JP2001009712A - Wafer polishing device, and manufacture of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the state of degradation of abrasive pads easily, and detect the state of polishing and completion of polishing of wafers stably. SOLUTION: A wafer holding head 1 comprises a diaphragm 5 tensioned within a head body 2, a carrier 6 secured to the diaphragm 5, a retainer ring 7 concentric with the carrier 6, a pressure regulating mechanism 30 for regulating the pressure of a fluid chamber 14, a carrier torque transmitting mechanism 40 and a ring torque transmitting mechanism 20 for transmitting the torque of the head body 2 to the carrier 6 and retainer ring 7, and a carrier sensor part 41 and a ring sensor part 21 disposed in the torque transmitting mechanisms 40 and 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus and a wafer manufacturing method used in an apparatus for polishing a semiconductor wafer surface in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In recent years, patterns have been miniaturized in accordance with high integration of a semiconductor manufacturing apparatus. In particular, since a fine pattern having a multilayer structure can be easily and reliably formed, a semiconductor wafer during a manufacturing process is required. It has become important to make the surface as flat as possible. In that case, a chemical mechanical polishing method (CMP method), which has a high degree of planarization, has been spotlighted for polishing a surface film.

In the CMP method, the wafer surface is chemically and mechanically polished using an alkaline solution using SiO 2 as an abrasive, a neutral solution using SeO 2, or an acidic solution using Al 2 O 3. In this method, a wafer polishing apparatus used in this method is, for example, as shown in FIG.
There are the following.

FIG. 9 shows a wafer polishing apparatus 100.
Is provided with a wafer holding head 101 holding a wafer W to be polished, and a polishing pad 102 affixed over the entire surface of a platen 103 formed in a disk shape. Of these, a plurality of wafer holding heads 101 are mounted below the carousel 104, which is a head driving mechanism, are rotatably supported by a spindle 111, and are made to rotate planetarily on the polishing pad 102. In this case, the center position of the platen 103 and the revolving center of the wafer holding head 101 can be installed eccentrically.

The platen 103 is disposed horizontally at the center of the base 105, and is rotated around an axis by a platen driving mechanism 106 provided in the base 105. A column 107 is provided on the side of the base 105, and an upper mounting plate 109 for supporting the carousel driving mechanism 110 is arranged between the columns 107. The carousel drive mechanism 110 has a function of rotating the carousel 104 provided below around an axis.

From the base 105, a butt 112 is arranged to protrude upward.
An interval adjusting mechanism 113 is provided at the upper end of the reference numeral 12. On the other hand, above the butting portion 112, the locking portion 11
4 are opposed to each other. The locking portion 114 is configured to be fixed to the upper mounting plate 109 and protrude downward from the upper mounting plate 109. Then, the distance adjusting mechanism 113 is adjusted so that the butting portion 112 and the locking portion 114 are brought into contact with each other, so that the distance between the wafer holding head 101 and the polishing pad 102 is made appropriate. Then, the wafer W held by the wafer holding head 101 is brought into contact with the surface of the polishing pad 102, and the wafer W is polished by rotating the carousel 104 and the platen 103.

When polishing is performed using such a wafer polishing apparatus 100, it is determined whether the polished surface of the wafer W has reached a desired state (polishing end point detection), for example, by determining the rotational power of the platen driving mechanism 106. This was done by observing the fluctuations. That is, when the polishing of the wafer W is insufficient, the frictional force generated between the polishing pad 102 and the wafer W becomes unstable and fluctuates. On the other hand, when the wafer W is polished to a desired polishing surface, Thus, the frictional force becomes stable. At this time, since the platen 103 rotates at a constant speed, for example, when the polishing resistance is large, the rotational power of the platen driving mechanism 106 is large, and when the polishing resistance is small, the rotational power is small. . Then, the fluctuation of the rotational power of the platen driving mechanism 106 is observed, and when this observation value is stabilized, it is determined that the polished surface of the wafer W has reached a desired state.

[0008]

At this time, the wafer W
Polishing deteriorates the polishing pad 102. Although the deteriorated polishing pad 102 is subjected to dressing, it is difficult to determine when dressing is performed during wafer polishing. Therefore, the actual dressing timing is not limited to the length of the polishing time of the wafer W. Predetermined interval (for example, every time one set of wafers W is polished)
Was done in Therefore, even when the polishing pad 102 is not deteriorated, the polishing of the wafer must be temporarily stopped in order to perform the dressing, so that the working efficiency is poor.

Further, as in the prior art, the platen drive mechanism 10
In the method of 6 for observing the fluctuation of the rotational power, it is difficult to accurately detect the polishing end point when detecting the polishing end point of the wafer W made of a material having a small polishing resistance. That is, the platen 103 is often idle even when the wafer W and the polishing pad 102 are not in contact with each other. However, when the wafer W is originally made of a material having a low polishing resistance, the polishing state of the wafer W and the completed state In this case, since the fluctuation of the rotational power of the platen driving mechanism 106 is small, it is difficult to accurately detect the polishing end point of the wafer W by being mixed with the idling power component of the platen 103. Also, the polishing resistance acting on the wafer W may gradually increase with the deterioration of the polishing pad 102. At this time, for example, a state in which one surface (for example, an oxide film layer) of the surface of the wafer W has been removed. When the change in the polishing resistance between the in-polishing state and the completed state is small, such as when the polishing end point is set as the polishing end point, the change in the polishing resistance caused by the deterioration of the polishing pad 102 is lost and the rotation of the platen drive mechanism 106 It has been difficult to accurately detect the polishing end point from fluctuations in power. Further, with respect to the plurality of wafer holding heads 101 installed,
In this case, the polishing end point cannot be detected with respect to the wafer No. 01, and some wafers W are over-polished or under-polished, or over-polished products and under-polished products are mixed.

On the other hand, a method of detecting the rotational power of each wafer holding head 101 can be considered as the polishing end point detection. However, the response is poor, and the force acting on the wafer W cannot be accurately detected. Further, the force detected at this time includes, in addition to the frictional force acting on the wafer W, the frictional force acting on the portion of the wafer holding head 101 other than holding the wafer W and the contact portion with the polishing pad 102. On the other hand, when the polishing pad 102 has deteriorated and the frictional force has changed, the polishing end point cannot be accurately detected.

The present invention has been made in view of such circumstances, and it is possible to easily grasp the state of deterioration of a polishing pad and to stably detect the polishing state of a wafer and the state of completion of polishing. It is an object of the present invention to provide a wafer polishing apparatus and a manufacturing method therefor.

[0012]

In order to solve the above-mentioned problems, a wafer polishing apparatus according to the present invention comprises a platen having a polishing pad adhered to a surface thereof, a wafer to be polished held, and a wafer being polished to the polishing pad. A wafer holding head that abuts one surface thereof, and a wafer polishing apparatus that polishes the wafer with the polishing pad by rotating the wafer holding head and the platen, wherein the wafer holding head is A head body including a plate portion and a cylindrical peripheral wall portion provided below the outer periphery of the top plate portion, a diaphragm stretched in the head body perpendicular to a head axis, the diaphragm and the head body, A pressure adjusting mechanism for adjusting a fluid pressure filled in a fluid chamber formed between the diaphragm and the diaphragm fixed to the diaphragm; A carrier for holding one surface of a wafer to be polished, and a concentric arrangement between an inner wall of the peripheral wall portion and an outer periphery of the carrier, and the diaphragm is provided on the diaphragm. The retainer ring is fixed and provided so as to be displaceable in the head axis direction together with the diaphragm, and a plurality of retainer rings are provided along the circumferential direction between the head body and the retainer ring during polishing. A ring torque transmission mechanism for transmitting torque to the retainer ring, and a plurality of ring sensor units provided on the respective ring torque transmission mechanisms for observing a rotational force acting on the retainer ring; The retainer is connected to each of the ring sensor units and based on the output from these ring sensor units. Characterized in that an arithmetic unit for calculating the force acting on the grayed.

According to the present invention, the sensor portion is provided in the ring torque transmitting mechanism provided on the upper surface of the retainer ring, and the force acting on the retainer ring in contact with the polishing pad can be directly detected. It can be detected stably. Further, since the surface state of the polishing pad can be detected while polishing the wafer, the work efficiency is improved. In addition, even in a configuration including a diaphragm that is an elastic body, the torque of the head body is accurately transmitted to the retainer ring by the ring torque transmission mechanism, and the diaphragm is not subjected to excessive rotational force, so that Deterioration of the diaphragm is prevented.

A plurality of carrier torque transmitting mechanisms are provided between the head body and the carrier along the circumferential direction for transmitting the torque of the head body to the carrier, and the respective carrier torque transmitting mechanisms. And a plurality of carrier sensor units for observing a rotational force acting on the carrier are provided, and the arithmetic unit is connected to the respective carrier sensor units,
By calculating the force acting on the wafer based on the output from the ring sensor and the output from the carrier sensor, the end point of polishing of the wafer can be accurately detected. That is, the change in the polishing resistance due to the deterioration of the polishing pad is detected by the ring sensor unit, and the value of the carrier sensor unit that directly detects the force acting on the wafer based on this value is corrected. The acting force can be accurately detected.

A wafer manufacturing method according to the present invention includes a platen having a polishing pad attached to a surface thereof, and a wafer holding head for holding a wafer to be polished and bringing one surface of the wafer into contact with the polishing pad. A wafer manufacturing method including a polishing step of polishing the wafer with the polishing pad by rotating the wafer holding head and the platen, respectively, wherein the wafer holding head has a top plate portion and a top plate portion. A head body comprising a cylindrical peripheral wall provided below the outer periphery, a diaphragm stretched in the head body perpendicular to the head axis, and a fluid chamber formed between the diaphragm and the head body A pressure adjusting mechanism for adjusting the pressure of the fluid filled in the diaphragm, and a pressure adjusting mechanism fixed to the diaphragm to change the head axial direction together with the diaphragm. A carrier for holding one surface of a wafer to be polished, and a concentrically disposed between an inner wall of the peripheral wall and an outer periphery of the carrier, and fixed to the diaphragm and a head together with the diaphragm. A plurality of retainer rings are provided along the circumferential direction between the head body and the carrier, and are provided so as to be displaceable in the axial direction and abut against the polishing pad during polishing, and transmit the torque of the head body to the carrier. A plurality of carrier torque transmitting mechanisms for providing, in the circumferential direction between the head body and the retainer ring,
A ring torque transmission mechanism for transmitting the torque of the head main body to the retainer ring; and a plurality of carrier sensor units provided in the respective carrier torque transmission mechanisms for observing a rotational force acting on the carrier. And a plurality of ring sensor units provided in each of the ring torque transmitting mechanisms for observing a rotational force acting on the retainer ring, and based on a detection signal of the ring sensor unit, The method is characterized in that the detection signal of the carrier sensor section is corrected, and the polishing is performed while detecting the force acting on the wafer based on the obtained correction value.

According to the present invention, by detecting a force acting on the retainer ring, a change in polishing resistance caused by deterioration of the polishing pad is detected, and a force acting on the wafer held by the carrier is detected. By correcting the force acting on the wafer based on the change in the polishing resistance caused by the deterioration of the polishing pad, it is possible to accurately grasp the polishing state and detect the polishing end point.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wafer polishing apparatus and a wafer manufacturing method according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a wafer holding head 1 in one embodiment of the wafer polishing apparatus of the present invention.
The wafer holding head 1 is installed in, for example, the carousel 104 shown in FIG.

In FIG. 1, a wafer holding head 1 is
A head body 2 including a top plate 3 and a peripheral wall 4 formed in a cylindrical shape; a diaphragm 5 formed of an elastic body stretched inside the head body 2; and a disk-shaped carrier fixed to the lower surface of the diaphragm 5 6, the inner wall of the peripheral wall portion 4 and the carrier 6
And an annular retainer ring 7 provided concentrically on the outer peripheral surface of the ring. The carrier 6 and the retainer ring 7 have a floating structure that can be moved in the axial direction by elastic deformation of the diaphragm 5.

The head body 2 comprises a disk-shaped top plate 3 and a cylindrical peripheral wall 4 fixed below the outer periphery of the top plate 3, and the lower end of the head body 2 is open and hollow. It has become. The top plate 3 is coaxially fixed to a shaft portion 9 which is a connecting portion for connecting to the carousel, and a flow path 15 is formed in the shaft portion 9 in a vertical direction. An external thread 8 is formed on the outer peripheral surface of the shaft 9. In addition, a stepped portion 4a is provided at the lower portion of the
Further, an annular locking portion 10 protruding inward in the radial direction is formed.

The diaphragm 5 made of an elastic material such as fiber reinforced rubber is formed in an annular or disk shape, and is fixed on a step 4a formed on the inner wall of the peripheral wall 4 by a diaphragm fixing ring 11. .

A fluid chamber 14 is formed above the diaphragm 5 and communicates with a flow path 15 formed in the shaft 9. The pressure inside the fluid chamber 14 is adjusted by supplying a fluid such as air into the fluid chamber 14 from the pressure adjusting mechanism 30 through the flow path 15.

The carrier 6 made of a high-rigidity material such as ceramic is formed in a disc-like shape with a certain thickness, and is fixed by a carrier fixing ring 12 provided on the upper surface of the diaphragm 5. An annular step 12a is formed in an upper part of the carrier fixing ring 12, and is formed at a lower end of a nut 19 inserted vertically from the top plate part 3 and a stopper bolt 18 fixed by a spacer 19a. It is adapted to be engaged with the stepped portion 18a. Then, the wafer holding head 1 is moved to the elevating mechanism 118, for example.
And the fluid chamber 14 due to its own weight such as the carrier 6
Even if the diaphragm 5 bends downward due to the internal pressure, the step portion 12a and the step portion 18a engage with each other,
An excessive force is not applied to the diaphragm 5.

The retainer ring 7 is formed in an annular shape between the inner wall of the peripheral wall 4 and the outer peripheral surface of the carrier 6, and slightly between the inner wall of the peripheral wall 4 and the outer peripheral surface of the carrier 6. It is arranged concentrically with the peripheral wall portion 4 and the carrier 6 with an appropriate gap. The retainer ring 7 has an upper end surface and a lower end surface formed horizontally, and is fixed by a retainer ring fixing ring 13 provided on the upper surface of the diaphragm 5. A step 7 is provided on the outer peripheral surface of the retainer ring 7.
When the wafer holding head 1 is lifted by the elevating mechanism 118, even if the diaphragm 5 is locally bent by the weight of the retainer ring 7 and the pressure inside the fluid chamber 14, the stepped portion 7a and the locking portion 10 By engaging with, excessive downward movement of the retainer ring 7 is suppressed, and excessive force is not locally applied to the diaphragm 5.

A plurality of ring torque transmitting mechanisms 20 are provided on the upper surface of the retainer ring 7. As shown in FIGS. 1 and 2, the ring torque transmission mechanism 20 includes a plate-shaped first member 20 a formed so as to extend downward from the lower surface of the top plate 3 along the circumferential direction. A second member 20b having a U-shaped cross section is provided on the upper surface of the retainer ring 7 via the diaphragm 5 so as to correspond to each of the members 20a. The first member 20a and the second member 20b are arranged with their planar portions facing in the circumferential direction, and the tip of the first member 20a is arranged inside the U-shape of the second member 20b.

The tip of the first member 20a and the second member 2
Ob has a space from the inside of the U-shape so as not to hinder the movement of the retainer ring 7 in the axial direction.
That is, the second member 20b is provided so as to be movable in the axial direction with respect to the first member 20a together with the retainer ring 7.

The ring torque transmitting mechanism 20 is for transmitting the torque of the head main body 2 to the retainer ring 7 when the head main body 2 is rotated during the polishing of the wafer W. That is, when the head main body 2 is rotated in the direction of arrow A in FIG.
The retainer ring 7 supported by the diaphragm 5 is rotated in the direction of arrow A while being twisted in the direction of arrow B by the frictional force between its own lower surface and the polishing pad 102. At this time, the one side of the first member 20a and the inside of the U-shape of the second member 20b are in contact with each other, so that the torque of the head main body 2 is reduced to the retainer ring 7 while the torsional force acting on the diaphragm 5 is reduced. Let them communicate. At this time, the first member 20a and the second member 20b are slidable with each other in the axial direction, so that the floating effect of the retainer ring 7 is not hindered.

A ring sensor 21 is provided on a part of the side surface of the first member 20a. This ring sensor section 21
Are provided in parallel with the planar portion of the second member 20b oriented in the rotation direction, and are provided on the side pressed into the second member 20b when the wafer holding head 1 rotates.

That is, when the wafer holding head 1 is not rotated, the ring torque transmitting mechanism 20
The surface of the ring sensor 21 and the inside of the second member 20b are slightly separated from each other so as not to hinder the swing of the retainer ring 7 in the axial direction. When the wafer holding head 1 is rotated, the ring sensor unit 21 is provided on one side of the first member 20a on which the ring sensor unit 21 is installed and on the side where the surface inside the second member 20b is pressed. Let me.

The ring sensor 21 uses a pressure sensor such as a piezoelectric element or a strain gauge.
First member 2 generated by rotation of wafer holding head 1
0a and the pressing force between the second member 20b can be detected. That is, when the wafer W is polished, the rotational force acting on the lower surface of the retainer ring 7 due to friction with the polishing pad 102 is directly detected by the ring sensor 21.

On the other hand, a plurality of carrier torque transmitting mechanisms 40 for transmitting the torque of the head main body 2 to the carrier 6 when the head main body 2 is rotated during the polishing of the wafer W are provided on the upper surface of the carrier 6. The carrier torque transmission mechanism 40 has the same configuration as the ring torque transmission mechanism 20, and has a plate-shaped first member 40a formed to extend downward from the lower surface of the top plate 3 along the circumferential direction.
And a second member 40b having a U-shaped cross section provided on the upper surface of the carrier 6 so as to correspond to the first member 40a, respectively.
And The first member 40a is provided in parallel with the plane portion of the second member 40b oriented in the rotation direction. When the wafer holding head 1 rotates, a part of the side surface of the first member 40a rotates. A carrier sensor section 41 is provided on the side pressed inside the two members 40b.

The distal end of the first member 40a and the U-shaped interior of the second member 40b are arranged with a space therebetween,
The movement of the carrier 6 in the axial direction is not hindered. Further, the carrier sensor section 41 is provided on the side where one side surface of the first member 40a and the inner surface of the second member 40b are pressed when the wafer holding head 1 is rotated.

A pressure sensor such as a piezoelectric element or a strain gauge is used for the carrier sensor 41, like the ring sensor 21, and the first member 40a and the second member 40a generated by the rotation of the wafer holding head 1 are used. The pressing force with respect to 40b can be detected. That is, when the wafer W is polished, the rotational force acting on the wafer W is directly detected by the carrier sensor 41 via the carrier 6.

When the wafer holding head 1 is not rotated, the surface of the ring sensor 21 and the second
The inside of the member 20b may be in a state where the retainer ring 7 is slightly contacted so as not to hinder the swing of the retainer ring 7 in the axial direction. Further, the ring sensor section 21 may be provided at a portion pressed when the wafer holding head 1 is rotated, and may be provided at, for example, a plane portion on the second member 20b side. Further, the first member 20a may be formed in a U-shaped cross section and the second member 20b may be formed in a plate shape, or the first and second members 20a and 20b may be formed in plate shapes, respectively. . The same applies to the carrier torque transmission mechanism 40 and the carrier sensor unit 41.

As shown in FIG. 3, the ring torque transmitting mechanism 20 provided with the ring sensor section 21 is provided at a plurality of circumferential positions on the upper surface of the retainer ring 7 of the wafer holding head 1 and rotates. Four locations are provided at the same distance from the axis center in the radial direction. Similarly,
The carrier torque transmitting mechanism 40 including the carrier sensor unit 41 is also provided at a plurality of locations on the upper surface of the carrier 6 in the circumferential direction, and is provided at, for example, four locations at the same radial distance from the center of the rotation axis. .

Each of the ring sensor sections 21 is provided with a harness 3 inserted through the shaft section 9 connected to the spindle.
1a is connected to the arithmetic unit 31. The output signals from each of the ring sensor units 21 are sent to the operation unit 31 by a harness 31a connected to the operation unit 31. The operation unit 31 receives the output signal from each of the ring sensor units 21 and And polishing pad 1
02 is output. Similarly, the output signal from the carrier sensor unit 41 is also sent to the calculation unit 31 by the harness 31b, and the calculation unit 31
Receives an output signal from each carrier sensor unit 41 and outputs a force acting on the wafer W.

The wafer holding head 1 configured as described above is connected by screwing the external thread 8 to the carousel. When polishing the wafer W using the wafer holding head 1, first, the wafer W
Is attached to the wafer attachment sheet 6a provided on the lower surface of the wafer. Then, while the periphery of the wafer W is locked by the retainer ring 7, the surface thereof is brought into contact with the polishing pad 102 attached to the upper surface of the platen 103. The material of the polishing pad 102 may be any material that has been conventionally used for polishing a wafer. For example, a velor-type pad in which a nonwoven fabric made of polyester or the like is impregnated with a soft resin such as a polyurethane resin, or a polyester A suede-type pad having a foamed resin layer made of foamed polyurethane or the like formed on a nonwoven fabric made of nonwoven fabric or the like, or a foamed resin sheet made of independently foamed polyurethane or the like is used.

Next, a fluid such as air is supplied from the pressure adjusting mechanism 30 to the flow path 15. The supplied fluid is in the fluid chamber 1
4 The flowed fluid adjusts the pressure in the fluid chamber 14 and adjusts the pressing pressure of the carrier 6 and the retainer ring 7 against the polishing pad 102. The carrier 6 and the retainer ring 7 have a floating structure supported by the diaphragm 5 and capable of being independently displaced in the vertical direction, and the pressure applied to the polishing pad 102 can be adjusted by the pressure inside the fluid chamber 14. ing.

Then, the carrier 6 and the retainer ring 7
Platen 1 while adjusting the pressing force on polishing pad 102
The wafer W is polished by rotating the wafer holding head 1 in a planetary rotation while rotating the wafer holder 03 and simultaneously supplying the polishing agent from the polishing agent supply means (not shown) to the surface of the polishing pad 102 and the polishing surface of the wafer W. .

The carrier 6 and the retainer ring 7 holding the wafer W are twisted with respect to the head body 2 by the force acting between the polishing pad 102 and the lower surface of the wafer W and the retainer ring 7 to be polished. At this time, the ring torque transmission mechanism 20 and the carrier torque transmission mechanism 4
The ring sensor unit 21 and the carrier sensor unit 41 provided at 0 are pressed by the flat portions inside the second members 20b and 40b and output a signal corresponding to the pressing force.
That is, the ring sensor unit 21 outputs an output signal corresponding to the force acting between the lower surface of the retainer ring 7 and the polishing pad 102, and the carrier sensor unit 41 responds to the force acting between the wafer W and the polishing pad 102. The output signals are sent to the operation unit 31 independently. Then, the calculation unit 31 independently calculates a force acting on the retainer ring 7 and the wafer W based on output signals from the plurality of ring sensor units 21 and the carrier sensor unit 41.

For example, as shown in FIG. 4, the retainer ring 7 has a rotational force T generated in the rotation direction of the wafer holding head 1 by rotating on the polishing pad 102 and a rotational force T of the polishing pad 102 due to the rotation of the polishing pad 102. The polishing force F generated in the rotation direction is applied. And operation unit 3
Numeral 1 calculates the rotational force T and the polishing force F.

This rotational force T is generated by the rotation of the wafer holding head 1 and acts in the rotational direction of the retainer ring 7, and differs between the inner diameter position and the outer diameter position. On the other hand, the polishing force F is generated by the rotation of the polishing pad 102, and acts uniformly on the entire lower surface of the retainer ring 7 in the rotation direction of the polishing pad 102.

This polishing force F acts on the entire contact surface between the retainer ring 7 and the polishing pad 102, and is, for example, a resultant force acting on the center position of the retainer ring 7 as shown in FIG. Can be. At this time, at the position a where the tangential direction of the rotating retainer ring 7 and the rotational direction of the polishing pad 102 coincide with each other in the outer peripheral portion of the retainer ring 7, the force acting on the retainer ring 7 by the rotation of the polishing pad 102 is F / 2. Further, a rotational force T is applied in the rotation direction of the retainer ring 7. Since the four ring sensor portions 21 provided along the circumferential direction of the retainer ring 7 are installed with their sensitivity directions directed toward the rotation direction of the wafer holding head 1, they are moved to the position a. The force Fa acting on the ring sensor section 21 is as follows: Fa = F / 2 + T (1) Similarly, the force Fb acting on the ring sensor unit 21 moved to the position b on the inner peripheral side of the polishing pad 102 is: Fb = F / 2−T (2) Therefore, from the equations (1) and (2), Fa + Fb = F (3), and the polishing force F can be obtained.

Further, the ring sensor unit 21 moved to the position c in the rotational direction of the polishing pad 102 and at a right angle to the positions a and b changes its sensitivity direction to the rotational direction of the wafer holding head 1. Since it is installed facing, only the rotational force T generated by the rotation of the wafer holding head 1 is detected. That is, since the sensitivity direction of the ring sensor unit 21 and the rotational direction of the polishing pad 102 are in a vertical relationship at the position c, the ring sensor unit 21 generates the polishing force F generated by the relative movement between the wafer holding head 1 and the polishing pad 102. Not detected. Therefore, the force Fc acting on the ring sensor unit 21 moved to the position c
Is Fc = T (4) Similarly, the ring sensor unit 2 moved to the position d
The force Fd acting on 1 is: Fd = T (5) Therefore, equation (3), equation (4) (or (5)
The rotational force T and the polishing force F acting on the retainer ring 7 can be derived from the equation). The number of rotations of the carousel per unit time: Rc The number of rotations of the wafer holding head 1 per unit time: Rh When the number of rotations per unit time of the platen 103 is Rp, Rc + Rh = Rp (6) No torque acts on the carrier 6.

In one rotation of the wafer holding head 1, one ring sensor unit 21 applies the maximum force Fa.
, And outputs a sinusoidally fluctuating signal having the minimum value of the force Fb and the forces Fc and Fd observed at the intermediate time. At this time, since the rotation time (rotation speed) of the wafer holding head 1 is known in advance, the rotation force T and the polishing force F of the wafer W can be detected by one ring sensor unit 21. Therefore, the polishing force F and the rotational force T can be obtained by detecting a signal output from one ring sensor unit 21 every moment.

Further, by providing two ring sensor units 21 at positions a and b, respectively, the arithmetic unit 31 that receives these output signals at the same time enables the polishing force acting on the wafer W while polishing the wafer W. F is detected. That is, the polishing force F can be calculated by providing the two ring sensor units 21 according to the equations (1), (2), and (3). Therefore, at least two ring sensor units 21 are installed on the upper surface of the retainer ring 7, and these ring sensor units 21, 21 are installed so as to be opposed to a position at the same radial distance from the rotation center of the retainer ring 7. As a result, the polishing force F or the rotational force T becomes
The detection can be performed while polishing the wafer W.

Further, positions a and b and positions a and b
By arranging the ring sensor portions 21, 21, 21 at a position c which is in a right angle relationship with respect to
The polishing force F can be derived from the expressions (2) and (3), and the rotational force T can be derived simultaneously from the expression (4) (or the expression (5)). As described above, three ring sensor portions 21 are provided on the upper surface of the retainer ring 7, and two of the ring sensor portions 21 are arranged so as to face radially equal distances from the rotation center of the retainer ring 7. Is arranged at a position perpendicular to the two ring sensors 21, the polishing force F and the rotational force T can be simultaneously detected while polishing the wafer W.

Further, at least four ring sensor portions 21 are provided on the upper surface of the retainer ring 7, and two of the ring sensor portions 21 are arranged so as to be opposed to a position at an equal radial distance from the rotation center of the retainer ring 7. Are disposed at right angles to the two ring sensor portions 21, so that the polishing force F acting on the retainer ring 7 is
And the rotational force T can always be detected simultaneously while polishing the wafer W.

As described above, by providing a plurality, preferably four or more, of the ring sensor portions 21, the polishing force F and the rotational force T can be simultaneously detected. Further, as shown in the equation (3), the polishing force F is derived based on the respective outputs from the two ring sensor units 21 arranged opposite to each other. Therefore, at least two ring sensor units 2
The polishing force F is detected by arranging the ring sensors 1 and 21 at the same distance in the radial direction with respect to the rotation center of the retainer ring 7, that is, by providing the ring sensor unit 21 at even positions as a whole.

As described above, the arithmetic unit 31 calculates the force acting on the wafer W held on the lower surface of the carrier 6 based on the output signal from the carrier sensor unit 41 provided on the upper surface of the carrier 6. As described above, the calculation unit 31 simultaneously and independently calculates the force acting on the lower surface of the retainer ring 7 and the force acting on the wafer W.

A case where the wafer W1 provided with an oxide film as shown in FIG. 5 is flattened by using such a wafer holding head 1 will be described. This wafer W1
Is to be polished so as to flatten an oxide film having an uneven surface, and passes through time h1 to time h
Aim to be polished to 2. That is, the polishing end point in this case is a state where the oxide film of the wafer W1 is flattened. When the wafer W1 is polished, the calculation unit 31 outputs the detection value g1 based on the output of the ring sensor unit 21 provided in the ring torque transmission mechanism 20 and the output of the carrier sensor unit 41 provided in the carrier torque transmission mechanism 40. And a detection value g2 based on

At this time, when polishing is performed in a state where the polishing pad 102 has not deteriorated, when the polishing is started at a time point h1.
Until the contact area between the wafer W1 and the polishing pad 102 gradually increases, the polishing resistance of the wafer W1 also gradually increases, and between the time h1 and the time h2, Since the contact area is constant, the polishing resistance also shows a constant value.

However, when the wafer W1 is polished in a state where the polishing pad 102 is deteriorated, as shown in FIG. 6A, the detection value g2 based on the output value of the carrier sensor unit 41 is changed from the time h1 to the time It gradually rises at h2. At this time, the detection value g1 based on the output value of the ring sensor unit 21 also gradually increases. This indicates that the polishing pad 102 gradually deteriorates as the polishing of the wafer W progresses, so that the polishing resistance acting between the lower surface of the retainer ring 7 and the polishing pad 102 gradually increases. Therefore, the detected value g2, which is the polishing resistance of the wafer W1, also increases between the time h1 and the time h2. For this reason, it is difficult to determine the polishing end point.

The detected values g1 and g2 indicate the change in the maximum value of the signals output from the respective sensor units 21 and 41.

At this time, the polishing resistance of the wafer W is observed based on the change in the surface state of the polishing pad 102, that is, the value of the change in the polishing resistance of the retainer ring 7 rotated while directly contacting the polishing pad 102. By correcting the detection value of the carrier sensor unit 41, the wafer W1
Is polished. That is, the polishing pad 102
Of the polishing resistance (that is, the detected value g
1) is subtracted from the polishing resistance value of the wafer W including the change (that is, the detected value g2), and as shown in FIG. 6B, the calculation between the time h1 and the time h2 is performed. The value now shows a stable constant value,
The detection of the polishing end point can be accurately grasped.

When the polished surface of the wafer W is flattened and a desired polished surface is obtained (that is, when the polished surface reaches the time point h2), it is determined that the polished surface of the wafer W has reached a desired state, and The polishing is completed.

As described above, the ring sensor portion 2 is attached to the ring torque transmitting mechanism 20 provided on the upper surface of the retainer ring 7.
1 and retainer ring 7 contacting polishing pad 102
By detecting the force acting on the polishing pad 102, it is possible to detect the deterioration state of the polishing pad 102 while polishing the wafer. Since the detection of the deteriorated state can be performed simultaneously with the polishing of the wafer, the working efficiency is improved. Then, the torque of the head body 2 is accurately transmitted to the retainer ring 7 by the ring torque transmission mechanism 20, and the diaphragm 5 is not subjected to excessive rotational force. Therefore, the deterioration of the diaphragm 5 is prevented. You.

Further, by providing the carrier torque transmitting mechanism 40 on the upper surface of the carrier 6, the torque of the head main body 2 is accurately transmitted to the carrier 6, and no excessive rotational force is applied to the diaphragm 5. Become like Therefore, the deterioration of the diaphragm 5 can be prevented, and a stable floating effect can be maintained for a long time.

Since the ring sensor section 21 and the carrier sensor section 41 are provided in the ring torque transmission mechanism 20 and the carrier torque transmission mechanism 40, respectively, the force acting on the lower surface of the retainer ring 7 and the wafer W is directly applied to each sensor section 21. , 41. That is, by directly detecting the force acting on the lower surface of the retainer ring 7 and the wafer W, the force acting on the carrier 6 holding the retainer ring 7 and the wafer W can be directly and accurately detected.

Then, the output signals of the sensor sections 21 and 41 are sent to the arithmetic section 31 and operated to calculate the value of the polishing resistance of the wafer W by subtracting the change caused by the deterioration of the polishing pad 102. Therefore, the polishing end point is detected with high accuracy.

The outputs from the ring sensor section 21 and the carrier sensor section 41 are calculated by a calculation section 31.
The calculation unit 31 outputs a force acting on the retainer ring 7 and the wafer W during polishing of the wafer W. Therefore, since the polishing of the wafer W is performed while observing the force acting on the wafer W, the polishing is performed while determining whether the polished surface of the wafer W has reached a desired state.
Therefore, generation of a wafer such as overpolishing or insufficient polishing can be reduced, and stable polishing of the wafer W can be realized.

The sensor section 21 (41) is connected to the first member 2
The force acting on the wafer W is reliably detected even when the wafer holding head 1 is in a rotating state, because it is provided at a contact portion between the first member 0a (40a) and the second member 20b (40b). Further, the second member 20b (40b) is
a (20a), the carrier 6 and the retainer ring 7 supported by the diaphragm 5 are not displaced in the axial direction, and the polishing of the wafer W is stably performed. Done.

The plurality of sensor units 21 (4
1) are provided at the same radial distance from the center of rotation of the wafer holding head 1, respectively. May be arranged such that their distances from the rotation center of the sensor unit are different from each other. In this case, each sensor unit can detect the rotational force T at a predetermined distance. That is, by providing a plurality of pairs of sensor units facing each other, it is possible to detect the rotational force of the wafer W at various positions in the radial direction.

As shown in FIG. 7A, one or both of the contact portions of the first and second members 20a and 20b may be formed in a round bar shape. By forming the first and second members 20a and 20b in a round bar shape, the contact area of each can be reduced, so that the vertical swinging (floating effect) of the retainer ring 7 is performed more stably. Further, FIG.
As shown in the figure, the ring sensor 21 is disposed between the top plate 3 and the first member 20a (or between the retainer ring 7 and the second member 20b), and the wafer is subjected to a shear force generated at this position. It is also possible to detect a rotational force acting on W. In this case, the shear force can be detected by using a piezoelectric element as the ring sensor unit 21. Further, by employing a configuration in which a shear force is detected using a piezoelectric element, forces acting in a plurality of directions can be simultaneously detected by one ring sensor section 21, and the number of ring sensor sections 21 to be installed is reduced. can do. Of course, the configuration of FIG.
Needless to say, it can be applied to 0.

As shown in FIG. 8, the ring sensor section 21 is driven by a driving circuit of a driving / amplifying circuit unit 32 installed on the upper surface of the head main body 2 and outputs an output signal from the ring sensor section 21. Of the drive / amplifier circuit unit 32 may be sent to the arithmetic unit 31 via the amplifier circuit. At this time, the ring sensor unit 2
A harness 32 a connecting the drive unit 1 to the drive / amplification circuit unit 32 is provided so as to pass through a part of the top plate 3 of the head main body 2. Similarly, the carrier torque transmission mechanism 4
0 is provided with the harness 32.
It is connected to the drive / amplifier circuit unit 32 by b. Since the driving / amplifying unit 32 is installed in the head main body 2, the harnesses 32a and 32b can be formed short, so that the sensor unit 21 is hardly affected by noise.

[0065]

The wafer polishing apparatus and the wafer manufacturing method of the present invention have the following effects. (1) A sensor portion is provided on a ring torque transmission mechanism provided on the upper surface of the retainer ring, and the force acting on the retainer ring in contact with the polishing pad can be directly detected, so that the deterioration of the polishing pad can be detected stably. Can be. Further, since the surface state of the polishing pad can be detected while polishing the wafer, the work efficiency is improved. In addition, even in a configuration including a diaphragm that is an elastic body, the torque of the head body is accurately transmitted to the retainer ring by the ring torque transmission mechanism, and the diaphragm is not subjected to excessive rotational force, so that Deterioration of the diaphragm is prevented. (2) A plurality of carrier sensor units for observing the rotational force acting on the carrier are provided, and the calculation units are connected to the respective carrier sensor units, so that the output from the ring sensor unit and the output from the carrier sensor unit are provided. By calculating the force acting on the wafer based on the above, the polishing end point of the wafer can be detected more accurately. That is, the change in the polishing resistance of the polishing pad deteriorated by polishing is detected by the ring sensor unit, and the value of the carrier sensor unit which directly detects the force acting on the wafer based on this value is corrected. Can be detected more accurately.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wafer holding head in a view showing an example of an embodiment of a wafer polishing apparatus of the present invention.

FIG. 2 is a sectional view illustrating a torque transmission mechanism and a sensor unit.

FIG. 3 is a diagram illustrating an arrangement of a torque transmission mechanism and a sensor unit.

FIG. 4 is a diagram illustrating a state where a force acting on a wafer is detected by a sensor unit.

FIG. 5 is a sectional view showing a layer configuration of a wafer.

FIG. 6 is a diagram illustrating an output result from a calculation unit when the wafer in FIG. 5 is polished.

FIG. 7 is a sectional view showing another embodiment of the torque transmission mechanism and the sensor unit.

FIG. 8 is a cross-sectional view of a wafer holding head in a view showing an example of an embodiment of a wafer polishing apparatus of the present invention.

FIG. 9 is a diagram illustrating the entire wafer polishing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wafer holding head 2 Head main body 3 Top plate part 4 Peripheral wall part 5 Diaphragm 6 Carrier 7 Retainer ring 9 Shaft part 14 Fluid chamber 15 Flow path 20 Ring torque transmission mechanism 21 Ring sensor part 30 Pressure adjustment mechanism 31 Calculation part 40 Carrier torque transmission Mechanism 41 Carrier sensor unit 102 Polishing pad 103 Platen W wafer

Claims (3)

[Claims] A platen having a polishing pad affixed to a surface thereof; and a wafer holding head for holding a wafer to be polished and bringing one surface of the wafer into contact with the polishing pad. A wafer polishing apparatus for polishing the wafer with the polishing pad by rotating the wafer pad, wherein the wafer holding head comprises a top plate portion and a cylindrical peripheral wall portion provided below the outer periphery of the top plate portion. A head body comprising: a diaphragm extending perpendicularly to a head axis in the head body; and a pressure adjusting mechanism for adjusting a fluid pressure filled in a fluid chamber formed between the diaphragm and the head body. And fixed to the diaphragm and provided so as to be displaceable in the head axis direction together with the diaphragm, and one surface of the wafer to be polished is And a carrier for holding, concentrically disposed between the inner wall of the peripheral wall portion and the outer periphery of the carrier, fixed to the diaphragm and provided so as to be displaceable in the head axis direction together with the diaphragm, and polished during polishing. A retainer ring abutting on a pad; a plurality of ring torque transmission mechanisms provided circumferentially between the head body and the retainer ring to transmit torque of the head body to the retainer ring; A plurality of ring sensor units provided in the ring torque transmission mechanism for observing a rotational force acting on the retainer ring, and are connected to the respective ring sensor units, based on outputs from these ring sensor units. A calculation unit for calculating a force acting on the retainer ring. Polishing apparatus. 2. The wafer polishing apparatus according to claim 1, wherein a plurality of wafer polishing apparatuses are provided between the head main body and the carrier along a circumferential direction, and transmit the torque of the head main body to the carrier. A carrier torque transmitting mechanism; and a plurality of carrier sensor units provided in each of the carrier torque transmitting mechanisms for observing a rotational force acting on the carrier. A wafer polishing apparatus which is connected to a section and calculates a force acting on the wafer based on an output from the ring sensor section and an output from the carrier sensor section. 3. A platen having a polishing pad attached to a surface thereof, and a wafer holding head for holding a wafer to be polished and bringing one surface of the wafer into contact with the polishing pad, wherein the wafer holding head and the platen A polishing step of polishing the wafer with the polishing pad by rotating each of the wafers, wherein the wafer holding head is provided below the top plate and the outer periphery of the top plate. A head body composed of a cylindrical peripheral wall portion; a diaphragm stretched in the head body perpendicular to the head axis; and a fluid pressure filled in a fluid chamber formed between the diaphragm and the head body. A pressure adjusting mechanism for adjusting the pressure, and being provided on the diaphragm so as to be displaceable in the head axis direction together with the diaphragm, and for polishing. A carrier for holding one surface of the wafer, and disposed concentrically between the inner wall of the peripheral wall portion and the outer periphery of the carrier, and fixed to the diaphragm and provided so as to be displaceable in the head axis direction together with the diaphragm. A plurality of retainer rings that abut against a polishing pad during polishing, a plurality of retainer rings are provided along the circumferential direction between the head body and the carrier, and a carrier torque transmission mechanism for transmitting torque of the head body to the carrier. A plurality of ring torque transmitting mechanisms provided in the circumferential direction between the head body and the retainer ring to transmit torque of the head body to the retainer ring; and a ring torque transmitting mechanism provided in each of the carrier torque transmitting mechanisms. And a plurality of carrier sensor units for observing a rotational force acting on the carrier. A plurality of ring sensor units provided in each of the ring torque transmission mechanisms for observing a rotational force acting on the retainer ring; and a carrier sensor based on a detection signal of the ring sensor unit. A method of correcting a detection signal of a portion, and performing polishing while detecting a force acting on the wafer based on the obtained correction value.