JPH06252253A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To prevent the generation of dropping, cracking, etc., of an object to be attracted, and enable a specimen to be released immediately after the attractive force is extinguished. CONSTITUTION:A specimen stand 1 wherein conductor 2 is covered with an insulating film 3 is arranged at the nearly central part on a cooling plate 12, and fixed to the cooling plate 12 by a specimen stand presser 11. A base member 5 is arranged in a space 22 formed in the cooling plate 12. Lift pins 4, 4,... disposed upright in the end portion of the base member 5 are inserted from the space 22 into holes 21, 21,... formed in the specimen stand 1. The base member 5 is retained by an upper side retaining rod 61, which is connected with a lower side retaining rod 62, via a spring 8. A retaining plate 25 formed at the lower end of the lower side retaining rod 62 is connected with the cooling plate 12 by using a bellows 24. The retaining plate 25 is connected with an elevating shaft 27 wherein a load cell 9 connected with a stepping motor 26 is arranged. The load cell 9 is connected with a control equipment 10 in which an amplifier 101, an operator 102 and a driver 103 are installed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck for, for example, a semiconductor manufacturing apparatus, which attracts and holds a sample on the surface of which a treatment such as film formation or etching is performed by electrostatic attraction.

[0002]

2. Description of the Related Art For example, electron cyclotron resonance (Ele
ctron Cyclotron Resonance)
A semiconductor manufacturing apparatus such as a CVD (Chemical Vapor Deposition) apparatus for forming a film of a desired substance on a semiconductor substrate by ECR plasma or a dry etching apparatus for forming a fine pattern on a semiconductor substrate is provided in a plasma generation chamber. The generated ECR plasma is guided to the sample chamber connected to the plasma generation chamber by the action of the divergent magnetic field, and it irradiates the semiconductor substrate held on the sample table arranged in the sample chamber, and the thin film on the substrate is irradiated. It is to be formed or etched. In these devices, an electrostatic chuck that utilizes an electrostatic adsorption action is used to adsorb and hold a semiconductor substrate on a sample table in a sample chamber.

As this electrostatic chuck, a sample stage having a flat plate-shaped conductor whose outer surface is covered with a thin film insulator is arranged in a sample chamber, and a semiconductor which is an object to be adsorbed is provided on the surface of the sample stage. A substrate is placed, and a predetermined DC voltage is applied to the conductor to generate an electrostatic attraction force between the conductor and the semiconductor substrate. This electrostatic attraction force attracts the semiconductor substrate onto the conductor. There is an electrostatic chuck configured to hold.

In such an electrostatic chuck, when removing the attracted object in the attracted state, the application of the DC voltage is interrupted to eliminate the electrostatic force, and then the attracted object is detached. ing. FIG. 3 is a schematic cross-sectional view showing a conventional electrostatic chuck, in which 12 is a cooling plate provided with a circulation path 14 for circulating cooling water. A space 22 is formed in the center of the cooling plate 12 in the thickness direction thereof, and a guide hole 23 is formed in the space 22 to reach the back surface of the cooling plate 12 by a guide 23. A sample table 1 on which a sample S such as a semiconductor substrate, which is an object to be adsorbed, is placed is arranged at approximately the center of the cooling plate 12, and the sample table 1 is provided with a cooling water in a circulation path 14 provided in the cooling plate 12. Is circulated to be cooled. The sample table 1 is configured by covering the surface of the conductor 2 with the insulating film 3, and the vertical cross section thereof has a convex shape. Further, holes 21, 21, ... For inserting lift pins 4, 4, ... For moving up and down the sample S are penetrated through the sample table 1, and the cooling plate 12 is communicated with the holes 21, 21 ,. A hole reaching the space portion 22 is formed.

Around the convex sample stage 1, a sample stage retainer 11 having holes of different diameters formed in the upper and lower portions is arranged in the center, and the holes have different diameters. It is designed to be slightly larger than the diameter of the upper stage and the diameter of the lower stage. Further, the pressing portion 11a protruding above the lower hole of the sample table holder 11 is made to face the receiving portion 1a which is lowered by one step in the peripheral edge of the upper surface of the sample table 1. And sample holder
11 is fixed to the cooling plate 12 by a fixing tool 13 such as a screw, and the fixing tool 13 is mounted on the sample table via the receiving section 1a of the sample table 1 and the pressing section 11a of the sample table holder 11 facing the receiving section 1a. 1 cooling plate
It sticks to 12.

On the other hand, a plate-shaped base member 5 is arranged in the space 22 of the cooling plate 12, and the sample table 1 is provided at the edge of the base member 5.
Of the lift pins 4, 4 for vertically moving the sample S by being inserted into the holes 21, 21 ,. The base member 5 is supported by a support rod 6 inserted into a guide 23 provided on the cooling plate 12. A support plate 25 is fixed to the lower end of the support rod 6, and the support plate 25 and the cooling plate 12 are sealed by an expandable bellows 24 for maintaining a depressurized state in a sample chamber (not shown). It has been stopped. And the support plate 25 has lift pins 4, 4 ...
Is connected to an actuator 36 that moves up and down.

In order to separate the sample S with such an apparatus, it is necessary to interrupt the application of the DC voltage to the conductor 2 to neutralize the charge between the sample S and the conductor 2 and to eliminate the adsorption force. After a lapse of time, the actuator 36 was operated to raise the support rod 6, and the sample S was detached from the sample table 1 by the lift pins 4, 4.

[0008]

By the way, in such a conventional electrostatic chuck, the time required for the attraction force to disappear is not constant depending on the characteristics of the sample, the processing temperature, the applied voltage, etc. When the actuator is operated while remaining and the sample is removed from the sample table,
Since the sample may fall from the lift pin or may be misaligned from the predetermined position to cause the sample to be unloaded from the sample chamber, and the lift pin may break the sample, the time required for the suction force to disappear is the most necessary. Based on long time,
It is necessary to set it by multiplying it by a safety factor, which lowers the throughput indicating the number of processed samples per unit time, and further lowers the efficiency of the semiconductor manufacturing apparatus. The present invention has been made in view of such circumstances, and its purpose is to apply a weak force in a direction in which a sample is detached before the adsorption force disappears, thereby dropping and breaking the sample. Another object of the present invention is to provide an electrostatic chuck capable of releasing a sample immediately after the attraction force disappears, without causing the phenomenon.

[0009]

In an electrostatic chuck according to the present invention, an attractive force is generated by a DC voltage applied between a conductor coated with an insulating film and an object to be attracted, and the object to be attracted is generated. In an electrostatic chuck that is configured to adsorb an adsorbate and has a detaching unit that detaches the adsorbate from the conductor, a direction in which the adsorbate detaches from the conductor by using elastic force. A detachment force applying means for applying a force weaker than the attraction force and a means for detecting a force applied to the object to be attracted, and the object to be attracted to the conductor immediately after the attraction force disappears. It is characterized in that it is made to leave from.

[0010]

In the electrostatic chuck of the present invention, the attracted object that is attracted by the electrostatic attraction force generated by applying the DC voltage between the conductor coated with the insulating film and the attracted object is converted into the DC voltage. In case of detaching from the conductor after stopping the application of a force, a force weaker than the attracting force is applied to the attractant through the detaching means in the direction in which the attractant is detached from the conductor by the detaching force applying means utilizing elastic force. Since it is applied to the object, it is possible to apply a weak force to the object to be adsorbed without causing conveyance error or breakage of the object to be adsorbed, and to release the object to be adsorbed immediately after the adsorption force disappears. You can Further, since the means for detecting the force applied to the object to be adsorbed is provided, the force applied to the object to be adsorbed can be accurately detected, and the separation of the object to be adsorbed is sensed, and the object to be adsorbed subsequently Items can be transported to a predetermined position.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a schematic sectional view showing an electrostatic chuck of the present invention. In the figure, reference numeral 12 is a cooling plate provided with a circulation passage 14 for circulating cooling water. A space 22 is formed in the cooling plate 12 at the center in the thickness direction.
A guide hole reaching the back surface of the cooling plate 12 is formed by the guide 23. A sample table 1 on which a sample S such as a semiconductor substrate, which is an object to be adsorbed, is placed is arranged at approximately the center of the cooling plate 12, and the sample table 1 is provided with a cooling water in a circulation path 14 provided in the cooling plate 12. Is circulated to be cooled. Sample table 1
Is formed by covering the surface of the conductor 2 with the insulating film 3, and the vertical cross-section thereof is convex. Further, holes for inserting the lift pins 4, 4 ...
21,21 ... are penetrated, and the sample table 1 is attached to the cooling plate 12.
Are formed so as to reach the space 22.

Around the convex sample stage 1, a sample stage retainer 11 having holes of different diameters formed in the upper and lower portions is arranged in the center, and each of the holes has a diameter of the sample stage. It is designed to be slightly larger than the diameter of the upper stage and the diameter of the lower stage. Further, the pressing portion 11a protruding above the lower hole of the sample table holder 11 is made to face the receiving portion 1a which is lowered by one step in the peripheral edge of the upper surface of the sample table 1. And sample holder
11 is fixed to the cooling plate 12 by a fixing tool 13 such as a screw, and the fixing tool 13 is mounted on the sample table via the receiving section 1a of the sample table 1 and the pressing section 11a of the sample table holder 11 facing the receiving section 1a. 1 cooling plate
It sticks to 12.

On the other hand, a plate-shaped base member 5 is arranged in the space 22 of the cooling plate 12, and the sample table 1 is provided at the edge of the base member 5.
Of the lift pins 4, 4 for vertically moving the sample S by being inserted into the holes 21, 21 ,. The base member 5 is supported by an upper support rod 61 inserted into a guide 23 provided on the cooling plate 12, and the upper support rod 61 uses an elastic force to weaken the adsorption force and scratch the sample. Via a spring 8 which is a detachment force imparting means for imparting a weak force to the sample S
It is connected to the lower support rod 62.

A support plate 25 is arranged at the lower end of the lower support rod 62, and the support plate 25 and the cooling plate 12 are connected to a sample chamber (not shown).
It is sealed by an expandable bellows 24 for maintaining the reduced pressure inside. The support plate 25 is a stepping motor.
It is connected to an elevating shaft 27 connected to 26, and a strain gauge type load cell 9 which is a detector for detecting the pushing force by the stepping motor 26 is arranged on the elevating shaft 27.

On the other hand, the output of the load cell 9 is input to the amplifier 101 of the control device 10, and the amplified output of the amplifier 101 is the arithmetic unit 10
Entered in 2. The calculator 102 outputs the control signal of the stepping motor 26 to the driver 103 according to the result of comparison between the input value and a predetermined value given or the presence or absence of a ridge to be detected. The stepping motor 26 is powered according to the input from the device 102.

FIG. 2 is a partial schematic view for explaining the separation of the sample and the subsequent push-up by the apparatus of the present invention. Point A is the lowered position of the lift pin 4 and point B is the sample S completely separated from the sample table 1. The position and point C are the upper limit position of the lift pin 4. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Immediately after the power supply to the conductor 2 of the sample table 1 is stopped, the computing unit 102 of the control device 10 causes the driver 103 to drive the stepping motor 26 to raise the lift pin 4 at the point A to a predetermined position. This predetermined position is a position corresponding to the amount of lift of the stepping motor 26 required for the lift pin 4 to reach point B when the suction force disappears.
At this time, since the sample S is attracted to the sample table 1 by the residual attraction force, the elastic force of the spring 8 receives an upward force via the lift pin 4, but this force is a weak force as described above. Therefore, the sample S is not released until the adsorption force disappears, and the lift pin 4 does not cause a flaw on the sample S, and the sample S continues to receive the upward force.

On the other hand, when the remaining suction force disappears, the sample S is simultaneously detached from the sample table 1 by the elastic force of the spring 8 and moves to the point B. As a result, the strain that should be detected by the load cell 9 is not detected, so the control device
10 judges that the sample S has come off, and the stepping motor 26
Is driven to push up the sample S to point C.

Next, the result of a sample detachment test conducted by the apparatus of the present invention will be described. A silicon wafer weighing 23 g and a diameter of 6 inches was used as the sample, and the spring was 100 g when the lift pin contracted 2 mm after the contact with the wafer, considering the weight of the sample stand and the suction force due to the reduced pressure. A stainless steel product having a spring constant to which force is applied upward was used.
A voltage of 400 V is applied to the sample table to adsorb the wafer, this state is maintained for 1 minute, then application is stopped, and immediately the stepping motor 26 is operated for the amount corresponding to the point B of the sample S. Then, the detachment time until the sample S moved to the point B was measured.

As a result, the minimum withdrawal time is 10
The maximum time was 60 seconds, and the average time was 25 seconds. Under the same conditions, in the conventional apparatus, the separation was started 90 seconds after the application was stopped in consideration of safety, but the apparatus of the present invention shortened the average by 65 seconds compared to this case.

[0020]

As described above in detail, in the electrostatic chuck of the present invention, the sample can be removed immediately after the attraction force disappears without causing the sample to drop or be broken. The present invention has excellent effects such as improved reliability and higher efficiency of semiconductor manufacturing equipment.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an electrostatic chuck of the present invention.

FIG. 2 is a partial schematic diagram for explaining separation and push-up of a sample by the device of the present invention.

FIG. 3 is a schematic cross-sectional view showing a conventional electrostatic chuck.

[Explanation of symbols]

 1 sample table 2 conductor 3 insulator 4 lift pin 5 horizontal 6 support rod 8 spring 9 load cell 10 controller

Claims (1)

[Claims] 1. A direct current voltage applied between a conductor coated with an insulating film and an object to be adsorbed is used to generate an adsorbing force to adsorb the object to be adsorbed. In an electrostatic chuck having a detaching means for detaching from the conductor, a detaching force imparting means for imparting a force weaker than the attracting force to the attracted object in a direction of detaching from the conductor by utilizing elastic force, An electrostatic chuck comprising means for detecting a force applied to the object to be attracted, and the object to be attracted is separated from the conductor immediately after the attraction force disappears.