JP2000006002A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of satisfactorily controlling the evenness in the polishing surface of an article to be polished. SOLUTION: In a polishing device provided with a turntable stuck with a polishing cloth or a grinding wheel on the surface and a top ring 16 for holding the article 15 to be polished, and pressing the article 15 to be polished held by the rotating top ring 16 on the polishing cloth or the grinding wheel surface of the turntable for polishing the polishing surface of the article 15 to be polished, a piezoelectric element 32 is provided to the top ring 16, or a piezoelectric element 32 is provided between a rotary shaft 17 for holding the top ring 16 and the top ring 16. The pressure distribution in the surface of the article 15 to be polished held by the top ring 16, or its inclination is regulated by regulating the voltage applied to the piezoelectric element 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus for polishing a surface of an object to be polished such as a semiconductor wafer to a flat and mirror surface, and more particularly to a mechanism for adjusting the in-plane pressure distribution of a top ring for holding the object to be polished. About.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has increased, circuit wiring has become finer and the distance between wirings has been reduced. In particular, in the case of optical lithography of 0.5 μm or less, the depth of focus becomes shallow, so that the image forming surface of the stepper needs to be flat. Therefore, it is necessary to planarize the surface of the semiconductor wafer. As one of the planarization methods, polishing is performed by a polishing apparatus. Conventionally, this type of polishing apparatus rotates a top ring and a turntable on which an abrasive cloth or a grindstone is stuck on the upper surface at an independent rotation speed, and interposes an object to be polished between the abrasive cloth or the grindstone and the top ring. Then, the surface of the object to be polished is polished to a flat and mirror-like surface while the polishing liquid flows down onto the polishing cloth or the grindstone.

FIG. 7 shows an example of a conventional polishing apparatus. A turntable 12 having a surface to which a polishing cloth or a grinding stone 11 is attached is fixed to a rotating shaft 13 and is driven to rotate by a motor (not shown). The rotating shaft 13 is supported in a radial direction and a thrust direction by a radial bearing 14A and a thrust bearing 14B, respectively. For example, a top ring 16 for holding a workpiece 15 such as a semiconductor wafer
Is rotatably driven by a motor 18 via a pulley 19 and a belt 20.
The rotating shaft 17 holding the top ring is supported on its upper and lower sides by radial bearings 21, and the radial bearings 21 are fixed to a housing 22 via an elastic body 23 such as rubber.

Here, while applying a constant pressure to the object to be polished during polishing, the top ring and the turntable are rotated,
The polished surface of the object to be polished is uniformly polished.
Since the polished surface of No. 5 has irregularities, the pressure applied by the rotating shaft 17 of the top ring is not always uniformly loaded on the surface of the object to be polished with a constant load over the entire surface, and the uniformity of the polished surface is impaired. There's a problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polishing apparatus capable of well controlling the uniformity of a polished object in a polished surface. And

[0006]

A polishing apparatus according to the present invention includes a turntable having a polishing cloth or a grindstone adhered to a surface thereof, and a top ring for holding an object to be polished. In a polishing apparatus for pressing an object to be polished held by the rotating top ring against a whetstone surface and polishing a polished surface of the object to be polished, a piezoelectric element is provided on the top ring, or the top ring is supported. A piezoelectric element is provided between the rotating shaft to be rotated and the top ring, and the applied voltage of the piezoelectric element is adjusted to adjust the in-plane pressure distribution or inclination of the object to be polished held by the top ring. It is characterized by.

In the polishing apparatus, a piezoelectric element is provided on the top ring, or a piezoelectric element is provided between a rotating shaft supporting the top ring and the top ring. The in-plane pressure distribution of the object to be polished, which is held by the top ring, is detected.

Further, the top ring includes a sensor for measuring an in-plane pressure or displacement of the object to be polished, and the piezoelectric element is controlled based on an output of the sensor.

According to the above invention, since the piezoelectric element generates displacement in accordance with the applied voltage and generates voltage in accordance with the pressure, the rotation shaft in the top ring or the top ring supporting the top ring and the top ring The pressure applied to the turntable of the object to be polished is adjusted by the piezoelectric element
Can be detected. Thereby, at the time of polishing, the in-plane pressure distribution of the object to be polished can be adjusted, and the uniformity of the in-plane polishing amount can be improved. Furthermore, a sensor is provided,
Since the in-plane pressure distribution can be controlled based on the information of the sensor, polishing is performed while controlling the in-plane pressure distribution and the like to a predetermined target value while always detecting the in-plane pressure distribution and the like during polishing. It can be carried out.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of a top ring according to a first embodiment of the present invention. The top ring 16 is supported by a rotating shaft 17 and holds, for example, a semiconductor wafer 15 which is an object to be polished on a lower end surface thereof. Top ring 16
Is provided with a convex portion 16a at its lower end, and a guide ring 31 for holding the wafer 15 is mounted on the convex portion 16a so as to be movable in the vertical direction. Lower end surface 16 of top ring 16
As shown in FIG. 1B, a piezoelectric element 32 is mounted on the entire surface of the piezoelectric element 32b.

The piezoelectric element 32 is a group of electrically independent piezoelectric elements divided radially and circumferentially as shown in the drawing, and each is formed in a fan shape. A voltage input line (not shown) is connected to each element of the unit piezoelectric element, so that a different voltage can be applied to each unit piezoelectric element. An elastic mat 33 is attached below the piezoelectric element 32, and the object 15 to be polished comes into contact with the elastic mat 33 so as to provide a cushioning property during polishing.

According to the top ring having such a configuration, by supplying different voltages to the respective piezoelectric elements 32, a slight displacement can be given in the vertical direction, that is, in the contact direction of the object to be polished. Thereby, the in-plane pressure distribution of the top ring 16 applied to the workpiece can be arbitrarily adjusted.
For example, when the outer peripheral side of the object 15 is excessively polished and the inner peripheral side is excessively polished, a small displacement of (−) is applied to the outer peripheral side piezoelectric element, and (+) is applied to the inner peripheral side piezoelectric element. )
The applied voltage may be adjusted so as to give a slight displacement on the side. As a result, excessive polishing on the outer peripheral side and excessive polishing on the inner peripheral side are corrected, and a uniform polished surface can be obtained. Further, even when the surface of the object 15 is inclined, the object to be polished can be polished by giving each piezoelectric element a slight difference in displacement in order to correct the inclination.

In the above embodiment, an example in which the piezoelectric element is attached to the entire lower end of the top ring has been described. However, it is not always necessary to provide the piezoelectric element on the entire surface. The portion may be provided with a vacuum suction hole for adsorbing the object to be polished to the top ring or a fluid injection hole for applying a back pressure to the object to be polished during polishing.

FIG. 2 shows a configuration of a top ring according to a second embodiment of the present invention. This top ring portion has piezoelectric elements 32A and 32B arranged in two layers as shown. The upper piezoelectric element 32A functions as a pressure sensor. That is, a lead wire (not shown) is connected to each of the piezoelectric elements 32A, and a vertical in-plane pressure distribution causes
A voltage corresponding to this is output. Lower layer piezoelectric element 3
2B has the same function as the piezoelectric element 32 of the first embodiment. That is, a lead wire (not shown) is connected to each of the piezoelectric elements 32B, which is connected to a controller. When an applied voltage is supplied, a slight displacement occurs with respect to the contact surface of the object to be polished.

FIG. 3 is a block diagram of a control system according to this embodiment. A command value of the in-plane pressure distribution is given to each lower end surface of the top ring, and this command value is compared with the actually detected output of the pressure sensor 32A. Then, the comparison deviation ΔV is input to the controller 34, and PID (proportional / integral / differential) is set so that the deviation ΔV becomes zero.
A control output is generated by a control device such as the above. The drive circuit 35 amplifies the output of the controller 34 and inputs the amplified output to the lead terminal of the piezoelectric element 32B. As a result, a minute displacement in the vertical direction occurs in the piezoelectric element 32B, which gives a minute unevenness to the contact surface of the object to be polished and adjusts the in-plane pressure distribution of the polished surface of the top ring. This process is indicated as a plant 37.

According to the top ring having such a configuration, the object to be polished 1 such as a semiconductor wafer held on the lower end surface of the top ring.
In the polishing of 5, the measurement of the in-plane pressure distribution on the lower end surface of the top ring is performed by the piezoelectric element 32A functioning as a pressure sensor.
Is possible. Then, by the signal of the piezoelectric element 32A as the pressure sensor, the in-plane pressure distribution according to the command value can be given by using the piezoelectric element 32B by the feedback control circuit shown in FIG. This makes it possible to control the in-plane pressure distribution to a predetermined target value while measuring the actual in-plane pressure distribution on the lower end surface of the top ring.

In this embodiment, too, the upper and lower piezoelectric elements 32A and 32B are partially adhered, not entirely, to provide through holes for vacuum suction or fluid pressure supply. Of course, it is good.

FIG. 4 shows a configuration of a top ring according to a third embodiment of the present invention. In this embodiment, the piezoelectric elements 41 are arranged at equal intervals in the circumferential direction on the outer peripheral side of the top ring lower end face 16b, and the displacement sensor 42 is arranged at an intermediate position between the piezoelectric elements 41. This displacement sensor 42
A capacitance type, current type, induction type, or the like that can measure a displacement at a minute interval with the mat member 43 that contacts the workpiece 15 is used.

FIG. 5 is a block diagram of a control system according to the third embodiment. The displacement sensor 42 detects displacement of a gap between the mat member 43 and the back surface of the workpiece 15. Then, the output is subjected to coordinate conversion by the coordinate conversion circuit 45 and compared with the command value by the adder 46. Then, the deviation is input to the controller 47, and an output signal that makes the deviation zero by PID control or the like is generated. This signal is amplified by the amplifier 48, and the output voltage is applied to the piezoelectric element 41. As a result, the lower surface 16b of the top ring and the mat member 4 are adjusted so that the back surface of the object 15 has a predetermined command value.
3 is adjusted.

Therefore, the actual top ring lower end surface 16b
Polishing can be performed while measuring the displacement of the gap between the metal member and the mat member 43 while maintaining the size of the gap at a predetermined target value. Thereby, for example, even if the rotation axis is tilted,
By correcting the displacement by the piezoelectric element 41, a uniform polished surface of the object to be polished can be obtained, and the inclination of the object to be polished can be corrected.

FIG. 6 shows a configuration of a top ring portion according to a fourth embodiment of the present invention. As shown in the figure, a piezoelectric element 51 is mounted between the lower end 17 b of the rotating shaft 17 and the top ring 16. The piezoelectric element 51 has a single-layer structure as shown in FIG.
By applying a voltage to the piezoelectric element, a predetermined minute displacement is generated, whereby it is possible to correct and control the object to be polished, the inclination of the top ring, and the like. As shown in FIG. 2, this piezoelectric element has a two-layer structure of an upper layer and a lower layer, one of which is used as a pressure sensor, and the lower piezoelectric layer corresponds to the in-plane pressure distribution detected by the pressure sensor. The element may be controlled so that the in-plane pressure distribution is controlled to a predetermined target value.
Thus, the lower end 17b of the rotating shaft 17 and the top ring 1
By mounting a piezoelectric element between the head 6 and the workpiece 6, it is possible to easily correct the object to be polished, the inclination of the top ring, and the like.

Although the above embodiment shows several examples of mounting the piezoelectric element on the top ring, various modifications can be made without departing from the gist of the present invention. Of course.

[0024]

According to the present invention as described above,
Since the in-plane pressure distribution or inclination of the holding surface of the object to be polished at the lower end portion of the top ring can be easily adjusted, a highly uniform polished surface of the object to be polished can be obtained. In addition, since the in-plane pressure distribution or displacement relative to the lower end face of the top ring is detected and the piezoelectric element can correct the in-plane pressure distribution, the polishing can be performed. An arbitrary in-plane pressure distribution can be automatically given to the workpiece. Therefore, stable polishing can be performed with respect to the fluctuation of the rotating shaft or the fluctuation of the polishing cloth on the turntable.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing a configuration of a top ring portion according to a first embodiment of the present invention, and FIG.

FIG. 2 is a longitudinal sectional view showing a configuration of a top ring portion according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a control system of a top ring unit shown in FIG. 2;

FIG. 4A is a longitudinal sectional view and FIG. 4B is a view taken along a line BB, showing a configuration of a top ring portion according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a control system of a top ring unit shown in FIG. 4;

FIG. 6A is a vertical cross-sectional view showing the configuration of a top ring portion according to a fourth embodiment of the present invention, and FIG.

FIG. 7 is an explanatory diagram showing an overall configuration of a polishing apparatus.

[Explanation of symbols]

 15 Polished object 16 Top ring 17 Rotation axis 32, 32B, 41, 51 Piezoelectric element 32A, 42 Sensor 33 Elastic mat

Claims (3)

[Claims] 1. A turntable having a polishing cloth or a grindstone adhered to a surface thereof, and a top ring for holding an object to be polished, the turntable being held on the polishing cloth or the grindstone surface of the turntable by the rotating top ring. In a polishing apparatus for pressing the object to be polished and polishing the polished surface of the object to be polished,
A piezoelectric element is provided on the top ring, or a piezoelectric element is provided between a rotation shaft supporting the top ring and the top ring, and by adjusting an applied voltage of the piezoelectric element, A polishing apparatus for adjusting an in-plane pressure distribution or inclination of an object to be polished held by a ring. 2. A turntable having a polishing cloth or a grindstone attached to a surface thereof, and a top ring for holding an object to be polished, wherein the top ring is held on the polishing cloth or the grindstone surface of the turntable by the rotating top ring. In a polishing apparatus for pressing the object to be polished and polishing the polished surface of the object to be polished,
A piezoelectric element is provided on the top ring, or a piezoelectric element is provided between a rotating shaft supporting the top ring and the top ring, and a polishing object held by the top ring by the piezoelectric element. A polishing apparatus for detecting an in-plane pressure distribution. 3. The apparatus according to claim 1, wherein the top ring includes a sensor for measuring an in-plane pressure or a displacement of the object to be polished, and controls the piezoelectric element based on an output of the sensor. The polishing apparatus according to claim 1.