CN110634736A - The processing method of the processed object - Google Patents

Abstract

To provide a processing method of a workpiece that can identify the crystal orientation of the wafer even when the outer periphery of the wafer (plate-shaped workpiece) is trimmed. In the outer peripheral edge removal step of this processing method, the outer peripheral edge (7) of the front surface (2a) is cut while the cutting tool is oscillated in the radial direction of the wafer (1), so that the front surface (2a) has an elliptical shape . In addition, in this outer peripheral edge removal step, the cutting tool is oscillated so that the short side (L2) of the ellipse shape of the front surface (2a) is along the extending direction of the notch (9) indicating the crystallographic orientation of the wafer (1). Thus, the oval shape of the front side (2a) corresponds to the crystallographic orientation of the wafer (1). Then, the entire wafer (1) has an elliptical shape as the shape of the front surface (2a) by a grinding step after the peripheral edge removing step. Therefore, in the wafer (1), the crystal orientation of the wafer (1) can be discriminated from the ellipse shape.

Description

The processing method of the processed object

technical field

The present invention relates to a method for processing a workpiece.

Background technique

Among plate-shaped workpieces such as wafers, some workpieces are chamfered from the front surface to the back surface on the outer periphery. When such a plate-shaped workpiece is thinned to less than half the thickness, so-called sharp edges are formed on the outer periphery, and the plate-shaped workpiece may be damaged. In order to prevent this, there is known a technique of thinning the plate-shaped workpiece after trimming the outer periphery of the plate-shaped workpiece to remove chamfers (for example, refer to Patent Document 1).

In addition, notches showing crystal orientations are sometimes formed on plate-like workpieces. The notches are used, for example, as marks when dividing a plate-shaped workpiece into devices (for example, refer to Patent Document 2). The notch shape is determined by, for example, SEMI specifications which are industry standard specifications. The outer periphery of the plate-shaped workpiece in which the notches are formed is also trimmed to remove chamfers, and then thinned.

Patent Document 1: Japanese Patent Laid-Open No. 2000-173961

Patent Document 2: Japanese Patent Laid-Open No. 2004-198264

However, in the trimmed plate-shaped workpiece, the notch becomes smaller or disappears after thinning. Therefore, it is difficult to accurately detect the crystal orientation of the plate-shaped workpiece in the subsequent process.

Contents of the invention

The present invention has been made in view of such a problem, and an object of the present invention is to identify the crystal orientation of a plate-shaped workpiece even when the outer periphery of the plate-shaped workpiece is trimmed.

The method of processing a workpiece according to the present invention is a method of processing a workpiece having a front surface of a device formed in a region divided by a plurality of planned division lines formed in a lattice shape, and is characterized in that the processing of the workpiece The method has the following steps: a holding step of holding the back surface of the workpiece with a holding table to expose the front surface of the workpiece; a peripheral edge removing step of cutting a cutting tool into the To the outer peripheral edge of the front surface of the workpiece, the holding table is rotated and the cutting tool is swung in the radial direction of the workpiece so that the outer peripheral edge of the workpiece is changed while changing the cutting width. performing cutting; a front protection step, after implementing the outer peripheral edge removal step, using a front protection member to cover the region where the device is formed on the front of the workpiece; and a grinding step, after implementing the front protection step Afterwards, the back surface of the workpiece is ground with a grinding tool to thin the workpiece to a predetermined thickness, and in the outer peripheral edge removal step, the workpiece is cut while changing the cutting width. The outer peripheral edge of the front surface is cut, and the outer peripheral edge is removed so that the front surface of the workpiece has an elliptical shape corresponding to the crystal orientation of the workpiece, so that the surface of the workpiece can be identified by the elliptical shape crystal orientation.

In the processing method of the present invention, in the outer peripheral edge removing step, the outer peripheral edge of the front surface of the workpiece is cut while changing the cutting width. Thus, the outer peripheral edge is removed from the front surface of the workpiece, and the front surface of the workpiece has an elliptical shape corresponding to the crystal orientation of the workpiece. Then, in the grinding step following the outer peripheral edge removing step, the outer peripheral edge of the back surface of the workpiece is also ground (removed), so that the entire workpiece has an elliptical shape as a front shape. Therefore, after the grinding step, even if the notch formed on the outer peripheral edge of the workpiece disappears, the ellipse shape of the workpiece (for example, the extending direction of its major axis or minor axis) can be used to discriminate the shape of the workpiece. crystal orientation.

Description of drawings

FIG. 1 is a perspective view showing a wafer as an example of a workpiece according to the present embodiment.

FIG. 2 is a cross-sectional view of the wafer shown in FIG. 1 .

FIG. 3 is a perspective view showing a wafer held by a holding table and being trimmed.

Fig. 4 is a perspective view showing the front side of the wafer after the outer peripheral edge removal step.

Fig. 5 is a cross-sectional view showing a wafer whose front side is covered with a front side protection tape.

Fig. 6 is a perspective view showing a grinding device.

Fig. 7 is a sectional view showing a grinding step.

Fig. 8 is a perspective view showing the wafer after the grinding step.

9( a ) and 9 ( b ) are plan views showing other examples of the front surface shape of the wafer after the outer peripheral edge removal step.

Label description

1: wafer; 2a: front side; 2b: back side; 3: planned dividing line; 4: device; 5: device area; 6: peripheral remaining area; 7: outer peripheral edge; 8: outer peripheral cutting part; 9: notch; 101 : Holding table; 103: Cutting tool; 10: Front protection tape; 11: Adhesive layer; 200: Grinding device, conveying/storage section; 201, 202: Table section; 203: Grinding section; 213: Robot Arm; 221: rotary table; 222: chuck table; 231: rough grinding part; 232: fine grinding part; 236: rough grinding abrasive; 237: fine grinding abrasive.

Detailed ways

One embodiment of the present invention will be described in detail using the drawings. First, a to-be-processed object in the method of processing a to-be-processed object (this processing method) according to the present embodiment will be briefly described.

As shown in FIG. 1 , a wafer 1 as an example of a workpiece of the present embodiment is, for example, a silicon substrate having a disk shape. A device region 5 and a peripheral remaining region 6 are formed on the front surface 2 a of the wafer 1 . In the device region 5 , the devices 4 are formed in the respective regions divided by the grid-like dividing lines 3 . The peripheral remaining area 6 surrounds the device area 5 .

As shown in FIG. 2 , the back surface 2 b of the wafer 1 does not have the device 4 and is a surface to be ground which is ground by a grinding wheel or the like. A chamfer is formed on the outer peripheral edge 7 of the wafer 1 in an arc shape from the front surface 2a to the rear surface 2b. In addition, in FIG. 2, the device 4 provided on the front surface 2a of the wafer 1 is omitted.

Furthermore, as shown in FIG. 1 , a notch 9 is provided on the outer peripheral edge 7 of the wafer 1 . The notch 9 is a mark indicating the crystallographic orientation of the wafer 1 . That is, the wafer 1 of the present embodiment includes a semiconductor single crystal. Furthermore, in order to indicate the crystal orientation of the wafer 1 , a notch 9 is provided on the outer peripheral edge 7 of the wafer 1 . The notch 9 is used, for example, as a mark for alignment of the wafer 1 when the wafer 1 is divided into semiconductor chips. The shape of the notch 9 is determined by, for example, the SEMI specification which is an industry standard specification. The notch 9 is, for example, a substantially triangular cutout portion provided on the outer peripheral edge 7 of the wafer 1 and extending toward the center of the wafer 1 .

Next, the steps included in this processing method will be described.

(1) Hold step

In this processing method, first, the wafer 1 is held by the holding table 101 . As shown in FIG. 3 , the back surface 2 b of the wafer 1 is held by a holding table 101 . Thereby, the front surface 2a of the wafer 1 is exposed. At this time, for example, the back surface 2b side of the wafer 1 placed on the holding table 101 is sucked by a suction source (not shown), so that the holding table 101 sucks and holds the wafer 1 .

(2) Outer peripheral edge removal step

After performing the holding step, the rotating cutting tool 103 is cut into the outer peripheral edge 7 of the front surface 2a of the wafer 1, and the holding table 101 is rotated. Thus, the front surface 2 a side of the outer peripheral edge 7 of the wafer 1 is removed (trimmed). That is, edge trimming is performed on the outer peripheral edge 7 of the front surface 2 a of the wafer 1 . The cutting tool 103 used has a flat edge.

In this step, for example, the holding table 101 is arranged below the cutting blade 103, while the cutting blade 103 is rotated in the arrow B direction, the cutting blade 103 is lowered toward the front surface 2a of the wafer 1, and the cutting blade 103 The tip of the blade cuts into the outer periphery 7. Next, the holding table 101 is rotated in the arrow A direction. Then, as the cutting tool 103 descends, the outer peripheral edge 7 is gradually cut. As a result, the outer peripheral edge 7 is edge-trimmed into a ring shape.

Through this outer peripheral edge removing step, as shown in FIG. 4 , a part of the outer peripheral edge 7 of the wafer 1 (on the side of the front surface 2 a ) is removed to form an outer peripheral cut portion 8 . As a result, the notch 9 disappears on the front side 2 a of the wafer 1 .

In particular, in this processing method, in the outer peripheral edge removal step, the outer peripheral edge 7 of the front surface 2a of the wafer 1 is cut (removed) while the cutting blade 103 is oscillated in the radial direction of the wafer 1 . That is, the outer peripheral edge 7 is cut while the cutting blade 103 is moved back and forth in the direction of the rotation axis of the cutting blade 103 to change the cutting width. Thus, as shown in FIG. 4, the front surface 2a of the wafer 1 has an elliptical shape having a major axis (long side) L1 and a minor axis (short side) L2. In addition, for example, in the outer peripheral edge removal step, in order to make the front surface 2a an elliptical shape, the cutting tool 103 is swung twice in the radial direction of the wafer 1 every time the holding table 101 holding the wafer 1 is rotated once. times (two round trips).

In addition, especially in this outer peripheral edge removal step, as shown in FIG. The cutting tool 103 is swung in such a way that the straight lines are parallel to each other to form the elliptical shape of the front surface 2a.

In order to realize such a relationship between the elliptical shape and the position of the notch 9, a processing worker who performs the outer peripheral edge removal step confirms the position of the notch 9 of the wafer 1 in advance. Here, since the notch 9 is a relatively small part, it may be difficult to visually recognize the notch 9 . In this case, the processing worker can confirm the position of the notch 9 without directly visually recognizing the notch 9 . For example, the notches 9 sometimes extend in the arrangement direction of the devices 4 (parallel to the dividing line 3). In this case, the processor can confirm the positions of the notches 9 from the arrangement direction of the devices 4 .

In addition, the device (cutting device) for performing the outer peripheral edge removal step may have a camera system for photographing the notches 9 of the wafer 1 and displaying them to the processing personnel. In this case, the processing worker can carry out the outer peripheral edge removal step while confirming the position of the notch 9 using the display screen of the camera system. In addition, the notch 9 may be detected by pattern matching processing between an image captured by a camera and a prestored image including the notch 9 .

(3) Front protection steps

After performing the peripheral edge removal step, the device region 5 where the device 4 is formed on the front side 2 a of the wafer 1 is covered by a front side protection tape 10 as a front side protection member.

In this step, as shown in FIG. 5 , the front surface protection tape 10 is attached to the front surface 2 a of the wafer 1 . The front side protection tape 10 protects the devices 4 formed on the front side 2 a of the wafer 1 . The front side protection tape 10 has an area covering the entire front side 2 a of the wafer 1 .

When affixing the front protection tape 10 to the wafer 1 , for example, an adhesive is applied to the entire front surface 2 a of the wafer 1 . By affixing the front protection tape 10 with this adhesive, the entire front surface 2 a of the wafer 1 can be covered by the front protection tape 10 . The adhesive includes, for example, a material (paste) having adhesive force to the wafer 1 made of silicon. The front protection tape 10 is in close contact with the wafer 1 while absorbing unevenness generated by the device 4 . As a result, the entire front side 2 a of the wafer 1 is covered by the front side protection tape 10 , thereby protecting the device 4 .

In addition, in the example shown in FIG. 5, the surface protection tape 10 is adhere|attached to the uneven|corrugated produced by the device 4 so that no space may be left. However, the front protection tape 10 may be affixed so as to be in contact with a part of the unevenness.

In addition, in the present embodiment, resin may be used as the front protection member for protecting the device region 5 of the wafer 1 . That is, the front side protection step may include a resin coating step of covering the front side 2 a of the wafer 1 with a resin.

(4) Grinding steps

After performing the front side protection step, the back surface 2b of the wafer 1 is ground with a grinding tool to thin the wafer 1 to a predetermined thickness.

First, the structure of the grinding device used in the grinding step will be described. A grinding apparatus 200 shown in FIG. 6 is an apparatus for performing grinding processing on a wafer 1 . The grinding apparatus 200 has a conveyance/accommodation unit 201 , a table unit 202 , and a grinding unit 203 .

The transfer/storage unit 201 stores the wafer 1 before and after grinding, and transfers the wafer 1 between it and the table unit 202 . The conveying/accommodating part 201 has: the first box 211, which stores the wafer 1 before grinding; the second box 212, which stores the ground wafer 1; the robot arm (transporting part) 213, which transports the wafer 1; a positioning unit 214, which aligns the center of the wafer 1 at a constant position; and a cleaning unit 215, which cleans the wafer 1 after grinding.

The table unit 202 includes a rotary table 221 and three chuck tables (holding tables) 222 provided on the upper surface of the rotary table 221 . The chuck table 222 can revolve on the XY plane by the rotation of the rotary table 221 with the wafer 1 suction-fixed. The rotary table 221 arranges the wafer 1 at a predetermined position of the grinding unit 203 by revolving the chuck table 222 . In addition, the three chuck tables 222 can rotate independently.

The grinding part 203 has a rough grinding part 231 and a finish grinding part 232 . The rough grinding unit 231 has a grinding wheel 235 rotatable together with the rotating shaft 233 . On the bottom surface of the grinding wheel 235, a plurality of rough grinding stones 236 are arranged in a ring shape. The rough grinding tool 236 is a tool used for rough grinding, and contains relatively large abrasive grains, for example. The grinding unit 203 has a grinding feed unit 238 for grinding and feeding the rough grinding unit 231 in the Z-axis direction.

The finish grinding unit 232 performs finish grinding to improve flatness on the wafer 1 that has been thinned to about the finished thickness by rough grinding. The fine grinding part 232 has the structure similar to the rough grinding part 231 except having the finishing grinder 237 instead of the rough grinding grinder 236. As shown in FIG. The fine grinding wheel 237 contains abrasive grains having a smaller particle diameter than the abrasive grains contained in the rough grinding wheel 236 . The grinding part 203 has the grinding feed part 239 which grinds and feeds the finish grinding part 232 to Z-axis direction.

Next, the operation of the grinding apparatus 200 in the grinding step will be described. First, the robot arm 213 takes out the wafer 1 before grinding from the first cassette 211 and places it on the chuck table 222 of the table 202 . At this time, as shown in FIG. 7 , the front surface protection tape 10 of the wafer 1 is sucked and held by the chuck table 222 . Thereby, the back surface 2b of the wafer 1 is exposed upward (Z direction).

Then, rough grinding is performed. That is, by rotating the rotary table 221 shown in FIG. 6 , the chuck table 222 holding the wafer 1 is moved below the rough grinding unit 231 .

Then, as shown in FIG. 7 , the chuck table 222 rotates, for example, in the arrow A direction. In addition, the grinding wheel 235 of the rough grinding unit 231 descends while rotating in the arrow A direction. Then, the rough grinding stone 236 grinds while pressing the back surface 2b of the wafer 1 . In this grinding, the back surface 2 b of the wafer 1 is ground until the remaining outer peripheral edge 7 of the wafer 1 is removed and the rough grinding wheel 236 reaches the outer peripheral cutting portion 8 .

Finish grinding is then carried out. That is, by rotating the rotary table 221 shown in FIG. 6 , the chuck table 222 holding the wafer 1 is moved below the finish grinding unit 232 . The grinding wheel 235 of the fine grinding unit 232 descends while rotating, and the fine grinding wheel 237 performs fine grinding while pressing the back surface 2 b of the wafer 1 . In this finish grinding, the flatness of the back surface 2b is improved so that the entire back surface 2b of the wafer 1 has a substantially uniform thickness. The finish-ground wafer 1 is removed from the chuck table 222 by the robot arm 213 and stored in the second cassette 212 .

As shown in FIG. 8 , since the outer peripheral edge 7 is removed from the wafer 1 in the grinding step, the notch 9 (refer to FIG. 4 ) remaining on the rear surface 2b side of the outer peripheral edge 7 also disappears. In addition, in the grinding step, the back surface 2b of the wafer 1 is ground until it reaches the peripheral cutting portion 8, so the entire wafer 1 has the shape (that is, an elliptical shape) of the front surface 2a before the grinding step.

Then, the wafer 1 is broken along the planned dividing line 3 (see FIG. 1 ) by a known method to form chips as final products (breaking step).

As described above, in the present processing method, in the outer peripheral edge removal step, the cutting blade 103 is oscillated in the radial direction of the wafer 1 (the position of the cutting blade 103 is changed in the radial direction of the wafer 1), while the wafer is The outer peripheral edge 7 of the front face 2a of 1 is cut. That is, the outer peripheral edge 7 is cut while changing the cutting width. Thereby, the outer peripheral edge 7 is removed from the front surface 2a of the wafer 1, and the front surface 2a of the wafer 1 has an elliptical shape. In addition, in this outer peripheral edge removal step, as shown in FIG. The cutting tool 103 is oscillated in a direction parallel to the straight line at the center of the wafer 1). Therefore, the elliptical shape of the front surface 2 a of the wafer 1 is a shape corresponding to the crystal orientation of the wafer 1 .

Then, by the grinding step after the peripheral edge removing step, the peripheral edge 7 of the back surface 2b of the wafer 1 is also ground (removed), so that the entire wafer 1 has an elliptical shape as the shape of the front surface 2a. Therefore, the crystal orientation of the wafer 1 can be discriminated (recognized) from the elliptical shape of the wafer 1 .

In addition, in the present embodiment, the short side L2 of the ellipse shape of the wafer 1 (front surface 2 a ) is along the extending direction of the notch 9 by the outer peripheral edge removal step. However, it is not limited thereto, and the outer peripheral edge removal step may be performed so that the long side L1 of the ellipse shape of the wafer 1 (front side 2 a ) is along the extending direction of the notch 9 . That is, it is only necessary that the elliptical shape of the front surface 2 a of the wafer 1 and the position of the notch 9 have a predetermined relationship. In this case, too, the crystal orientation of the wafer 1 can be discriminated from the elliptical shape of the wafer 1 (front surface 2a).

In addition, in the present embodiment, in the outer peripheral edge removal step, the front surface 2 a of the wafer 1 is formed into an elliptical shape corresponding to the crystal orientation of the wafer 1 . However, the front side 2 a of the wafer 1 may also have other shapes corresponding to the crystallographic orientation of the wafer 1 . For example, as shown in (a) and (b) of FIG. 9 , the front surface 2 a of the wafer 1 may also have a flat shape having drop-shaped protrusions 301 or gentle protrusions 302 . In this structure, the positions and/or shapes of the protrusions 301 and protrusions 302 correspond to the crystallographic orientation of the wafer 1 . In this structure, after the grinding step, the entire wafer 1 has the shape of the protruding portion 301 and the convex portion 302 similarly to the front surface 2 a shown in FIG. 9( a ) and ( b ). Therefore, the crystal orientation of the wafer 1 can be discriminated (recognized) based on the protruding portion 301 or the convex portion 302 .

In addition, in this embodiment, the shape of the front surface 2a of the wafer 1 after the outer peripheral edge removal step (the shape of the wafer 1 after the grinding step) is expressed as an ellipse. The expression of this "ellipse" is of course not limited to the strict ellipse shape having two foci, but includes any shape having symmetry (for example, first-order symmetry or second-order symmetry) in which the crystal orientation of the wafer 1 can be determined.

In addition, in the present embodiment, the wafer 1 is chamfered in an arc shape from the front surface 2a to the rear surface 2b, and the outer peripheral edge 7 is trimmed into a ring shape. However, the outer periphery 7 to be trimmed is not only formed by chamfering. For example, when the outer peripheral edge 7 of the wafer 1 has a level difference, it is also preferable to trim the outer peripheral edge 7 .

Claims (1)

1. A method for processing a workpiece having a front surface on which devices are formed in regions defined by a plurality of planned dividing lines formed in a lattice shape, the method comprising:

a holding step of holding the back surface of the workpiece by a holding table so that the front surface of the workpiece is exposed;

an outer peripheral edge removing step of cutting the outer peripheral edge of the workpiece while changing a cutting width by causing a cutting tool to cut into the outer peripheral edge of the front surface of the workpiece and rotating the holding table while swinging the cutting tool in a radial direction of the workpiece after the holding step is performed;

a front surface protecting step of covering a region of the front surface of the workpiece, in which the device is formed, with a front surface protecting member after the peripheral edge removing step is performed; and

a grinding step of grinding the back surface of the workpiece with a grinding wheel to reduce the thickness of the workpiece to a predetermined thickness after the front surface protection step is performed,

in the outer peripheral edge removing step, the outer peripheral edge of the front surface of the workpiece is cut while changing the cutting width, and the outer peripheral edge is removed so that the front surface of the workpiece has an elliptical shape corresponding to the crystal orientation of the workpiece, whereby the crystal orientation of the workpiece can be identified by the elliptical shape.

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