Spindle unit, processing apparatus, and wafer processing method

Abstract

This air bearing rotatably supports the spindle on which the workpiece is mounted, providing high rigidity to support the spindle while minimizing air consumption. [Solution] A spindle unit comprising a spindle (43) to which a processing tool (12) is attached, a casing (41) having an inner surface facing the outer surface of the spindle with a gap (S) between them, an air bearing that rotatably supports the spindle by interposing high-pressure air in the gap, and a motor (50) that rotates the spindle, wherein the air bearing comprises a hydrostatic air bearing (85) formed by supplying high-pressure air at a first flow rate (Aa), a hydrodynamic air bearing (84) formed on both sides of the hydrostatic air bearing or between two hydrostatic air bearings, which allows the high-pressure air supplied to form the hydrostatic air bearing to pass through at a second flow rate (Ab) less than the first flow rate, and exhaust ports (53, 55) that exhaust the high-pressure air that formed the hydrostatic air bearing through the hydrodynamic air bearing.

Description

Technical Field

[0001] The present invention relates to a spindle unit, a processing apparatus, and a method for processing a wafer.

Background Art

[0002] A spindle unit provided in a cutting apparatus for cutting a workpiece such as a semiconductor wafer, or a spindle unit provided in a grinding apparatus for grinding a workpiece, rotatably supports a spindle by a hydrostatic air bearing that supplies high-pressure air around the spindle (for example, Patent Documents 1 and 2).

[0003] As described above, in a conventional air bearing, high-pressure air is continuously supplied so that the gap is maintained at a high pressure to form an air bearing (hydrostatic bearing), so the air supply amount (air consumption amount) is large. Therefore, problems such as increased power consumption of a compressor or the like for producing high-pressure air occur. Thus, as disclosed in Patent Document 3, in a spindle unit, a technique has been proposed in which a hydrostatic air bearing and a hydrodynamic air bearing are provided, and when a spindle supported by the hydrostatic air bearing is rotated to form a hydrodynamic air bearing, the supply of high-pressure air for the hydrostatic air bearing is stopped to reduce the air consumption amount.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with only dynamic air bearings, problems such as spindle vibration can occur when machining hard materials (such as SiC and sapphire) that are subjected to heavy machining loads.

[0006] Therefore, the spindle unit and processing equipment have a challenge to overcome: supporting the spindle with sufficient strength to withstand the processing load while minimizing air consumption. [Means for solving the problem]

[0007] One aspect of the present invention is a spindle unit comprising: a spindle with a work tool attached to its tip for rotation; a casing having a gap on the outer surface of the spindle and an inner surface facing the outer surface; an air bearing in which high-pressure air is interposed in the gap and the casing rotatably supports the spindle; and a motor for rotating the spindle, wherein the air bearing comprises: a hydrostatic air bearing formed by supplying high-pressure air at a first flow rate; a hydrodynamic air bearing formed on both sides of the hydrostatic air bearing, or between two spaced-apart hydrostatic air bearings, by rotating the spindle at a predetermined rotational speed and allowing the high-pressure air supplied to form the hydrostatic air bearing to pass through at a second flow rate less than the first flow rate; and an exhaust port for exhausting the high-pressure air that formed the hydrodynamic air bearing through the hydrodynamic air bearing.

[0008] One aspect of the present invention is a processing apparatus comprising a chuck table for holding a workpiece and a processing unit for processing the workpiece with a rotating processing tool, wherein the processing unit includes the spindle unit described above and comprises a control unit that supplies high-pressure air to the gap at a preset first flow rate to form the hydrostatic air bearing and rotates the spindle to a predetermined rotational speed to form the hydrostatic air bearing, and in conjunction with the formation of the hydrostatic air bearing, high-pressure air is supplied to the hydrostatic air bearing and the hydrostatic air bearing at a second flow rate.

[0009] One aspect of the present invention is a method for processing a wafer using the processing apparatus described above, comprising: a holding step of holding a wafer, which is a workpiece, on a chuck table; a spindle support step of supplying high-pressure air to the spindle unit at a first flow rate to form a hydrostatic air bearing and rotatably support the spindle; and a processing step of rotating the spindle at a predetermined rotational speed to form a hydrostatic air bearing, and then supplying high-pressure air to the hydrostatic air bearing and the hydrostatic air bearing at a second flow rate to process the wafer. [Effects of the Invention]

[0010] According to each of the above embodiments, it is possible to support the spindle with sufficient strength to withstand machining loads in an air bearing while reducing the amount of air consumed to form the air bearing. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of the processing apparatus of this embodiment. [Figure 2] This is a cross-sectional view of the spindle unit of the first embodiment of the processing apparatus. [Figure 3] This figure shows the relationship between the supply of high-pressure air and the rotational speed of the spindle when forming an air bearing. [Figure 4] This is a cross-sectional view of the spindle unit according to the second embodiment. [Figure 5] This is a perspective view of the first large-diameter portion of the spindle in the spindle unit of the third embodiment. [Figure 6] This is a cross-sectional view showing a portion of the spindle unit of the third embodiment. [Figure 7] This is a perspective view of the first large-diameter portion of the spindle in the spindle unit of the fourth embodiment. [Figure 8] This is a cross-sectional view showing a portion of the spindle unit of the fourth embodiment. [Modes for carrying out the invention]

[0012] The spindle unit, processing apparatus, and wafer processing method according to this embodiment will be described below with reference to the attached drawings. This embodiment is applied to a cutting apparatus as an example of a processing apparatus equipped with a spindle unit. The processing apparatus to which the present invention is applied only needs to be equipped with a spindle unit that rotatably supports the spindle with an air bearing, and is not limited to a cutting apparatus. It can also be applied to grinding apparatuses equipped with a grinding wheel (grinding wheel) as a processing tool, polishing apparatuses equipped with a polishing pad as a processing tool, and so on.

[0013] The processing apparatus 10 shown in Figure 1 cuts a workpiece 1. The workpiece 1 is, for example, a disc-shaped semiconductor wafer made of silicon. On the surface of the workpiece 1, chips, which are electronic devices, are formed in multiple regions demarcated by multiple grid-like division lines. A flexible tape 2 is attached to the back side of the workpiece 1, and an annular ring frame 3 is attached to the outer circumference of the tape 2. Note that the workpiece processed by the processing apparatus 10 is not limited to semiconductor wafers. For example, inorganic material substrates such as ceramics, glass, and sapphire, or semiconductor product packaging substrates may also be used.

[0014] The machining unit 11 of the machining apparatus 10 is equipped with a cutting blade 12 as a machining tool. The X-axis, Y-axis, and Z-axis directions in the machining apparatus 10 are perpendicular to each other. The X-axis and Y-axis directions are horizontal, and the Z-axis direction is vertical. The X-axis direction is the machining feed direction that moves the workpiece 1 relative to the cutting blade 12 when the workpiece 1 is being cut along the division line by the cutting blade 12. The Y-axis direction is the indexing feed direction that moves the cutting blade 12 to position the cutting blade 12 at the next division line after cutting along the division line. The Z-axis direction is the cutting feed direction that moves the cutting blade 12 when the cutting blade 12 cuts into the workpiece 1.

[0015] The processing device 10 includes a chuck table 14 on a base 13. The chuck table 14 has a holding surface formed of a porous member such as porous ceramics on the upper surface side, and a suction force can be applied to the holding surface by a suction source (not shown). The workpiece 1 is sucked and held on the holding surface of the chuck table 14 through the tape 2 by the suction force on the holding surface. A plurality of clamps 15 are provided around the chuck table 14, and the ring frame 3 around the workpiece 1 is clamped and fixed by the clamps 15.

[0016] On the base 13 of the processing device 10, a processing feed mechanism 16 for moving the chuck table 14 in the X-axis direction is provided. The processing feed mechanism 16 has a pair of guide rails 17 and a ball screw 18 arranged on the base 13 and extending in the X-axis direction. The ball screw 18 is rotationally driven by a motor 19 provided at one end. The X-axis movement table 20 is supported slidably in the X-axis direction with respect to the guide rails 17 and has a screwing portion (not shown) with which the ball screw 18 is screwed. When the ball screw 18 is rotated by the motor 19, the X-axis movement table 20 moves in the X-axis direction.

[0017] On the X-axis movement table 20, a rotation support portion 21 for rotatably supporting the chuck table 14 around an axis in the Z-axis direction is provided. The chuck table 14 is supported on the upper part of the rotation support portion 21, and the chuck table 14 can be rotated by a motor (not shown) provided in the rotation support portion 21.

[0018] On the upper surface of the base 13, a gantry column 22 straddling the processing feed mechanism 16 is erected. The column 22 is provided with a indexing feed mechanism 23 for moving (indexing feed) the processing unit 11 in the Y-axis direction and a lifting mechanism 24 for moving (cutting feed) the processing unit 11 in the Z-axis direction.

[0019] The indexing feed mechanism 23 has a pair of guide rails 25 and a ball screw 26 positioned on the front of the column 22 and extending in the Y-axis direction, and the ball screw 26 is rotationally driven by a motor 27 provided at one end. The Y-axis moving table 28 is supported so as to be slidable in the Y-axis direction relative to the guide rails 25 and has a threaded portion (not shown) into which the ball screw 26 is screwed. When the ball screw 26 is rotated by the motor 27, the Y-axis moving table 28 moves in the Y-axis direction.

[0020] The lifting mechanism 24 has a pair of guide rails 29 and a ball screw 30 positioned in front of the Y-axis moving table 28 and extending in the Z-axis direction, and the ball screw 30 is rotationally driven by a motor 31 provided at one end. The Z-axis moving table 32 is supported so as to be slidable in the Z-axis direction relative to the guide rails 29 and has a threaded portion (not shown) into which the ball screw 30 is screwed. When the motor 31 rotates the ball screw 30, the Z-axis moving table 32 moves in the Z-axis direction.

[0021] The machining unit 11 includes a spindle unit 40 supported at the lower end of the Z-axis moving table 32. Referring to Figure 2, the structure of the spindle unit 40 of the first embodiment will be described. The spindle unit 40 has a box-shaped casing 41 that is long in the Y-axis direction. A spindle housing space 42 is formed inside the casing 41, and a spindle 43 is arranged in the spindle housing space 42. The spindle 43 has a first large-diameter portion 44 and a second large-diameter portion 45 that are offset in the Y-axis direction. The first large-diameter portion 44 and the second large-diameter portion 45 are enlarged portions of the diameter of a part of the spindle 43, with the first large-diameter portion 44 having a larger diameter than the second large-diameter portion 45. Also, the second large-diameter portion 45 has a longer length in the Y-axis direction than the first large-diameter portion 44. The spindle unit 40 includes an air bearing that supports the spindle 43 so that the casing 41 can rotate, by interposing high-pressure air in the gap S between the inner surface of the spindle housing space 42 and the outer surface of the spindle 43. Details of the air bearing will be described later.

[0022] A cutting blade 12 is attached to one end (tip portion 49) of the spindle 43. The cutting blade 12 is a hub blade comprising a hub 47 that is detachable from a blade mount 46 provided on the tip portion 49 of the spindle 43, and an annular cutting edge 48 provided on the side of the hub 47, and is mounted so that the cutting edge 48 is sandwiched between the blade mount 46 and the hub 47. Note that, unlike the cutting blade 12 shown in the figure, a hubless type cutting blade may be used as the cutting tool.

[0023] A motor 50 for rotating the spindle 43 is located at the other end of the spindle 43. The motor 50 has a rotor 51 attached to the outer circumference of the spindle 43 and a stator 52 arranged around the rotor 51. The stator 52 is fixed inside the casing 41. The rotor 51 is made of permanent magnets, and the stator 52 is made of a coil with a wire wound around it. By energizing the stator 52, a force is generated to rotate the spindle 43.

[0024] The spindle housing space 42 is a space inside the casing 41 that extends in the Y-axis direction. The central axis P is a virtual axis that extends in the Y-axis direction passing through the center of the spindle housing space 42. The casing 41 has an exhaust port 53 that connects one end of the spindle housing space 42 to the outside, and the tip portion 49 of the spindle 43 that connects to the blade mount 46 protrudes to the outside of the casing 41 through the exhaust port 53. The opening diameter of the exhaust port 53 is larger than the diameter of the tip portion 49 of the spindle 43, and when the spindle 43 is supported by an air bearing (as shown in Figure 2), the gap S inside the spindle housing space 42 and the outside of the casing 41 are in communication through the exhaust port 53. The other end of the spindle housing space 42 is in communication with the motor housing portion 54 inside the casing 41. Inside the motor housing portion 54, the stator 52 is fixed in an arrangement surrounding the central axis P, and the rotor 51 is arranged inside the stator 52. The casing 41 is provided with an exhaust port 55 that connects the inside of the motor housing 54 to the outside. When the spindle 43 is supported by the air bearing (as shown in Figure 2), high-pressure air in the spindle housing space 42 can be discharged to the outside of the casing 41 at a predetermined flow rate through the exhaust ports 53 and 55.

[0025] The casing 41 is equipped with a cooling water channel 56 that surrounds the outside of the stator 52. A cooling water supply port 57 provided on the outer surface of the casing 41 is connected to the cooling water channel 56, and cooling water is supplied to the cooling water channel 56 from a cooling water source 58 outside the casing 41 via the cooling water supply port 57. The cooling water in the cooling water channel 56 is discharged to the outside through a cooling water outlet 59 provided on the outer surface of the casing 41. The heat generated in the motor 50 when the spindle 43 is rotated can be removed by the cooling water passing through the cooling water channel 56, thereby cooling the motor 50.

[0026] The spindle housing space 42 has a first housing section 60 that houses the first large-diameter portion 44 of the spindle 43 and a second housing section 61 that houses the second large-diameter portion 45 of the spindle 43, located midway along the Y-axis. The first housing section 60 is a cylindrical space with the central axis P as its central axis, and has an inner surface 601 which is the outer surface of the cylindrical space, and a pair of parallel side surfaces 602 that face each other in the Y-axis direction. The second housing section 61 is a cylindrical space with the central axis P as its central axis, and has an inner surface 611 which is the outer surface of the cylindrical space, and a pair of parallel side surfaces 612 that face each other in the Y-axis direction.

[0027] A gap Sa, which is part of the gap S, is provided between the side surface 602 of the first housing section 60 and the outer surface of the spindle 43. By supplying high-pressure air to the gap Sa, a thrust bearing is formed that supports the spindle 43 in the axial direction (Y-axis direction).

[0028] Between the inner surface 611 of the second housing 61 and the outer surface of the spindle 43, gaps Sb and Sc, which are part of the gap S, are provided. By supplying high-pressure air to gaps Sb and Sc, a radial bearing is formed that radially supports the spindle 43.

[0029] The spindle unit 40 is equipped with a high-pressure air supply unit that supplies high-pressure air to the spindle housing space 42. Specifically, a plurality of high-pressure air supply units 62 are formed on a pair of side surfaces 602 of the first housing unit 60 that forms a gap Sa, and a plurality of high-pressure air supply units 63 are formed on the inner surface 611 of the second housing unit 61 that forms a gap Sb. In Figure 2, the high-pressure air supply units 62 and 63 are simplified and shown with arrows, but each of the high-pressure air supply units 62 and 63 is configured as an opening that opens to the inner surface of the spindle housing space 42.

[0030] A high-pressure air source 64 is provided outside the casing 41. The high-pressure air source 64 has a compressor, which compresses air to produce high-pressure air that is then sent to the spindle unit 40. Inside the casing 41, there is an air supply passage 65 that connects the high-pressure air supply units 62 and 63 with the high-pressure air source 64. The high-pressure air sent from the high-pressure air source 64 enters the air supply passage 65 through an air supply port 66 provided on the outer surface of the casing 41, and is supplied to the high-pressure air supply units 62 and 63 through the air supply passage 65. By supplying high-pressure air from the high-pressure air source 64 to the gap S inside the casing 41, and continuously supplying high-pressure air so that the gap S is maintained at high pressure, a hydrostatic air bearing is formed that rotatably supports the spindle 43 via the high-pressure air from the high-pressure air source 64. The hydrostatic air bearing can support the spindle 43 without contact with the inner surface of the spindle housing space 42, even when the spindle 43 is not rotating or when the spindle 43 is rotating at a low speed.

[0031] As shown in Figure 2, an air rectifier 80 is formed on the outer circumferential surface of the second large-diameter portion 45. In Figure 2, the second large-diameter portion 45 is shown in a side view rather than a cross-sectional view in order to show the air rectifier 80. The spindle 43 rotates in the rotation direction R shown in Figure 2. The air rectifier 80 is a recess or protrusion formed on the outer circumferential surface of the second large-diameter portion 45, and has multiple arrowhead-shaped features on its outer surface with their tips pointing in the opposite direction to the rotation direction R of the spindle 43. More specifically, the air rectifier 80 is located in the first region 81 and the second region 82, which are two regions near both ends in the Y-axis direction of the second large-diameter portion 45. In other words, the first region 81 and the second region 82 are regions spaced apart in the axial direction of the spindle 43. The second large-diameter portion 45 also has a third region 83, which is a smooth outer circumferential surface (cylindrical surface) where the air rectifier 80 is not formed, between the first region 81 and the second region 82 in the Y-axis direction. A gap Sc is formed in the area corresponding to the first region 81 and the second region 82, and a gap Sb is formed in the area corresponding to the third region 83. The gap Sb and the gap Sc are in communication in the Y-axis direction. The high-pressure air supply unit 63 supplies high-pressure air at a first flow rate to the gap Sb, mainly to the area of ​​the third region 83, thereby forming a static air bearing 85.

[0032] The air rectifiers 80 provided on the outer circumferential surfaces of the first region 81 and the second region 82 of the second large-diameter portion 45 have a shape that narrows (collects) the air in the gap Sc as the spindle 43 rotates in the rotation direction R. When high-pressure air is supplied to the gap Sb to form a static air bearing 85, and the spindle 43 is rotated in the rotation direction R at a rotation speed of a predetermined or higher by the motor 50, the air rectifiers 80 rotate the high-pressure air interposed in the gap Sc in the rotation direction R within the range of the first region 81 and the second region 82. As a result, a dynamic air bearing 84 is formed between the outer surfaces of the first region 81 and the second region 82 and the inner surface of the spindle housing space 42 (gap Sc). The dynamic air bearing 84 is formed while the spindle 43 is rotating at a rotation speed of a predetermined or higher, and is not formed while the spindle 43 is stopped or rotating at a low speed.

[0033] When the dynamic air bearing 84 is formed, the flow rate of the high-pressure air supplied from the high-pressure air supply unit 63 changes to a second flow rate. In other words, the high-pressure air supplied to form the static air bearing 85 is exhausted through the dynamic air bearing 84 and then exhausted from the exhaust ports 53 and 55. When the dynamic air bearing 84 is formed, the exhaust of the static air bearing 85 is obstructed by the dynamic air bearing 84, and the amount of high-pressure air supplied is reduced to a second flow rate.

[0034] The operation of the spindle unit 40 is controlled by the control unit 70. The control unit 70 includes a memory for storing a control program and a processor for executing the control program, and controls the operation of the spindle unit 40 by transmitting operation signals from the control unit 70 to each part of the spindle unit 40. The functional blocks of the control unit 70 include an air supply control unit 71 that controls the on / off switching of the supply of high-pressure air from the high-pressure air source 64, and a motor control unit 72 that controls the rotation, stopping, and rotational speed of the spindle 43. The motor control unit 72 causes the motor 50 to rotate the spindle 43 by controlling the power supply to the stator 52. A rotation detection sensor 73 is provided to detect the rotational speed of the spindle 43, and the rotational speed of the spindle 43 detected by the rotation detection sensor 73 is input to the control unit 70. The control unit 70 controls the rotational speed of the spindle 43 by referring to the detection result from the rotation detection sensor 73. Furthermore, the system may be equipped with an exhaust temperature sensor to measure the temperature of the air exhausted from the exhaust port 55 and a coolant temperature sensor to measure the temperature of the coolant discharged from the coolant outlet 59. The control unit 70 may then detect and control the rotation speed of the spindle 43 by referring to the measurement results of the exhaust temperature sensor and the coolant temperature sensor. Additionally, the air supply control unit 71 may not be provided.

[0035] The control unit 70 may be a control unit that provides overall control for the processing apparatus 10. In this case, in addition to the spindle unit 40, the control unit 70 also controls the operation of the processing feed mechanism 16, the rotation support unit 21, the indexing feed mechanism 23, the lifting mechanism 24, and other components.

[0036] Referring to Figure 3, the air bearing supporting the spindle 43 in the spindle unit 40 will be described. The horizontal axis of the graph in Figure 3 represents the passage of time, with time progressing from left to right in Figure 3. The solid line graph in Figure 3, Air Flow Rate A, shows the change in the flow rate (air flow rate per minute: L / min) of high-pressure air supplied from the high-pressure air source 64 to the gap S in the spindle housing space 42, with the air flow rate increasing as the graph moves upward along the vertical axis. The dashed line graph in Figure 3, Rotation Speed ​​B, shows the change in the rotation speed (revolutions per minute: rpm) of the spindle 43, with the rotation speed increasing as the graph moves upward along the vertical axis. The dashed line graph in Figure 3, Pressure C, shows the pressure (MPa) of the high-pressure air supplied from the high-pressure air source 64.

[0037] The high-pressure air source 64 is capable of supplying high-pressure air at a predetermined pressure C (e.g., 0.5 MPa) higher than atmospheric pressure at a predetermined first flow rate Aa (e.g., 20 L / min).

[0038] The control unit 70 starts supplying high-pressure air from the high-pressure air source 64 during the first period Ta shown in Figure 3. At the start of the first period Ta, the pressure in the gap S within the spindle housing space 42, which is in communication with the external space of the casing 41 through the exhaust ports 53 and 55, is equivalent to atmospheric pressure. Therefore, the high-pressure air sent from the high-pressure air source 64 at a pressure C higher than atmospheric pressure flows into the gap S through the high-pressure air supply unit 62 and the high-pressure air supply unit 63 at a first flow rate Aa, which is the flow rate of the supply capacity of the high-pressure air source 64. By continuously supplying high-pressure air from the high-pressure air source 64 to the gap S at the first flow rate Aa, a hydrostatic air bearing is formed that rotatably supports the spindle 43 via the high-pressure air in the gap S, and the spindle 43 becomes supported.

[0039] Furthermore, during the first period Ta, the control unit 70 drives the motor 50 to cause the spindle 43 to rotate from a stationary state. The rotational speed of the spindle 43, which is supported by the hydrostatic air bearing, is gradually increased, and when it reaches a rotational speed above a predetermined level, in the range of the first region 81 and the second region 82 of the second large diameter portion 45, a dynamic air bearing 84 consisting of a ring-shaped high-pressure air layer is formed in the gap Sc between the outer surface of the spindle 43 and the inner surface of the spindle housing space 42 due to the action of the air rectifier 80 as the spindle 43 rotates. The rotational speed Ba shown in Figure 3 indicates the rotational speed of the spindle 43 in which the dynamic air bearing 84 is formed.

[0040] When the spindle 43 reaches rotational speed Ba and a ring-shaped dynamic air bearing 84 is formed surrounding the first region 81 and the second region 82 of the second large-diameter portion 45, the process transitions from the first period Ta to the second period Tb. The control unit 70 continues to supply high-pressure air from the high-pressure air source 64 even after the transition from the first period Ta to the second period Tb. As a result, in the portion surrounding the third region 83 of the second large-diameter portion 45, the gap Sb is maintained at high pressure by the high-pressure air supplied from the high-pressure air source 64 through the high-pressure air supply unit 63, and a static air bearing 85 is formed following the first period Ta.

[0041] During the second period Tb, when the hydrodynamic air bearings 84 are formed on both sides of the hydrostatic air bearing 85 in the Y-axis direction, the high-pressure air that formed the hydrostatic air bearing 85 continuously flows into the hydrodynamic air bearings 84 on both sides, maintaining the pressure in the gap Sc that forms the hydrodynamic air bearings 84. On the other hand, the amount of high-pressure air flowing from the hydrostatic air bearing 85 to the hydrodynamic air bearing 84 is reduced by the hydrodynamic air bearing 84, resulting in a second flow rate Ab that is less than the first flow rate Aa, thus maintaining the formation of the hydrostatic air bearing 85 and the hydrodynamic air bearing 84. Therefore, during the second period Tb, the hydrodynamic air bearing 84 is formed as the spindle 43 rotates at high speed, and the hydrostatic air bearing 85 is formed while gradually reducing the amount of air supplied per unit time from the high-pressure air source 64 from the first flow rate Aa.

[0042] During the second period Tb, the rotational speed of the spindle 43 gradually increases, and when it reaches the steady-state rotational speed Bb during machining (for example, any rotational speed between 30,000 rpm and 80,000 rpm set in the machining conditions), the control unit 70 maintains the rotational speed of the spindle 43 at a constant level. At the moment the spindle 43 is maintained at the steady-state rotational speed Bb, the system transitions from the second period Tb to the third period Tc. Even after transitioning from the second period Tb to the third period Tc, the control unit 70 continues to supply high-pressure air from the high-pressure air source 64. As a result, similar to the second period Tb, dynamic air bearings 84 are formed on both sides of the static air bearing 85, and a small amount of high-pressure air is supplied from the static air bearing 85 to the dynamic air bearing 84.

[0043] In the third period Tc, as the rotational speed of the spindle 43 stabilizes, fluctuations in the pressure of the air layer around the spindle 43 in the dynamic air bearing 84 are suppressed, and the high-pressure air supplied to form the static air bearing 85 is passed through the dynamic air bearing 84 at a constant second flow rate Ab, which is less than the first flow rate Aa, toward the exhaust ports 53 and 55. For example, if the first flow rate Aa is 20 L / min, the second flow rate Ab is any value in the range of 3 L / min to 10 L / min. In this way, in the third period Tc, the high-pressure air supplied to form the static air bearing 85 is exhausted from both sides of the static air bearing 85 through the dynamic air bearing 84 at a second flow rate Ab, which is less than the first flow rate Aa, toward the exhaust ports 53 and 55.

[0044] In the third period Tc, with the hydrostatic air bearing 85 and the hydrodynamic air bearing 84 formed, a small amount of high-pressure air (second flow rate Ab) is continuously supplied from the high-pressure air source 64 to the gap S (particularly the third region 83 of the second large-diameter portion 45). This allows for the supply of high-pressure air that is higher than the air pressure in the gap S when the hydrodynamic air bearing is formed without air supply (when the supply of high-pressure air from the high-pressure air source 64 is shut off), thereby increasing the pressure of the hydrodynamic air bearing 84. In other words, since the high-pressure air that formed the hydrostatic air bearing 85 flows complementaryly through the ring-shaped air layer that constitutes the hydrodynamic air bearing 84, the spindle 43 can be supported with higher rigidity compared to a hydrodynamic air bearing without air supply. Furthermore, compared to the case of only a hydrostatic air bearing that constantly maintains a large amount of air supply corresponding to the first flow rate Aa (unlike the hydrostatic air bearing 85 in this embodiment, this is a hydrostatic air bearing that does not have hydrodynamic air bearings on either side), it is possible to support the spindle 43 with a smaller air supply (second flow rate Ab) and with the same rigidity as a hydrostatic air bearing.

[0045] As described above, according to the configuration and method of this embodiment, when a dynamic air bearing 84 is formed to rotatably support the spindle 43, it is possible to achieve both high support rigidity of the spindle 43 and suppression of the consumption of high-pressure air for forming the dynamic air bearing 84 and the static air bearing 85. The high support rigidity of the spindle 43 by the dynamic air bearing 84 provides sufficient support for the spindle 43 to withstand machining loads that tilt the spindle 43 when machining hard workpieces (such as SiC and sapphire) that are subjected to machining loads. This prevents problems such as vibration of the spindle 43 or occurrence of machined surface defects due to tilting of the spindle 43 (such as meandering and groove tilting in cutting, and thickness variations in grinding). If the spindle 43 vibrates or tilts, the machining accuracy of the workpiece 1 by the cutting blade 12 may decrease, or damage or uneven wear may occur due to the wobble of the cutting blade 12. Therefore, by suppressing the vibration and tilt of the spindle 43, it is possible to improve machining accuracy and the durability of the cutting blade 12. Reducing the consumption of high-pressure air to form the dynamic air bearing 84 and the static air bearing 85 contributes to reducing the power consumption of the compressor that produces the high-pressure air, thereby enabling energy saving and reduction of operating costs in the machining apparatus 10.

[0046] The control unit 70 has a simple control operation: during the first period Ta shown in Figure 3, it supplies high-pressure air from the high-pressure air source 64 to the gap S, starts the rotation of the spindle 43 by driving the motor 50, and maintains the rotation speed of the spindle 43 at a constant speed once it reaches a steady rotation speed Bb. This operation is easy to implement with minimal control burden. Furthermore, the spindle unit 40 is configured such that a dynamic air bearing 84 is formed on both sides of the static air bearing 85, and an air rectifier 80 is provided at a predetermined position on the spindle 43. Air flows from the static air bearing 85 through the dynamic air bearing 84 to the exhaust ports 53 and 55. This configuration allows for the transition of the air flow rate A (switching from the first flow rate Aa to the second flow rate Ab) as shown in Figure 3, and increases the rigidity of the dynamic air bearing 84. Since it does not require complex changes to the air supply amount or on / off switching of the air supply on the high-pressure air source 64 side, the air supply structure can be made low-cost, readily available, and highly reliable.

[0047] Furthermore, with the hydrostatic air bearing 85 and the hydrodynamic air bearing 84 formed, by continuing to supply high-pressure air at a second flow rate Ab from the high-pressure air source 64 to the gap S, the exhaust port 53 through which the tip 49 of the spindle 43 is inserted, and the exhaust port 55 provided on the motor 50 side, exhaust the high-pressure air that formed the hydrostatic air bearing 85 to the outside of the casing 41 via the hydrodynamic air bearing 84. This exhaust from the exhaust ports 53 and 55 prevents foreign matter from entering the casing 41. In particular, the exhaust port 53 provided on the tip side of the spindle 43, which is close to the cutting blade 12, is located in a place where processing chips and processing water containing processing chips generated when the workpiece 1 is processed by the cutting blade 12 are likely to enter. Therefore, by continuing to exhaust high-pressure air from the exhaust port 53 during processing (third period Tc shown in Figure 3), the effect of preventing processing chips and processing water from entering from the exhaust port 53 is enhanced.

[0048] Furthermore, since the high-pressure air forming the static air bearing 85 is exhausted through the dynamic air bearing 84 to the exhaust ports 53 and 55, it also has the effect of air-cooling the casing 41 and spindle 43 in the parts forming the dynamic air bearing 84.

[0049] When processing a wafer, which is a workpiece 1, with a processing apparatus 10 equipped with the spindle unit 40 as described above, the following steps are performed: a holding step of holding the workpiece 1 on the chuck table 14, a spindle support step of rotatably supporting the spindle 43 within the casing 41, and a processing step of processing the workpiece 1 on the chuck table 14 with a rotating cutting blade 12. In the spindle support step, as explained for the first period Ta in Figure 3, high-pressure air is supplied to the spindle unit 40 at a first flow rate to form a hydrostatic air bearing 85. In the processing step, as explained with reference to Figure 3, the supply of high-pressure air from the high-pressure air source 64 is continued, and high-pressure air is exhausted from the exhaust ports 53 and 55. The spindle 43 is then rotated at a predetermined rotational speed (steady rotational speed Bb) to form a hydrodynamic air bearing 84, and a hydrostatic air bearing 85 is formed between the two hydrodynamic air bearings 84. High-pressure air is then supplied to the hydrostatic air bearing 85 and the hydrodynamic air bearing 84 at a second flow rate Ab. In this state (the state of the third period Tc shown in Figure 3), the workpiece 1 is machined by the cutting blade 12.

[0050] For example, the control unit 70 moves the cutting blade 12 downward in the Z-axis direction (cutting feed) using the lifting mechanism 24 to position it at a height for cutting into the workpiece 1, and while rotating the cutting blade 12, moves the chuck table 14 (the X-axis moving table 20 that supports the chuck table 14) in the X-axis direction (cutting feed) using the machining feed mechanism 16. As a result, cutting is performed along the planned division line extending in the X-axis direction of the workpiece 1.

[0051] Once cutting along one planned division line is completed, the control unit 70 moves the machining unit 11 upward in the Z-axis direction using the lifting mechanism 24, moving the cutting blade 12 away from the workpiece 1. Next, the control unit 70 moves the Y-axis moving table 28 in the Y-axis direction using the indexing feed mechanism 23 (indexing feed), positioning the cutting blade 12 above the end of the next uncut planned division line. Then, similarly to the above, the lifting mechanism 24 moves the cutting blade 12 downward in the Z-axis direction (cutting feed), and the machining feed mechanism 16 moves the chuck table 14 in the X-axis direction (machining feed), performing cutting along the planned division line.

[0052] Once cutting along all planned division lines aligned in the Y-axis direction is complete, the control unit 70 rotates the chuck table 14 by 90 degrees using the rotation support unit 21. As a result, the workpiece 1 on the chuck table 14 is positioned so that multiple uncut planned division lines are aligned in the Y-axis direction (extending toward the X-axis direction). Then, cutting is performed sequentially along all the uncut planned division lines in the same manner as described above.

[0053] Until the series of cutting operations is completed, the motor control unit 72 of the control unit 70 continues to drive the motor 50 to keep the spindle 43 rotating. In addition, the air supply control unit 71 of the control unit 70 continues to supply high-pressure air from the high-pressure air source 64. This allows cutting operations to be performed in the spindle unit 40 with the spindle 43 supported by the hydrostatic air bearing 85 and the hydrodynamic air bearing 84. The spindle unit 40 maintains the pressure by supplying high-pressure air that forms the hydrostatic air bearing 85 to the hydrodynamic air bearing 84, supporting the spindle 43 with high rigidity while reducing the flow rate of high-pressure air from the first flow rate to the second flow rate to reduce the consumption of high-pressure air. As a result, even with reduced consumption of high-pressure air, when the workpiece 1 is a wafer made of a hard material (such as SiC or sapphire) that is subjected to a heavy processing load, the spindle 43 is supported with sufficient strength to withstand the processing load, allowing for high-precision machining.

[0054] Once the cutting process on the workpiece 1 is complete, the motor control unit 72 of the control unit 70 sends a motor stop signal to terminate the power supply to the stator 52 and cut off the power supplied to the motor 50. As a result, the motor 50 no longer generates rotational force, and the spindle 43 stops rotating. As the rotational speed of the spindle 43 decreases, the dynamic air bearing 84 disappears, but the supply of high-pressure air from the high-pressure air source 64 to the gap S continues. With the disappearance of the dynamic air bearing 84, the high-pressure air supplied to the gap S changes from a second flow rate to a first flow rate, and by forming a static air bearing at the first flow rate, the outer surface of the spindle 43 is prevented from colliding with the inner surface of the spindle housing space 42 (galling), and the rotation of the spindle 43 can be stopped smoothly. Once the rotation of the spindle 43 has stopped, the air supply control unit 71 of the control unit 70 stops the supply of high-pressure air from the high-pressure air source 64. As a result, high-pressure air escapes from the gap S, and the support of the spindle 43 by the hydrostatic air bearing is released.

[0055] The processing described above is merely an example and is not limited to it. For example, the processing device 10 may perform edge trimming, which removes the chamfered portion on the outer circumference of the disc-shaped workpiece 1 by cutting. In edge trimming, the cutting blade 12 is positioned on the outer circumference of the workpiece 1 and cut into it, and the rotation support unit 21 is operated to rotate the chuck table 14, thereby removing the chamfered portion along the outer circumference of the workpiece 1.

[0056] Furthermore, the technology disclosed herein is broadly applicable to spindle units that rotatably support a spindle with air bearings, and is not limited to cutting devices such as the processing device 10 of the above embodiment, but can be applied to various processing devices such as grinding devices equipped with grinding wheels (grinding wheels) as processing tools, and polishing devices equipped with polishing pads as processing tools. Grinding devices and polishing devices often have spindles that extend in the Z-axis direction, and the technology disclosed herein can also be applied to support such spindles.

[0057] Next, the spindle unit 100 of the second embodiment shown in Figure 4 will be described. The difference from the spindle unit 40 of the first embodiment shown in Figure 2 is that the spindle unit 100 of Figure 4 has a first region 102 in the second large diameter portion 45 of the spindle 43 in which an air rectifier portion 101 is formed in the central part in the Y-axis direction. The air rectifier portion 101 is a recess or protrusion formed on the outer circumferential surface of the second large diameter portion 45. The second large diameter portion 45 has a second region 103 and a third region 104 on both sides of the first region 102 in the Y-axis direction, and the second region 103 and the third region 104 have smooth outer circumferential surfaces (cylindrical surfaces) in which the air rectifier portion 101 is not formed. Between the inner surface 611 of the second housing portion 61 and the outer surface of the spindle 43, a gap Sc is formed in the area corresponding to the first region 102, and a gap Sb is formed in the areas corresponding to the second region 103 and the third region 104. Gap Sb and gap Sc are in communication. Also, the high-pressure air supply unit 63 is connected to gap Sb.

[0058] The spindle unit 100 has an exhaust port 105 that connects the gap Sc with the outside of the casing 41, separate from the exhaust port 53 on the tip side of the spindle 43. Unlike the spindle unit 40 of the first embodiment, the spindle unit 100 does not have an exhaust port on the rear end side (motor housing 54 side) of the spindle 43. Therefore, the high-pressure air in the gap Sb within the third region 104 is exhausted through the gap Sc and out of the exhaust port 105.

[0059] The control mechanism for forming air bearings in the spindle unit 100 is the same as that for the spindle unit 40 in the first embodiment. The high-pressure air supply unit 63 supplies high-pressure air at a first flow rate to the gap Sb (the range of the second region 103 and the third region 104), thereby forming a hydrostatic air bearing 107 in the gap Sb corresponding to the second region 103, and a hydrostatic air bearing 108 in the gap Sb corresponding to the third region 104. When the spindle 43 is rotated to a rotational speed above a predetermined level, in the range of the first region 102, the high-pressure air in the gap Sc rotates due to the action of the air rectifier unit 101 as the spindle 43 rotates, and a hydrodynamic air bearing 106 is formed in the gap Sc. In this way, the hydrodynamic air bearing 106 is formed between the two spaced-apart hydrostatic air bearings 107 and 108.

[0060] For the gap Sb in the second region 103, since no dynamic air bearing is formed between the location where the static air bearing 107 is formed and the exhaust port 53, the exhaust from the static air bearing 107 to the exhaust port 53 is obstructed by the dynamic air bearing, and the effect of reducing the supply of high-pressure air to the second flow rate is not obtained. In contrast, for the gap Sb in the third region 104, since there is no exhaust path to the rear end side (motor housing 54 side) of the spindle 43, the high-pressure air supplied to form the static air bearing 108 in the gap Sb is exhausted from the exhaust port 105 via the dynamic air bearing 106 in the gap Sc. Consequently, the exhaust from the static air bearing 108 is obstructed by the dynamic air bearing 106, and the supply of high-pressure air to form the dynamic air bearing 106 and the static air bearing 108 is reduced to the second flow rate. Furthermore, because the dynamic air bearing 106 receives high-pressure air from the static air bearing 108, it can support the spindle 43 with greater rigidity compared to a dynamic air bearing without an air supply.

[0061] Next, the spindle unit 110 of the third embodiment will be described with reference to Figures 5 and 6. The spindle unit 110 applies the same configuration as the dynamic air bearing 84 and static air bearing 85 at the second large diameter portion 45 (radial bearing) of the spindle unit 40 of the first embodiment to the first large diameter portion 44 (thrust bearing) of the spindle 43. The casing 41 of the spindle unit 110 is provided with exhaust ports 53 and 603 on the tip side of the spindle 43 and an exhaust port 55 on the rear end side of the spindle 43. The exhaust port 603 exhausts air to the outside of the casing 41 via an exhaust path that communicates with the inner surface 601 of the first housing portion 60.

[0062] As shown in Figure 5, an air rectifier 111 is formed on the Y-axis end face of the first large-diameter portion 44 of the spindle 43. The air rectifier 111 is a concave or convex portion, and multiple arrowhead-shaped portions are present on the Y-axis end face of the first large-diameter portion 44, with their tips pointing in the opposite direction to the rotational direction R of the spindle 43. The air rectifier 111 is provided in a ring shape in the first region 112 on the inner (center side) and the second region 113 on the outer (outer circumference side) in the radial direction of the first large-diameter portion 44. Between the first region 112 and the second region 113, there is no air rectifier 111 and it is a smooth plane third region 114. Figure 5 shows one end face of the first large-diameter portion 44 in the Y-axis direction, but the air rectifier 111 is also formed in a similar arrangement on the opposite end face of the first large-diameter portion 44.

[0063] As shown in Figure 6, a gap Sd is formed between the pair of side surfaces 602 of the first housing section 60 and the end faces on both sides of the first large-diameter section 44 of the spindle 43, in the area corresponding to the third region 114, and a gap Se is formed in the areas corresponding to the first region 112 and the second region 113. The gap Sd and the gap Se are in communication. The high-pressure air supply section 62 is connected to the gap Sd.

[0064] The control mechanism for forming the air bearing in the spindle unit 110 is the same as that for the spindle unit 40 in the first embodiment. The high-pressure air supply unit 62 supplies high-pressure air to the gap Sd (the range of the third region 114) at a first flow rate, thereby forming a static air bearing 116 in the gap Sd. When the spindle 43 is rotated to a rotational speed above a predetermined level, the high-pressure air in the gap Se rotates in the range of the first region 112 and the second region 113 due to the action of the air straightening unit 111 as the spindle 43 rotates, and a dynamic air bearing 115 is formed in the gap Se. In this way, on both sides of the first large-diameter portion 44, the dynamic air bearings 115 are formed outside the static air bearing 116 in the radial direction of the first large-diameter portion 44.

[0065] By forming dynamic air bearings 115 on both sides of the static air bearing 116, the high-pressure air forming the static air bearing 116 is exhausted through the dynamic air bearings 115 from exhaust ports 53, 603, and 55. Consequently, the exhaust of the static air bearing 116 is obstructed by the dynamic air bearings 115, resulting in the effect of reducing the amount of high-pressure air supplied to form the dynamic air bearing 115 and the static air bearing 116 to a second flow rate. Furthermore, because the dynamic air bearing 115 receives high-pressure air from the static air bearing 116, it can support the spindle 43 with higher rigidity compared to a dynamic air bearing without air supply.

[0066] The spindle unit 110 may also be configured without the exhaust port 55 shown in Figure 6. In this case, the high-pressure air from the static air bearing 116 formed in the gap Sd to the right of the first large-diameter portion 44 in Figure 6 is exhausted through the dynamic air bearing 115 from the exhaust port 53 and the exhaust port 603. The sum of the air flow rates exhausted from the exhaust port 53 and the exhaust port 603 becomes the second flow rate.

[0067] Next, the spindle unit 120 of the fourth embodiment will be described with reference to Figures 7 and 8. The spindle unit 120 applies the same configuration as the dynamic air bearing 106 and static air bearings 107 and 108 in the second large diameter portion 45 (radial bearing) of the spindle unit 100 of the second embodiment to the first large diameter portion 44 (thrust bearing) of the spindle 43.

[0068] As shown in Figure 7, an air rectifier 121 is formed on the Y-axis end face of the first large-diameter portion 44 of the spindle 43. The air rectifier 121 is a concave or convex portion, and multiple arrowhead-shaped portions are present on the Y-axis end face of the first large-diameter portion 44, with their tips pointing in the opposite direction to the rotational direction R of the spindle 43. The air rectifier 121 is provided in a ring shape in the central first region 122 in the radial direction of the first large-diameter portion 44. The air rectifier 121 is not formed on either side of the first region 122 in the radial direction of the first large-diameter portion 44, which are smooth planes forming the second region 123 and third region 124. Figure 7 shows one end face in the Y-axis direction of the first large-diameter portion 44, but the air rectifier 121 is also formed in a similar arrangement on the opposite end face of the first large-diameter portion 44.

[0069] As shown in Figure 8, a gap Sd is formed between the pair of side surfaces 602 of the first housing section 60 and the end faces on both sides of the first large-diameter section 44 of the spindle 43, in the areas corresponding to the second region 123 and the third region 124, and a gap Se is formed in the area corresponding to the first region 122. The gap Sd and the gap Se are in communication. The high-pressure air supply section 62 is connected to the gap Sd.

[0070] The spindle unit 120 is equipped with an exhaust port 53 and an exhaust port 604 at the tip of the spindle 43. The exhaust port 604 exhausts air to the outside of the casing 41 via an exhaust path that communicates with the side surface 602 of the first housing section 60 (the side surface 602 located on the left side in Figure 8 of the pair of side surfaces 602). Therefore, the high-pressure air in gaps Sd and Se has a second flow rate, which is the sum of the air flow rates exhausted from exhaust port 53 and exhaust port 604.

[0071] The control mechanism for forming air bearings in the spindle unit 120 is the same as that for the spindle unit 40 in the first embodiment. The high-pressure air supply unit 62 supplies high-pressure air at a first flow rate to the gap Sd (the range of the second region 123 and the third region 124), thereby forming a hydrostatic air bearing 126 in the gap Sd corresponding to the second region 123, and a hydrostatic air bearing 127 in the gap Sd corresponding to the third region 124. When the spindle 43 is rotated to a rotational speed above a predetermined level, a hydrodynamic air bearing 125 is formed in the gap Se in the range of the first region 122 due to the action of the air rectifier unit 121 as the spindle 43 rotates. In this way, on both sides of the first large-diameter portion 44, a hydrodynamic air bearing 125 is formed between two hydrostatic air bearings 126 and 127 spaced radially apart from each other.

[0072] In the first large-diameter section 44, the location where the hydrostatic air bearing 127 is formed on the left side of Figure 8 is not formed between the hydrostatic air bearing 127 and the exhaust port 53. Therefore, the exhaust air from the hydrostatic air bearing 127 to the exhaust port 53 is not obstructed by the hydrostatic air bearing, and the effect of reducing the supply of high-pressure air to the second flow rate is not obtained. In contrast, for the hydrostatic air bearing 126 on the left side of Figure 8 and the hydrostatic air bearings 126 and 127 on the right side of Figure 8, the high-pressure air supplied to form each hydrostatic air bearing 126 and 127 is exhausted through at least one of the hydrostatic air bearings 125 on both sides of the first large-diameter section 44 (left and right sides of Figure 8) to the exhaust port 53 and the exhaust port 604. Consequently, the exhaust from these static air bearings 126 and 127 is obstructed by the dynamic air bearing 125, and the amount of high-pressure air supplied to form the dynamic air bearing 125 and the static air bearings 126 and 127 is reduced to a second flow rate. Furthermore, because the dynamic air bearings 125 on both sides of the first large-diameter section 44 receive high-pressure air from the static air bearings 126 and 127, the spindle 43 can be supported with higher rigidity compared to dynamic air bearings without air supply.

[0073] As described above, the spindle unit and processing apparatus of this disclosure can reduce air consumption while supporting the spindle with an air bearing strong enough to withstand the processing load, thereby reducing power consumption for producing high-pressure air, and improving the durability of the spindle unit and the processing accuracy of the processing tool. Furthermore, by applying the spindle unit and processing apparatus of this disclosure to a wafer processing method, it is possible to support the spindle with high rigidity while suppressing the air consumption of the air bearing, thereby processing wafers with high precision at a low cost.

[0074] The illustrated embodiments are preferred examples of the present disclosure and do not preclude the application of configurations or methods different from those described above. For example, it is preferable to have a first large-diameter portion 44 and a second large-diameter portion 45, as in the spindle 43 of each embodiment, and to form a thrust bearing at the location of the first large-diameter portion 44 and a radial bearing at the location of the second large-diameter portion 45 when forming the air bearing. However, it is also possible to apply the contents of the present disclosure to the support of a spindle with a constant overall diameter without a first large-diameter portion 44 or a second large-diameter portion 45. In other words, regardless of the specific shape of the spindle, any spindle unit that can include at least a hydrostatic air bearing formed by supplying high-pressure air at a first flow rate, a hydrodynamic air bearing formed outside both hydrostatic air bearings or between two spaced hydrostatic air bearings, which allows the high-pressure air supplied to form the hydrostatic air bearings to pass through at a second flow rate less than the first flow rate, and an exhaust port for exhausting the high-pressure air that formed the hydrostatic air bearings through the hydrodynamic air bearings is subject to the application of the present disclosure.

[0075] Furthermore, the embodiments of the present invention are not limited to the embodiments and modifications described above, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Moreover, if the technical idea of ​​the present invention can be realized in a different way by advances in the art or by other derived arts, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial applicability]

[0076] By applying the technology disclosed herein, it becomes possible to support a spindle with an air bearing in a rotatable manner, while reducing air consumption, thereby improving machining accuracy, reducing operating costs and environmental impact in machining equipment that rotates a workpiece with a spindle. [Explanation of symbols]

[0077] 1: Workpiece (wafer) 10: Processing equipment 11: Processing Unit 12: Cutting blade (machining tool) 14: Chuck Table 16: Machining feed mechanism 21: Rotating support part 23: Indexing feed mechanism 24: Lifting mechanism 40: Spindle Unit 41: Casing 42: Spindle housing space 43: Spindle 44: First large diameter section 45: Second large diameter section 46: Blade Mount 50: Motor 53: Exhaust vent 54: Motor housing 55: Exhaust vent 56: Cooling water channel 57: Cooling water supply port 58: Cooling water source 59: Cooling water outlet 60: First containment unit 61: Second containment unit 62: High-pressure air supply unit 63: High-pressure air supply unit 64: High-pressure air source 65: Air supply path 66: Air supply port 70: Control Unit 71: Air supply control unit 72: Motor Control Unit 73: Rotation detection sensor 80: Air rectifier 81: 1st area 82:Second area 83:Third area 84: Dynamic air bearings 85: Static air bearing 100: Spindle Unit 101: Air rectifier 102: 1st area 103:Second area 104:Third area 105: Exhaust port 106: Dynamic air bearing 107: Static air bearing 108: Static air bearing 110: Spindle Unit 111: Air rectifier 112: 1st area 113:Second area 114:Third area 115: Dynamic air bearing 116: Static air bearing 120: Spindle Unit 121: Air rectifier 122: 1st area 123:Second area 124: Third area 125: Dynamic air bearing 126: Static air bearing 127: Static air bearing 603: Exhaust vent 604: Exhaust vent A: Air flow rate Aa: 1st flow rate Ab: 2nd flow rate B: Spindle speed Ba: Rotational speed at which a dynamic air bearing is formed Bb: Steady-state rotational speed C: Pressure of high-pressure air S: Gap Sa: gap Sb: gap Sc: gap Sd: gap Se: gap

Claims

1. A spindle unit comprising: a spindle with a workpiece attached to its tip that rotates; a casing having a gap on the outer surface of the spindle and an inner surface facing the outer surface; an air bearing in which high-pressure air is interposed in the gap to allow the casing to rotate the spindle; and a motor that rotates the spindle, The air bearing comprises a hydrostatic air bearing formed by supplying high-pressure air at a first flow rate, a dynamic air bearing formed outside the hydrostatic air bearing, or between two spaced hydrostatic air bearings, by rotating the spindle at a predetermined rotational speed, which allows the high-pressure air supplied to form the hydrostatic air bearing to pass through at a second flow rate less than the first flow rate, and an exhaust port for exhausting the high-pressure air that formed the hydrostatic air bearing through the dynamic air bearing. Spindle unit.

2. A processing apparatus comprising a chuck table for holding a workpiece and a processing unit for processing the workpiece with a rotating processing tool, The processing unit includes the spindle unit described in claim 1, The system includes a control unit that supplies high-pressure air to the gap at a preset first flow rate to form a static air bearing, rotates the spindle to a predetermined rotational speed to form a dynamic air bearing, and, in conjunction with the formation of the dynamic air bearing, supplies high-pressure air to the static air bearing and the dynamic air bearing at a second flow rate. Processing equipment.

3. A method for processing a wafer using the processing apparatus described in claim 2, A holding step of holding the wafer, which is the workpiece, on the chuck table, A spindle support step involves supplying high-pressure air to the spindle unit at the first flow rate to form a hydrostatic air bearing and rotatably support the spindle, The process includes a step of processing a wafer by rotating the spindle at a predetermined rotational speed to form the dynamic air bearing, and then supplying high-pressure air to the static air bearing and the dynamic air bearing at the second flow rate. Wafer processing methods.

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