JPH07240298A - Discharge starting mechanism of plasma processing device - Google Patents

Abstract

PURPOSE:To start the discharge of a microwave simply and securely by installing the output terminal of a high voltage generating device to the outer wall near the discharge member of a discharge tube, and applying an AC high voltage to the outer wall of the discharge tube immediately after the microwave is applied. CONSTITUTION:A wafer substrate 17 is loaded on a holding board 16 in a vacuum processing chamber 10, and after heating to a specific temperature, the chamber 10 and a discharge tube 20 are vacuum evacuated by a vacuum pump 13. At the same time, the oxygen gas is fed from a gas feeding end 25 into the tube 20. Then, a microwave with the frequency 2.45 GHz is applied from a microwave current source 31, and immediately after that, a voltage with + or -6KV in the earthing standard is applied to the outer wall of the tube 20 through the output terminal of an AC voltage trigger. A plasma of oxygen gas is produced by the discharge in the tube 20, and a gas including high activity of neutral oxygen radicals is led in to the chamber 10. The oxygen gas is reacted with a resist membrane on the substrate 17, and the membrane can be ashing removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge initiation mechanism for a microwave plasma processing apparatus, and more particularly to a discharge initiation mechanism for ensuring the initiation of microwave discharge.

[0002]

2. Description of the Related Art In a plasma processing apparatus using microwaves, such as a plasma etching apparatus, a plasma ashing apparatus, a plasma CVD (chemical vapor deposition) apparatus, etc., a microwave is applied to discharge plasma. However, the impedance changes before and after plasma generation, or process conditions,
For example, since the impedance varies depending on the type of plasma generating gas, the pressure, the flow rate, and the power of the applied microwave, a stub tuner or an E is used for the microwave waveguide.
A matching device such as an H tuner is provided to match the microwave.

Regarding the change in impedance before and after plasma generation, for example, regarding the position of the stub tuner, the insertion depth position where discharge is most likely to start before plasma generation and the reflected wave of microwaves after plasma generation are the most. Different from the smaller insertion depth position.
Therefore, at first, plasma should be generated with the stub tuner as a certain position for starting the discharge, and immediately after that, it should be moved to a position where the reflected wave of the microwave becomes small, and the adjustment should be done manually. Is inefficient and unproductive, so some are self-adjusting. That is, this is a method of automatically adjusting the position of the stub tuner while monitoring the reflected wave of the microwave and feeding it back. However, this method has a complicated mechanism and operation, and the device cost also rises.

On the other hand, when the LSI (Large Scale Integrated Circuit) of a semiconductor product and other electronic parts are mass-produced, the above-mentioned process conditions in the microwave plasma processing apparatus used are constant, so that plasma generation is performed. The matcher is often pre-adjusted to match the microwaves later. However, in such adjustment, discharge may not be started even if microwave is applied, and plasma may not be generated. This is because the impedance is largely different before and after plasma generation, as described above.

In order to deal with this, an output terminal of a high voltage trigger has been provided inside the discharge tube, but this method contaminates the vacuum processing chamber with the metal of the output terminal, resulting in This caused a problem that the characteristics of the electric circuit were deteriorated. Therefore, currently, an ultraviolet lamp is installed outside the discharge tube, and ultraviolet rays are applied to the inside of the discharge tube.
A method of initiating discharge by the effect of photoelectrons is widely adopted.

Hereinafter, a microwave plasma processing apparatus for starting discharge by this ultraviolet irradiation will be described as a conventional example. FIG. 5 is a side sectional view of a plasma ashing apparatus 1 as an example of a microwave plasma processing apparatus. In general, a vacuum processing chamber 10 that accommodates a wafer substrate 17 to be ashed (resist film ashing treatment), a discharge tube 20 that converts the supplied oxygen gas into plasma, and a microwave is applied to the discharge tube 20. Microwave power source 3
1 and its waveguide 30.

That is, the protrusions 14a and 14b facing the inner wall of the vacuum processing chamber 10 are provided, and the gas rectifier 15 is supported by these protrusions 14a and 14b. Also, gas rectifier 1
Although not shown, a support table 16 provided with a heating mechanism used when necessary is provided below the wafer 5, and a wafer substrate 17 from which the resist film is to be removed is placed on the support table 16. Furthermore,
An insertion fixing portion 18 for inserting an end portion of the discharge tube 20 is provided on the side wall of the vacuum processing chamber 10, and the exhaust port 1 provided on the bottom wall.
A vacuum pump 13 is connected to 1 via a vacuum valve 12.

The discharge tube 20 penetrates the waveguide 34 with a gap, and as described above, one end is inserted into the insertion fixing portion 18 of the vacuum processing chamber 10 and both are vacuum-sealed by an O-ring 22b. The other end of the discharge tube 20 is inserted into the oxygen gas supply end 25, and both are vacuum-sealed by the O-ring 22a. The discharge tube 20 is made of quartz glass, sapphire,
Alternatively, it is manufactured using an insulator such as alumina.

The waveguide 30 has a microwave power source 3 at the beginning.
1, a stub tuner 32 is provided below the discharge tube 20 by inserting the waveguide 30, and a termination matching unit 33 is provided at the terminal end for matching microwaves. Furthermore, in the portion where the discharge tube 20 penetrates, the discharge tube 20
A cylindrical sleeve 35 extending inwardly from the side wall of the waveguide 20 and extending to approximately the center thereof is provided with a gap around the circumference. The sleeve 35 is provided to concentrate the electric field of microwaves on the discharge portion in the discharge tube 20.

Then, this plasma ashing apparatus 1
On the other hand, an ultraviolet lamp 40 for irradiating the inside of the discharge tube 20 with ultraviolet rays is installed on the oxygen gas supply end 25 side of the discharge tube 20. A quartz window 26 for transmitting ultraviolet rays is provided at the oxygen gas supply end 25.

The conventional discharge initiation mechanism for the plasma ashing apparatus 1 is constructed as described above, and its operation will be described below.

A wafer substrate 17 on which a resist film used for fine processing remains is placed on a support 16 in the vacuum processing chamber 10 and heated to a predetermined temperature. Then, the vacuum valve 12 is opened, and the vacuum processing chamber 1 is operated by the vacuum pump 13.
0, the discharge tube 20 is evacuated. On the other hand, oxygen gas from a cylinder (not shown) is supplied into the discharge tube 20 from the gas supply end 25.

The microwave power supply 31 causes a frequency of 2.4.
While applying a microwave of 5 GHz to the discharge tube 20,
The ultraviolet lamp 40 is turned on, and the discharge tube 20 is discharged through the quartz window 26.
When the interior is irradiated with ultraviolet rays, a discharge occurs in the discharge tube 20 and plasma of oxygen gas is generated. That is, the supplied oxygen gas is turned into plasma by passing through the plasma discharge region 21, and then introduced into the vacuum processing chamber 10 as a gas containing highly active neutral oxygen radicals. Further, it is rectified by the gas rectifier 15 and uniformly transported on the wafer substrate 17, and reacts with the resist film on the wafer substrate 17 to remove it. The removed material is discharged to the outside of the system by the vacuum pump 13.

This plasma ashing apparatus 1 facilitates the initiation of discharge and the generation of plasma by irradiating it with ultraviolet rays, but it has not yet reached a satisfactory level. That is, when the stub tuner 32 is adjusted so that the reflected wave of the microwave becomes small after plasma generation, there is a problem that the discharge start probability is still low. FIG. 6 shows a case where the microwave power is 1 kW,
It is a figure which shows the relationship between the magnitude of the reflected wave Pr after plasma generation, and discharge start probability, and if the stub tuner 32 is adjusted so that reflected wave Pr = 120 W, a discharge start probability will be 1.
Although it is 00%, it is 8 when adjusting the reflected wave Pr = 50W.
If the adjustment is made to 0% and the reflected wave Pr = 10 W, the discharge start probability is lowered to 40%.

Furthermore, this ultraviolet irradiation method is based on the quartz window 26.
The dirt makes it difficult for the ultraviolet rays to reach the inside of the discharge tube 20, and there is a problem that the effect of the ultraviolet rays decreases with time.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a discharge starting mechanism in a plasma processing apparatus capable of easily and reliably starting microwave discharge.

[0017]

The above objects are at least a vacuum processing chamber, a waveguide for transmitting microwaves,
One end is inserted into the vacuum processing chamber through the waveguide.
In a microwave plasma processing apparatus having a discharge tube whose other end is a plasma generation gas supply port, an output terminal of a high voltage generator is attached to an outer wall of the discharge tube in the vicinity of a discharge portion to apply a microwave. This is achieved by a discharge starting mechanism of a plasma processing apparatus, which is characterized in that discharge is started surely at times.

Further, the above object is to provide a plasma processing apparatus in which an RF (high frequency) power source is connected to an electrode in a vacuum processing chamber in which a wall portion is made of an insulating material and which is provided with a plasma generating gas inlet, and high voltage is generated in the wall portion. The discharge initiation mechanism of the plasma processing apparatus is characterized in that the output terminals of the apparatus are arranged close to each other.

[0019]

The high voltage generator having the output terminal attached to the outer wall of the discharge tube in the vicinity of the discharge portion works as a trigger, so that even when the matching device is adjusted so that the reflected wave of the microwave becomes small after plasma generation. , The discharge by microwave is surely started. Alternatively, the discharge can be started easily and surely even in the plasma processing apparatus using the RF power source.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A discharge starting mechanism according to an embodiment of the present invention will be described below with reference to the drawings. In this embodiment, as the microwave plasma processing apparatus, the same plasma ashing apparatus 1 as that described in the conventional example is used, and FIG. 1 is a side sectional view thereof. Therefore, the same components are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, referring to FIG. 1, the plasma ashing apparatus 1 generally has a vacuum processing chamber 10 for accommodating a wafer substrate 17 to be ashed, and an electric discharge for converting oxygen gas used for ashing into plasma. Tube 20
And a microwave power source 31 for applying microwaves to the discharge tube 20 and a waveguide 30 thereof.
These configurations, including attached devices, are the same as those described in the conventional example.

As the discharge initiation mechanism of the embodiment, the electrode of the AC high voltage trigger 50 or the output terminal 51 is provided on the outer wall of the discharge tube 20 made of quartz glass in the vicinity of the discharge portion.
Abut. The details are shown in FIG. The AC high voltage trigger 50 includes a switch 52, an AC power supply 53, and a step-up transformer 54, and one end on the secondary side is grounded. This grounding may be performed, for example, through the portion of the waveguide 30 that is close to the discharge tube 20. As a matter of course,
The ultraviolet lamp 40 used in the conventional example is removed, and the quartz window 26 at the oxygen gas supply end 25 is unnecessary.

The discharge initiation mechanism in the plasma ashing apparatus 1 according to this embodiment is constructed as described above.
Next, the operation will be described.

A wafer substrate 17 is placed on a support 16 in the vacuum processing chamber 10 with the resist film to be removed as an upper surface, heated to a predetermined temperature, the vacuum valve 12 is opened, and the vacuum pump 13 is opened. Then, the vacuum processing chamber 10 and the discharge tube 20 integrated with the vacuum processing chamber 10 are evacuated. At the same time, oxygen gas from a cylinder (not shown) is supplied into the discharge tube 20 from the gas supply end 25.

Then, a microwave of frequency 2.45 GHz is applied and applied to the discharge tube 20 by the microwave power source 31, and immediately thereafter, the switch 52 of the AC high voltage trigger 50 is closed and the output terminal 51 is used to close the discharge tube 20. When a voltage of ± 6 KV with respect to the earth is applied to the outer wall, a discharge is generated in the discharge tube 20 to generate oxygen gas plasma. That is, the oxygen gas supplied from the gas supply end 25 is subsequently turned into plasma by passing through the plasma discharge region 21 in the discharge tube 20, and becomes a gas containing highly active neutral oxygen radicals, which is a vacuum processing chamber. Introduced in 10. This gas reacts with the resist film on the wafer substrate 17 to ash and remove the resist film, as in the case of the conventional example.

The function of the discharge initiation mechanism of this embodiment is as follows.
When a voltage is applied to the outer wall of the discharge tube 20 as an insulator by the output terminal 51 of the AC high voltage trigger 50, the discharge tube 2
An electric field having a high potential gradient is formed in 0, the wall of the discharge tube 20 is polarized, and a large amount of electrostatic charge is locally induced on the inner wall.
It is thought that the collision of oxygen gas molecules with this electrostatic charge is the cause of the discharge start.

FIG. 3 is a diagram showing the discharge start probability of the plasma ashing apparatus 1 by the discharge start mechanism according to this embodiment, and corresponds to FIG. 6 described in the conventional example. That is, in the case of the discharge starting mechanism of the present embodiment, it goes without saying that the stub tuner 32 is adjusted so that the reflected wave Pr after plasma generation is 120 W when the power of the microwave applied and applied is 1 KW. That the reflected wave P
Even when r was adjusted to be as small as 50 W and 10 W, the discharge start probability was 100%. As described above, when the discharge starting mechanism according to the present embodiment is used, microwave discharge is reliably started, and plasma is stably formed.

In the present embodiment, the AC high voltage trigger 50 is adopted, but when this is used as the DC high voltage trigger 50 'as shown in FIG. 2B, the discharge is surely started similarly. In FIG. 2B, the DC high voltage trigger 50 'is composed of a switch 55, a DC power supply 56 and a step-up transformer 57, and one end on the secondary side is grounded.

When an AC high voltage or a DC high voltage is applied, the output terminal 51 is brought into contact with the outer wall of the discharge tube 20 in FIGS. Even if they were placed close to each other with a certain distance, the similar discharge initiation probability was shown. Proximity in the invention of the present application includes abutment and an arrangement in which such a slight distance is provided.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in this embodiment, the plasma ashing device was taken as the microwave plasma processing device to which the discharge starting mechanism is applied, but it can be applied to other plasma etching devices and plasma CVD devices. A reliable start of discharge can be obtained.

Although oxygen gas is used as the plasma generating gas in the embodiments, other gases such as argon (Ar) and CF ₄ may be used depending on the purpose.

In the embodiment, the ground electrode is not provided for the high voltage applied to the outer wall of the discharge tube 20, but the ground electrode is attached to the vacuum processing chamber 10 or the waveguide 30, for example. These may be set to the ground potential.

The discharge starting mechanism of the present invention is also effective for starting RF (high frequency) discharge. FIG. 4 shows this specific example, but the wall of the vacuum chamber 61 is made of an insulating material, for example, quartz, and is connected with a plasma generating gas introduction pipe 68 and an exhaust pipe 69 for vacuum exhaust. In addition, a substrate electrode 62 is arranged inside this, and a substrate 63 to be plasma-processed is provided thereon. In this modification,
A sputtering process is performed. An electrode 65 to which a target 64 is fixed is arranged facing the substrate 63, and an output terminal of an RF (high frequency) power source 66 is connected to the electrode 65 via a capacitor 67. An output terminal 51 of an AC high voltage trigger 50 or a DC high voltage trigger 50 'similar to that of the embodiment is in contact with such a vacuum processing apparatus. Even in such a modification, it is possible to easily and reliably generate plasma, that is, start discharge. In this modification, the sputtering processing apparatus has been described, but the present invention can also be applied to an etching apparatus.

[0035]

As described above, according to the discharge initiation mechanism of the microwave plasma processing apparatus of the present invention, even when the matching device is adjusted so that the reflected wave of microwave becomes small after plasma generation. , The discharge by the microwave is surely started, and the plasma is stably generated. Further, since the output terminal of the high voltage generator is attached to the outer wall of the discharge tube, the vacuum processing chamber cannot be contaminated by the metal of the output terminal.

[Brief description of drawings]

FIG. 1 is a side sectional view of a plasma ashing device to which a discharge starting mechanism according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing how a high voltage generator and its output terminal come into contact with a discharge tube, where A is an AC high voltage trigger,
B is the case of using a DC high voltage trigger.

FIG. 3 shows the same device after plasma generation.
It is a figure which shows the relationship between the magnitude of the reflected wave of a microwave, and a discharge start probability.

FIG. 4 is a side sectional view of a modified plasma processing apparatus.

FIG. 5 is a side sectional view of a plasma ashing device using a discharge initiation mechanism of a conventional example.

FIG. 6 is a diagram showing a relationship between a magnitude of a reflected wave of a microwave and a discharge start probability after plasma is generated in a plasma ashing device having a discharge start mechanism of a conventional example.

[Explanation of symbols]

 10 Vacuum Processing Chamber 17 Wafer Substrate 20 Discharge Tube 21 Plasma Discharge Region 25 Oxygen Gas Supply End 30 Waveguide 31 Microwave Power Supply 50 AC High Voltage Trigger 51 Output Terminal 61 Vacuum Processing Chamber 63 Wafer Substrate 66 RF Power Supply

Claims (4)

[Claims] 1. A vacuum processing chamber, a waveguide for transmitting microwaves, at least one end penetrating the waveguide and being inserted into the vacuum processing chamber, and the other end being a supply port for a plasma generating gas. In the plasma processing apparatus including the discharge tube, the output terminal of the high voltage generator is arranged close to the outer wall of the discharge tube in the vicinity of the discharge part, and the discharge is surely started when the microwave is applied. A discharge initiation mechanism of a plasma processing apparatus characterized by the above. 2. The discharge starting mechanism of the plasma processing apparatus according to claim 1, wherein the high voltage generator is an AC high voltage generator. 3. The discharge starting mechanism of the plasma processing apparatus according to claim 1, wherein the high voltage generator is a DC high voltage generator. 4. A plasma processing apparatus comprising a plasma generating gas introduction port, wherein a wall is made of an insulating material and an RF (high frequency) power source is connected to an electrode in a vacuum processing chamber. A discharge starting mechanism of a plasma processing apparatus, characterized in that they are arranged close to each other.