JP2004358638A - Method and device for polishing semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for polishing a semiconductor wafer which provide a highly flat semiconductor wafer. <P>SOLUTION: Temperatures at different positions in the thickness direction of a carrier plate 16 are measured by each thermocouple 17A-17E during polishing. Thus, the temperature of the plate 16 in actual polishing is measured. A warpage amount of the plate 16 is calculated from the temperature data. Also, on the basis of the temperature data, a supply amount of a polishing agent for reducing the warpage amount is controlled, the temperature of cooling wafer flowing in the internal flow path of a polishing platen 12 is controlled, and polishing pressure from a polishing head 13 to a silicone wafer W is controlled. As a result, a polishing rate in the polishing face of the wafer W is equalized. The flatness of the wafer W after the polishing is enhanced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for polishing a semiconductor wafer and a polishing apparatus for a semiconductor wafer, and more particularly, warpage of a wafer holding member during polishing by a temperature of the wafer holding member measured by a plurality of temperature sensors embedded at different depths of the wafer holding member. The present invention relates to a semiconductor wafer polishing method and a semiconductor wafer polishing apparatus for calculating an amount.
[0002]
[Prior art]
After chamfering, the surface of the etched silicon wafer is subjected to mechanical and chemical polishing in the next polishing step. Here, the surface is finished to a smooth and distortion-free mirror surface by the polishing machine.
A conventional polishing machine is provided with a polishing platen on which an upper surface is provided with a polishing cloth, and a polishing head which is disposed opposite to and above the polishing platen and on the lower surface of which a silicon wafer is held by a predetermined holding structure. ing.
At the time of polishing, by supplying an abrasive (slurry) containing abrasive grains to the polishing cloth, the silicon wafer rotating integrally with the polishing head is brought into sliding contact with the surface (polishing surface) of the polishing cloth. ,Grind.
[0003]
Polishing of a silicon wafer by such a polishing machine is promoted by frictional heat and reaction heat of an abrasive interposed between the polishing cloth and the silicon wafer on a sliding contact surface between the polishing cloth and the silicon wafer.
The frictional heat generates a predetermined temperature distribution on the surface of the polishing pad, and also generates a temperature distribution on the silicon wafer within the wafer surface. In addition, a predetermined temperature difference is generated also for the carrier plate holding the silicon wafer. Such a temperature difference of the wafer holding member affects the cooling effect of the abrasive supplied on the polishing pad, the cooling effect of the cooling water supplied to the internal flow path of the polishing platen, and the silicon head from the polishing head. This is caused by a difference in work amount due to variation in polishing pressure to be performed.
Then, the temperature difference in the wafer holding member adds a warp to the wafer holding member. That is, when the temperature of the inner portion in the radial direction of the wafer holding member was higher than that of the outer portion, the wafer holding member was warped downward. This greatly affects the flatness of the polished surface.
[0004]
Conventionally, as a method of measuring heat generated during polishing such as frictional heat and reaction heat (hereinafter, polishing heat), a non-contact type infrared radiation thermometer arranged above a side of a polishing platen is used for polishing. There is known a method of detecting the surface temperature of a polishing pad in the inside. The detection signal from the infrared radiation thermometer is sent to the control unit of the polishing machine, and in accordance with a command from the control unit based on the detection signal, the supply amount of the abrasive supplied on the polishing cloth, and the polishing platen. The temperature of the supplied cooling water is controlled to eliminate unevenness in the temperature of the surface of the polishing pad.
[0005]
[Problems to be solved by the invention]
As described above, the conventional method for detecting polishing heat cannot detect the amount of warpage of the wafer holding member of the semiconductor wafer that is actually being polished. Therefore, it has been difficult to increase the flatness of the polished surface of the semiconductor wafer.
[0006]
[Object of the invention]
An object of the present invention is to measure the temperature in the thickness direction of a semiconductor wafer holding member during polishing, calculate the amount of warpage based on the measured value, and further control polishing conditions and the like according to the amount of warpage. Accordingly, an object of the present invention is to provide a method for polishing a semiconductor wafer, which can improve the flatness of a polished surface of the wafer.
Also, the present invention measures the temperature at a plurality of positions in the thickness direction of the wafer holding member, calculates the amount of warpage of the wafer holding member, and based on the amount of warpage, makes the polishing rate in the plane of the semiconductor wafer uniform. It is an object of the present invention to provide a semiconductor wafer polishing apparatus capable of producing a semiconductor wafer having a high degree of flatness.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, when the semiconductor wafer held by the wafer holding member having a predetermined thickness is brought into sliding contact with the polishing cloth and the semiconductor wafer is polished, the thickness of the wafer holding member in the thickness direction is reduced. A method for polishing a semiconductor wafer for measuring temperatures at different depth positions, wherein the semiconductor temperature is measured by a plurality of temperature sensors buried separately at the different depth positions while the temperature of the wafer holding member is being polished. This is a method for polishing a wafer.
As a polishing apparatus for carrying out this method, for example, a method of vacuum-adsorbing a semiconductor wafer to a polishing head, a wax mounting method of bonding a semiconductor wafer to a polishing head via a carrier plate, or a bag containing water There is a waxless mounting method in which a semiconductor wafer is held on a polishing head by a pad.
Further, the polishing head may be arranged above and opposite to the polishing platen, or may be arranged upside down. The material of the polishing head is not limited. However, ceramics, low expansion coefficient metals (including alloys), cast iron, steel and the like are preferable.
The wafer holding member includes a polishing head or a carrier plate supported by the polishing head.
[0008]
For temperature measurement, for example, a contact-type temperature sensor such as a thermocouple, a bimetal thermometer, or a thermistor thermometer can be employed. Further, a non-contact type temperature sensor such as an optical pyrometer or a radiation thermometer for infrared rays or the like can be employed.
The temperature sensor may be embedded near the wafer holding surface of the head body of the polishing head. Alternatively, when a carrier plate is attached to the lower surface of the polishing head, it can be embedded in the carrier plate.
The number of temperature sensors used for one carrier (wafer holding member) may be two or three or more. These temperature sensors may be arranged not only in the thickness direction of the carrier but also in different positions in the radial direction. The warpage of the carrier can be calculated more accurately, and the temperature distribution on the wafer holding surface of the carrier can be measured.
[0009]
The detection signal from the temperature sensor may be transmitted directly to the control unit of the polishing apparatus by using, for example, a lead wire that passes through a wiring path formed along the axis of the rotation axis of the polishing head. In addition, a data logger is attached to the polishing head, and the digitally converted data is transmitted using a light emitting unit (such as an infrared light emitting type) and a light receiving unit provided between the polishing head and the apparatus body. Good. The control unit may directly create and display a temperature distribution during polishing based on the obtained temperature data. Alternatively, only the value of the temperature data may be output, and the temperature distribution may be tabulated or graphed manually by the operator based on the output value.
[0010]
The polishing cloth is usually spread on the surface of the polishing platen facing the polishing head. Examples of the polishing cloth include a hard urethane pad and a non-woven cloth pad.
Both the polishing cloth and the polishing head may be rotated, or only the polishing cloth or only the polishing head may be rotated.
As the abrasive, for example, a mixture of calcined silica, colloidal silica (abrasive grains), amine (processing accelerator), organic polymer (haze inhibitor), and the like can be used. Among them, colloidal silica is provided as a transparent or opaque milky white colloid liquid in which silicic acid fine particles are dispersed in water as primary particles without agglomeration.
As a semiconductor wafer, for example, a gallium arsenide wafer (GaAs wafer) or the like can be employed other than the typical silicon wafer.
[0011]
The invention according to claim 2 is the method for polishing a semiconductor wafer according to claim 1, wherein the amount of warpage of the wafer holding member is calculated based on temperature data measured by the plurality of temperature sensors.
Thermocouples are preferred as temperature sensors. The type of thermocouple is not limited. For example, various thermocouples such as B, R, and S specified by JIS can be adopted. The amount of warpage is calculated based on a temperature difference between a shallow position and a deep position of the wafer holding member.
[0012]
According to a third aspect of the present invention, there is provided a polishing platen on which a polishing cloth is stretched, a wafer holding member provided to face the polishing platen and holding a semiconductor wafer on a wafer holding surface thereof, and a wafer holding member. A semiconductor wafer polishing apparatus comprising: a plurality of temperature sensors buried at different depth positions in a thickness direction of a member so as to be spaced apart from each other and measuring a temperature of a wafer holding member at each depth position.
[0013]
According to a fourth aspect of the present invention, there is provided the polishing apparatus for a semiconductor wafer according to the third aspect, further comprising calculating means for calculating an amount of warpage of the wafer holding member based on a value detected by each of the temperature sensors.
The calculation means can be configured using, for example, a computer system. For example, data from a sensor is input, and the amount of warpage is calculated from these data using a predetermined program.
[0014]
[Action]
According to the present invention, at the time of polishing, each temperature at a different position in the thickness direction of the wafer holding member is measured by the plurality of embedded temperature sensors. Therefore, the temperature of the wafer holding member during actual polishing can be measured. Then, the amount of warpage of the wafer holding member of the semiconductor wafer is calculated based on the detected signal of the measured temperature data. Further, based on the obtained temperature data, the amount of warpage is reduced, for example, control of the supply amount of the abrasive, control of the temperature of the cooling water flowing through the internal flow path of the polishing platen, and further from the polishing head to the semiconductor wafer. Control the polishing pressure. As a result, the polishing rate in the polished surface of the semiconductor wafer can be made uniform, and as a result, the flatness of the polished wafer can be increased.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 4 are views showing an apparatus for polishing a semiconductor wafer according to one embodiment of the present invention.
In FIG. 1, reference numeral 10 denotes a batch-type polishing apparatus. The polishing apparatus 10 includes a polishing platen 12 on which a polishing pad 11 made of a hard urethane pad is spread, and a polishing head 13 disposed above the polishing table 12. And
[0016]
The polishing head 13 has a disk-shaped head main body 14. A thick annular flange 14a is integrally formed on the lower surface of the outer peripheral portion of the head main body 14. An annular cushioning body 15 made of silicone rubber is fixed to the lower end surface of the annular flange 14a. A ceramic carrier plate 16 having a thickness of 20 mm is detachably supported on the head body 14 via the buffer 15.
The carrier plate 16 has five silicon wafers W attached on its wafer holding surface (lower surface) by wax. In a portion of the wafer holding surface of the carrier plate 16 where one silicon wafer W is held, one virtual line passing through the center of the carrier plate 16 and the center of the silicon wafer W in plan view is provided. Are formed with five small holes 16a to 16e arranged at a constant pitch. Each of the small holes 16a to 16e has a different depth, and has a diameter of 1.5 to 2 mm reaching from the upper surface to the vicinity of the lower surface of the carrier plate 16. For example, the hole 16a is the shallowest (depth A), the hole 16b is slightly deeper (depth B), the hole 16c is next deeper (depth C), and the hole 16d is deeper (deep). D), the small hole 16e is the deepest (depth E).
The specific positions where the holes 16a to 16e are formed are shown below. That is, in plan view, a small hole 16a is formed at a position closest to the center of the carrier plate 16, a small hole 16c is formed at the center position of the wafer, and a small hole 16e is formed at a position farthest from the center of the carrier plate 16. Are formed, a small hole 16b is formed at an intermediate position between the small holes 16a and 16c, and a small hole 16d is formed at an intermediate position between the small holes 16c and 16e.
[0017]
Into the small holes 16a to 16e, a total of five thermocouples (temperature sensors) 17A to 17E for measuring the in-plane temperature of the carrier plate 16 held on the wafer holding surface are inserted and fixed, respectively. Specifically, a thermocouple 17A is provided in the small hole 16a, a thermocouple 17B is provided in the small hole 16b, a thermocouple 17C is provided in the small hole 16c, a thermocouple 17D is provided in the small hole 16d, and a thermocouple 17E is provided in the small hole 16e. Has been inserted. These thermocouples 17A to 17E can detect the temperature of the carrier plate 16 at the installation position.
A data logger 18 that converts the detection signals from the thermocouples 17A to 17E into digital data is attached to one side of the upper surface of the carrier plate 16. An annular weight 19 covered by a circular hood F in a plan view is mounted on the head body 14. The entire load (static load) of the polishing head 13 by the weight 19 is applied to the carrier plate 16 via the buffer 15.
[0018]
A lower end of a rotating shaft 20 extending from a rotating motor (not shown) built in an upper pedestal 10a of the polishing apparatus 10 is fixed on a central portion of the head body 14. On a part of the outer peripheral portion of the hood F, a light emitting unit 22 for transmitting the temperature data converted by the data logger 18 as an infrared signal toward a light receiving unit 21 provided on the lower surface of the upper mount 10a is provided. Fixed. The signal of the temperature data received by the light receiving unit 21 is sent to the control unit C.
A reflector 23 having a mirror-finished upper surface is fixed to a portion of the outer peripheral portion of the hood F opposite to the light emitting portion 22 about the rotation axis 20. On the lower surface of the upper pedestal 10a, a photoelectric sensor 24 that irradiates light toward the reflection plate 23 is provided at a position opposite to the light receiving unit 21 about the rotation axis 20. The timing of data transmission is measured by the photoelectric sensor 24, and an infrared signal including temperature data is emitted from the light emitting unit 22 to the light receiving unit 21 at the transmission timing.
Although not shown, a disc-shaped pressing plate is detachably fixed to the upper surface of the entire central portion of the carrier plate 16 via a pyramid-shaped silicone rubber. Further, an air cylinder is suspended from the center of the inner surface of the head body 14, and a pressure plate is fixed to the lower end of the rod. When the rod is protruded, the pressure plate moves downward, and the entire central portion of the carrier plate 16 is pushed downward. Accordingly, each silicon wafer W attached to the carrier plate 16 is pressed against the polishing pad 11 of the polishing platen 12 with a predetermined pressure (center load).
[0019]
Next, the operation of the polishing apparatus 10 according to this embodiment will be described.
At the time of polishing, a predetermined load and a relative speed are applied between the polishing cloth 11 and each silicon wafer W while supplying an abrasive containing abrasive grains such as calcined silica or colloidal silica to the polishing cloth 11 on the polishing platen 12. This is done by giving
During this polishing, the entire load of the weight 19 acts on the outer peripheral portion of the carrier plate 16 from the annular flange 14a via the buffer 15. A center load acts on the center of the carrier plate 16 by an air cylinder (not shown). That is, the silicon wafer W is mirror-polished while maintaining the balance between the static load and the center load.
[0020]
At this time, the temperature in the plane of the carrier plate 16 during polishing is detected as a voltage by the five thermocouples 17A to 17E. Each detection signal is converted into a digital signal by the data logger 18 and then transmitted as an infrared signal from the light emitting unit 22 to the light receiving unit 21 at a predetermined timing measured by the photoelectric sensor 24. Next, the signal received by the light receiving unit 21 is sent to the control unit C, and the control unit C calculates and creates a time-dependent temperature distribution in the plane of the carrier plate 16 based on the temperature data. The created temperature distribution is displayed on a monitor as shown in the graph of FIG. 3 and printed out by a printer.
Further, the amount of warpage of the carrier plate 16 during the polishing is calculated based on these temperatures.
Based on the temperature distribution and the amount of warpage thus obtained, the temperature in the polished surface of the carrier plate 16 is kept constant, for example (or so as to have a specific temperature distribution), and the amount of warpage maintains a predetermined condition. The polishing conditions are changed so that For example, control of the supply amount of the abrasive, control of the temperature of cooling water (not shown) flowing through the internal flow path of the polishing platen 12, control of the center load by the air cylinder, and the like are performed. In particular, the control of the amount of warpage is performed by controlling the center load. As a result, the polishing rate is made uniform within the polishing surface of the carrier plate 16, whereby the flatness of the polished silicon wafer W can be increased.
The control of the amount of warpage or the like can also be achieved by conforming to the condition when the flatness of the polished surface of the obtained polished wafer is high.
[0021]
【The invention's effect】
According to the present invention, during polishing, the temperature of the semiconductor wafer at different positions in the thickness direction of the wafer holding member is measured by a plurality of temperature sensors, and the amount of warpage of the wafer holding member is calculated based on the detection signals. Therefore, the wafer being polished can be kept flat, and as a result, a semiconductor wafer with high flatness can be obtained.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view of a polishing apparatus for a semiconductor wafer according to one embodiment of the present invention.
FIG. 2 is a plan view of a carrier plate according to one embodiment of the present invention.
FIG. 3 is a graph showing a temperature change over time in a plane of a semiconductor wafer during polishing according to an embodiment of the present invention.
FIG. 4 is a longitudinal sectional view showing a sensor embedding portion of a carrier plate according to one embodiment of the present invention.
[Explanation of symbols]
10 polishing equipment,
11 polishing cloth,
13 polishing head,
17A-17E thermocouple (temperature sensor),
C control unit,
W Silicon wafer (semiconductor wafer).

Claims (4)

When a semiconductor wafer held by a wafer holding member having a predetermined thickness is slid against a polishing cloth and the semiconductor wafer is polished, temperatures at different depth positions in the thickness direction of the wafer holding member are measured. A method of polishing a semiconductor wafer,
A method for polishing a semiconductor wafer, wherein the temperature of a wafer holding member during polishing is measured by a plurality of temperature sensors buried separately at different depth positions. 2. The method according to claim 1, wherein the amount of warpage of the wafer holding member is calculated based on temperature data measured by the plurality of temperature sensors. A polishing platen on which a polishing cloth is stretched,
A wafer holding member that is arranged to face the polishing platen and holds a semiconductor wafer on its wafer holding surface,
An apparatus for polishing a semiconductor wafer, comprising: a plurality of temperature sensors buried separately at different depth positions in the thickness direction of the wafer holding member and measuring the temperature of the wafer holding member at each depth position. 4. The apparatus for polishing a semiconductor wafer according to claim 3, further comprising a calculating unit configured to calculate an amount of warpage of the wafer holding member based on a value detected by each of the temperature sensors.

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