JP2023128351A - Processing method - Google Patents

Abstract

To flatness a protective member by grinding, and prevent adhesion of a bond material of a dressing board to a grindstone and a wafer.SOLUTION: A processing method of a protective member and a grindstone bonded to a front side of a wafer, includes: a rear side holding step of exposing the other surface side of the protective member in which one surface side is bonded to the front side by holding the rear side of the wafer with a chuck table; a flatness step of reducing a level of unevenness of the other surface side of the protective member by grinding the other surface side of the protective member with the grindstone after the rear side holding step; and a dressing step of dressing the grindstone by grinding the grindstone while bringing it in contact with the rear side of the wafer or a single crystal substrate formed by the same material with the single crystal substrate constructing the wafer, after the flatness step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for processing a protective member and a grinding wheel attached to the front side of a wafer, and a method for processing a wafer, a protective member, and a grinding wheel for grinding the protective member.

Electronic devices such as mobile phones and personal computers are equipped with device chips. When manufacturing a device chip, for example, first, a plurality of devices such as ICs (Integrated Circuits) are formed on the front surface side of a disk-shaped wafer made of a semiconductor material such as silicon.

Next, the back side of the wafer is ground to be thinned to a predetermined thickness, and the ground wafer is cut and divided into devices. This divides the wafer into multiple device chips.

By the way, when grinding the back side of a wafer, a resin protective member (protective tape) is usually attached to the front side of the wafer in order to reduce damage to devices. Then, while the front side of the wafer is held under suction by a chuck table, the back side of the wafer is ground (for example, see Patent Document 1).

However, there is variation in the in-plane thickness of the protective member, and this variation in in-plane thickness may affect the processing accuracy of the wafer during grinding (that is, the flatness of the wafer after grinding). In particular, when the finished thickness is made relatively thin or when a wafer with bumps provided on the front side is ground, the influence of variations in the in-plane thickness of the protective member becomes relatively large.

In addition, when the protective member is attached to the front side of the wafer, irregularities caused by devices and the like provided on the front side of the wafer are also reflected on the protective member. If the back side of the wafer is ground with the unevenness reflected on the protective member, the unevenness will be formed on the back side of the wafer after grinding, resulting in a decrease in processing accuracy.

Therefore, a method has been proposed in which the protective member is polished before grinding the back side of the wafer (for example, see Patent Document 2). In this method, the protective member attached to the front side of the wafer is polished to flatten the base film constituting the protective member, and then the back side of the wafer is ground.

On the other hand, for example, by using a grinding device, the protective member attached to the front side of the wafer is ground and flattened, and then the wafer is turned over and the front side of the wafer is held by suction on a chuck table. However, it is conceivable to then grind the back side of the wafer.

However, when the protective member is ground with a grinding wheel, the grinding wheel becomes clogged, making subsequent grinding difficult. Therefore, after grinding the protective member and before grinding the back side of the wafer, it is necessary to use a dressing board to eliminate clogging of the grinding wheel.

JP 61-141142 Publication Japanese Patent Application Publication No. 2005-19666

However, the dressing board may have a bond material of a different material than the grinding wheel. If the grinding wheel is dressed with a dressing board having a bond material different from that of the grinding wheel, the bonding material of the dressing board will adhere to the grinding wheel and the wafer.

The present invention has been made in view of the above problems, and an object of the present invention is to flatten a protective member by grinding and to prevent a dressing board bond material from adhering to a grinding wheel and a wafer.

According to one aspect of the present invention, there is provided a method for processing a protective member and a grinding wheel attached to the front side of a wafer, wherein the back side of the wafer is held on a chuck table and one side is attached to the front side. After the back side holding step, the other side of the protective member is ground with the grinding wheel to expose the other side of the protective member. A flattening step to reduce the degree of unevenness on the side, and after the flattening step, the grinding wheel is applied to the back side of the wafer or to a single crystal substrate formed of the same material as the single crystal substrate constituting the wafer. A processing method is provided that includes a dressing step of dressing the grinding wheel by contacting and grinding.

Preferably, the grinding wheel has abrasive grains having an average grain size of 1 μm or more and 20 μm or less, and a vitrified bond, and the concentration of the abrasive grains in the grinding wheel is 50 or more and 150 or less.

According to another aspect of the present invention, there is provided a method for processing a wafer, a protection member, and a grinding wheel for grinding the protection member, comprising: a pasting step of pasting one side of the protection member on the front side of the wafer; a rough grinding process in which the back side of the wafer is roughly ground with a first grinding wheel having a first grinding wheel; a finish grinding step of performing finish grinding on the back side of the wafer, and before the rough grinding step or before the finish grinding step, the back side of the wafer is held on a chuck table and the protective member is A back side holding step of exposing the other side, and after the back side holding step, the other side of the protective member is ground with a grinding wheel for grinding the protective member, so that the other side of the protective member is A flattening step is performed to reduce the degree of unevenness, and after the flattening step, a polishing layer for grinding the protective member is applied to the back side of the wafer or to a single crystal substrate made of the same material as the single crystal substrate constituting the wafer. A processing method is provided that further includes a dressing step of dressing a grinding wheel for grinding the protective member by bringing a grinding wheel into contact with the protective member.

In the processing method according to one aspect of the present invention, after the step of flattening the protective member, a grinding wheel is brought into contact with the back side of the wafer or a single crystal substrate formed of the same material as the single crystal substrate constituting the wafer. Dress the grinding wheel by grinding.

In this way, dressing the grinding wheel without using a dressing board can cause problems when the bonding material of the dressing board and the bonding material of the grinding wheel are different. can prevent adhesion of bond material.

FIG. 3 is a flow diagram of a processing method in the first embodiment. It is a figure which shows the pasting process. It is a figure which shows the back side holding process. It is a figure showing a planarization process. It is a figure showing a reversal process. It is a figure showing a dressing process. It is a flowchart of the processing method in 2nd Embodiment. It is a figure which shows the dressing process in 2nd Embodiment. It is a flowchart of the processing method in a 3rd embodiment. It is a top view showing an outline of a grinding device used in a 3rd embodiment. FIG. 11(A) is a side view showing a wafer unit placed on a temporary holding table, and FIG. C) is a side view showing the wafer unit being transferred to the chuck table. It is a figure showing a rough grinding process. It is a figure showing a final grinding process. It is a flowchart of the processing method in a 5th embodiment.

Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. In the first embodiment, as shown in FIG. 1, a pasting process S10, a back side holding process S20, a flattening process S30, an inversion process S40, and a dressing process S50 are performed in this order.

FIG. 1 is a flow diagram of the processing method in the first embodiment. The wafer 11 has a disk-shaped single crystal substrate made of silicon, for example (see FIG. 2). Note that the material of the single crystal substrate is not limited to silicon.

The single crystal substrate constituting the wafer 11 may be formed of other semiconductors or compound semiconductors such as SiC (silicon carbide) and GaN (gallium nitride). The wafer 11 has, for example, a diameter of 200 mm (ie, 8 inches) and a thickness of 725 μm, but the diameter and thickness are not limited to these numerical examples.

As shown in FIG. 2, on the front surface 11a of the wafer 11, a plurality of dividing lines (street) 13 are set in a grid pattern. A device 15 such as an IC is formed in each of the rectangular areas partitioned by a plurality of planned division lines 13.

A metal bump (not shown) may also be provided on the device 15. When grinding the back surface 11b side of the wafer 11, a protective member 17 made of resin is closely attached to the front surface 11a side in order to protect the devices 15 located on the front surface 11a side.

The protective member 17 of this embodiment is a so-called protective tape, and has a laminated structure of a base material layer 17a and an adhesive layer (glue layer) 17b (see FIG. 3). The base layer 17a is made of, for example, polyolefin or polyethylene terephthalate, and the adhesive layer 17b is made of, for example, an epoxy, acrylic, or rubber adhesive.

The thickness of the base layer 17a is greater than the thickness of the adhesive layer 17b. For example, the base layer 17a has a thickness of 100 μm or more and 500 μm or less, and the adhesive layer 17b has a thickness of 5 μm or more and 200 μm or less.

The adhesive layer 17b of the protective member 17 may be a UV-cured resin that hardens and loses its adhesive strength when exposed to UV (ultraviolet) irradiation, or a thermosetting resin that hardens and loses its adhesive strength when heated. Good too. Note that the protective member 17 may have only the base material layer 17a without having the adhesive layer 17b.

The protective member 17 is attached in close contact with the surface 11a by bonding by pressing using a roller, vacuum bonding, thermocompression bonding, or the like. In this embodiment, one surface 17c of the protective member 17 exposed on the adhesive layer 17b side is pasted on the front surface 11a side of the wafer 11 (pasting step S10).

FIG. 2 is a diagram showing the pasting step S10. In the pasting step S10, for example, the back side 11b of the wafer 11 is held under suction using a disk-shaped chuck table (not shown), and one side of the approximately square protection member 17 having each side larger than the diameter of the wafer 11 is attached. The 17c side is attached to the surface 11a side.

Thereafter, the protective member 17 is cut along the outer circumference of the wafer 11 with a cutting blade (not shown), thereby forming a wafer unit 19 in which the wafer 11 and the protective member 17 having approximately the same diameter are stacked. Note that the adhesive layer 17b side of the protective member 17, which is previously formed in a circular shape, may be attached to the surface 11a side.

When the one surface 17c is attached to the surface 11a, the other surface 17d of the protective member 17 located on the opposite side to the one surface 17c is exposed. Irregularities 17e are formed on the other surface 17d of the protective member 17 after the pasting step S10 (see FIG. 3). The unevenness 17e is caused by unevenness on the surface 11a side of the wafer 11, variations in the in-plane thickness of the protective member 17 itself, and the like.

The degree of the unevenness 17e on the other surface 17d side shown in FIG. 3 is, for example, the arithmetic mean roughness (Ra), maximum height roughness (Rz), and It is evaluated by root mean square roughness (Rq), etc.

For example, the degree of the unevenness 17e on the other surface 17d side shown in FIG. 3 is measured by maximum height roughness (Rz), and is 10 μm or more and 500 μm or less.

Note that the thickness unevenness (ie, TTV (total thickness variation)) on the back surface 11b side of the wafer 11 according to SEMI standards (Semiconductor Equipment and Materials International standards) is 10 μm or less.

After the pasting step S10, the back surface 11b side of the wafer 11 is held by suction with a disk-shaped chuck table 4 provided in the grinding device 2 (back side holding step S20). Therefore, next, the configuration of the grinding device 2 will be explained.

The grinding apparatus 2 of this embodiment is a manual type in which an operator manually places the wafer 11 on the chuck table 4, takes out the wafer 11 from the chuck table 4 (see FIG. 3), and inverts the wafer 11. It is.

Furthermore, the grinding device 2 of this embodiment is of an infeed grinding type in which grinding is performed by lowering the grinding unit 8 (see FIG. 4) along the Z-axis direction. Note that the Z-axis direction is, for example, parallel to the vertical direction.

The chuck table 4 has a disc-shaped frame made of non-porous ceramics. A disc-shaped recess (not shown) is formed on the upper surface side of the frame. A disc-shaped porous plate (not shown) made of porous ceramics is fixed in the recess.

A suction source (not shown) such as a vacuum pump is connected to the frame, and the negative pressure generated by the suction source can be transmitted to the porous plate. The upper surface of the porous plate and the upper surface of the frame are formed substantially flush with each other, and constitute a holding surface 4a that holds the wafer unit 19 under suction.

The holding surface 4a has a conical shape in which the central portion protrudes slightly compared to the outer circumferential portion, but the amount of protrusion is very small, for example, 20 μm, so the holding surface 4a is shown as substantially flat in the drawings from FIG. 3 onwards.

A rotational drive source (not shown) such as a motor is provided below the chuck table 4. The torque of the rotational drive source is transmitted to the rotating shaft 6 (see FIG. 4) of the chuck table 4 via a pulley, an endless belt (both not shown), and the like. In addition, in FIG. 4, the rotating shaft 6 is shown simplified with a dashed line.

The rotating shaft 6 is slightly tilted in a predetermined direction by an angle adjustment mechanism (not shown) so that a part of the holding surface 4a is substantially parallel to the grinding surface 14c of the grinding wheel 14. Further, the chuck table 4 is configured to be movable along the Y-axis direction orthogonal to the Z-axis direction by a ball screw type Y-axis direction movement unit (not shown).

The Y-axis direction movement unit moves the chuck table 4 to a loading/unloading area A1 where the wafer 11 is loaded and unloaded, and a grinding area A2 where the protection member 17 and the wafer 11 are ground.

A grinding unit 8 is provided above the chuck table 4 arranged in the grinding area A2. The grinding unit 8 has a cylindrical spindle housing (not shown) whose longitudinal direction is arranged along the Z-axis direction.

A ball screw type grinding feed mechanism (not shown) that moves the grinding unit 8 along the Z-axis direction is connected to the spindle housing. A portion of a cylindrical spindle 10 is rotatably held within the spindle housing.

The longitudinal direction of the spindle 10 is arranged along the Z-axis direction. A rotational drive source (not shown) such as a motor is provided at the upper end of the spindle 10, and a disc-shaped mount 12 is fixed to the lower end of the spindle 10.

An annular grinding wheel 14 is attached to the lower surface of the mount 12. The grinding wheel 14 has an annular wheel base 14a made of metal such as aluminum alloy. The upper surface side of the wheel base 14a is fixed to the lower surface side of the mount 12.

On the lower surface side of the wheel base 14a, a plurality of segment-shaped grinding wheels (grinding wheels for grinding the protective member) 14b are arranged in an annular manner along the circumferential direction of the wheel base 14a. When the spindle 10 is rotated, an annular grinding surface 14c is formed by the trajectory of the lower surface of the plurality of grinding wheels 14b.

The grinding wheel 14b includes abrasive grains made of diamond, cBN (cubic boron nitride), etc., and a bond material for fixing the abrasive grains, such as vitrified bond or resin bond. The grinding wheel 14b of the present embodiment includes abrasive grains having an average grain size of 1 μm or more and 20 μm or less, and a vitrified bond, and the concentration of the abrasive grains is 50 or more and 150 or less.

When the average grain size of the abrasive grains in the grinding wheel 14b is smaller than 1 μm, when the protective member 17 is ground with the grinding wheel 14b, clogging tends to occur, and the protective member 17 cannot be properly ground.

On the other hand, when the average grain size of the abrasive grains of the grinding wheel 14b is larger than 20 μm, when the protective member 17 is ground with the grinding wheel 14b, the surface to be ground of the protective member 17 becomes rough.

The roughness of the surface to be ground of the protection member 17 is transferred to the back surface 11b side as unevenness on the back surface 11b when the back surface 11b side of the wafer 11 is ground after the dressing step S50 described later. Therefore, it is preferable that the average grain size of the abrasive grains of the grinding wheel 14b is 1 μm or more and 20 μm or less.

The average particle size in this embodiment is defined as the particle size when the cumulative height becomes 50% in the sedimentation test method (that is, the median diameter or 50% diameter). Note that the average particle size may be defined by the most frequently occurring particle size (ie, the most frequently occurring particle size or mode diameter) in the electrical resistance test method.

The size of the abrasive grains can also be expressed using the particle size defined in JIS R 6001-2:2017. For example, the grinding wheel 14b uses abrasive grains having a grain size of #1000 as defined by the electrical resistance test method.

The degree of concentration means the volume of abrasive grains in the grinding wheel 14b. When the degree of concentration is 50, the volume of the abrasive grains in the grinding wheel 14b is 12.5%, and when the degree of concentration is 100, the volume of the abrasive grains in the grinding wheel 14b is 25%.

Further, in the case of a concentration level of 150, the volume of the abrasive grains in the grinding wheel 14b is 37.5%. In this way, the degree of concentration in the grinding wheel 14b linearly increases as the volume of the abrasive grains in the grinding wheel 14b increases.

Next, with reference to FIGS. 3 to 6, a method of processing the protective member 17 and the grinding wheel 14b after the pasting step S10 will be described. FIG. 3 is a diagram showing the back side holding step S20. In addition, in FIG. 3, the wafer unit 19 is shown in cross section for convenience of explanation.

In the backside holding step S20, the backside 11b side of the wafer 11 is suction-held by the holding surface 4a of the chuck table 4 disposed in the loading/unloading area A1, thereby exposing the other side 17d of the protection member 17. After the back side holding step S20, the chuck table 4 is moved to the grinding area A2.

Then, while supplying grinding water (not shown) such as pure water to the region to be ground and the grinding wheel 14b at a predetermined flow rate, the other surface 17d side of the protective member 17 is ground by the grinding wheel 14b. (flattening step S30, see FIG. 4).

In the flattening step S30, for example, grinding water is supplied to the processing point from a not-shown nozzle (so-called internal nozzle) arranged between the grinding wheel 14 and the holding surface 4a, and further, the wheel base Grinding water (so-called wheel grinding water) is supplied at 4 L/min from a plurality of nozzles (not shown) formed on the inner peripheral side of the grinding wheel 14b along the circumferential direction of the grinding wheel 14a.

In addition to the grinding water, a predetermined high pressure (for example, 10 MPa) and a predetermined pressure are applied to one or more grinding wheels 14b located outside the chuck table 4 from below the grinding wheel 14 toward the grinding wheels 14b. The lower surface side of the grinding wheel 14b may be cleaned by spouting grinding water at a flow rate (for example, 4 L/min).

FIG. 4 is a diagram showing the planarization step S30. Note that FIG. 4 also shows the wafer unit 19 in cross section. In the flattening step S30, only the base material layer 17a of the protection member 17 is ground with the grinding wheel 14.

For example, the other surface 17d side of the protective member 17 is ground by 5 μm or more and less than 500 μm, and the degree of unevenness 17e on the other surface 17d side measured by arithmetic mean roughness (Rz) is set to 10 μm or less. The processing conditions in the planarization step S30 are set as follows, for example.

Grinding feed speed: 0.3μm/s
Spindle rotation speed: 2500rpm
Chuck table rotation speed: 300 rpm
Load current of motor driving spindle: 10A

After the planarization step S30, as shown in FIG. 5, the chuck table 4 is returned to the loading/unloading area A1, and the operator manually turns the wafer unit 19 upside down. Then, the other surface 17d of the ground protection member 17 is suction-held by the holding surface 4a (reversing step S40).

FIG. 5 is a diagram showing the reversal step S40. In addition, in FIG. 5, the wafer unit 19 suction-held by the holding surface 4a is shown in cross section. After the reversing step S40, as shown in FIG. 6, the wafer unit 19 is returned to the grinding area A2.

Then, by bringing the grinding wheel 14b into contact with the back surface 11b of the wafer 11 and grinding it, the grinding wheel 14b is dressed (dressing step S50, see FIG. 6). In addition, grinding water is also supplied to the processing point in the dressing step S50.

For example, grinding water is supplied from an internal nozzle (not shown) to the processing point at a rate of 4 L/min, and wheel grinding water is supplied to the processing point from the wheel base 14a at a rate of 4 L/min. FIG. 6 is a diagram showing the dressing step S50. The dressing conditions are set as follows, for example.

Grinding feed speed: 1.0μm/s
Spindle rotation speed: 1000rpm
Chuck table rotation speed: 300 rpm
Load current of motor driving spindle: 13A

By the way, the dressing board normally used for dressing the grinding wheel 14b has abrasive grains such as white alundum (WA) or green carbon (GC) fixed to a bond material such as vitrified bond or resin bond. ing.

If the bonding material of the dressing board and the bonding material of the grinding wheel 14b are different materials, when the dressing board is used to dress the grinding wheel 14b, the bonding material of the dressing board will adhere to the grinding wheel 14b.

However, in this embodiment, the dressing is applied to the grinding wheel 14b without using a dressing board, which can cause problems when the bonding material of the dressing board and the bonding material of the grinding wheel 14b are different. It is possible to prevent the bond material from adhering to the grinding wheel 14b.

Furthermore, when the wafer 11 is ground with the grinding wheel 14b after dressing, it is possible to prevent the bonding material of the dressing board, which is different from the bonding material of the grinding wheel 14b, from adhering to the wafer 11.

In this way, it is possible to prevent the grinding wheel 14b and the wafer 11 from being contaminated by different types of bond materials. Furthermore, contamination of the grinding wheel 14b and the wafer 11 by different types of abrasive grains can also be prevented.

In addition, since dressing can be performed by simply turning the wafer unit 19 upside down in the turning step S40, a dressing board becomes unnecessary. Furthermore, there is also the advantage that there is no need to transport, manage, etc. the dressing board.

Further, in the dressing step S50, in addition to dressing the grinding wheel 14b, the back surface 11b side of the wafer 11 can be ground to thin the wafer 11. In other words, dressing and grinding of the wafer 11 can be performed at the same time.

(Second Embodiment) Next, a second embodiment will be described. FIG. 7 is a flow diagram of the processing method in the second embodiment. In the second embodiment, the dummy wafer 21 is used instead of the wafer 11 in the dressing step S50 (see FIG. 8).

The dummy wafer 21 is a single crystal substrate formed of the same semiconductor material (ie, the same material) as the single crystal substrate constituting the wafer 11, and the devices 15 are not formed thereon. Note that in this embodiment, being formed of the same semiconductor material (that is, the same material) means that the main components are the same material.

Since the wafer 11 of this embodiment has a silicon single crystal substrate, a silicon single crystal substrate having the same main component (that is, silicon) is used as the dummy wafer 21.

By the way, the dummy wafer 21 may be a mirror wafer in which at least one of the one surface 21a and the other surface 21b located on the opposite side to the one surface 21a is mirror-finished.

In the second embodiment, since the dressing step S50 is performed using the dummy wafer 21, instead of the reversing step S40, the wafer unit 19 placed in the loading/unloading area A1 is replaced with a dummy wafer 21 having approximately the same diameter as the wafer 11. A replacement step S42 is performed.

In the replacement step S42, one surface 21a side of the dummy wafer 21 is suction-held by the holding surface 4a. After the replacement step S42, the grinding wheel 14b is brought into contact with the other surface 21b of the dummy wafer 21 and ground, thereby dressing the grinding wheel 14b.

FIG. 8 is a diagram showing the dressing step S50 in the second embodiment. Note that FIG. 8 also shows a cross-sectional view of the dummy wafer 21 held by suction on the holding surface 4a.

In the second embodiment as well, adhesion of the bond material of the dressing board to the grinding wheel 14b can be prevented. Furthermore, in grinding the wafer 11 after dressing, adhesion of the bond material of the dressing board, which is different from the bond material of the grinding wheel 14b, to the wafer 11 can be prevented.

(Third Embodiment) Next, a third embodiment will be described. FIG. 9 is a flowchart of the processing method in the third embodiment. In the third embodiment, an automatic type and infeed grinding type grinding apparatus 20 is used in which a transfer robot 30 or the like automatically transfers, reverses, etc. the wafer 11 (see FIG. 10).

FIG. 10 is a top view schematically showing a grinding device 20 used in the third embodiment. Note that the X-axis direction, Y-axis direction, and Z-axis direction shown in FIG. 10 are orthogonal to each other. For example, the XY plane is substantially parallel to the horizontal plane, and the Z-axis direction is parallel to the vertical direction.

The grinding device 20 has a base 24 that is rectangular in top view. On the front side (one side in the Y-axis direction) of the base 24, cassette mounting tables 26a and 26b are provided along the X-axis direction. Cassettes 28a each containing a plurality of wafer units 19 before grinding are placed on the cassette mounting table 26a.

Further, cassettes 28b for accommodating a plurality of wafer units 19 after grinding are placed on the cassette mounting table 26b. A transfer robot 30 is provided on the rear side (the other side in the Y-axis direction) of the cassette mounting tables 26a and 26b.

The base portion of the transfer robot 30 is configured to be movable along the X-axis direction and the Z-axis direction. A multi-joint link structure is provided on the base. A wrist portion 30b is provided at the tip of the uppermost link.

The wrist section 30b is provided with a hand section 30a that can suction and hold the wafer unit 19 in a non-contact manner. A plurality of Bernoulli chucks (also called Bernoulli pads) are provided on one surface of the hand section 30a, and this surface functions as a suction surface 30a ₁ (see FIG. 11(B)) that holds the wafer unit 19 under suction.

The hand portion 30a is rotated around a predetermined rotation axis by a rotational drive source (not shown) disposed within the wrist portion 30b. That is, the suction surface _30a1 of the hand portion 30a can be turned upside down.

A disk-shaped temporary stand 30c is provided on one side of the base 24 in the X-axis direction (left side in FIG. 10). When viewed from above, the diameter of the temporary stand 30c is smaller than the gap _30a2 provided in the hand portion 30a. The temporary stand 30c is used, for example, when turning the wafer unit 19 upside down or when aligning the wafer unit 19.

The transport robot 30 not only accesses the cassettes 28a and 28b, but also accesses a disc-shaped turntable 32 provided on the rear side of the base 24. The turntable 32 can be rotated both clockwise and counterclockwise when viewed from above.

The upper surface of the turntable 32 is divided into four fan-shaped areas (carrying in/out area B1, protection member grinding area B2, rough grinding area B3, and finish grinding area B4) each having a center angle of about 90 degrees. A disk-shaped chuck table 34 is provided in the area.

The structure of each chuck table 34 is substantially the same as the chuck table 4. The upper surface of the porous plate and the upper surface of the frame in each chuck table 34 function as a holding surface 34a that holds the wafer unit 19 under suction.

Each chuck table 34 is rotatable around a predetermined rotation axis (not shown), similar to the rotation axis 6 of the chuck table 4. A protection member grinding unit 36 for grinding the protection member 17 is provided above the protection member grinding region B2.

The configuration of the protective member grinding unit 36 is similar to the grinding unit 8 used in the flattening step S30 of the protective member 17. The above-described grinding wheel 14 is attached to the lower end of the spindle (not shown) of the protection member grinding unit 36 .

A rough grinding unit 38 is provided above the rough grinding area B3. The configuration of the rough grinding unit 38 is also similar to that of the grinding unit 8. However, a rough grinding wheel (first grinding wheel) 44 is attached to the lower end of the spindle 40 of the rough grinding unit 38 via a mount 42 (see FIG. 12).

The rough grinding wheel 44 has an annular wheel base 44a made of metal such as aluminum alloy. The upper surface side of the wheel base 44a is fixed to the lower surface side of the mount 42.

On the lower surface side of the wheel base 44a, a plurality of segment-shaped rough grinding wheels (first grinding wheels) 44b are arranged annularly along the circumferential direction of the wheel base 44a. When the spindle 40 is rotated, an annular grinding surface 44c is formed by the trajectory of the lower surface of the plurality of rough grinding wheels 44b.

The rough grinding wheel 44b includes abrasive grains made of diamond, cBN (cubic boron nitride), or the like, and a bond material for fixing the abrasive grains, such as vitrified bond or resin bond.

The rough grinding wheel 44b of this embodiment has abrasive grains with a larger average grain size than the average grain size of the grinding wheel 14b that grinds the protection member 17. For example, the rough grinding wheel 44b uses abrasive grains having a grain size of #400, #500, or #600 as defined by the electrical resistance test method of JIS R 6001-2:2017.

A finish grinding unit 48 is provided above the finish grinding area B4. The configuration of the finish grinding unit 48 is also similar to that of the grinding unit 8. However, a finish grinding wheel (second grinding wheel) 54 is attached to the lower end of the spindle 50 of the finish grinding unit 48 via a mount 52 (see FIG. 13).

The finishing grinding wheel 54 has an annular wheel base 54a made of metal such as aluminum alloy. The upper surface side of the wheel base 54a is fixed to the lower surface side of the mount 52.

On the lower surface side of the wheel base 54a, a plurality of segment-shaped finish grinding wheels (second grinding wheels) 54b are arranged annularly along the circumferential direction of the wheel base 54a. When the spindle 50 is rotated, an annular grinding surface 54c is formed by the trajectory of the lower surface of the plurality of finish grinding wheels 54b.

The finishing grinding wheel 54b includes abrasive grains made of diamond, cBN (cubic boron nitride), etc., and a bond material for fixing the abrasive grains, such as vitrified bond or resin bond. The finishing grinding wheel 54b of this embodiment has abrasive grains having an average particle size smaller than the average particle size of the grinding wheel 14b that grinds the protection member 17.

For example, the finish grinding wheel 54b uses abrasive grains having a grain size of #6000 or #8000 as defined by the electrical resistance test method of JIS R 6001-2:2017. As an example of a preferred embodiment, the finish grinding wheel 54b has an average grain size of 1 μm or less.

A spinner cleaning device 60 is provided on the front side of the temporary storage stand 30c. The processed wafer unit 19 is transported by a transport unit 62 provided on one side of the base 24 in the X-axis direction from the chuck table 34 arranged in the loading/unloading area B1 to the spinner cleaning device 60.

In addition, in FIG. 10, the transport unit 62 is shown by a broken line for convenience of explanation. The transport pad 62a that holds the wafer unit 19 under suction is configured to be movable along the X-axis direction, the Y-axis direction, and the Z-axis direction.

The wafer 11 cleaned by the spinner cleaning device 60 is transferred from the spinner cleaning device 60 to the cassette 28b by the transfer robot 30. Next, a method of processing the wafer 11, the protection member 17, and the grinding wheel 14b will be described with reference to FIG.

The wafer unit 19 formed through the pasting step S10 is housed in the cassette 28a. The transfer robot 30 accesses the cassette 28a, holds the protection member 17 side under suction, and transfers the wafer unit 19 to the chuck table 34 arranged in the carry-in/out area B1.

After the wafer unit 19 is transported to the chuck table 34 arranged in the loading/unloading area B1 so that the back side 11b of the wafer 11 is in contact with the holding surface 34a, the back side 11b is held by suction (back side holding step S20). . At this time, the other surface 17d of the protection member 17 is exposed upward.

After the back side holding step S20, the turntable 32 is rotated 90 degrees clockwise when viewed from above. Then, using the protection member grinding unit 36, the above-described flattening step S30 is performed. After the planarization step S30, an inversion step S40 is performed in which the wafer unit 19 is turned upside down.

In the reversing step S40, first, by rotating the turntable 32 90 degrees counterclockwise when viewed from above, the chuck table 34, which is suctioning and holding the wafer unit 19 after the planarization step S30, is returned to the loading/unloading area B1. .

Then, the transport unit 62 suction-holds the protection member 17 side of the wafer unit 19, and transports the wafer unit 19 from the chuck table 34 disposed in the carry-in and carry-out area B1 to the temporary storage table 30c. FIG. 11A is a side view showing the wafer unit 19 placed on the temporary stand 30c.

As shown in FIG. 11(A), the wafer unit 19 is placed on the temporary stand 30c so that the other flattened surface 17d is exposed upward. Next, as shown in FIG. 11(B), the hand portion 30a whose orientation is adjusted so that the suction surface _30a1 faces upward is placed below the wafer unit 19.

Then, the back surface 11b side of the wafer 11 is held by suction using the suction surface _30a1 . FIG. 11(B) is a side view showing the wafer unit 19 whose back surface 11b side is held under suction by the hand portion 30a. The hand section 30a moves upward while sucking and holding the wafer unit 19, and also turns the wafer unit 19 upside down.

Then, the transfer robot 30 transfers the wafer unit 19 to the chuck table 34 arranged in the carry-in/out area B1, as shown in FIG. 11(C). FIG. 11C is a side view showing the wafer unit 19 being transported to the chuck table 34 arranged in the carry-in/out area B1.

Note that the above-mentioned reversing step S40 is an example. For example, in the reversing step S40, a dedicated reversing mechanism (not shown) may be used to hold the wafer unit 19 on the chuck table 34 disposed in the carry-in/unload area B1 and turn it upside down.

In any case, after the reversing step S40 is completed, the front surface 11a side of the wafer 11 in the wafer unit 19 is held by suction via the protection member 17 (front side holding step S44).

After the front side holding step S44, the turntable 32 is rotated 90 degrees clockwise when viewed from above, and the chuck table 34 is placed directly below the protection member grinding unit 36 (protection member grinding region B2). Then, similarly to the first embodiment, a dressing step S50 is performed.

Also in the dressing step S50 of this embodiment, dressing is applied to the grinding wheel 14b of the protection member grinding unit 36 on the back surface 11b side of the wafer 11, thereby preventing the bonding material of the dressing board from adhering to the grinding wheel 14b and the wafer 11. can. In addition, there is also the advantage that a dressing board is not required.

After the dressing step S50, the turntable 32 is rotated 90 degrees clockwise when viewed from above, and the chuck table 34 is placed directly below the rough grinding unit 38 (rough grinding area B3).

Then, while supplying grinding water such as pure water at a predetermined flow rate to the region to be ground and the rough grinding wheel 44b, rough grinding is performed on the back surface 11b side of the wafer 11 with the rough grinding wheel 44 (rough grinding step S60). . FIG. 12 is a diagram showing the rough grinding step S60. The processing conditions in the rough grinding step S60 are set as follows, for example.

Grinding feed speed: 1μm/s or more and 10μm/s or less Spindle rotation speed: 1000rpm or more and 3500rpm or less Chuck table rotation speed: 10rpm or more and 500rpm or less Load current of the motor that drives the spindle: 6A or more and 20A or less

After the rough grinding step S60, the turntable 32 is rotated 90 degrees clockwise when viewed from above, and the chuck table 34 is placed directly below the finish grinding unit 48 (finish grinding area B4).

Then, while supplying grinding water such as pure water at a predetermined flow rate to the area to be ground and the finish grinding wheel 54b, finish grinding is performed on the back surface 11b side of the wafer 11 with the finish grinding wheel 54 (finish grinding step S70). . FIG. 13 is a diagram showing the finish grinding step S70. The processing conditions in the finish grinding step S70 are set as follows, for example.

Grinding feed speed: 0.5μm/s
Spindle rotation speed: 3000rpm
Chuck table rotation speed: 300 rpm
Load current of motor driving spindle: 10A

Through the rough grinding step S60 and the final grinding step S70, the wafer 11 is thinned to a predetermined thickness (for example, 100 μm). After the final grinding step S70, the turntable 32 is rotated 270 degrees counterclockwise when viewed from above and returned to the loading/unloading area B1.

Then, the transport unit 62 transports the thinned wafer unit 19 to the spinner cleaning device 60. After cleaning in the spinner cleaning device 60, the transfer robot 30 transfers the wafer unit 19 whose back surface 11b side has been cleaned to the cassette 28b.

In the third embodiment, the flattening step S30 of the protective member 17 can be performed before the rough grinding step S60, so that in the rough grinding step S60, the other surface 17d side of the protective member 17 that has been made substantially flat is It can be held by suction with the chuck table 34.

Thereby, the flatness of the back surface 11b side can be improved compared to the case where the flattening step S30 is performed after the rough grinding step S60 and before the final grinding step S70. Furthermore, in the dressing step S50 after the planarization step S30, the back surface 11b side is ground with the grinding wheel 14b, so the volume of the wafer 11 to be ground in the rough grinding step S60 and the final grinding step S70 can be reduced.

By the way, when performing the flattening step S30 after the rough grinding step S60 and before the finish grinding step S70, the reversing step is required twice, but the third embodiment has the advantage that the reversing step only needs to be performed once. There is.

(Fourth Embodiment) Next, a fourth embodiment will be described. In the fourth embodiment, similarly to the second embodiment, a dummy wafer 21 is used in the dressing step S50. The dummy wafer 21 is placed on a chuck table 34 different from the wafer unit 19.

Thereby, the dressing step S50 can be performed using the dummy wafer 21 during the reversing step S40 of the wafer unit 19, during the rough grinding step S60 or finish grinding step S70 of the wafer 11, during spinner cleaning of the wafer 11, and the like. The dummy wafer 21 may be continuously held under suction by an arbitrary chuck table 34 until the thickness reaches the usable limit.

(Fifth Embodiment) Next, a fifth embodiment will be described. FIG. 14 is a flow diagram of the processing method in the fifth embodiment. In the fifth embodiment, similarly to the third embodiment, the dressing step S50 is performed using the back surface 11b side of the wafer 11.

However, the fifth embodiment is different from the third embodiment in that the back side holding step S28, the flattening step S30, the dressing step S50, etc. are performed after the rough grinding step S24 and before the finish grinding step S70. Different from the form.

As shown in FIG. 14, after the pasting step S10, the front surface 11a side of the wafer unit 19 is suction-held via the protective member 17 on the chuck table 34 disposed in the loading/unloading area B1 (front side holding step). S22).

After the front side holding step S22, rough grinding is performed on the back surface 11b side (rough grinding step S24). After the rough grinding step S24, the wafer unit 19 is turned upside down using, for example, the transport robot 30, the temporary stand 30c, and the transport unit 62 (reversal step S26).

Next, the back side 11b is held by suction with the chuck table 34 arranged in the carry-in/out area B1 (back side holding step S28). Thereafter, the degree of unevenness 17e on the other surface 17d of the exposed protection member 17 is reduced (flattening step S30).

After the planarization step S30, the reversing step S40 is performed again, and the front surface 11a side of the wafer 11 is suction-held via the protective member 17 with the chuck table 34 arranged in the loading/unloading area B1 (front side holding step S44). .

After the front side holding step S44, a dressing step S50 using the protection member grinding unit 36 and a finish grinding step S70 using the finish grinding unit 48 are performed in sequence.

In the fifth embodiment as well, adhesion of the bonding material of the dressing board to the grinding wheel 14b and the wafer 11 can be prevented. Note that in the fifth embodiment as well, the dummy wafer 21 can be used as in the fourth embodiment.

By the way, in the third to fifth embodiments described above, an example was described in which the grinding device 20 having three grinding units (so-called triaxial type) is used. However, a grinding device having two grinding units (so-called two-axis type) may also be used.

In this case, the final grinding unit 48 is omitted and the protective member grinding unit 36 used for flattening the protective member 17 is used to perform the flattening step S30 and the final grinding step S70. In addition, the structure, method, etc. according to the above-described embodiments can be modified and implemented as appropriate without departing from the scope of the objective of the present invention.

For example, each of the embodiments described above is not limited to the wafer 11 having the devices 15 and the like. After attaching one side 17c of the protective member 17 to the front surface 11a side of the wafer 11 which does not have devices 15 etc. and has a substantially flat surface 11a, the other side 17d of the protective member 17 is ground. The degree of the unevenness 17e on the side of the surface 17d may be reduced.

Thereby, for example, the degree of unevenness 17e on the other surface 17d side, which is 3 μm or more and 6 μm or less, can be reduced to 1 μm or less. By flattening the protection member 17 in this way, processing accuracy such as grinding can be improved in subsequent processes.

2: Grinding device, 4: Chuck table, 4a: Holding surface 6: Rotating axis, 8: Grinding unit, 10: Spindle, 12: Mount 11: Wafer, 11a: Front surface, 11b: Back surface, 13: Planned dividing line, 15 : Device 14: Grinding wheel, 14a: Wheel base 14b: Grinding wheel (grinding wheel for grinding protective member), 14c: Grinding surface 17: Protective member, 17a: Base material layer, 17b: Adhesive layer 17c: One surface, 17d : Other side, 17e: Unevenness, 19: Wafer unit 20: Grinding device, 24: Base 21: Dummy wafer, 21a: One side, 21b: Other side 26a, 26b: Cassette mounting stand, 28a, 28b: Cassette 30: Transport Robot, 30a: Hand part _30a1 : Suction surface, _30a2 : Gap, 30b: Wrist part, 30c: Temporary stand 32: Turn table, 34: Chuck table, 34a: Holding surface 36: Protective member grinding unit 38: Rough Grinding unit, 40: Spindle, 42: Mount 44: Rough grinding wheel (first grinding wheel), 44a: Wheel base 44b: Rough grinding wheel (first grinding wheel), 44c: Grinding surface 48: Finish grinding unit , 50: Spindle, 52: Mount 54: Finish grinding wheel (second grinding wheel), 54a: Wheel base 54b: Finish grinding wheel (second grinding wheel), 54c: Grinding surface 60: Spinner cleaning device, 62 : Transport unit A1: Carrying in/out area, A2: Grinding area B1: Carrying in/out area, B2: Protective member grinding area B3: Rough grinding area, B4: Finish grinding area S10: Pasting process S20: Back side holding process, S22: Front side holding process, S24: Rough grinding process S26: Reversing process, S28: Back side holding process S30: Flattening process S40: Reversing process, S42: Replacement process, S44: Front side holding process S50: Dressing process, S60: Roughing Grinding process, S70: Finish grinding process

Claims (3)

A method for processing a protective member and a grinding wheel attached to the front side of a wafer, the method comprising:
a back side holding step of holding the back side of the wafer on a chuck table to expose the other side of the protection member with one side attached to the front side;
After the back side holding step, a flattening step of reducing the degree of unevenness on the other side of the protective member by grinding the other side of the protective member with the grinding wheel;
After the planarization step, the grinding wheel is dressed by bringing the grinding wheel into contact with the back side of the wafer or a single crystal substrate formed of the same material as the single crystal substrate constituting the wafer. dressing process,
A processing method characterized by comprising: 1. The grinding wheel has abrasive grains having an average grain size of 1 μm or more and 20 μm or less, and a vitrified bond, and the concentration of the abrasive grains in the grinding wheel is 50 or more and 150 or less. Processing method described. A method for processing a wafer, a protective member, and a grinding wheel for grinding the protective member,
an attaching step of attaching one side of the protective member to the front side of the wafer;
a rough grinding step of roughly grinding the back side of the wafer with a first grinding wheel having a first grinding wheel;
After the rough grinding step, a finish grinding step of performing finish grinding on the back side of the wafer with a second grinding wheel having a second grinding wheel;
Equipped with
Before the rough grinding step or before the finish grinding step,
a back side holding step of holding the back side of the wafer on a chuck table to expose the other side of the protection member;
After the back side holding step, a flattening step of reducing the degree of unevenness on the other side of the protective member by grinding the other side of the protective member with a grindstone for grinding the protective member;
After the planarization step, a grinding wheel for grinding the protection member is brought into contact with the back side of the wafer or a single crystal substrate formed of the same material as the single crystal substrate constituting the wafer, and the grinding wheel is ground. a dressing process of dressing a grinding wheel for grinding the protective member;
A processing method further comprising:

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