TWI443728B - Wafer grinding apparatus - Google Patents

Description

Wafer grinding device

The present invention relates to a polishing apparatus for polishing a wafer such as a semiconductor wafer and thinning it, and particularly for polishing a wafer to which a protective member such as a protective tape is attached to a surface of a device forming surface, Get technology that is only the thickness of the wafer.

A semiconductor wafer with electronic circuits such as ICs and LSIs is formed on the surface, in various electrical systems. The miniaturization of electronic devices has become an essential component today. The semiconductor wafer is a rectangular region which is divided into a lattice shape on a surface of a disk-shaped semiconductor wafer (hereinafter referred to as a wafer) by a cutting line called a boundary, and after an electronic circuit is formed in the rectangular regions. Manufactured by the steps of dividing the wafer along the boundary.

In such a manufacturing step, the wafer is polished by a polishing device to the back surface opposite to the surface on which the electronic circuit is formed, before being divided into semiconductor wafers. In addition to further miniaturization and weight reduction of electronic equipment, the polishing of the back surface is aimed at improving heat dissipation and maintaining performance, for example, from 600 μm of the original thickness to 200 to 100 μm or 50 μm. The following thickness treatment.

In general, the wafer polishing apparatus is configured such that the back surface side of the wafer is exposed, and the wafer is adsorbed and held on a vacuum type chuck, and the grindstone disposed opposite to the chuck is rotated at a high speed and pressed against the back surface to be polished. . When a wafer is provided for such a polishing apparatus, the protective tape is attached to the surface to prevent the surface from directly contacting the chuck, thereby causing damage to the electronic circuit or contamination by the grinding waste liquid. The protective tape is formed, for example, by applying a 10 μm adhesive to one side of a polyethylene or polyolefin sheet having a thickness of 100 to 200 μm, but in the protective tape, especially due to variations in thickness of the adhesive, in thickness There will be a deviation of ±5%.

In the process of grinding the wafer, the thickness is usually controlled by the total thickness of the protective tape (thickness of the wafer + thickness of the protective tape), so the thickness deviation of the protective tape will directly affect the deviation of the thickness of the wafer. Here, although the thickness deviation of the protective tape is small when the thickness of the wafer to be polished is thick, the thinner the effect on the thickness of the wafer is, the more the crystal is different depending on the case. The case where the thickness of the circle itself exceeds the allowable value and becomes too thick or otherwise is too thin. Here, it is proposed to measure the thickness of the wafer itself before the polishing process using a non-contact thickness measuring device that uses laser light reflection, and calculate the target polishing amount from the thickness and the target thickness after polishing, and the actual polishing time is The contact thickness measuring device measures the thickness of the wafer (including the thickness of the protective tape), and polishes the amount of polishing corresponding to the target polishing amount (refer to Japanese Laid-Open Patent Publication No. 2006-21264).

However, in the non-contact thickness measuring device using laser light reflection, it is difficult to accurately measure the thickness of a wafer having a thickness of, for example, 700 μm or more, which is not practical. Further, for example, even if it is a measurable thickness, the thickness of the wafer cannot be accurately measured in many cases due to the influence of the oxide film or the nitride film formed on the back surface of the wafer.

Accordingly, it is an object of the present invention to provide a wafer polishing apparatus which is subjected to polishing and thinning a back surface of a wafer having a protective member such as a protective tape on its surface, and is not affected by the thickness of the wafer or the back surface of the wafer. The influence of the presence or absence of the oxide film or the nitride film can accurately measure the thickness of the wafer itself except for the protective member, whereby the wafer of the desired thickness can be surely obtained.

A wafer polishing apparatus according to the present invention includes: a rotatable wafer holding mechanism having at least a rough polishing portion and a fine polishing portion, each of the polishing portions having a holding surface for covering a surface on which the device is formed The protective member side of the wafer of the protective member is held; the polishing mechanism is disposed to face the holding mechanism and has a rotating shaft parallel to the rotating shaft of the holding mechanism; and the feeding mechanism is configured to hold the holding mechanism and The grinding mechanism is relatively close to or apart from each other along the extending direction of the rotating shaft of the mechanisms, and at the same time, the back surface of the wafer is polished by the grinding mechanism to reduce the thickness of the wafer when approaching, and is characterized in that: the rough grinding portion is disposed. a contact thickness measuring device that is in contact with the back surface of the wafer held by the wafer holding mechanism to measure the thickness of the wafer including the protective member; and the same contact type as the contact thickness measuring device is provided in the fine polishing portion The thickness measuring device is provided with a non-contact thickness measuring device which is close to the back surface of the wafer held by the wafer holding mechanism and measures only the thickness of the wafer.

In the contact thickness measuring device of the present invention, a conventionally used altimeter or the like can be used which converts the shaking displacement to the measured thickness by bringing the shaking measuring head into contact with the back surface of the wafer. In addition, the non-contact thickness measuring device of the present invention uses a laser to reflect light, which irradiates laser light onto the wafer from the back side and is reflected from the back surface and the surface (the interface with the protective member). The time difference when reflecting light is converted into thickness.

The wafer polishing apparatus according to the present invention is configured to perform rough grinding of a thickness of 100 μm on a wafer having a thickness of, for example, 700 μm by a rough polishing portion, and then moving the wafer to a fine polishing portion to a thickness of 50 μm. The method of fine grinding. In the rough polishing portion, the thickness of the wafer including the protective member is measured while the thickness of the wafer including the protective member is measured by the thickness measuring device. However, when there is an error in the thickness of the protective member, the measured value is obtained. This error is included, but this error is not in the fine grinding and can be allowed.

Secondly, it is preferable to re-confirm the thickness of the wafer by the contact thickness measuring device in the process of performing fine polishing on the wafer which has been moved to the fine polishing portion. This is because, in the case where the thickness of the wafer after the rough polishing is thicker than the target thickness, in consideration of the thickness of the setting, there is a fear that the polishing mechanism of the finish polishing portion approaches the wafer at a relatively high speed. In order to avoid this, the thickness of the wafer can be re-measured and the grinding mechanism can be controlled according to the thickness. Since the wafer thickness measurement before the fine polishing portion is performed because the polishing surface after the rough polishing is rough, it is difficult to measure in the non-contact type. Therefore, the thickness of the wafer is first measured by a contact thickness measuring device. Further, in the initial stage of finish polishing (for example, polishing a thickness of several μm after contact with the polished surface), it is required to control the polishing while measuring the thickness of the wafer by a contact thickness measuring device. After that, the polishing surface polished by the polishing mechanism of the polishing unit is a mirror surface that can be measured by the non-contact thickness measuring device. Therefore, the wafer thickness is measured while switching to a non-contact thickness measuring device. Grinding. In the non-contact thickness measuring device, since only the thickness of the wafer itself except the protective member is measured, the thickness of the wafer alone can be accurately measured, and the thickness of the wafer is 50 μm when the thickness is 50 μm. , finish grinding.

According to the present invention, by providing the contact thickness measuring device and the non-contact thickness measuring device on the finishing portion, as described above, the thickness of the wafer before the finish polishing can be reconfirmed by the contact thickness measuring device, and The initial fine grinding is performed, and the finishing thickness of the wafer can be accurately ground to the desired thickness by fine polishing by a non-contact thickness measuring device.

In the present invention, as described above, in order to control the device, a control mechanism is provided, and the measurement signals input to the contact thickness measuring device and the non-contact thickness measuring device are input, and the feeding mechanism is controlled based on the measurement signals. The feed amount of the polishing mechanism is used to grind the wafer to a specified thickness in the rough polishing portion and the fine polishing portion; the control mechanism is in the rough polishing portion, and the feeding is controlled according to the measurement signal of the contact thickness measuring device. In the mechanism, the thickness of the wafer including the protective member is a predetermined rough polishing thickness. Then, in the finish polishing portion, first, based on the measurement signal of the contact thickness measuring device, it is confirmed whether or not the thickness of the wafer including the protective member is specified. After the thickness of the rough grinding, fine grinding is started by the grinding mechanism, and during the fine polishing, the feeding mechanism is controlled according to the measurement signal of the non-contact thickness measuring device, and the thickness of the wafer itself is not included in the protective member. It becomes the specified fine grinding thickness.

Further, as a configuration for further embodying the configuration, the control unit includes a memory unit for storing the thickness of the protective member including the wafer before rough polishing, and the thickness of the wafer. The thickness of the protective member after polishing and the target thickness after the polishing of the wafer; during the polishing of the rough polishing portion, the feeding mechanism is controlled to polish the thickness of the protective member from the wafer before the rough grinding a thickness region up to the thickness of the protective member after the rough polishing of the wafer; and then, during the polishing of the finish polishing portion, the feeding mechanism is controlled while measuring only the thickness of the wafer by the non-contact thickness measuring device After the thickness of the wafer reaches the target thickness after the pre-stored fine polishing, the control of stopping the operation of the feeding mechanism is performed.

According to the present invention, in the finish polishing portion, the contact type and the non-contact type thickness measuring device are switched in accordance with the thickness of the wafer, and the thickness of the wafer and the presence or absence of the oxide film or the nitride film on the back surface of the wafer are not affected. The influence of the surface state such as the thickness of the surface can be accurately measured, except that the thickness of the wafer is excluded except for the protective member, whereby the effect of reliably obtaining the wafer of the desired thickness can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[1]Semiconductor wafer

The component symbol 1 in the drawings 1A and 1B shows a disk-shaped semiconductor wafer (hereinafter simply referred to as a wafer) to be subjected to thinning by a back surface polishing method. The wafer 1 is a germanium wafer or the like, and the thickness before processing is, for example, about 600 to 700 μm. On the surface of the wafer 1, a plurality of rectangular semiconductor wafers (devices) 3 are partitioned by a grid-shaped dividing line 2, and ICs, LSIs, and the like are formed on the surface of the semiconductor wafers 3, not shown. electronic circuit.

After the wafer 1 is subjected to back surface polishing and thinned to a desired thickness (for example, 50 to 100 μm), the wafer 1 is cut and divided along the dividing line 2 to form a plurality of singulated semiconductor wafers 3 . . At the time of back surface polishing, as shown in FIG. 1B, a protective tape (protective member) is adhered to the surface on the side on which the electronic circuit is formed, for the purpose of protecting an electronic circuit or the like. The protective tape 4 is formed by, for example, applying an adhesive of about 10 μm on one surface of a polyethylene or a polyolefin sheet having a thickness of 100 to 200 μm.

[2] Wafer grinding device

Fig. 2 shows a wafer polishing apparatus 10 according to an embodiment. The component symbol 11 in the same figure is provided with a base of various mechanisms, and the base 11 has a rectangular parallelepiped portion having a horizontal upper surface as a main body, and one end portion in the longitudinal direction (the end portion on the depth side of FIG. 2) ) has a wall portion 12 that stands vertically. In the second drawing, the longitudinal direction, the width direction, and the vertical direction of the base 11 are indicated in the Y direction, the X direction, and the Z direction, respectively. A substantially intermediate portion in the longitudinal direction of the base 11 to the wall portion 12 side serves as the polishing region 10A, and the opposite side serves as the supply and recovery region 10B for supplying the wafer 1 before polishing to the polishing region 10A and recycling Grinded wafer 1 .

The grinding region 10A in the upper surface of the base 11 is formed with a shallow rectangular groove 11a in which a disc-shaped turntable 13 which is freely rotatable is provided, the rotation axis of which is parallel to the Z direction and the upper surface Level. This turntable 13 is rotated in the direction of the arrow R by a rotation drive mechanism (not shown). Further, on the outer peripheral portion of the turntable 13, a plurality of (in this case, three) freely rotatable chuck-shaped chuck tables 14 are provided at equal intervals in the circumferential direction thereof, and the rotation axis thereof is directed to the turntable 13 The axis of rotation is the same in the Z direction, and the upper surface (holding surface) 14a is horizontal.

The suction cup 14 is a conventional vacuum adsorption type, and the wafer 1 is placed on the upper surface 14a to be adsorbed and held. Each of the suction cups 14 is individually rotated in one direction or two directions by a rotation drive mechanism (not shown) provided in the turntable 13.

As shown in FIG. 2, in the state in which the two suction cups 14 are arranged in the X direction on the side of the wall portion 12, the rough grinding unit is sequentially disposed from the upstream side in the rotation direction of the turntable 13 directly above the suction cups 14. (grinding mechanism) 20A and finishing polishing unit (polishing mechanism) 20B. Each of the suction cups 14 is intermittently rotated by the turntable 13, and reaches the rough polishing position below the rough polishing unit 20A, the fine polishing position below the finish polishing unit 20B, and the three loading and unloading positions closest to the supply and recovery region 10B. position. Further, the suction cup 14 and the rough polishing unit 20A located at the rough polishing position constitute a rough polishing portion, and the suction cup 14 and the finish polishing unit 20B at the fine polishing position constitute a fine polishing portion.

Since the rough polishing unit 20A and the fine polishing unit 20B have the same configuration, the same reference numerals will be given.

The polishing units 20A and 20B are attached to the wall portion 12 of the base 11 so as to be movable up and down in the Z direction through the slider 31 and the guide rail 32, and are driven by a feed mechanism (feeding means) driven by the motor 34. 33 to carry out the lift. As shown in FIGS. 3 and 4, the polishing units 20A and 20B are configured to be fixed to each other when the mandrel 22 incorporated in the cylindrical casing 21 is rotationally driven by the motor 23, and is fixed to the flange 24 via the flange 24. The cup-shaped grinding wheel 25 at the tip end of the mandrel 22 is rotated, and a plurality of grindstones 26 fixed to the outer circumference of the outer surface of the cup-shaped grinding wheel 25 are annularly arranged to polish the workpiece. The outer diameter of the circular grinding track of the grindstone 26 is substantially equal to the diameter of the wafer 1.

Each of the polishing units 20A and 20B is offset from the suction cup 14 so as not to be coaxially disposed. As shown in detail in Fig. 4, the substantially central portion of the blade edge (radial length) of the blade edge located at the innermost side of the chuck 14 among the plurality of grindstones 26 arranged in a ring shape is located at a vertical portion passing through the center of the suction cup 14. The way on the line to set the relative position. According to this positional relationship, when the back surface of the wafer 1 is pressed by the grindstone 26 of the cup-shaped grinding wheel 25 while the chuck 14 is rotated together with the wafer 1, the back surface thereof is completely polished. For the grindstone 26 of the rough grinding unit 20A, for example, a diamond abrasive grain containing #280 to #600 is used, and the grindstone 26 of the fine grinding unit 20B is made of, for example, a diamond abrasive grain containing #2000 to #8000.

Further, the cup-shaped grinding wheel 25 is provided with a polishing water supply port (not shown), and the lower workpiece is supplied with polishing water for cooling, lubricating or polishing, and the polishing unit 20A, 20B is provided with a pair. A water supply line (not shown) for supplying the grinding water to the polishing water supply port.

The rough polishing unit 20A and the fine polishing unit 20B configured as described above are each fixed to the slider 31 by passing the casing 21 through the block 27.

As shown in Fig. 2, a suction cup washing nozzle 15 is disposed around the turntable 13 in the recess 11a of the base 11 and closest to the supply and recovery area 10B for discharging the washing water. The suction cup 14 is washed toward the suction cup 14 at the loading and unloading position. Further, a drain hole 16 for discharging the water in the recess 11a to the outside is provided at a corner of the wall portion 12 side of the recess 11a.

The wafer 1 is in a rough grinding position, and is coarsely ground by the rough grinding unit 20A to, for example, about 30 μm thicker than the fine grinding thickness, and then finely ground by the finishing polishing unit 20B to the purpose of fine polishing at the fine polishing position. thickness. As shown in Fig. 2, a rough polishing side thickness measuring unit 40 and a finishing polishing side thickness measuring unit 50 for measuring the thickness of the wafer 1 are provided around the turntable 13 in the recess 11a and in the vicinity of each polishing position. . The wafer 1 is polished to the desired thickness while being measured by the thickness measuring units 40 and 50 at the respective polishing positions.

First, the fine polishing side thickness measuring unit 50 will be described. As shown in Fig. 3, the unit 50 is fixed to the contact thickness measuring device 53 and the non-contact thickness measuring device 54 composed of a pair of altimeters 51 and 52. The structure of the bracket 59 supported by the base 11.

Each of the altimeters 51, 52 of the contact thickness measuring device 53 is a conventionally known one and has a probe 51b that extends horizontally from the measuring body portion 51a, 52a fixed to the holder 59 and that is rocked, The equivalent configuration of 52b is divided into a reference side altimeter 51 and a variable side altimeter 52, wherein the front end of the former probe 51b is always in contact with the upper surface 14a of the suction cup 14 to determine the height position of the upper surface 14a thereof. The front end of the probe 52b of the latter is always in contact with the back surface (abrasive surface) of the wafer 1 held on the chuck 14 to determine the height position of the back surface of the wafer 1. Each of the altimeters 51 and 52 converts the shaking of the probes 51b and 52b into electrical signals by a coil type sensor built in the measurement main body portions 51a and 52a by electromagnetic induction, and outputs them as measured values of height positions. Composition. The contact-type thickness measuring device 53 composed of the altimeter 51 and 52 is converted from the difference between the measured value of the fluctuation side altimeter 52 and the measured value of the reference side altimeter 51, and the total of the wafer 1 is converted. Thick (including protective tape 4).

The non-contact thickness measurer 54 has a laser head 56 attached to the front end of an arm 55 fixed to the bracket 59 and extending horizontally on the suction cup 14, and the visible light semiconductor laser light is vertically irradiated onto the suction cup 14. Wafer 1 and receives reflected light from wafer 1. The laser heads 56 respectively receive the reflected light of the laser beam reflected from the surface (the interface with the protective member) on the back side and the lower side of the upper side of the wafer 1 held on the chuck 14. The non-contact thickness measuring device 54 converts the thickness of the wafer 1 from the time difference when the reflected light is received by the laser head 56. For the non-contact type thickness measuring device 54 that uses the reflection of the laser light, for example, the constituents described in Japanese Laid-Open Patent Publication No. 2001-203249 can be used.

A gas nozzle 58 is attached to the holder 59 through the nozzle holder 57, which blows air onto the irradiation surface of the laser beam to be irradiated onto the wafer 1 from the laser head 56 to remove water such as grinding water. In order to prevent the measurement accuracy from deteriorating due to the penetration of water by the laser light. An air pressure feed line (not shown) is connected to the gas nozzle 58.

On the other hand, the rough-grinding-side thickness measuring unit 40 is constituted by a contact-type thickness measuring device 43 having the same configuration as that of the contact-type thickness measuring unit 53 of the fine-grinding-side thickness measuring unit 50, that is, by measuring the suction cup 14. The reference altimeter 41 at the height position of the surface and the fluctuation side altimeter 42 that always touches the back surface of the wafer 1 to measure the height position of the back surface of the wafer 1 are configured. Each of the altimeters 41 and 42 has a configuration in which probes 41b and 42b that are rocked are attached (see FIGS. 5A and 5C).

The above is the configuration of the polishing zone 10A on the base 11, and the supply and recovery zone 10B will be described next with reference to FIG.

A two-link type transfer robot arm 60 that moves up and down is provided in the center of the supply and collection area 10B. Further, around the transfer robot arm 60, the supply port 61, the alignment table 62, the arm type supply arm 63, and the supply arm 63 are disposed in the counterclockwise direction in a state viewed from the top. The recovery arm 64, the spinner cleaning device 65 and the recovery crucible 66 are constructed.

The supply port 61, the alignment stage 62, and the supply arm 63 are means for supplying the wafer 1 to the chuck 14, and the recovery arm 64, the spin type cleaning device 65, and the recovery cassette 66 are collected from the suction cup 14 to complete the back surface. The means of grinding the wafer 1. In the case of the crucibles 61 and 66, the plurality of wafers 1 are placed in a stacked state at a predetermined interval in the vertical direction, and are set at a predetermined position of the base 11.

When a wafer 1 is taken out from the supply cassette 61 by the transfer robot arm 60, the wafer 1 is attached to the back side of the unattached protective tape 4

The upper state is placed on the alignment station 62 where it is determined by a certain position. Next, the wafer 1 is sucked and picked up from the alignment table 62 by the supply arm 63, and then placed on the chuck 14 that is waiting at the loading and unloading position.

On the other hand, the wafer 1 which is back-polished by each of the polishing units 20A and 20B and positioned on the chuck 14 at the loading and unloading position is sucked by the recovery arm 64 and taken up, and then moved to the cleaning device 65 for washing. And dry. Then, the wafer 1 after the cleaning process is completed by the cleaning device 65 is transferred to the recovery cassette 66 by the transfer robot 60 and stored.

The mechanical configuration of the wafer polishing apparatus 10 is as described above. However, as shown in FIG. 2, the wafer polishing apparatus 10 has a control mechanism 70 that is input to the contact thickness measuring device 43 of the rough polishing side thickness measuring unit 40. The measured value and the measured value of the contact thickness measuring device 53 of the finish polishing side thickness measuring unit 50 and the measured value of the non-contact thickness measuring device 54. The control unit 70 controls the motors 23 that rotate the cup-shaped grinding wheels of the rough polishing unit 20A and the finishing polishing unit 20B or the feeding mechanisms 33 that raise and lower the polishing units 20A and 20B based on the thickness measurement values. The action of the motor 34. Further, the control unit 70 has a memory unit 71 for inputting "the thickness (total thickness) of the wafer 1 containing the protective tape 4 before polishing" from a suitable input means, and the purpose of "protection after rough grinding" The thickness (total thickness) of the wafer 1 with the tape 4, and the purpose of "only the finishing thickness of the wafer 1", and memorize the data.

Next, an operation of polishing the back surface of the wafer 1 by the wafer polishing apparatus 10 including the control of the control unit 70 will be described.

First, by transferring the robot arm 60, one of the wafers 1 accommodated in the supply cassette 61 is moved to the alignment stage 62 for alignment, and then the wafer side 1 is placed on the wafer 1 with the back side up by the supply arm 63. It is placed on the suction cup 14 which is in standby at the loading and unloading position and is in a vacuum operation. Thereby, the wafer 1 is adsorbed and held on the upper surface 14a while the protective tape 4 on the front side is in close contact with the upper surface 14a of the chuck 14 and the back surface is exposed. Further, at this time, the probes 41b and 42b of the respective altimeters 41 and 42 of the contact thickness measuring device 43 on the rough grinding side are appropriately turned upward to avoid the upper surface 14a of the suction cup 14.

Then, the turntable 13 is rotated in the direction of the arrow R shown in FIG. 2, and the chuck 14 holding the wafer 1 is stopped at the rough polishing position. At this time, the next suction cup 14 is positioned at the loading and unloading position, and the next wafer 1 to be polished is set on the suction cup 14 as described above.

At the rough polishing position, the wafer 1 is rotated in one direction by rotating the chuck 14, and the reference altimeter 41 and the variable side altimeter 42 of the contact thickness measuring device 43 on the rough polishing side are simultaneously Each of the probes 41b and 42b is lowered to come into contact with the upper surface 14a of the chuck 14 and the back surface of the exposed surface of the wafer 1 to maintain the thickness of the wafer 1 including the protective tape 4. Then, the coarse polishing unit 20A is lowered by the feeding mechanism, and while the polishing water is supplied, the grindstone 26 of the cup-shaped grinding wheel 25 that rotates at a high speed is pressed against the back surface of the wafer 1 to be polished. Further, when the rough grinding unit 20A is lowered, when the grindstone 26 of the cup-shaped grinding wheel 25 is lowered at a relatively high speed before approaching the wafer 1 according to the measured value of the contact thickness measuring device 43, the time can be shortened. More ideal.

Figs. 5A and 5C show the wafer 1 on the chuck 14 before polishing, and Fig. 5A shows that the protective tape 4 is thick, and Fig. 5C shows that the protective tape 4 is thin. The contact thickness measuring device 43 measures the total thickness t (t1 + t4) of the wafer 1 and the protective tape 4. Here, the control unit 70 compares the total thickness t based on the contact thickness measuring device 43 with the total thickness of the wafer 1 including the protective tape 4 input in advance, and the total thickness t of the measured value is greatly increased to exceed the allowable value. In the case of the value (for example, if the grindstone 26 collides with the wafer 1 or the like), the alarm processing is performed to temporarily suspend the operation of the operation or the like. Further, in Figs. 5A and 5C, it is shown that there is an error in the thickness t4 of the protective tape 4, and there is an error in the thickness t1 of the wafer 1, and therefore it is necessary to grasp the total thickness t.

Further, during the rough polishing, the thickness (total thickness t) of the wafer 1 measured by the contact thickness measuring device 43 is input to the control unit 70 one by one, and the control unit 70 controls the rough grinding unit 20A based on the measured value. The motor 34 controls the amount of feed of the cup-shaped grinding wheel 25, that is, the amount of grinding. Next, the control unit 70 determines that the measured value of the touch thickness measuring device 43 has reached the thickness of the rough polishing stored in the memory unit 71 (the thickness of the wafer 1 including the protective tape 4 after the rough polishing). The cup-shaped grinding wheel 25 of the feeding mechanism 33 is lowered, and after maintaining the original state for a predetermined period of time to rotate the cup-shaped grinding wheel 25, the rough grinding unit 20A is raised to end the rough grinding. As described above, the thickness of the rough grinding is set to be about 30 μm thicker than the finish polishing thickness.

Next, the wafer 1 that has finished the rough polishing is transferred to the fine polishing position by rotating the turntable 13 in the R direction. Further, the wafer 1 previously set at the attaching and detaching position is transferred to the rough polishing position, and the wafer 1 is subjected to rough polishing while performing the same thickness measurement as described above while performing the finish polishing. Further, on the chuck 14 moved to the loading and unloading position, the next wafer 1 to be processed is set.

In the finishing position, first, the chuck 14 is rotated together with the wafer 1, and the thickness of the wafer 1 is measured in the same manner as described above by the contact thickness measuring device 53 of the finishing side thickness measuring unit 50 (total thickness t ). The thickness measurement value of the contact thickness measuring device 53 is the same as the thickness of the rough polishing. If the measured value of the contact thickness measuring device 43 on the rough grinding side is different from the actual thickness, the grinding stone 26 of the finishing polishing unit 20B is made. When the wafer 1 is lowered at a relatively high speed before approaching the wafer 1, the operation may not be performed properly. For example, the grindstone 26 collides with the wafer 1 as described above. In order to avoid such a defect beforehand, it is necessary to re-measure and determine the thickness of the wafer 1 including the protective tape 4 by the contact thickness measuring device 53.

Next, the finish polishing unit 20B is caused to drop at a relatively high speed before the grindstone 26 of the cup-shaped grinding wheel 25 approaches the wafer 1 according to the measured value of the contact thickness measuring device 53, and then, by the contact thickness measuring device 53 The thickness of the wafer 1 was measured, and the back surface of the wafer 1 was polished to a size of about several μm using the finish polishing unit 20B in the same manner as the rough polishing. Thereby, since the back surface of the wafer 1 is a mirror surface which can be measured by the non-contact thickness measuring device 54, the thickness measurement of the wafer 1 is switched to the non-contact thickness measuring device 54 to polish the wafer 1. This fine polishing is performed by the non-contact thickness measuring device 54 while measuring only the thickness of the wafer 1. Moreover, from the viewpoint of accurately measuring the thickness of only the wafer 1 itself by the non-contact thickness measuring device 54, the thickness (rough polishing thickness) of the wafer 1 which is transferred to the finish polishing is preferably about 200 μm or less.

During the fine polishing, the thickness of the wafer 1 measured by the non-contact thickness measuring device 54 is input to the control mechanism 70 one by one, and the control mechanism 70 controls the motor 34 of the finishing polishing unit 20B based on the measured value to control the cup. The feed amount of the shaped grinding wheel 25 is also the amount of grinding. Then, the fine polishing is continued, and after the control unit 70 determines that the measured value of the non-contact thickness measuring device 54 reaches the fine grinding thickness stored in the memory unit 71, the falling of the cup-shaped grinding wheel 25 by the feeding mechanism 33 is stopped. After the cup-shaped grinding wheel 25 is rotated while maintaining its original state for a certain period of time, the finish polishing unit 20B is raised to finish the finish polishing.

Here, preferred operating conditions of rough grinding and fine grinding are exemplified. The grinding unit 20A, 20B of the rough grinding and the fine grinding has a rotation speed of the cup-shaped grinding wheel 25 of 3,000 to 5,000 RPM, and the rotation speed of the suction cup 14 is 100 to 300 RPM. Further, the rate of decrease of the feed rate of the rough grinding unit 20A is 3 to 5 μm/sec, and the descending speed of the polishing unit 20B is 0.3 to 1 μm/sec.

After both the finish polishing and the rough polishing are completed, the turntable 13 is rotated to transfer the finished finely polished wafer 1 to the loading and unloading position. Thereby, the subsequent wafers 1 are respectively transferred to the rough grinding position and the fine grinding position. The wafer 1 positioned on the chuck 14 at the loading and unloading position is moved to the cleaning device 65 by the recovery arm 64 to be washed and dried. Then, the wafer 1 after the cleaning process is completed by the cleaning device 65 is transferred to the recovery cassette 66 by the transfer robot 60 and stored.

The above is a cycle in which one wafer 1 is thinned to the intended fine polishing thickness and washed and recovered. According to the wafer polishing apparatus 10 of the present embodiment, the wafer 1 is roughly polished in the rough polishing position while the turntable 13 is intermittently rotated, and fine polishing is performed at the fine polishing position. The polishing process of the plurality of wafers 1 is efficiently performed.

In the wafer polishing apparatus 10 of the present embodiment, first, the total thickness (t) of the wafer 1 including the protective tape 4 is measured by the contact thickness measuring device 43 of the rough polishing side thickness unit 40, and coarse grinding is performed. The unit 20A performs rough polishing on the wafer 1 to thin the wafer 1 until, for example, the thickness of the finished product is 30 μm. Then, in the finish polishing, the thickness of the wafer 1 is re-measured by the contact thickness measuring device 53 to confirm that it is safe, and then the thickness of the wafer 1 is measured by the non-contact thickness measuring device 54 while polishing. The step of polishing is completed after the wafer 1 is thinned to the finished thickness. In the case of rough polishing, although the thickness of the wafer 1 including the protective tape 4 is measured, the measured value is not fine polishing, so even if, for example, the thickness of the protective tape 4 has an error, it is allowed. Then, after the migration to the finish polishing, only the thickness of the wafer 1 is measured by the non-contact thickness measuring device 54, so that the thickness of the wafer 1 can be accurately measured, and the thickness of the protective tape 4 and the wafer 1 can be incorrectly determined. The wafer 1 is surely processed to a desired thickness irrelevantly.

5B and 5D show the state in which the wafer 1 is polished while the thickness of the wafer 1 shown in FIGS. 5A and 5C is measured by the contact thickness measuring device 53 and the non-contact thickness measuring device 54. If only the thickness of the wafer 1 is measured by the contact thickness measuring device 53, only the total thickness t can be controlled. When the thickness t4 of the protective tape 4 is different from each other as shown, the crystal is polished. The thickness t1 of the circle 1 is also different. However, the thickness of only the wafer 1 is measured by the non-contact thickness measuring device 54, and the grinding feed amount is controlled based on the measured value. Even if the thickness of the protective tape 4 is different, the finishing thickness of the wafer 1 can be always made. for sure.

Further, on the fine polishing side, the thickness of the wafer 1 before polishing is re-measured by the contact thickness measuring device 53, and the measurement is continued, and the grinding stone having the cup-shaped grinding wheel 25 can be obtained until the completion of the finish polishing. The meaning of the amount of wear of 26 is.

1. . . Semiconductor wafer

2. . . Split line

3. . . Semiconductor wafer

4. . . Protective tape

10. . . Wafer grinding device

10A. . . Grinding area

10B. . . Supply and recycling area

11. . . Abutment

11a. . . Groove

12. . . Wall

13. . . Turntable

14. . . Suction cup

14a. . . Upper surface (holding surface)

15. . . Suction cup cleaning nozzle

16. . . drainage hole

20A. . . Rough grinding unit

20B. . . Fine grinding unit

twenty one. . . case

twenty two. . . Mandrel

twenty three. . . motor

twenty four. . . Flange

25. . . Cup grinding wheel

26. . . Grindstone

27. . . Block

31. . . Slider

32. . . guide

33. . . Feeding mechanism

34. . . motor

40. . . Rough grinding side thickness measuring unit

41. . . Benchmark altimeter

41b, 42b. . . Probe

42. . . Variable side altimeter

43. . . Contact thickness gauge

50. . . Fine grinding side thickness measuring unit

51, 52. . . Altimeter

51a, 52a. . . Measuring body

51b, 52b. . . Probe

53. . . Contact thickness gauge

54. . . Non-contact thickness gauge

55. . . Arm

56. . . Laser head

57. . . Nozzle bracket

58. . . Gas nozzle

59. . . support

60. . . Transfer robot

61. . . Supply

62. . . Position alignment table

63. . . Supply arm

64. . . Recycling arm

65. . . Cleaning device

66. . . Recycling

70. . . Control mechanism

71. . . Memory department

t. . . Wafer thickness including guard tape

T1. . . Only the thickness of the wafer itself

T4. . . Protective tape thickness

Figs. 1A and 1B are views showing a semiconductor wafer on which a back surface is polished by an embodiment of the present invention, and Fig. 1A is a perspective view, and Fig. 1B is a side view.

Fig. 2 is an overall perspective view of a wafer polishing apparatus according to an embodiment.

Fig. 3 is a perspective view of a polishing unit included in the wafer polishing apparatus shown in Fig. 1.

Fig. 4 is a side view of the polishing unit included in the wafer polishing apparatus shown in Fig. 1.

5A and 5C are cross-sectional views showing a state in which the thickness of the wafer having different thicknesses of the protective tape is measured by the contact thickness measuring device, and FIGS. 5B and 5D are diagrams showing the contact thickness measuring device and the non-contact type, respectively. The thickness measuring device is a side view in a state in which the thickness of the wafer shown in FIGS. 5A and 5C is measured while the thickness is measured.

1. . . Semiconductor wafer

4. . . Protective tape

14. . . Suction cup

14a. . . Upper surface (holding surface)

41b, 42b. . . Probe

43. . . Contact thickness gauge

51b, 52b. . . Probe

53. . . Contact thickness gauge

54. . . Non-contact thickness gauge

55. . . Arm

56. . . Laser head

58. . . Gas nozzle

t. . . Wafer thickness including guard tape

T1. . . Wafer thickness only

T4. . . Protective tape thickness

Claims (1)

A wafer polishing apparatus comprising: a rotatable wafer holding mechanism having at least a rough polishing portion and a fine polishing portion, each of the polishing portions having a holding surface for covering a surface on which the device is formed with a protective member Holding the protective member side of the wafer; the grinding mechanism is disposed to face the holding mechanism and has a rotating shaft parallel to the rotating shaft of the holding mechanism; and the feeding mechanism is configured to hold the holding mechanism The grinding mechanism is relatively close to or separated from each other along the extending direction of the rotating shaft of the mechanisms, and the back surface of the wafer is polished by the grinding mechanism to reduce the thickness of the wafer when approaching, the wafer polishing apparatus The method of providing a contact thickness measuring device in contact with the back surface of the wafer holding mechanism exposed by the wafer holding mechanism to determine the thickness of the wafer including the protective member; The fine grinding portion is provided with the same contact thickness measuring device as the contact thickness measuring device, and a non-contact thickness measuring device is provided, which is opposite to the crystal held by the wafer holding mechanism The exposed back surface is close to each other, and only the thickness of the wafer is measured. The wafer polishing apparatus has a control mechanism that is input to each of the contact thickness measuring device and the measurement signal of the non-contact thickness measuring device, and according to the measurement. The signal is used to control the feed amount of the polishing mechanism based on the feed mechanism, and the wafer is ground to a specified thickness in the rough polishing portion and the fine polishing portion; the control portion has a memory portion for storing the The thickness of the wafer before the rough grinding including the protective member, and the thickness of the wafer after the rough grinding The thickness of the protective member and the target thickness after the polishing of the wafer; the control mechanism controls the feeding mechanism according to the measurement signal of the contact thickness measuring device when polishing by the rough polishing portion, from the crystal The thickness of the round material before the rough polishing including the protective member is up to the thickness of the target material including the protective member after the rough polishing of the wafer; and then the following control is performed, and when the polishing is performed by the fine polishing portion, first The measurement signal of the contact thickness measuring device starts to perform fine polishing by the polishing mechanism after confirming whether the thickness of the wafer including the protective member is the thickness after the specified rough polishing, and according to the non-contact during the fine polishing The measurement signal of the thickness measuring device controls the feeding mechanism only while measuring the thickness of the wafer not including the protective member, and stops only after the thickness of the wafer reaches the target thickness after the fine polishing which is stored in advance. Give the action of the organization.