A surface plate cooling structure, a single-sided polishing apparatus, a surface plate cooling method, and a wafer manufacturing method.

Abstract

To provide a surface plate cooling structure which can suppress pressure deformation of a surface plate, while maintaining predetermined cooling capability to the surface plate.SOLUTION: A surface plate cooling structure cools a surface plate of a polishing device for polishing a main surface of a wafer, wherein the surface plate includes a first surface plate where a polishing object is positioned on one surface side, and a second surface plate fixed to the other surface of the first surface plate, a groove for a flow channel constituting a coolant flow channel is formed on at least the one surface plate among the mutually opposite surfaces of the first surface plate and the second surface plate, a supply pipe provided with a supply pump for supplying a coolant to the coolant flow channel is connected to the inlet of the coolant flow channel, and a discharge pipe provided with a discharge pump for discharging the coolant from the coolant flow channel is connected to the outlet of the coolant flow channel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a platen cooling structure, a single-sided polishing apparatus, a platen cooling method, and a wafer manufacturing method.

Background Art

[0002] Conventionally, a polishing apparatus for polishing a wafer has been known (for example, see Patent Document 1). In the polishing apparatus described in Patent Document 1, the lower polishing platen includes a lower polishing plate to which a lower polishing pad is attached, and a member (hereinafter sometimes referred to as a "lower platen base member") fixed to the lower side of the lower polishing plate. The upper polishing platen includes an upper polishing plate to which an upper polishing pad is attached, and a member (hereinafter sometimes referred to as an "upper platen base member") fixed to the upper side of the upper polishing plate. The lower polishing platen is provided with a lower coolant flow path formed by a flow path groove formed in the lower platen base member and the lower polishing plate that closes the upper side of the flow path groove. The upper polishing platen is provided with an upper coolant flow path formed by a flow path groove formed in the upper platen base member and the upper polishing plate that closes the lower side of the flow path groove. Coolant is continuously supplied to the upper and lower coolant flow paths by driving one coolant circulation pump.

[0003] In such a polishing apparatus, paying attention to the differences in thermal displacement due to the materials of the upper and lower polishing plates during processing and the upper and lower polishing pads attached to each polishing plate and changes over time during processing, the temperature and flow rate of the coolant supplied to each polishing plate, and, additionally, the flow rate and temperature of the polishing agent are controlled so that the surface of the polishing pad that affects the accuracy after processing always maintains a flat surface. For example, in order to increase the flow rate of the coolant for the purpose of increasing the cooling capacity, it is necessary to increase the discharge pressure of the coolant circulation pump.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] In the polishing apparatus described in Patent Document 1, the hydraulic pressure on the downstream side of each coolant flow path (hereinafter sometimes referred to as the "downstream side of the flow path") is lower than the hydraulic pressure on the upstream side (hereinafter sometimes referred to as the "upstream side of the flow path") due to pressure loss. In this case, the difference in the force exerted by the hydraulic pressure on each polishing plate between the upstream side of the flow path and the downstream side of the flow path may cause pressure deformation of each polishing plate, potentially resulting in differences in the flatness of each polishing plate.

[0006] The present invention aims to provide a surface plate cooling structure, a single-sided polishing apparatus, a surface plate cooling method, and a wafer manufacturing method that can suppress pressure deformation of the surface plate while maintaining a predetermined cooling capacity for the surface plate. [Means for solving the problem]

[0007] The surface plate cooling structure of the present invention is a surface plate cooling structure for a polishing apparatus that polishes the main surface of an object to be polished, wherein the surface plate comprises a first surface plate on which the object to be polished is located on one side, and a second surface plate fixed to the other side of the first surface plate, wherein a flow channel groove constituting a coolant flow channel is formed in at least one of the mutually opposing surfaces of the first surface plate and the second surface plate, a supply pipe equipped with a supply pump for supplying coolant to the coolant flow channel is connected to the inlet of the coolant flow channel, and a discharge pipe equipped with a discharge pump for discharging the coolant from the coolant flow channel is connected to the outlet of the coolant flow channel.

[0008] In the platen cooling structure of the present invention, it is preferable that a discharge-side hydraulic pressure gauge is provided upstream of the discharge pump in the discharge pipe.

[0009] In the platen cooling structure of the present invention, it is preferable that a supply-side hydraulic pressure gauge is provided downstream of the supply pump in the supply pipe.

[0010] In the surface plate cooling structure of the present invention, it is preferable to further include a control device that controls at least one of the supply pump and the discharge pump such that the liquid pressure measured by the discharge side liquid pressure gauge becomes a first target liquid pressure at which the first surface plate does not undergo pressure deformation, and the liquid pressure measured by the supply side liquid pressure gauge becomes a second target liquid pressure at which the first surface plate does not undergo pressure deformation.

[0011] The present invention relates to a single-sided polishing apparatus for polishing one main surface of a wafer as an object to be polished, comprising: a platen on which a polishing pad is provided on one side; a polishing head that presses the one main surface of the wafer against the polishing pad; a platen cooling structure for cooling the platen; and a rotation drive unit that polishes the one main surface by rotating the platen and the polishing head relative to each other.

[0012] The present invention relates to a surface plate cooling method for a polishing apparatus that polishes the main surface of an object to be polished, wherein the surface plate comprises a first surface plate on which the object to be polished is located on one side, and a second surface plate fixed to the other side of the first surface plate, wherein at least one of the first surface plate and the second surface plate has a channel groove that constitutes a cooling liquid channel, a supply pipe equipped with a supply pump for supplying cooling liquid to the cooling liquid channel is connected to the inlet of the cooling liquid channel, and a discharge pipe equipped with a discharge pump for discharging the cooling liquid from the cooling liquid channel is connected to the outlet of the cooling liquid channel, and the surface plate cooling method comprises a cooling liquid supply step of driving the supply pump and the discharge pump to supply the cooling liquid to the cooling liquid channel, and a pump control step of controlling at least one of the supply pump and the discharge pump so that the liquid pressure in the cooling liquid channel becomes a target liquid pressure that does not cause pressure deformation of the first surface plate.

[0013] In the platen cooling method of the present invention, it is preferable that the pump control step controls at least one of the pumps such that the liquid pressure upstream of the discharge pump in the discharge pipe becomes the first target liquid pressure.

[0014] In the platen cooling method of the present invention, it is preferable that the pump control step controls at least one of the pumps such that the liquid pressure downstream of the supply pump in the supply pipe becomes the second target liquid pressure.

[0015] In the platen cooling method of the present invention, the target liquid pressure is preferably +50kPa or less relative to atmospheric pressure, more preferably less than atmospheric pressure, and even more preferably -50kPa or more relative to atmospheric pressure.

[0016] The wafer manufacturing method of the present invention comprises a step of polishing the wafer, which is the object to be polished, using the polishing apparatus in which the platen has been cooled by the platen cooling method described above. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram showing the configuration of a single-sided polishing apparatus according to the embodiment. [Figure 2] This is a partial longitudinal cross-sectional view showing a surface plate cooling structure according to an embodiment, and is a cross-sectional view along the line II-II in Figures 3 and 4. [Figure 3] This is a cross-sectional view of the first surface plate according to the embodiment, and is a cross-sectional view along the line III-III in Figure 2. [Figure 4] This is a cross-sectional view of the second surface plate according to the embodiment, and is a cross-sectional view along the line IV-IV in Figure 2. [Figure 5] Figures 3 and 4 show cross-sectional views along the line VI-VI according to the embodiment, where (A) shows the state where the fluid pressure in the coolant flow path is at the target fluid pressure, and (B) shows the state where the fluid pressure in the coolant flow path exceeds the target fluid pressure. [Figure 6] This is a flowchart showing the method for manufacturing a wafer according to the embodiment. [Figure 7] This is a flowchart showing the single-sided finishing process according to the embodiment. [Modes for carrying out the invention]

[0018] [Embodiment] <Configuration of a single-sided wafer polishing apparatus> First, the configuration of a single-sided wafer polishing apparatus according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the configuration of a single-sided wafer polishing apparatus. As the single-sided polishing apparatus 1 shown in FIG. 1, one main surface (polishing surface W1) of the wafer W as the polishing object is polished. The single-sided polishing apparatus 1 includes a polishing unit 2 and a control device 7.

[0019] The polishing unit 2 includes a polishing head 21, a head holding unit 22, a head lifting and lowering unit 23, a head driving unit 24 as a rotation driving unit, a lower surface plate 25 as a surface plate, a lower polishing pad 26, a lower surface plate driving unit 27 as a rotation driving unit, a wafer pressing force adjustment unit 28, and a polishing liquid supply unit 29. Note that the number of polishing heads 21 included in the polishing unit 2 may be one, but in this embodiment, a configuration in which the polishing unit 2 includes a plurality of polishing heads 21 is exemplified.

[0020] Each polishing head 21 is formed in a disk shape. Each polishing head 21 holds the surface (back surface) opposite to the polishing surface W1 (surface) of the wafer W due to the surface tension of water or the like. A ring-shaped retainer ring 211 is disposed on the outer peripheral portion of the lower surface of each polishing head 21. The retainer ring 211 contacts the outer peripheral end portion of the wafer W located inside the retainer ring 211 and holds the wafer W so as not to come out of the gap between the polishing head 21 and the lower polishing pad 26. A columnar head rotation shaft member 213 is provided at the center of the upper surface of each polishing head 21.

[0021] The head holding unit 22 holds the upper end side portion of the head rotation shaft member 213 of each polishing head 21 so that the head rotation shaft member 213 can rotate around its axis. The head holding unit 22 holds the head rotation shaft member 213 such that a plurality of polishing heads 21 are arranged at equal intervals on the circumference of a predetermined circle. The head lifting and lowering unit 23 raises and lowers the head holding unit 22. The head drive unit 24 is located inside the head holding unit 22. The head drive unit 24 is composed of, for example, a motor, which rotates the head rotation shaft member 213 connected to the rotation shaft of the motor.

[0022] The lower platen 25 is formed in a disc shape and is positioned below the multiple polishing heads 21. A cylindrical platen rotation shaft member 251 is positioned in the center of the lower surface of the lower platen 25. As will be described in more detail later, the temperature of the lower platen 25 is kept constant by a cooling liquid during the polishing of the wafer W. The lower polishing pad 26 is attached to the upper surface of the lower platen 25. The lower polishing pad 26 is formed in a circular shape that is larger than the wafer W and is configured to polish multiple wafers W held by multiple polishing heads 21 simultaneously.

[0023] The lower platen drive unit 27 is composed of, for example, a motor, and rotates a platen rotation shaft member 251 connected to the rotation shaft of the motor in the same direction as or opposite to the rotation direction of the polishing head 21. The wafer pressure adjustment unit 28 is a fixed pressure type device that adjusts the pressure applied to the wafer W against the lower polishing pad 26. The polishing fluid supply unit 29 supplies a slurry-like polishing fluid to the lower polishing pad 26 via a nozzle 291. Using this polishing fluid, the surface W1 of the wafer W is polished. The control device 7 controls the polishing unit 2.

[0024] <Surface plate cooling structure> Next, the surface plate cooling structure will be described. Figure 2 is a partial longitudinal section view showing the surface plate cooling structure, and is a cross-sectional view along line II-II in Figures 3 and 4. Figure 3 is a cross-sectional view of the first surface plate, and is a cross-sectional view along line III-III in Figure 2. Figure 4 is a cross-sectional view of the second surface plate, and is a cross-sectional view along line IV-IV in Figure 2. Figure 5 is a cross-sectional view along line VI-VI in Figures 3 and 4, where (A) shows the state where the fluid pressure in the coolant flow path is at the target fluid pressure, and (B) shows the state where the fluid pressure in the coolant flow path exceeds the target fluid pressure.

[0025] As shown in Figure 2, the lower base plate 25 comprises a first base plate 31, a second base plate 32, and a pad mounting member 33. The first surface plate 31, the second surface plate 32, and the pad mounting member 33 are formed from, for example, stainless steel, a low-expansion alloy, or ceramic, and are disc-shaped with equal diameters to each other.

[0026] As shown in Figures 2 and 3, a suction groove 34 is formed on the upper surface of the first base plate 31. The suction groove 34 is composed of a circular groove 341 whose center coincides with the center of the first base plate 31, a plurality of radial grooves 342 extending radially from the circular groove 341, and a plurality of ring grooves 343 surrounding the circular groove 341, each having a different inner diameter. The circular groove 341 is provided with a first suction hole 35 that penetrates the first base plate 31.

[0027] As shown in Figures 2 and 4, the upper surface of the second base plate 32 is provided with a flow channel groove 37 formed by a partition wall 36. The partition wall 36 comprises one outer peripheral partition wall 361, a plurality of outer radial partition walls 362, a plurality of inner radial partition walls 363, and one arc-shaped partition wall 364.

[0028] The outer peripheral partition wall 361 is formed in a ring shape along the outer edge of the second surface plate 32. The outer peripheral partition wall 361 has a fitting groove 361A into which the O-ring 38 is fitted. Each outer radial partition wall 362 is formed to extend from different positions on the inner edge of the outer peripheral partition wall 361 toward the center of the second base plate 32 (hereinafter sometimes referred to as the "center of the lower base plate"). Each inner radial partition wall 363 is formed to extend toward the center of the lower platen from a position away from the inner edge of the outer peripheral partition wall 361, between adjacent outer radial partition walls 362. The end of each inner radial partition wall 363 on the lower platen center side is located closer to the lower platen center than the end of each outer radial partition wall 362 on the lower platen center side. The arc-shaped partition wall 364 is formed in an arc shape in which, of the ends on the lower platen side of each inner radial partition wall 363, one adjacent pair of ends is not connected, while the remaining adjacent ends are connected. An outer radial partition wall 362 (hereinafter sometimes referred to as "entrance / exit partition wall 362A") is connected to the center of the arc-shaped partition wall 364, located between a pair of inner radial partition walls 363 that are not connected to the arc-shaped partition wall 364. The entrance / exit partition wall 362A is provided with a second suction hole 364A that penetrates the second platen 32. The area enclosed by the arc-shaped partition wall 364 is divided into two areas by the entrance / exit partition wall 362A. One of the two divided areas is provided with an entrance 39 that penetrates the second platen 32, and the other area is provided with an exit 40 that penetrates the second platen 32.

[0029] The first surface plate 31 and the second surface plate 32 are fixed together by bolts 41 that are screwed into the first surface plate 31, passing through the outer radial partition wall 362 or the inner radial partition wall 363 from below, so that the first suction hole 35 of the first surface plate 31 and the second suction hole 364A of the second surface plate 32 are in communication.

[0030] As shown in Figure 2, the single-sided polishing apparatus 1 further comprises a cooling liquid tank 51, a supply pipe 52, a supply pump 53, a supply-side hydraulic pressure gauge 54, a flow meter 55, a discharge pipe 56, a discharge pump 57, a discharge-side hydraulic pressure gauge 58, a suction pipe 59, and a suction section 60. The coolant tank 51 contains the coolant C and has the function of maintaining the temperature of the coolant C at, for example, between 20°C and 26°C. The supply pipe 52 comprises an upstream supply pipe 521 and a downstream supply pipe 522. One end of the upstream supply pipe 521 is located below the liquid level of the coolant C contained in the coolant tank 51. The other end of the upstream supply pipe 521 and one end of the downstream supply pipe 522 are connected to a rotary joint 61 provided on the base plate rotating shaft member 251. The other end of the downstream supply pipe 522 is fixed to the lower surface of the second base plate 32 such that its interior communicates with the inlet 39. The supply pump 53 is installed in the upstream supply pipe 521. The supply-side hydraulic pressure gauge 54 is installed on the downstream side of the supply pipe 522, below the supply pump 53, in the upstream supply pipe 521, and outputs the measured hydraulic pressure of the upstream supply pipe 521 as gauge pressure (the difference between absolute pressure and atmospheric pressure). The flow meter 55 is installed between the supply pump 53 and the supply side hydraulic pressure gauge 54 in the upstream supply pipe 521, and measures the flow rate of the coolant C flowing through the upstream supply pipe 521.

[0031] The discharge pipe 56 comprises an upstream discharge pipe 561 and a downstream discharge pipe 562. One end of the upstream discharge pipe 561 is fixed to the lower surface of the second base plate 32 such that its interior communicates with the outlet 40. The other end of the upstream discharge pipe 561 and one end of the downstream discharge pipe 562 are connected to a rotary joint 62 provided on the base plate rotating shaft member 251. The other end of the downstream discharge pipe 562 is located inside the coolant tank 51. The discharge pump 57 is installed in the downstream discharge pipe 562. The discharge-side hydraulic pressure gauge 58 is installed on the upstream side of the discharge pipe 561, above the discharge pump 57, in the downstream discharge pipe 562, and outputs the measured hydraulic pressure of the downstream discharge pipe 562 as gauge pressure.

[0032] The suction pipe 59 comprises an upstream suction pipe 591 and a downstream suction pipe 592. One end of the upstream suction pipe 591 is connected to the suction section 60. The other end of the upstream suction pipe 591 and one end of the downstream suction pipe 592 are connected to a rotary joint 63 provided on the base plate rotating shaft member 251. The other end of the downstream suction pipe 592 is fixed to the lower surface of the second base plate 32 such that its interior communicates with the second suction hole 364A.

[0033] The control device 7 is electrically connected to the supply pump 53, the supply side hydraulic pressure gauge 54, the flow meter 55, the discharge pump 57, the discharge side hydraulic pressure gauge 58, and the suction section 60.

[0034] As described above, with the first surface plate 31 and the second surface plate 32 fixed in place, when a pad mounting member 33, on which a lower polishing pad 26 is attached to the upper surface by, for example, double-sided tape, is placed on the first surface plate 31, the suction groove 34 is closed by the pad mounting member 33, forming a suction space 42. When the control device 7 drives the suction unit 60, the air inside the first suction hole 35, the second suction hole 364A, and the suction space 42 is sucked in by the suction unit 60, and the pad mounting member 33, which is integrated with the lower polishing pad 26, is attracted to and fixed to the first surface plate 31. In this way, by configuring the pad mounting member 33, which is integrated with the lower polishing pad 26, to adhere to the first surface plate 31, the lower polishing pad 26 can be easily replaced compared to a configuration in which the lower polishing pad 26 is directly fixed to the first surface plate 31 with double-sided tape.

[0035] As described above, once the first base plate 31 and the second base plate 32 are fixed, a coolant flow path 43 is formed by the flow path groove 37 and the lower surface of the first base plate 31. Here, for example, it is conceivable to use a single disc-shaped member instead of the first base plate 31 and the second base plate 32 and form a coolant flow path inside the disc-shaped member. However, in this case, if foreign matter such as dirt or limescale adheres to the coolant flow path, it becomes difficult to remove such foreign matter. As in this embodiment, by fixing the first base plate 31 and the second base plate 32 so that they can be separated and forming the coolant flow path 43, foreign matter adhering to the coolant flow path 43 can be easily removed. When the control device 7 drives the supply pump 53 and the discharge pump 57, as shown in Figure 2, the supply pump 53 pumps up the coolant C from the coolant tank 51 and supplies it into the coolant flow path 43 via the inlet 39. As shown in Figure 4, the coolant C supplied into the coolant flow path 43 flows along the outer peripheral partition wall 361, the outer radial partition wall 362, the inner radial partition wall 363, and the arc-shaped partition wall 364, covering almost the entire surface of the second base plate 32, and is discharged from the outlet 40. As shown in Figure 2, the coolant C discharged from the outlet 40 is drawn into the discharge pipe 56 by the discharge pump 57 and returned to the coolant tank 51. In this manner, the coolant C circulates between the coolant tank 51, the supply pipe 52, the coolant flow path 43, and the discharge pipe 56. The coolant C flowing through the coolant flow path 43 maintains a constant temperature of the lower platen 25 during wafer polishing, thereby suppressing thermal deformation of the lower platen 25.

[0036] The supply pipe 52, supply pump 53, supply-side hydraulic pressure gauge 54, flow meter 55, cooling liquid passage 43, discharge pipe 56, discharge pump 57, discharge-side hydraulic pressure gauge 58, and control device 7 constitute a platen cooling structure that cools the lower platen 25 during wafer polishing. The hydraulic pressure measured by the supply-side hydraulic pressure gauge 54 (hereinafter sometimes referred to as "supply-side hydraulic pressure") corresponds to the hydraulic pressure on the inlet side 39 (upstream side) of the coolant flow path 43. The hydraulic pressure measured by the discharge-side hydraulic pressure gauge 58 (hereinafter sometimes referred to as "discharge-side hydraulic pressure") corresponds to the hydraulic pressure on the outlet side 40 (downstream side) of the coolant flow path 43. The flow rate measured by the flow meter 55 (hereinafter sometimes referred to as "coolant flow rate") corresponds to the flow rate of the coolant C newly supplied to the coolant flow path 43.

[0037] The control device 7 controls at least one of the supply pump 53 and the discharge pump 57 so that the supply-side fluid pressure becomes the supply-side target fluid pressure (second target fluid pressure) and the discharge-side fluid pressure becomes the discharge-side target fluid pressure (first target fluid pressure), while maintaining a state in which the coolant flow rate falls within the target flow rate range. Controlling the pump here means adjusting the flow rate of the coolant C supplied or discharged from the pump, which can be adjusted to the target flow rate, for example, by adjusting the opening of the pump valve. In the following, the supply-side target fluid pressure and the discharge-side target fluid pressure may be collectively referred to as "target fluid pressure".

[0038] Here, the target hydraulic pressure is set to a pressure at which the lower base plate 25 does not undergo pressure deformation. The portion of the first base plate 31 that is not fixed to the outer radial partition wall 362 or the inner radial partition wall 363 by bolts 41 (hereinafter sometimes referred to as the "unfixed portion") is more susceptible to pressure deformation due to the hydraulic pressure of the coolant C compared to the portion that is fixed by bolts 41 (hereinafter sometimes referred to as the "fixed portion"). The target hydraulic pressure is preferably a predetermined value of +50 kPa or less in gauge pressure. When the hydraulic pressure is +50kPa or less in gauge pressure, the hydraulic pressure in the coolant flow path 43 is not large enough to cause pressure deformation of the first base plate 31, so the non-fixed portion does not undergo pressure deformation, as shown in Figure 5(A). On the other hand, if the hydraulic pressure exceeds +50kPa in gauge pressure, as shown in Figure 5(B), the hydraulic pressure in the coolant flow path 43 may cause the unfixed portion to deform due to pressure, separating it from the second surface platen 32. When the unfixed portion deforms, the lower polishing pad 26 also deforms, reducing the flatness of the wafer W polished by the single-sided polishing device 1. Furthermore, if the unfixed portion deforms and separates from the outer radial partition wall 362 or the inner radial partition wall 363, as shown by the dashed line in Figure 4 and in Figure 5(B), the coolant C flows to the separated portion, causing the temperature distribution of the lower surface platen 25 to become inconsistent.

[0039] Furthermore, it is more preferable that the target hydraulic pressure is a predetermined value less than 0 kPa (negative pressure) in gauge pressure. When the hydraulic pressure is less than 0 kPa in gauge pressure, pressure deformation that would cause the non-fixed portion to separate from the second base plate 32 is reliably suppressed. Furthermore, it is even more preferable that the target hydraulic pressure be a predetermined value of -50 kPa or higher in gauge pressure. If the target hydraulic pressure is less than -50kPa in gauge pressure, the portion of the non-fixed part that is not in contact with the partition wall 36 may be pressure-deformed by the hydraulic pressure of the cooling liquid passage 43, causing it to move closer to the second surface platen 32. When the non-fixed part deforms in this way, the lower polishing pad 26 also deforms, reducing the flatness of the wafer W polished by the single-sided polishing device 1. The supply-side target fluid pressure and the discharge-side target fluid pressure may be the same or different, but it is preferable that they be the same from the viewpoint of eliminating pressure deformation of the lower base plate 25 due to the difference in fluid pressure in the coolant flow path 43.

[0040] The target flow rate range is set by factors such as the number of polishing heads 21. For example, in the single-sided polishing apparatus 1 used in the single-sided polishing process described later, if there are two polishing heads 21, the target flow rate range is set to 20 L / min or more and 50 L / min or less. If the flow rate in the supply pipe 52 is below the lower limit of the target flow rate range, the amount of coolant C newly supplied to the coolant flow path 43 will decrease, which may cause the temperature of the lower base plate 25 to become too high. On the other hand, if the flow rate of the coolant C exceeds the upper limit of the target flow rate range, a large amount of coolant C will be newly supplied to the coolant flow path 43, which may make it difficult to control the temperature of the lower platen 25.

[0041] <Wafer manufacturing method> Next, a wafer manufacturing method including the surface plate cooling method of the present invention will be described. Figure 6 is a flowchart of the wafer manufacturing method. Figure 7 is a flowchart of the single-sided finishing process.

[0042] As shown in Figure 6, the method for manufacturing the wafer W comprises a pulling step (step S1), a block processing step (step S2), a slicing step (step S3), a pretreatment step (step S4), a simultaneous double-sided polishing step (step S5), and a single-sided finishing step (step S6) as a finishing step.

[0043] In step S1, the pulling process, a cylindrical silicon single crystal is pulled from the silicon melt using the Czochralski method. In the block processing step S2, the outer circumference of the single crystal ingot is ground, and notches are made according to the crystal orientation. Then, for example, the single crystal ingot is cut into multiple blocks using a band saw.

[0044] In the slicing process of step S3, the block is sliced ​​into multiple wafers W, for example, with a thickness of about 1 mm, using an internal blade cutting machine or a wire saw. In the pre-treatment step S4, chamfering is performed, and rough polishing (lapping) is carried out using, for example, an alumina abrasive to ensure that both sides of the wafer W are parallel. Then, after etching or other processes as necessary, a planarization process is performed to eliminate irregularities on the surface of the wafer W.

[0045] In the simultaneous double-sided polishing process of step S5, a mirror finish is applied to the pre-treated wafer W to increase its flatness. For example, double-sided polishing is performed using colloidal silica liquid to further increase the flatness and obtain a wafer W with a predetermined flatness. Step S6, the single-sided finishing step, includes the platen cooling method of the present invention. In the single-sided finishing step, the polished surface W1 of the wafer W obtained in the double-sided simultaneous polishing step is polished using the single-sided polishing apparatus 1. By performing polishing in the single-sided finishing step, scratches and damage are removed from the polished surface W1 of the wafer W, and at the same time, the surface roughness of the polished surface W1 can be adjusted. Details of the single-sided finishing process will be described later. The wafers W obtained in the single-sided finishing process are cleaned with, for example, an alkaline solution, and then inspected for surface particles or scratches, as required for quality control. The wafers that pass the inspection are then packaged and shipped.

[0046] Next, we will describe the details of the single-sided finishing process in step S6. As shown in Figure 7, with wafers W held in each polishing head 21, the control device 7 drives the supply pump 53 and the discharge pump 57 to start supplying coolant C to the coolant flow path 43 (coolant supply process: step S11). When the coolant supply process in step S11 is performed such that the measurement results of the supply-side hydraulic pressure gauge 54 and the discharge-side hydraulic pressure gauge 58 reach the target hydraulic pressure, and the measurement result of the flow meter 55 falls within the target flow rate range, as shown in Figures 2, 4, and 5(A), the coolant flow path 43 does not undergo pressure deformation due to the hydraulic pressure, and the coolant C in the coolant tank 51 circulates between the coolant tank 51, the supply pipe 52, the coolant flow path 43, and the discharge pipe 56. In addition, the control device 7 drives the suction unit 60 to fix the lower polishing pad 26 to the first surface plate 31 before, after, or simultaneously with the start of the coolant supply process.

[0047] Next, the control device 7 starts polishing a predetermined batch number of wafers W (polishing start step: step S12). In the polishing initiation step S12, the control device 7 controls the polishing fluid supply unit 29 to supply polishing fluid to the lower polishing pad 26, controls the lower platen drive unit 27 to rotate the lower platen 25, and controls the head lifting unit 23 and head drive unit 24 to rotate and lower each polishing head 21. When polishing begins, the temperature of the lower platen 25 rises due to frictional heat, but the lower platen 25 is cooled by the coolant C.

[0048] Subsequently, the control device 7 determines, based on the measurement results of the supply-side hydraulic pressure gauge 54 and the discharge-side hydraulic pressure gauge 58, whether the supply-side hydraulic pressure is at the supply-side target hydraulic pressure and whether the discharge-side hydraulic pressure is at the discharge-side target hydraulic pressure (whether the supply-side hydraulic pressure and discharge-side hydraulic pressure are at the target hydraulic pressure) (Step S13: Determination step). The determination step in Step S13 can also be described as a step in determining whether the hydraulic pressure in the coolant flow path 43 is at the target hydraulic pressure that does not cause pressure deformation of the first surface plate 31.

[0049] If the control device 7 determines that at least one of the supply-side hydraulic pressure and the discharge-side hydraulic pressure is not at the target hydraulic pressure (step S13: NO), it controls at least one of the supply pump 53 and the discharge pump 57 so that the supply-side hydraulic pressure and the discharge-side hydraulic pressure reach the target hydraulic pressure and the coolant flow rate reaches the target flow rate (step S14: pump control step). The pump control step in step S14 can also be described as the step of controlling at least one of the pumps so that the hydraulic pressure in the coolant flow path 43 reaches the target hydraulic pressure and the coolant flow rate reaches the target flow rate. In the pump control process of step S14, the control device 7 increases the discharge rate of the supply pump 53 and the suction rate of the discharge pump 57 when increasing the discharge hydraulic pressure without changing the supply hydraulic pressure, or when increasing both the supply and discharge hydraulic pressures. Also, when the control device 7 decreases the supply hydraulic pressure while increasing the discharge hydraulic pressure, it increases the suction rate of the discharge pump 57 without changing the discharge rate of the supply pump 53. Furthermore, when the supply and discharge hydraulic pressures are in other combinations (for example, decreasing the supply hydraulic pressure and increasing the discharge hydraulic pressure), the control device 7 controls the supply pump 53 and the discharge pump 57 according to the state of the other combination. The control device 7 performs the pump control process in step S14, and then, after a predetermined period of time has elapsed, performs the determination process in step S13.

[0050] On the other hand, if the control device 7 determines that the supply side hydraulic pressure and the discharge side hydraulic pressure are at the target hydraulic pressure (step S13: YES), it determines whether or not the polishing of a predetermined batch has been completed (step S15: completion determination step). If the control device 7 determines that polishing of a predetermined batch has not been completed (step S15: NO), it performs the determination process in step S13 after a predetermined period of time has elapsed. On the other hand, if the control device 7 determines that the polishing of the target batch number has been completed (step S15: YES), it stops the supply pump 53 and the discharge pump 57 to stop the supply of coolant C to the coolant passage 43 (step S16: coolant supply stop step), and ends the single-sided finishing process.

[0051] <Effects of the Embodiment> The cooling structure of the lower surface platen 25, which includes a first surface platen 31, a second surface platen 32, and a coolant flow path 43, comprises a supply pipe 52 connected to the inlet 39 of the coolant flow path 43 and equipped with a supply pump 53, and a discharge pipe 56 connected to the outlet 40 of the coolant flow path 43 and equipped with a discharge pump 57. The control device 7 controls at least one of the supply pump 53 and the discharge pump 57 so that the coolant flow rate becomes the target flow rate and the liquid pressure in the coolant flow path 43 becomes the target liquid pressure at which the first surface platen 31 does not undergo pressure deformation during the polishing of the wafer W. Therefore, even if the hydraulic pressure in the coolant passage 43 does not reach the target hydraulic pressure due to pressure loss, the coolant flow rate can be set to the target flow rate and the hydraulic pressure in the coolant passage 43 can be set to the target hydraulic pressure by controlling at least one of the supply pump 53 and the discharge pump 57. Therefore, it is possible to provide a surface plate cooling structure that can suppress pressure deformation of the lower surface plate 25 while maintaining a predetermined cooling capacity for the lower surface plate 25. In addition, there may be cases where, for example, foreign matter adheres to the coolant passage 43, causing the fluid pressure in the coolant passage 43 to not reach the target fluid pressure. However, even in such cases, by controlling at least one of the pumps, the coolant flow rate can be set to the target flow rate, and the fluid pressure in the coolant passage 43 can be set to the target fluid pressure.

[0052] Furthermore, as described above, the present invention makes it possible to suppress pressure deformation of the lower platen 25 while maintaining a predetermined cooling capacity for the lower platen 25, thereby improving the yield when manufacturing polishing targets such as wafers W, and the yield when manufacturing devices from wafers W. Improved yield enhances the manufacturing efficiency of semiconductor products, enabling the production of more high-quality products, contributing to the promotion of technological innovation and the sustainable development of the industry. Improved yield also contributes to the efficient use of resources by reducing waste of materials consumed in the semiconductor product manufacturing process. Moreover, improved yield reduces energy waste in the semiconductor product manufacturing process, consequently contributing to the reduction of greenhouse gas emissions. In other words, the present invention can, for example, contribute to Sustainable Development Goals (SDGs) "Goal 9: Build industry, innovation and infrastructure," "Goal 12: Ensure sustainable consumption and production," and "Goal 13: Address climate change."

[0053] The control device 7 controls at least one of the supply pump 53 and the discharge pump 57 such that the supply-side fluid pressure corresponding to the fluid pressure on the upstream side of the coolant flow path 43 becomes the supply-side target fluid pressure, and the discharge-side fluid pressure corresponding to the fluid pressure on the downstream side of the coolant flow path 43 becomes the discharge-side target fluid pressure. In this way, by controlling at least one of the pumps based on the corresponding fluid pressures on the upstream and downstream sides of the coolant flow path 43, the fluid pressure in the coolant flow path 43 can be controlled more appropriately.

[0054] [Differentiation] Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and various improvements and design changes that do not depart from the spirit of the present invention are also included.

[0055] Without providing a supply-side hydraulic pressure gauge 54, at least one of the supply pump 53 and the discharge pump 57 may be controlled so that the discharge-side hydraulic pressure becomes the target discharge-side hydraulic pressure. Even with this configuration, the hydraulic pressure in the coolant flow path 43 can be set to the target hydraulic pressure. The target hydraulic pressure may be set within a predetermined range of -50kPa to +50kPa in gauge pressure. The single-sided finishing process in step S6 may be performed by an operator rather than by the control device 7. After polishing a predetermined batch number in the single-sided finishing process of step S6, when polishing the next predetermined batch number, the supply-side hydraulic pressure gauge 54 and the discharge-side hydraulic pressure gauge 58 may be removed, and the settings of the supply pump 53 and discharge pump 57 after the last pump control process in the previous single-sided finishing process may be maintained. The cooling liquid supply step S11, the determination step S13, and the pump control step S14, which constitute the surface plate cooling method of the present invention, may be performed during the warm-up time or standby time of the single-sided polishing apparatus 1. With this configuration, the frequency of performing the pump control step after the start of polishing can be reduced.

[0056] The surface plate cooling structure of the present invention may be applied to a structure that cools at least one of the surface plates, the lower surface plate and the upper surface plate, in a double-sided polishing apparatus used for rough polishing in the pretreatment step S4, or in a double-sided polishing apparatus used for mirror finishing in the simultaneous double-sided polishing step S5. In these polishing apparatuses, for example, if a configuration is used that can polish 15 wafers with a diameter of 300 mm in one batch, the target flow rate range can be set to 70 L / min or more and 100 L / min or less. The polishing object polished by the polishing apparatus to which the base plate cooling structure of the present invention is applied is not limited to wafers, but may also be a component made of metal or the like that requires a certain degree of flatness. [Explanation of Symbols]

[0057] 1...Single-sided polishing device (polishing device), 7...Control device, 21...Polishing head, 24...Head drive unit (rotation drive unit), 25...Lower platen (platen), 27...Lower platen drive unit (rotation drive unit), 31...First platen, 32...Second platen, 37...Flow channel groove, 39...Inlet, 40...Outlet, 43...Coolant flow channel, 52...Supply pipe, 53...Supply pump, 54...Supply side hydraulic pressure gauge, 56...Discharge pipe, 57...Discharge pump, 58...Discharge side hydraulic pressure gauge, C...Coolant, W...Wafer (object to be polished), W1...Surface to be polished (main surface).

Claims

1. A cooling structure for a polishing platen of a polishing apparatus that polishes the main surface of an object to be polished, The surface plate comprises a first surface plate on which the object to be polished is positioned on one side, and a second surface plate fixed to the other side of the first surface plate. At least one of the opposing surfaces of the first and second surface plates has a flow channel groove that constitutes a coolant flow channel. A supply pipe is connected to the inlet of the aforementioned coolant passage, and a supply pump is provided to supply coolant to the aforementioned coolant passage. A surface plate cooling structure, wherein a discharge pipe equipped with a discharge pump for discharging the coolant from the coolant passage is connected to the outlet of the coolant passage.

2. In the surface plate cooling structure according to claim 1, A base plate cooling structure is provided in which a discharge-side hydraulic pressure gauge is installed upstream of the discharge pump in the discharge pipe.

3. In the base plate cooling structure according to claim 2, A base plate cooling structure is provided in which a supply-side hydraulic pressure gauge is installed downstream of the supply pump in the supply pipe.

4. In the base plate cooling structure described in claim 3, A surface plate cooling structure further comprising a control device that controls at least one of the supply pump and the discharge pump such that the hydraulic pressure measured by the discharge-side hydraulic pressure gauge becomes a first target hydraulic pressure at which the first surface plate does not undergo pressure deformation, and the hydraulic pressure measured by the supply-side hydraulic pressure gauge becomes a second target hydraulic pressure at which the first surface plate does not undergo pressure deformation.

5. A single-sided polishing apparatus for polishing one main surface of a wafer, which is the object to be polished, A surface plate with polishing pads covering its entire surface, A polishing head that presses one of the main surfaces of the wafer against the polishing pad, A surface plate cooling structure according to any one of claims 1 to 4 for cooling the surface plate, A single-sided polishing device comprising a rotary drive unit that polishes one of the main surfaces by rotating the surface plate and the polishing head relative to each other.

6. A method for cooling the surface plate of a polishing apparatus used to polish the main surface of an object to be polished, The surface plate comprises a first surface plate on which the object to be polished is positioned on one side, and a second surface plate fixed to the other side of the first surface plate. At least one of the first surface plate and the second surface plate has flow channel grooves that constitute a coolant flow channel. A supply pipe equipped with a supply pump that supplies coolant to the coolant passage is connected to the inlet of the coolant passage. A discharge pipe equipped with a discharge pump for discharging the coolant from the coolant passage is connected to the outlet of the coolant passage. The aforementioned platen cooling method is A coolant supply step involves driving the supply pump and the discharge pump to supply the coolant to the coolant flow path, A surface plate cooling method comprising a pump control step of controlling at least one of the supply pump and the discharge pump so that the liquid pressure in the cooling liquid passage becomes a target liquid pressure that does not cause pressure deformation of the first surface plate.

7. In the plate cooling method described in claim 6, A platen cooling method, wherein the pump control step controls at least one of the pumps such that the liquid pressure upstream of the discharge pump in the discharge pipe becomes the first target liquid pressure.

8. In the plate cooling method described in claim 7, A platen cooling method, wherein the pump control step controls at least one of the pumps so that the liquid pressure downstream of the supply pump in the supply pipe becomes the second target liquid pressure.

9. In the plate cooling method described in claim 6, A method for cooling a surface plate, wherein the target hydraulic pressure is 50 kPa or less relative to atmospheric pressure.

10. In the plate cooling method described in claim 9, A method for cooling a surface plate, wherein the target hydraulic pressure is less than atmospheric pressure.

11. In the plate cooling method according to claim 10, A method for cooling a surface plate, wherein the target hydraulic pressure is -50 kPa or more relative to atmospheric pressure.

12. A method for manufacturing a wafer, comprising the step of polishing a wafer as an object to be polished using the polishing apparatus in which the polishing platen has been cooled by the polishing platen cooling method described in any one of claims 6 to 11.

Images