CN103367250A - Segmenting method of device wafer - Google Patents

Abstract

The invention provides a method for dividing a device wafer. When a device wafer with a modified layer formed inside is divided into multiple devices starting from the modified layer by expanding the extended sheet, it can reduce the degradation of device quality and reduce the cost to subsequent devices. The process may cause obstacles. A division method, after performing a sticking step of sticking a spread sheet to the back surface (1b) of a device wafer (1), and irradiating a laser beam (L) having a transmittance wavelength along a line to be divided (2) to After the modified layer forming step of forming the modified layer (1c) in the device wafer, there is a division step of dividing the device wafer into individual devices (3) with the expansion sheet (11) starting from the modified layer. The method includes a protective film covering step of covering the surface (1a) of the device wafer with a water-soluble protective film (5) before the dividing step, and a protective film removing step of removing the protective film by cleaning after the dividing step.

Description

Separation method of device wafer

technical field

The present invention relates to a method for dividing a device wafer in which devices are formed in regions divided by a plurality of intersecting dividing lines.

Background technique

For example, semiconductor devices are manufactured through such a process: a plurality of rectangular device regions are divided on the surface of a wafer made of semiconductors such as silicon or gallium arsenide through grid-shaped dividing lines, and devices with IC (Integrated IC) are formed in these device regions. circuit, integrated circuit) or LSI (Large Scale Integration, large-scale integrated circuit) and other electronic circuit devices, then, after performing predetermined processing such as grinding the back of the wafer to thin the wafer to a predetermined thickness, the Wafers are separated into individual devices. Separation of such a device wafer is generally performed by cutting the device wafer with a dicing blade. However, in recent years, a laser processing method has also been adopted in which a modified layer is formed inside the device wafer by irradiating it with a laser beam having a wavelength that is transparent. The device wafer is divided by applying an external force to the device wafer starting from the reformed layer (Patent Document 1, etc.).

prior art literature

Patent Document 1: Japanese Patent Laid-Open No. 2009-277778

Contents of the invention

However, when the device wafer is divided as described above, there are cases where slitting chips are generated from the slicing surface. When the slitting chips adhere to the device, the quality of the device will be reduced, and the following problems will be caused: welding (bonding, combining) in the subsequent process. ) or packaging (packaging) to bring obstacles.

The present invention was made in view of the above, and its main technical task is to provide a method for dividing a device wafer having a modified layer formed therein into a plurality of devices by expanding a stretched sheet. , it is possible to reduce the degradation of device quality and reduce the possibility of causing obstacles to subsequent processes.

The method for dividing a device wafer of the present invention is a method for dividing a device wafer in which devices are formed in each area divided by a plurality of intersecting predetermined dividing lines, and is characterized in that it has: a sticking step, sticking the back surface of the device wafer on an extended sheet; modified layer forming step, before implementing the pasting step or after implementing the pasting step, the device wafer is irradiated with a laser beam of a wavelength that is transmissive relative to the device wafer along the planned division line of the device wafer, and formed on the device wafer the modified layer along the dividing line; and a dividing step, after performing the above-mentioned pasting step and the above-mentioned modified layer forming step, applying an external force to the device wafer by expanding the above-mentioned extended sheet pasted with the device wafer, so that the above-mentioned The modified layer is used as a starting point to divide the device wafer along the above-mentioned predetermined division line, and the above-mentioned method for dividing the device wafer also includes: a protective film covering step, at least before implementing the above-mentioned dividing step, covering the surface of the device wafer with a water-soluble protective film; and In the protective film removal step, the protective film is removed by washing after the above-mentioned dividing step is performed.

In the present invention, the surface of the device wafer is covered with a water-soluble protective film in the protective film covering step before the dividing step, and then the device wafer is divided by the dividing step. Therefore, the division chips generated in the division step are attached to the protective film, and the division chips are removed together with the protective film in the subsequent protective film removal step. Therefore, it is possible to reduce the degradation of device quality and reduce the possibility of causing troubles in subsequent processes.

According to the present invention, there is an effect of providing a division method in which when a device wafer having a modified layer formed therein is divided into a plurality of devices starting from the modified layer by expanding the stretched sheet, it is possible to reduce degradation in device quality and reduce The possibility of bringing obstacles to the subsequent process.

Description of drawings

FIG. 1 is a perspective view showing a pasting step of a division method according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view showing a state where the back surface of the device wafer is bonded to the stretch sheet with a frame in the bonding step.

3 is an overall perspective view showing a laser processing apparatus suitable for carrying out a modified layer forming step of the division method according to one embodiment.

Fig. 4 is a side view showing a state in which the above-mentioned modified layer forming step is performed.

Fig. 5 is a cross-sectional view showing details of the modification layer forming step described above.

6 is a side view showing a state where a protective film covering step of the dividing method according to one embodiment is performed by a film forming apparatus.

7 is a cross-sectional view showing a state where the surface of the device wafer is covered with a protective film in the protective film covering step.

8 is a cross-sectional view showing a dividing step of a dividing method according to an embodiment, (a) showing before dividing the device wafer, and (b) showing after dividing the device wafer.

9 is a side view showing a state in which a protective film removal step of the dividing method according to one embodiment is performed by a film forming apparatus.

FIG. 10 is a cross-sectional view showing a state where the protective film has been removed from the surface of the device by the protective film removing step described above.

Label description

1 device wafer

1a The surface of the device wafer

1b The back side of the device wafer

1c modified layer

2 split reservation line

3 Device (device area)

5 protective film

11 extension piece

L laser beam

Detailed ways

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

(1) Device wafer

Reference numeral 1 in FIGS. 1 and 2 denotes a disc-shaped device wafer that is divided in a dividing method according to an embodiment. The device wafer 1 is based on a semiconductor material (silicon or gallium arsenide, etc.) with a thickness of, for example, about several hundreds of μm, and a plurality of rectangular devices are divided on the surface 1 a of the device wafer 1 by grid-shaped dividing lines 2 . area 3. Furthermore, an electronic circuit composed of IC, LSI, or the like is formed in each device region 3 . In the following description, the device region 3 on which the electronic circuit is formed is simply referred to as the device 3 . The present embodiment is a method of dividing the device wafer 1 along the planned dividing line 2 to obtain individual devices 3, which is performed in the following steps.

First, as shown in FIGS. 1 and 2 , the back surface of the device wafer 1 is bonded to the spreading sheet 11 attached to the ring frame 10 to expose the surface 1 a of the device wafer 1 (sticking step). The expand sheet 11 is a sheet with a resin adhesive layer formed on one side of a base material such as a stretchable synthetic resin sheet such as polyvinyl chloride or polyolefin, and the frame 10 is made of a rigid metal plate such as a stainless steel plate. composed frame. The extension sheet 11 is arranged to cover the space inside the frame 10 , and is attached to one side (single side) of the frame 10 via an adhesive layer. The back surface 1b of the device wafer 1 is stuck to the adhesive layer of the extension sheet 11 so that the device wafer 1 and the frame 10 form a concentric shape. The device wafer 1 is handled through the frame 10 and the spreading sheet 11 at the time of transfer.

Next, after the above-mentioned pasting step, the device wafer 1 is irradiated with a laser beam of a transmissive wavelength along the planned dividing line 2, and a modified layer along the planned dividing line 2 is formed in the device wafer 1 (modified layer formation step). The modified layer forming step can be performed by the laser processing device 20 shown in FIG. 3 , and the laser processing device 20 will be described below.

(2) Laser processing device

The laser processing apparatus 20 has a base 21 on which an XY movable table 22 movable freely in the horizontal X-axis direction and the Y-axis direction is provided. A chuck table 51 for holding the device wafer 1 is provided on the XY moving table 22 . The irradiation part 62 of the laser irradiation member 60 for irradiating the laser beam toward the device wafer 1 held on the chuck table 51 is arranged above the chuck table 51, and the irradiation part 62 is arranged so as to be connected to the chuck table 51. opposite state.

The XY mobile table 22 is composed of a combination of an X-axis base 30 and a Y-axis base 40. The X-axis base 30 can be freely moved in the X-axis direction and is arranged on the base 21. The Y-axis base The base 40 is provided on the X-axis base 30 so as to be able to move freely in the Y-axis direction. The X-axis base 30 is slidably mounted on a pair of parallel guide rails 31, and the X-axis base 30 is moved in the X-axis direction by an X-axis drive mechanism 34 that uses a motor 32 to make a ball screw (ball screw) 33 work. , the pair of parallel guide rails 31 are fixed on the base 21 and extend in the X-axis direction. On the other hand, the Y-axis base 40 is slidably mounted on a pair of parallel guide rails 41, and the Y-axis base 40 is moved in the Y-axis direction by a Y-axis drive mechanism 44 that operates a ball screw 43 with a motor 42. , the pair of parallel guide rails 41 are fixed on the X-axis base 30 and extend in the Y-axis direction.

The cylindrical chuck base 50 is supported on the upper surface of the Y-axis base 40, and can freely rotate around the Z-axis direction (up-down direction), and the chuck table 51 is concentrically fixed to the chuck base. Seat 50. The chuck table 51 is a generally well-known vacuum type chuck table that absorbs and holds the device wafer 1 by vacuum suction. The chuck table 51 is rotationally driven integrally with the chuck base 50 by an unillustrated rotational driving means. A pair of clamps 52 are disposed at positions separated from each other by 180° around the chuck table 51 , and the pair of clamps 52 hold the frame 10 in a detachable manner. The clamp 52 is attached to the chuck base 50 via a stay (see FIG. 4 ) 53 .

In the XY moving table 22 , when the X-axis base 30 moves in the X-axis direction, it is a processing feed for irradiating the laser beam along the dividing line 2 of the device wafer 1 . Then, by moving the Y-axis base 40 in the Y-axis direction, the index feeding of the target dividing line 2 to which the laser beam is irradiated is switched. In addition, the machining feed direction and the index feed direction can also be set oppositely, that is, the Y-axis direction is the machining feed direction, and the X-axis direction is the index feed direction, which is not limited.

The laser irradiation unit 60 has a rectangular parallelepiped housing 61 extending in the Y-axis direction toward the upper side of the chuck table 51 , and the irradiation unit 62 is provided at an end of the housing 61 . The casing 61 is provided on the column 23 so as to be movable up and down in the vertical direction (Z-axis direction). The body 61 moves up and down.

The housing 61 of the laser irradiation member 60 accommodates: a laser oscillation unit for oscillating a laser beam composed of a pulsed laser such as YAG or YVO, an output adjustment unit for adjusting the output of the laser beam, etc. (not shown), The laser beam oscillated by this laser oscillation unit is irradiated downward from the irradiation unit 62 .

An alignment member 70 for detecting the planned dividing line 2 of the device wafer 1 is fixed near the irradiation portion 62 at the end of the housing 61 . The correction means 70 has a camera 71 for photographing the device wafer 1 , and the correction means 70 detects (corrects) the dividing line 2 based on the image obtained with the camera 71 .

(3) Formation of modified layer

The above is the structure of the laser processing apparatus 20, and the reformed layer is formed inside the device wafer 1 by this laser processing apparatus 20 as follows.

Firstly, the device wafer 1 is loaded onto the chuck table 51 of the laser processing device 20 through the extension sheet 11 , and is adsorbed and held on the chuck table 51 by vacuum suction. The device wafer 1 is held on the chuck table 51 with the rear surface 1b exposed. In addition, the frame 10 is held by clamps 52 .

Then, after the position of the planned dividing line 2 is detected by the calibration member 70, as shown in FIGS. The inside of the device wafer 1 is scanned with the laser beam L along the detected planned dividing line 2 .

The laser beam L is a pulsed laser beam having a wavelength that is transparent to the device wafer 1 , and is, for example, a laser beam under the following conditions.

Wavelength: 1064nm pulsed laser

· Repetition frequency: 100kHz

· Average output: 1.5W

As shown in FIG. 5 , the laser beam L during laser processing is incident from the surface 1 a and condensed into the device wafer 1 , thereby forming the reformed layer 1 c along the planned dividing line 2 inside the device wafer 1 . The modified layer 1c is formed with a constant layer thickness at a certain depth from the surface 1a of the device wafer 1 . Modified layer 1 c has a characteristic of lower strength than other parts in device wafer 1 .

By rotating the chuck table 51 to set the planned dividing line 2 parallel to the machining feed, and moving the chuck table 51 in the X-axis direction, the laser processing device 20 moves along the planned dividing line 2 . A scan of the laser beam is performed. Arrow B in FIG. 4 is the movement direction of the chuck table 51 during laser processing, and the irradiation unit 62 is relatively processed in the arrow A direction accordingly. At this time, the machining feed rate is, for example, about 400 mm/s. In addition, the planned division line 2 on which the laser beam is irradiated is switched by index feed that moves the chuck table 51 in the Y-axis direction. As a result, modified layer 1 c is formed along all planned dividing lines 2 in device wafer 1 .

The modified layer forming step for the device wafer 1 is completed by the above, and then the device wafer 1 is carried out from the laser processing device 20, and the surface 1a of the device wafer 1 is covered with a water-soluble protective film (protection layer) by the film forming device 80 shown in FIG. 6 . membrane covering step). Hereinafter, the film forming apparatus 80 will be described.

(4) Film forming device

The film forming apparatus 80 is an apparatus in which a liquid resin is dripped from a resin supply nozzle 83 onto a surface 1 a which is an upper surface of a device wafer 1 on a disc-shaped rotary table 82 held in an apparatus case 81 . P, and implement spin coating.

The device case 81 is composed of a cylindrical case body 811 that opens upward and has a hole 811a formed in the center, and a cover 812 that closes the hole 811a of the case body 811. The drive shaft 85 of the motor 84 penetrates the cover 812 from below. The center of the rotary table 82 is fixed to the upper end of a drive shaft 85 protruding into the device case 81 , and is supported so as to be horizontally rotatable by the drive of a motor 84 .

The device wafer 1 is loaded onto the upper surface of the rotary table 82 through the extension sheet 11 , and is adsorbed and held on the upper surface of the rotary table 82 by vacuum suction. A plurality of centrifugal grippers 86 are attached to the peripheral portion of the rotary table 82, and the frame 10 is held by the centrifugal grippers 86. When the centrifugal force is generated by the rotation of the rotary table 82, the centrifugal grippers 86 are Work by holding down the frame 10 from above.

The resin supply nozzle 83 is rotatably supported on the bottom of the casing main body 811 , and the resin supply port 831 at the end can be positioned directly above the center of the rotary table 82 by turning. In addition, there is a cleaning liquid supply nozzle 87 inside the device case 81. The cleaning liquid nozzle 87 has the same structure as the resin supply nozzle 83 and is rotatable. 871 supplies the cleaning liquid W downward (see FIG. 9 ).

(5) Formation of protective film

In the protective film covering step, the device wafer 1 is held on the rotary table 82 via the stretch sheet 11 , the rotary table 82 is driven to rotate, and the frame 10 is held by the centrifugal clamp 86 . Then, the resin P is dropped from the resin supply port 831 of the resin supply nozzle 83 to the center of the surface 1 a of the device wafer 1 in the spinning state. The resin P dropped onto the surface 1a is spin-coated on the entire surface 1a by centrifugal force, and a protective film 5 made of the resin P as shown in FIG. 7 is formed. In addition, when the protective film covering step is performed, the cleaning liquid supply nozzle 87 retreats to the vicinity of the inner peripheral surface of the housing main body 811 .

As the water-soluble resin P used to form the protective film 5, water-soluble coatings such as polyvinyl alcohol (polyvinylalcohol, PVA), polyethylene glycol (polyethylene glycol, PEG), and polyethylene oxide (polyethylene oxide, PEO) are preferably used. (resist).

After the protective film 5 is formed with a predetermined thickness (for example, about several μm) on the surface 1 a of the device wafer 1 , the protective film covering step is completed, and the device wafer 1 is removed from the film forming apparatus 80 . Then, the stretched sheet 11 is expanded by the expanding device 90 shown in FIG. 8 , an external force is applied to the device wafer 1 , and the device wafer 1 is divided along the predetermined dividing line 2 starting from the modified layer 1 c (dividing step). Hereinafter, a method for dividing the device wafer 1 in the dividing step will be described.

(6) Segmentation of device wafers

The expansion apparatus 90 has a cylindrical loading drum 91 for loading the device wafer 1 . An annular holding table 92 is disposed concentrically with the loading drum 91 around the loading drum 91 , and a plurality of movable clamps 93 for pressing the holding frame 10 from above are provided on the holding table 92 . In addition, the holding table 92 is supported by a plurality of air cylinders 94 so as to be able to move up and down.

As shown in (a) of FIG. 8 , in the dividing step, the device wafer 1 is loaded onto the loading drum 91 of the expansion device 90 via the stretch sheet 11, and the frame 10 is loaded onto the raised holding table 92, and The holding frame 10 is pressed from above by the movable clamp 93 . In this set state, the stretch sheet 11 and the device wafer 1 are horizontal, and then, as shown in FIG. 8( b ), the holding table 92 is lowered by the air cylinder 94 . Then, the stretched sheet 11 on the holding table 92 expands in the radial direction, and the device wafer 1 attached to the stretched sheet 11 is cut from the modified layer 1c formed in the device wafer 1 as a starting point. In this way, the device wafer 1 is divided into a plurality of chip-shaped devices 3 .

(7) Removal of protective film

After the device wafer 1 is divided into individual devices 3 , the dividing step is completed, and then, the protective film 5 is cleaned and removed by the above-mentioned film forming apparatus 80 (protective film removal step).

In the protective film removal step, as shown in FIG. 9 , the device wafer 1 in which a plurality of divided devices 3 are attached to the spreading sheet 11 is set again in the film forming apparatus 80, and a cleaning solution is supplied to the surface of the device wafer 1. W.

When supplying the cleaning liquid W, the resin supply nozzle 83 is retracted to the vicinity of the inner peripheral surface of the housing body 811 , and the cleaning liquid supply nozzle 87 is rotated to position the cleaning liquid supply port 871 directly above the center of the rotary table 82 . Then, the rotary table 82 is rotated while the cleaning liquid W is discharged from the cleaning liquid supply port 871 . The cleaning liquid W is supplied to the center of the device wafer 1 in a spinning state, and is spread over the entire surface of the device wafer 1 by centrifugal force, and the water-soluble protective film 5 is melted and removed by the cleaning liquid W. Alternatively, the cleaning liquid W may be supplied while reciprocating the cleaning liquid supply nozzle 87. In this case, the cleaning liquid W is directly supplied to the entire surface of the device wafer 1, so the protective film 5 can be efficiently removed. Thereby, the protective film 5 covering the surface of each device 3 is removed as shown in FIG. 10 .

After the protective film 5 is removed from the surface of each device 3, the protective film removal step is ended. Thereafter, the process proceeds to a pickup step of peeling and picking up the devices 3 one by one from the stretch sheet 11 .

The above is the dividing method of the present embodiment. According to the present embodiment, the surface 1a of the device wafer 1 is covered with a water-soluble protective film 5 in the protective film covering step before the dividing step, and then the device wafer 1 is divided in the dividing step. for multiple devices 3 . There are cases where slits are generated from the fractured surfaces of the segregated devices 3 in the slicing step, and the slits adhere to the surface 1a of the device wafer 1 due to movement of the device wafer 1 or generation of static electricity in the absence of the protective film 5 . However, as described in this embodiment, when the surface 1 a of the device wafer 1 is covered with the protective film 5 , dicing chips adhere to the protective film 5 . Then, the protective film 5 is removed by the protective film removing step, whereby the division chips adhering to the protective film 5 are removed together with the protective film 5 . Therefore, it is possible to reduce the problem that the quality of the picked-up device 3 is affected by the shavings, and to reduce the possibility of impairing the subsequent process.

In addition, in the above-mentioned embodiment, each step of the present invention is performed in the order of the sticking step, the modified layer forming step, the protective film covering step, the dividing step, and the protective film removing step, but in the present invention, the sticking step and the modified The order of the permanent layer forming step is arbitrary, and the sticking step may be performed after the modifying layer forming step contrary to the above embodiment. In addition, the protective film covering step may be carried out before or after the pasting step, or before the modified layer forming step, but it is preferably carried out immediately before the dividing step.

Claims (1)

1. a method for dividing a device wafer is to form a method for dividing a device wafer with a device in each region divided by a plurality of division predetermined lines crossing, it is characterized in that it has: Pasting step, pasting the back side of the device wafer on the extension sheet; The modified layer forming step is to irradiate the device wafer with a laser beam having a transmittance wavelength relative to the device wafer along the planned division line of the device wafer before or after the sticking step, and form a layer on the device wafer along the planned dividing line of the device wafer. the modified layer of the dividing line; and In the dividing step, after the above-mentioned pasting step and the above-mentioned modified layer forming step are performed, an external force is applied to the device wafer by expanding the above-mentioned extended sheet on which the device wafer is pasted, thereby starting from the above-mentioned modified layer along the above-mentioned planned dividing line. Divide the device wafer, The dividing method of above-mentioned device wafer also has: A protective film covering step, at least before implementing the above-mentioned dividing step, covering the surface of the device wafer with a water-soluble protective film; and In the protective film removal step, the protective film is removed by washing after the above-mentioned dividing step is performed.

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