JP2817585B2 - Sample removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of removing a sample and a sample holding apparatus used in the method, and more particularly to a method of forming a thin film or a dry etching by electrostatically adsorbing a sample holding portion in a semiconductor device manufacturing process. The present invention relates to a sample detaching method required when detaching a sample after performing a process, and a sample holding device used in the method.

[0002]

2. Description of the Related Art In the process of forming a thin film or in a dry etching process in a semiconductor manufacturing process, it is desirable to carry out a process in which a sample is securely brought into close contact with a sample stage and controlled at a predetermined temperature.

Conventionally, when a sample is mounted on a sample stage, a peripheral portion of the sample is fixed on the sample stage by pressing it using a ring-shaped holding plate or a claw-shaped holding jig provided on a mounting surface. Was. However, when such a mechanical mounting means is used, there is a problem that the degree of close contact between the sample and the sample stage is insufficient, and in order to solve this problem, in recent years, using an adsorption action by electrostatic force, A sample holding device for bringing a sample into close contact with the entire surface of a sample table has been developed and is becoming popular. However, the sample holding device using the electrostatic force has a problem that it is difficult to detach the sample after the treatment, and various detaching methods and detaching devices have been proposed as a countermeasure. For example, a method for irradiating the sample with plasma for detachment to eliminate the electrostatic force, a method for contacting the grounded sample transfer arm with the sample to eliminate the electrostatic force, and applying a voltage whose polarity is opposite to that at the time of adsorption. There are a method of applying electrostatic force to the sample to eliminate the electrostatic force, a method of forcibly removing the sample using a lift pin mechanism for lifting the sample, a method of combining these methods, and the like.

FIG. 6 is a cross-sectional view schematically showing a sample holding apparatus in which this kind of lift pin mechanism is incorporated. In the figure, reference numeral 41 denotes an insulating ring formed using alumina or the like. Aluminum lower electrode 4 is placed on insulating ring 41.
2 and R is connected to the lower electrode 42 through a conductive wire 43a.
The F power supply 43 is connected. A sample holder 44 is provided on the lower electrode 42, and the sample holder 44 is formed in such a manner that a conductor layer 44b is embedded in an insulator 44a made of, for example, ceramics. The conductor layer 44b is connected to a DC power supply 45 via a conductor 45a, and an insulating tube 42a is interposed in a portion of the lower electrode 42 through which the conductor 45a passes. A flow path 46 is formed in the sample holding unit 44, and an introduction pipe 46a and a discharge pipe 46b are connected to the flow path 46, and the coolant circulates through the flow path 46 from the introduction pipe 46a and the discharge pipe 46b. The sample holding unit 44 is cooled by discharging the sample from the sample holding unit 44. Further, a space 47 is provided in the sample holder 44.
A lift table 48b having a plurality of lift pins 48a is disposed in the space 47, and a driving device 48d is connected below the lift table 48b via an elevating shaft 48c. Sample holder 4 above space 47
4 is formed with an insertion hole 44d for a lift pin 48a, and when the driving device 48d is driven, the elevating shaft 48c rises so that the sample 50 placed on the sample holder 44 is pushed up by the lift pin 48a. Has become.

In order to fix the sample holder 44 and the lower electrode 42 on the insulating ring 41, a lower electrode pressing ring 49 made of ceramics such as alumina is used, and the lower surfaces of the flanges 49a, 49b and 49c are fixed. Sample holder 4
4 and the upper surface of the peripheral edge of the lower electrode 42 and the upper surface of the peripheral edge of the insulating ring 41 are joined and bolted (not shown).

When the sample 50 is adsorbed and held by using the sample holding apparatus having the above-described structure, the sample 50 is first placed on the sample holding section 44, and then the DC power supply 45 is turned on to turn the sample holding section 44 on. A DC voltage is applied to the conductor layer 44b, and the upper surface of the sample 50 is irradiated with plasma for a short time. Then, the sample holder 44 is positively or negatively charged, while the sample 50 is grounded via the plasma. As a result, an electric field is generated between the sample 50 and the sample holder 44. Therefore, the sample 50 is adsorbed and held on the surface of the sample holding unit 44 by the electrostatic force between the positive and negative charges. Sample 50
After the adsorption, the cooling liquid is circulated through the flow path 46, the RF power supply 43 is turned on, and processing steps such as film formation or etching are started.

When the sample 50 is detached from the sample holder 44 after the film formation or etching process, the DC power supply 45 and the RF power supply 43 are first turned off, and for example, the charge stored in the sample 50 is irradiated by plasma. Let me escape. Next, the drive unit 48d is operated to raise the elevating shaft 48c, the sample 50 is pushed up by the lift pin 48a, and the sample 50 is detached from the sample holder 44. Thereafter, the sample 50 is gripped using a sample transfer arm (not shown) and is carried out of the system.

[0008]

In the above-described method of detaching the sample, the electric charge still remains in the sample 50 immediately after the sample is grounded, and therefore, the attraction force of the sample holder 44 remains. This residual adsorption force decreases with the passage of time.
It differs depending on the applied voltage and the like.

Therefore, when the sample 50 is pushed up using the lift pins 48a in a state where the suction force remains, the sample 50 is not smoothly separated, and the sample 50 jumps on the lift pins 48a due to a shock at the time of separation. There has been a problem that a position shift occurs due to shaking and a trouble that the transfer arm cannot grip the sample 50 occurs. Further, when the residual suction force is large, the push-up force is concentrated on the contact portions of the sample 50 with the plurality of lift pins 48a, and there is a problem that damage may occur in the vicinity thereof. In addition, it is difficult to confirm the shortest time (hereinafter, referred to as a detachment point) at which the sample can be detached smoothly, and the sample 5
Since the departure point is different for each type of 0, it is necessary to set the push-up start timing in consideration of the safety factor. As a result, the throughput of the apparatus (the number of samples that can be processed within a certain time) decreases, and There was a problem that the efficiency was reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a push-up force is evenly applied to the entire surface of a sample to be separated, and the push-up force can be released at the moment of the separation. It is an object of the present invention to provide a sample detaching method capable of preventing troubles and damages and improving processing efficiency.

[0011]

According to the present invention, there is provided a method for releasing a sample, comprising the steps of: releasing a sample electrostatically adsorbed on a sample holding unit;
The sample is provided between the sample holding unit and the sample.
At a given pressure to apply a release force in the opposite direction to the holding part side
Introduce gas and monitor the flow rate of the gas,
By confirming the phenomenon of increase, detachment of the sample is confirmed.
It is characterized by recognition .

[0012]

[0013]

The gas supplied to the gas inlet is Ar, H
and a rare gas such as e. When using means for irradiating detached plasma to remove the charge accumulated in the sample, the gas supplied to the gas introduction unit leaks from a gap between the sample and the sample holding unit, and Ar gas is converted to He gas. Since it is easier to ionize and easily take charge from the sample,
It is more effective to use r gas.

[0014] According to the above-described method of detaching a sample , the sample can be retained.
Between the holding part and the sample, the sample holding part
Introduce gas at a given pressure to give a release force in the opposite direction
Therefore, after the adsorption force decreases, the gas
The sample can be detached from the sample holder.
During this separation, the flow rate of the gas suddenly increases.
Quickly and reliably
You can do that. As a result, lift
Can move to the next process such as
It will be able to obtain. Also, lift up before leaving point.
The sample is not damaged or misaligned.
This can prevent occurrence of this.

[0015]

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sample detaching method and a sample holding device used in the method according to the present invention will be described below with reference to the drawings. Note that components having the same functions as those of the conventional example are denoted by the same reference numerals. FIG. 1 is a cross-sectional view schematically showing a parallel plate type plasma etching apparatus provided with a sample holding device according to an embodiment. In the drawing, reference numeral 11 denotes a processing chamber. An upper electrode 12 having a gas introduction hole (not shown) is provided in a central portion of the processing chamber 11, and an RF power supply 15 is connected to the upper electrode 12. Upper electrode 1
Numeral 2 is fixed to the upper electrode holder 14 via an insulating ring 13 made of ceramic such as alumina.
Numeral 4 is slidably in contact with the inner peripheral surface of the upper wall 11a of the processing chamber 11, and is movable up and down by using a motor 14a. Further, a loading hole 16 and a discharging hole 17 for the sample 50 are formed on both side walls of the processing chamber 11, respectively.
a and 17a. A vacuum pump (not shown) is provided on the lower wall 11c of the processing chamber 11.
Is connected to the exhaust pipe 19.

On the other hand, the upper electrode 11
The sample holding unit 24 is disposed so as to face the sample holding unit 24.
A sample 50 is placed on the top. The sample holder 24 is provided around the conductor 24b by means of thermal spraying or the like.
Are formed, and the conductor 24b is formed.
Is connected to a DC power supply 45 via a conducting wire 45a.
In addition, a channel 46 is formed in the sample holding unit 24, and the channel 4
An inlet pipe 46a and an outlet pipe 46b are connected to 6 so that the cooling liquid circulates through the flow path 46 from the inlet pipe 46a and is discharged from the outlet pipe 46b so that the sample holder 24 is cooled. Has become. A space 47 is formed in the sample holding section 24, and a lift table 48b having a plurality of lift pins 48a is disposed in the space 47, and is driven below the lift table 48b via a lifting shaft 48c. The device 48d is connected. An insertion hole 44d for a lift pin 48a is formed in the sample holder 44 above the space 47. When the driving device 48d is driven, the elevating shaft 48c rises, and the sample 50 placed on the sample holder 24 is moved. Is pushed up by the lift pin 48a.

Further, a gas introduction section 21 is formed on the upper surface of the sample holding section 24. As shown in FIG. 2, the gas introduction section 21 is formed radially with a plurality of concentric grooves 21a. And a plurality of grooves 21b, and an insertion hole 44d is connected to these grooves 21a and 21b.
A gas introduction pipe 22a is connected below the space 27 through the lower electrode 42, and one end of the gas introduction pipe 22a is provided with a pressure control (control range of about 0 to 100 Torr) and a flow rate monitor (measurement range of 0 to 100 Torr). A device 22c and a valve 22d are connected, and a pressure gauge 22b is connected to an intermediate portion of the gas introduction pipe 22a. These valves 22
d, pressure control and flow rate monitoring device 22c, pressure gauge 22
b, the gas introduction pipe 22a, the space portion 47 and the insertion hole 44d constitute the gas supply means 22, and the valve 22
d, gas of a predetermined pressure is supplied to the gas introduction pipe 22a, the space 47, the insertion hole 4 through the pressure control and flow rate monitor 22c.
The gas is supplied to the gas introduction unit 21 through 4d.

As in the prior art, the sample holder 24 and the lower electrode 42 are fixed to the insulating ring 41 using a lower electrode pressing ring 49, and the insulating ring 41 is
Is fixed to the lower wall 11c. Then, the coolant is circulated through the channel 46 to set the sample 50 at a predetermined temperature, and the RF power supplies 15 and 43 are turned on to turn on the upper electrode 12 and the lower electrode 42.
By applying high frequency power to the sample, the reaction gas supplied from the gas inlet is turned into plasma, and the sample 50 is subjected to an etching process.

Using the apparatus thus constructed, the sample 5
When adsorbing and holding 0, the sample 50 is first placed on the sample holder 24, and then the DC power supply 45 is turned on to apply a DC voltage to the conductor 24b of the sample holder 24,
The upper surface of the sample 50 is irradiated with plasma for a short time. Then, the sample holder 24 is positively or negatively charged, while the sample 50 is grounded via the plasma. As a result, an electric field is generated between the sample 50 and the sample holder 24. For this reason, the sample 50 is reliably adsorbed and held on the surface of the sample holding unit 24 by the electrostatic force between the positive and negative charges.

When the sample 50 is detached from the sample holder 24 after the film formation or etching process, the DC power supply 45 is first turned off, and a gas such as Ar or He having a predetermined pressure is supplied through the gas supply means 22. The gas introduction part 2
1 to uniformly apply a push-up force to many places on the lower surface of the sample 50. Then, for example, by irradiating plasma,
The charge stored in the sample 50 is released. Then
When the electrostatic force gradually decreases and the residual adsorption force becomes smaller than the gas pressure, the sample 50 is moved to the sample holder 2.
Leave from 4. The time of the separation can be reliably confirmed by a sudden increase in the supply gas flow rate or a decrease in the gas pressure in the pressure control and flow rate monitor 22c. Thereafter, the drive unit 48d is operated to raise the elevating shaft 48c, lift the sample 50 by the lift pin 48a, and grip the sample 50 using a sample transfer arm (not shown).
Take it out of the system.

Using the apparatus of the embodiment, the conductor 24b
A case where the sample 50 is adsorbed on the sample holding unit 24 by applying a DC voltage of 400 V to the sample holding unit 24 and then separated is described. Table 1 shows the separation conditions.

[0023]

[Table 1]

FIGS. 3A and 3B are graphs showing the separation process when the method and apparatus according to the embodiment are used. FIG. 3A shows the residual voltage of the sample holder, FIG. 3B shows the flow rate of Ar, and FIG.
r pressure. As is clear from this graph,
When the application of the DC voltage to the conductor 24b is stopped and the Ar gas is supplied to the gas introduction unit 21, the gas flow rate is reduced to about 2 SCCM after 7 seconds, and the gas is reduced to the set pressure of 1 SCCM.
It is kept at 5 Torr. At this time, when the detached plasma is irradiated, the residual voltage in the sample holder 24 becomes 3 seconds after the irradiation.
It was confirmed that the residual adsorption force was weakened by decreasing from 8 V to 3 V, and at the same time, the Ar flow rate rapidly increased, and the sample 50 was detached from the sample holding unit 24. After withdrawal, sample 50
There was no occurrence of displacement, as well as damage to the device.

As is clear from the results, in the sample detaching method according to the embodiment, the sample holder 24 and the sample 50
In the meantime, a detaching force is applied to the sample 50 in the direction opposite to the sample holding unit 24 side.
Gas is introduced at a predetermined pressure to give
After the decrease, the gas is released from the sample holding unit 24 by the separating force of the gas.
The sample 50 can be detached. Hey when you leave
As the gas flow rate increases rapidly, the sample 50
Points can be caught quickly and reliably.
As a result, immediately after the separation, proceed to the next process such as lift-up
And the processing efficiency can be increased. Also
No lift up before leaving point
To prevent damage and displacement of the sample 50
Can be.

Further, since the departure point can be quickly confirmed by using the flow rate monitor device 22c in the gas supply means 22, it is possible to immediately proceed to the next step, and therefore, it is possible to increase the processing efficiency.

In this embodiment, the case where the present invention is applied to a parallel plate type plasma etching apparatus has been described. However, the present invention can be applied to another etching apparatus or a thin film forming apparatus.

In this embodiment, a means for irradiating desorbed plasma is used to release the electric charge accumulated in the sample 50. In another embodiment, the grounded sample transfer arm is brought into contact with the sample. For example, a method of causing the electrostatic force to disappear by applying the voltage to the sample, or a method of applying an opposite voltage to the sample to remove the electrostatic force may be used.

In this embodiment, Ar gas is supplied to the gas introduction section 21.
Although gas is supplied, He gas may be used in another embodiment. However, when using means for irradiating detached plasma to discharge the electric charge accumulated in the sample 50, as shown in FIG. 4, the Ar gas has a smaller residual voltage in the sample holder 24 and a lower gas pressure. The sample 50 can be released more smoothly by the pressure.

In the present embodiment, the sample holder 24 having the insulator layer 24a formed around the conductor 24b by means such as thermal spraying is used. In another embodiment, the conductor layer is provided in the insulator. You may use the sample holding part of an embedded mode.

FIGS. 5A and 5B schematically show a sample holding device according to another embodiment, wherein FIG. 5A is a sectional view of the sample holding device, and FIG. 5B is a plan view of a sample holding portion. . The sample holder 34 is formed by forming an insulator layer 34a around a conductor 34b by means of thermal spraying or the like, and a gas flow path 31a is formed radially in the sample holder 34.
One end of the gas flow path 31a is connected to the space 47, and a plurality of holes 31b are formed on the gas flow path 31a.
Is configured. Other configurations and methods of using the apparatus are the same as those in the above-described embodiment, and thus description thereof is omitted here.

As is clear from the above description, the method for removing a sample according to another embodiment uses the sample according to the above-described embodiment.
And the same effect as the method of withdrawing can be obtained.
Since the gas flow path 31a serves as a gas reservoir, it is easy to equalize the gas ejection pressure in each hole 31b, and it is possible to apply the push-up force more evenly and to detach the sample 50 smoothly. .

[0033]

As described above in detail, in the sample detaching method according to the present invention, the distance between the sample holder and the sample is reduced.
Then, a detaching force is applied to the sample in a direction opposite to the sample holding unit side.
Since gas is introduced at a predetermined pressure as much as possible, adsorption power is reduced.
After a short time, the gas is released from the sample holder by the detaching force of the gas.
The sample can be removed. At the time of this withdrawal
Since the flow rate of the gas increases rapidly,
Points can be caught quickly and reliably.
As a result, immediately after the separation, proceed to the next process such as lift-up
And the processing efficiency can be increased. Also
No lift up before leaving point
To prevent the sample from being damaged or displaced.
Can be.

[0034]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating parallel plate type plasma etching provided with a sample holding device according to the present invention.

FIG. 2 is a plan view of a sample holding unit according to the embodiment.

FIGS. 3A and 3B are graphs showing the departure process when the method and the apparatus according to the embodiment are used, wherein FIG. 3A shows the residual voltage of the sample holder, FIG. 3B shows the Ar flow rate, and FIG. Is shown.

FIG. 4 shows a case where A is applied to a gas introduction part when irradiation with detached plasma is performed.
It is the graph which showed the result of having measured the residual voltage of the sample holding part at the time of supplying r or He.

5A and 5B are diagrams schematically illustrating a sample holding device according to another embodiment, wherein FIG. 5A is a cross-sectional view of the sample holding device, and FIG. 5B is a plan view of a sample holding unit.

FIG. 6 is a cross-sectional view schematically showing a conventional sample holding device.

[Explanation of symbols]

 Reference Signs List 21 Gas introduction part 22 Gas supply means 24 Sample holding part 24a Insulator layer 24b Conductor 45 DC power supply 50 Sample

Claims (1)

(57) [Claims] In a sample detaching method for detaching a sample electrostatically adsorbed on a sample holding unit, the sample holding unit and a sample holding unit are provided.
Between the sample and the sample, in the opposite direction to the sample holder
Introduce a gas at a predetermined pressure to give a departure force, monitor the flow rate of the gas, and confirm that the flow rate increases rapidly
A method for removing a sample, comprising confirming the removal of the sample.