JP7680909B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method.

The wafer, on the surface of which multiple devices such as ICs and LSIs are formed and partitioned along planned dividing lines, has its back surface ground by a grinding device to form it to the desired thickness, and is then divided into individual device chips by a cutting device. Each divided device chip is then used in electrical equipment such as mobile phones and personal computers.

At the desired position on the wafer (for example, in the peripheral excess area adjacent to the orientation flat), a barcode, product number, product name, lot number, or other characters including an ID mark are marked to manage the wafer. The ID mark is checked at each manufacturing process to perform the desired processing on the wafer, while past information is passed on to ensure traceability (for example, see Patent Document 1).

Japanese Patent Application Publication No. 8-330196

However, when a wafer is divided into individual device chips, there is a problem that past information cannot be transferred for each device chip, and traceability cannot be ensured.

In view of the above, the objective of the present invention is to provide a wafer processing method that allows the transfer of past information for each device chip and ensures traceability for each device chip.

According to the present invention, the following wafer processing method is provided to solve the above problems. That is, the wafer processing method includes a cutting device preparation step of preparing a cutting device including at least a rotatable chuck table that holds a wafer, cutting means having a rotatable cutting blade that cuts the wafer held on the chuck table, an X-axis feed means that feeds the chuck table and the cutting means relatively in the X-axis direction, a Y-axis feed means that indexes and feeds the chuck table and the cutting means relatively in the Y-axis direction perpendicular to the X-axis direction, a Z-axis feed means that feeds the chuck table and the cutting means relatively in the Z-axis direction perpendicular to the X-axis and Y-axis directions, an imaging means that images the wafer held on the chuck table, a display means that displays an image captured by the imaging means, and a control means; The wafer processing method includes an information registration step of registering information to be marked in the control means, a holding step of holding the front side of a wafer having a surface divided by a planned dividing line on the chuck table and exposing the back side of the wafer, a position registration step of imaging the wafer held on the chuck table with the imaging means, specifying the position of each device to be marked in terms of X and Y coordinates, and registering the position in the control means, and a marking step of operating the X-axis feed means and the Y-axis feed means based on the X-axis and Y coordinates registered in the position registration step to position the cutting blade at a desired position and operate the Z-axis feed means, and marking the information registered in the information registration step on the back side of each device with the cutting blade.

The marking step is preferably carried out before dividing the wafer into individual device chips. It is desirable to carry out a surface protection member disposing step of disposing a protection member on the surface of the wafer before the holding step.

It is preferable that the method includes a wafer supporting step in which a dicing tape is applied to the back surface of the wafer and the wafer is supported via the dicing tape by a frame having an opening for accommodating the wafer, and a dividing step in which the protective member is peeled off from the front surface of the wafer to divide the wafer into individual device chips.

It is convenient to carry out the marking step after dividing the wafer into individual device chips. It is preferable to include a retaining member disposing step, prior to the holding step, of disposing a retaining member that maintains the shape of the wafer on the surface of the wafer divided into individual device chips.

The wafer processing method of the present invention includes a cutting device preparation step of preparing a cutting device including at least a rotatable chuck table for holding a wafer, cutting means having a rotatable cutting blade for cutting the wafer held on the chuck table, an X-axis feed means for relatively feeding the chuck table and the cutting means in the X-axis direction, a Y-axis feed means for relatively indexing and feeding the chuck table and the cutting means in the Y-axis direction perpendicular to the X-axis direction, a Z-axis feed means for relatively cutting the chuck table and the cutting means in the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction, an imaging means for imaging the wafer held on the chuck table, a display means for displaying an image captured by the imaging means, and a control means, and a step of registering information to be marked in the control means. The method includes an information registration step, a holding step in which the front side of a wafer having a surface divided by planned dividing lines and a plurality of devices is held on the chuck table and the back side of the wafer is exposed, a position registration step in which the wafer held on the chuck table is imaged by the imaging means to identify the position of each device to be marked in terms of X and Y coordinates and registered in the control means, and a marking step in which the X-axis feed means and the Y-axis feed means are operated based on the X-axis and Y coordinates registered in the position registration step to position the cutting blade at a desired position and the Z-axis feed means is operated to mark the information registered in the information registration step on the back side of each device with the cutting blade. This makes it possible to transfer past information for each device chip and ensures traceability for each device chip.

FIG. FIG. 13 is a perspective view showing a state in which a surface protection member disposing step is being carried out. FIG. 2A is a perspective view showing a state in which a wafer is positioned above a chuck table, and FIG. 2B is a perspective view showing a state in which the wafer is held by the chuck table. FIG. 13 is a perspective view showing a state in which a position registration process is being performed. FIG. 2A is a perspective view showing a state in which a marking process is being performed, and FIG. 2B is a partial plan view of the back surface side of the wafer on which marking has been performed. FIG. 13 is a perspective view showing a state in which a wafer supporting step is being performed. FIG. FIG. 2 is a perspective view of a wafer divided into device chips.

Below, a preferred embodiment of the wafer processing method of the present invention will be described with reference to the drawings.

(Cutting device preparation process)
In the illustrated embodiment, a cutting device preparation step is first performed to prepare a required cutting device. The cutting device prepared in this step may be, for example, the cutting device 2 shown in FIG.

The cutting device 2 includes at least a rotatable chuck table 4 that holds a wafer, a cutting means 6 that has a rotatable cutting blade that cuts the wafer held on the chuck table 4, an X-axis feed means (not shown) that feeds the chuck table 4 and the cutting means 6 relatively in the X-axis direction, a Y-axis feed means (not shown) that indexes and feeds the chuck table 4 and the cutting means 6 relatively in the Y-axis direction perpendicular to the X-axis direction, a Z-axis feed means (not shown) that feeds the chuck table 4 and the cutting means 6 relatively in the Z-axis direction perpendicular to the X-axis and Y-axis directions, an imaging means 8 that images the wafer held on the chuck table 4, a display means 10 that displays the image captured by the imaging means 8, and a control means 12. The X, Y, and Z axis directions are respectively indicated by the arrows X, Y, and Z in FIG. 1. The XY plane defined by the X-axis and Y-axis directions is substantially horizontal, and the Z-axis direction is the up-down direction.

The chuck table 4 is configured to be movable in the X-axis direction and rotatable about the Z-axis direction. A porous circular suction chuck 14 connected to a suction means (not shown) is disposed at the upper end of the chuck table 4. The chuck table 4 suction-holds the wafer placed on the upper surface of the suction chuck 14 by generating a suction force on the upper surface of the suction chuck 14 using the suction means. In addition, a number of clamps 16 are disposed around the periphery of the chuck table 4 at intervals in the circumferential direction.

Referring to Figures 1 and 5, the cutting means 6 includes a spindle housing 18 (see Figure 5) that is movable in both the Y-axis and Z-axis directions, a spindle 20 that is rotatably supported by the spindle housing 18, an annular cutting blade 22 fixed to the tip of the spindle 20, and a motor (not shown) that rotates the spindle 20.

The X-axis feed means has a ball screw that is connected to the chuck table 4 and extends in the X-axis direction, and a motor that rotates the ball screw. The X-axis feed means converts the rotational motion of the motor into linear motion using the ball screw and transmits it to the chuck table 4, feeding the chuck table 4 in the X-axis direction for machining relative to the cutting means 6.

The Y-axis feed means includes a ball screw that is connected to the spindle housing 18 of the cutting means 6 and extends in the Y-axis direction, and a motor that rotates the ball screw. The Y-axis feed means converts the rotational motion of the motor into linear motion using the ball screw and transmits it to the spindle housing 18, indexing and feeding the cutting means 6 in the Y-axis direction relative to the chuck table 4.

The Z-axis feed means includes a ball screw that is connected to the spindle housing 18 and extends in the Z-axis direction, and a motor that rotates the ball screw. In the Z-axis feed means, the ball screw converts the rotational motion of the motor into linear motion and transmits it to the spindle housing 18, so that the cutting means 6 is fed in the Z-axis direction to cut into the chuck table 4.

The imaging means 8 is disposed above the orbit of the chuck table 4. The imaging means 8 includes a normal imaging element (CCD) that images the wafer with visible light, an infrared irradiating means that irradiates the wafer with infrared light, an optical system that captures the infrared light irradiated by the infrared irradiating means, and an imaging element (infrared CCD) that outputs an electrical signal corresponding to the infrared light captured by the optical system (none of which are shown). The image captured by the imaging means 8 is sent to the display means 10 and the control means 12.

The control means 12 is composed of a computer having a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program, etc., and a readable/writable random access memory (RAM) that stores the calculation results, etc.

The cutting device 2 further includes a cassette table 26 that can be raised and lowered and on which a cassette 24 containing a plurality of wafers is placed, a transfer means 30 that pulls out unprocessed wafers from the cassette 24 and transfers them to the temporary placement table 28 and transfers processed wafers positioned on the temporary placement table 28 into the cassette 24, a first transfer means 32 that transfers the unprocessed wafers transferred from the cassette 24 to the temporary placement table 28 to the chuck table 4, a cleaning means 34 that cleans the processed wafers, and a second transfer means 36 that transfers the processed wafers from the chuck table 4 to the cleaning means 34.

(Information registration process)
After the cutting device preparation step is performed, an information registration step is performed in which information to be marked is registered in the control means 12. The information to be marked is information for identifying each of a plurality of devices formed on the wafer.

(Surface protection member disposing process)
In the illustrated embodiment, after the information registration step is performed, a surface protection member providing step is performed in which a protection member is provided on the surface of the wafer.

Figure 2 shows a wafer 38 that can be processed by the wafer processing method of this embodiment. The wafer 38 is disk-shaped and can be made of an appropriate semiconductor material such as silicon. The surface 38a of the wafer 38 is partitioned into a plurality of rectangular regions by lattice-shaped division lines 40, and devices 42 such as ICs and LSIs are formed in each of the rectangular regions. In addition, a notch 44 indicating the crystal orientation is formed on the periphery of the wafer 38.

In the surface protection member disposition process, as shown in FIG. 2, a circular protection member 46 having a diameter substantially equal to that of the wafer 38 is disposed on the surface 38a of the wafer 38. The protection member 46 may have an adhesive layer, in which case this process can be carried out by attaching the protection member 46 to the surface 38a of the wafer 38. Note that if a thermocompression sheet such as polyolefin is used as the protection member 46, no adhesive layer is required.

(holding process)
After the surface protection member arrangement process is performed, a holding process is performed in which the front surface 38a side of a wafer 38 having a surface 38a partitioned by planned division lines 40 into which a plurality of devices 42 are formed is held on a chuck table 4, and the back surface 38b side of the wafer 38 is exposed.

As shown in FIG. 3, in the holding process, first, the wafer 38 is placed on the upper surface of the chuck table 4 with the surface 38a of the wafer 38 facing downward. Next, the suction means connected to the suction chuck 14 is operated to generate a suction force on the upper surface of the suction chuck 14, and the wafer 38 is suction-held on the upper surface of the suction chuck 14.

(Location registration process)
After the holding step is performed, a position registration step is performed in which the wafer 38 held on the chuck table 4 is imaged by the imaging means 8, and the position of each device 42 to be marked is identified by X and Y coordinates and registered in the control means 12.

In the position registration process, first, the chuck table 4 is moved by the X-axis feed means, and the wafer 38 is positioned below the imaging means 8. Next, the wafer 38 held on the chuck table 4 is imaged by the imaging means 8. Next, based on the image of the wafer 38 captured by the imaging means 8, the planned division line 40 is aligned in the X-axis direction.

At this time, the back surface 38b of the wafer 38 faces upward, and the front surface 38a on which the planned division lines 40 are formed faces downward. However, as described above, the imaging means 8 includes an infrared irradiation means, an optical system that captures infrared rays, and an imaging element (infrared CCD) that outputs an electrical signal corresponding to the infrared rays, so that the planned division lines 40 on the front surface 38a can be imaged through the back surface 38b of the wafer 38.

Next, the position of each device 42 to be marked is specified by X and Y coordinates. In this case, for example, as shown in Fig. 4, the position of the device 42 can be specified by detecting the X and Y coordinates of each intersection of the center lines L of the planned division lines 40. Specifically, the position of the device 42a to be marked can be specified by detecting the coordinates of four intersections ( _X3 , _Y3 ), ( _X3 , _Y4 ), ( _X4 , _Y3 ), and ( _X4 , _Y4 ) around the device 42a. In this way, the positions of all the devices 42 are specified by X and Y coordinates.

In addition, in the position registration process, the position of the device 42 may be identified by detecting the X and Y coordinates of a characteristic pattern (key pattern) on the device 42, instead of the intersection coordinates around the device 42. The origin of the X and Y coordinates can be set arbitrarily. For example, the origin of the X and Y coordinates can be set to the notch 44.

(Marking process)
After the position registration process is performed, the X-axis feed means and the Y-axis feed means are operated based on the X-coordinates and Y-coordinates registered in the position registration process to position the cutting blade 22 at the desired position, and the Z-axis feed means is operated to perform a marking process in which the information registered in the information registration process is marked on the back surface of each device 42 with the cutting blade 22.

In the marking process, first, the chuck table 4 is moved by the X-axis feed means, and the wafer 38 is positioned below the cutting means 6. Next, based on the X- and Y-coordinates registered in the position registration process, the X- and Y-axis feed means are operated, and the cutting blade 22 is positioned above the device 42 to be marked.

Next, the spindle housing 18 is lowered by the Z-axis feed means, and the cutting edge of the cutting blade 22, which is rotating at high speed, cuts into the wafer 38 from the back surface 38b to the front surface 38a, while supplying cutting water to the area where the cutting edge of the cutting blade 22 is to cut. Then, as shown in FIG. 5, the X-, Y-, and Z-axis feed means are operated appropriately to repeatedly cut the cutting edge of the cutting blade 22 into the back surface 38b of the wafer 38, forming a marking 48, which may be in the form of a barcode, on the back surface of the device 42.

After marking 48 has been formed on one device 42, marking 48 is repeated while moving chuck table 4 in the X-axis direction by the distance between planned division lines 40 in the X-axis direction. After marking 48 has been formed on all devices 42 in one row, chuck table 4 is moved in the Y-axis direction by the distance between planned division lines 40 in the Y-axis direction, and marking 48 is formed on the next row of devices 42. In this manner, marking 48 is formed on all devices 42 on wafer 38.

(Wafer support process)
In the illustrated embodiment, after the marking step is performed, a wafer supporting step is performed in which a dicing tape 50 is attached to the back surface 38b of the wafer 38 and the wafer 38 is supported via the dicing tape 50 by a frame 52 having an opening 52a for accommodating the wafer 38, as shown in Fig. 6. Note that the wafer supporting step is performed after the suction force of the chuck table 4 is released and the wafer 38 is carried out from the chuck table 4.

(Dividing process)
After the wafer supporting step is performed, a dividing step is performed in which the protective member 46 is peeled off from the front surface 38a of the wafer 38 and the wafer 38 is divided into individual device chips.

In the division process, first, as shown in FIG. 6, the protective member 46 is peeled off from the surface 38a of the wafer 38. Next, the wafer 38 is suction-held on the upper surface of the chuck table 4 with the surface 38a of the wafer 38 facing upward. The frame 52 is fixed by the clamps 16 of the chuck table 4. Next, the wafer 38 is imaged by the imaging means 8, and based on the image of the wafer 38 imaged by the imaging means 8, the planned division lines 40 are aligned in the X-axis direction, and the area corresponding to the planned division lines 40 aligned in the X-axis direction is positioned below the cutting blade 22.

Next, as shown in FIG. 7, the cutting edge of the cutting blade 22 rotated at high speed is cut from the front surface 38a to the back surface 38b, and cutting water is supplied to the portion where the cutting edge of the cutting blade 22 is to be cut. At the same time, the chuck table 4 (omitted in FIG. 7) is moved in the X-axis direction relative to the cutting means 6, thereby forming a dividing groove 54 along the intended dividing line 40.

Then, the cutting blade 22 is indexed and fed in the Y-axis direction relative to the chuck table 4 by an amount equal to the spacing of the planned division lines 40 in the Y-axis direction, while repeatedly forming the division grooves 54, to form the division grooves 54 along all of the planned division lines 40 aligned in the X-axis direction. The chuck table 4 is then rotated 90 degrees, and the cutting blade 22 is indexed and fed, while repeatedly forming the division grooves 54, to form the division grooves 54 along all of the planned division lines 40 that are perpendicular to the planned division lines 40 along which the division grooves 54 were previously formed. In this way, the wafer 38 is divided into individual device chips, as shown in FIG. 8.

As described above, in the illustrated embodiment, the markings 48 are formed for each device 42 by cutting, so that past information can be transferred for each device chip, and traceability for each device chip is ensured.

In the illustrated embodiment, an example is described in which the marking process is performed before dividing the wafer 38 into individual device chips, but the marking process may be performed after dividing the wafer 38 into individual device chips.

When the marking process is carried out after division, it is preferable to carry out the wafer supporting process and the dividing process, and then carry out a maintaining member disposing process in which a maintaining member (for example, a circular adhesive tape similar to the protective member 46) that maintains the shape of the wafer 38 is disposed on the surface 38a of the wafer 38 divided into individual device chips, and then peel the wafer 38 from the dicing tape 50, and then carry out the holding process, position registration process, and marking process.

2: Cutting device 4: Chuck table 6: Cutting means 8: Imaging means 10: Display means 12: Control means 22: Cutting blade 38: Wafer 38a: Front surface of wafer 38b: Back surface of wafer 40: Planned division line 42: Device 46: Protective member 48: Marking 50: Dicing tape 52: Frame 52a: Opening of frame

Claims (6)

A method for processing a wafer, comprising the steps of:
a cutting device preparation step of preparing a cutting device including at least a rotatable chuck table for holding a wafer, cutting means having a rotatable cutting blade for cutting the wafer held on the chuck table, X-axis feed means for relatively feeding the chuck table and the cutting means in an X-axis direction, Y-axis feed means for relatively indexing and feeding the chuck table and the cutting means in a Y-axis direction perpendicular to the X-axis direction, Z-axis feed means for relatively cutting the chuck table and the cutting means in a Z-axis direction perpendicular to the X-axis and Y-axis directions, imaging means for imaging the wafer held on the chuck table, display means for displaying an image captured by the imaging means, and control means;
an information registration step of registering information to be marked in the control means;
a holding step of holding a front side of a wafer having a surface divided by dividing lines into a plurality of devices on the chuck table and exposing a back side of the wafer;
a position registration step of imaging the wafer held on the chuck table with the imaging means, specifying the position of each device to be marked in terms of X and Y coordinates, and registering the specified position in the control means;
a marking step of operating the X-axis feed means and the Y-axis feed means to position the cutting blade at a desired position based on the X- and Y-coordinates registered in the position registration step and operating the Z-axis feed means to mark the information registered in the information registration step on the back surface of each device with the cutting blade;
A method for processing a wafer comprising the steps of: The method for processing a wafer according to claim 1, in which the marking step is carried out before dividing the wafer into individual device chips. The wafer processing method according to claim 1, further comprising a surface protection member disposing step of disposing a protection member on the surface of the wafer prior to the holding step. The wafer processing method of claim 3, comprising a wafer supporting step of adhering a dicing tape to the back surface of the wafer and supporting the wafer via the dicing tape with a frame having an opening for accommodating the wafer, and a dividing step of peeling off the protective member from the front surface of the wafer and dividing the wafer into individual device chips. The wafer processing method according to claim 1, in which the marking step is carried out after dividing the wafer into individual device chips. The wafer processing method according to claim 5, further comprising a step of providing a support member for maintaining the shape of the wafer on the surface of the wafer divided into individual device chips prior to the holding step.

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