JPH09139417A - Method and device for plasma treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attenuate the electrostatic attraction force between a sample and a sample stand, to confirm the separation of the sample from the sample stand, and to quickly and safely carry the process-finished sample. SOLUTION: A vacuum gauge is used to give a decision whether or not a wafer 85 and a sample stand 6 which is given after finish of process of a sample are separated. First, while a process is being conducted, inert gas is stored in a tank 81, and the pressure P1 of the tank 81 is measured by a vacuum manometer 82. The pressure Pj of the tank 81 is monitored at all times by the vacuum manometer 82 while an electrostatic attraction removing treatment is being conducted, and the separation of the wafer 85 and the sample stand 68 is judged by comparing the pressure P1 and Pj. When the holding strength of electrostatic attraction is attenuated, as the pressure Pj becomes small, and the separation of the wafer and the sample stand 68 can be confirmed. Accordingly, the process-finished wafer can be conveyed quickly and safely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus, and particularly to a plasma processing method suitable for confirming static elimination of plasma processing using electrostatic attraction and holding and for statically eliminating a sample such as a semiconductor element by the plasma. And the device.

[0002]

2. Description of the Related Art Conventionally, as an apparatus using electrostatic attraction and holding, a means for detecting a voltage applied to an electrode is provided as described in, for example, JP-A-62-54637, and the value of the voltage is detected. By detecting the attachment / detachment state of the object to be processed, it is possible to detect an abnormal state such as falling or non-adhesion of the object to be processed,
There are some that have improved reliability.

[0003]

In a semiconductor manufacturing process for submicron using plasma, in order to reduce foreign matters and the like, an object other than the wafer to be processed, such as a wafer, is held on the sample table. It is necessary to hold the wafer on the sample table and process it without arranging an object such as the wafer retainer.

Further, in order to protect the wafer from the heat of the plasma, it is necessary to cool the wafer by flowing a cooling gas between the wafer and the sample table to cause heat exchange between the wafer and the sample table.

For this reason, an etching apparatus using plasma, for example, takes the form of holding the wafer on the sample stage by removing the wafer retainer as described above by using the electrostatic attraction holding as in the above-mentioned conventional technique. However, since an object such as a wafer retainer for holding the wafer is not arranged, it is necessary to have an electrostatic adsorption holding force that can sufficiently withstand the pressure of the cooling gas for heat exchange during the process.
After the process is finished, the electrostatic adsorption holding force is attenuated,
Next, electrostatic attraction release processing was required so that the wafer can be immediately transferred for replacement with the wafer to be held. If this electrostatic adsorption release process is insufficient or if re-adsorption holding occurs due to the extra electrostatic adsorption release process, the wafer is exchanged while it is still held on the sample table. There was a possibility that normal wafer transfer could not be performed.

An object of the present invention is to provide a plasma processing method and apparatus capable of promptly and safely carrying a sample after processing.

[0007]

The above object is to provide a vacuum chamber in which a processing gas is supplied and which is depressurized to a predetermined pressure, a means for converting the processing gas in the vacuum chamber into a plasma, and the vacuum chamber. Sample stage, means for electrostatically holding the sample placed on the sample stage by electrostatic attraction, means for supplying heat transfer gas to the back surface of the sample attracted and held on the sample stage, the sample stage and the sample And a means for confirming the separation of Further, in a plasma processing method in which an electrostatic attraction voltage is applied to the sample stage to electrostatically attract and hold the sample placed on the sample stage, and the sample is treated with plasma, the attraction force between the sample stage and the sample is measured. Therefore, it is achieved by confirming the separation between the sample table and the sample during the electrostatic adsorption release process.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION During execution of electrostatic adsorption release processing, an inert gas is stored in a space between a sample stage and a sample and a constant flow rate of the inert gas is flown, or pressure is applied in a state where the inert gas is stored. Is constantly measured, or the inert gas is stored in the space between the sample stage and the sample during the electrostatic adsorption release process, and the flow rate of the inert gas is controlled so that the pressure in the space becomes constant. Perform and always measure the flow rate of the inert gas. The measurement value obtained as a result is compared with the set value by the operator to determine whether the sample stage and the sample are detached.By this, the electrostatic adsorption holding force sufficient for transporting the sample is attenuated and Since the sample table and the sample are not held again due to the adsorption release process, the sample after the process process can be transported promptly and safely.

An embodiment of the present invention will be described below with reference to FIGS.
This will be described below. FIG. 1 shows an embodiment of the plasma processing apparatus. FIG. 2 is a diagram showing details of the plasma generation unit and the sample table in FIG. The present embodiment is an example in which a microwave and a magnetic field are used as a means for generating plasma. 6
1 is a magnetron that generates microwaves, 62 is a rectangular waveguide that propagates microwaves, 63 is a circular rectangular conversion waveguide, 64 is a cylindrical cavity portion, 641 is a top plate of the cylindrical cavity portion 64, and 65 is a magnetic field. , 66 is a microwave transparent window (for example, a quartz flat plate), 67 is a vacuum container,
Reference numeral 68 is a sample stage on which a wafer as a sample is placed, 69 is a drive mechanism for moving the sample stage up and down, 610 is plasma processing, for example, a high frequency power source for applying a high frequency bias voltage to the sample stage during etching, and 611 is processing. A shower plate for introducing a gas, for example, an etching gas into the vacuum container 67, a variable valve 612 for adjusting the pressure in the vacuum container 67, and a turbo molecular pump 613 for depressurizing the vacuum container 67 to a vacuum. , 614 is a vacuum pump of rough quotation, 616 is an electrostatic attraction power supply for electrostatically attracting a wafer placed on a sample stage, 81 is an inertness necessary for cooling the wafer by forming a space by placing the wafer. A tank capable of accumulating gas, a vacuum gauge 82 for measuring the pressure in the tank 81, and a gas flow meter 83 for supplying an inert gas to the tank 81. 84 through the gas flow meter 83 8
It is a gas introduction path for supplying an inert gas to the first tank.

A lower container 31 is attached to the lower portion of the buffer chamber 3. The lower container 31 is provided with a sample table 68 corresponding to the opening of the buffer chamber 3. Lower container 3
1 has a variable valve 612 in the middle, and the lower container 3
A turbo molecular pump 613 is provided at one end. The turbo molecular pump 613 is a rough reference vacuum pump 6
14 are connected.

A drive mechanism 69 is provided on the sample table 68,
The upper part of the sample table can be moved up and down. A high frequency power source 610 is connected to the sample stage 68, and a high frequency bias voltage can be applied to the sample stage 68.

A cylindrical vacuum container 67 is attached to the upper portion of the buffer chamber 3, and a flat microwave transmitting window 66 is airtightly attached to the upper opening of the vacuum container 67.
A plasma generation chamber is formed by the vacuum container 67 and the microwave transmission window 66. A cylindrical wall 642 configured to have substantially the same diameter as the vacuum container 67 is provided on the microwave transmission window 66 so as to be electrically connected to the vacuum container 67.
A top plate 641 having a circular opening in the center is provided in the upper opening of 42 so as to be electrically connected to the cylindrical wall 642.
A cylindrical cavity portion 64 surrounded by the microwave transmission window 66, the cylindrical wall 642, and the top plate 641 is provided. A circular rectangular conversion waveguide 63 is electrically connected to the circular opening in the center of the top plate 641, and the circular rectangular conversion waveguide 63 is electrically connected to a waveguide 62 and a magnetron 61 sequentially. It is connected and provided.

As shown in FIG. 2, a shower plate 611 having a large number of gas outlets 111 is provided on the lower surface of the microwave transmitting window 66 with a slight gap between the microwave transmitting window 66 and the shower plate 611. A gas introduction path 112 is provided in the gap between the microwave transmission window 66 and the shower plate 611.
Is connected.

The buffer chamber 3 is provided with a ring gate 15 which is a cylindrical partition valve for partitioning a processing chamber 6 from a passage which is a sample transfer space in the buffer chamber 3. The ring gate 15 is formed to have the same or substantially the same diameter as the inner diameter of the vacuum container 67, is incorporated from below the buffer chamber 3, and is formed by two air cylinders (not shown) symmetrically arranged with respect to the central axis of the ring gate 15. It is driven vertically.

A solenoid coil 65 is provided on the outer peripheral portions of the cylindrical hollow portion 64 and the vacuum container 67. The solenoid coil 65 includes solenoid coils 652 and 653 wound around the cylindrical cavity 64 and the outer periphery of the vacuum container 67.
And a solenoid coil 65 arranged on the top plate 641 of the cylindrical hollow portion 64 and having a small inner diameter and a large number of turns in the circumferential direction.
And 1. The solenoid coil 651 is used for main magnetic flux, and the solenoid coils 652 and 653 are used for controlling magnetic force lines. Further, a yoke 654 is provided around the solenoid coils 651, 652 and 653 so as to surround these solenoid coils. The inner upper end portion of the yoke 654 corresponding to the solenoid coil 651 is concentric with the axial center of the cylindrical hollow portion 64 and the vacuum container 67, and is bent downward toward the cylindrical hollow portion 64.

As shown in FIG. 2, the inner surface of the vacuum container 67 is made of quartz to prevent metal contamination from the vacuum container 67.
A cylindrical insulator cover 671 formed of a plasma resistant material such as ceramic is installed. Further, inside the vacuum container 67, a ground electrode 672, which is a member of ground potential, is arranged near the sample table 68, which is an electrode. The ground electrode 672 is electrically connected to the buffer chamber 3 that is at the ground potential, and is directed toward the inside of the vacuum container 67.
It is attached by providing a groove portion between and. The ground electrode 672 serves to establish electrical continuity between the plasma 615 and the vacuum container 67 electrically insulated by the insulator cover 672. The insulator cover 671 is held in the groove formed by the inner wall surface of the vacuum container 67 and the ground electrode 672.

In the apparatus configured as described above, in order to generate plasma in the vacuum container 67, first, the inside of the vacuum container 67 is depressurized by the turbo molecular pump 613 and the vacuum pump 614. When processing the sample, the process gas is introduced from the gas introduction path 112 into the microwave transmission window 6
6 and the shower plate 611 and introduced into the vacuum container 67 from the gas outlet 111 provided in the shower plate 611 (step a in FIG. 3). The internal pressure of the vacuum container 67 is adjusted by the variable valve 612,
A microwave that is a microwave current having a set current value is emitted from the magnetron 61 (step b in FIG. 3). In this case, the microwave of 2.45 GHz oscillated from the magnetron 61 has a rectangular waveguide 62 and a circular rectangular conversion waveguide 63.
Is introduced into the cylindrical hollow portion 64 via. In this case, a rectangular TE10 mode microwave is propagated in the waveguide 62, converted into a circular TE11 mode microwave by the circular rectangular conversion waveguide 63, and guided to the cylindrical cavity portion 64.
The microwave introduced into the cylindrical cavity portion 64 is guided into the vacuum container 67 via the microwave transmission window 66 and the shower plate 611. On the other hand, a magnetic field in the axial direction of the vacuum container 67 is formed inside the vacuum container 67 by the solenoid coil 65 provided around the vacuum container 67. Due to the action of the microwave introduced into the vacuum chamber 67 and the magnetic field of the solenoid coil 65, the electrons in the plasma receive the Lorentz force from the magnetic field and make a turning motion. When the period of the swirling motion and the frequency of the microwaves are substantially equal to each other, the electrons efficiently receive energy from the microwaves, and the electron cyclotron resonance phenomenon (Electron Cyc
lotron Resonance, hereinafter abbreviated as "ECR". ) Produces a dense plasma 615. In this apparatus, an equal magnetic field surface (hereinafter abbreviated as “ECR surface”) satisfying the ECR condition is present inside the vacuum container 67. In this case, the strength of the magnetic field on the ECR plane is 875.
Gauss. As a result, a high density plasma 615 is generated in the vacuum container 67.

After the plasma is generated, the electrostatic attraction power supply 6
A DC voltage for adsorbing the wafer to the sample table 68 is output from 16 (step c in FIG. 3). In the electric circuit configured between the ground electrode 672, the electrostatic attraction power supply 616 and the sample table 68 via the plasma 615, the sample table 68 is used.
Since the wafer and the wafer itself have a capacitive component, the DC voltage output from the electrostatic attraction power supply 616 is
And the wafer are charged, so that the wafer is attracted to the sample table 68.

After the wafer is adsorbed on the sample stage 68, an inert gas is introduced into the tank formed by the wafer and the sample stage 68 for the purpose of preventing heat input by the plasma (step d in FIG. 3), and then the high frequency power source 610. The high-frequency bias voltage of the set voltage is output (step e in FIG. 3), and the process processing is started.

After that, when the process processing is completed, the supply of the cooling gas supplied to the back surface of the wafer is stopped (step f in FIG. 3), and the electrostatically adsorbed wafer is removed from the sample table 68 by the electrostatic adsorption release processing. After confirming the removal (step g in FIG. 3), the supply of high frequency power to the sample stage is continuously stopped (step h in FIG. 3), and the power supply to the magnetron 61 that oscillates microwaves is stopped (FIG. 3). Step i). After that, the supply of the process gas is stopped (step j in FIG. 3), and the wafer is unloaded for replacement with the next wafer.

Here, the pressure vacuum gauge 82 or the gas flow meter 83 is used to judge whether or not the wafer and the sample table 68 have been separated.
This is performed using

The pressure of the inert gas stored in the tank 81 formed by the wafer and the sample stage during the process is not lowered unless the electrostatic adsorption holding force is attenuated. That is,
Only when the electrostatic adsorption holding force is attenuated during the electrostatic adsorption releasing process, the pressure is reduced. Further, when the flow rate of the inert gas is controlled in order to keep the pressure of the space stored in the tank 81 formed by the wafer and the sample table constant, when the electrostatic adsorption holding force is attenuated, the pressure is reduced. The flow rate of the inert gas is increased in order to maintain the retention.

During the process, an inert gas is stored in a tank 81 formed by the wafer and the sample table for cooling the wafer, and the pressure P1 in the tank 81 is measured by using a pressure vacuum gauge 82. During the electrostatic adsorption release process, the pressure gauge 8
2, the pressure Pj of the tank 81 is constantly monitored, and the pressure P1
And Pj are compared, it is determined that the wafer and the sample table 68 can be separated. If the electrostatic adsorption holding force is attenuated, the pressure Pj is reduced, so that it is possible to confirm the separation between the wafer and the sample table 68, for example, by the following equation.

When P1-Pj> Px, the wafer and sample stage 6
It is judged that 8 and 8 have been able to leave. Here, Px is a value set by the operator according to the type of wafer, the conditions of process processing, etc., and a plurality of Px can be set under the above conditions.

Even when the inert gas is supplied at a constant flow rate during the electrostatic adsorption canceling process, the decrease in pressure due to the decrease in electrostatic adsorption holding force is larger than the increase in pressure due to the supply of inert gas. If the inert gas flow rate is set so that
Similar confirmations can be made.

Further, during the process processing, an inert gas is stored in the tank 81 formed by the wafer and the sample table for cooling the wafer, and the pressure of the tank 81 becomes constant during the electrostatic adsorption releasing process. Thus, the flow rate of the inert gas is controlled.
At this time, it is determined that the wafer and the sample stage 68 can be separated by measuring the sum Qj of the flow rates of the inert gas for a certain period of time. If the electrostatic adsorption holding force decays, the pressure will decrease,
Since the flow rate of the inert gas increases in order to maintain a constant pressure, it is possible to confirm the separation between the wafer and the sample table 68, for example, by the following formula.

When Qj> Qx, it is determined that the wafer and the sample table 68 can be separated. Where Qx is the type of wafer,
Indicates the value set by the operator according to the process processing conditions. Further, when it is confirmed that the wafer and the sample table 68 are detached, the electrostatic attraction release process is stopped even during execution,
It is possible to prevent the wafer and the sample table 68 from being re-held by the extra electrostatic attraction release processing and to shorten the electrostatic attraction release processing. Further, when the wafer and the sample table 68 cannot be separated from each other in the electrostatic attraction release process for some reason, an error timer is set to stop the replacement of the next wafer and give a warning to the operator. The wafer will not be damaged due to falling or falling.

[0028]

According to the present invention, the electrostatic attraction force between the sample and the sample stage can be attenuated and the separation between the sample and the sample stage can be confirmed, so that the sample can be transported after the process treatment is completed. The effect is that it can be performed promptly and safely.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a vacuum processing apparatus equipped with a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing details of a plasma generation unit and a sample stage unit of the apparatus of FIG.

3 is a time chart diagram showing operating steps of the apparatus of FIG. 1. FIG.

[Explanation of symbols]

61 ... Magnetron, 62 ... Waveguide, 63 ... Circular rectangular conversion waveguide, 64 ... Cylindrical cavity part, 65 ... Solenoid coil,
66 ... Microwave transmission window, 67 ... Vacuum container, 68 ... Sample stand, 610 ... High frequency power supply, 611 ... Shower plate,
613 ... Turbo molecular pump, 615 ... High density plasma,
616 ... Electrostatic adsorption power source, 81 ... Cooling gas storage tank,
82 ... Pressure vacuum gauge, 83 ... Gas flow meter, 84 ... Cooling gas introduction path, 85 ... Sample (wafer).

Front Page Continuation (72) Inventor Naoyuki Tamura, Higashi-Toyoi 794, Higashi-Toyoi, Shimomatsu, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi Ltd. (72) Hideyuki Yamamoto 794, Higashi-Toyoi, Shimomatsu, Yamaguchi Prefecture Hitachi, Ltd. In the Kasado Plant (72) Inventor Hiroyoshi Hirano 794 Higashi-Toyoi, Higashi-Tomoi, Yamaguchi Prefecture Stock company Hitachi Ltd.In the Kasado Plant (72) Inventor Masamichi Sakaguchi 794, Toyoi, Higashi-Toyo, Hitachi Kasato Engineering Co., Ltd. In the company

Claims (13)

[Claims] 1. A plasma processing method in which plasma is generated in a vacuum chamber, and an electrostatic attraction voltage is applied to the sample stage to electrostatically attract and hold a sample placed on the sample stage, and the sample is treated with the plasma. 2. The plasma processing method according to claim 1, wherein the detachment of the sample stage from the sample can be confirmed during the electrostatic adsorption cancellation process by measuring the attraction force between the sample stage and the sample. 2. The plasma processing method according to claim 1, wherein a space for storing an inert pressure for cooling the sample during plasma processing can be used as an adsorption force between the sample stage and the sample. . 3. The inert gas stored in the space between the sample stage and the sample according to claim 2, wherein a cooling gas used for cooling the sample during plasma processing can be used. Plasma treatment method. 4. The method according to claim 1, wherein the separation of the sample table and the sample is confirmed by storing an inert gas in a space between the sample table and the sample while holding the sample by electrostatic adsorption. A plasma processing method, which is performed by measuring the pressure in the space during processing. 5. The method according to claim 1, wherein the separation of the sample table and the sample is confirmed by flowing a constant flow rate of an inert gas into the space between the sample table and the sample during the electrostatic adsorption releasing process. The plasma processing method is performed by measuring the pressure in the space at that time. 6. The method according to claim 1, wherein the separation of the sample table and the sample is confirmed so that the pressure in the space between the sample table and the sample becomes constant during the electrostatic adsorption canceling process. A plasma processing method, which is performed by controlling a flow rate of an active gas and measuring a flow rate of the inert gas. 7. The operator according to any one of claims 4 to 6, wherein a condition for determining whether or not the sample stage and the sample are separated from each other is determined by an operator depending on a type of sample, an apparatus state during plasma processing, and the like. A plasma processing method characterized in that a plurality of them can be set by 8. The electrostatic chuck release according to claim 1, wherein when the separation of the sample table and the sample is confirmed during execution of the electrostatic chuck release processing, the electrostatic chuck release processing is immediately stopped to release the electrostatic chuck. A plasma processing method characterized in that the processing can be shortened. 9. The plasma according to claim 8, wherein the electrostatic adsorption release process is immediately stopped so that re-holding of the sample stage and the sample due to the extra electrostatic adsorption release process does not occur. Processing method. 10. The plasma processing method according to claim 8, wherein the shortening of the electrostatic adsorption releasing treatment reduces damage to the sample due to the electrostatic adsorption releasing treatment. 11. The function according to claim 1, wherein when the separation of the sample table and the sample cannot be confirmed, the fact is reported to the operator and the operator is asked whether to start the next process. A plasma processing apparatus comprising: 12. The plasma processing apparatus according to claim 11, further comprising a function of stopping unloading of the sample when the separation of the sample from the sample cannot be confirmed. 13. A vacuum chamber which is supplied with a processing gas and is depressurized to a predetermined pressure, a means for converting the processing gas in the vacuum chamber into plasma, a sample stage provided in the vacuum chamber, and the sample stage. Means for electrostatically holding the sample placed on the sample table, means for supplying a heat transfer gas to the back surface of the sample held on the sample table by suction, and measuring the attraction force between the sample table and the sample. A plasma processing apparatus comprising: the sample stage and means for confirming separation of the sample during the electrostatic adsorption release process.