JP2013211364A - Accommodation method for wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a wafer from cracking when the wafer having a modified layer formed inside along division predetermination lines is accommodated in a cassette and conveyed.SOLUTION: When a wafer which has a modified layer 8 formed along crossing division predetermined lines L is accommodated in a cassette 9 having at least an opening portion 90 allowing the wafer to be put in and out, a pair of side walls 91 provided to both side portions of the opening portion 90, and support shelves 92 formed facing inner surfaces of the pair of the side walls 91 and provided from the opening portion 90 to a back portion 95, the wafer W is accommodated so that directions of the division predetermination lines L cross the support shelves 92, and the weight of the wafer W does not concentrate on the division predetermination lines L, thereby preventing the wafer W from cracking during conveyance of the cassette 9, etc.

Description

  The present invention relates to a method for accommodating a wafer having a modified layer formed therein by irradiation with laser light in a cassette.

  A plurality of wafers formed by dividing devices such as ICs, LSIs, and LEDs by dividing lines are cut along the dividing lines and divided into individual devices, which are used for various electronic devices.

  As a method for dividing a wafer into individual devices, a modified layer is formed by irradiating a condensing point of a laser beam having a wavelength that is transmissive to the wafer along the inside of the line to be divided. A technique of dividing an individual device by applying an external force to the quality layer has been proposed and put into practical use (see, for example, Patent Document 1). At the time of laser beam irradiation, a device formed on the front surface side of the wafer gets in the way, so the laser beam is irradiated from the back surface side of the wafer.

Japanese Patent No. 3408805

  However, the wafer in which the modified layer is formed inside the planned dividing line is in a state of being easily broken along the planned dividing line, so when storing the wafer in the cassette, the cassette storing the wafer, There is a problem that the wafer may break when it is transported to the dividing process for dividing the wafer into devices and the grinding process for grinding the back surface of the wafer.

  The present invention has been considered in view of such a problem, and when a wafer having a modified layer formed therein is accommodated in a cassette and transported along a division line, the wafer is prevented from cracking. Let it be an issue.

  The present invention relates to a wafer accommodation method for accommodating a wafer in which a device is formed in a region defined by a plurality of intersecting division lines, in a cassette, and divides a laser beam having a wavelength having transparency to the wafer. Provided on both sides of the opening, a modified layer forming process for locating and irradiating the condensing point inside the planned line, forming a modified layer along the planned dividing line, an opening allowing wafers to be taken in and out A reformed layer is formed along the planned dividing line in a cassette including at least a pair of side walls and a support shelf formed to face the inner surface of the pair of side walls and provided from the opening to the back. A wafer storing step, wherein the wafer is stored such that the direction of the division line intersects the support shelf.

  In the accommodating step, it is desirable to accommodate the wafer so that the direction of the division line formed on the wafer intersects the support shelf at an angle of 45 degrees.

  In the present invention, in the accommodating step of accommodating a wafer in which a modified layer is formed along a plurality of intersecting division lines, the wafer is arranged such that the direction of the division line intersects the direction in which the support shelf extends. Since the weight of the wafer is prevented from being concentrated on the division planned line, the wafer can be prevented from being broken during the transfer of the cassette. In particular, when the wafer is accommodated in the cassette so that the direction of the planned dividing line intersects with the support shelf at an angle of 45 degrees, the bending moment due to the weight of the wafer is minimized with respect to the intersecting scheduled line, and more reliably. Wafer cracking can be prevented.

It is a disassembled perspective view which shows a wafer and a protective tape. It is a perspective view which shows the state by which the protective tape was stuck on the surface of the wafer. It is a perspective view which shows an example of a laser processing apparatus. It is sectional drawing which shows the state which forms a modified layer in the inside of a wafer. It is a perspective view which shows the state which forms a modified layer in the inside of a wafer. It is a perspective view which shows the wafer in which the modified layer was formed in the inside of a wafer. It is a perspective view which shows the state which accommodates a wafer in a cassette. It is a top view which shows the state which accommodates a wafer in a cassette. It is a perspective view which shows the state which grinds the back surface of a wafer. It is a perspective view which shows the state which affixes the back surface of a wafer on an expansion tape, and peels off a protective tape from the back surface of a wafer. It is sectional drawing which shows the state which divides | segments a wafer.

  On the surface W1 of the wafer W shown in FIG. 1, a plurality of intersecting division lines L are formed, and a device D is formed in a region partitioned by the division lines L. Hereinafter, a method of dividing the wafer W into individual devices D along the division line L and accommodating the divided wafer W in a cassette will be described.

(1) Modified layer forming step A protective tape T1 is attached to the surface W1 of the wafer W shown in FIG. 1, and the device D formed on the surface W1 is protected by the protective tape T1 as shown in FIG. The back surface W2 is exposed. FIG. 2 shows a state in which the protective tape T1 is attached to the front surface W1 of the wafer W and turned upside down. In this manner, a modified layer is formed inside the planned division line L of the wafer W having the protective tape T1 adhered to the surface W1, for example, using the laser processing apparatus 1 shown in FIG.

  The laser processing apparatus 1 includes a holding unit 2 that holds a wafer and a processing unit 3 that irradiates the wafer with a laser beam.

  The holding unit 2 is supported by the holding unit X-direction feeding unit 4 so as to be movable in the X-axis direction, and is supported by the holding unit Y-direction feeding unit 5 so as to be movable in the Y-axis direction. On the other hand, the processing unit 3 is supported by the processing unit Y-direction feeding unit 6 so as to be movable in the Y-axis direction, and is supported by the processing unit Z-direction feeding unit 7 so as to be movable in the Z-axis direction.

  The holding means X-direction feed section 4 includes a ball screw 40 having an axis in the X-axis direction, a pair of guide rails 41 arranged in parallel to the ball screw 40, a motor 42 connected to one end of the ball screw 40, a ball screw The slide portion 43 includes a slide portion 43 that has a nut that is screwed into the guide rail 40 and that has a lower portion that is in sliding contact with the guide rail 41. The slide portion 43 is driven by the motor 42 to rotate the ball screw 40. It is configured to slide in the X-axis direction on the top.

  The slide unit 43 is provided with a holding unit Y-direction feeding unit 5 that moves the holding unit 2 in the Y-axis direction. The holding means Y-direction feeding unit 5 includes a ball screw 50 having an axis in the Y-axis direction, a pair of guide rails 51 arranged in parallel to the ball screw 50, a pulse motor 52 connected to one end of the ball screw 50, The moving base 53 includes a moving base 53 having a nut screwed into the ball screw 50 and having a lower portion slidably contacting the guide rail 51. The moving base 53 is driven by the pulse motor 52 to rotate the ball screw 50. Is configured to slide on the guide rail 51 in the Y-axis direction. The moving base 53 is provided with a rotation driving unit 54 that has a pulse motor therein and rotates the holding means 2.

  The processing means Y-direction feeding section 6 includes a ball screw 60 having an axis in the Y-axis direction, a pair of guide rails 61 arranged in parallel to the ball screw 60, a pulse motor 62 connected to one end of the ball screw 60, A slide part 63 having a nut that engages with the ball screw 60 and having a lower part slidably contacting the guide rail 61 is driven. The slide part 63 is guided by the pulse motor 62 as the ball screw 60 rotates. The rail 61 is slid in the Y-axis direction, and the processing means 3 is also moved in the Y-axis direction along with this.

  The processing means Z-direction feeding unit 7 includes a ball screw 70 having an axis in the Z-axis direction, a pair of guide rails 71 disposed in parallel to the ball screw 70, a pulse motor 72 connected to one end of the ball screw 70, It has a nut that engages with the ball screw 70 inside, and a side portion that is in sliding contact with the guide rail 71 to support the processing means 3. The ball screw 70 is driven by the pulse motor 72 to rotate. Accordingly, the elevating part 73 is guided by the guide rail 71 and moves up and down in the Z-axis direction, and the processing means 3 is also moved up and down in the Z-axis direction accordingly.

  The processing means 3 includes a laser light irradiation head 30 that irradiates laser light downward, and the laser light irradiation head 30 is fixed to the distal end portion of the housing 31. Further, on the side of the housing 31, detection means 32 for detecting the position where the wafer should be imaged and irradiated with laser light is disposed. The detection unit 32 includes, for example, an infrared camera 32a.

  In the laser processing apparatus 1, the wafer W having the protective tape T <b> 1 attached to the front surface W <b> 1 exposes the back surface W <b> 2 side upward, and the protective tape T <b> 1 side is sucked and held by the holding means 2.

  The holding means 2 holding the wafer W is driven by the holding means X-direction feeding unit 4 shown in FIG. 1 and moves in the X-axis direction, and the wafer W is positioned immediately below the detection means 32. Then, the division line L formed on the surface W1 is detected by processing such as imaging and pattern matching by the infrared camera 32a, and the position of the laser light irradiation head 30 and the detected division line L in the Y-axis direction is detected. Matching is done.

  When the laser beam irradiation head 30 and the scheduled division line L are aligned, the laser is applied to the detected scheduled division line L while the holding means 2 is moved in the X-axis direction by the holding means X-direction feeding unit 4. Laser light 30 a is irradiated from the light irradiation head 30. At this time, as shown in FIG. 4, if irradiation is performed so that the condensing point of the laser beam 30 a is located inside the wafer W, the wafer W enters the inside of the wafer W along a division line L parallel to the X-axis direction. The modified layer 8 is formed. The modified layer refers to a layer in which any of density, refractive index, mechanical strength, and other physical characteristics is different from the surrounding area.

As shown in FIG. 5, after the laser beam irradiation performed in this way is performed for all the division lines L in the same direction while the processing unit 3 is sent in the Y-axis direction, the holding unit 2 is rotated by 90 degrees. Then, when the laser beam is irradiated in the same manner, the modified layer 8 is formed along all the division lines L as shown in FIG. In addition, the processing conditions at the time of laser beam irradiation are as follows, for example.
Wavelength: 1300 [nm]
Average output: 1 [W]
Repetition frequency: 90 [kHz]
Pulse width: 10 [ps]
Spot diameter: 1 [μm]

(2) Housing Process The wafer W on which the modified layer 8 is formed is housed in the cassette 9 shown in FIG. The cassette 9 is formed so as to face an opening 90 serving as an entrance / exit allowing the wafer W to be taken in and out, a pair of side walls 91 erected on both sides of the opening 90, and an inner surface of the pair of side walls 91. A support shelf 92 extending from the opening 90 to the back portion 95 of the cassette 9, a top plate 93 installed between the upper portions of the pair of side walls 91, and a gripping portion 94 provided on the top surface of the top plate 93. Yes.

  The support shelf 92 is configured by a plurality of grooves 92a that are formed in a concave shape by cutting out the inner surface of the side wall 91 in the horizontal direction, and the outer periphery of the wafer W can be supported in each groove 92a.

  The wafer W is inserted into each groove 92a from the opening 90. As shown in FIG. 7, the wafers W are accommodated in the cassette 9 so that the division line L intersects with the direction A as the insertion direction, that is, the direction in which the support shelf 92 extends from the opening 90 to the back 95.

  When the wafer W is accommodated in the cassette 9, for example, the wafer W is held by the holding member 95 shown in FIG. The holding member 95 is formed by two fingers 950 and a base portion 951 connecting them, and a suction portion 952 for sucking the wafer W is provided on the upper surfaces of the two fingers 950 and the base portion 951.

  With the wafer W supported from below by the holding member 95 and sucked by the suction portion 952, the holding member 95 enters the inside through the opening 90 of the cassette 9, releases the suction by the suction portion 952, and moves the holding member 95 to the When lowered, the outer periphery of the wafer W is supported by the support shelf 92. The wafer W accommodated in the support shelf 92 is supported by its own weight along the longitudinal direction of the support shelf 92, and the bending moment acts in a direction perpendicular to the support shelf 92.

となり、９０度の角度で交差する分割予定ラインＬに対して曲げモーメントを最小にすることができるため、より確実にウェーハＷの割れを防止することができる。このようにしてウェーハＷがカセット９に収容されると、カセット９は、後の研削工程や分割工程に搬送される際に、ウェーハＷが割れるのを防ぐことができる。 Here, since the modified layer 8 formed inside the holding member 95 is formed along the division line L, the direction of the division line L and the longitudinal direction of the support shelf 92 are assumed to be parallel. If there is, the bending moment due to the weight of the wafer W concentrates on the modified layer 8 and the wafer W may be broken along the division line L. However, as shown in FIGS. 7 and 8, since the wafer W is accommodated such that the division line L intersects with the direction in which the support shelf 92 extends, the bending moment due to the weight of the wafer W is divided. The direction in which the support shelf 92 extends, that is, the direction in which the wafer W is supported, and the direction in which the weight is concentrated are shifted from each other, so that the wafer W is not easily broken along the division line L. In particular, as shown in FIG. 8, when the wafer W is accommodated so that the angle θ formed by intersecting the direction of the planned division line L and the direction in which the support shelf 92 extends is 45 degrees, Compared with the case where the wafers are accommodated in parallel, the bending moment acting on the dividing line L is [Equation 1]

Thus, since the bending moment can be minimized with respect to the planned division line L that intersects at an angle of 90 degrees, the wafer W can be more reliably prevented from cracking. When the wafer W is accommodated in the cassette 9 in this way, the cassette 9 can prevent the wafer W from being cracked when being transferred to a subsequent grinding process or division process.

(3) Grinding process In the grinding process, for example, a grinding apparatus 10 shown in FIG. 9 can be used. The grinding apparatus 10 includes a chuck table 100 that can hold and rotate a wafer W, and a grinding means 101 that grinds the wafer. The grinding means 101 is configured by attaching a grinding wheel 104 to the lower end of a rotating shaft 102 via a mount 103, and a plurality of grinding wheels 104 a are fixed to the lower surface of the grinding wheel 104.

  The wafer W in which the modified layer 8 is formed is taken out from the cassette 9 shown in FIG. 7, and the protective tape T1 side is sucked and held by the chuck table 100. The chuck table 100 rotates in the direction of arrow B at a rotational speed of, for example, 300 [RPM], the grinding means 101 rotates in the direction of arrow C, for example, at a rotational speed of 6000 [RPM], and the grinding means 101 has a rotational speed of, for example, 1 [μm]. / S], the back surface W2 of the wafer W is ground. And if the wafer W is formed in predetermined thickness, the grinding means 1 will be raised and grinding will be complete | finished. Then, during grinding, the wafer W is divided into individual devices by a division line L on which the modified layer 8 is formed.

(4) Separation Step As shown in FIG. 10, the back surface W2 side of the ground wafer W is adhered to the expansion tape T2. A ring-shaped frame F is attached to the peripheral edge of the expansion tape T2. Further, the protective tape T1 is peeled off from the surface W1 of the wafer W. As a result, the wafer W is supported by the frame F via the expansion tape T2.

  Next, the wafer W is separated along the division line L by using the wafer expanding apparatus 11 shown in FIG. The wafer expanding apparatus 11 includes a holding table 110 that holds a wafer and a frame holding unit 111 that supports the frame F, and the holding table 110 and the frame holding unit 111 can be moved up and down relatively. The frame holding part 111 includes a table part 111a that supports the frame F from below, and a pressing part 111b that presses the frame F placed on the table part 111a from above.

  Of the expansion tape T2, the portion attached to the wafer W is placed on the holding table 110, the portion attached to the frame F is placed on the table portion 111a of the frame holding portion 111, and the frame is formed by the pressing portion 111b. Press F. When the holding table 110 is raised relative to the frame holding unit 111, the expansion tape T2 is stretched in the horizontal direction and the wafer W is also pulled in the same direction, so that the individual devices D are separated. In the case where the grinding process is not performed, in the separation process, the wafer is divided into individual devices along the planned division line on which the modified layer is formed.

1: Laser processing apparatus 2: Holding means 3: Processing means 30: Laser light irradiation head 31: Housing 32: Detection means 4: Holding means X-direction feeding part 40: Ball screw 41: Guide rail 42: Motor 43: Slide part 5: Holding means Y-direction feeding section 50: Ball screw 51: Guide rail 52: Pulse motor 53: Moving base 54: Rotation drive section 6: Processing means Y-direction feeding section 60: Ball screw 61: Guide rail 62: Pulse motor 63: Slide section 7: Processing means Z direction feeding part 70: Ball screw 71: Guide rail 72: Pulse motor 73: Lifting part 8: Modified layer 9: Cassette 90: Opening part 91: Side wall 92: Support shelf 92a: Groove 93: Top plate 94 : Grasping part 95: Holding member 10: Grinding device 100: Chuck table 101: Grinding means 102: Mount 103: Grinding wheel 103a: Grinding wheel 11: Wafer expansion device 110: Holding table 111: Frame holding part 111a: Table part 111b: Holding part W: Wafer W1: Front surface L: Line to be divided D: Device W2: Back surface T1: Protective tape T2 : Expansion tape F: Frame

Claims (2)

A wafer storage method for storing a wafer in which a device is formed in an area defined by a plurality of intersecting division lines in a cassette,
A modified layer forming step of irradiating a laser beam having a wavelength having transparency with respect to the wafer with a focusing point positioned inside the planned division line and forming a modified layer along the planned division line;
An opening for allowing the wafer to be taken in and out, a pair of side walls provided on both sides of the opening, and a support shelf formed to face the inner surface of the pair of side walls and provided from the opening to the back And a housing step for housing a wafer having a modified layer formed along the division line,
Including
In the accommodation step, a wafer accommodation method for accommodating the wafer so that the direction of the division line intersects the support shelf. The wafer accommodation method according to claim 1, wherein, in the accommodation step, the wafer is accommodated such that a direction of a division line formed on the wafer intersects the support shelf at an angle of 45 degrees.

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