JPH09283608A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detach a wafer without damaging it, by providing a through hole which supplies gas to a gap part with a specific depth on the clamping surface of an insulated substrate, and by projecting a lift pin to push and detach the wafer which is held on the wafer table when gas pressure which is detected by a detecting means provided in the through hole seaches a predetermined value. SOLUTION: An upper surface of an insulated board 2 is made to be a wafer table 5, an opening gap part 8 with 50∼200μm depth being comprised of a gap 8a having a concentric circle form and a gap 8b extending with a radiating form from the center are formed on the wafer table 5 and a through hole 9 to supply such gas as He and so on to the gap part 8 is provided. A pressure sensor 12 is provided as a detecting means to detect gas pressure change in the through hole 9 and a lift pin 7 is projected to push and detach a wafer 30 held on the wafer table 5 when the gas pressure reaches a predetermined value measured by the pressure sensor 12. This can detach the wafer 30 without damage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck used for holding a wafer such as a semiconductor wafer or a glass substrate in a manufacturing process of a semiconductor device, a liquid crystal substrate or the like.

[0002]

2. Description of the Related Art Conventionally, in the process of manufacturing a semiconductor device,
A jig for holding a semiconductor wafer with high precision is used in a film forming apparatus for forming a film on a semiconductor wafer, an etching apparatus for performing fine processing, and an exposure apparatus for performing electron beam exposure processing. The electrostatic chuck is used as.

FIG. 4 shows an electrostatic chuck of this type.
A disk-shaped insulating substrate 22 as shown in FIGS.
In some cases, the electrostatic electrode 23 is provided in the upper part of the inside, and the resistance heating element 24 is embedded in the lower part of the inside, and the upper surface of the insulating substrate 22 is used as the adsorption surface 25. Then, by energizing the semiconductor wafer 30 placed on the suction surface 25 and the electrostatic electrode 23, the insulating base material between the wafer 30 and the electrostatic electrode 23 acts as a dielectric layer 22a, The wafer 30 is attracted and held flat on the attracting surface 25 by the Coulomb force due to the dielectric polarization generated between the attracting surface 30 and the attracting surface 25 and the Johnson-Rahbek force due to a minute leakage current, and the resistance heating element 24 is energized to generate heat. As a result, the wafer 30 on the suction surface 25 is uniformly heated.

Further, a plurality of holes 26 are formed in the periphery of the insulating base 22 as a mechanism for removing the semiconductor wafer 30 which has undergone various process treatments from the suction surface 25, in the electrostatic chuck 21. In some cases, the lift pins 27 are projected from the holes 26 to lift and remove the semiconductor wafer 30 on the suction surface 25 (see Japanese Utility Model Publication No. 3-4037).

[0005]

However, as shown in FIG.
There is a problem that when the semiconductor wafer 30 that has been processed by using the electrostatic chuck 21 shown in (a) and (b) is to be removed, the wafer 30 is damaged by the lift pins 27.

That is, in order to remove the wafer 30 from the attracting surface 25, it is necessary to first turn off the energization to the electrostatic electrode 23 to remove the adsorbing force.
Even if F is set, the electric charge charged on the adsorption surface 25 does not disappear immediately, and thus the adsorption force remains. By lifting the semiconductor wafer 30 without knowing that the residual adsorption force remains, it is a hard and brittle material. Wafer 30 lift pin 2
It was damaged by 7.

Therefore, the wafer 30 may be removed by measuring the time required for the residual suction force to decay and adjusting the lift timing of the lift pins 27. Since it also varies depending on the type of carrier gas, processing temperature, high-frequency voltage, etc., it has not yet been possible to completely control the timing of the lift pins 27 under all process conditions.

Therefore, in the conventional electrostatic chuck, the wafer 3
There is still a risk that 0 will be damaged, and if the wafer 30 is damaged, in the automated manufacturing process of the semiconductor device, there is a problem that the wafer 30 sent next cannot be processed normally due to the broken pieces. there were.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrostatic chuck capable of removing a wafer which has been subjected to various kinds of process processing without damaging the wafer and notifying the operator or the like of the damage. Especially.

[0010]

In view of the above problems, therefore, the present invention provides an electrostatic electrode inside an insulating substrate, and uses the surface of the insulating substrate as an adsorption surface, and the adsorption surface has an opening depth. It has a through hole for supplying gas to the groove of 50 to 200 μm, and a detecting means for detecting a change in the gas pressure is provided in the through hole, and the insulating substrate can project from the suction surface. The electrostatic chuck is configured such that the lift pins are provided and the wafer held on the suction surface is pushed out by projecting the lift pins when the gas pressure by the detection means reaches a predetermined value.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

1A and 1B are views showing an electrostatic chuck 1 which is an example of an embodiment according to the present invention. FIG. 1A is a perspective view and FIG. 1B is a sectional view taken along line XX of FIG. The electrostatic electrode 3 is embedded in the upper part of the inside, and the resistance heating element 4 is embedded in the lower part of the inside, and the upper surface of the insulating substrate 2 is the adsorption surface 5. Further, the adsorption surface 5 is formed with a groove portion 8 including a concentric circular groove 8a and a groove 8b extending radially from the center, and a through hole for supplying a gas such as He to the groove portion 8 in the center. 9 is drilled.

As a material for forming the insulating substrate 2,
Alumina sinter, silicon nitride sinter, and aluminum nitride sinter can be used, and among these, it is particularly preferable that the aluminum nitride sinter has excellent plasma resistance and heat resistance.

Further, an introduction pipe 10 for introducing a gas such as He is continuously provided in the through hole 9, and a gas cylinder 14 and a flow rate control valve 13 for adjusting the flow rate of the gas are provided at the ends thereof. And a detecting means for detecting a change in the gas pressure supplied to the groove portion 8 of the adsorption surface 5 by measuring the pressure in the introduction pipe 10 in the branch pipe 11 branched from the introduction pipe 10. A pressure sensor 12 is provided as the pressure sensor 12, and the pressure detected by the pressure sensor 12 is transmitted to the control unit 18 as an electric signal.

Further, a plurality of holes 6 are formed in the periphery of the insulating substrate 2, and a driving mechanism (not shown) separately provided in the holes 6.
Therefore, a lift pin 7 that moves back and forth from the suction surface 5 is arranged, and the lift pin 7 is controlled by a controller 18 to control the lift timing.

With this electrostatic chuck 1, the semiconductor wafer 3
In order to hold 0, first, the semiconductor wafer 30 is attached to the suction surface 5.
Is placed, and an electric current is applied between the wafer 30 and the electrostatic electrode 3 so that the insulating base between the wafer 30 and the electrostatic electrode 3 acts as the dielectric layer 2a. The wafer 30 is attracted and held flat on the attracting surface 5 by the Coulomb force due to the dielectric polarization generated during the period and the Johnson-Rahbek force due to the minute leakage current. In addition, the introduction pipe 1 from the gas cylinder 14 is inserted into the groove 8 of the suction surface 5.
0 and the gas such as He having good heat transfer characteristics are supplied through the through holes 9 and the resistance heating element 4 is energized to generate heat to uniformly heat the wafer 30 on the adsorption surface 5. There is. It is preferable that the gas pressure supplied to the groove portion 8 is about 20 Torr because a high thermal uniformity of the wafer 30 can be obtained.

Next, a mechanism for removing the semiconductor wafer 30 that has undergone various process processes using the electrostatic chuck 1 according to the present invention will be described.

FIG. 2 is a flow chart showing the removing process of the semiconductor wafer 30 which has been processed.

First, the energization to the electrostatic electrode 3 and the supply of gas such as He are turned off, and the pressure in the groove 8 (≈introduction tube 1
The pressure within 0) is measured by the pressure sensor 12. That is,
When the energization to the electrostatic electrode 3 is turned off, the residual adsorption force is gradually attenuated, the gas supplied to the groove portion 8 flows out from the gap between the semiconductor wafer 30 and the adsorption surface 5, and the pressure in the groove portion 8 decreases. The pressure change is measured by the pressure sensor 12. In addition, since the electrostatic chuck 1 according to the present invention has the groove 8 formed on the attraction surface 5, the charge on the attraction surface 5 is small, and the responsiveness after releasing the chuck can be improved.

Then, the control unit 18 controls so that an infinite loop is formed without applying lift timing until the pressure in the groove 8 decreases to a predetermined pressure, and the pressure in the groove 8 is a predetermined value or less. Then, the lift pins 7 are projected from the suction surface 5 to push the wafer 30 off the suction surface 5.

For example, if the lift timing is set when the pressure in the groove 8 is less than 1/2 of the initial pressure of 20 Torr, that is, 10 Torr or less, almost no suction force remains. Therefore, even if the lift pins 7 are projected from the suction surface 5, the semiconductor wafer 30 can be removed without damaging the semiconductor wafer 30. However, regarding the pressure value for applying the lift timing, the wafer
It suffices to measure a limit value of the pressure in the groove portion 8 which does not cause the breakage, and set the lift timing within this limit value.

As described above, by detecting the absolute pressure in the groove portion 8 by the pressure sensor 12, the lift timing of the lift pin 7 can be easily controlled.

When the lift timing of the semiconductor wafer 30 needs to be advanced for the convenience of work, the time until the pressure in the groove 8 becomes zero when the semiconductor wafer 30 is lifted is measured. The presence or absence of damage to the wafer 30 can be detected by comparing with the time when the semiconductor wafer 30 is normally lifted.
That is, when the semiconductor wafer 30 is lifted normally, it takes some time for the pressure in the groove 8 to reach zero. However, if the semiconductor wafer 30 is damaged during the lift, the pressure in the groove 8 will be short. Since it becomes zero, it is possible to easily detect the presence or absence of damage to the wafer by comparing these times.

Although the lift timing of the lift pin 7 is controlled by the absolute pressure in the groove portion 8 in the above embodiment, the pressure in the chamber chamber and the pressure in the groove portion 8 are detected and the differential pressure between the two is detected. The lift timing of the lift pin 7 may be controlled by measuring
That is, when the lift timing is applied when the pressure difference between the pressure in the chamber chamber and the pressure in the groove portion 8 becomes substantially zero, the residual suction force generated between the wafer 30 and the suction surface 5 is substantially generated. Since it becomes zero, the wafer 30 can be removed without damaging it.

However, in order to detect the gas pressure in the groove portion 8 by the pressure sensor 12 and confirm whether or not the wafer 30 is damaged, the depth T of the groove portion 8 of the suction surface 5 is an important requirement.

That is, the depth T of the groove portion 8 of the suction surface 5 is 50 μm.
If the depth is less than m, even if the wafer 30 is damaged, the gas pressure in the groove portion 8 is gradually decreased, so that the wafer 30 is not damaged.
This is because it is not possible to detect the presence or absence of damage in the. However, if the depth T of the groove portion 8 is deeper than 200 μm, when the electrostatic chuck 1 is heated, thermal stress may be concentrated on the bottom corner portion of the groove portion 8 and cracks may occur, and the wafer 30 may be broken. The soaking property deteriorates.

Therefore, the depth T of the groove 8 is 50 to 20.
It is preferable to provide it in the range of 0 μm.

As for the sectional shape of the groove portion 8 formed on the suction surface 5, the side wall surface 15 forming the groove portion 8 as shown in FIG. 3 is formed in a tapered shape, and the side wall surface 15 and the bottom surface 16 are formed. It is preferable to form the corner portion 17 in a curved shape. With such a structure, it is possible to prevent the corner portion 17 from cracking due to thermal stress concentration. Desirably, when the width of the groove portion 8 is L and the angle of the side wall surface 15 is Z, those having a cross-sectional shape having the following relationship are preferable.

[Relational Expression] L> T, Z <60 ° The thermal stress concentration can be further suppressed by integrally forming the corner portion 17 and the bottom surface 16 into a curved surface.

Although the electrostatic chuck 1 used in the manufacturing process of the semiconductor device has been described in the embodiment of the present invention, the electrostatic chuck 1 is also used for adsorbing and holding the glass substrate and other articles constituting the liquid crystal substrate. It goes without saying that the electrostatic chuck 1 can also be used as the electrostatic chuck 1.

[0031]

EXAMPLE Here, FIG. 1 in which groove portions 8 having different depths T are provided
The electrostatic chuck 1 shown in 1 was prepared, and the semiconductor wafer 30 sucked and held was forcibly lifted by the lift pins 7, and the pressure change in the groove portion 8 when the semiconductor wafer 30 was damaged was measured.

The electrostatic chuck 1 used in this experiment has an outer diameter of 2
It is a disc having a thickness of 00 mm and a substrate thickness of 15 mm, and the width of the groove 8 formed on the suction surface 5 is 80 μm.

The pressure of He gas supplied to the groove portion 8 of the suction surface 5 is set to 20 torr and the lift pin 7 is used.
When the semiconductor wafer 30 was lifted normally, the time required for the gas pressure in the introduction tube 10 to reach zero was measured and found to be about 1.5 to 2.0 seconds.

The respective results are shown in Table 1.

[0035]

[Table 1]

As a result, in the samples A and B, since the depth T of the groove 8 is less than 50 μm, the time until the gas pressure in the introduction tube 10 becomes zero when the wafer 30 is forcibly damaged. It is found that the time of 1.2 to 1.8 sec is almost the same as the time when the semiconductor wafer 30 is normally lifted, and it is not possible to judge whether or not the wafer 30 is damaged.

On the other hand, in the samples C and D, the depth T of the groove 8 is set to 50 μm or more, so that the wafer 30
When the gas is forcibly damaged, the time until the gas pressure in the introduction tube 10 becomes zero is 0.4 sec or less, and the gas pressure immediately drops, so it is clear that the time is the time when the semiconductor wafer 30 is normally lifted. The presence or absence of damage to the wafer 30 can be detected.

From this, the groove portion 5 formed on the suction surface 5
It can be seen that the damage of the wafer 30 can be easily detected if the depth T of the wafer is set to 50 μm or more.

[0039]

As described above, according to the present invention, an electrostatic electrode is provided inside an insulating substrate, and the surface of the insulating substrate is used as a suction surface.
Has a through hole for supplying gas to the groove of 00 μm,
The through hole is provided with a detection means for detecting the change in the gas pressure, and the insulating substrate is provided with a lift pin projecting freely from the suction surface so that the gas pressure by the detection means becomes a predetermined value. Since the electrostatic chuck is constructed so that the lift pins are sometimes projected to push out the wafer existing on the suction surface, the wafer after various process processing can be removed from the suction surface without damage by the lift pins. In addition, the presence or absence of damage can be easily detected even if the wafer is forcibly removed and damaged.

[Brief description of drawings]

FIG. 1 is a view showing an electrostatic chuck according to the present invention;
(A) is a perspective view, (b) is the XX sectional drawing.

FIG. 2 is a flow chart showing a wafer removing process in the electrostatic chuck of the present invention.

FIG. 3 is an enlarged view showing a cross-sectional shape of a groove portion of the electrostatic chuck according to the present invention.

4A and 4B are views showing a conventional electrostatic chuck, in which FIG. 4A is a perspective view and FIG. 4B is a sectional view taken along line YY.

[Explanation of Codes] 1 ... Electrostatic chuck, 2 ... Insulating substrate, 3 ...
・ Electrostatic electrode, 4 ... Resistance heating element, 5 ... Adsorption surface,
6 ... Hole, 7 ... Pin, 8 ... Groove, 9 ...
..Through holes, 10 ... Introducing pipes, 11 ... Branch pipes, 12 ...
..Pressure sensor, 13 ... Flow control valve, 14 ... Gas cylinder

Claims (1)

[Claims] 1. A through hole for supplying a gas to a groove having a depth of 50 to 200 μm, which is provided with an electrostatic electrode inside the insulating substrate, and has a surface of the insulating substrate as an adsorption surface. And a detection means for detecting a change in the gas pressure is provided in the through hole, and the insulating substrate is provided with a lift pin projectable from the suction surface.
An electrostatic chuck configured such that when the gas pressure by the detection means reaches a predetermined value, the lift pins are projected to push out the wafer held on the suction surface.