JP3223291B2 - Electrostatic chuck sample table - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck sample stage used in an apparatus for processing a sample such as a semiconductor device substrate.

[0002]

2. Description of the Related Art In an apparatus for performing a predetermined process on a semiconductor substrate, for example, a CVD apparatus, an etching apparatus, etc., an electrostatic chuck sample stage for holding the semiconductor substrate in a sample chamber is provided. The electrostatic chuck sample stage uses an electrostatic chuck method, in which a plate-shaped conductor whose outside is covered with an insulator on a thin film is fixed in the sample chamber, and the sample is placed on the surface of the insulator. The semiconductor substrate is brought into close contact, a predetermined DC voltage is applied between the conductor and the semiconductor substrate to generate an electrostatic force between the two, and the semiconductor substrate is attracted and held on the conductor by the electrostatic force. It has become.

FIG. 5 is a schematic sectional view of a conventional electrostatic chuck sample stage. In the figure, reference numeral 15 denotes a chamber bottom plate provided with an electrostatic chuck, and a base plate 16 made of an insulating material is placed on the chamber bottom plate 15, and on the base plate 16,
An electrostatic chuck 11 in which a conductor is covered with an insulating film is provided, on which a sample S is mounted. Inside the base plate 16, there is provided a cylindrical base hole 16b opening on the lower surface, and a plurality of holes 16a, 16a,... Penetrating the base hole 16b are formed on the upper surface of the base plate 16. . Holes 11a, 11a... Corresponding to holes 16a, 16a.
The chamber bottom plate 15 has a base hole 16b.
A hole 15a corresponding to the center of the hole is provided. The sample detaching mechanism 12 includes a flat base member 12b at the upper end of the shaft 12c.
And a plurality of lift pins 12a, 12
a… and the shaft 12c is
The base member 12b is connected to the hole 16a of the base plate 16 through the hole 15a.
, The lift pins 12a, 12a...
a ... is inserted.

Also, a hole between the shaft 12c and the chamber bottom plate 15 is provided.
A slide guide 17 is fitted in the gap between the slide guide 15a and the space 15a, and seals the inside of the chamber. An actuator 19 is connected to the lower end of the shaft 12c, and the sample detaching mechanism 12 moves in the vertical direction by driving the actuator 19. The shaft 12 extending from the lower surface of the chamber bottom plate 15 to the lowermost end of the shaft 12c
A bellows 18 is fitted around c and the shaft 12
The leakage of the seal of the chamber due to the movement of c is prevented. When the pressure in the chamber is reduced, the bellows 18 contracts.

[0005]

In the electrostatic chuck sample stage having such a structure, when the sample in the suction state is to be released, immediately after the application of the DC voltage is stopped and the electrostatic force is extinguished, the actuator 19 is stopped. The tip of the lift pins 12a, 12a,... Pushes up the sample S, and releases the sample S from the electrostatic chuck 11. Then, the sample detaching mechanism 12 is further raised, and lifts the sample S to the raised position shown in the figure. Even after the stop of the DC voltage, the electrostatic chuck 11 retains a charge for a certain period and retains the attraction force. Therefore, the actuator 19 applies a large detaching force to the sample detaching mechanism 12 to push up the sample S.
Immediately after the voltage application is stopped, if a releasing force is applied during a period when the sample S is still being attracted to the electrostatic chuck 11, an excessive force is applied to the sample S, and the sample S is moved to a predetermined position for transport to the next process. There is a problem in that a detachment error such as displacement, damage, or the like that deviates from the position occurs.

In order to prevent such a detachment mistake, after the detachment setting time, that is, the waiting time after stopping the application of the DC voltage, the suction force remaining on the electrostatic chuck is reduced, and then the sample detaching mechanism is started. 12, a method of detaching the sample S is performed. FIG. 6 is a graph showing a residual adsorption force and a desorption set time in various conventional samples. The vertical axis shows the residual adsorption force and the horizontal axis shows time. Although the residual adsorption force of all the samples decreases with time, the rate of the decrease differs depending on the sample. This depends on the characteristics of the sample, the processing temperature, the applied voltage, and other conditions, and the time until the residual suction force decreases to the limit suction force (limit separation force) F differs depending on the sample. Here, the limit suction force (limit separation force) F is a limit residual suction force (separation force) at which a separation error occurs in the sample S when a larger separation force is applied to the sample S.
That is.

[0007] As described above, since the time until the residual adsorption force is smaller than the limit adsorption force F differs depending on the sample, the separation setting time T common to many samples needs to be set sufficiently long. As shown in the figure, the samples A and _B have passed unnecessary waiting times t _A and t _B. In addition, a sample such as Sample C, which has a very low rate of decrease in residual adsorption force, has a residual adsorption force larger than the limit adsorption force F at the time of the above-mentioned separation setting time T, and a separation / transport error occurs. However, a longer period of time for setting the departure is required. As described above, in order to set the leaving setting time sufficiently long, an unnecessary waiting time is required, and there is a problem that the throughput is reduced.

[0008] Further, a method of applying a reverse voltage to a sample in order to increase the reduction rate of the residual adsorption force is known. FIG.
Is a graph showing the relationship between the time when a reverse voltage is applied to the samples A and D after the application of the DC voltage is stopped and the residual adsorption force. The vertical axis represents the residual adsorption force and the horizontal axis represents time, and zero on the horizontal axis is the time when the application of the reverse voltage is started. Samples A and D are samples in which the rate of decrease in residual adsorption force is significantly different, and as shown in the figure, the rate of decrease in residual adsorption force of sample A is higher than when no reverse voltage is applied. There is no period in which both A and D have a residual adsorbing force smaller than the limit adsorbing force F, and there is a problem that the set-off time of the samples A and D must be set for each.

The present invention has been made in view of such circumstances, and in the first invention, the separation stability is improved by applying a separation force to the separation means that does not cause a separation error, and the waiting time is improved. It is an object of the present invention to provide an unnecessary and high-throughput electrostatic chuck sample stage. Another object of the second invention is to provide an electrostatic chuck sample stage having a higher throughput by providing a detachment detecting means for detecting detachment of the sample.

[0010]

According to a first aspect of the present invention, there is provided an electrostatic chuck sample stage provided with detaching means for applying a detaching force to a suctioned sample by moving the sample in a detaching direction. In order to apply a detachment force smaller than the limit detachment force of the occurrence of a mistake to the sample, a pressure adjusting means for applying a tensile force in a direction opposite to the detachment force to the detachment means by pressurizing the detachment means is provided. .

An electrostatic chuck sample table according to a second aspect of the present invention is an electrostatic chuck sample table provided with release means for applying a release force to a suctioned sample in a direction of releasing the sample by movement.
Pressure applying means for applying a pulling force in a direction opposite to the detaching force to the sample by applying pressure to the detaching means so as to apply a detaching force smaller than a limit detaching force at which a detachment error occurs to the sample; Is provided with a detachment detecting means for detecting detachment of the sample depending on the position of.

[0012]

In the electrostatic chuck sample stage of the present invention, a tension force in a direction opposite to the release force is applied to the release means by adjusting the pressure, and a release force smaller than the limit release force is applied to the release means.
A detaching force can be applied to the sample without waiting for a decrease in the adsorbing force of the sample, and a sample detaching error does not occur. Further, since the detachment detecting means detects the detachment of the sample, the specimen can be immediately transferred to the next step after the detection.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic sectional view of an electrostatic chuck sample stage of the present invention. In the figure, reference numeral 5 denotes a chamber bottom plate provided with an electrostatic chuck. A base plate 6 made of an insulating material is mounted on the chamber bottom plate 5, and the electrostatic chuck 1 having a conductor covered with an insulating film is disposed on the base plate 6. The sample S is mounted thereon. Inside the base plate 6, there is provided a cylindrical base hole 6b opening on the lower surface, and a plurality of holes 6a, 6a,... Penetrating through the base hole 6b are formed on the upper surface of the base plate 6. . Holes 1a, 1a... Corresponding to the holes 6a, 6a... Are formed through the electrostatic chuck 1, and a hole 5a corresponding to the center of the base hole 6b is formed through the chamber bottom plate 5.

A hollow cylindrical housing 9 is provided on the lower surface of the chamber bottom plate 1, and a hole 9 a is formed in the bottom of the housing 9.
, 9b. The sample detaching mechanism 2 includes a flat base member 2b provided at an upper end and a lower end of a shaft 2c.
, A plurality of lift pins 2a, 2a... Protruding from the upper surface of the base member 2b, and a displacement measuring member 2e protruding from the lower surface of the pressing member 2d. The base member 2b has a hole 6a in the bottom plate 5, the base member 2b has a hole 6a in the base plate 6, the lift pins 2a, 2a ... have holes 1a, 1a ... in the electrostatic chuck 1, and the displacement measuring member 2e.
Pass through the hole 9a.

A slide guide 7 is fitted in a gap between the shaft 2c and the hole 5a of the chamber bottom plate 5 to seal the inside of the chamber. Around the shaft 2c, a double bellows 8, which is the pressure adjusting means, is mounted around the lower surface of the chamber bottom plate 5 and the upper surface of the pressing member 2d, and the shaft 2c and the pressing member 2d are housed. Part 9
It is designed to move within. The inner bellows 8a prevents the seal from leaking in the chamber due to the movement of the shaft 12c. When the inside of the chamber is in a reduced pressure state, the double bellows 8 is in a contracted state. Pressing member 2d
Has a hole 2f penetrating therethrough at a position corresponding to the outer bellows 8b, and a conduit connected to the hole 2f has air valves 3a, 3a.
b, 3c are provided. Air valve 3 connected to a compressed air source
The air is introduced into the outer bellows 8b through the hole 2f by a, and the air from the inside of the outer bellows 8b is discharged by the air valve 3c connected to the air valve 3b and the pressure regulating valve 3d opened to the atmosphere. Thereby, the double bellows 8 expands and contracts to move the sample detaching mechanism 2.

When the chamber is in a vacuum state, the air valve 3b,
When the air is introduced from the air valve 3a by closing the 3c and the internal pressure of the outer bellows 8b is adjusted to be higher than the atmospheric pressure, the double bellows 8, which has been in the contracted state, expands, and the sample detaching mechanism 2 applies the tensile force. And descend. Also outer bellows 8b
When the inside is in a compressed air state, the air valves 3b and 3c are closed to discharge air from the air valve 3c, and when the internal pressure of the outer bellows 8b is set to the atmospheric pressure, the double bellows 8 contracts and the sample detaching mechanism 2 becomes Ascending is given by the detaching force. When the inside of the outer bellows 8b is in a compressed air state, the air valves 3a, 3
When the internal pressure of the outer bellows 8b is finely adjusted by the air valve 3b and the pressure adjusting valve 3d with the c closed, the tensile force applied to the sample detaching mechanism 2 is adjusted to a constant force, and the sample detaching mechanism 2
Can apply a small detachment force to the sample. Further, the inner dimension of the storage portion 9 may be any size as long as the pressing member 2d can move within the movement range of the base member 2b within the base hole 6b.

Further, a displacement detecting optical sensor 4 as the detachment detecting means is provided with the displacement measuring member 2e interposed therebetween. The displacement detecting optical sensor 4 detects a predetermined displacement of the displacement measuring member 2e, that is, a predetermined displacement of the sample detaching mechanism 2.

A description will be given of a case in which, for example, a sample subjected to an etching process is detached from the electrostatic chuck sample stage having such a structure. FIG. 2 is a flowchart illustrating a procedure for removing and lifting a sample using the electrostatic chuck sample stage of the present invention. Description will be made based on this flowchart. First, air is introduced from the air valve 3c into the outer bellows 8b, the internal pressure of the outer bellows 8b is made higher than the atmospheric pressure, and the double bellows 8 is extended. Let
Are stopped at a lower position lower than the electrostatic chuck 1. The sample S is sucked and held on the electrostatic chuck 1 to perform an etching process. After the etching is completed, the application of the DC voltage is stopped (step S21).

Immediately after the application of the DC voltage is stopped, the air valve 3b
The internal pressure of the outer bellows 8b is minutely adjusted by the pressure adjusting valve 3d, the double bellows 8 is contracted, and the pulling force applied to the sample detaching mechanism 2 is adjusted. (Step S22). Since the force due to the spring constant of the double bellows 8 is also applied to the detaching force applied to the sample detaching mechanism 2, the pressure of the pressure regulating valve 3d is adjusted taking this into consideration. At this time, the detachment force is set to a force that does not cause a detachment mistake of the sample S.

Then, the separation of the sample S is determined by the displacement detecting optical sensor 4 (step S23). In this determination,
When the displacement measuring member 2e has risen a predetermined distance, that is, when the lift pins 2a, 2a... At this time, lift pin 2
.. stop at a separation detection position above the electrostatic chuck 1 by a predetermined distance, and the sample S separates from the electrostatic chuck 1.

Next, the outer bellows 8b is operated by the air valve 3c.
The internal pressure is set to the atmospheric pressure (step S24). When the inside of the chamber is vacuum and the internal pressure of the outer bellows 8b becomes atmospheric pressure, the double bellows 8 is further contracted, the sample detaching mechanism 2 rises, and the base member 2b comes into contact with the upper surface of the base hole 6b. Stop at the position you want. At this time, the tips of the lift pins 2a, 2a,... Stop at a raised position above the electrostatic chuck 1 by a predetermined distance, and the lifting of the sample S ends.

FIG. 3 is a graph showing the residual attraction force of various samples and the desorption start time using the electrostatic chuck of the present invention. The vertical axis indicates the residual adsorption force and the horizontal axis indicates time, and zero on the horizontal axis indicates the point in time when the sample separation mechanism 2 applies a separation force to the sample. When the residual adsorption forces of the samples A, B, and C reach the same value as the detachment force f smaller than the limit adsorption force F set in step S22 described above, the sample detachment mechanism 2 detaches each sample. . As described above, the sample can be separated from the electrostatic chuck at the times T _A , T _B , and T _C according to the residual suction force reduction rate of each sample without setting a wasteful waiting time.

FIG. 4 is a graph showing the residual attraction force when a reverse voltage is applied to the sample after the application of the DC voltage is stopped and the desorption start time using the electrostatic chuck of the present invention. is there. Zero on the horizontal axis is the time when the application of the reverse voltage is started and a detaching force is applied to the sample. There is no period in which both samples A and D, which have greatly different reduction rates of the residual adsorption force, have a residual adsorption force smaller than the limit adsorption force F, but a value smaller than the common limit adsorption force F for samples A and D. By setting the detachment force f of the time T _a , the time T _a ,
It can be allowed to withdrawal in T _B.

Next, as described above, the separation time of the sample S, that is, the time from the stop of the voltage application to the end of the separation (Step S22) was measured. Table 1 shows this result.
For each type of wafer, the average separation time on the electrostatic chuck sample stage of the present invention was measured and compared with the conventional separation setting time F.

[0025]

[Table 1]

As is clear from Table 1, when the sample is detached by using the electrostatic chuck of the present invention, one-fifth of the conventional one is used.
Withdrawal took about 1/10 of the time, indicating that the time required for withdrawal was reduced.

In the present embodiment, the separation detecting means is
Although an optical sensor is used, the invention is not limited to this, and any device that can detect displacement can be used.

[0028]

As described above, in the present invention, since the pressure adjusting means applies a detaching force to the sample such that a detachment error does not occur, the detachment stability is improved, the waiting time is not required, and the throughput is improved. . Further, since the detection means detects the detachment of the sample, the present invention has excellent effects such that the conveyance is performed quickly and the throughput is further improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electrostatic chuck sample stage of the present invention.

FIG. 2 is a flowchart illustrating a procedure for removing a sample using the electrostatic chuck sample stage of the present invention.

FIG. 3 is a graph showing the residual attraction force of various samples and the desorption start time using the electrostatic chuck of the present invention.

FIG. 4 is a graph showing the residual attraction force of various samples and the desorption start time using the electrostatic chuck of the present invention.

FIG. 5 is a schematic sectional view of a conventional electrostatic chuck sample stage.

FIG. 6 is a graph showing a residual adsorption force and a desorption set time in a conventional sample.

FIG. 7 is a graph showing a residual adsorption force and a desorption set time in a conventional sample.

[Explanation of symbols]

 Reference Signs List 1 electrostatic chuck 2 sample detaching mechanism 2a lift pin 2b base member 2c shaft 2d pressing member 2e displacement measuring member 3a, 3b, 3c air valve 3d pressure regulating valve 4 displacement detection optical sensor 5 chamber bottom plate 8 double bellows

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 B23Q 3/15 H01L 21/3065 H01L 21/68 H02N 13/00

Claims (2)

(57) [Claims] In an electrostatic chuck sample stage provided with a detaching means for applying a detaching force in a direction of detaching the adsorbed sample by moving the adsorbed sample, a detaching force smaller than a limit detaching force at which a detachment error occurs is applied to the sample. And a pressure adjusting means for applying a pulling force in a direction opposite to the detaching force to the detaching means by applying a pressure to the detaching means. 2. The electrostatic chuck sample stage according to claim 1, further comprising a detachment detecting means for detecting detachment of the sample according to a position of the detaching means.