Grinding device

Abstract

To provide a polishing device which polishes a chuck with excellent reproducibility.SOLUTION: A CMP device 1 includes: a porous chuck 16 which includes a chuck table 17 provided at a lower end of a polishing head 10 and a chuck 18 received in a lower surface of the chuck table 17 so that a workpiece W can be held by a holding surface 16a; and a base member 13 which is fastened to the chuck table 17 and transmits rotational driving force input into the polishing head 10 to the chuck table 17. The chuck table 17 and the base member 13 are made of a material indicating a linear expansion coefficient in which flatness of the holding surface 16a changing according to a temperature of the chuck 18 caused by a difference between a linear expansion coefficient of the chuck table 17 and a linear expansion coefficient of the base member 13 is substantially linearly changed over a use temperature range of the CMP device 1. The difference between the linear expansion coefficient of the base member 13 and the linear expansion coefficient of the chuck table 17 is set to be 2.2 ppm / °C or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a polishing apparatus for polishing a workpiece.

Background Art

[0002] In the field of semiconductor manufacturing, a CMP apparatus for polishing and planarizing a silicon wafer or the like (hereinafter referred to as a "workpiece") is known.

[0003] The polishing apparatus described in Patent Document 1 is a polishing apparatus to which a chemical mechanical polishing, so-called CMP (Chemical Mechanical Polishing) technique is applied. This CMP apparatus presses a workpiece mounted on a polishing head against a polishing pad to polish the workpiece.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in backside reference polishing in which the back surface of the workpiece is held by the chuck of the polishing head and the front surface of the workpiece is pressed against the polishing pad for polishing, the flatness of the chuck holding the workpiece is transferred as a pressure distribution acting on the workpiece, and it is known that the shape of the workpiece after polishing is affected.

[0006] In a conventional polishing head, the flatness of the chuck is set to 1 μm or less by lapping the suction surface of the chuck. However, there is a problem that even when the workpiece is held on such a flat suction surface and polished under the same polishing conditions, the workpiece shape is not stable, that is, an event in which high reproducibility cannot be obtained occurs.

[0007] Therefore, technical challenges arise that need to be solved in order to polish workpieces with good reproducibility, and the present invention aims to solve these challenges. [Means for solving the problem]

[0008] As a result of diligent research by the inventors, it was discovered that in conventional polishing devices, the difference between the coefficient of thermal expansion of the alumina chuck table housing the chuck and the coefficient of thermal expansion of the metal base member that is fastened to the chuck table and transmits the rotational driving force input to the polishing head to the chuck table causes a nonlinear responsive distortion in the chuck in response to temperature changes during polishing.

[0009] Furthermore, the inventors have discovered that by setting the difference between the coefficient of thermal expansion of the chuck table and the coefficient of thermal expansion of the base member within a predetermined range, the flatness of the chuck changes in a substantially linear manner.

[0010] To achieve the above objective, the polishing apparatus according to the present invention is a polishing apparatus that polishes a workpiece held in a polishing head by pressing it against a polishing pad on a platen, and comprises a holding mechanism having a chuck table provided at the lower end of the polishing head and a chuck housed on the lower surface of the chuck table and capable of holding the workpiece with a holding surface, and a base member that is pressed against the chuck table by fastening and transmits the rotational driving force input to the polishing head to the chuck table, wherein the chuck table and the base member are made of a material exhibiting a coefficient of linear expansion such that the flatness of the holding surface, which changes according to the temperature of the chuck due to the difference between the coefficient of linear expansion of the chuck table and the coefficient of linear expansion of the base member, changes in a substantially linear manner over the operating temperature range of the polishing apparatus, and the difference between the coefficient of linear expansion of the base member and the coefficient of linear expansion of the chuck table is set to 2.2 ppm / °C or less.

[0011] Furthermore, in the polishing apparatus according to the present invention, if the coefficient of linear expansion of the chuck table is 7.2 ppm / °C, it is preferable that the coefficient of linear expansion of the base member is 5.0 to 9.4 ppm / °C.

[0012] Furthermore, in the polishing apparatus according to the present invention, it is preferable that the base member is a low thermal expansion alloy having a coefficient of linear expansion lower than that of the chuck table. [Effects of the Invention]

[0013] This invention enables the polishing of a workpiece to a flat surface with high reproducibility. [Brief explanation of the drawing]

[0014] [Figure 1] A schematic perspective view showing a CMP apparatus according to the first embodiment of the present invention. [Figure 2] A schematic longitudinal cross-sectional view showing the main parts of the polishing head. [Figure 3] A graph showing the temperature dependence of the flatness of the holding surface in a CMP apparatus to which the base member according to a comparative example of the present invention is applied. [Figure 4] A schematic diagram illustrating how the holding surface deforms due to temperature changes. [Figure 5] A schematic diagram showing how the base member and chuck table expand as the temperature rises. [Figure 6] A graph showing the relationship between the temperature of the chuck and the flatness of the holding surface when a workpiece is polished using the CMP apparatus according to Example 1 and Example 2 of the present invention. [Figure 7] A graph showing the finished shape of a workpiece at different polishing temperatures when polishing a workpiece using the CMP apparatus described in the comparative example. [Figure 8] A graph showing the finished shape of a workpiece at different polishing temperatures when polishing a workpiece using the CMP apparatus according to Example 1. [Figure 9] A graph showing the finished shape of a workpiece at different polishing temperatures when polishing a workpiece using the CMP apparatus according to Example 2. [Figure 10] A graph showing the temperature dependence of the flatness of the holding surface in a comparative example CMP apparatus, with the slope of the flatness of the holding surface added. [Figure 11]Schematic diagram showing the state where the holding surface is deformed into a convex shape in the middle to correspond to the polished pad with the center sunken.

Embodiment for Carrying Out the Invention

[0015] An embodiment of the present invention will be described based on the drawings. In the following, when referring to the number of components, numerical values, amounts, ranges, etc., unless otherwise specified or limited to a specific number in principle, it is not limited to that specific number, and it may be more or less than the specific number.

[0016] Also, when referring to the shape, positional relationship, etc. of components, etc., unless otherwise specified or considered not to be so in principle, it includes those substantially approximated or similar to the shape, etc.

[0017] Also, the drawings may be exaggerated by enlarging characteristic parts to make the characteristics easier to understand, and the dimensional ratios of components, etc. are not necessarily the same as the actual ones. Also, in cross-sectional views, in order to make the cross-sectional structure of components easier to understand, the hatching of some components may be omitted.

[0018] FIG. 1 is a perspective view schematically showing a CMP apparatus 1 according to an embodiment of the present invention. The CMP apparatus 1 polishes one surface of a workpiece W flat. The CMP apparatus 1 includes a platen 2 and a polishing head 10. The workpiece W is, for example, a silicon wafer, but is not limited thereto.

[0019] The platen 2 is formed in a disk shape and is connected to a rotating shaft 3 disposed below the platen 2. When the rotating shaft 3 rotates by the drive of a motor 4, the platen 2 rotates in the direction of arrow D1 in FIG. 1. A polishing pad 5 is attached to the upper surface of the platen 2, and a CMP slurry, which is a mixture of a polishing agent and a chemical, is supplied from a nozzle (not shown) onto the polishing pad 5.

[0020] Furthermore, a circulating cooling system 6 is connected to the platen 2, and temperature-controlled chiller water supplied from the circulating cooling system 6 flows through the platen 2, allowing the temperature of the platen 2 to be adjusted during the polishing process according to the temperature and flow rate of the chiller water.

[0021] The polishing head 10 is formed to have a smaller diameter than the platen 2 and is connected to a rotating shaft 10a located above the polishing head 10. The rotating shaft 10a rotates due to the drive of a motor (not shown), causing the polishing head 10 to rotate in the direction of arrow D2 in Figure 1. The polishing head 10 is configured to be movable in the vertical and horizontal directions by a head moving mechanism (not shown). When polishing the workpiece W, the polishing head 10 descends and presses the workpiece W against the polishing pad 5.

[0022] The operation of the CMP device 1 is controlled by a control device (not shown). The control device controls each of the components that make up the CMP device 1. The control device is, for example, a computer and is composed of a CPU, memory, etc. The functions of the control device may be realized by control using software or by operating using hardware.

[0023] Next, the structure of the polishing head 10 will be described. Figure 2 is a schematic longitudinal cross-sectional view showing the main part of the polishing head 10.

[0024] The polishing head 10 includes a head body 11 connected to a rotating shaft 10a. The head body 11 is connected to a base member 13 via a rotation transmission unit 12, and the head body 11, rotation transmission unit 12, and base member 13 rotate together with the rotating shaft 10a.

[0025] A plate holder 14 made of PPS is fastened to the upper part of the base member 13 via bolt B1. As a result, the rotational driving force input to the polishing head 10 is transmitted to the plate holder 14 via the base member 13.

[0026] An airbag 15 is interposed between the plate holder 14 and the head body 11. The airbag 15 can be inflated and deflated by air supplied from a compressed air source (not shown) via a vacuum line 15a. The pressure of the air supplied from the compressed air source is regulated by a regulator (not shown). The airbag 15 adjusts the polishing pressure at which the workpiece W is pressed against the polishing pad 5 by pressurizing the plate holder 14 according to the pressure of the supplied air.

[0027] A porous chuck 16 is provided below the base member 13. The porous chuck 16 comprises an alumina chuck table 17 and a porous alumina chuck 18.

[0028] The chuck table 17 is fastened to the base member 13 via bolts B2. This allows the rotational driving force input to the polishing head 10 to be transmitted to the porous chuck 16 via the base member 13.

[0029] The chuck 18 is embedded in the underside of the chuck table 17. The chuck 18 is connected to a vacuum source and a cooling water source (not shown) via line 18a. By activating the vacuum source, the workpiece W is held by suction on the holding surface 16a of the porous chuck 16. The cooling water supplied from the cooling water source is temperature-controlled to approximately room temperature, and the chuck 18 is cooled by passing the water through it after polishing.

[0030] In this way, the polishing head 10 presses the surface of the workpiece W against the polishing pad 5 while the back surface of the workpiece W is held by suction to the chuck 18, and as the airbag 15 inflates, a load is transmitted to the workpiece W, causing the workpiece W to be polished so that the shape of the holding surface 16a is transferred to it (back surface reference polishing). The holding surface 16a is set to a flatness of approximately 1 μm or less by lapping, and in this type of back surface reference polishing, the flatness of the holding surface 16a of the chuck table 17 affects the finished shape of the workpiece W.

[0031] Furthermore, the base member 13 is made of a material that exhibits a coefficient of thermal expansion close to that of the alumina that constitutes the chuck table 17 (7.2 ppm / °C). The base member 13 is, for example, a low thermal expansion alloy (Invar alloy) formulated to have a coefficient of thermal expansion close to that of alumina.

[0032] Furthermore, the fact that the linear expansion coefficients of the base member 13 and the chuck table 17 are close means that, over the operating temperature range of the CMP device 1 (for example, approximately 10 to 40°C), the base member 13 and the porous chuck 16 expand and contract respectively while fastened together by bolts B2. The difference between the linear expansion coefficients of the base member 13 and the chuck table 17 causes the flatness of the holding surface 16a, which changes in response to the temperature change of the chuck 19, to change in a substantially linear manner (respond linearly). This is because the linear expansion coefficients of the base member 13 and the chuck table 17 are set to such a degree. The operating temperature range of the CMP device 1 varies depending on the pressure applied to the workpiece W, the rotational speed of the polishing head 10, the rotational speed of the platen 2, the slurry flow rate, the temperature and flow rate of the chiller water, etc. [Examples]

[0033] Next, we will describe evaluation data comparing the change in the flatness of the holding surface 16a within the operating temperature range for CMP apparatus 1 (Example 1) using a base member 13 made of Invar alloy with a linear expansion coefficient of 5.0 ppm / °C, CMP apparatus 1 (Example 2) using a base member 13 made of Invar alloy with a linear expansion coefficient of 7.0 ppm / °C, and CMP apparatus 1 (Comparative Example) using a conventional base member 13 made of SUS316.

[0034] [Evaluation Method] First, Figure 3 shows the relationship between the temperature of the chuck 18 and the flatness of the holding surface 16a when the polishing head 10 of the comparative example CMP apparatus 1 is subjected to a temperature change due to external factors.

[0035] Figure 3 is a graph showing the temperature dependence of the flatness of the holding surface 16a in the polishing head 10 of the comparative example CMP apparatus 1. In the graph of Figure 3, the vertical axis is set to the flatness of the holding surface 16a and the horizontal axis is set to the temperature of the chuck 18. A positive flatness corresponds to a convex state where the center of the porous chuck 16 is convex compared to the outer circumference, and a negative flatness corresponds to a concave state where the center of the porous chuck 16 is concave compared to the outer circumference. The flatness of the holding surface 16a was measured using a Corning Tropel Flat Master 200XRA-Industrial. The temperature of the chuck 18 was measured using an Anritsu Keiki Co., Ltd. digital thermometer HA-202K.

[0036] The range indicated by the symbol a in Figure 3 corresponds to the state in which the polishing head 10 of the comparative example CMP apparatus 1 is waiting at room temperature (approximately 22-24°C), and shows the change in the flatness of the holding surface 16a when the temperature of the chuck 18 is changed at room temperature (approximately 22-24°C). Within this range, it can be seen that the flatness of the holding surface 16a responds linearly, becoming negative (concave) as the temperature increases.

[0037] The range indicated by the symbol b in Figure 3 corresponds to the state in which the chuck 18 is heated up due to the frictional heat generated during polishing, and shows the change in the flatness of the holding surface 16a when the chuck 18 is heated to approximately 37°C, which is the temperature during polishing, on a hot plate set to 40°C. The range indicated by the symbol c in Figure 3 corresponds to the state in which the polishing head 10 is cooled by passing cooling water through it after polishing, and shows the change in the flatness of the holding surface 16a when it is left at room temperature after heating on a hot plate and then cooled to approximately room temperature. The range indicated by the symbol b and the range indicated by the symbol c do not coincide, indicating that the flatness of the holding surface 16a deviates from a linear response and changes in a hysteretic manner. Furthermore, it can be seen that the flatness of the holding surface 16a after heating and cooling to room temperature (23°C) is positive (approximately 5 μm) and deformed into a convex shape.

[0038] Furthermore, the range indicated by the symbol d in Figure 3 corresponds to a state where the polishing head 10 is placed in an environment below room temperature due to transportation or other reasons, and shows the change in the flatness of the holding surface 16a when the polishing head 10 is cooled to near the lower limit of the operating temperature range (approximately 11°C) with chiller water at 10°C. The range indicated by the symbol e in Figure 3 shows the change in the flatness of the holding surface 16a when the polishing head 10, after being cooled with chiller water at 10°C, is left at room temperature and warmed to approximately room temperature. The range indicated by the symbol d and the range indicated by the symbol e do not coincide, indicating that the flatness of the holding surface 16a deviates from a linear response and changes in a hysteretic manner. Furthermore, it can be seen that the flatness of the holding surface 16a, after being cooled and warmed to room temperature (23°C), is negative (approximately -4 μm) and has deformed into a concave shape.

[0039] Thus, it can be seen that there is a significant difference between the flatness of the holding surface 16a when it is at approximately room temperature and the flatness of the holding surface 16a when it has reached approximately room temperature after heating due to polishing or cooling by the outside air in cold weather. Furthermore, because the flatness of the holding surface 16a changes hysterically, it was extremely difficult to control the flatness of the holding surface 16a.

[0040] Furthermore, considering that the flatness of the holding surface 16a after lapping is approximately 1 μm, while the flatness of the holding surface 16a after heating and cooling to approximately room temperature is approximately 5 μm, it is clear that the workpiece W cannot be polished stably, and that it is necessary to reduce the fluctuation in flatness of the porous chuck 16 due to temperature changes.

[0041] The temperature dependence of the porous chuck 16 is thought to be due to the following reason. Specifically, due to the bimetallic effect caused by the difference in linear expansion coefficients between the SUS316 base member 13 (coefficient of linear expansion: 16.0 ppm / °C) and the alumina chuck table 17 (coefficient of linear expansion: 7.2 ppm / °C), as shown in Figure 4, when heated the base member 13 expands relatively more, causing the holding surface 16a to deform into a concave shape, and when cooled the base member 13 contracts relatively more, causing the holding surface 16a to deform into a convex shape.

[0042] Furthermore, when the base member 13 and the porous chuck 16 are heated, as shown in Figure 5(a), the chuck table 17 is fastened to the base member 13 with bolts B2, and as shown in Figure 5(b), in the initial stages of thermal expansion, the base member 13 and the chuck table 17 are expected to expand uniformly as the temperature rises (linear response) due to the fastening force by bolts B2 and the surface friction force acting on the contact surface between bolts B2 and the base member 13 and the contact surface between the base member 13 and the chuck table 17 (dashed line portion in Figure 5(b)).

[0043] However, as shown in Figure 5(c), if the base member 13 expands to the point where it can no longer be supported by the fastening force of bolt B2 and the surface friction of the base member 13 and the chuck table 17, the base member 13 will reach its holding limit and slide laterally against the chuck table 17. As a result, the base member 13 and the chuck table 17 will not expand uniformly, and the flatness of the holding surface 16a is thought to tend to saturate with respect to temperature changes. A similar tendency is thought to occur when the base member 13 and the porous chuck 16 cool down.

[0044] While increasing the tightening torque of bolt B2 can expand the temperature range in which the linear response occurs, since the chuck table 17 is fastened with bolt B2 via a helicoil tap (not shown), there is a risk that the chuck table 17 may chip or crack if tightened with a torque exceeding a predetermined value.

[0045] Next, Figure 6 shows the relationship between the temperature of the chuck 18 and the flatness of the holding surface 16a when the workpiece W was polished using the CMP apparatus 1 according to Example 1 and Example 2, respectively, under the polishing conditions shown in Table 1. In the graph of Figure 6, the flatness of the holding surface 16a is set on the vertical axis and the temperature of the chuck 18 is set on the horizontal axis. Note that the measurement of the flatness of the holding surface 16a and the temperature of the chuck 18 are the same as in the comparative example described above. [Table 1]

[0046] As shown in Figure 6, the variation in flatness of the porous chuck 16 with respect to temperature changes is smaller compared to Figure 3. Specifically, the range of change in the flatness of the holding surface 16a within the operating temperature range is -4 to 4 μm in Example 1, centered around the flatness at room temperature (0 μm), and 2 to 2.5 μm in Example 2, centered around the flatness at room temperature (2.2 μm). Therefore, the flatness of the holding surface 16a in a standby state at room temperature does not deviate from the flatness of the holding surface 16a after heating and cooling by chiller associated with polishing, indicating that the workpiece W can be polished stably with high reproducibility.

[0047] Furthermore, if the base member 13 is made of a material that exhibits a coefficient of thermal expansion similar to that of the alumina chuck table 17, the flatness of the holding surface 16a will respond linearly, indicating that the flatness of the holding surface 16a can be easily controlled by temperature control of the chuck 18.

[0048] Next, Figures 7 to 9 show the finished shape of the workpiece W at each polishing temperature (adjusted by changing the chiller water temperature supplied to the platen 2) when the workpiece W was polished using the respective CMP apparatus 1 according to Example 1, Example 2, or Comparative Example.

[0049] The graphs in Figures 7-9 show the finished thickness of the workpiece W on the vertical axis and the radial coordinates on the horizontal axis. In Figures 7-9, the finished thickness at a point 70 mm away from the center in the radial direction R is used as the reference, and the finished thickness at each measurement point (R=0 mm, approximately 17 mm, approximately 35 mm, approximately 53 mm) is plotted as the relative height to the reference, representing the finished shape of the workpiece W at each polishing temperature. Note that multiple measurement points are set on the workpiece W with the same radial coordinates, and the finished thickness is an index of the average value of multiple measurement points on concentric circles.

[0050] In back-side reference polishing, where the holding surface 16a is transferred to the finished shape of the workpiece W, if the holding surface 16a is deformed into a convex shape with a convex center, the finished shape of the workpiece W will be a concave shape with a concave center, and if the holding surface 16a is deformed into a concave shape with a concave center, the finished shape of the workpiece W will be a convex shape with a convex center. In other words, the finished shape of the workpiece W and the shape of the holding surface 16a are inversely related.

[0051] Figure 7 shows the finished shape of the workpiece W at different polishing temperatures when the workpiece W is polished using the comparative example CMP apparatus 1.

[0052] As shown in Figure 7, when the polishing temperature is below room temperature (approximately 23°C), the finished shape of the workpiece W is convex in the middle and curved in a way that the inclination gradually decreases towards the outer circumference. When the polishing temperature is above room temperature (approximately 23°C), the finished shape of the workpiece W is concave in the middle and curved in a way that the inclination gradually increases towards the outer circumference.

[0053] Figure 8 shows the finished thickness of the workpiece W at different polishing temperatures when the workpiece W was polished using the CMP apparatus 1 according to Example 1.

[0054] As shown in Figure 8, compared to Figure 7, when the polishing temperature is below room temperature (approximately 23°C), the finished shape of the workpiece W is the same in that it is convex in the middle, but the height in the center is lower, and the entire surface of the workpiece W is formed to be almost flat. When the polishing temperature is above room temperature (approximately 23°C), the finished shape of the workpiece W is the same in that it is concave in the middle, but the height in the center is higher, and the entire surface of the workpiece W is formed to be almost flat.

[0055] Figure 9 shows the finished thickness of the workpiece W at different polishing temperatures when the workpiece W was polished using the CMP apparatus 1 according to Example 2.

[0056] As shown in Figure 9, compared to Figures 7 and 8, it can be seen that the entire surface of the workpiece W is formed to be the flattest, regardless of the polishing temperature.

[0057] In this way, by constructing the base member 13 from a material with a small difference in coefficient of thermal expansion from the chuck table 17, the finished shape of the workpiece W can be easily formed flat without strict control of the polishing temperature.

[0058] To easily control the flatness of the holding surface 16a, if the linear expansion coefficient of the alumina constituting the chuck table 17 is 7.2 ppm / °C, then the material of the base member 13 is preferably one that exhibits a linear expansion coefficient of 5.0 to 9.4 ppm / °C. The reasons for this are explained below.

[0059] First, the difference between the coefficient of thermal expansion of the SUS316 base member 13 and the alumina porous chuck 16 is approximately 8.8 ppm / °C. Then, as shown in Figure 10 (Figure 3 with the slope of the flatness of the holding surface 16a added), the slope of the flatness of the holding surface 16a when the change is large (indicated by the dashed line in the figure) is -1.8 μm / °C, and the slope of the flatness of the holding surface 16a when the change is small (indicated by the dashed line in the figure) is -0.45 μm / °C. Therefore, the slope of the flatness when the flatness of the holding surface 16a changes the most is four times the value of the slope of the flatness when the change is small. Therefore, by constructing the base member 13 from a material such that the difference in linear expansion coefficient with respect to the porous chuck 16 is 2.2 ppm / °C or less (a value obtained by dividing approximately 8.8 ppm / °C by 4), it is considered that the flatness of the holding surface 16a will respond linearly to temperature changes over the operating temperature range (for example, approximately 10 to 40°C).

[0060] Furthermore, as the workpiece W is pressed into the polishing pad 5 during polishing, there is a risk that the polishing pad 5 may sink slightly, as shown in Figure 11, resulting in a concave finish on the workpiece W. In such cases, by constructing the base member 13 from a material with a lower coefficient of thermal expansion than the alumina chuck table 17, the holding surface 16a deforms into a convex shape as the temperature rises, allowing the workpiece W to be polished in a way that cancels out the sinking of the polishing pad 5.

[0061] Furthermore, the present invention can be modified in various ways other than those described above, as long as it does not deviate from the spirit of the invention, and it goes without saying that the present invention extends to such modified forms. [Explanation of Symbols]

[0062] 1:CMP equipment 2: Platen 3: (Platen's) axis of rotation 4: Motor 5: Polishing pad 6: Circulating cooling device 10: Polishing head 10a: Rotation axis (of the polishing head) 11: Head body 12: Rotation transmission section 13: Base component 14: Plate holder 15: Airbag 16: Porous chuck (holding mechanism) 16a: Holding surface 17: Chuck Table 18: Chuck W: Work

Claims

1. A polishing device that polishes a workpiece held in a polishing head by pressing it against a polishing pad on a platen, A holding mechanism comprising a chuck table provided at the lower end of the polishing head, and a chuck housed on the lower surface of the chuck table and capable of holding the workpiece with its holding surface, A base member that is fastened to the chuck table and transmits the rotational driving force input to the polishing head to the chuck table, Equipped with, The chuck table and the base member are made of different materials exhibiting linear expansion coefficients such that the flatness of the holding surface, which changes according to the temperature of the chuck due to the difference between the linear expansion coefficient of the chuck table and the linear expansion coefficient of the base member, changes in a substantially linear manner over the operating temperature range of the polishing device. A polishing apparatus characterized in that the difference between the coefficient of thermal expansion of the base member and the coefficient of thermal expansion of the chuck table is set to 2.2 ppm / °C or less.

2. The polishing apparatus according to claim 1, characterized in that the coefficient of linear expansion of the chuck table is set to 7.2 ppm / °C, and the coefficient of linear expansion of the base member is set to 5.0 to 9.4 ppm / °C.

3. The polishing apparatus according to claim 1, characterized in that the base member is a low thermal expansion alloy having a coefficient of linear expansion lower than that of the chuck table.

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