JPH10296617A - Polishing device and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the equality of the face of a workpiece to be polished even if there is a primary factor that deteriorates the equality of the face of a workpiece to be polished after being polished by making it possible to positively and accurately adjust polishing pressure. SOLUTION: This polishing method is used in such a way that push pressure of a polishing pad 8 against a wafer W is adjusted according to the polishing pressure preset according to the relative position of the polishing face 8a of the polishing pad 8 to the face of the wafer W to be polished while relatively moving the polishing face 8a of the rotating polishing pad 8 in one plane made to slide on the face of the wafer W to be polished. Through such operation, the face of the wafer W to be polished is polished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polishing apparatus and a polishing method capable of improving the uniformity of the surface of an object to be polished having a flat surface such as a semiconductor substrate such as a silicon wafer.

[0002]

2. Description of the Related Art For example, in an LSI manufacturing process, it is important to flatten an interlayer insulating film or another film. Various means have been proposed as a technique for planarization. In recent years, a CMP (Chemical Mechanical Polishing) method which applies a mirror polishing technique for a silicon wafer has attracted attention and is utilized. A method for flattening has been developed.

[0003]

A conventional wafer flattening technique using the CMP method is a process in which a polishing pad is pressed against a wafer surface by a driving means such as an air cylinder during polishing. I do. However, conventionally, the mechanical transmission loss of the driving means and the unevenness of the pressing force have not been considered, and the mechanical transmission loss of the driving means and the uneven pressing force do not allow the polishing pad to be effectively applied to the wafer. Uneven polishing pressure was generated. For this reason, uneven polishing pressure has been a factor of deteriorating the uniformity of the wafer surface after polishing. Note that the uniformity of the wafer surface refers to the variation in the amount of removal processing on the entire surface of the wafer.

On the other hand, due to the unevenness of the surface of the wafer itself, the effective area of the polished surface of the polishing pad fluctuates, the amount of polishing of the projections on the wafer surface increases, and the amount of polishing of the recesses decreases. This is a factor of deteriorating the uniformity of the processed wafer surface. In addition, the unevenness of the polishing surface of the polishing pad is
Since it is directly transferred to the wafer surface, this is also a factor of deteriorating the uniformity of the wafer surface after polishing. Further, the distribution of the slurry as the abrasive supplied between the wafer and the polishing pad during the polishing process differs between the slurry supply position and the inner and outer peripheral sides of the polishing pad. Non-uniformity has also been a factor in deteriorating the uniformity of the wafer surface. It is difficult to fundamentally remove the unevenness of the surface of the wafer itself, the unevenness of the polishing surface of the polishing pad, and the unevenness of the slurry distribution as described above.

[0005] Incidentally, the removal processing amount by polishing is PR
According to a relational expression called the ESTON expression, the polishing pressure,
It is proportional to the relative speed between the polishing pad and the object to be polished and the processing time. Therefore, even if there is unevenness of the surface of the wafer itself, non-uniformity of the polishing surface of the polishing pad, or non-uniformity of slurry distribution as described above, the polishing pressure is actively adjusted during the polishing process. It is considered that this can improve the uniformity of the wafer surface.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and allows a polishing pad to positively and accurately adjust a polishing pressure in polishing a surface to be polished by a polishing pad. It is an object of the present invention to provide a polishing apparatus and a polishing method capable of improving the uniformity of a polished surface to be polished even if there is a factor that deteriorates the uniformity of the polished surface.

[0007]

A polishing apparatus according to the present invention comprises: holding means for holding an object to be polished; a polishing pad having a polishing surface for polishing the surface to be polished; and a rotating pad for the polishing pad. Rotation driving means for freely holding and rotating the polishing surface of the polishing pad by pressing the polishing surface of the polishing pad relatively to the polishing surface of the polishing target, and the polishing surface of the polishing pad and the polishing surface of the polishing pad. Moving means for moving the polishing pad relative to the surface to be polished of the polishing surface of the polishing pad by the rotation driving means; And pressure control means for outputting a control signal to the rotary drive means based on the detection signal of the pressing force detection means so that the polishing pressure generated on the object to be polished has a desired value.

In the polishing apparatus of the present invention, since the polishing pressure is controlled to a desired value by the pressure control means, it is possible to improve the uniformity of the surface to be polished by the fluctuation of the polishing pressure.

The polishing apparatus of the present invention preferably comprises
The rotation driving means includes: a spindle that rotatably holds the polishing pad facing the object to be polished; a spindle that rotates the spindle; a slider that holds the spindle; and a slider that holds the slider. A guide movably held in the axial direction, a sub-slider provided movably along the axial direction of the main shaft, and a driving unit for moving the sub-slider along the main axis direction;
A connecting member for connecting the slider and the sub-slider;

The pressing force detecting means preferably detects a force acting on the connecting member from the sub-slider to the slider in an axial direction of the main shaft.

Preferably, the axis of the main shaft, the guide, and the point of action of the connecting member with respect to the slider are located in a plane orthogonal to the surface to be polished.

A polishing method according to the present invention is a polishing method for polishing a surface to be polished by relatively moving the polishing surface of a rotating polishing pad in a plane while slidingly contacting the surface to be polished. By adjusting the pressing force of the polishing pad against the object to be polished in accordance with a polishing pressure set in advance according to the relative position between the polishing surface of the polishing pad and the surface to be polished of the object to be polished, The surface to be polished is polished.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall perspective view of a polishing apparatus according to an embodiment of the present invention. A polishing apparatus 30 according to the embodiment shown in FIG. 1 is used for polishing a surface to be polished of a wafer as a polishing object. Device. FIG.
3A is a schematic configuration diagram of a rotation driving mechanism of a polishing pad and a wafer movement holding mechanism of the polishing apparatus shown in FIG. 1; FIG.
Is a top view, (b) is a front view, and (c) is a side view. FIG. 3 is a sectional view of a main part near the polishing pad, and FIG. 4 is a bottom view of the polishing pad.

As shown in FIG. 1, a rotary drive mechanism of the main spindle of the polishing apparatus 30 for holding the polishing pad 8 is provided with a main spindle 32 for rotating the polishing pad 8 and a main spindle 32 movable in the Z-axis direction. Z-axis slider 73 to be held
And a load cell 81 having one end fixed to two places on the upper surface of the Z-axis slider 73 for detecting a load, and a sub-slider 82 fixed at the other end of the load cell 81 and supported to be movable in the Z-axis direction. And a Z-axis servo motor 74 for driving the sub-slider 82 in the Z-axis direction. A pressure control system, which will be described later, is applied to the rotation drive mechanism of the present embodiment, so that the pressure of the polishing pad 8 on the wafer W can be controlled. On the other hand, a wafer movement holding mechanism for holding and moving the wafer W of the polishing apparatus 30 is mainly configured by the X-axis table 6.

The Z-axis slider 73 is movable in the Z-axis direction along a Z-axis guide 72 provided on the side surface of the column 71. The movement of the Z-axis slider 73 causes the main spindle 32 to move in the Z-axis direction. The load cell 81 having one end fixed to the Z-axis slider 73 detects a load applied in the Z-axis direction. The other end of the load cell 81 is fixed to the sub-slider 82, and moves in the Z-axis direction together with the Z-axis slider 73 while being held by the load cell 81.

The load cell 81 is a force measuring device using a strain gauge. The principle structure of the load cell 81 is such that a strain gauge is adhered to a side surface of an elastic member such as a metal, and the strain generated in the elastic member is detected. Detect the applied load. In the present embodiment, the load cell 81 can detect a load in the Z-axis direction. The features of the load cell are small size, high rigidity, high natural frequency, and the like. Further, as shown in FIG. 2A, the load cell 81 has an action point P with respect to the Z-axis slider 73, the axis O of the main shaft, and the Z-axis guide 7.
2 are fixed so as to be located on a straight line T. That is, the point of action P of the load cell 81 with respect to the Z-axis slider 73, the axis O of the main shaft, and the Z-axis guide 72 are located on the same plane including the straight line T, and this plane is the holding surface of the X-axis table 6. Are orthogonal to.

As shown in FIG. 2, the sub-slider 82
The sub-slider 82 is movable along the sub-slider guide 74a in the Z-axis direction. The sub-slider 82 is driven by a Z-axis servo motor 74 connected via a coupling 89 to a ball screw 87 screwed in the Z-axis direction. Is driven in the Z-axis direction.

As shown in FIGS. 1 and 2, one ends of two wires 84 are connected to both ends of the upper surface of the Z-axis slider 73, respectively. As shown in FIG. 2, counterweights 86 are respectively connected to the other ends of these wires 84, and these counterweights 86 are suspended via pulleys 83. The load of the counterweight 86 is substantially equal to the load of the Z-axis slider 73, whereby the load of the Z-axis slider 73 applied to the load cell 81 is almost canceled, and the load applied to the load cell 81 is reduced. It has been reduced. Therefore, the difference between the load of the counterweight 86 and the load of the Z-axis slider 73 is given to the load cell 81 as a preload.

The main spindle 32 is provided with a Z-axis slider 73.
, And can be moved in the Z-axis direction. The main spindle 32 has a main shaft 36 and a main shaft housing 38 as shown in FIG. Spindle 3
A platen 34 is attached and fixed to the lower part of the plate 6. Surface plate 34
A nozzle hole 42 is formed in the center of the nozzle tube 40. The nozzle hole 42 is inserted into the nozzle hole 42 so that the lower end of the nozzle tube 40 does not come into contact with the nozzle hole 42. From the nozzle tube 40, a slurry as a polishing liquid is discharged. The nozzle tube 40 does not rotate, and the platen 34 can be rotated by the main shaft 36. The main shaft 36 is driven to rotate by a motor (not shown). As the slurry supplied from the nozzle tube 40, a polishing slurry capable of performing chemical mechanical polishing is used. For example, powdery silicon oxide (SiO 2)
₂ ) An aqueous solution of potassium hydroxide (KOH) and the like are used.

As shown in FIGS. 3 and 4, in this embodiment, the nozzle hole 42 has a slurry distributing end plate 4 at its lower part.
6 is formed on the surface plate 34 so that 6 remains. Moreover, a radial groove 44 is formed on the lower surface of the surface plate 34, and the center of the radial groove 44 communicates with the nozzle hole 42.

The X-axis table 6 is rotatably mounted on a slider movably provided in the X-axis direction along a rail (not shown). Since the X-axis table 6 rotates at a relatively low speed, it is rotationally driven by a motor, a pulley, a flat belt, and the like. The size of the X-axis table 6 is not particularly limited, but is, for example, a disk having a diameter of about 200 mm. On the upper part of the X-axis table 6, a chuck made of a porous member or the like is mounted. The rotary shaft for rotating the X-axis table 6 has a vacuum passage formed along the axis thereof. By evacuating through this passage, the wafer W is vacuum-adsorbed on the surface of the X-axis table 6.

As shown in FIGS. 3 and 4, a ring-shaped polishing pad 8 is attached to the outer periphery of the lower surface of the surface plate 34 by bonding or the like. The center of rotation of the ring-shaped polishing pad 8 is
The axis coincides with the axis O of the spindle spindle 32 and the spindle 36 described above. The polishing pad 8 is made of a porous viscoelastic material such as polyurethane foam. The outer diameter D of the polishing pad 8 is substantially equal to or smaller than the outer diameter of the wafer W. The radial groove 44 is formed to extend to the inner peripheral surface of the polishing pad 8. The diameter D of the ring-shaped polishing pad 8 is 200 m in the present embodiment.
m and the radial width d is 20 mm.

Also, as shown in FIG.
Is, for example, an unpolished wafer W stored in a wafer cassette 61 carried by a transfer device (not shown).
When the wafer W on the X-axis table 6 is polished and unloaded, the wafer W on the load buffer 63 is removed through the opening 90 in FIG. A loader chuck 55 for loading the X-axis table 6, an unloader chuck 64 for holding the wafer W polished on the X-axis table 6 through the opening 90 by vacuum suction and carrying the wafer W to the unload buffer 65, The surface of the wafer W placed on the buffer 65 is cleaned and the wafer cassette 6 is cleaned.
7 is provided.

Next, the operation of the polishing apparatus 30 according to the present embodiment will be described. First, the unpolished wafer W stored in the wafer cassette 61 is placed on the load buffer 63 by the loader chuck 55. When the polishing of the wafer W on the X-axis table 6 is completed, the unloader chuck 6
When the wafer W is unloaded, the loader chuck 55 carries the wafer W placed on the load buffer 63 onto the X-axis table 6, and places the wafer W on the polished surface in the figure. Then, the suction device of the X-axis table 6 starts suction, a suction force is generated on the surface thereof, and the wafer W mounted on the X-axis table 6 is suctioned to the X-axis table 6.

Next, by driving the spindle 32, the surface plate 34 is rotated, for example, at a rotation speed of 1000 to 3000.
Rotate at high speed of rpm. Further, the X-axis table 6 is rotated together with the wafer W at a low speed of, for example, several tens of rpm by driving the motor. In addition, a slider provided movably in the X-axis direction along a rail (not shown) is moved in the X-axis direction along the rail so that the polishing pad 8 is located above the wafer W. At this time, the slurry from the slurry supply device is discharged from the nozzle hole 42 through the nozzle tube 40 shown in FIG. 3, and is supplied to the inner peripheral side of the polishing pad 8 through the radial 44 by centrifugal force due to rotation. .

Then, by driving the Z-axis servo motor 74, the sub-slider 82 is lowered in the Z-axis direction. As the sub-slider 82 descends in the Z-axis direction, the Z-axis slider 73 connected to the sub-slider 82 and the load cell 81 descends in the Z-axis direction. At this time, the load cell 81 detects only the difference between the load on the counterweight 86 and the load on the Z-axis slider 73.

When the main spindle 32 held by the Z-axis slider 73 is lowered to a predetermined position in the Z-axis direction and the polished surface 8a of the polishing pad 8 comes into contact with the polished surface of the wafer W, a state as shown in FIG. Becomes The polishing surface 8a of the polishing pad 8 slides on the surface to be polished of the wafer W held on the holding surface 6a of the X-axis table 6, and the X-axis table 6 moves by a driving force from a driving device (not shown). Wafer W moves with respect to polishing pad 8 (moves in the direction of the radius of rotation)
I do. Thereby, polishing is performed. The moving speed of the X-axis table 6 is, for example, 5 to 400 (mm).
/ Min). During this movement, the polishing pad 8 and the wafer W rotate together. The polishing pad 8 includes a main shaft 36.
, A pressing force F acts in the Z-axis direction. The pressing force F is a force having a magnitude corresponding to the driving position of the sub-slider 82 in the Z-axis direction.

As described with reference to FIG. 2A, the point of action P of the load cell 81 with respect to the Z-axis slider 73, the axis O of the main shaft, and the Z-axis guide 72 are located on the same plane including the straight line T. This plane is the holding surface 6 of the X-axis table 6.
It is orthogonal to a. Therefore, the pressing force F acting on the polishing pad 8 can be applied in the Z-axis direction and on the axis O of the main shaft 36. For this reason, the mechanical deformation of the main shaft 36 due to the reaction to the pressing force F acting on the polishing pad 8 can be restricted almost only in the Z-axis direction. Further, with the above structure, when the polishing pad 8 receives a load in the X-axis direction by the polishing process, the load cell 81
And the sub-slide 82 undergoes mechanical deformation in the X-axis direction. However, there is no effect on the pressing force F, and the mechanical deformation of the main shaft 36 can be limited almost only in the Z-axis direction. Does not participate in polishing. As a result, during the polishing, the perpendicularity between the axis O of the main shaft 36 and the holding surface of the X-axis table 6 can be kept constant, and the polishing accuracy can be improved.

Also, the Z-axis slider 73 of the load cell 81
Are located on the same plane including the straight line T, and the plane is orthogonal to the holding surface 6a of the X-axis table 6. Therefore, the load cell 81 does not receive a geometrical error based on Abbe's principle to detect the force in the Z-axis direction, and the pressing force F to the polishing pad 8 is accurately detected by the load cell 81. Therefore, when the pressure control system according to the present embodiment described later is applied to the polishing apparatus 30, it is possible to generate an accurate polishing pressure between the polishing surface 8a of the polishing pad 8 and the surface to be polished of the wafer W. it can.

When the polishing process by the polishing apparatus 30 is completed, the wafer W is carried from the opening 30 shown in FIG. 1 to the unload buffer 65 by the unloader chuck 64, and is cleaned by the wafer cleaning brush 66. Is stored in.

FIG. 6 is a block diagram showing an example of a pressure control system applied to the rotation drive mechanism of the polishing apparatus 30 according to the present embodiment. The pressure control system according to the present embodiment includes a pressure control device 201 and an operation panel 202.
It is composed of Detection signal 81s of load cell 81
Is input to the pressure control device 201. Operation panel 20
2 displays various control information signals 201sb output from the pressure control device 201,
01 is input with the data signal 202s. Pressure control device 2
01 is a position command signal 2 for the Z-axis servomotor 74.
01sa is output. In addition, from the main control device 301 that performs overall operation control of the polishing apparatus 30 according to the present embodiment, various control signals 301s are output to the pressure control device 201, and the main control device 301 sends the control signal 301s to the main control device 301. Various control signals 201sc are output.

FIG. 7 is a control block diagram of the pressure control system according to the present embodiment. As shown in FIG. 7, the pressure control device 201 includes a polishing pressure setting unit 205, a comparison operation unit 207, a movement amount conversion unit 206, and a polishing pressure calculation unit 20.
8 and the load cell 81
Is input from the pressure control device 201 and the Z-axis drive system 20 including the Z-axis servomotor 74 and the like.
1, the movement signal r is output. The detection signal Vl of the load cell 81 is determined by the polishing pressure calculation unit 208 of the pressure control device 201.
The polishing pressure calculator 208 calculates the current polishing pressure P from the digital signal D. The polishing pressure setting unit 205 holds a preset polishing pressure Pr set in advance, and the comparison polishing unit 207 compares the set polishing pressure Pr with the polishing pressure P calculated by the polishing pressure calculation unit 208. The pressure difference signal Pe is output to the movement amount conversion unit 206. The movement amount converter 206 calculates a rotation amount (movement amount) r of the Z-axis servo motor 74 to be rotated based on the pressure difference signal Pe so that the pressure difference signal Pe becomes zero,
Output to the Z-axis drive system 210. The Z-axis drive system 201
The driving force of the shaft servomotor 74 generates a pressing force F for pressing the polishing pad 8. The pressing force F is detected by the load cell 81. The polishing pressure setting unit 205 and the moving amount conversion unit 206 in the control block diagram of FIG.
The polishing pressure calculator 208 can also be realized by hardware, but in the present embodiment, a case in which these are realized by software will be described.

FIG. 8 shows a pressure control device 2 according to this embodiment.
FIG. 2 is a configuration diagram illustrating a configuration example of hardware No. 01. In FIG. 8, the pressure control device 201 is a computer 22
1, an A / D converter 223, a D / A converter 225,
It comprises a RAM 227, a ROM 229, DIO interfaces 233 and 234, and an external storage device 231.

The computer 221 performs various calculations.
The A / D converter 223 converts the analog detection signal of the load cell 81 into a digital signal and inputs the digital signal to the computer 221. The D / A converter 225 converts the position command for the Z-axis servo motor 74 calculated by the computer 221 into an analog signal and outputs the analog signal to the servo driver 74a of the Z-axis servo motor 74. The RAM 227 is a computer 22
1 is a memory for storing and executing programs and data to be executed. The ROM 229 is a memory for storing a program for starting the computer 221. I / F233
Is a circuit that performs an interface between the operation panel 202 and the computer 221. The DIO 234 is a circuit that performs an interface between the main controller 301 and the computer 221. The external storage device 231 is a device that stores various data, and is, for example, a floppy disk device or a hard disk device.

In the pressure control system according to this embodiment,
A set polishing pressure Pr to be held by the polishing pressure setting unit 205 described in FIG. 7 is prepared in advance. This set polishing pressure Pr is obtained by simulation. The amount of polishing of the wafer W by the polishing pad 8 is related to each state quantity by the following equation (1) called a PRESTON equation. H = Kp · P · V · t (1) where H is a polishing amount, Kp is a proportional constant, P is a polishing pressure, V
Is the polishing rate and t is the processing time. Also, the polishing pad 8
When the pressing force F is applied to the surface, the polishing pressure P is calculated by the following equation (2).
It is represented by P = F / A (2) where A is a contact (sliding contact) area between the polishing pad 8 and the wafer W.

When the polishing pad and the wafer W are relatively moved, the contact area A between the polishing pad 8 and the wafer W changes. That is, from the equations (1) and (2), it can be seen that the polishing pressure P fluctuates according to the change in the contact area A even when the pressing force F is constant. When the polishing pressure P fluctuates, the uniformity of the polished surface of the wafer W deteriorates. When polishing is performed with a constant pressing force F, the distribution of the amount of polishing on the surface to be polished of the wafer W is, for example, a distribution as shown by a solid line K1 in FIG.
Therefore, a polishing pressure P for making the distribution of the polishing amount uniform as indicated by a solid line K1 shown in FIG. 9 is derived by simulation based on the above equations (1) and (2). Table 1 shows an example of the polishing pressure P derived by simulation.
Shown in

[Table 1] Table 1 shows the value of the polishing pressure P according to the position of the wafer W, and the polishing pressure P indicates a magnification with respect to the reference polishing pressure. The reference polishing pressure is, for example, on the order of 100 to 300 gf / cm ² . The polishing conditions at the time of the simulation include, for example, rotating the polishing pad 8 at 1500 rpm, rotating the wafer W at 50 rpm, and keeping the relative movement speed (processing time) between the polishing pad 8 and the wafer W constant.

When polishing is performed in accordance with the distribution of the polishing pressure P shown in Table 1, the distribution of the polishing amount becomes as shown by a solid line K2 in FIG. 9, which is much larger than the case where the pressure control is not performed. It can be seen that the uniformity of the polished surface is improved.

The pressure control system according to the present embodiment uses polishing pressure data corresponding to the relative position between the wafer W and the polishing pad 8 as shown in Table 1 as a set polishing pressure.
Based on this, the Z-axis servomotor 74 is driven to adjust the pressing force F on the polishing pad 8.

Next, an example of the processing in the pressure control device 201 shown in FIG. 8 will be described with reference to the flowcharts shown in FIGS. As shown in FIG. 10, in the pressure control device 201, first, the A / D converter 223 and the D /
The A converter 225 is initialized (step S1).

Next, the A / D converted load cell 81
The filter coefficient of the low-pass filter for removing the high-frequency component of the detection signal is calculated (step S2). The low-pass filter can be constituted by, for example, a secondary FIR filter or the like.

Next, a data file of the contact area between the polishing surface 8a of the polishing pad 8 and the surface to be polished of the wafer W corresponding to the X-axis coordinate position of the wafer W is stored in advance in the external storage device 231 as a file. The data is read (step S3) and stored in the RAM 227 described above. Thus, if the pressure control device 201 sequentially acquires the position of the wafer W in the X-axis direction, the pressure control device 201 can acquire the contact area between the polishing surface 8a of the polishing pad 8 and the surface to be polished of the wafer W at that position. .

Next, a data file of the set polishing pressure value Pr obtained by the above-described simulation, which is stored in the external storage device 231 in advance, is read (step S4). The data file of the set polishing pressure value can be selected from a plurality of recipe files. The pressure control device 201 can acquire the polishing pressure to be set at an arbitrary position in the X-axis direction of the wafer W from the data file of the set polishing pressure Pr.

Next, the D / A converter 225 and the DIO
The outputs of the interfaces 234 and 234 are reset (step S5). Furthermore, the graphic screen of the operation panel 202 is initialized, and the read polishing pressure P
A setting screen including the contents of the data file r is displayed on the screen of the operation panel 202. FIG. 13 is an example of a setting screen displayed on the screen.

Subroutine Next, the process proceeds to a subroutine (step S7). In the subroutine, as shown in FIG. 11, first, interrupt processing is performed at regular intervals (sampling time) (step S11). The processing in the interrupt routine will be described later.

Next, it is confirmed whether or not the end flag for terminating the operation of the pressure control device 201 is turned on (step S12). If the end flag is off, the main control device 301 sends the pressure control device through the DIO 234 to the pressure control device. 201
It is confirmed whether an error reset signal at the time of occurrence of an error, an emergency stop signal, and a pressure control start signal (press servo start signal) for starting pressure control are input. (Step S13). When the reset signal is input, the emergency stop flag and the error reset flag of the pressure control device 201 are turned off. When the emergency stop signal is input, the start flag for starting the pressure control of the pressure control device 201 is turned off, and the emergency stop flag is turned on. When the pressure control start signal is input, the start flag is turned on according to the state of the emergency stop flag and the error reset flag. The operation of the pressure control system according to the present embodiment is started and stopped by an operation signal from main controller 301. The status confirmed in step S13 is displayed as a status such as "stopping" on the setting screen shown in FIG.

If the end flag is ON in step S12, the above-described interrupt processing is stopped (step S16), and the process proceeds to step S8 in FIG.
The outputs of the D / A converter 225 and the DIO 234 are reset.

Next, the state of the start flag is confirmed (step S14). If the start flag is off and the pressure control has not been started yet, the control mode is selected (step S15). The pressure control device 201 according to the present embodiment has a pressure control mode for controlling the polishing pressure P to a desired value and a force control mode for controlling the pressing force F of the polishing pad 8 to be constant. Therefore, one of the two control modes is selected. In this embodiment, only the case where the pressure control mode is selected will be described. The control mode selection result is displayed on the setting screen as shown in FIG. Along with the selection of the control mode, a set value of the polishing pressure P or the pressing force F in the pressure control mode or the force control mode is input. As shown in FIG. 13, the content of the data file of the set polishing pressure is the value of the pressure magnification at each X-axis coordinate position, and the value of the reference polishing pressure is input in this step.

Interrupt Processing Routine During the execution of each step of the above subroutine, the above interrupt processing routine is executed at a predetermined sampling time interval. In the interrupt processing routine, FIG.
As shown in FIG. 2, first, a converted value of the detection signal of the load cell 81 converted into a digital signal by the A / D converter 223 is read (step S22). Next, the read conversion value of the A / D converter 223 is filtered by the low-pass filter configured in step S2 to remove high frequency components such as noise (step S2).
3). The read conversion value of the A / D converter 223 from which the high frequency component has been removed is multiplied by a predetermined coefficient to obtain a load cell 81.
Is converted to the detected force. Further, since the force detected by the load cell 81 when the polishing pad 8 is not in contact with the wafer W is an offset unnecessary for pressure control, this offset is subtracted. The value obtained by subtracting the offset becomes the pressing force F that presses the polishing pad 8 detected by the load cell 81. Therefore, the pressing force F is zero when the polishing pad 8 is not in contact with the wafer W, and when the polishing pad 8 is in contact with the wafer W, the mechanical force of the main shaft 36 in the Z-axis direction is zero. The value corresponds to the amount of deformation.

Next, the X-axis coordinate position of the wafer W is obtained (step S24). The X-axis coordinate position of the wafer W is X
It is obtained from the position detector of the axis table 6. Thereby, the relative position between the polishing pad 8 and the wafer W is detected. Further, data of the contact area A between the polishing surface 8a of the polishing pad 8 and the surface to be polished of the wafer W according to the obtained X-axis coordinate position of the wafer W is obtained. This contact area data is already stored on the RAM 227 as described above. Further, a polishing pressure P is calculated from the obtained area data A and the pressing force F based on the above equation (2).

Next, it is determined whether the pressure control has been started by checking the state of the start flag (step S25). If the pressure control has been started, data of the set polishing pressure Pr corresponding to the acquired X-axis coordinate position of the wafer W is read from the RAM 227 (Step S).
26).

Next, it is determined whether or not the lowering of the main shaft 36 in the Z-axis direction has been completed (step S27). Here, in the pressure control system according to the present embodiment, when the pressure control is started, the main shaft 36 moves in the Z-axis direction in a direction in which the wafer W and the polishing pad 8 come into contact with each other from a separated state. Will be As described above, when the wafer W and the polishing pad 8 are separated from each other, the pressing force F detected by the load cell 81 is zero, and the wafer W and the polishing pad 8 are separated.
When the contact is made, the pressing force F becomes a value corresponding to the amount of mechanical deformation of the main shaft 36 in the Z-axis direction. For this reason, when the pressing force F becomes larger than the predetermined value, it can be determined that the wafer W has come into contact with the polishing pad 8. Therefore, it is determined from the magnitude of the pressing force F calculated in step S24 that the lowering of the main shaft 36 in the Z-axis direction is completed,
If the lowering is completed, the rotation of the Z-axis servo motor 74 is stopped. If the descent in the Z-axis direction is not completed within a predetermined time, the error flag is turned on and the pressure control is stopped.

Next, the polishing pressure P calculated in step S24 is compared with the set polishing pressure Pr read out in step S26 to calculate a pressure difference Pe between the polishing pressure P and the set polishing pressure Pr (step S28). ).

Next, a movement pulse for the Z-axis servomotor 74 is calculated so that the pressure difference Pe becomes zero (step S29). For example, when the pressure difference Pe is already zero, the movement pulse for the Z-axis servo motor 74 is zero, and when the pressure difference Pe is not zero, a movement pulse corresponding to the magnitude is calculated, and D / D The calculated value is written to the A converter 225. Thereby, the D / A converter 22
5, the movement command r is output to the servo driver 74a of the Z-axis servo motor 74. The Z-axis servo motor 74 rotates according to the movement command r, and lowers or raises the sub-slide 82 in the Z-axis direction. Thereby, the load cell 81
The pressing force F that presses the polishing pad 8 that is transmitted through is adjusted to control the polishing pressure P to be equal to the set polishing pressure Pr. As a result, the polishing pressure P generated between the polishing surface 8a of the polishing pad 8 and the surface to be polished of the wafer W during the polishing process is controlled so as to always become the set polishing pressure Pr. When the movement command r is output to the Z-axis servo motor 74, the process returns from the interrupt processing routine to the above-described subroutine (step S30).

As described above, in the pressure control system according to the present embodiment, the polishing surface 8a of the polishing pad 8 during the polishing process.
And the polishing pressure P generated between the surface to be polished of the wafer W and
It is possible to control the polishing pressure to be always at the set polishing pressure Pr. Therefore, similarly to the simulation result shown in FIG. 9, the uniformity of the polishing amount in the surface to be polished of the wafer W can be drastically improved.

Specifically, in the polishing apparatus 30, when the pressing force F of the polishing pad 8 is controlled to be constant and the wafer W having a diameter of 8 inches is polished, the in-plane uniformity of the polished surface of the wafer W is obtained. Although the property M is about 10%, when the polishing is performed while controlling the polishing pressure P by applying the pressure control system according to the present embodiment to the polishing apparatus 30 according to the present embodiment, the polished surface of the wafer W Was able to be improved to about 3%. The in-plane uniformity M is given by the following equation (3).
Required by In-plane uniformity M = standard deviation σ of variation in polishing amount / mean value of polishing amount Me (3)

Further, the polishing apparatus 30 according to the present embodiment
As described above, since the pressing force F against the polishing pad 8 can be accurately detected by the load cell 81,
In the pressure control system according to the present embodiment, the polishing pressure P can be calculated based on the pressing force F of an accurate value, an error with the set polishing pressure Pr can be suppressed, and a more accurate polishing process can be performed. It can be performed.

Further, according to the pressure control system according to the present embodiment, the uniformity of the polished surface of the wafer W is improved while the polishing pressure P is adjusted while the feed speed of the wafer W in the X-axis direction is constant. This eliminates the need to adjust the feed speed of the wafer W in the X-axis direction, thereby facilitating polishing.

Further, by performing the polishing process by applying the pressure control system according to the present embodiment, the uniformity of the polished surface of the wafer W can be improved, so that the yield can be improved and the process can be improved. The margin can be expanded.

[0059]

According to the present invention, since the polishing pressure can be adjusted, the uniformity of the surface to be polished can be improved. Further, according to the present invention, it is possible to accurately detect the pressing force of the polishing pad against the object to be polished, calculate the accurate polishing pressure, and improve the uniformity of the surface to be polished by the polishing pressure. Polishing can be performed with high accuracy. Further, according to the present invention, the wafer W
Since the uniformity of the surface to be polished can be improved, the yield can be improved, and the process margin can be expanded.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a polishing apparatus according to an embodiment of the present invention.

2A and 2B are schematic configuration diagrams of a rotation driving mechanism of a polishing pad and a wafer movement holding mechanism of the polishing apparatus shown in FIG. 1, wherein FIG. 2A is a top view, FIG. 2B is a front view, and FIG. It is a side view.

FIG. 3 is a sectional view of a main part near a polishing pad.

FIG. 4 is a bottom view of the polishing pad.

FIG. 5 is a cross-sectional view showing a state in which polishing is performed in a state where the polishing surface of the polishing pad is in sliding contact with the surface to be polished of the wafer.

FIG. 6 is a configuration diagram showing an example of a pressure control system applied to a rotation drive mechanism of the polishing apparatus according to the present invention.

FIG. 7 is a control block diagram of the pressure control system of FIG. 6;

8 is a configuration diagram illustrating a configuration example of hardware of the pressure control device of FIG. 6;

FIG. 9 is an explanatory diagram showing a simulation result of a polishing process.

FIG. 10 is a flowchart illustrating a processing example of the pressure control device illustrated in FIG. 8;

FIG. 11 is a flowchart illustrating a processing example of the pressure control device illustrated in FIG. 8;

FIG. 12 is a flowchart illustrating a processing example of the pressure control device illustrated in FIG. 8;

FIG. 13 is a diagram illustrating an example of a setting screen displayed on the screen of the operation panel.

[Explanation of symbols]

6 X-axis table, 8 polishing pad, 8a polishing surface, 3
0: Polishing device, 32: Spindle spindle, 72: Z-axis guide, 73: Z-axis slider, 74: Z-axis servo motor, 8
1. Load cell, 82: Sub-slider, 201: Pressure control device.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Ei Otorii 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (12)

[Claims] 1. A polishing means for holding a polishing object, a polishing pad having a polishing surface for polishing the surface to be polished, and a polishing surface of the polishing pad rotatably holding the polishing pad. A rotation driving unit for relatively pressing and rotating the surface to be polished to the surface to be polished, and relatively moving the surface to be polished to the surface to be polished and the polishing surface of the polishing pad in a planar manner while slidingly contacting each other. Moving means, pressing force detecting means for detecting a relative pressing force of the polishing surface of the polishing pad against the surface to be polished by the rotary driving means, and a detection signal of the pressing force detecting means. And a pressure control means for outputting a control signal to the rotary drive means so that a polishing pressure generated on the object to be polished has a desired value. 2. A spindle for rotatably holding the polishing pad so as to face the object to be polished, a spindle for rotating the spindle, a slider for holding the spindle, and A guide for movably holding a slider in the axial direction of the main shaft, a sub-slider movably provided along the axial direction of the main shaft, and a driving unit for moving the sub-slider in the main axis direction. The polishing apparatus according to claim 1, further comprising a connecting member that connects the slider and the sub-slider. 3. The polishing apparatus according to claim 2, wherein the pressing force detecting means detects a force acting on the connecting member from the sub-slider to the slider in an axial direction of the main shaft. 4. The polishing device according to claim 2, wherein the axis of the main shaft, the guide, and the point of action of the connecting member with respect to the slider are located in a plane orthogonal to the surface to be polished. apparatus. 5. The load cell according to claim 3, wherein said pressing force detecting means is a load cell for connecting said slider and said sub-slider and detecting an axial force of said main shaft from said sub-slider to said slider. Polishing equipment. 6. The polishing apparatus according to claim 2, wherein the connecting members are provided at two positions symmetrical with respect to the slider via the axis of the main shaft. 7. The polished surface of the object to be polished based on a detection signal detected by the pressing force detecting unit and a sliding contact area between the object to be polished and the polishing surface of the polishing pad. Is calculated, the polishing pressure is compared with a preset set pressure, and a comparison signal is calculated.Based on the calculation result, a control signal is sent to the rotation driving means so that the polishing pressure becomes the set pressure. The polishing apparatus according to claim 1, which outputs an output. 8. The polishing apparatus according to claim 7, wherein said pressure control means calculates said sliding contact area from a relative position between a polishing surface of said polishing pad and a surface to be polished. 9. The polishing apparatus according to claim 1, wherein the polishing pad is formed in a ring shape about the axis of the main shaft as a center of rotation, and has a polishing surface orthogonal to the axis of the main shaft. 10. A polishing method for polishing a polished surface of an object to be polished by relatively moving a polishing surface of a rotating polishing pad in a planar manner while slidingly contacting the surface to be polished. The pressing force of the polishing pad against the object to be polished is adjusted according to a polishing pressure set in advance according to the relative position between the polishing surface of the polishing pad and the surface to be polished of the object to be polished. A polishing method for polishing a polishing surface. 11. A simulation in which, prior to polishing, a polishing surface of a rotating polishing pad is relatively moved in a plane while sliding a polishing surface of a rotating polishing pad on a polishing surface of the polishing object to polish the polishing surface of the polishing object. Performing a polishing pressure for improving the uniformity of the polished surface of the object to be polished during actual polishing according to a relative position between the polished surface of the polishing pad and the polished surface of the object to be polished. Item 11. The polishing method according to Item 10. 12. The polishing method according to claim 10, wherein a moving speed when the polishing surface of the polishing pad and the surface to be polished are relatively moved is kept constant.