JP2000343415A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the temperature of a sample uniform by providing a sample holding table with nozzles for supplying a cooling gas-liquid mist to the back face of a plate-like sample. SOLUTION: A plurality of cooling nozzles 109 for cooling a sample from the back face are arranged on the sample back face side of a sample holding table 106. The cooling nozzles 109 are connected to a passage 110 provided inside the sample holding table 106. The passage 110 is connected to an air tube 111 and a liquid tube 112, and compressed air and liquid are respectively supplied from the air tube 111 and liquid tube 112. A mixture of air and liquid is made into an air-liquid mist with liquid in a fine mist state by the action of the nozzles 109, and the back face of the sample 107 is cooled by this mist flow. The mist flow exhibits large cooling capacity by covering the cooled face with a thin liquid film and further increases the cooling effect by taking away latent heat while evaporating from the back face of the sample 107.

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 flat sample while supplying a polishing liquid, and particularly to a silicon wafer, a quartz substrate, a ceramic substrate, a metal substrate, and a wafer in the course of an LSI manufacturing process. The present invention relates to a polishing apparatus for polishing.

[0002]

2. Description of the Related Art FIG. 4 is a side view showing an outline of a conventional polishing apparatus for polishing a semiconductor substrate. Reference numeral 101a in FIG.
Is a polishing surface plate having a circular shape in plan view, and a polishing surface
To rotate horizontally. A polyurethane-based polishing cloth 101b is adhered on the polishing platen 101a, and the polisher 101 is constituted by the polishing platen 101a and the polishing cloth 101b. This polisher 101
A plurality of sample holders 102 smaller than the radius of the polisher 101 are disposed above the polisher 101.
A plate-like sample 107 is held on the polisher 101 side. The sample holder 102 is provided on the polishing table 10.
Independently from 1a, it is rotated in the horizontal direction by the sample holder rotating shaft 12. Further, a structure (not shown) capable of pressing the sample 107 is incorporated in the sample holding unit 102, so that an appropriate polishing pressure can be applied to the sample 107. A polishing liquid supply nozzle 121 is provided at an upper central portion of the polisher 101. The polishing liquid 101 is rotated while supplying the polishing liquid 10 from the polishing liquid supply nozzle 121 to the polisher 101, and the sample holding part 102 is also separated from the polisher 101. When the polishing liquid 10 is rotated independently, the polishing liquid 10
01b and polishing proceeds.

[0003] The polishing liquid is typically in the form of a slurry containing free abrasive grains in a liquid which is chemically active with respect to the portion to be polished. Polished by mechanical grinding with loose abrasives.

As a structure for uniformly pressing a sample to be polished against a polishing cloth, for example, Japanese Patent Application Laid-Open No. 9-198163 discloses an apparatus for obtaining a uniform load by holding a sample holder in a bellows chamber and applying air pressure to the bellows. It has been disclosed.

FIG. 5 is a longitudinal sectional view showing a main part of a sample holding section disclosed in the publication. 4, the same elements as those in FIG. 4 are denoted by the same reference numerals. The sample holding unit 102 has a housing plate 103 integrated with the sample holding unit rotation shaft 12, a bellows chamber 104 and a sample holding ring unit 105 attached thereto, and a sample holding table 106 attached to the bellows chamber 104. By pressing the inside of the bellows chamber 104 through the second air pipe 113, the sample 1
07 is pressed against the polisher 101. At the same time, a pressure is applied to the back pressure chamber 108 formed by the sample holding table 106 and the sample 107 through the first air pipe 111 so that a uniform load is applied to each portion of the polished surface of the sample 107.

Generally, in a polishing apparatus that performs polishing while supplying a polishing liquid, the sample 107 is heated from the polishing surface by so-called polishing heat such as frictional heat during polishing, mechanical processing heat, and chemical reaction heat. In the polishing apparatus, heat entering the sample 107 from the polishing surface is radiated from the back surface of the sample 107 to the sample holding unit 102 by heat conduction. However, among the sample holders, the thermal conductivity of the sample holder 106 which is in direct contact with the sample is determined by the heat conductivity shown in FIG.
As is clear from the structure, the sample 107 is close to the thermal conductivity of air, and the temperature of the sample 107 increases as the amount of heat input increases. This temperature is the temperature at which the reliability of the sample surface is guaranteed (for example, an integrated circuit pattern is formed on the sample surface). In this case, the reliability assurance temperature is often set to 100 to 120 ° C.). In addition, the sample 107 is deformed by the thermal stress generated by the temperature rise, and the flatness of the surface to be polished cannot be maintained, which causes a problem that the sample surface cannot be polished uniformly.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to maintain the temperature of a sample to be polished below a reliability assurance temperature in a conventional polishing apparatus, or to impair the flatness of a polished surface due to deformation caused by thermal stress. It is an object of the present invention to provide a polishing apparatus capable of keeping the temperature of a sample uniform so as not to cause a problem.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors conducted various experiments and studies to develop a polishing apparatus capable of efficiently cooling a sample, and as a result, obtained the following findings. .

(A) By appropriately supplying a cooling gas to the back surface (the surface that is not polished) of the sample, the cooling of the sample is greatly accelerated compared to the cooling by the stationary gas layer. Furthermore, if a gas-liquid mist in which fine droplets are dispersed in a cooling gas is supplied, the cooling effect is greater. That is, the back surface of the sample is covered with the liquid film, and the cooling effect is enhanced by the high thermal conductivity and heat capacity of the liquid. Furthermore, when the amount of heat flowing into the sample from the polished surface is large, the liquid film covering the back surface of the sample is vaporized, and the sample is efficiently cooled to take away latent heat of evaporation.

As a structure for this purpose, a nozzle for supplying gas-liquid mist to the back surface of the sample is provided on the sample holder of the polishing apparatus, and the arrangement and the supply amount of gas-liquid mist are appropriately adjusted. A polishing apparatus capable of efficiently cooling the sample to be obtained is obtained.

(B) Further, if the temperature distribution on the back surface of the sample can be grasped from the temperature measurement during test polishing, the supply state of the polishing liquid, the initial shape of the sample, and the like, the cooling gas is transferred to the high temperature portion (heating portion) of the sample. By selectively supplying the liquid mist, the sample temperature distribution can be made more uniform, and the cooling performance can be further improved.

The present invention has been made based on such findings, and the gist lies in the following (1) and (2).

(1) Between a plate-like sample held by a rotating sample holding table and a polisher having a polishing material attached to a rotating polishing plate, which is disposed in parallel with the plate-like sample and is opposed to the rotating platen. A polishing apparatus for polishing a flat sample while supplying a polishing liquid, wherein the sample holding table is provided with a nozzle for supplying a gas-liquid mist for cooling to the back surface of the flat sample. Characteristic polishing equipment.

(2) A plurality of nozzles of gas-liquid mist for cooling are provided, and the distribution of gas-liquid mist supply to each line can be changed to adjust the cooling amount distribution on the back surface of the flat sample. The polishing apparatus according to the above (1), characterized by having a simple adjustment valve.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of a polishing apparatus according to the present invention will be described below using an example of a polishing apparatus.

FIG. 1 is a schematic view showing an example of a sample holder of a polishing apparatus according to the present invention. FIG. 1 (a) is a longitudinal sectional view, and FIG.
FIG. 2 is a sectional view taken along line AA of FIG.

In FIG. 3, the same elements as those in FIGS. 4 and 5 are denoted by the same reference numerals. In the following, the cooling gas will be described as air.

A plurality of cooling nozzles 109 for cooling the sample from the back side are provided on the sample back side of the sample holding table 106. The cooling nozzle 109 is connected to the sample holder 106.
Is connected to a flow path 110 provided inside. The flow path 110 is connected to the first air pipe 111 through the air branch pipe 115.
, And the liquid pipe 112 via the liquid branch pipe 116, and compressed air and liquid are supplied from each of them.

FIG. 1 shows an example in which two lines of an outer peripheral channel 110a and an inner peripheral dew 110b are provided concentrically. The air branch pipe 115 and the liquid branch pipe 116 may be connected at least at one point in the circumferential direction. However, in order to uniformly distribute air or liquid to the flow path 110, the air branch pipe 115 and the liquid branch pipe 116 may be connected in the circumferential direction. It is good to provide a plurality of places in the.

The compressed air in the first air tube also pressurizes the back pressure chamber 108 at the same time, and the force for pushing up the sample holder 106 by the compressed air is periodically controlled so as to exceed the pressing force for the bellows chamber 104. Is done.

At the moment when the pushing force of the sample holder exceeds the pressing force of the bellows chamber, the sample holder 106 and the sample 1
07 is separated and the air-tightness of the back pressure chamber 108 held by the O-ring 114 is broken.
Injected toward. This air-fuel mixture becomes an air-liquid mist in which the liquid becomes fine mist by the function of the nozzle 109, and the back surface of the sample 107 is cooled by this air-liquid mist flow. The mist flow exhibits a large cooling capacity by covering the surface to be cooled with a thin liquid film, and further increases the amount of heat generated from the back surface of the sample 107 to remove latent heat while evaporating, so that the cooling effect is further enhanced.

During polishing, the supply pressure of the first air supplied to the back pressure chamber 108 is slightly smaller than the air pressure supplied to the bellows chamber 104 except for the mist spray timing, and the air supplied to the bellows chamber 104 only at the mist spray timing. It is desirable to be slightly greater than the pressure.

The mist spray timing can be arbitrarily set by temporally controlling the air pressure supplied to the back pressure chamber 108.

Similarly, the mist spraying time can be arbitrarily set by temporally controlling the air pressure supplied to the back pressure chamber 108.

Instead of periodically raising the pressure of the first air to push up the sample holding table 106, a constant pressure relief valve (not shown) is provided in the back pressure chamber 108 to be lower than the pressure of the bellows chamber 104 during mist spraying. Alternatively, a method in which the liquid is pressurized only at the time of cooling by applying a higher pressure than the relief valve is also possible. At this time, the structure is such that air is always released from the back pressure chamber 108 via the constant pressure relief valve.

In the present invention, since the mist is sprayed on the back surface of the sample, it is desirable to appropriately secure the interval (spray distance) between the cooling nozzle 109 and the sample 107. Although it depends on the spray volume and the spray pressure, the spray distance is desirably about 3 to 50 mm when the air pressure of the normally used back pressure chamber is used.

The liquid supplied through the liquid tube 112 is typically water, but a liquid having a lower boiling point than water, such as ethanol, is also preferable as long as it does not chemically react with the sample or adversely affect the sample. .

The arrangement of the flow channel 110 inside the sample holding table 106 can take various forms.

FIG. 2 is a schematic diagram showing an example of the arrangement of the flow path 110 and the cooling nozzle 109 inside the sample holding table.
(a) is a single row arranged concentrically with the outer periphery of the sample holder.
FIG. 2B shows a case where a plurality of rows are arranged, and FIG. 2C shows a case where a plurality of rows are arranged radially from the center.

The heat generated by polishing is not uniform over the entire surface of the sample, but is often distributed in the radial direction of the sample as shown in FIG.
FIG. 3 is a diagram schematically showing a heat generation state of a wafer sample.
(b) is a schematic diagram showing an example of the arrangement of flow paths for the heat generation of FIG. 3 (a).

As shown in FIG. 3A, when a high heat generation portion is known in advance on the back surface of the sample based on the temperature measurement during the test polishing, the supply state of the polishing liquid, the initial shape of the sample, and the like, as shown in FIG. If the arrangement of the nozzles 109 is determined so that more air-liquid mist for cooling is supplied to the high heat generating portion of the sample, the temperature of the sample is made uniform, and the cooling performance can be further improved.

The change in polishing conditions may change the heat generation distribution in the sample surface. For example, when the polishing material and polishing liquid are changed due to an improvement in operation, the types of samples to be polished are diversified, and the production speed is improved, the heat generation distribution changes. Alternatively, it may be necessary to adjust the cooling characteristics of the sample holder once manufactured.

In the polishing apparatus of the present invention, assuming an apparatus having a plurality of nozzles for gas-liquid mist for cooling, it is possible to adjust the distribution of the supply amount of gas-liquid mist to each line.

FIG. 6 is a schematic diagram showing a mechanism for adjusting the distribution of the supply amount of the gas-liquid mist. In the figure, the cooling nozzle 109 is divided into a series of an outer flow path 110a and a series of an inner flow path 110b. A pipe for supplying air to the outer peripheral channel 110a is provided with an outer air regulating valve 122a, and a pipe for supplying liquid is provided with an outer liquid regulating valve 123a. Similarly, a pipe for supplying air to the inner peripheral channel 110b is provided with an inner peripheral air adjusting valve 122b, and a pipe for supplying liquid is provided with an inner peripheral liquid adjusting valve 123b.

For example, when it is found that the outer periphery generates a large amount of heat, the outer periphery air regulating valve 122a and the outer periphery fluid regulating valve 1
23a may be opened and the inner peripheral air regulating valve 122b and the inner peripheral fluid regulating valve 123b may be half-opened or fully closed.

These regulating valves can be automatically opened and closed in conjunction with a temperature sensor for detecting the temperature on the back surface of the wafer.

[0037]

(Embodiment 1) A polishing apparatus shown in FIG. 1 was manufactured. The radius of the outer peripheral channel 110a is 85 mm, and the inner peripheral channel 11 is
The radius of Ob is 45 mm, and eight cooling nozzles 109 are provided on the outer periphery and four cooling nozzles are provided on the inner periphery. The test material has a diameter of 200.
LS on 0mm, 0.725mm thick silicon wafer
It is a wafer on which a circuit pattern simulating I is formed. Water was used as a cooling liquid.

The main polishing conditions were a polisher rotation speed of 30.
rpm, number of rotations of sample holding unit: 80 rpm, polishing time: 1
20 seconds, polishing liquid supply amount: 50 cc / min, back pressure chamber pressure: (when not spraying) 1.12 atm /
(At the time of spraying) 1.30 atm, bellows chamber pressure:
1.15 atm, mist spray timing (interval): 5
Seconds, mist spraying time: 0.5 seconds / time, cooling water supply: 4
00 cc / min, ambient temperature: 20.0 ° C., cooling water temperature: 20.0 ° C.

When the temperature at the center of the back surface of the silicon wafer was measured with a thermocouple, the average temperature during polishing was 35.5 ° C.
The highest temperature was 48.0 ° C.

When the same silicon wafer was polished by the conventional polishing apparatus shown in FIG. 5 under the same conditions, the temperature at the center of the rear surface of the silicon wafer was 58.5 during the polishing.
° C and the maximum temperature was 91.5 ° C.

From this, it was found that the polishing apparatus according to the present invention can reduce the temperature rise of the silicon wafer by about 40 ° C. at the maximum when polishing the silicon wafer as compared with the conventional polishing apparatus.

(Embodiment 2) An adjustment valve as shown in FIG. 6 was incorporated in the sample holding section 106 of the same polishing apparatus as in Embodiment 1. A silicon wafer similar to that used in Example 1 was prepared as a test material. Fully open all adjustment valves in advance,
A polishing test was performed.

The polishing conditions were as follows: polisher rotation speed: 40 rpm
m, rotation speed of sample holding unit: 100 rpm, polishing time: 12
0 second, polishing liquid supply amount: 40 cc / min, back pressure chamber pressure: (when not spraying) 1.12 atm /
(At the time of spraying) 1.30 atm, bellows chamber pressure:
1.15 atm, mist spray timing (interval): 5
Seconds, mist spraying time: 0.5 seconds / time, cooling water supply: 4
00 cc / min, ambient temperature: 20.0 ° C., cooling water temperature: 20.0 ° C.

0 m from the center in the radial direction on the back surface of the test material
m, 20mm, 40mm, 55mm, 65mm, 75m
A total of ten thermocouples were attached at positions of m, 80 mm, 85 mm, 90 mm, and 95 mm, and the temperature distribution in the wafer surface was measured.

In the first polishing, the average temperature in the range of a radius of 80 to 95 mm of the outer peripheral portion of the wafer is 60.5 ° C., the maximum temperature is 78 ° C., and the average temperature between the center and the radius of 75 mm is 45.
° C and the maximum temperature was 55 ° C, and it was confirmed that the temperature at the outer peripheral portion was extremely high.

Therefore, the opening degree (the number of rotations of the screw type adjusting valve) of the inner air adjusting valve 122b and the inner liquid adjusting valve 123b is reduced to 1/4, and the outer air adjusting valve 122a and the outer liquid adjusting valve 123a are reduced. The opening was kept fully open.

In the second polishing, the average temperature in the range of the radius of 80 to 95 mm at the outer peripheral portion of the wafer is 50.5 ° C., the maximum temperature is 66 ° C., and the average temperature between the center and the radius of 75 mm is 47.
° C and the maximum temperature was 63.5 ° C.

As described above, when a plurality of channels are provided,
It was found that the temperature distribution in the plane of the sample can be made more uniform by changing the spray distribution of the air-liquid mist for each part of the sample.

[0049]

According to the polishing apparatus of the present invention, it is possible to suppress a rise in the temperature of the material to be polished and perform polishing so that the temperature does not exceed the reliability assurance temperature. Further, if the supply distribution of the gas-liquid mist for cooling is changed according to the distribution of the calorific value in the sample surface, polishing can be performed while maintaining high flatness, and LS
It is possible to improve the quality yield of electronic products such as I.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a sample holder of a polishing apparatus according to the present invention, wherein FIG. 1 (a) is a longitudinal sectional view, and FIG. 1 (b) is FIG.
It is AA sectional drawing of.

FIG. 2 is a schematic diagram showing an example of the arrangement of flow paths inside a sample holder. FIG. 2 (a) shows a case where a single line is arranged concentrically with the outer periphery of the sample holder, and FIG. When placed, the same figure (c)
Is a case where a plurality of rows are arranged radially from the center.

3 is a diagram schematically showing a heat generation state of a wafer sample, and FIG. 3 (b) is a schematic diagram showing an example of arrangement of flow paths for heat generation in FIG. 3 (a).

FIG. 4 is a side view showing an outline of a conventional polishing apparatus for polishing a conventional semiconductor substrate.

FIG. 5 is a longitudinal sectional view showing a main part of a sample holding unit disclosed in Japanese Patent Application Laid-Open No. 9-19863.

FIG. 6 is a schematic view showing a mechanism for adjusting a supply distribution of a gas-liquid mist.

[Explanation of symbols]

 10: Polishing liquid 11: Polishing platen rotating shaft 12: Sample holding unit rotating shaft 101: Polisher 101a: Polishing platen 101b: Polishing cloth 102: Sample holding unit 103: Housing plate 104: Bellows chamber 105: Sample holding ring unit 106 : Sample holder 107: sample 108: back pressure chamber 109: cooling nozzle 110: flow path 110 a: outer circumference flow path 110 b: inner circumference flow path 111: first air pipe 112: liquid pipe 113: second air pipe 114: O-ring 115: air branch pipe 116: liquid branch pipe 121: polishing liquid supply nozzle 122a: outer peripheral air regulating valve 122b: inner peripheral air regulating valve 123a: outer peripheral fluid regulating valve 123b: inner peripheral fluid regulating valve

Claims (2)

[Claims] 1. A polishing apparatus comprising: a plate-like sample held by a rotating sample holding table; and a polisher having a polishing material attached to a rotating polishing platen disposed in parallel with the plate-like sample and rotating.
A polishing apparatus for polishing a flat sample while supplying a polishing liquid, wherein the sample holding table is provided with a nozzle for supplying a gas-liquid mist for cooling to the back surface of the flat sample. Polishing equipment. 2. A plurality of gas-liquid mist nozzle lines for cooling, and the distribution of gas-liquid mist supply to each line can be changed to adjust the cooling amount distribution on the back surface of the flat sample. The polishing apparatus according to claim 1, further comprising a regulating valve.