JP2001035698A - Plasma generation method and plasma processing apparatus - Google Patents

Abstract

(57) [PROBLEMS] To prevent degassing from a cryopanel when a plasma discharge occurs in a plasma processing apparatus such as a sputtering apparatus that exhausts a vacuum chamber with a cryopump. SOLUTION: In a state where the exhaust conductance between the vacuum chamber and the cryopump is increased, a gas necessary for generating plasma discharge is introduced into the vacuum chamber, and the degree of vacuum in the vacuum chamber is reduced to generate plasma discharge. . Thereafter, the exhaust conductance between the vacuum chamber and the cryopump is reduced while the degree of vacuum in the vacuum chamber is high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for generating a plasma discharge in a plasma processing apparatus evacuated by a cryopump, and more particularly to a method for generating a plasma discharge in a sputtering apparatus.

[0002]

2. Description of the Related Art In order to generate a plasma discharge in a plasma processing apparatus such as a sputtering apparatus, it is necessary to introduce a certain amount or more of gas for contributing to the plasma discharge into the plasma processing apparatus.

[0003]

However, in order to reduce the influence of residual gas in the plasma processing apparatus, an apparatus that exhausts the inside of the plasma processing apparatus with an oil-free cryopump requires a large amount of gas in the plasma processing apparatus. Is introduced, the introduced room-temperature gas is adsorbed on the surface of the cryogenic panel (about 10 K) of the cryopump. The adsorbed gas raises the temperature of the cryopanel and vaporizes the gas adsorbed on the surface of the cryopanel, thereby deteriorating the degree of vacuum of the plasma processing apparatus.

On the other hand, the present inventors have studied the mechanism of plasma discharge generation. As a result, if a certain amount or more of gas is present at the time of plasma discharge, plasma discharge can be generated. After that, it was found that stable plasma discharge was maintained even when the gas amount was reduced, and the present invention was completed.

That is, the present invention relates to a method for generating a plasma discharge while preventing degassing from a cryopanel of a cryopump in a plasma processing apparatus such as a sputtering apparatus for evacuating a vacuum chamber by a cryopump, and a method for using the method. The purpose of the present invention is to provide a plasma processing apparatus that performs

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for generating plasma in a plasma processing apparatus for evacuating the inside of a vacuum chamber by a cryopump. A first gas introduction step of flowing a first gas into the vacuum chamber so that the first gas flows into the vacuum chamber; and a second gas flowing into the vacuum chamber so that the degree of vacuum in the vacuum chamber becomes a discharge vacuum degree at which plasma discharge occurs. After flowing, a second gas introduction step of shutting off the second gas, and a discharge step of generating a plasma discharge in the vacuum chamber after the degree of vacuum in the vacuum chamber reaches the degree of discharge vacuum, Further, before the second gas introducing step, an exhaust conductance limiting step for increasing the exhaust conductance between the vacuum chamber and the cryopump, and after the discharging step, A plasma generating method characterized by comprising an exhaust conductance relaxation step of reducing the inductance. By starting the plasma discharge using such a method, even if the gas required for generating the plasma discharge is introduced into the vacuum chamber, the temperature rise of the cryopanel of the cryopump can be suppressed. Degassing from the gas can be suppressed. As a result,
For example, when the present invention is applied to a sputtering apparatus, it is possible to improve the film quality of a thin film formed in a vacuum chamber and to stabilize the film forming rate, thereby improving the production yield. In the case where a plurality of films are continuously formed using a film forming apparatus having a plurality of electrodes in the same vacuum chamber,
Since almost no degassing occurs when plasma is generated in each film forming step, it is possible to improve the film quality of the formed thin film and to stabilize the film forming speed.

In the second gas introducing step, the step of shutting off the second gas after introducing the second gas is repeated at least twice, and the step of changing the degree of vacuum in the vacuum chamber in a stepwise manner is performed. Preferably, it is a gas introduction step.
By gradually changing the degree of vacuum in this way, the second gas can be introduced while detecting the degree of vacuum in the vacuum chamber. For this reason, the degree of vacuum of the vacuum chamber can be accurately controlled to the degree of vacuum required for plasma discharge, and it is possible to prevent the degree of vacuum of the vacuum chamber from being reduced more than necessary.

[0008] The stepwise second gas introduction step is preferably a step of sequentially opening and closing at least two or more valves arranged in parallel in the second gas introduction path to introduce the second gas. . This is because the life of each valve can be extended by using a plurality of valves.

It is preferable that the exhaust conductance limiting step is a step of increasing the exhaust conductance after the stable vacuum degree becomes substantially constant.

It is preferable that the evacuation conductance relaxation step is performed after the degree of vacuum in the vacuum chamber reaches the degree of discharge vacuum and further returns to the degree of vacuum before the introduction of the second gas.

It is preferable that the difference between the temperature of the cryopanel of the cryopump before the exhaust conductance limiting step and the temperature of the cryopanel after the exhaust conductance relaxation step is within 2 degrees. By setting the temperature change of the cryopanel to 2K or less, degassing from the cryopanel can be suppressed to a level that causes little problem.

The above-mentioned stable vacuum degree is 1 to 9 × 10 ⁻³ Torr.
r is preferred. This is for maintaining stable plasma discharge.

The discharge vacuum degree is 1 to 5 × 10 ^-2 Torr.
r is preferred. This is for easily generating a plasma discharge.

Preferably, the exhaust conductance limiting step and the exhaust conductance relaxing step are performed by opening and closing an orifice valve or a main valve provided between the vacuum chamber and the cryopump.

Preferably, the second gas introducing step is a step of opening a valve provided in the second gas introducing path for 0.1 to 0.7 seconds.

It is preferable that the stepwise second gas introduction step is a step of sequentially opening at least two or more valves arranged in parallel in the second gas introduction path for a maximum of 0.3 seconds each.

Preferably, the plasma processing apparatus is a sputtering apparatus. In particular, in the sputtering apparatus, the outgassing from the cryopanel greatly affects the quality of the formed thin film.

The present invention also provides a vacuum chamber for generating plasma, a gas introduction pipe for introducing gas into the vacuum chamber, and a vacuum chamber connected to the vacuum chamber via an orifice valve and / or a main valve. A cryopump for evacuating the inside of the plasma processing apparatus, wherein the gas introduction pipe supplies a first gas at a flow rate required to stabilize the plasma, a first gas introduction pipe, and the plasma A second gas introduction pipe for supplying a second gas at a flow rate required to generate the gas, and the second gas introduction pipe includes a plurality of valves provided in parallel with the pipe. It is also a processing device. The second gas introduction pipe is provided with a plurality of valves provided in parallel to the pipe, and each valve is sequentially opened and closed to introduce the second gas, thereby extending the life of each valve. This is because it is possible to suppress the deterioration of.

Preferably, the plasma processing apparatus is a sputtering apparatus.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 First Embodiment A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of a plasma discharge process according to the first embodiment of the present invention. In the figure, the operation of the instantaneous introduction gas cutoff valve, the operation of the power supply, the degree of vacuum of the chamber, and the operation of the orifice valve are shown in order from the top. The horizontal axis is time. 20 is a flow rate of Ar required for plasma discharge.
This is the operation of the instantaneous gas shutoff valve that introduces gas.
A pulse-up portion indicates a state where the valve is open, and other portions indicate a closed state. Reference numeral 21 denotes the operation of the power supply. The upward portion indicates a state where the power supply is turned on, and the other portions indicate a state where the power supply is turned off. Reference numeral 22 denotes a degree of vacuum, and the lower the level, the lower the vacuum. Reference numeral 24 denotes the operation of the orifice valve. The upper part is an opening degree setting 1 with small conductance (conductance: 30 l / sec), and the lower part is an opening degree setting 2 with large conductance (conductance: 3).
80 l / sec). The diameter of the orifice valve is
12 inches.

FIG. 3 is a schematic diagram of a magnetron sputtering apparatus used in the method according to the present embodiment. In the magnetron sputtering apparatus shown in FIG. 3, a flat plate target 2 and a substrate 1 on which a sputtered film is formed are arranged substantially in parallel in a chamber 8. A magnet 3 is provided on the back surface of the flat target 2, and a magnetic field 4 is formed. Around the flat target 2, an earth shield 5 for preventing discharge in parts other than the flat target 2 is provided.
The electrode 10 connected to the power supply 11 is provided below the power supply 11. Ar gas is introduced into the chamber 8 through a mass flow controller 6 for measuring a flow rate and a valve 7 for controlling a flow rate. The fixed valve 12 and the gas introduction cutoff valve 13 are provided to introduce a large amount of Ar gas only when plasma discharge occurs. The chamber 8 is evacuated to a high vacuum by a cryopump 9, and a main valve 14 and an orifice valve 15 for adjusting the exhaust amount are provided between the chamber 8 and the cryopump 9. Here, as described above, the orifice valve 15 can select and set the opening degree setting 1 having a small conductance and the opening degree setting 2 having a large conductance.

FIG. 1 shows a method according to this embodiment.
3 and the sputtering apparatus of FIG. 3 will be described. In this method, first, with the substrate 1 set in the chamber 8, for example, 10
Evacuate to a high vacuum of ^-6 Torr. In this state, the orifice valve 15 is in the standard position, that is, the opening degree setting 1.
(A position where the exhaust conductance is small).

Next, 80 sccm / min. Ar gas at a flow rate of? When the flow rate of Ar is stabilized and the degree of vacuum in the chamber 8 is stabilized at about 5 × 10 ⁻³ Torr (26 in FIG. 1), the orifice valve 15 is set to the opening degree setting 2 (a position where the exhaust conductance is large).

Next, a state where the degree of vacuum is stabilized (2 in FIG. 1)
7), the Ar gas instantaneous introduction gas shutoff valve 13 is set to 0.4
Open for about 0.7 seconds to introduce Ar gas into the chamber 8. In FIG. 1, a portion 20 in a pulse-like manner in the upper state is a state in which the Ar gas instantaneous introduction gas shutoff valve 13 is opened. As a result, as shown at 22 in FIG. 1, after the degree of vacuum suddenly decreases, for example, about 4 × 10 ⁻² To
Stabilizes at rr. As described above, by setting the degree of vacuum of the chamber 8 to about 1 to 5 × 10 ⁻² Torr, plasma discharge can be generated.

Next, in a state where the degree of vacuum in the chamber 8 is substantially stabilized (28 in FIG. 1), the power supply 11 is turned on and the electrode 1 is turned on.
A predetermined voltage is applied to 0. In such a state, a magnetic field and an electric field orthogonal thereto are generated in the chamber 8, and the Ar gas is discharged to be in a plasma discharge state. In the plasma discharge state, since the instantaneous introduction gas shut-off valve 13 is already closed, the degree of vacuum of the chamber 8 gradually shifts to high vacuum, and approaches the degree of vacuum before the instantaneous introduction gas shut-off valve 13 is opened.
As described above, even if the degree of vacuum is increased, the Ar gas once in the plasma discharge state by causing the plasma discharge can maintain the discharge state as it is.

Next, in a state where the degree of vacuum in the chamber 8 becomes substantially the same as that before opening the instantaneous introduction gas shut-off valve 13 and is stable (29 in FIG. 1), the orifice valve 15 is moved to the position of the opening degree setting 1. Return to As a result, the degree of vacuum stabilizes at about 4 × 10 ⁻² Torr while maintaining stable plasma discharge. In such a plasma discharge state, a high-density Ar plasma confined in the magnetic field 4 is generated, and the target 2 is sputtered by the Ar ions in the plasma colliding with the target 2, and the opposing substrate 1 is provided. To form a thin film 16.

As described above, in order to generate plasma by discharging Ar gas, a predetermined voltage is applied while a larger amount of Ar gas is supplied into the chamber 8 than in a state where plasma is stably discharged. However, by performing plasma discharge using the process according to the present embodiment, it is possible to prevent a large amount of Ar gas from being adsorbed on the cryopanel of the cryopump 9 even if a large amount of Ar is introduced. That is, in the process according to the present embodiment, when a large amount of Ar gas is introduced, the orifice valve 14 between the chamber 8 and the cryopump 9 is set to the position of the opening degree setting 2 where the exhaust conductance is large. Limiting the arrival of Ar gas to the cryopump 9,
Adsorption of Ar gas to the cryopanel can be reduced. As a result, the temperature rise of the cryopanel during the generation of the plasma discharge can be suppressed to about 1K, and the outgassing from the cryopanel due to the temperature rise of the cryopanel can be suppressed. Degassing from the cryopanel does not pose a problem if the temperature rise of the cryopanel is suppressed to about 2K or less.

In this embodiment, the conductance between the chamber 8 and the cryopump 9 is adjusted by using the orifice valve 15, but it is also possible to adjust the conductance by opening and closing the main valve 14. In this case,
It is necessary to set the opening / closing speed of the main valve 14 faster than the standard speed.

Embodiment 2 Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram of the plasma discharge process according to the first embodiment of the present invention. In the figure, the operation of the instantaneous introduction gas shut-off valve and the degree of vacuum of the chamber are shown in order from the top. The operation of the power supply and the operation of the orifice valve are the same as the process of the first embodiment shown in FIG. The horizontal axis is time. As in the first embodiment, the magnetron sputtering apparatus shown in FIG. 3 was used as the magnetron sputtering apparatus for generating plasma.

The plasma discharge method according to the present embodiment is obtained by changing the method of introducing Ar gas in the process of the first embodiment. That is, in the first embodiment, the instantaneous introduction gas shutoff valve 13 is opened for 0.4 to 0.7 seconds to introduce a large amount of Ar gas, but in the present embodiment, the valve is divided into several small steps. And Ar gas is introduced.

In FIG. 2, reference numeral 20 denotes a state of the instantaneous introduction gas shut-off valve 13. The upper part represents the open state of the valve, and the other parts represent the closed state.
The time for opening the valve is within 0.3 seconds each time.
Numeral 22 denotes the degree of vacuum of the chamber 8, and the portion indicated by 30 is enlarged in the vertical direction and indicated by 31 to 36.

As is apparent from FIG. 2, in this embodiment, the instantaneous introduction gas shut-off valve 13 is divided into several portions and opened in small increments to introduce Ar gas. As shown in the enlarged view of FIG.
As a result, by detecting the degree of vacuum in the chamber 8 and changing the number of times the instantaneous introduction gas shutoff valve 13 is opened,
The degree of vacuum of the chamber 8 can be accurately controlled to the degree of vacuum necessary for plasma discharge, and it is possible to prevent the degree of vacuum of the chamber 8 from being reduced more than necessary. Therefore, the Ar gas is not introduced into the cryopump 9 more than necessary, so that the adsorption of Ar to the cryopanel of the cryopump 9 can be minimized, and the temperature rise of the cryopanel can be suppressed.

FIG. 4 is a schematic diagram of a magnetron sputtering apparatus used in the second embodiment. This magnetron sputtering apparatus is obtained by improving the instantaneous gas shut-off valve 13 of the magnetron sputtering apparatus shown in FIG. In FIG. 3, one instantaneous introduction gas shutoff valve 1 is provided.
3 are arranged in parallel with the Ar gas introduction pipe as shown by 13a, 13b and the like in the figure.
In the method according to the second embodiment, the instantaneous introduction gas shut-off valve 13 needs to be opened and closed a plurality of times in order to generate one plasma discharge. In some cases. Therefore, as shown in FIG.
3a and the like are provided, for example, 13a, 13b, 1
By opening and closing in order of 3c, the number of times of opening and closing one instantaneous introduction gas shutoff valve can be reduced, and the life of the instantaneous introduction gas shutoff valve can be prolonged.

Although the magnetron sputtering apparatus has been described in the first and second embodiments, the present invention can be applied to other sputtering apparatuses such as a high-frequency sputtering apparatus. In addition, a target other than a flat plate target can be used as a sputtering target.
It is also possible to use N ₂ or the like other gases. Furthermore, in the first and second embodiments, the opening degree of the orifice valve is set to 2
However, if there are two or more patterns, more states may be set.

Comparative example. FIG. 5 is a comparative example of the plasma discharge process. Change the setting of the orifice valve 15 to the opening setting 1 with small conductance (conductance: 30 l
/ Sec), except that the plasma was fixed to the state of / sec). In this comparative example, when the instantaneous introduction gas shut-off valve 13 is opened and Ar gas is introduced, a large amount of Ar gas is adsorbed on the cryopanel of the cryopump 9 and the temperature of the cryopanel becomes about 10K.
The degree has risen. Therefore, warm Ar gas was adsorbed on the surface of the Ar solid previously adsorbed on the surface of the cryopanel. As a result, the Ar solid separated from the surface of the cryopanel due to the thermal stress caused by the temperature difference, and the temperature of the Ar solid rapidly increased and vaporized, so that the degree of vacuum in the chamber 8 was rapidly reduced. Such a decrease in the degree of vacuum, in particular,
When a plurality of electrodes are provided in the same chamber and sputtering is performed a plurality of times, it takes a long time to evacuate the chamber 8 to a high vacuum after one sputtering is completed. In addition, the mixing of the gas discharged from the cryopanel may cause deterioration of the quality of the thin film formed by sputtering and instability of the sputtering speed.

[0036]

As is apparent from the above description, the use of the method according to the present invention makes it possible to reduce outgassing from the cryopanel when plasma discharge occurs. As a result, it is possible to improve the film quality of the thin film produced by the sputtering apparatus and to stabilize the film forming rate, thereby improving the production yield.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a plasma discharge process according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a plasma discharge process according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram of a magnetron sputtering apparatus used in the first embodiment of the present invention.

FIG. 4 is a schematic diagram of a magnetron sputtering apparatus used in Embodiment 2 of the present invention.

FIG. 5 is a schematic view of a plasma discharge process according to a conventional method.

[Explanation of symbols]

1 ... substrate, 2 ... target, 3 ... magnet, 4 ... magnetic field,
5 ... Earth shield, 6 ... Mass flow controller,
7 ... valve, 8 ... fixed valve, 9 ... cryopump, 10 ... electrode, 11 ... power supply, 12 ... fixed valve,
13 ... instantaneous gas introduction shut-off valve, 14 ... main valve, 15 ... orifice valve, 16 ... thin film, 20 ...
Operation of instantaneous introduction gas shut-off valve, 21 ... power supply,
22 ... Degree of vacuum, 24 ... Operation of orifice valve.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 21/31 H01L 21/31 C (72) Inventor Katsuyuki Kita 1006 Ojidoma, Kazuma, Osaka Matsushita Electric Industrial Incorporated (72) Inventor Koji Imamura 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd.F-term (reference) EG06 EH14 EH16 EH19 5F103 AA08 BB12 BB47 BB52 NN04 RR01

Claims (14)

[Claims] 1. A method for generating plasma in a plasma processing apparatus that evacuates the inside of a vacuum chamber with a cryopump, wherein the vacuum chamber has a vacuum degree such that plasma discharge is stable. A first gas introducing step of flowing a first gas into the chamber; and flowing the second gas through the vacuum chamber so that the degree of vacuum in the vacuum chamber becomes a degree of discharge vacuum at which plasma discharge occurs. A second gas introduction step of shutting off a gas; and a discharge step of generating a plasma discharge in the vacuum chamber after the vacuum degree of the vacuum chamber reaches the discharge vacuum degree, further comprising the second gas introduction step. An exhaust conductance limiting step for increasing the exhaust conductance between the vacuum chamber and the cryopump; and reducing the exhaust conductance after the discharging step. Plasma generating method characterized by comprising a gas conductance relaxation step. 2. The method according to claim 2, wherein the step of introducing the second gas includes the step of shutting off the second gas after introducing the second gas.
2. The plasma generation method according to claim 1, wherein the step is a stepwise second gas introduction step of repeatedly changing the degree of vacuum in the vacuum chamber stepwise. 3. The stepwise second gas introduction step is a step of sequentially opening and closing at least two or more valves arranged in parallel in a second gas introduction path to introduce the second gas. 3. The method according to claim 2, wherein: 4. The exhaust conductance limiting step is a step of increasing the exhaust conductance after the stable vacuum degree becomes substantially constant.
The plasma generation method according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the exhaust conductance relaxation step is performed after the degree of vacuum in the vacuum chamber reaches the degree of discharge vacuum and further returns to the degree of vacuum before the introduction of the second gas. Item 4. The plasma generation method according to any one of Items 1 to 3. 6. The difference between the temperature of the cryopanel of the cryopump before the exhaust conductance limiting step and the temperature of the cryopanel after the exhaust conductance mitigation step is within 2 degrees. 4. The plasma generation method according to any one of 1 to 3. 7. The stable vacuum degree is 1 to 9 × 10 ⁻³ To.
The method according to claim 1, wherein rr is rr. 8. The discharge vacuum degree is 1 to 5 × 10 ^-2 To.
The method according to claim 1, wherein rr is rr. 9. The exhaust conductance limiting step and the exhaust conductance relaxing step are performed by opening and closing an orifice valve or opening and closing a main valve provided between the vacuum chamber and the cryopump. The plasma generation method according to claim 1, wherein 10. The method according to claim 1, wherein the second gas introducing step is a step of opening a valve provided in the introduction path of the second gas for 0.1 to 0.7 seconds. Plasma generation method. 11. The method according to claim 11, wherein the step-wise second gas introduction step includes a second step.
3. The plasma generation method according to claim 2, wherein at least two or more valves arranged in parallel in the gas introduction path are sequentially opened for a maximum of 0.3 seconds. 12. The method according to claim 1, wherein the plasma processing apparatus is a sputtering apparatus. 13. A vacuum chamber for generating plasma, a gas introduction pipe for introducing gas into the vacuum chamber,
A cryopump connected to the vacuum chamber through an orifice valve and / or a main valve and configured to evacuate the vacuum chamber, wherein the gas introduction pipe is used to stabilize the plasma. A first gas introduction pipe for supplying a required flow rate of the first gas, and a second gas introduction pipe for supplying a flow rate of a second gas required for generating the plasma; And a plurality of valves provided in parallel with the piping. 14. The plasma processing apparatus according to claim 13, wherein said plasma processing apparatus is a sputtering apparatus.