JP2022180733A - Wafer processing method - Google Patents

Abstract

To provide a wafer processing method of grinding a front surface of a wafer in which a post region and an outer peripheral residual region surrounding the post region are formed, to grind the height of a post to a desired height.SOLUTION: A processing method by a grinding deice 1 includes the steps of: holding another surface of a wafer on a chick table 32; detecting a height position of the front surface of an outer peripheral residual region of the held wafer with a laser displacement gauge 5; rotating the chuck table, and making grinding means 4 comprising a grinding wheel 425 in which a grinding grinder 426 is annularly distributed approach the wafer held on the chuck table to grind a post region of the wafer so that the grinding grinder passes through a rotational center of the wafer; and detecting the height position of the post to be ground in the post region when executing the grinding step, and terminating the grinding step in the case where a difference between the height position of the post and the height position of the outer peripheral residual region becomes a predetermined value.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method of processing a wafer having, on one surface thereof, a post region having a plurality of fine posts formed thereon and an outer peripheral surplus region surrounding the post region.

A wafer having a plurality of devices such as ICs, LSIs, etc. formed on the front surface partitioned by division lines is ground by a grinding machine to form a desired thickness on the rear surface thereof, and then divided into individual device chips by a dicing machine. , cell phones, and personal computers.

The grinding apparatus includes a chuck table holding a wafer, a grinding means having a rotatable grinding wheel on which grinding wheels for grinding the wafer held on the chuck table are arranged in an annular shape, and feeding the grinding means for grinding. At least a grinding feeding means and a measuring means for measuring the thickness of the wafer are provided, and the wafer can be processed to have a desired thickness (see Patent Document 1, for example).

JP 2009-246098 A

By the way, the surface of a wafer having a post region in which a plurality of fine posts are formed and an outer peripheral surplus region surrounding the post region are formed on one side is ground to obtain a desired height of the posts. In some cases, it is required to perform very precise grinding, and there is a problem that a method for realizing such processing has not yet been specifically established and is difficult to implement.

The present invention has been made in view of the above facts, and its main technical problem is that a post region in which a plurality of fine posts are formed and an outer peripheral surplus region surrounding the post region are formed on one surface. To provide a wafer processing method capable of grinding the surface of a wafer and accurately grinding the height of the post to a desired height.

In order to solve the above main technical problem, according to the present invention, there is provided a method of processing a wafer having a post region in which a plurality of fine posts are formed and an outer peripheral surplus region surrounding the post region are formed on one surface. a holding step of holding the other surface of the wafer on a chuck table; and an outer peripheral height detecting step of detecting the height position of the surface of the outer peripheral surplus region of the wafer held on the chuck table with a laser displacement meter. rotating the chuck table and bringing a grinding means having a rotatable grinding wheel on which a grinding wheel is arranged in a ring to approach the wafer held on the chuck table, so that the grinding wheel passes through the center of rotation of the wafer; a grinding step of grinding the post region of the wafer such that the post region of the wafer is ground so that the height of the post is detected by a laser displacement meter during the grinding step; a grinding termination step of terminating the grinding step when the difference between the height position and the height position of the surface of the outer peripheral surplus region reaches a predetermined value.

It is preferable to detect at least one of post breakage and chipping in the grinding termination step.

A method of processing a wafer according to the present invention is a method of processing a wafer in which a post region in which a plurality of fine posts are formed and an outer peripheral surplus region surrounding the post region are formed on one surface of the wafer. a holding step of holding the other surface on a chuck table; an outer peripheral height detecting step of detecting a surface height position of an outer peripheral surplus region of the wafer held on the chuck table with a laser displacement meter; and rotating the chuck table. At the same time, a grinding means having a rotatable grinding wheel on which a grinding wheel is arranged is brought close to the wafer held on the chuck table, and the post of the wafer is moved so that the grinding wheel passes through the center of rotation of the wafer. a grinding step of grinding an area; and a height position of the post ground in the post area during the grinding process is detected by a laser displacement meter, and the height position of the post and the outer peripheral surplus are detected. and a grinding termination step of terminating the grinding step when the difference from the height position of the surface of the region reaches a predetermined value. It is possible to solve the problem that it is difficult to grind the height of the post to a desired height when grinding a wafer having an outer peripheral surplus region surrounding the post region formed on one side thereof.

1 is an overall perspective view of a grinding apparatus suitable for the wafer processing method of the present embodiment; FIG. (a) A block diagram showing an outline of a laser displacement meter arranged in the grinding apparatus shown in FIG. 1, (b) A conceptual diagram of laser light decomposed so that the focal position differs for each wavelength in the vertical direction. . (a) A perspective view showing an embodiment of a holding step, and (b) a cross-sectional view taken along the line AA of (a). It is a perspective view which shows the embodiment of an outer periphery height detection process. It is a perspective view which shows the embodiment of a grinding process and a grinding completion process. FIG. 5 is a graph based on data showing changes in post height as a function of the grinding process; FIG. FIG. 4 is a perspective view of a wafer after a grinding finishing step; It is a graph based on the data in which bending and chipping of the post are detected in the finishing process of grinding.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wafer processing method based on the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows an overall perspective view of a grinding apparatus 1 suitable for carrying out this embodiment. The grinding apparatus 1 shown in FIG. 1 includes holding means 3 having a chuck table 32 for sucking and holding a plate-shaped workpiece, and grinding means as processing means for grinding the workpiece sucked and held by the chuck table 32. 4, a laser displacement meter 5 for detecting the height position of the surface of the workpiece, and a control means 100 for controlling each operating part. The workpiece in this embodiment is the wafer 10 shown in FIG. 3(a), and the details will be described later.

The grinding device 1 shown in FIG. 1 comprises a device housing 2 . The device housing 2 has a substantially rectangular parallelepiped body portion 21 and an upright wall 22 provided at the rear end portion of the body portion 21 and erected in the vertical direction. The holding means 3 is arranged in the body portion 21, and bellows means 6a and 6b are arranged on both sides of the holding means 3 in the X-axis direction indicated by the arrow X. As shown in FIG. A moving means (not shown) for moving the chuck table 32 of the holding means 3 in the X-axis direction is accommodated inside the body portion 21 . By operating the moving means, the bellows means 6a and 6b are extended and contracted, and the unprocessed wafer 10 is placed on the chuck table 32 on the front side of the drawing. can be moved to and from the processing area on the back side in the drawing where processing is performed in . In FIG. 1, the control means 100 is shown outside the grinding machine 1 for convenience of explanation, but it is actually accommodated inside the machine housing 2. As shown in FIG.

The grinding means 4 are arranged on the front face of the upright wall 22 . The grinding means 4 includes a movable base 41 and a spindle unit 42 mounted on the movable base 41 . The movable base 41 engages with a pair of guide rails 221, 221 arranged on the upright wall 22 of the device housing 2 on the rear side, and moves in the Z-axis direction (vertical direction) with respect to the guide rails 221, 221. It is slidably mounted.

The spindle unit 42 includes a spindle housing 421 supported by a support portion 413 formed integrally with the moving base 41, a rotating spindle 422 rotatably held by the spindle housing 421, and a rotating spindle 422 for rotating. and a servomotor 423 arranged as a rotary drive means. A lower end portion of the rotary spindle 422 protrudes downward from the spindle housing 421, and a wheel mount 424 is provided at the lower end. A grinding wheel 425 is attached to the lower surface of the wheel mount 424, and a plurality of grinding wheels 426 are annularly arranged on the lower surface of the grinding wheel 425 (see also FIG. 5). For the grinding wheel 426 of this embodiment, the roughness and material suitable for grinding the posts 12 (see FIG. 3) formed on the surface 10a of the wafer 10, which will be described later, are selected. A vitrified wheel is selected.

The grinding apparatus 1 shown in FIG. 1 includes grinding feed means 7 for vertically moving the grinding means 4 along the pair of guide rails 221 , 221 . The grinding feeding means 7 has a male threaded rod 71 arranged on the front side of the upright wall 22 and extending in the vertical direction. The male threaded rod 71 is rotatably supported by the upright wall 22 at its upper and lower ends. A pulse motor 72 as a drive source for rotationally driving the male threaded rod 71 is provided at the upper end of the male threaded rod 71 , and the output shaft of the pulse motor 72 is connected to the male threaded rod 71 . A screw connecting portion (not shown) is formed on the rear surface of the movable base 41, and a female threaded hole extending in the vertical direction is formed in the connecting portion, and the male threaded rod 71 is screwed into the female threaded hole. Let me. Such a grinding feed means 7 can rotate the pulse motor 72 forward to lower the grinding means 4 together with the movable base 41 , and can rotate the pulse motor 74 in the reverse direction to raise the grinding means 4 together with the movable base 41 . .

As shown in FIG. 1, the laser displacement gauge 5 is arranged on the main body 21 of the device housing 2 at a position close to the area where the chuck table 32 moves in the X-axis direction in the Y-axis direction. is disposed on a side wall portion 23 formed along the . The laser displacement gauge 5 is driven by a moving means (not shown) disposed inside the side wall portion 23, and is driven by a sliding groove 231 of the side wall portion 23 formed along the direction indicated by X1 in the figure. configured to be movable along the

The function of the laser displacement meter 5 will be described more specifically with reference to FIG. 1 and a block diagram showing an outline of the laser displacement meter 5 shown in FIG. The laser displacement meter 5 includes a detection unit 51, a light source 52 arranged in the detection unit 51, a beam splitter 53 for transmitting a part of the laser light L0 emitted from the light source 52, and a beam splitter 53 for transmitting the laser light L0. A projection lens 54 (for example, a chromatic aberration lens) that separates the laser beam L0 into laser beams (L1 to L2) of different wavelengths to generate converging points in the vertical direction, and a workpiece (wafer 10 in the figure) and a convex lens 55A for condensing the laser beam that has been reflected by the surface 10a of the workpiece and reflected by the beam splitter 53 to be split. A pinhole mask 56 having a pinhole 56a that allows only the laser beams of matching wavelengths (part of L1 to L2 in the figure) to pass through, and a convex lens that arranges the laser beams that have passed through the pinholes 56a into substantially parallel beams. 55B, a diffraction grating 57 that reflects the laser light emitted from the convex lens 55B in different directions for each wavelength, and the laser light reflected by the diffraction grating 57 is received, and the wavelength of the received laser light is received according to the received position. and a wavelength detector 58 including a high-resolution photodetector for identifying the wavelength detector 58 , which is connected to the control means 100 .

The detection unit 51 is formed with an air flow path 51a that communicates in the vertical direction, and high-pressure (eg, 0.5 Mpa) air 50 is introduced into the air flow path 51a from an air supply source (not shown), The high-pressure air 50 introduced into the air flow path 51a is jetted from the laser irradiation port 51b at the lower end of the detection unit 51 toward the measurement section immediately below at a flow rate of, for example, 160 L/min. When detecting the height position of the surface of the workpiece using the laser displacement meter 5, the jet of the high-pressure air 50 adheres to the surface of the workpiece positioned directly below the detection unit 51. Dust, machining fluid, etc. are blown away, and the height position of the surface of the workpiece can be detected with high accuracy.

The laser light L0 emitted from the light source 52 of the present embodiment is, for example, white light, and includes not only visible light wavelengths but also a wide range of wavelengths from 350 nm to 1400 nm. A light source is selected that emits light with a stable intensity in the wavelength band. The laser beam emitted from the laser irradiation port 51b of the detection unit 51 described above is decomposed so that the focal position differs for each wavelength in the vertical direction, as shown in the conceptual diagram of FIG. 2(b). In this embodiment, the laser light L1 with a wavelength of 350 nm to the laser light L2 with a wavelength of 1400 nm are resolved, and a focal position is formed over 7 mm (7000 μm) in the vertical direction. With such a configuration, if the surface 10a of the wafer 10 is at the position Z1 indicated by the solid line in FIG. , light with a wavelength of 350 nm is mainly reflected from the surface 10a of the wafer 10, and when the surface 10a' of the wafer 10' is at the lower position Z2 indicated by the dashed line in FIG. The light with a wavelength of 1400 nm is mainly reflected from the surface 10a' of the wafer 10', coinciding with the focal position of the light L2 (wavelength of 1400 nm). Further, when the surface 10a of the wafer 10 is at any position between the above positions Z1 and Z2, the laser light of any wavelength between 350 nm and 1400 nm corresponding to that position is mainly reflected. Since the pinhole mask 56 having the pinholes 56a described above is arranged, only the mainly reflected wavelength is efficiently guided to the diffraction grating 57, so that the wavelength of the light receiving element in the wavelength detector 58 can be detected. The corresponding position is irradiated with laser light, and the wavelength of the laser light mainly reflected by the workpiece is specified with high accuracy.

A wavelength signal having a wavelength specified and output by the wavelength detector 58 is transmitted to the control means 100, and based on the wavelength, a table T stored in advance in the control means 100 is detected by a matching section 110 configured in the control means 100. is matched with As shown on the right side of FIG. 2(a), the table T specifies the wavelength of the light detected by the wavelength detector 58 in the range of 350 nm to 1400 nm. It is possible to specify the height position with the focus position as the reference (0 mm). Since the wavelength detector 58 of this embodiment is composed of a high-resolution light-receiving element, the height position of the surface of the workpiece can be determined in units of 0.5 μm by checking with the table T described above. It is possible to specify exactly. In addition to the collation unit 110, the control means 100 is also provided with a grinding end determination unit 120 for executing the grinding end process. explain.

The grinding apparatus 1 suitable for the present embodiment generally has the configuration described above, and a wafer processing method performed using the above-described grinding apparatus 1 will be described below.

As shown in FIG. 3A, the workpiece in this embodiment is, for example, a circular silicon substrate wafer 10 having a diameter of 150 mm. A post area 14 in which a plurality of fine posts 12 made of nickel are formed, and an annular outer peripheral surplus area 16 surrounding the post area 14 are formed on the central side. The diameter of the post area 14 is, for example, 138 mm, and the width of the peripheral surplus area 16 is 6 mm. The post 12 has a substantially cylindrical shape, as shown in FIG. is 0.5 mm, and the height before grinding is 80 μm. As can be understood from FIG. 3B showing the AA cross section of FIG. In this embodiment, the post 12 is ground to a desired height (25 μm). The other surface (back surface 10b) of the wafer 10 does not have the posts 12 and is a flat surface. Also, the dashed line 11 that separates the post region 14 and the peripheral surplus region 16 described on the surface 10a of the wafer 10 shown in FIG. It is not what is being done.

When carrying out the wafer processing method of this embodiment, as shown in FIG. The wafer 10 is held by suction on the table 32 (holding step).

Next, the above-described moving means is operated to move the chuck table 32 in the X-axis direction so that the peripheral surplus area 16 of the wafer 10 is positioned directly below the detection unit 51 of the laser displacement meter 5 as shown in FIG. As described above, since the laser displacement meter 5 can be moved in the X-axis direction in the main body 21 of the apparatus housing 2, the chuck table 32 was moved to the processing area directly below the grinding means 4. In addition, the position of the laser displacement gauge 5 can be finely adjusted so that the peripheral surplus region 16 of the wafer 10 is positioned directly below the detection unit 51 of the laser displacement gauge 5 . Next, the laser displacement meter 5 is operated, high-pressure air 50 is jetted from the laser irradiation port 51b of the detection unit 51, laser light L0 is irradiated from the light source 52, and the outer peripheral surplus of the wafer 10 held on the chuck table 32 is The wavelength λ1 of the laser light reflected by the surface 10a of the region 16 is detected. In this embodiment, the laser displacement meter 5 is operated so that the surface 10a of the wafer 10 is positioned between the focal position of the laser beam L1 having a wavelength of 350 nm and the focal position of the laser beam L2 having a wavelength of 1400 nm. The position of the detection unit 51 is adjusted in advance, and the wavelength λ1 is detected at a substantially intermediate position between 350 nm and 1400 nm. Further, when detecting the height position of the surface 10a of the peripheral surplus region 16, the chuck table 32 is rotated in the direction indicated by the arrow R1 in FIG. The average value may be calculated as the wavelength λ1.

Here, the wavelength λ1 (for example, 735.1 nm) detected by the wavelength detector 58 as described above is transmitted to the collation unit 110 of the control means 100, and the wavelength λ1 is collated with the table T to obtain the outer circumference surplus. It is detected that the height position of the surface of the region 16 is Z3 (for example, 3675.5 μm) (peripheral height detection step). The value of Z3 is stored in the grinding end determination section 120 provided in the control means 100 . The height position Z3 obtained by comparing the detected wavelength λ1 with the table T is, as described above, the distance from the position based on the focal position of the laser light L1 having a wavelength of 350 nm. The reference position is set to be sufficiently above the surface 10 a of the wafer 10 .

Next, the above moving means is operated to move the chuck table 32 to the processing area directly below the grinding means 4, and as shown in FIG. position. Next, the rotating spindle 422 of the grinding means 4 is rotated in the direction indicated by the arrow R2 at a predetermined rotational speed (for example, 2000 rpm), and the chuck table 32 is rotated in the direction indicated by the arrow R3 by operating the rotation drive means (not shown). (for example, 100 rpm). Next, the grinding feeding means 7 is operated to lower the grinding means 4 in the direction indicated by the arrow R4 so as to approach the surface 10a of the wafer 10 held by the chuck table 32. Grinding water) is supplied, a grinding wheel 426 arranged on the lower surface of the grinding wheel 425 is brought into contact with the post region 14 of the surface 10a of the wafer 10, and the wafer is moved at a predetermined descending speed (for example, 0.5 μm/second). The post area 14 on the surface 10a of 10 is ground (grinding process).

When performing the above-described grinding process, the following grinding finishing process is performed in parallel. More specifically, as shown in FIG. 5, the detection unit 51 of the laser displacement meter 5 is positioned above the post area 14 of the wafer 10 held on the chuck table 32 . Note that if the chuck table 32 is moved to the vicinity of the processing area when performing the outer circumference height detection process, the position of the detection unit 51 of the laser displacement gauge 5 only needs to be finely adjusted. Next, high-pressure air 50 is jetted from the laser irradiation port 51b of the detection unit 51 toward the post region 14, and the laser beam L0 is irradiated from the light source 52. As shown in FIG. When the grinding process is being performed, a working fluid (grinding water) is supplied onto the surface 10a of the wafer 10, and the working fluid containing grinding dust overflows the grinding wheel 425 to the outside, causing the surface 10a of the wafer 10 to swell. cover. However, as described above, since the high-pressure air 50 is jetted from the laser irradiation port 51b of the detection unit 51, a predetermined position (indicated by the broken line 18 The machining fluid is removed from the indicated circumference. Then, while the chuck table 32 rotates once, the wavelength detector 58 detects the wavelength λ2 of the laser beam reflected at the predetermined position 18 of the post area 14 .

By the way, since a plurality of fine posts 12 are formed in the post region 14 as described with reference to FIG. The wavelength λ1 of the laser light reflected at the height of the surface 10a (same height as the outer peripheral surplus region 16) and the wavelength λ2 (λ2 < λ1) of the laser light reflected at the top of the post 12 change repeatedly. do. Here, if the wavelength λ2 is, for example, 719.1 nm before performing the above grinding process or immediately after starting the grinding process, the height position Z4 of the post 12 before grinding or at the beginning of grinding is , the wavelength λ2 (719.1 nm) is detected to be 3595.5 μm, for example, by collating it with the table T above. The value of Z4 is always stored in the grinding end determination unit 120, and the specific height of the post 12 is detected by repeatedly calculating the difference between Z3 and Z4. Data on the height of the post 12 detected based on the wavelength detected in this manner is shown in the graph on the left side of FIG. 6, for example.

While the grinding process is being performed, the grinding end determination unit 120 repeatedly performs the calculation of the difference between Z3 and Z4 at a cycle of 10 kHz (10,000 times/second), for example, so that the height of the post 12 reaches a predetermined value. It is determined whether or not the value (25 μm in this embodiment) has been reached. If the height of the post 12 does not reach the predetermined value (25 μm), the grinding process is continued. Then, as the grinding process progresses, the post 12 is ground, the wavelength λ2 of the laser beam reflected at the top of the post 12 becomes 730.1 nm, and the height position detected by comparing the wavelength λ2 with the table T Z4 becomes 3650.5 μm. As a result, the difference between the height positions Z3 (3675.5 μm) and Z4 (3650.5 μm) of the surface 10a of the outer peripheral surplus region 16 is the height of the post 12, as understood from the graph shown on the right side of FIG. height data reached 25 μm. Based on this determination, the control means 100 instructs the end of the grinding process. As a result, the wafer 10 is brought into a desired state as shown in FIG. 7, and the grinding process and the grinding finishing process are completed.

By the way, when performing the grinding finishing process as described above, it is possible to show the state of the height of the post region 14 in a graph as shown in FIG. 8 based on the wavelength detected by the wavelength detector 58 . The graph shows in detail the morphology of the surface 10a of the wafer 10, the post 12, and the shape of the graph (16C, 16D) shown in FIG. 8 during the grinding process or after the grinding process is completed. ), it is possible to detect at least one of the breakage of the post 12 as indicated by A in the drawing and the chipping of the post 12 as indicated by B in the drawing. Such detection can also be detected by visually confirming a graph displayed on a monitor (not shown) connected to the control means 100 by an operator who manages the grinding apparatus 1. However, it is also possible to automatically detect (check step) by an image processing program stored in the control means 100 . By providing such a check process, when implementing the wafer processing method as described above, it is possible to use it for the quality control of the wafer. Processing conditions in the wafer processing method can be quickly determined.

According to the present embodiment, when grinding a wafer having a post region in which a plurality of fine posts are formed and an outer peripheral surplus region surrounding the post region are formed on one surface, the height of the posts is set to a desired height. It is possible to solve the problem that it is difficult to grind to a height of

1: Grinding device 2: Device housing 21: Main body 22: Upright wall 3: Holding means 32: Chuck table 4: Grinding means 41: Moving base 42: Spindle unit 421: Spindle housing 422: Rotating spindle 423: Servo motor 424 : Wheel mount 425: Grinding wheel 426: Grinding wheel 5: Laser displacement meter 51: Detection unit 51a: Air flow path 51b: Laser irradiation port 52: Light source 53: Beam splitter 54: Projection lenses 55A, 55B: Convex lens 56: Pin Hole mask 56a: Pinhole 57: Diffraction grating 58: Wavelength detectors 6a, 6b: Bellows means 7: Grinding feed means 100: Control means 110: Verification unit 120: Grinding end determination unit

Claims (2)

A method of processing a wafer having a post region in which a plurality of fine posts are formed and an outer peripheral surplus region surrounding the post region are formed on one surface, the method comprising:
a holding step of holding the other surface of the wafer on a chuck table;
an outer peripheral height detection step of detecting the height position of the surface of the outer peripheral surplus region of the wafer held on the chuck table with a laser displacement meter;
While the chuck table is rotated, a grinding means having a rotatable grinding wheel on which a grinding wheel is arranged in a ring is brought close to the wafer held by the chuck table, and the grinding wheel passes through the center of rotation of the wafer. a grinding step to grind the post areas of the wafer such that
During the grinding process, the height position of the post ground in the post region is detected by a laser displacement meter, and the height position of the post and the height position of the surface of the peripheral surplus region are determined. a grinding termination step of terminating the grinding step when the difference between the
A wafer processing method comprising 2. The method of processing a wafer according to claim 1, wherein at least one of post breakage and chipping is detected in the grinding end step.

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