JP2014199834A - Holding means and processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide holding means capable of performing the handling of a work-piece inexpensively and having no fear that paste and an adhesive remain on the surface of the work-piece.SOLUTION: Holding means has a holding surface which holds a work-piece having a central region and an outer peripheral excess region surrounding the central region. The holding surface corresponding to the central region of at least the work-piece is formed by a flexible member. The holding means includes: a plurality of suction holes which open to the holding surface corresponding to the outer peripheral excess region of the work-piece; and a suction path having one end communicated with the suction hole and the other end selectively connected to a suction source.

Description

  The present invention relates to a holding unit having a holding surface for holding a workpiece and a method for processing the workpiece held by the holding unit.

  Workpieces such as semiconductor wafers and optical device wafers are ground on the backside with the holding means held by the holding means, or a laser beam is irradiated from the backside to form a modified layer inside the workpiece, By applying an external force, the chip is divided into individual chips along the modified layer.

  As the holding means, a holding table having a holding surface for holding a workpiece as disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-229889 is widely used, and the surface side of the workpiece is sucked into the holding table. Suction hold.

  If the surface of the workpiece is in direct contact with the holding surface, the workpiece surface may be scratched or foreign matter may adhere to it. To prevent this, a protective tape or protective member is applied to the surface of the workpiece in advance. Is disposed.

  A protective tape consists of a base material and the paste layer arrange | positioned on a base material, and a protective tape is stuck by the surface of a workpiece by a paste layer. As the protective member, for example, a hard plate made of silicon or glass is widely used, and is disposed on the surface of the workpiece through an adhesive. Generally, the protective tape is disposable for each workpiece, and the protective member is often used repeatedly.

JP 2007-229889 A

  However, since the protective tape is disposable for each workpiece, there is a problem that the cost of the protective tape is high and it is not economical. Even in the protective member that is used repeatedly, the adhesive is not economical because it is disposable for each workpiece.

  Furthermore, when removing the protective tape and the protective member from the surface of the workpiece, it is difficult to completely remove the adhesive of the protective tape and the adhesive of the protective member. In particular, in the case where the workpiece is a device wafer on which a semiconductor device or an optical device is formed, glue or adhesive remains in the minute unevenness of the device, which may cause a device defect or the like later.

  The present invention has been made in view of these points, and the object of the present invention is to allow the workpiece to be handled at a lower cost and to prevent the glue or adhesive from remaining on the workpiece surface. It is to provide a holding means.

  According to the first aspect of the present invention, the holding means has a holding surface for holding a workpiece having a central region and an outer peripheral surplus region surrounding the central region, and at least corresponds to the central region of the workpiece. The holding surface is formed of a flexible member, and a plurality of suction holes opened on the holding surface corresponding to the outer peripheral surplus area of the workpiece, one end communicating with the suction hole and the other end selected as a suction source And a suction path connected to each other.

  Preferably, the holding means further includes a plurality of central suction holes that open to the holding surface made of the flexible member and are selectively connected to the suction source.

  According to invention of Claim 3, it is a processing method which processes to the workpiece hold | maintained at the holding means of Claim 1 or Claim 2, Comprising: One surface side of a workpiece is this holding of this holding means A placement step for placing the workpiece directly on a surface; and operating the suction source to suck and hold the outer peripheral surplus region of the workpiece by the suction hole, and the flexible region for the central region of the workpiece. A holding step for supporting and exposing the other surface opposite to the one surface of the workpiece; a processing step for performing processing on the workpiece from the other surface side of the workpiece after performing the holding step; A processing method characterized by comprising:

  According to the holding means of the present invention, it is possible to handle the workpiece at a lower cost and prevent the possibility of glue or adhesive remaining on the surface of the workpiece as compared with the conventional method using a protective tape or a protective member. it can.

  That is, the holding means of the present invention has a plurality of suction holes for sucking the outer peripheral surplus region surrounding the central region, while the region corresponding to the central region of the workpiece on the holding surface is made of a flexible member. Therefore, even if the workpiece is directly brought into contact with the holding surface without using a protective tape or a protective member, the central region of the workpiece is not scratched or foreign matter adheres. With the workpiece directly in contact with the holding surface, the outer peripheral surplus area of the workpiece is sucked through the suction hole and sucked and held by the holding means.

It is a perspective view of the holding table of a 1st embodiment of the present invention. It is a surface side perspective view of a semiconductor wafer. It is a longitudinal cross-sectional view which shows a mounting step. It is a longitudinal cross-sectional view which shows a holding step. It is a block diagram of a laser beam irradiation unit. It is a partial cross section side view which shows a modified layer formation step. It is a partial cross section side view which shows a back surface grinding step. FIG. 8A is a perspective view of the holding table of the second embodiment, and FIG. 8B is a longitudinal sectional view thereof.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a holding table (holding means) 10 according to the first embodiment of the present invention is shown. The holding table 10 includes a frame body 12 made of a metal such as SUS, and a holding section 14 having a holding surface 14 a surrounded by the frame body 12. The upper surface 12a of the frame 12 acts as a holding surface, and the holding surface 14a of the holding unit 14 and the holding surface 12a of the frame 12 are formed flush with each other.

  The holding part 14 is formed of a flexible member, and is preferably flat and has a tack force on the workpiece. For example, KERATHERM (registered trademark of KERAFOL Keramische Folien GmbH) can be used.

  A plurality of suction holes 16 that are spaced apart by a predetermined distance in the circumferential direction are opened on the upper surface (holding surface) 12 a of the frame 12. As shown in FIG. 3, each suction hole 16 is connected to a suction source 22 via a suction path 18 formed in the frame 12 of the holding table 10 and an electromagnetic switching valve 20. Instead of forming the plurality of suction holes 16 on the upper surface 12a of the frame body 12, an annular suction groove may be formed.

  Referring to FIG. 2, a front side perspective view of a semiconductor wafer 11 as an example of a workpiece is shown. The semiconductor wafer 11 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of division lines (streets) 13 are formed in a lattice shape on the surface 11 a and are partitioned by the plurality of division lines 13. Devices 15 such as IC and LSI are formed in each region.

  The thus configured semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11 includes a device region (center region) 17 in which the device 15 is formed, and an outer peripheral surplus region 19 surrounding the device region 17. It is provided on the flat part of the surface. An arc-shaped chamfered portion 11 e is formed on the outer peripheral portion of the wafer 11. Reference numeral 21 denotes a notch as a mark indicating the crystal orientation of the silicon wafer.

  Hereinafter, a processing method using the holding table 10 configured as described above will be described. First, as shown in FIG. 3, a mounting step for mounting the surface 11 a of the wafer 11 directly on the holding table 10 is performed.

  In this placement step, the device region (center region) 17 formed on the surface 11a of the wafer 11 abuts on the holding surface 14a of the holding unit 14, but the holding unit 14 is formed of a flexible member. No foreign matter adheres to or scratches 17.

  Next, the electromagnetic switching valve 20 is switched to the communication position, and a plurality of suction holes 16 opened on the upper surface (holding surface) 12 a of the frame 12 are connected to the suction source 22 via the suction path 18, and the suction holes 16 are negatively connected. Pressure is applied and the outer peripheral surplus area 19 of the wafer 11 is sucked and held by the holding table 10. At this time, the device region 17 of the wafer 11 is brought into contact with the holding surface 14a of the holding unit 14 without being sucked.

  In the processing method of the first embodiment, a modified layer forming step of forming a modified layer inside the wafer 11 by irradiating the wafer 11 held on the holding table 10 with a laser beam is performed.

  This modified layer forming step is performed using a laser beam irradiation unit 24 as shown in the block diagram of FIG. The laser beam irradiation unit 24 includes a laser beam generation unit 26 and a condenser (laser head) 28.

  The laser beam generation unit 26 includes a laser oscillator 30 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 32, a pulse width adjustment unit 34, and a power adjustment unit 36. The laser oscillator 30 oscillates a laser having a wavelength of 1064 nm that is transparent to the wafer 11.

  The pulsed laser beam adjusted to a predetermined power by the power adjusting means 36 of the laser beam generating unit 26 is reflected by the mirror 38 of the condenser 28 and further condensed by the condenser objective lens 40 and held on the holding table 10. The irradiated wafer 11 is irradiated.

  More specifically, as shown in FIG. 6, the pulsed laser beam is irradiated along the planned dividing line 13 so as to be focused on the focusing point P inside the wafer 11 by the condenser 28, and the holding table 10 is moved to the arrow. By processing and feeding in the X1 direction, the modified layer 23 is formed inside the wafer 11.

  A similar modified layer 23 is formed inside the wafer 11 along all the planned division lines 13 extending in the first direction while indexing the holding table 10. Next, after the holding table 10 is rotated by 90 degrees, the same modified layer 23 is formed inside the wafer 11 along all the planned dividing lines 13 extending in the second direction orthogonal to the first direction.

  In the processing method according to the present embodiment, since the modified layer 23 is formed inside the wafer 11, the device region 17 of the wafer 11 is not sucked and held, and only the outer peripheral region 19 is sucked and held relatively. Even weak suction holding can sufficiently withstand practical use.

  Next, with reference to FIG. 7, the processing method of 2nd Embodiment is demonstrated. In this embodiment, a grinding step for grinding the back surface 11b of the wafer 11 is performed. In FIG. 7, a grinding unit (grinding means) 42 includes a spindle 44 that is rotationally driven, a wheel mount 46 that is fixed to the tip of the spindle 44, and a grinding wheel 48 that is detachably attached to the wheel mount 46 by bolts (not shown). Including. The grinding wheel 48 includes an annular base 50 and a plurality of grinding wheels 52 fixed to the lower end portion of the annular base 50.

  In the back grinding step, the holding table 10 is rotated in the direction of arrow a at 300 rpm, for example, and the grinding wheel 52 is rotated by rotating the grinding wheel 48 in the direction of arrow b at 6000 rpm, for example. 11 is brought into contact with the back surface 11b.

  The grinding wheel 48 is ground by a predetermined amount at a predetermined grinding feed speed, and the back surface 11b of the wafer 11 is ground. The wafer 11 is ground to a desired thickness while measuring the thickness of the wafer 11 with a contact or non-contact thickness gauge.

  Since the holding portion 14 is formed of a flexible member having a tacking force with respect to the wafer 11, the wafer 11 is sucked and held by the holding table 10 even in a holding method in which only the outer peripheral area 19 of the wafer 11 is sucked and held. Then, the back surface grinding of the wafer 11 can be performed.

  Referring to FIG. 8A, a perspective view of a holding table 10A according to the second embodiment of the present invention is shown. FIG. 8B is a longitudinal sectional view thereof. In the holding table 10 </ b> A of the present embodiment, a plurality of central suction holes 16 a are opened on the holding surface 14 a of the holding portion 14 in addition to the suction holes 16 formed on the upper surface (holding surface) 12 a of the frame 12.

  Similar to the holding table 10 of the first embodiment, the holding portion 14 is formed of a flexible member having a tack force against the workpiece, and opens to the holding surface 14a as shown in FIG. 8B. The plurality of central suction holes 16 a are selectively connected to the suction source 22 via the suction path 18 and the electromagnetic switching valve 20.

  In the holding table 10A of the present embodiment, in addition to the suction holes 16 opened on the upper surface 12a of the frame 12, a plurality of central suction holes 16a opened on the holding surface 14a of the holding portion 14 formed of a flexible member are provided. It can exhibit a strong suction force and is suitable for use as, for example, a holding table for performing a back grinding step as shown in FIG.

  In the above-described embodiment, the semiconductor wafer 11 has been described as the workpiece to be held by the holding table 10, but the workpiece is not limited to the semiconductor wafer, and the holding tables 10 and 10A of the present invention are optical. It can also be used to hold other workpieces such as device wafers.

10, 10A Holding table 11 Semiconductor wafer 12 Frame 12a Upper surface (holding surface)
14 Holding part 14a Holding surface 16 Suction hole 16a Central suction hole 18 Suction path 23 Modified layer 28 Condenser (laser head)
48 grinding wheel

Claims (3)

A holding means having a holding surface for holding a work piece having a central region and an outer peripheral surplus region surrounding the central region,
The holding surface corresponding to at least the central region of the workpiece is formed of a flexible member;
A plurality of suction holes opened in the holding surface corresponding to the outer peripheral surplus area of the workpiece;
A suction path having one end communicating with the suction hole and the other end selectively connected to a suction source;
The holding means characterized by comprising.   The holding means according to claim 1, further comprising a plurality of central suction holes that open to the holding surface made of the flexible member and are selectively connected to the suction source. A processing method for processing a workpiece held by the holding means according to claim 1 or 2,
A placing step of placing one surface side of the workpiece directly on the holding surface of the holding means;
The suction source is actuated to suck and hold the outer peripheral area of the work piece by the suction hole, and the central area of the work piece is supported by the flexible member to be opposite to the one surface of the work piece. A holding step to expose the other side;
A processing step of processing the workpiece from the other side of the workpiece after performing the holding step;
A processing method characterized by comprising:

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