JP2017220557A - Electrostatic chuck sheet and processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck sheet which allows a wafer to be processed while suppressing breakage risk thereof, and to provide a processing method of wafer.SOLUTION: An electrostatic chuck sheet 1 includes an elastic base sheet, an electrode circuit 3 formed on the upper surface of the base sheet, a nonconductive resin layer 4 covering the upper surface of the base sheet and the electrode circuit 3 and composing a holding surface 4a on which a wafer W is placed, and a feeding terminal 5 for connection with the electrode circuit 3. The electrode circuit 3 consists of stems 7a, 7b for connection with the feeding terminal 5, and branches 6a, 6b breaking apart from the stem 7a into multiple and extending in wave-shape. In the wave-shape branches 6a, 6b, the branches 6a of positive electrode and branches 6b of negative electrode are staggered.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrostatic chuck sheet and a wafer processing method.

  A semiconductor circuit, a MEMS (Micro Electro Mechanical Systems) structure, an LED (Light Emitting Diode) element, or the like is irradiated with a laser beam on a wafer formed in a region partitioned by a division line, and breaks along the formed modified layer. Processing methods are known (see Patent Document 1 and Patent Document 2).

JP 2005-328441 A JP 2004-349623 A

  There is a method of breaking the wafer by extending the dicing tape to which the wafer is attached and applying an external force to the wafer to break the wafer. In this process, the wafer must be attached to a dicing tape larger than the diameter of the wafer. It is necessary to keep. In particular, in the processing method in which the wafer is divided into individual device chips by extending the cracks from the modified layer by external force due to the thinning after forming the modified layer on the wafer, the distance between the chips is increased after the division. In order to insert the tape into a pickup device that picks up afterwards or to attach a DAF (Die Attach Film) tape, a process of replacing and expanding the tape with a tape having a diameter larger than that of the wafer occurs. In this replacement work, since the chips have already been broken, the chips may be rubbed and damaged during the work.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an electrostatic chuck sheet and a wafer processing method capable of processing a wafer with reduced risk of wafer breakage.

  In order to solve the above-described problems and achieve the object, an electrostatic chuck sheet of the present invention includes a stretchable base sheet, an electrode circuit formed on the upper surface of the base sheet, an upper surface of the base sheet, and A non-conductive resin layer that covers the electrode circuit and constitutes a holding surface on which a wafer is placed, and a power supply terminal portion that is connected to the electrode circuit, are elastic.

  The electrode circuit includes a trunk portion connected to the power supply terminal portion, and a branch portion that divides into a plurality of portions from the trunk portion and extends in a wave shape, and the corrugated branch portions are alternately arranged with a positive electrode and a negative electrode. be able to.

  The base sheet can be composed of rubber, synthetic resin or cloth.

  The wafer processing method of the present invention is a wafer processing method for processing a wafer in which a device is formed in a region defined by division lines that intersect with each other on the surface, and a laser beam is applied to the wafer held by the electrostatic chuck sheet. A modified layer forming step for forming a modified layer along the line to be divided inside the wafer, and after the modified layer forming step, the electrostatic chuck sheet is expanded while holding the wafer. And an expansion step of breaking the wafer along the modified layer and dividing it into a plurality of device chips.

  In the wafer processing method, after the expansion step, the electrostatic chuck sheet is expanded, and a tape adhering step is performed in which a dicing tape is adhered to the exposed surface of the wafer in which the adjacent device chips are spaced. Can be provided.

  Therefore, the electrostatic chuck sheet of the present invention has an effect of enabling wafer processing with reduced risk of wafer breakage.

FIG. 1 is a plan view of the electrostatic chuck sheet according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a perspective view of the wafer held by the electrostatic chuck sheet shown in FIG. FIG. 4 is a cross-sectional view showing a base sheet preparation step of the electrostatic chuck sheet manufacturing method according to the first embodiment. FIG. 5 is a cross-sectional view illustrating an electrode forming step of the method for manufacturing the electrostatic chuck sheet according to the first embodiment. FIG. 6 is a cross-sectional view showing a non-conductive resin layer forming step of the electrostatic chuck sheet manufacturing method according to the first embodiment. FIG. 7 is a sectional side view showing a modified layer forming step of the wafer processing method according to the first embodiment. FIG. 8 is a side cross-sectional view showing an expansion step of the wafer processing method according to the first embodiment. FIG. 9 is a perspective view showing the conveyance frame and the like shown in FIG. FIG. 10 is a side cross-sectional view showing the tape attaching step of the wafer processing method according to the first embodiment. FIG. 11 is a plan view showing a tape attaching step of the wafer processing method according to the first embodiment. FIG. 12 is a perspective view showing an expansion step of the wafer processing method according to the second embodiment. FIG. 13 is a plan view of an electrostatic chuck sheet according to Embodiment 3 of the present invention.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment 1
A method for processing the electrostatic chuck sheet 1 and the wafer W according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the electrostatic chuck sheet according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a perspective view of the wafer held by the electrostatic chuck sheet shown in FIG.

  The electrostatic chuck sheet 1 according to the first embodiment holds the wafer W shown in FIG. In the present embodiment, the wafer W is a disk-shaped semiconductor wafer or optical device wafer having silicon, sapphire, gallium or the like as a base material. In the wafer W, as shown in FIG. 3, devices D are formed in each region defined by a plurality of division lines S where the surface WS intersects. As the device D, an IC (Integrated Circuit), an LSI (Large Scale Integration), a MEMS (Micro Electro Mechanical Systems), and the like are formed in each region.

  As shown in FIG. 1, the planar shape of the electrostatic chuck sheet 1 according to the first embodiment is formed in a square shape. The electrostatic chuck sheet 1 is formed in a stretchable sheet shape. As shown in FIG. 2, the electrostatic chuck sheet 1 includes a stretchable base sheet 2, an electrode circuit 3, a nonconductive resin layer 4, and a power supply terminal portion 5 connected to the electrode circuit 3.

  The base sheet 2 is made of rubber, synthetic resin or cloth. When the base sheet 2 is made of a synthetic resin, the base sheet 2 is preferably made of polyimide or polyolefin. The base sheet 2 is formed in a rectangular sheet shape. The base sheet 2 can expand and contract along the surface of the base sheet 2. The thickness of the base sheet 2 is about 100 μm to 800 μm, and preferably about 100 μm to 300 μm.

  The power feeding terminal portion 5 is formed on the upper surface of the base sheet 2. As shown in FIG. 1, the power supply terminal portion 5 includes a positive electrode power supply terminal portion 5a and a negative electrode power supply terminal portion 5b. The positive electrode power supply terminal portion 5a and the negative electrode power supply terminal portion 5b are provided at outer edge portions 1a and 1b that sandwich the center of the base sheet 2 therebetween. In the first embodiment, the positive electrode power supply terminal portion 5a and the negative electrode power supply terminal portion 5b are disposed at the centers of the outer edge portions 1a and 1b of the base sheet 2, respectively. The positive electrode power supply terminal portion 5a and the negative electrode power supply terminal portion 5b are each made of a conductive metal. A positive voltage is applied to the positive electrode power supply terminal portion 5a, and a negative voltage is applied to the negative electrode power supply terminal portion 5b.

  The electrode circuit 3 is formed on the upper surface of the base sheet 2. The electrode circuit 3 includes a positive electrode circuit 3a and a negative electrode circuit 3b. The positive electrode circuit 3a is connected to the positive electrode power supply terminal portion 5a, and the negative electrode circuit 3b is connected to the negative electrode power supply terminal portion 5b. The positive electrode circuit 3a is made of metal, and includes a trunk portion 7a that is connected to the positive electrode power supply terminal portion 5a, and a branch portion 6a that diverges from the trunk portion 7a and extends in a wave shape. The trunk portion 7a is formed in a straight line parallel to the outer edge portion 1a of the base sheet 2 provided with the positive electrode feeding terminal portion 5a. The branch portion 6a extends from the outer edge portion 1a of the base sheet 2 provided with the positive electrode power supply terminal portion 5a toward the outer edge portion 1b of the base sheet 2 provided with the negative electrode power supply terminal portion 5b. A plurality of branch portions 6a are provided between the outer edge portions 1a and 1b. The branch portion 6a is formed in a wave shape that alternately meanders from side to side as it goes from the outer edge portion 1a to the outer edge portion 1b.

  The negative electrode circuit 3b is made of metal, and includes a trunk portion 7b that is connected to the negative electrode feeding terminal portion 5b, and a branch portion 6b that is separated from the trunk portion 7b and extends in a wave shape. The trunk portion 7b is formed in a straight line parallel to the outer edge portion 1b of the base sheet 2 provided with the negative electrode feeding terminal portion 5b. The branch portion 6b extends from the outer edge portion 1b of the base sheet 2 provided with the negative electrode power supply terminal portion 5b toward the outer edge portion 1a of the base sheet 2 provided with the positive electrode power supply terminal portion 5a. A plurality of branch portions 6b are provided between the outer edge portions 1a and 1b. The branch portion 6b is formed in a wave shape that alternately meanders from side to side as it goes from the outer edge portion 1b to the outer edge portion 1a. In addition, one branch 6b of the negative electrode circuit 3b is disposed between two adjacent branches 6a of the positive electrode circuit 3a, and between the two adjacent branches 6b of the negative electrode circuit 3b. A single branch 6a is disposed in the positive electrode circuit 3a. Thus, in the electrode circuit 3, the branch portions 6a and the branch portions 6b are alternately arranged. In the wave-shaped branches 6a and 6b of the electrode circuit 3, the branches 6a of the positive electrode circuit 3a and the branches 6b of the negative electrode circuit 3b are alternately arranged.

  In the first embodiment, the distance between the corrugated branches 6a and 6b of the electrode circuits 3 adjacent to each other is preferably 0.1 mm or more and 5.0 mm or less, more preferably 0.5 mm or more and 2,0 mm. It is further desirable that: Further, the branch portions 6a and 6b of the electrode circuit 3 are formed in a wave shape and have elasticity. In the first embodiment, the branch portions 6a and 6b are formed in a wave shape, but are not limited to the wave shape and may be formed in a saw blade shape. In addition, the power supply terminal portion 5 and the electrode circuit 3 are preferably made of copper paste or silver paste, and preferably have a thickness of 3 μm to 30 μm.

  The nonconductive resin layer 4 is made of a nonconductive and stretchable material. The non-conductive resin layer 4 covers the upper surface of the base sheet 2 and the electrode circuit 3, and constitutes a holding surface 4a on which the wafer W is placed. The non-conductive resin layer 4 is formed with a notch 4 b that exposes each power supply terminal portion 5. The notch 4b exposes all or part of each power supply terminal portion 5. The non-conductive resin layer 4 is preferably composed of UV (Ultraviolet) type clear ink manufactured by Teikoku Ink Manufacturing Co., Ltd., and preferably has a thickness of 20 μm to 200 μm.

  In the electrostatic chuck sheet 1, a wafer W is placed on the holding surface 4a of the non-conductive resin layer 4, and a positive voltage is applied from the positive electrode power supply terminal portion 5a to the positive electrode circuit 3a, and from the negative electrode power supply terminal portion 5b. By applying a negative voltage to the negative electrode circuit 3b, the wafer W is attracted and held by the force generated between the branch portions 6a and 6b. In the first embodiment, the voltage applied to the electrode circuits 3a and 3b from the power supply terminal portions 5a and 5b is preferably 1000 V or more and 2000 V or less.

  Next, a method for manufacturing the electrostatic chuck sheet 1 will be described with reference to the drawings. FIG. 4 is a cross-sectional view showing a base sheet preparation step of the electrostatic chuck sheet manufacturing method according to the first embodiment. FIG. 5 is a cross-sectional view illustrating an electrode forming step of the method for manufacturing the electrostatic chuck sheet according to the first embodiment. FIG. 6 is a cross-sectional view showing a non-conductive resin layer forming step of the electrostatic chuck sheet manufacturing method according to the first embodiment.

  When manufacturing the electrostatic chuck sheet 1, first, in the base sheet preparation step, as shown in FIG. 4, the base sheet 2 is prepared. Thereafter, in the electrode forming step, as shown in FIG. 5, the feeding terminal portion 5 and the electrode circuit 3 are formed on the upper surface of the base sheet 2 by screen printing or ink jet printing. Then, in the non-conductive resin layer forming step, as shown in FIG. 6, UV (Ultraviolet) type clear ink manufactured by Teikoku Ink Manufacturing Co., Ltd. is used as the upper surface of the base sheet 2 and the electrode circuit 3 except for the notch 4b. The non-conductive resin layer 4 is formed by spreading on the top using a squeegee or by spin coating.

  Next, a method for processing the wafer W using the electrostatic chuck sheet 1 will be described with reference to the drawings. FIG. 7 is a sectional side view showing a modified layer forming step of the wafer processing method according to the first embodiment. FIG. 8 is a side cross-sectional view showing an expansion step of the wafer processing method according to the first embodiment. FIG. 9 is a perspective view showing the conveyance frame and the like shown in FIG. FIG. 10 is a side cross-sectional view showing the tape attaching step of the wafer processing method according to the first embodiment. FIG. 11 is a plan view showing a tape attaching step of the wafer processing method according to the first embodiment.

  The wafer W processing method (hereinafter simply referred to as a processing method) is a method of processing the wafer W shown in FIG. 3, and the wafer W is irradiated with a laser beam L (shown in FIG. 7) to form a modified layer inside. In this method, K (shown in FIG. 7, etc.) is formed and divided into individual device chips DT (shown in FIG. 8, etc.). It is. The device chip DT includes the device D. The modified layer K means a region where the density, refractive index, mechanical strength and other physical characteristics are different from those of the surroundings, and includes a melt-treated region, a crack region, and a dielectric breakdown region. , A refractive index change region, a region where these regions are mixed, and the like.

  The processing method includes a modified layer forming step, an expansion step, and a tape sticking step. The modified layer forming step is a step of irradiating the wafer W held by the electrostatic chuck sheet 1 with the laser beam L to form the modified layer K along the division line S inside the wafer W. In the modified layer forming step, the base sheet 2 of the electrostatic chuck sheet 1 is placed on the porous holding surface 11a of the chuck table 11 of the laser processing apparatus 10 as shown in FIG. The surface WS of the wafer W is placed on the holding surface 4 a of the non-conductive resin layer 4. The suction force of the vacuum suction source 13 connected to the chuck table 11 via the switching valve 12 is applied to the holding surface 11 a to suck the electrostatic chuck sheet 1, and the surface of the wafer W via the electrostatic chuck sheet 1. The WS side is sucked and held on the holding surface 11 a of the chuck table 11.

  Further, the power supply terminal portions 11 a and 11 b of the chuck table 11 are connected to the power supply terminal portions 5 a and 5 b, a predetermined voltage is applied to the electrode circuits 3 a and 3 b, and the wafer W is sucked and held on the electrostatic chuck sheet 1.

  And alignment is performed based on the image which the imaging means (not shown) of the laser processing apparatus 10 acquired. Thereafter, while the chuck table 11 and the laser beam irradiation means 14 are relatively moved by the moving means, as shown in FIG. 7, the rear surface WR of the wafer W held on the chuck table 11 is made transparent to the wafer W. A laser beam L having a wavelength (for example, 1064 nm) is irradiated along the planned division line S with the condensing point inside the wafer W. Then, the modified layer K along the planned division line S is formed inside the wafer W. Then, the process proceeds to the expansion step.

  The expansion step is a step of expanding the electrostatic chuck sheet 1 while holding the wafer W after the modified layer forming step, breaking the wafer W along the modified layer K, and dividing it into a plurality of device chips DT. . The expansion step is performed by pressing the electrostatic chuck sheet 1 against the holding surface 11a of the chuck table 11 by the annular frame 30 while positioning the annular frame 30 surrounding the wafer W on the outer periphery of the wafer W (to prevent leakage). As shown in FIG. 8, the changeover valve 12 is changed over to cause the pressurized gas of the air supply source 15 connected to the chuck table 11 via the changeover valve 12 to be ejected from the holding surface 11a. Then, expand the electrostatic chuck sheet 1 into a spherical shape. When the electrostatic chuck sheet 1 is expanded, the electrostatic chuck sheet 1 becomes spherical, and an external force that expands in the radial direction is applied to the wafer W, so that the modified layer K formed along the division line S is formed. Apply tension to the. Then, starting from the modified layer K, the wafer W is divided into individual device chips DT along the planned division line S, and the device chips DT are separated from each other. And it progresses to a tape sticking step.

  When proceeding from the expansion step to the tape sticking step, the wafer W is conveyed from the laser processing apparatus 10 to the tape sticking apparatus 20 shown in FIGS. At this time, the laser processing device 10 places the transport frame 31 on the outer edge portions 1a, 1b, and 1c of the electrostatic chuck sheet 1 in a state where the electrostatic chuck sheet 1 is expanded. In the first embodiment. As shown in FIG. 9, four conveyance frames 31 are provided corresponding to the outer edge portions 1 a, 1 b, and 1 c of the electrostatic chuck sheet 1.

  The transfer frame 31 is formed in a quadrangular prism and is attached to a transfer arm of a transfer device (not shown). The conveyance frame 31 sucks and holds the non-conductive resin layer 4 of the electrostatic chuck sheet 1 by the suction force from the suction source 32. Of the four transport frames 31, two transport frames 31a overlapping the power supply terminal portion 5 can apply a predetermined voltage to the electrode circuits 3a and 3b via the power supply terminal portions 5a and 5b. A power supply 33 is connected.

  The transport frame 31 is placed on the outer edge portions 1 a, 1 b, 1 c of the electrostatic chuck sheet 1 and then sucks and holds the nonconductive resin layer 4 of the electrostatic chuck sheet 1. Then, the application of predetermined power from the power supply terminal portions 11a and 11b of the laser processing apparatus 10 to the electrode circuits 3a and 3b via the power supply terminal portions 5a and 5b is stopped and the two transport frames 31a are applied. Application of predetermined power from the connected power supply 33 to the electrode circuits 3a and 3b via the power supply terminal portions 5a and 5b is started. In this way, the transport device can transport the electrostatic chuck sheet 1 while holding the wafer W divided into the device chips DT by suction.

  The transport device removes the electrostatic chuck sheet 1 that sucks and holds the wafer W from the chuck table 11 of the laser processing apparatus 10. The intervals between the device chips DT can also be maintained by slightly separating the transport frames 31 from each other. The conveying device places the electrostatic chuck sheet 1 that sucks and holds the wafer W divided into device chips DT on the porous holding surface 21a of the chuck table 21 of the tape sticking device 20, and performs the tape sticking step. Run.

  In the tape adhering step, after the expansion step, the expansion of the electrostatic chuck sheet 1 is maintained, and the dicing tape T is adhered to the back surface WR, which is the exposed surface of the wafer W in which the adjacent device chips DT are spaced apart. It is a step. In the tape attaching step, the outer edge portions 1a and 1b of the electrostatic chuck sheet 1 are clamped by the clamps 22 of the chuck table 21, and the expansion of the electrostatic chuck sheet 1 is maintained. The suction force of the vacuum suction source 24 connected to the chuck table 21 via the switching valve 23 is applied to the holding surface 21 a to suck the electrostatic chuck sheet 1, and the surface of the wafer W via the electrostatic chuck sheet 1. The WS side is sucked and held on the holding surface 11 a of the chuck table 11.

  Thereafter, the suction holding of the transport frame 31 of the transport device is stopped, the application of voltage from the power supply 33 connected to the two transport frames 31a through the power supply terminal portions 5a and 5b is stopped, and the chuck table A predetermined power is applied from the 20 clamps 22 to the electrode circuits 3a and 3b through the power supply terminal portions 5a and 5b, and the conveying device is retracted from the tape sticking device 20. As shown in FIGS. 10 and 11, the ring ring frame F is stacked on the outer edge portions 1 a, 1 b, 1 c of the electrostatic chuck sheet 1, and the dicing tape T is used by using the sticking unit 25 of the tape sticking device 20. Is attached to the back surface WR and the ring frame F of the wafer W divided into device chips DT. When the attachment of the dicing tape T is completed, the application to the electrode circuits 3a and 3b is stopped, and the wafer W to which the dicing tape T is attached is conveyed to the next step.

  As described above, in the electrostatic chuck sheet 1 and the processing method according to the first embodiment, since the base sheet 2, the electrode circuit 3, and the non-conductive resin layer 4 have elasticity, the wafer on which the modified layer K is formed. The wafer W can be divided into device chips DT by being expanded in the expansion step while W is held. In addition, since the base sheet 2, the electrode circuit 3, and the non-conductive resin layer 4 have elasticity, the electrostatic chuck sheet 1 can hold the wafer W in an expanded state after being divided into device chips DT. Therefore, it is possible to process the wafer W while suppressing the risk of damage to the device chip DT, that is, the wafer W.

  In addition, since the electrostatic chuck sheet 1 and the processing method according to the first embodiment hold the wafer W by the force generated between the branch portions 6a and 6b of the electrode circuits 3a and 3b, the wafer W is held on the adhesive tape. As compared with the above, there is an effect that there is no adhesive residue because the adhesive layer is not adhered to the surface of the device D. In particular, in the electrostatic chuck sheet 1 and the processing method according to the first embodiment, when the surface WS of the wafer W on which the electrode bumps are arranged is fixed to the holding surface 4a of the electrostatic chuck sheet 1, uneven electrode bumps are formed. This is effective for the problem that the adhesive layer adhesive remains on the electrode bumps when fixed to the adhesive tape.

  The electrostatic chuck sheet 1 according to the first embodiment can be expanded and contracted without damaging the electrode circuit 3 because the branch portions 6a and 6b of the electrode circuits 3a and 3b are formed in a wave shape. The electrostatic chuck sheet 1 according to the first embodiment is extensible because the base sheet 2 is made of rubber, synthetic resin, or cloth.

  In addition, the processing method according to the first embodiment includes an expansion step of expanding the electrostatic chuck sheet 1 while holding the wafer W and dividing it into device chips DT after the modified layer forming step. It is possible to process the wafer W with reduced risk.

  In addition, since the processing method according to the first embodiment includes the tape sticking step of sticking the dicing tape T to the back surface WR of the wafer W in which the device chips DT are spaced apart from each other after the expansion step, the device chip after the division. It is possible to suppress rubbing between DTs.

[Embodiment 2]
A wafer processing method according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 12 is a perspective view showing an expansion step of the wafer processing method according to the second embodiment. In FIG. 12, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 12, the processing method of the wafer W according to the second embodiment includes an electrostatic chuck sheet 1 in which the wafer W is sucked and held by power feeding from the transport frame 31 of the transport device after the modified layer forming step. Is held by vacuum suction. In the wafer W processing method according to the second embodiment, the electrostatic chuck sheet 1 is expanded by relatively moving the conveyance frames 31 in directions away from each other, and the wafer W is divided into a plurality of device chips DT. To do.

  According to the method for processing a wafer W according to the second embodiment, the modified layer K is formed because the base sheet 2, the electrode circuit 3, and the non-conductive resin layer 4 are stretchable as in the first embodiment. The wafer W can be divided into device chips DT by being expanded in the expansion step while holding the wafer W. In addition, since the base sheet 2, the electrode circuit 3, and the non-conductive resin layer 4 have elasticity, the electrostatic chuck sheet 1 can hold the wafer W in an expanded state after being divided into device chips DT. Therefore, it is possible to process the wafer W while suppressing the risk of damage to the device chip DT, that is, the wafer W. In the first and second embodiments, the step of replacing the dicing tape T with the dicing tape T has been exemplified. However, the present invention provides a pickup apparatus that picks up the device chip DT while holding the wafer W with the electrostatic chuck sheet 1 after the expansion step. You can bring it in. In particular, in the case of the wafer W in which the device D is a MEMS, the present invention exposes the surface of the MEMS in the modified layer forming step, and it is not necessary to replace the front and back with the dicing tape T. You will pick up later. In that case, the electrostatic chuck sheet 1 that can be used repeatedly eliminates the need to use consumables such as adhesive tapes such as the dicing tape T, thereby greatly reducing the manufacturing cost.

[Embodiment 3]
An electrostatic chuck sheet according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 13 is a plan view of an electrostatic chuck sheet according to Embodiment 3 of the present invention. In FIG. 13, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 13, the electrostatic chuck sheet 1 according to the third embodiment includes a plurality of electrode blocks 8. Each electrode block 8 includes a power supply terminal portion 5 and an electrode circuit 3, and is configured to be able to apply power to the electrode circuit 3 independently of each other. In the third embodiment, the electrostatic chuck sheet 1 includes four electrode blocks 8.

  According to the electrostatic chuck sheet 1 according to the third embodiment, the modified layer K is formed because the base sheet 2, the electrode circuit 3, and the non-conductive resin layer 4 have elasticity as in the first embodiment. The wafer W can be divided into device chips DT by being expanded in the expansion step while holding the wafer W. In addition, since the base sheet 2, the electrode circuit 3, and the non-conductive resin layer 4 have elasticity, the electrostatic chuck sheet 1 can hold the wafer W in an expanded state after being divided into device chips DT. Therefore, it is possible to process the wafer W while suppressing the risk of damage to the device chip DT, that is, the wafer W.

  In addition, according to the electrostatic chuck sheet 1 according to the third embodiment, since a plurality of electrode blocks 8 that are independent from each other are provided, most of the electrode circuits 3a and 3b of most of the divided electrode blocks 8 are applied with a voltage. While the device chips DT are adsorbed, the application of voltages to the electrode circuits 3 a and 3 b of some electrode blocks 8 can be stopped to remove some device chips DT from the electrostatic chuck sheet 1.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Electrostatic chuck sheet 2 Base sheet 3 Electrode circuit 4 Non-conductive resin layer 4a Holding surface 5 Power supply terminal portion 6a, 6b Branch portion 7a, 7b Trunk portion W Wafer WS Surface WR Back surface (Exposed surface)
D device DT device chip L laser beam K modified layer T dicing tape

Claims (5)

An elastic base sheet,
An electrode circuit formed on the upper surface of the base sheet;
A non-conductive resin layer constituting a holding surface for covering the upper surface of the base sheet and the electrode circuit and placing the wafer thereon;
An electrostatic chuck sheet comprising a power supply terminal portion connected to the electrode circuit and having elasticity. The electrode circuit is composed of a trunk part connected to the power supply terminal part, and a branch part extending in a wave shape from the trunk part.
The electrostatic chuck sheet according to claim 1, wherein the corrugated branch portion has a positive electrode and a negative electrode arranged alternately.   The electrostatic chuck sheet according to claim 1, wherein the base sheet is made of rubber, synthetic resin, or cloth. A wafer processing method for processing a wafer in which a device is formed in a region defined by lines to be divided on a surface,
A modified layer forming step of irradiating the wafer held by the electrostatic chuck sheet according to claim 1, 2 or 3 with a laser beam, and forming a modified layer along the planned division line inside the wafer;
After the modified layer forming step, the electrostatic chuck sheet is expanded while holding the wafer, and the wafer is processed along with the modified layer, and the wafer is broken and divided into a plurality of device chips. Method.   5. The tape attaching step of maintaining the extension of the electrostatic chuck sheet after the expanding step and attaching a dicing tape to an exposed surface of a wafer in which the adjacent device chips are spaced apart. Wafer processing method.

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