TWI402128B - Laser processing method - Google Patents

Description

Laser processing method Field of invention

The present invention relates to a laser processing method in which a laser beam is irradiated along a planned dividing line formed on a workpiece such as a semiconductor wafer, and a deteriorated layer is formed inside the wafer along a dividing line.

Background of the invention

In a wafer manufacturing process of a semiconductor device, a plurality of rectangular regions are formed along a predetermined line portion arranged in a lattice shape on the surface of a substantially disk-shaped semiconductor wafer, and ICs, LSIs, and the like are formed in the rectangular regions. After an electronic circuit and a minute motor component called a MEMS (Micro Electro Mechanical System), the wafer is cut along a predetermined dividing line, and the rectangular region is used as a semiconductor wafer.

The means for cutting the wafer is generally a cutting method in which a thin disk-shaped blade that rotates at a high speed is cut into a wafer. This cutting method has the advantage of obtaining a flat and sharp cut surface, etc., but the width of the dividing line between the wafers needs to be equal to or larger than the thickness of the blade to be used (mainly about 10 to 30 μm), so the cutting cost It is highly disadvantageous and is extremely disadvantageous from the viewpoint of increasing the productivity in each wafer as much as possible.

On the other hand, in recent years, a laser method has been used to irradiate a transparent laser beam inside a wafer along a predetermined dividing line to form an altered layer having a reduced physical strength, and then an external force is applied to the wafer, thereby dividing the film. The wafer is cut by a predetermined line to obtain a singulated wafer (refer to Patent Document 1). In the laser method, cut The cost of cutting is very small compared to the cutting method, which is advantageous on the production side.

However, when the wafer is diced into a single wafer, in order to prevent wafer dispersion and to protect the cradle, an adhesive tape called a dicing tape is attached to the wafer in advance. Further, the wafer is cut by a cutting process, and the cutting process is attached to the outer periphery of the dicing tape to adhere the metal frame, whereby the wafer can be easily controlled, and in this state, after the laser light of the laser method is irradiated Apply external force.

[Patent Document 1] Japanese Patent Laid-Open Publication No. Hei 10-305420

Summary of invention

A device for irradiating laser light onto a predetermined dividing line of a wafer attached to a dicing tape, for example, a laser processing apparatus having: a holding mechanism for holding a wafer, and irradiating laser light to the wafer A laser beam irradiation mechanism and a moving mechanism that relatively moves the holding mechanism and the laser beam irradiation mechanism. Holding the wafer on the holding mechanism of the laser processing device, and irradiating the laser beam to the dividing line of the wafer by the laser beam irradiation mechanism, and moving the holding mechanism relative to the laser beam irradiation mechanism, This forms a metamorphic layer inside the wafer.

At this time, when the laser light is irradiated to the edge of the wafer, the laser light is irradiated onto the dicing tape or the holding mechanism slightly outside the edge of the wafer due to the mechanical control error of the moving mechanism. When the laser light hits the cutting tape or the holding mechanism, it generates heat due to the energy of the laser light, and a portion that is irradiated to the laser beam is opened. As described above, when a plurality of holes are formed in the extension line of the dividing line of the dicing tape, the wafer cannot be smoothly conveyed by the external force of the cutting process, and there is a fear that the cutting is poor. Especially LED chips such as sapphire wafers In a device of a small semiconductor size of a discrete semiconductor of a semiconductor device of a single function, the hole is in the shape of a small pinhole. When an external force is applied, the holes are connected, and the dicing tape may be cut at the position of the hole and cannot be cut.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a laser processing method for a laser which can perform laser processing by preventing laser light from being irradiated to the outside of the wafer and the dicing tape or the holding mechanism is not affected by the laser light.

In the laser processing method of the present invention, the plate-shaped workpiece is held by the holding mechanism and the one surface of the plate-shaped workpiece is exposed, and the laser beam irradiation mechanism disposed opposite the holding mechanism is opposed to the holding mechanism. When the laser beam is irradiated in parallel along the line to be divided which is formed on the workpiece, the laser beam having the same shape and substantially the same size as the object to be processed is irradiated in parallel. The shielding member is disposed around the workpiece in a state of surrounding the workpiece.

According to the present invention, when the workpiece is held by the holding mechanism, the laser beam blocking member having the opening shape which is substantially the same shape as the workpiece and which is substantially the same size is disposed so as to surround the workpiece. Since the laser light shielding member blocks the laser light, the area covered by the laser light shielding member of the cutting tape or the holding mechanism does not illuminate the laser beam. Thereby, even if the laser light is irradiated to the outer side of the edge of the workpiece due to the mechanical control error of the moving mechanism, the dicing tape or the holding mechanism is not affected by the laser light and does not open. As a result, when the cutting process is performed by irradiating the laser beam with the dicing tape, the external force can be reliably transmitted to the workpiece, and the occurrence of the cutting failure can be suppressed.

Further, in the present invention, the distance between the inner edge portion of the opening portion of the laser light-shielding member and the outer edge portion of the workpiece is preferably set to be within 0.1 mm. By setting the gap to a fineness of 0.1 mm, the influence of the irradiation of the laser beam on the dicing tape or the holding mechanism can be suppressed. Thereby, the laser light can be irradiated onto the workpiece without considering the influence of the laser light on the dicing tape or the holding mechanism.

Further, the laser light-shielding member of the present invention may be exemplified in such a manner that the inner edge portion of the opening portion of the laser light-shielding member is formed away from the outer edge portion of the workpiece and has a height exceeding the thickness of the workpiece. The outer edge portion and the crotch portion extending inward from the upper end of the outer edge portion. The length extending toward the inner side of the crotch portion may also be such as to cover the outer edge of the workpiece or the length of the outer edge of the workpiece, and in such a case, it is possible to surely prevent the outer edge of the workpiece from being processed. At the stage of lateral removal, the laser light strikes the laser light shielding member or is irradiated to the cutting tape or the holding mechanism. Further, even if the outer edge of the workpiece is outside, as long as it is a distance of 0.1 mm from the outer edge as described above, it is not affected by the laser light. Thus, by forming the laser light-shielding member into a meander shape, it is ensured that there is a sufficient distance between the processed and the outer edge portion, so that the workpiece can be prevented from coming into contact with the laser light-shielding member. As a result, the laser light-shielding member can be easily disposed around the workpiece, and the contact between the workpiece and the laser light-shielding member can be suppressed to cause damage to the workpiece.

According to the present invention, by arranging the laser light shielding member In the state of the workpiece, the laser beam can be prevented from being irradiated to the dicing tape or the holding mechanism outside the workpiece, so that the external force can be reliably transmitted to the external force in the cutting program, and the effect of suppressing the occurrence of the cutting failure can be achieved.

Detailed description of the preferred embodiment

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[1]Semiconductor wafer

Reference numeral 1 of Fig. 1 shows a disk-shaped semiconductor wafer which is irradiated with light by a laser processing method according to an embodiment of the present invention. The surface of the wafer 1 is formed into a plurality of rectangular semiconductor wafers (devices) 3 by a lattice-shaped dividing line 2, and an electronic circuit (not shown) such as an IC or an LSI is formed on the surface of the semiconductor wafer 3. A predetermined portion of the peripheral surface of the wafer 1 forms a V-shaped slit (notch) 4 which shows the crystal orientation of the semiconductor.

The wafer 1 is irradiated with laser light internally along the dividing line 2 by a laser processing method according to an embodiment of the present invention to form a modified layer, and the modified layer is cut to form individual semiconductor wafers 3 of a single piece. The laser processing of one embodiment is suitably carried out using the laser processing apparatus shown in Fig. 2.

[2] Using a laser processing device to form a metamorphic layer

The wafer 1 is formed such that the surface side on which the semiconductor wafer 3 is formed is attached to the dicing tape 62 to which the dicing frame 61 is attached as shown in FIG. 3, and is shielded by the laser light around the wafer 1. The member 70 is held in a chuck stage (not shown) having the level of the laser processing apparatus 10. The wafer 1 and the laser light shielding member 70 (hereinafter, abbreviated as a light shielding member) are attached to the dicing tape 62 in connection with the present invention, and will be described in detail later.

Above the chuck table is provided a laser head 21 in which the laser beam is vertically directed downward. The chuck table is disposed on the XY moving table 13, and the XY moving table 13 is disposed on the base 12 of the laser processing apparatus 10 and is freely movable in the horizontal X-axis direction and the Y-axis direction, by the XY moving table 13 The X-axis direction or the Y-axis direction is moved, and the laser beam is irradiated by the laser head 21 to the division planned line 2.

The XY moving stage 13 is composed of an X-axis base portion 30 that is provided on the base 12 and that is free to move in the X-axis direction, and a Y-axis base portion 40 that is provided on the X-axis base portion 30 and that is movable in the Y-axis direction. The X-axis base portion 30 is movably attached to one of the pair of parallel guide rails 31 extending in the X-axis direction fixed to the base 12, and the X-axis drive mechanism 34 that the ball screw 33 is actuated by the motor 32 is moved in the X-axis direction. On the other hand, the Y-axis base portion 40 is slidably attached to a pair of parallel guide rails 41 extending in the Y-axis direction fixed to the X-axis base portion 30, and the Y-axis drive mechanism 44 for actuating the ball screw 43 by the motor 42 is directed Move in the Y-axis direction.

The chuck table is a vacuum chuck that is generally known to hold the workpiece (in this case, the wafer 1) by vacuum action, and is rotatably supported by the Y-axis base 40. The rotary drive mechanism rotates in one or two directions. Then, the chuck table moves in the X-axis direction or the Y-axis direction in accordance with the movement of the X-axis base portion 30 and the Y-axis base portion 40.

By rotating the chuck table, the respective divided planned lines 2 extending in one direction are parallel to the X-axis direction, and the respective divided planned lines 2 extending in the other direction orthogonal thereto are parallel to the Y-axis direction, in the state The wafer 1 held on the chuck table can be fixed by the chuck stop.

Then, the state is maintained such that the X-axis base 30 and the Y-axis of the XY moving table 13 The base 40 is appropriately moved, and the laser beam irradiated by the laser head 21 is irradiated from the surface side to the inside of the wafer 1 along the dividing line 2 . In the present embodiment, the focus position of the laser beam is set inside the wafer 1, and the altered layer is formed at the focus position.

The laser head 21 is disposed at a front end of the casing 22 extending in the Y-axis direction toward the chuck table. The casing 22 is vertically movably disposed in a vertical direction (Z-axis direction) on a column 14 that is erected on the upper surface of the base 11 and is housed in the column 14 and is not shown in the upper and lower driving mechanisms. Can move up and down.

The YAG laser oscillator or the YVO4 laser oscillator constitutes a pulsed laser oscillator connected to the laser head 21, and the laser emitted by the laser oscillator is vertically downwardly directed from the laser head 21 Laser light. The laser emitted from the laser oscillator has good permeability to the inside of the wafer and reliably forms a metamorphic layer, which is a type that is easier to cut. For example, the output is 1 to 5 W, and the wavelength can be determined by the light transmittance of the workpiece. Selected.

The irradiation position of the laser beam from the laser head 21 is controlled based on the photographing of the microscope 24 mounted to one side of the casing 22 via the arm 23. The microscope 24 moves up and down with the housing 22, and moves up and down simultaneously with the laser head 21 to adjust the focus. The wafer 1 held on the chuck table is moved below the microscope 24 before the laser light is irradiated, and the pattern image of the surface is taken by the microscope 24. Then, the image of the image on the surface of the wafer is input to an image processing mechanism (not shown), and the image processing unit detects the planned dividing line 2 to be cut. Further, the movement of the chuck table and the XY moving table 13 or the operation of the laser beam irradiation from the laser head 21 is controlled based on the data of the dividing line 2 detected by the image processing unit. Furthermore, if you use infrared display As the microscope 24, the micromirror can also hold the inner side of the wafer 1 on the chuck table, and in this state, the microscopic image is transmitted from the inside of the wafer 1 through the pattern image of the inner photographing surface to identify the dividing line 2 . Thereby, the laser light can also be irradiated from the inner side of the wafer 1.

In the laser processing apparatus 10 described above, the X-axis base portion 30 is moved in the X-axis direction, and the laser beam is irradiated with the laser beam on the division planned line 2, thereby being divided in parallel with the X-axis direction. Line 2 forms a metamorphic layer inside the wafer. Further, by moving the Y-axis base portion 40 in the Y-axis direction, and the laser beam is irradiated with the laser beam on the division planned line 2, the predetermined line 2 parallel to the Y-axis direction is formed inside the wafer. A metamorphic layer is formed. When irradiating the laser beam, in order to focus the focus position and the inside of the wafer to form a metamorphic layer, the housing 22 is moved up and down, the upper and lower positions of the laser head 21 are adjusted, and the focus position of the laser light is set to the inside of the wafer. height.

As described above, the laser beam is irradiated along all of the planned dividing lines 2 parallel to the X-axis direction and the Y-axis direction, and a deteriorated layer is formed inside the wafer. The wafer 1 after the formation of the altered layer passes through the dicing tape 62 and the dicing frame 61, and is provided to a force applying device such as a cutting device, and the external dividing force is applied to the dicing tape 62, and the dividing line 2 is cut. The individual semiconductor wafers 3 are formed into pieces.

[3] The wafer and the light shielding member are attached to the dicing tape

Before being held in the laser processing apparatus 10, the wafer 1 is as shown in Fig. 3, and the inner side is attached to the dicing tape 62 to which the cutting frame 61 is attached. Next, around the wafer 1, an annular light-shielding member 70 having a circular shape and a substantially large-sized opening portion 71 which is substantially the same shape as the wafer 1 is attached to the periphery around the wafer 1 in a state of being cut. Belt 62. The wafer 1 and the light shielding member 70 are attached to the cut When the tape 62 is cut, as shown in FIG. 5, the distance between the inner edge portion 72 of the opening portion 71 of the light shielding member 70 and the gap W2 between the outer edge portion 1a of the wafer 1 is set to be within 0.1 mm. To achieve this setting, the inner diameter of the light shielding member 70 is set to be within 0.2 mm of the outer diameter of the wafer 1, and when the light shielding member 70 is attached to the dicing tape 62, the gap W2 is ensured within the light shielding member 70. The edge portion 72 and the outer edge portion 1a of the wafer 1 may be included in the entire circumference. As such, the wafer 1 is attached to the dicing tape 62 and held on a horizontal cradle having the laser processing apparatus 10. Moreover, the width of the light shielding member 70 in the radial direction is about 3 to 5 mm. Moreover, the thickness of the light shielding member 70 is about 1 to 3 mm. The light shielding member 70 is required to cover the laser beam L, and does not melt even if the heat of the laser beam L is absorbed to some extent. From this point of view, the material of the light shielding member 70 is suitably made of aluminum or stainless steel. Further, when the light shielding member 70 is irradiated with the laser beam L, it is preferable to perform rough surface processing on the surface to diffuse the irradiated laser beam.

According to the present embodiment, since the light shielding member 70 is disposed in a state surrounding the periphery of the wafer 1, the laser beam L is not irradiated onto the dicing tape 62 or the field covered by the light shielding member 70 of the chuck table. Conventionally, due to mechanical control errors of the X-axis drive mechanism 34 or the Y-axis drive mechanism 44, the laser beam L is slightly irradiated to the outside of the outer edge portion 1a of the wafer 1, as shown in Fig. 4, for cutting. The belt 62 forms a hole 63. However, in the present embodiment, as shown in Fig. 5, even if the laser beam L is slightly irradiated to the outside of the outer edge portion 1a of the wafer 1, the light blocking member 70 blocks the laser beam L and cuts thereunder. The strap 62 or the chuck table will not be affected and will not open the slit 62. As a result, when the cutting process is performed after the laser beam L is irradiated by the dicing tape 62, the external force can be reliably transmitted to the wafer 1, and the occurrence of the cutting failure can be suppressed.

Further, in the present embodiment, it is difficult to adhere the dicing tape 62 to the dicing tape 62 without a gap between the wafer 1 and the light shielding member 70. Therefore, a gap W2 is generated between the outer edge portion 1a of the wafer 1 and the inner edge portion 72 of the light shielding member 70, and the laser beam L is irradiated between the dicing tape 62 of the gap W2. However, by setting the distance of the gap W2 within 0.1 mm, the influence of the gap W2 on the dicing tape 62 or the chuck table can be suppressed. Conventionally, as shown in FIG. 4, the outer edge portion 1a of the wafer 1 is opened at an outer side (distance W1) of about 0.1 mm. Therefore, if the distance from the outer edge portion 1a of the wafer 1 is within 0.1 mm, the dicing tape 62 is not affected by the laser light L.

[4] Other embodiments

The cross-sectional shape of the light-shielding member 70 of the above embodiment is a simple rectangular shape. However, even if it is a dome shape as shown in Fig. 6, the same effects as those of the above-described embodiment can be obtained. Hereinafter, the dome-shaped light shielding member 73 will be described.

The inner edge portion 75 of the opening portion 74 of the light shielding member 73 shown in FIG. 6 is formed with a side edge portion 76 away from the outer edge portion 1a of the wafer 1 and having a height exceeding the thickness of the wafer 1, and A crotch portion 77 extending inward from the upper end of the outer edge portion 76.

The length of the light shielding member 73 that is projected to the inside of the crotch portion 77 has three forms: the length of the outer edge portion 1a of the cover wafer 1 as shown in Fig. 6(a), as shown in Fig. 6(b) The length of the outer edge portion 1a of the wafer 1 or the length of the gap W4 is formed between the front end portion 77a of the crotch portion 77 and the outer edge portion 1a of the wafer 1 as shown in Fig. 6(c). In the case of the sixth graph (a), the length W3 of the outer edge portion 1a of the cover wafer 1 is set to 0.5 mm or less, and the wafer 1 can be singulated into a wafer-deteriorating layer in the cutting process. Form the field. Also, if it is the 6th (c) diagram In other cases, the gap W4 is set to a distance of 0.1 mm or less as in the above embodiment.

As shown in the sixth (a) and (b), when the crotch portion 77 of the light shielding member 73 covers the length of the outer edge portion 1a of the wafer 1 or the length of the outer edge portion 1a of the wafer 1, It is prevented that the laser beam L is irradiated to the light shielding member 73 at the stage where the outer edge portion 1a of the wafer 1 appears outward, and is irradiated to the dicing tape 62 or the chuck table. Further, as shown in Fig. 6(c), even if there is a gap W4 between the front end surface 77a of the dam portion 77 and the outer edge 1a of the wafer 1, if the distance is within 0.1 mm as in the above embodiment, it will not be It is affected by the laser light L. Moreover, since the light shielding member 73 is formed in a meander shape, a sufficient distance can be secured between the wafer 1 and the outer edge portion 76, so that the wafer 1 can be prevented from contacting the light shielding member 73. As a result, the light shielding member 73 can be easily disposed around the wafer 1, and the contact between the wafer 1 and the light shielding member 73 can be suppressed to cause breakage of the wafer 1.

In the above embodiment, one wafer is attached to one dicing tape. However, in the case of a small wafer such as a sapphire wafer, a plurality of dicing tapes 62 having the same size as in the above embodiment may be attached to the dicing tape 62. Laser processing. At this time, as shown in FIG. 7, the light shielding member has a plurality of openings 79 (four in the figure), and a wafer is disposed inside the opening portion 79. In the figure, the cross-sectional shape of the opening portion 79 shows a rectangular light blocking member 78.

When such a small number of wafers are attached to the dicing tape 62, the dividing lines that are orthogonal to each other and extend in the two directions are arranged to extend in the X and Y directions, respectively. Thereby, the laser light can be irradiated to the plurality of wafers at a time, or the respective wafers can be irradiated in the X and Y directions. Therefore, the irradiation operation of the laser light can be performed efficiently. Then, the light shielding member 78 is attached to the dicing tape 62. at this time, Similarly to the above embodiment, the distance between the outer edge portion of the wafer and the inner edge portion 80 of the opening portion 79 is set to 0.1 mm or less. After the wafer and the light shielding member 78 are attached to the dicing tape, they are held by the chuck table of the laser processing apparatus 10, and the laser beam is irradiated onto the dividing line of the wafer.

1‧‧‧Semiconductor wafer

1a‧‧‧Outside

2‧‧‧ dividing line

3‧‧‧Semiconductor wafer

4‧‧‧ incision

10‧‧‧ Laser processing equipment

12‧‧‧Abutment

13‧‧‧XY mobile station

14‧‧‧Cylinder

21‧‧‧Ray head

22‧‧‧ housing

23‧‧‧ Arm

24‧‧‧Microscope

30‧‧‧X-axis base

31, 41‧‧‧ rails

32, 42‧‧‧ motor

33,43‧‧‧Rolling screw

34,44‧‧‧X-axis drive mechanism

40‧‧‧Y-axis base

61‧‧‧ cutting frame

62‧‧‧Cut tape

63‧‧‧ hole

70, 73, 78‧‧ ‧ laser light shading members

71,74,79‧‧‧ openings

72, 75, 80‧‧ ‧ rim

76‧‧‧Outside edge

77‧‧‧檐

77a‧‧‧ front face

L‧‧‧Laser light

W1‧‧‧ distance

W2, W4‧‧‧ gap

W3‧‧‧ length

1 is a perspective view of a semiconductor wafer singulated into a plurality of semiconductor wafers by an embodiment of the present invention.

Fig. 2 is a perspective view of the entire laser processing apparatus suitable for the method of one embodiment of the present invention.

Fig. 3 is a perspective view showing a state in which a wafer and a light shielding member are attached to a dicing tape.

Fig. 4 is a cross-sectional view showing a state in which a laser beam is irradiated onto a wafer by a conventional method.

Fig. 5 is a cross-sectional view showing a state in which a laser beam is irradiated onto a wafer by an embodiment.

6(a) to 6(c) are cross-sectional views showing a state in which laser light is irradiated onto a wafer in another embodiment.

Fig. 7 is a perspective view showing a dicing tape and a light blocking member used in another embodiment.

1‧‧‧Semiconductor wafer

1a‧‧‧Outside

21‧‧‧Ray head

62‧‧‧Cut tape

70‧‧‧Laser light shading member

71‧‧‧ openings

72‧‧‧Inner rim

L‧‧‧Laser light

W2‧‧‧ gap

Claims (2)

A laser processing method is characterized in that a plate-shaped workpiece is held by a holding mechanism and one of the surface of the plate-shaped workpiece is exposed, and a laser beam irradiation mechanism that is disposed opposite the holding mechanism is held The mechanism is relatively parallel to move, and the laser beam is irradiated from the laser beam irradiation mechanism along the line to be divided which is formed on the workpiece, and the laser beam blocking member having the opening is disposed around the workpiece. In a state of surrounding the workpiece, the opening portion has substantially the same shape and the same size as the workpiece, and is formed at an inner edge portion thereof from the outer edge portion of the workpiece and has more than the workpiece The outer edge portion of the height and the crotch portion extending inward from the upper end of the outer edge portion. The laser processing method according to claim 1, wherein the distance between the inner edge portion of the opening portion of the laser light shielding member and the outer edge portion of the workpiece is set to 0.1 mm. Within.