JP2001353657A - Wafer polishing device and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer polishing device and a polishing method, capable of eliminating irregularity in finishing flatness and polishing degree of wafers between polishing processes, and improving a throughput. SOLUTION: A carrier 22 or 28 for holding a wafer W, and a heating means 31 for heating the carrier 22 or 28 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a polishing method for mirror-polishing a wafer surface such as a semiconductor wafer with high precision.

[0002]

2. Description of the Related Art In recent years, patterns have been increasingly miniaturized with the increase in the degree of integration of semiconductor manufacturing equipment. In particular, in order to easily and surely form fine patterns having a multilayer structure, the semiconductor wafer itself on which the patterns are formed Needless to say, it is becoming important to make the surface of the semiconductor wafer as flat as possible during the pattern formation process. As a polishing method for flattening the surface of these semiconductor wafers (hereinafter simply referred to as wafers), a chemical mechanical polishing method (CMP method) having a high degree of finished flatness has been spotlighted.

The CMP method includes SiO2, CeO2,
This is a method of chemically and mechanically polishing and flattening the wafer surface using a slurry mixed with an abrasive such as Al2O3. As a wafer surface polishing apparatus employing the CMP method, for example, the one shown in FIG. 3A is known.

In this wafer polishing apparatus, a disk-shaped rotary table (platen) 2 attached to a central shaft 1, a polishing pad 3 made of hard urethane or the like provided on the platen 2, and eccentric from the central shaft 1. A wafer holding head 4 which is opposed to the polishing pad 3 at the set position and is driven to rotate by a head driving mechanism (not shown); And a conditioner 5 for dressing the surface of the polishing pad 3. As shown in FIG. 3A, the wafer polishing apparatus includes only one wafer holding head 4 and polishes wafers W one by one in one polishing process. And a plurality of wafers W in one polishing process.
Are polished simultaneously.

A wafer holding head (hereinafter, simply referred to as a holding head) 4 has a disk shape smaller in diameter than the polishing pad 3, and is held by an arm (not shown) at an upper end of a rotating shaft 4 a thereof. It can approach and separate.
Therefore, the wafer W can be brought into contact with the polishing pad 3 while holding the wafer W on a carrier (not shown) provided below the holding head 4 (head end portion), and the wafer W can be carried in and out of the polishing pad 3. It can be carried out.

At the time of polishing the wafer W, the abrasive is supplied onto the polishing pad 3 as a liquid slurry S, flows between the wafer W held by the holding head 4 and the polishing pad 3, and Since the wafer W held by the wafer 4 rotates and the polishing pad 3 rotates about the central axis 1 at the same time, the lower surface of the wafer W is polished.

The conditioner 5 includes an arm 7 having a base fixed to a rotating shaft 6 provided outside the platen 2.
A state supported by the free end of the arm 7 and driven to rotate by a driving device (not shown) in contact with the surface of the polishing pad 3, or a state in which rotation is allowed by a frictional force received from the polishing pad 3. And a dresser 8 provided in the main body. Then, the surface of the polishing pad 3 is dressed by the rotation of the arm 7 and the rotation of the dresser 8.

The wafer holding head 4 is, for example, as shown in FIG.
A floating type shown in (2) and a gimbal type shown in FIG. 3 (3) are known.

The floating type wafer holding head shown in FIG. 3 (2) has a head main body 9 composed of a top plate and a cylindrical peripheral wall, and a diaphragm (circle) stretched in the head main body substantially perpendicular to the head axis. A plate-shaped or ring-shaped fiber reinforced rubber film) 10, a disc-shaped carrier 11 made of a highly rigid material such as ceramic fixed to the lower surface of the diaphragm 10, and a gap between the carrier 11 and the peripheral wall of the head body 9. , And an annular retainer ring 12 fixed to the lower surface of the diaphragm 10. The carrier 11 and the retainer ring 12 can move in the head axis direction due to the elastic deformation of the diaphragm 10.

A shaft portion 13 provided on a top plate portion of the head body 9 and screwed to a spindle of the arm has a flow path 1
3a is formed in the vertical direction, and a fluid chamber 9a is formed above the diaphragm 10 of the head main body 9. Then, a fluid such as air is supplied from the flow path 13a to the fluid chamber 9a.
Is supplied in an adjustable manner. Therefore, the internal pressure of the fluid chamber 9a,
That is, the displacement force in the head axis direction of the carrier 11 displaced together with the diaphragm 10 can be adjusted, and the wafer W held on the carrier 11 via a sponge-like back pad 14 called an insert is applied to the polishing pad 3. The abutment pressure can be adjusted to an optimal one.

The gimbal type wafer holding head shown in FIG. 3 (3) has a head main body 15 composed of a top plate and a cylindrical peripheral wall, and a disk made of a highly rigid material such as ceramic fixed and housed in the head main body. A shaft portion 17 screwed to the spindle of the arm is connected to a top plate portion of the head main body 15 via a spherical bearing 18. Therefore, the wafer W held by the carrier 16 can be brought into close contact with the polishing pad 3.

[0012]

In any of the above types of wafer holding heads, chemical and mechanical heat is generated during wafer polishing. Therefore, it is necessary to avoid deformation of the carrier and the back pad due to the heat generated. Can not. The thermal deformation has a great effect on the polishing performance such as the finished flatness of the wafer and the polishing amount.

Normally, in a wafer polishing apparatus, a wafer is replaced every time a single wafer polishing process is completed.
The wafer is polished one after another. The carrier temperature increases during polishing of the wafer, as shown in FIG.
During the replacement of the wafer or during the cleaning of the polishing pad, the heat is dissipated and drops again. Here, since the amount of heat radiation of the carrier is smaller than the amount of heat generated during wafer polishing,
From the time when the operation of the wafer polishing apparatus is started to the time when the polishing processing of the wafer is repeated several times to reach a certain temperature, the temperature of the carrier tends to gradually increase with each polishing processing. For this reason, between the start of the operation of the wafer polishing apparatus and the repetition of the wafer polishing process several times, the amount of deformation of the carrier and the back pad varies, and during this time, the finished flatness and the polishing amount of the polished wafer are varied. Become irregular and unstable.

This can be seen from the graphs of FIGS. 5 and 6. The five graphs in both figures correspond to the respective polishing processes in FIG. 4 and show the relationship between the distance from the center of the wafer (horizontal axis) and the degree of polishing (vertical axis). The degree of polishing of each portion of the wafer is related to the pressure at which each portion of the wafer is pressed against the polishing pad by the carrier, and these graphs reflect the deformation of the carrier. In FIG. 5, the distance from the center of the wafer, the degree of polishing, and the degree of polishing corresponding to each polishing process when the polishing process is repeatedly performed under the condition that the polishing amount of the entire wafer is uniform at the beginning of polishing (before the carrier temperature rises) are uniform. Shows the relationship. Similarly, in FIG. 6, in the initial stage of the polishing start (before the carrier temperature rise), the polishing process is repeatedly performed under the condition that the degree of polishing in the central portion is smaller than that in the outer peripheral portion of the wafer. The relationship between the distance from the center and the degree of polishing is shown. That is, when the wafer is polished under the polishing conditions shown in FIG. 5, after the first polishing process, the degree of polishing of the wafer gradually increases toward the center until the wafer becomes stable (thickness). Becomes thinner). When the wafer is polished under the polishing conditions shown in FIG. 6, the polishing degree of the wafer becomes larger (thinner) toward the outer periphery in several polishing processes after the start of polishing. In any of these cases, it is necessary to repeat the polishing process several times before the polishing performance starts to be stabilized. Therefore, break-in or break-in or dummy run is usually performed a plurality of times before the start of polishing. The required number of break-in polishing and the carrier temperature after the break-in polishing are
Although it depends on the configuration of the wafer polishing apparatus and the polishing conditions, in any case, a dummy wafer for break-in polishing is required, which is uneconomical. It also takes the trouble of running in,
Throughput had peaked out.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer polishing apparatus and a polishing method which do not vary in finished flatness and polishing degree of a wafer between polishing treatments and can improve throughput.

[0016]

According to a first aspect of the present invention, there is provided a wafer polishing apparatus having a carrier for holding a wafer, wherein the carrier is provided with heating means for heating the carrier. It is characterized by. In the wafer polishing apparatus configured as described above, the carrier is heated by the heating means without performing break-in polishing. Then, the carrier is heated to, for example, the same temperature as the state after the break-in and polishing by the heating means, so that the deformation amount of the carrier is stabilized. Here, in the career,
On the side where the wafer holding surface is formed, heat generated during polishing of the wafer is received, and on the other side, heat of the carrier is released to the surroundings, so that a thermal gradient is generated in the carrier in the thickness direction. When a thermal gradient is generated in the carrier in this manner, a difference occurs in the amount of thermal expansion between the high temperature side and the low temperature side of the carrier, and the carrier is warped (thermal deformation). In this case, for example, the entire carrier (or at least most of the carrier) is heated by a heating unit, or a heating unit is provided on a side where the wafer holding surface is not formed, and this portion is heated to make the entire carrier substantially uniform. By setting the temperature, thermal deformation of the carrier itself (excluding thermal expansion) can be suppressed. Further, in the carrier, heat is more likely to be released to the outside at the outer periphery than at the center, so that the carrier tends to have a thermal gradient in the radial direction. For this reason,
For example, by providing a heating unit independently at the center and the outer periphery of the carrier and heating the carrier so that the center and the outer periphery have substantially the same temperature, thermal deformation of the carrier can be suppressed. When suppressing the thermal deformation itself of the carrier in this way, it is not always necessary to heat the carrier to a state where the carrier has been used up and the operation has been completed.

In the above wafer polishing apparatus, a heating temperature setting means for setting a temperature range for heating the carrier, a temperature detecting means for sensing the temperature of the carrier, and a control means for controlling the operation of the heating means. The control means calculates the temperature of the carrier based on the signal from the temperature detection means, compares the temperature with a set temperature range set in the heating temperature setting means, and sets the temperature of the carrier to the set temperature. The heating of the carrier by the heating means is continued when the temperature is lower than the range, and the heating by the heating means is stopped when the temperature of the carrier is higher than the set temperature range. In the wafer polishing apparatus configured as described above, the temperature of the carrier heated by the heating unit is detected by the temperature detection unit, and the control unit is set by the heating temperature setting unit based on a signal from the temperature detection unit. The heating temperature range and the temperature of the carrier are compared. When the temperature of the carrier is lower than the set range, the control device continues heating by the heating unit to further heat the carrier, and when the temperature of the carrier is higher than the set temperature range, stops the heating and stops the carrier. cool. As a result, the carrier is maintained in a set temperature range, for example, a temperature after the break-in polishing in the conventional wafer polishing apparatus, and the deformation amount of the carrier is stabilized. Here, a plurality of heating means may be provided independently for each part of the carrier, for example, and in this case, each heating means is independently controlled.

According to a third aspect of the present invention, in the wafer polishing method, the wafer is polished after the carrier is heated within a set temperature range to be in a stable state, and thereafter, the set temperature of the carrier is maintained. . In such a wafer polishing method, the temperature of the carrier is maintained within a set temperature range, and the wafer is polished in a state where its shape is stable.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wafer polishing apparatus according to the present invention will be described with reference to FIGS. This wafer polishing apparatus has a basic configuration including a platen (2), a polishing pad (3), a wafer holding head (4) and the like, which is the same as that shown in FIG.
A heating means such as a heater and a temperature sensor (temperature detection means) are built in or brought into contact with a carrier which is a member for holding the wafer W in the wafer holding head, and a control device (control means) is provided for the heating means and the temperature detection means.
Is connected to the control device, and a heating temperature setting means for setting a temperature range for heating the carrier is connected to the control device, whereby the carrier can be heated to a preset target temperature or a target temperature range. . Therefore, a detailed description of the basic configuration is omitted to avoid duplication.

First, referring to FIG. 1A, an example of application to a floating type wafer holding head will be invented.

The basic structure of this wafer holding head is the same as that shown in FIG. 3B described as a conventional example. That is, the head main body 2 including the top plate portion and the cylindrical peripheral wall portion
0, a diaphragm 21 made of a ring-shaped fiber-reinforced rubber film stretched substantially perpendicularly to the head axis in the head body.
And a disc-shaped carrier 22 made of a highly rigid material such as ceramic fixed to the lower surface of the diaphragm 21, and an annular ring fixed to the lower surface of the diaphragm 21 between the carrier 22 and the peripheral wall of the head body 20. Retaining ring 23
It is composed of

A flow path 24a is formed vertically in a shaft portion 24 provided on a top plate portion of the head main body 20, and a fluid chamber 20a is formed above a diaphragm 21 of the head main body 20. ing. A fluid such as air is supplied to the fluid chamber 20a from the flow path 24a in an adjustable manner.

The present invention further provides a heater 2 in the carrier 22.
5 and the temperature sensor (temperature detecting means) 26 are built-in or in contact with each other. In the drawing, the heaters 25 are embedded in the upper surface of the carrier 22, and the temperature sensors 26 are built in the respective heaters 25. Here, the heater 25 and the temperature sensor 26 are connected to the carrier 22.
Instead of being embedded in the upper surface of the carrier 22, an opening is formed in the diaphragm 21 at a position facing at least a portion where the heater 25 and the temperature sensor 26 are installed on the upper surface of the carrier 22, and a heater is formed on the upper surface of the carrier 22 through this opening. 25 and the temperature sensor 26 may be arranged in contact. The heaters 25 are provided in an annular shape on the outer peripheral portion of the carrier 22 and are small disk-shaped ones occupying the center. The temperature sensors 26 are arranged at appropriate positions of the respective heaters 25. Instead of such an arrangement, the size of the heater 25 may be substantially the same as the entire surface of the carrier 22, and the size of the fluid chamber
It is also possible to employ heated air as the fluid to be supplied to a. These heater 25 and temperature sensor 26
Are connected to a control device C (not shown in FIG. 1), and the control device C controls the operation of the heater 25 based on a signal received from the temperature sensor 26 (current and voltage supplied to the heater 25). Etc.). The type of temperature control performed by the control device C will be described later. The control device C is connected to a heating temperature setting device (not shown) that can set the heating temperature. In addition, what is indicated by the symbol P is the carrier 22.
This is a sponge-like back pad interposed when the wafer W is held on the substrate.

Next, an example of application to a gimbal type wafer holding head will be described with reference to FIG.

The basic structure of this wafer holding head is the same as that shown in FIG. 3 (3) described as a conventional example. That is, the head main body 2 including the top plate portion and the cylindrical peripheral wall portion
7 and a disc-shaped carrier 28 made of a highly rigid material such as ceramics fixedly housed in the head main body, and a shaft portion 29 screwed to the spindle of the arm is provided on the head main body 27 via a spherical bearing 30. It is configured to be connected to the top plate.

The present invention further provides the carrier 28 with a heater 3.
1 and a temperature sensor (temperature detecting means) 32 are built in or brought into contact with each other, and a feature is that a controller C (control means) is connected to the heater 31 and the temperature sensor 32. In the illustrated embodiment, the heater 31 is disposed in contact with the upper surface of the carrier 28, and its size is made to substantially match the entire surface of the carrier 28. Further, the temperature sensor 32 is arranged in contact with the upper surface of the carrier 28. Heater 3
1 instead of such an overall configuration, for example, FIG.
As shown in (3) and (4), the heater 31 is formed in an annular shape along the edge of the carrier 28 and in a small disk shape occupying the center, and the temperature sensors 32 are placed at appropriate positions of the respective heaters 31. It may be arranged.

Here, with reference to FIG. 2, a description will be given of the temperature control of the carriers 22, 28 which are the main part of the wafer polishing method of the present invention.

In carrying out the wafer polishing method of the present invention, the heating temperature of the carriers 22 and 28 is set at a target value or a target range (hereinafter, referred to as a target temperature), that is, polishing after finishing the conventional break-in polishing. The temperature must be set in advance to a temperature equal to or higher than the carrier temperature at the start. The target temperature differs depending on the configuration of the wafer polishing apparatus and the polishing conditions when performing continuous polishing. Therefore, a heating temperature setting device (not shown) that can set a target temperature is connected to the control device C of the wafer polishing apparatus, and when a polishing condition is input to the control device C, the target temperature is set by an operator. A target temperature is automatically calculated from the input or input polishing conditions, and the set target temperature value is stored in a storage device (not shown). Actual polishing of the wafer W is performed in a state where the carriers 22 and 28 are heated to the target temperature and then maintained at the target temperature.

Heating the carriers 22, 28 to a target temperature;
The subsequent maintenance of the target temperature is performed as follows. That is, the carrier 2 is controlled by the control device C of the wafer polishing apparatus based on the sensor signal emitted from the temperature sensor.
2 and 28 are detected (S1), and the detected temperatures are compared with the target temperatures of the carriers 22 and 28 set in the heating temperature setting device (S2). Therefore, if the detected temperature is equal to or lower than the target temperature (in the case of NO), the heaters 25 and 31 are energized, and if the detected temperature is equal to or higher than the target temperature (Y
In the case of ES), the power supply to the heaters 25 and 31 is stopped (S4). Hereinafter, the processing of S1 to S4 is repeated.

In the wafer polishing apparatus having such a function, the carriers 22 and 28 are heated to a target temperature (for example, the same temperature as that after the conventional break-in polishing), and then the polishing of the wafer W is started. The polishing process is performed while maintaining the target temperature. Thereby, the carriers 22, 2
The temperature of Step 8 becomes stable (substantially the same as the state after the conventional break-in operation), and a stable polishing performance without variation in the finished flatness and polishing degree from the first polishing processing to each polishing processing is obtained. Can be. In addition, break-in or break-in polishing which is conventionally required, which is called dummy run, becomes unnecessary, and therefore, auxiliary materials such as a dummy wafer and slurry become unnecessary, which is economical. In addition, since the time spent for break-in polishing is not required, the throughput can be improved.

Here, the side of the carrier that receives the heat generated during polishing of the wafer is the lower surface, and the upper surface emits the heat of the carrier to the surroundings. Further, in the carrier, heat is easily released to the outside at the outer peripheral portion with respect to the central portion where heat is likely to be stored. As described above, the carrier is thermally deformed due to a thermal gradient in the thickness direction and the radial direction. In the carrier 22, the heater 25 is provided on the upper surface, and the heater 25 is provided independently on the center side and the outer peripheral side on the upper surface. These heaters 25 target the center side and the outer peripheral side of the upper surface of the carrier 22, respectively. Since the carrier 22 is heated to a temperature, the carrier 22 has a substantially uniform temperature as a whole, and thermal deformation is suppressed. That is, in the carrier 22,
Since the wafer holding surface is formed flat in advance and the deformation of the wafer holding surface is suppressed even during polishing, in the wafer polishing apparatus using the carrier 22, polishing is performed in a state where the entire surface of the wafer W is pressed with a uniform pressure. can do. Thereby, in the wafer polishing apparatus using the carrier 22, in addition to obtaining the stable polishing performance as described above, the polishing amount is made substantially uniform over the entire surface of the wafer W,
The finish of the wafer W can be improved. Here, in order to suppress the thermal deformation of the carrier 22, it is not always necessary to heat the carrier 22 to a state where the operation is completed.

Here, in the above embodiment, the carrier 2
2, the heater 25 is provided independently at the center and the outer periphery of the upper surface.
1, the heater 25 is provided on almost the entire upper surface of the carrier 22, and the heater 31 is provided independently on the center and the outer periphery of the upper surface of the carrier 28. You may.

[0033]

According to the wafer polishing apparatus of the first aspect, break-in polishing is not required, and a stable polishing performance without variation in finish flatness and polishing degree from the first polishing process to each polishing process is obtained. be able to. In addition, break-in or break-in polishing which is conventionally required, which is called dummy run, becomes unnecessary, and therefore, auxiliary materials such as a dummy wafer and slurry become unnecessary, which is economical. In addition, since the time spent for break-in polishing is not required, the throughput can be improved.

According to the wafer polishing apparatus of the second aspect, the temperature of the carrier is maintained within the set temperature range.
The amount of deformation of the carrier during each polishing process is stabilized, and a stable polishing performance without variation in the finished flatness and the polishing degree between the polishing processes can be obtained.

According to the third aspect of the present invention, since the wafer is polished in a state in which the shape of the carrier is stable, the finished flatness and the degree of polishing of the wafer are stable without variation between the polishing processes. Polishing performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a view of a wafer holding head constituting a wafer polishing apparatus of the present invention, wherein (1) is a vertical sectional view of a floating system, (2) is a vertical sectional view of a gimbal system, and (3).
Is a longitudinal sectional view showing the arrangement of a heater and a temperature sensor on a carrier, and (4) is a plan view of the same.

FIG. 2 is a flowchart showing carrier heating control in the wafer polishing apparatus of the present invention.

FIG. 3 is a view of a conventional wafer polishing apparatus, (1)
2 is an enlarged perspective view of a main part, (2) is a longitudinal sectional view of a floating type wafer holding head constituting the same apparatus, and (3) is a longitudinal sectional view of a gimbal type wafer holding head constituting the same apparatus.

FIG. 4 is a graph (graph) showing the relationship between the elapsed polishing time and the carrier temperature from the start of operation to the point in time when the polishing process is repeated a plurality of times in the conventional wafer polishing apparatus.

FIG. 5 shows the distance from the center of the wafer, the degree of polishing, and the polishing degree corresponding to each polishing process when the polishing process is repeatedly performed under the condition that the polishing amount of the entire wafer is uniform at the beginning of polishing (before the carrier temperature rises). FIG. 4 is a diagram (graph) showing the relationship of FIG.

FIG. 6 is a diagram showing the relationship between the center of the wafer corresponding to each polishing process when the polishing process is repeatedly performed at the beginning of polishing (before the carrier temperature rise) under the condition that the degree of polishing at the center is smaller than that at the outer periphery of the wafer. It is a figure (graph) which shows the relationship between a distance and a polishing degree.

[Explanation of symbols]

22, 28 Carrier 25, 31
Heater (heating means) 26, 32 Temperature sensor (temperature detecting means) C Controller (control means) W Wafer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toyohisa Kongoji 1-297 Kitabukurocho, Omiya-shi, Saitama Mitsubishi Materials Corporation Intelligent Equipment and Systems Development Center F-term (reference) 3C058 AB04 AC01 AC02 BA08 BB01 BB09 BC01 CB01 CB03 DA17

Claims (3)

[Claims] 1. A wafer polishing apparatus having a carrier for holding a wafer, wherein the carrier is provided with heating means for heating the carrier. 2. A heating temperature setting means for setting a temperature range for heating the carrier, a temperature detecting means for sensing a temperature of the carrier, and a control means for controlling an operation of the heating means, The control means calculates a temperature of the carrier based on a signal from the temperature detection means, compares the temperature with a set temperature range set in the heating temperature setting means, and sets the temperature of the carrier to a set temperature range. The heating of the carrier by the heating unit is continued when the temperature is lower than the heating unit, and the heating by the heating unit is stopped when the temperature of the carrier is higher than the set temperature range. A wafer polishing apparatus as described in the above. 3. A wafer polishing method, comprising: starting a wafer polishing after a carrier is heated to within a set temperature range to be in a stable state, and thereafter maintaining the set temperature of the carrier.