JP7770971B2 - Wafer Processing Equipment - Google Patents

Description

The present invention relates to a wafer processing device, and in particular to a wafer processing device capable of performing highly accurate processing such as grinding and polishing on a disk-shaped wafer held on a rotating chuck table.

Conventionally, a known processing device for grinding the surface of a semiconductor wafer (hereinafter simply referred to as "wafer") to make it flat is equipped with a chuck table that holds a disk-shaped wafer by suction and a rotating processing wheel with a grinding wheel that grinds the wafer, and uses the grinding wheel to grind the wafer's surface.

When grinding with this type of grinding device, processing heat accumulated in the grinding wheel and other components is transferred to the chuck table via the wafer. This causes the chuck table to thermally expand, which can interfere with wafer processing, which requires precision measured in microns.

In response to this issue, chuck tables equipped with cooling functions have been proposed. These chuck tables include a disk-shaped chuck (suction plate) on which the wafer is placed, and a cooling device on the backside of the chuck. Furthermore, technology has been proposed to reduce the thermal expansion of the chuck by flowing temperature-controlled water through a flow path inside the chuck (see, for example, Patent Documents 1 and 2).

A technology has also been proposed that reduces the thermal expansion of a chuck by providing a flow path on a chuck base that rotates integrally with the chuck and flowing temperature-controlled water through the flow path on the chuck base (see Patent Document 3).

JP 2014-237200 A Japanese Patent Application Laid-Open No. 2018-27588 JP 2017-69429 A

However, while the technologies described in Patent Documents 1, 2, and 3 can reduce thermal expansion of the chuck, fastening members such as fixing screws that secure the chuck to the chuck base are generally made of different materials than the chuck and chuck base. As a result, heat from the chuck and chuck base is transferred to the fixing screws, and it takes time for the fixing screws to reach approximately the same temperature as the chuck and chuck base, during which time the fixing screws and other components undergo thermal expansion. This thermal expansion of the fixing screws changes the axial force that secures the chuck, resulting in a change in the shape of the chuck. This poses a problem in that accuracy differences are likely to occur between the processing of the first sheet and the processing of the Nth sheet.

Therefore, a technical problem that must be solved is to provide a wafer processing device with a structure that reduces axial force changes and enables high-precision processing by suppressing thermal expansion of the fixing screws that secure the chuck and chuck base, and this is the problem that the present invention aims to solve.

The present invention has been proposed to achieve the above-mentioned object, and the invention described in claim 1 provides a wafer processing apparatus having a chuck table fixed by a plurality of fixing screws between a chuck that holds a wafer by suction and a chuck base that rotates integrally with the chuck, and further comprising: a constant temperature chiller water supply means that supplies constant temperature chiller water to the chuck table to maintain the chuck at a substantially constant temperature; and an annular cover that covers at least substantially the entire outer peripheral side surface of the chuck and stores the constant temperature chiller water discharged from the outer peripheral side surface of the chuck table between the chuck table and the outer peripheral side surface and supplies it to the fixing screws.

With this configuration, the chuck and chuck base are maintained at a constant temperature by supplying constant-temperature chiller water from the constant-temperature chiller water supply means to the chuck table. At the same time, the constant-temperature chiller water supplied to the chuck table is discharged from the outer peripheral side of the chuck table, and the discharged constant-temperature chiller water is received in the gap formed between the chuck table and an annular cover that covers almost the entire outer peripheral side of the chuck table. A predetermined amount of constant-temperature chiller water is then stored in the gap, and the stored constant-temperature chiller water is actively supplied to the fixing screw side, shortening the time it takes for the fixing screw to reach the same temperature as the chuck and chuck table. This minimizes changes in thermal expansion of the fixing screw during processing. This suppresses changes in the axial force that secures the chuck, eliminating differences in processing accuracy between the first and Nth wafers processed, enabling high-precision wafer processing.

The invention described in claim 2 provides a wafer processing device configured as described in claim 1, wherein the cover extends to approximately the same height as the heads of the fixing screws, and the constant temperature chiller water can be stored up to a position where the heads of the fixing screws are immersed in the constant temperature chiller water.

With this configuration, the cover extends to the height of the fixing screws, so the constant-temperature chiller water received in the gap between the annular cover and the chuck table is collected up to a level where the heads of the fixing screws are submerged. Therefore, the constant-temperature chiller water received in the gap between the annular cover and the chuck table comes into direct contact with the fixing screws through the heads of the fixing screws, allowing for active temperature regulation of the fixing screws.

The invention described in claim 3 provides a wafer processing device having the configuration described in claim 1 or 2, wherein the chuck has a slit that extends from the outer peripheral side surface of the chuck to the inner peripheral side surface of the mounting hole into which the fixing screw is attached.

With this configuration, the constant-temperature chilled water received in the gap between the annular cover and the chuck table passes through the slit and directly contacts the outer circumferential side of the fixing screw, pooling up to the top of the fixing screw. Therefore, the constant-temperature chilled water received in the gap between the annular cover and the chuck table passes through the slit and directly contacts the fixing screw, from the outer circumferential side to the head, which is screwed into the threaded hole, allowing for active temperature regulation of the fixing screw.

According to the present invention, constant-temperature chiller water is supplied from a constant-temperature chiller water supply means to the chuck table, maintaining the chuck at a constant temperature. At the same time, the constant-temperature chiller water supplied to the chuck table is discharged from the outer peripheral side of the chuck table, and the discharged constant-temperature chiller water is received in a gap formed between the chuck table and an annular cover that covers substantially the entire outer peripheral side of the chuck table. The constant-temperature chiller water received in the gap is supplied to the fixing screw, actively adjusting the temperature of the fixing screw to be substantially the same as the constant-temperature chiller water. This shortens the time it takes for the fixing screw to reach the same temperature as the chuck and chuck table. Furthermore, thermal expansion changes in the fixing screw during processing can be minimized. This suppresses changes in the axial force that secures the chuck, maintaining a substantially constant chuck shape. This eliminates precision differences between the processing of the first wafer and the processing of the Nth wafer, enabling high-precision wafer processing.

1A and 1B are schematic diagrams showing the main configuration of a rotation mechanism in a wafer processing apparatus according to an embodiment of the present invention, in which FIG. 1A is a perspective view of the rotation mechanism, and FIG. 1B is a cross-sectional view taken along line A-A in FIG. 10 is a structural explanatory diagram of a constant temperature control passage formed in a chuck base in the rotation mechanism of the same. FIG. 2A and 2B are enlarged views of a portion of the rotation mechanism shown in FIG. 1, in which FIG. 2A is a perspective view thereof and FIG. 2B is a cross-sectional view taken along line BB of FIG. 4A and 4B are enlarged partial views showing a modified example of the rotation mechanism shown in FIG. 3, in which FIG. 4A is a perspective view thereof, and FIG. 4B is a cross-sectional view taken along line CC of FIG.

The present invention aims to provide a wafer processing device with a structure that reduces axial force changes and enables high-precision processing by suppressing thermal expansion of the fixing screws that secure the chuck and chuck base. This is achieved by providing a wafer processing device that includes a chuck table secured by multiple fixing screws between a chuck that suction-holds a wafer and a chuck base that rotates integrally with the chuck, and an annular cover that covers at least substantially the entire outer peripheral side of the chuck, and that stores the constant-temperature chiller water discharged from the outer peripheral side of the chuck table between the chuck and the outer peripheral side of the chuck and supplies it to the fixing screws.

An example of an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. Note that in the following example, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is clearly limited to a specific number in principle, the number is not limited to that specific number and may be greater than or less than the specific number.

In addition, when referring to the shape or positional relationship of components, etc., this includes things that are substantially similar or approximate to that shape, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

In addition, drawings may exaggerate characteristic parts to make their features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

In addition, in the following description, expressions indicating directions such as up/down, left/right, etc. are not absolute and are appropriate when each part of the wafer processing apparatus of the present invention is in the orientation depicted, but if that orientation changes, they should be interpreted differently in accordance with the change in orientation. Furthermore, the same symbols are used for the same elements throughout the description of the embodiments.

Below, a preferred embodiment of a wafer processing device according to the present invention will be described in detail with reference to Figures 1 to 3, taking as an example a case in which the device is applied to a grinding device that processes the surface of a wafer to make it flat.

Figure 1 shows a schematic diagram of the main components of the rotation mechanism 10 in a wafer processing device according to the present invention, with (A) being a perspective view of the rotation mechanism 10 and (B) being a cross-sectional view taken along line A-A in (A). The wafer processing device has the rotation mechanism 10 attached to the device body 11. The entire wafer processing device is controlled in accordance with a predetermined procedure by a program in the control device 50.

The rotation mechanism 10 has a chuck table 12 that holds a wafer (not shown) and rotates horizontally. The chuck table 12 holds the wafer and is positioned below the grinding unit (not shown), where the wafer is brought into contact with the rotating grinding wheel of the grinding unit to grind the wafer's surface.

The chuck table 12 includes a disk-shaped chuck base 14 that is rotatably mounted via a rotary joint 13, a similarly disk-shaped chuck 15 that is mounted on the chuck base 14 so that it can rotate integrally with the chuck base 14, and a constant temperature control unit 16 that is provided on the chuck base 14 and positioned between the chuck 15 and the chuck base 14. The chuck 15 and chuck base 14 are fixed together with a fixing screw 17, which is a fastening member.

The chuck 15 comprises a disk-shaped suction plate 18 and a chuck-side frame 19. The chuck-side frame 19 surrounds the outer peripheral side and bottom surface of the suction plate 18 and is integrated with the suction plate 18. The suction plate 18 is made of a porous holding member, and its upper surface serves as an adsorption surface 18A that holds the wafer by suction. In this embodiment, the chuck-side frame 19 of the chuck 15 is made of alumina (aluminum oxide), and the chuck base 14 and fixing screw 17 are both made of stainless steel (SUS).

The chuck side frame 19 has multiple (eight in this embodiment) mounting holes 20 that penetrate vertically around the outer periphery of the suction plate 18, spaced approximately evenly along the circumference. Meanwhile, the chuck base 14 has the same number of screw holes 33 that correspond to the mounting holes 20 in the chuck side frame 19. The chuck side frame 19 is then placed on the chuck base 14, matching the mounting holes 20 with the screw holes 33. When the chuck side frame 19 is placed on the chuck base 14 and the fixing screws 17 are threaded into the screw holes 33 through the mounting holes 20 from the top of the chuck side frame 19, the chuck 15 and chuck base 14 are fixed together with the center O of the chuck table 12 in the center. A counterbore 20A is provided above the mounting holes 20. A portion of the counterbore 20A is open on the outer periphery of the chuck side frame 19, exposing the side of the fixing screw 17 on the outer periphery of the chuck side frame 19.

The constant temperature control unit 16 is provided on the upper surface of the chuck base 14, facing the chuck 15. The constant temperature control unit 16 is formed as a groove excavated with a U-shaped cross section, and consists of a water channel 21 whose upper surface is covered and blocked by the lower surface (interface) of the chuck 15.

As shown in Figure 3, the water channel 21 consists of multiple concentrically formed annular water channel sections 21A, 21B, 21C, and 21D (four in this embodiment: 21A, 21B, 21C, and 21D), and a communicating water channel section 21E that sequentially connects each of these annular water channel sections 21A, 21B, 21C, and 21D.

Furthermore, the annular water channel portion 21A provided on the central side of the chuck base 14 has a through-hole serving as a water supply port 21F, and the annular water channel portion 21D provided on the outermost periphery of the chuck base 14 has a drain port 21G. The water supply port 21F is connected to the constant temperature chiller water source 23 via a water supply pipe 22 arranged through the rotary joint 13. On the other hand, the drain port 21G opens to the outer periphery of the chuck base 14. Furthermore, a chuck pipe 24 is provided in the center of the chuck base 14. One end of this chuck pipe 24 is connected to the lower end of the suction plate 18.

The constant-temperature chiller water source 23 adjusts the temperature of the constant-temperature chiller water supplied to the water passage 21 to, for example, approximately 30°C, allowing the temperature of the entire chuck 15 to be adjusted to approximately 30°C. Meanwhile, the vacuum source 25 applies a suction force by drawing a vacuum on the suction plate 18 via the chuck piping 24, allowing the wafer W to be adsorbed and held on the suction surface 18A of the suction plate 18.

A ring-shaped base-side frame 26 is attached to the outer periphery of the chuck base 14. The top surface of the base-side frame 26 is slightly lower than the top surface of the chuck base 14, and is set at a height that does not block the front of the drain outlet 21G of the water channel 21. Meanwhile, a labyrinth groove 26A is formed around the entire periphery of the bottom surface of the base-side frame 26, cutting from the bottom surface to the top surface. A portion of a labyrinth cover 30 is positioned in the labyrinth groove 26A, which seals off treated water that attempts to enter the device main body 11 and protects the power unit 29, which includes the motor 29A, power transmission belt 29B, pulleys 29C and 29D, the rotary joint 13, etc.

The chuck-side frame 19 is provided with a ring-shaped cover 27 that covers almost the entire outer circumferential surface of the chuck 15. The cover 27 is made of the same alumina as the chuck-side frame 19, and the inner diameter of the main body 27A is larger than the outer diameter of the chuck 15. A gap is formed between the chuck-side frame 19 and the chuck 15, forming a constant-temperature chiller water reservoir 28 that stores constant-temperature chiller water discharged from the drain outlet 21G. The lower end of the main body 27A has a fixed flange 27B bent outward, and the upper end has a gap-adjusting flange 27C bent inward toward the outer circumferential surface of the chuck 15. The fixed flange 27B is provided with a discharge port 27D that runs from the outer periphery to the inner periphery of the fixed flange 27B. The discharge port 27D is formed as a groove recessed into a substantially U-shaped cross section.

The cover 27 is fixed to the base-side frame 26 with the fixing flange 27B in close contact with the upper surface of the base-side frame 26 by the fixing screws 32. As shown in FIG. 3B, the height H of the cover 27 when fixed to the base-side frame 26 is approximately equal to the height of the heads 17A of the fixing screws 17 that attach the chuck 15 to the chuck base 14. In other words, the cover 27 extends to approximately the same height as the heads 17A of the fixing screws 17. Furthermore, a gap δ1 is provided around the entire periphery between the inner surface of the main body 27A and the outer surface of the chuck base 14 to avoid blocking the drain outlet 21G of the water channel 21. A predetermined gap δ2 is also provided between the inner surface of the gap adjustment flange 27C of the cover 27 and the outer surface of the chuck 15. The gap δ2 between the inner surface of the gap adjustment flange 27C and the outer surface of the chuck 15 functions to facilitate the flow of constant temperature chiller water stored in the constant temperature chiller water storage chamber 28 onto the side of the head 17A of the fixing screw 17 when the water rises, and also to allow overflowing constant temperature chiller water that cannot be completely discharged from the constant temperature chiller water storage chamber 28 through the outlet 27D to escape to the outside of the cover 27 through the gap δ2.

The power unit 29 transmits the rotation of the motor 29A, which rotates under the control of the control device 50, to the chuck table 12 via a power transmission belt 29B stretched between a pulley 29D attached to the output shaft of the motor 29A and a pulley 29C attached to the rotating part of the rotary joint 13, and also rotates the chuck table 12 at a predetermined constant speed.

Next, the operation of the processing device configured in this manner will be explained. First, before grinding begins, constant-temperature chiller water at approximately 30°C is flowed from the constant-temperature chiller water source 23 through the water supply pipe 22 toward the constant-temperature control unit 16. This constant-temperature chiller water enters the water channel 21 from the water supply port 21F, then exits the drain port 21G and is discharged into the constant-temperature chiller water storage chamber 28. The amount of this constant-temperature chiller water discharged is adjusted by the control device 50 so that it is slightly greater than the amount discharged from the discharge port 27D of the cover 27. The entire chuck base 14 and chuck 15 of the chuck table 12 are then adjusted to a temperature approaching approximately 30°C, the same as the constant-temperature chiller water.

The constant-temperature chiller water discharged from the drain outlet 21G accumulates in the constant-temperature chiller water storage chamber 28 and rises within the constant-temperature chiller water storage chamber 28 over time. Because the height of the cover 27 here is extended to approximately the same height as the head 17A of the fixing screw 17, the constant-temperature chiller water discharged into the constant-temperature chiller water storage chamber 28 rises to approximately the top of the head 17A of the fixing screw 17. When the constant-temperature chiller water rises to the side of the head 17A of the fixing screw 17, the side of the head 17A of the fixing screw 17 gradually becomes immersed in the constant-temperature chiller water. As a result, the heat of the constant-temperature chiller water adjusts the temperature of the fixing screw 17 to approximately the same as the constant-temperature chiller water. In other words, the entire chuck table 12 is adjusted to a temperature close to that of the constant-temperature chiller water (30°C).

Also, once the entire chuck table 12, i.e., the chuck base 14, chuck 15, fixing screws 17, etc., have been adjusted to a temperature approximately equal to that of the constant-temperature chiller water, the wafer W is placed on the suction surface 18A of the suction plate 18 of the chuck 15. Then, under the control of the control device 50, the vacuum source 25 applies negative pressure to the suction surface 18A, and the wafer W is suction-held on the suction surface 18A. Thereafter, under the control of the control device 50, the motor 29A is driven to rotate, and the driving force of the motor 29A rotates the chuck table 12. At the same time, the grinding unit (not shown) is driven to grind the surface of the wafer.

During grinding, constant-temperature chiller water at approximately 30°C flows through the water supply pipe 22 from the constant-temperature chiller water source 23 to the constant-temperature control unit 16 in the chuck base 14, maintaining the chuck base 14 and chuck 15 at a constant temperature. The constant-temperature chiller water discharged from the drain outlet 21G and stored in the constant-temperature chiller water storage chamber 28 immerses the sides of the heads 17A of the fixing screws 17, and the heat of the constant-temperature chiller water adjusts the fixing screws 17 to approximately the same temperature as the constant-temperature chiller water. As a result, during grinding, the entire chuck table 12, i.e., the chuck base 14, chuck 15, and fixing screws 17, are each maintained at approximately the same temperature as the constant-temperature chiller water.

Therefore, in the processing apparatus of this embodiment, the chuck 15 and suction plate 18 are maintained at a substantially constant temperature by supplying constant-temperature chiller water from the constant-temperature chiller water source 23, which serves as a constant-temperature chiller water supply means, to the chuck table 12. The constant-temperature chiller water supplied to the chuck table 12 is then discharged from the outer peripheral side of the chuck table 12. The discharged constant-temperature chiller water is then received in the constant-temperature chiller water reservoir 28, which is located between the chuck table 12 and an annular cover 27 that covers the entire outer peripheral side of the chuck table 12. The constant-temperature chiller water stored in the constant-temperature chiller water reservoir 28 actively regulates the temperature of the fixing screw 17. This shortens the time it takes for the fixing screw 17 to reach the same temperature as the chuck 15 and chuck table 12, and minimizes changes in thermal expansion of the fixing screw 17 during processing. This reduces changes in the axial force that secures the chuck 15, thereby maintaining a substantially constant shape of the chuck 15. This eliminates any difference in processing accuracy between the first wafer and the Nth wafer, enabling high-precision wafer processing. Furthermore, any excess constant-temperature chiller water remaining in the gap between the annular cover 27 and the chuck table 12 can be discharged outside the chuck table 12 through the outlet 27D provided in the cover 27 and the gap δ1 provided between the cover 27 and the chuck 15.

Figure 4 is a partially enlarged view showing a modified version of the rotation mechanism 10 shown in Figure 3, with (A) being a perspective view and (B) being a cross-sectional view taken along line C-C in (A). The modified version shown in Figure 4 features a slit 31 cut out of the chuck 15 at the mounting hole 20 on the chuck 15 side, through which the fixing screw 17 securing the chuck 15 to the chuck base 14 passes. The slit 31 extends from the outer peripheral surface of the chuck 15 to the inner peripheral surface of the mounting hole 20, opening into the mounting hole 20. The other components in Figure 4 are the same as those in Figures 1 to 3, so the same reference numerals are used for the same components in Figures 1 to 3, and their explanations will be omitted. Only the structural differences will be described. The opening width of the slit 31 is smaller than the thread diameter of the fixing screw 17 to prevent the fixing screw 17 from slipping out of the slit 31.

In the structure of the rotation mechanism 10 shown in FIG. 4, water is supplied from the constant-temperature chiller water source 23 to the constant-temperature control unit 16 to adjust the temperature of the chuck 15 and chuck base 14. The water is then discharged from the drain outlet 21G of the chuck base 14 and stored in the constant-temperature chiller water storage chamber 28. This water then enters the mounting hole 20 through the slit 31, immersing more of the outer peripheral surface of the fixing screw 17. This actively adjusts the fixing screw 17 to approximately the same temperature as the constant-temperature chiller water using the heat of the constant-temperature chiller water. In this case, the area of the fixing screw 17 immersed in the constant-temperature chiller water is larger than in the structure shown in FIG. 3, which shortens the time it takes for the fixing screw 17 to reach approximately the same temperature as the constant-temperature chiller water. Therefore, the temperatures of the chuck base 14, chuck 15, and fixing screw 17 of the chuck table 12 as a whole approach approximately 30°C, the same as the constant-temperature chiller water, more quickly.

The present invention can be modified in various ways without departing from the spirit of the invention, and it goes without saying that the present invention also covers such modifications.

10: Rotation mechanism 11: Device body 12: Chuck table 14: Chuck base 15: Chuck 16: Constant temperature control unit 17: Fixing screw 17A: Head 18: Suction plate 18A: Suction surface 20: Mounting hole 20A: Counterbore 21: Water channel 21F: Water supply port 21G: Drain port 22: Water supply pipe 23: Constant temperature chiller water source (constant temperature chiller water supply means)
24: Pipe for chuck 25: Vacuum source 26: Base side frame 26A: Groove 27: Cover 27D: Discharge port 28: Constant temperature chiller water storage chamber 31: Slit 33: Screw hole 50: Control device W: Wafer δ1, δ2: Gap

Claims (2)

A wafer processing apparatus including a chuck table fixed by a plurality of fixing screws between a chuck that suction-holds a wafer and a chuck base that rotates integrally with the chuck,
a constant temperature chiller water supply means for supplying constant temperature chiller water to the chuck table to maintain the chuck at a substantially constant temperature;
an annular cover provided to cover at least substantially the entire outer peripheral side surface of the chuck, which stores the constant temperature chiller water discharged from the outer peripheral side surface of the chuck table between the outer peripheral side surface of the chuck table and the chuck table, and supplies the constant temperature chiller water to the fixing screw side;
Equipped with
The wafer processing device is characterized in that the chuck has a slit cut out from the outer peripheral side surface of the chuck to the inner peripheral side surface of the mounting hole into which the fixing screw is attached . The wafer processing device described in claim 1, characterized in that the cover extends to approximately the same height as the heads of the fixing screws and is capable of storing the constant temperature chiller water up to a position where the heads of the fixing screws are immersed in the constant temperature chiller water.