dividing line 13a and the second direction formed along the second dividing line 13b are changed. The material layer 19 is a division start point, and the wafer 11 is broken along the first division planned line 13a and the second division planned line 13b, and is divided into the respective element wafers 21.

In the above-described embodiment, the semiconductor wafer 11 is described as a wafer to be processed by the processing method of the present invention. However, the wafer to be processed in the present invention is not limited thereto, and an optical element having sapphire as a substrate is used. The processing method of the present invention can be applied similarly to other wafers such as wafers.

11‧‧‧Semiconductor wafer

11b‧‧‧Back

17‧‧‧1st direction modified layer

19‧‧‧2nd direction modified layer

LB‧‧‧Laser beam

T‧‧‧ cutting tape

Claims (1)

A method of processing a wafer by using a plurality of first division planned lines formed in a first direction and regions partitioned by a plurality of second division planned lines formed in a second direction intersecting the first direction Forming a device, and processing a wafer in which at least the second divided planned line and the second divided planned line are formed into a discontinuous wafer into wafers of the respective element wafers, wherein: The first direction reforming layer forming step is configured to collect a laser beam having a wavelength that is transparent to the wafer from the back side of the wafer to the inside of the wafer along the first dividing line. Irradiation, a first direction reforming layer of a plurality of layers along the first dividing line is formed inside the wafer; and a second direction modifying layer forming step is performed after the step of forming the first direction modifying layer A laser beam having a wavelength that is transparent to the wafer is condensed from the back side of the wafer to the inside of the wafer along the second division planned line, and is formed along the second inside the wafer. Dividing the second direction modifying layer of the plurality of layers of the predetermined line; and dividing the step After performing the first direction modifying layer forming step and the second direction modifying layer forming step, an external force is applied to the wafer, and the first direction modifying layer and the second direction modifying layer are broken. Breaking the starting point and breaking the wafer along the first dividing line and the second dividing line to divide into the respective element wafers, and the second direction modifying layer forming step includes forming the first direction The first dividing line of the quality layer is formed as a T-shaped road and intersects the first The inside of the two-divided predetermined line forms a T-shaped path processing step of the second-direction reforming layer, and the T-shaped path processing step is performed by concentrating the spot of the laser beam which is converged by the back surface of the wafer in a conical shape near the surface. At the time of positioning, the first modified layer is formed such that a part of the cone-shaped laser beam does not extend beyond the first direction-modified layer formed first, and the second modified layer is formed by overlapping the first modified layer. At the same time, the second modified layer is formed so that a part of the laser beam condensed in the conical shape does not extend beyond the first direction modified layer formed first, and the end of the second direction modified layer which is sequentially formed in the same manner The first direction reforming layer formed in the first layer from the lower layer to the upper layer is formed in an inverted step shape.