JPH0831445B2 - Plasma processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a plasma processing apparatus.

(Prior art) Conventionally, plasma processing equipment has been ECR etching equipment or C
It is widely used in VD devices, etc., especially in semiconductor manufacturing processes.

In a conventional plasma processing apparatus using microwaves such as ECR or CVD, as shown in FIG. 8, the output of the microwave generator 10 is a rectangular waveguide 12, a power monitor 14, and the length of the waveguide. It is formed so as to be guided to the discharge chamber 18 through a tuner 16 that changes the temperature. The discharge chamber 18 is formed so as to communicate with the reaction chamber 20.

Here, a susceptor 24 on which a wafer 22 is placed is provided in the reaction chamber 20. Also, this reaction chamber
A vacuum pump 26 is connected to 20 and is formed so as to create a desired vacuum state in the reaction chamber 20.

A gas supply device 28 is connected to the discharge chamber 18, and a magnetic field coil 30 for applying a magnetic field is provided around the gas supply device 28.
Is installed.

Usually, the discharge chamber 18 is designed to have a diameter and a height that are the dimensions of a cavity resonator, and thus when a vacuum state is created in the discharge chamber 18, the discharge chamber 18 becomes in a resonance state.

In the plasma processing apparatus thus formed, the discharge chamber 18 and the reaction chamber 20 are evacuated, and then a gas is introduced into the discharge chamber 18 and the reaction chamber 20 to apply a magnetic field to apply a microwave. , An ECR condition is created,
Plasma is generated in the discharge chamber 18.

However, when plasma is generated, the dielectric constant in the discharge chamber 18 becomes a value different from that in vacuum. Because of this, the discharge chamber
The wavelength of the microwave supplied to 18 changes, and a mismatching state, that is, a state where matching cannot be achieved, occurs.

Therefore, a part of the microwave power supplied to the discharge chamber 18 via the waveguide 12 is reflected in the discharge chamber 18, and the reflected power returned to the waveguide 12 is generated.

Therefore, the waveguide 12 is provided with the circulator 32 and the dummy 34 so that the reflected wave does not return to the microwave generator 10.

By the way, in such a plasma processing apparatus, if a large amount of reflected power is generated, the effective power that can be converted into plasma in the discharge chamber 18 is reduced. Therefore, it is necessary to provide a means capable of matching in accordance with the change in the wavelength of the microwave.

For this reason, a tuner 16 for matching adjustment is normally provided between the waveguide 12 and the discharge chamber 18, and the tuner 16 is tuned in accordance with the power of the reflected wave so that the waveguide 12 and It is formed so that it can be matched with the discharge chamber 18.

Then, the reflected power is detected using the power monitor 14 provided in the waveguide 12, and the detected reflected power is displayed on the display unit 36.
The tuner 16 is tuned so that the reflected power displayed on the display unit 36 is minimized by moving the tuner driving device 40 by using the control circuit 38 based on the detected data while displaying the above.

(Problems to be Solved by the Invention) As described above, the conventional plasma processing apparatus requires the power monitor 14 and the display unit 36 for tuning.

However, the power monitor 14 has a large shape and a complicated structure. In particular, since the power monitor 14 is formed integrally with the waveguide 12, it is necessary to move the power monitor 14 integrally with the waveguide 12 when the tuner 16 is moved and its length is changed. In addition, there is a problem that the entire device is inevitably large.

Further, in such a conventional device, since both the power monitor 14 and the display unit 36 are required, there is a problem that the cost of the entire device becomes expensive.

Therefore, an object of the present invention is to address the above-mentioned conventional problems, and it is possible to detect reflected power without using a power monitor and automatically perform microwave tuning. Another object of the present invention is to provide a plasma treatment apparatus capable of performing the treatment.

[Structure of Invention]

(Means for Solving Problems) In order to achieve the above-mentioned object, the present invention is an apparatus for treating an object to be processed by irradiating a microwave to generate plasma, wherein the object to be processed is provided. A current flowing through the susceptor is detected, and a tuner provided between the microwave supply system and the plasma generator is tuned and controlled so that the susceptor current becomes maximum.

(Operation) Next, the operation of the present invention will be described.

The plasma processing apparatus supplies microwave power from a microwave generator to a plasma reaction container to generate plasma in the container.

The present inventors have found that when plasma is generated in the container, a current having a certain correlation with the plasma energy flows through the susceptor provided in the container.

Then, when the relationship between the susceptor current and the reflected power from the container was examined, there was a certain correlation between them, and if the susceptor current was detected, the reflected power from the container could be calculated based on this detected current. It turned out to be possible.

The feature of the present invention resides in that the reflected power from the container is detected based on the current flowing through the susceptor provided in the container as described above.

Then, tuning control of the tuner is performed based on the reflected power detected in this way, and plasma is efficiently generated in the container.

As described above, according to the present invention, it is not necessary to provide a power monitor in the waveguide as in the conventional device, and the reflected power is indirectly detected by simply measuring the current flowing through the susceptor provided in the container. Therefore, tuning control of the tuner can be performed at low cost with a simple device.

(Embodiment) Next, a preferred embodiment of the present invention will be described with reference to the drawings.
The members corresponding to those of the conventional device shown in FIG. 8 are designated by the same reference numerals and the description thereof will be omitted.

First, a preferred example of a plasma processing apparatus and a tuning apparatus for the same according to the present invention will be described with reference to FIG.

In the plasma processing apparatus of the embodiment, the output of the microwave generator 10 is supplied to the discharge chamber 18 via the waveguide 12 and the tuner 16 to generate plasma in the discharge chamber 18 and the reaction chamber 20.

By the way, applying a negative bias voltage to the susceptor 24,
When plasma was generated in this state, the susceptor current Is and the microwave reflection power were measured, and the measurement results shown in FIG. 2 were obtained. At this time, the reflection power was measured by using the conventional apparatus shown in FIG.

As is clear from this measurement result, there is a certain correlation between the susceptor current Is and the microwave reflection power. This is the discharge chamber when the microwave reflected power is minimal.
This is because the effective microwave power supplied to 18 and the reaction chamber 20 becomes maximum, and the current Is flowing in the susceptor 24 becomes maximum due to the ions or electrons generated by this plasma.

Therefore, by measuring the susceptor current Is, the state of the reflected power from the discharge chamber 18 can be indirectly detected.

Therefore, in the present invention, a current detection circuit 42 that applies a negative bias voltage to the susceptor 24 and detects the current Is flowing through the susceptor 24 is provided.

Then, the control circuit 38 calculates a tuning signal based on the detected susceptor current Is so that the susceptor current Is becomes maximum, and outputs the tuning signal to the tuner drive circuit 40.

The tuner drive circuit 40 tunes and controls the tuner 16 on the basis of this tuning signal to guide the waveguide 12 and the discharge chamber.
Adjust the length of the waveguide so that it can be matched with 18.

As described above, according to the present invention, the tuning control of the tuner 16 can be automatically performed based on the current Is flowing in the susceptor 24, and the tuning control can be performed as compared with the conventional technique using the power monitor 14 and the display unit 36. Can be performed extremely easily.

Further, the current detection circuit 42 of the embodiment is formed using a DC bias source 44, a resistor 46, a capacitor 48 and an amplifier 50, as shown in FIG. And a DC bias source 44
Is used to apply a negative bias voltage to the susceptor 24, and the current flowing through the susceptor 24 is detected and output via the amplifier 50.

As such a current detection circuit 42, an RF bias source 52 may be used instead of the DC bias source 44 as shown in FIG.

The control circuit 38 of the embodiment is constructed by using a one-chip CPU as shown in FIG. Then, the susceptor current Is output from the current detection circuit 42 is input to the one-chip CPU, and the unidirectional movement end limit signal and the + direction movement end limit signal are output from the limit switches 54a and 54b provided in the tuner 16. Has been entered.

Further, the tuner drive circuit 40 of the embodiment includes a motor driver 60, a motor 62 and a drive mechanism section 64 as shown in FIG.
And is formed so that the length of the tuner 16 can be adjusted.

Further, in the present embodiment, the one-chip CPU constituting the control circuit 38 is formed so as to perform the calculation according to the flowchart shown in FIG.

That is, the control circuit 38 of the embodiment reads the susceptor current Is detected by the current detection circuit 42 at regular time intervals, in this case, every 5 seconds, and calculates the change ΔIn.

Then, when the variation ΔIn of the detected current is less than or equal to the predetermined allowable error ΔI, it is determined that the detected susceptor current Is is near the maximum value, and the tuner 16 is stopped and controlled at that position.

If the change amount ΔIn of the detected current exceeds the allowable range ΔI, it is next determined whether the change amount ΔIn is a positive value or a negative value. When it is determined that the value is a positive value, the tuner 14 is controlled to be long so that Is takes the maximum value. When the variation ΔIn is negative, the tuner 16 is controlled to be short so that Is or the maximum value is obtained.

The control circuit 38 repeats such arithmetic control operation every 5 seconds.

Therefore, according to the device of the embodiment, the length of the tuner 16 is automatically controlled so that the susceptor current Is takes the maximum value,
As a result, even if the microwave wavelength changes,
The length of the tuner 16 is automatically controlled so that the waveguide 12 and the discharge chamber 18 can be matched, and the reflected power from the discharge chamber 18 can be suppressed to a minimum value.

Further, the tuner 16 and the drive mechanism 64 of this embodiment constitute the tuning mechanism shown in FIG. 7, and the tuning mechanism of this embodiment includes a fixed waveguide 70, a movable waveguide 72, and a fixed waveguide. The bracket 74, the movable waveguide bracket 76, the motor 62, the pulley 80, the pulley 82, the drive belts 84a and 84b, the drive ball screw 86, the slide bearing 88, and the slide shaft 90 are used.

Then, in this tuning mechanism, when the susceptor current Is changes, the motor 62 is driven based on the drive command output from the one-chip CPU 38 described above.

The rotation output of the motor 62 transmits the rotation to the pulleys 82 and 80 via the belts 84a and 84b.

The drive ball screw 86 is directly connected to the pulley 80. Therefore, the rotation of the motor 62 is transmitted to the ball screw 86, moves the movable waveguide bracket 76, and automatically moves the susceptor current.
The waveguide 72 is moved to a position where Is has the maximum value.

Further, the slide shaft 90 is fixed to the fixed waveguide bracket 74 as an axis of a slide bearing 88 fixed to the movable waveguide bracket 76 in order to receive the weight of the movable waveguide 72.

It should be noted that such a tuning mechanism is used in the movable waveguide 72
It is sufficient if the length can be automatically variably adjusted and tuned by using a motor, an air cylinder, or another drive source. Therefore, a rack and pinion or other driving means may be used instead of the ball screw.

Further, in the present embodiment, the tuner 16 has been described as an example of a type in which the length of the waveguide is changed, but the present invention is not limited to this, and other types of tuners may be used if necessary. For example, a stub tuner or an EH tuner may be used, or any two or more of them may be used together.

In addition, in this embodiment, the control circuit 38 is a one-chip CP.
Although the description has been made by taking the case of using U as an example, the present invention is not limited to this, and the circuit configuration may be of either an analog type or a digital type as required.

Further, in the present embodiment, the control circuit 38 has been described as an example in which the position of the tuner 16 is adjusted according to the flow shown in FIG. 6, but the present invention is not limited to this, and other adjustment methods may be used as necessary. For example, it is possible to scan the variable range of the tuner 16 once to detect a position where the susceptor current Is is minimized, and then adjust the tuner 16 to the minimum position.

〔The invention's effect〕

As described above, according to the present invention, since the reflected power of the microwave is detected based on the susceptor current,
The microwave power monitor or the like used in the conventional device becomes unnecessary, and the tuning control of the tuner can be performed using a small and inexpensive device.

In particular, according to the present invention, since a power monitor having a complicated structure is unnecessary, the structure of the entire apparatus can be simplified, and the labor required for maintenance management can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a preferred example of a plasma processing apparatus to which the present invention is applied and a tuning apparatus therefor, and FIG. 2 is a graph showing correlation data between a current flowing through a susceptor of the apparatus shown in FIG. 1 and reflection power. Explanatory diagrams, FIGS. 3 and 4 are circuit diagrams of the current detection circuit shown in FIG. 1, FIG. 5 is a block diagram of the control circuit and tuner drive circuit shown in FIG. 1, and FIG. 6 is shown in FIG. FIG. 7 is a flowchart showing the operation of the 1-chip CPU shown in FIG. 7, FIG. 7 is an external view of the tuning mechanism used in this embodiment, and FIG. 8 is an explanatory view of a conventional plasma processing apparatus provided with the tuning mechanism. 10 …… Microwave generator 12 …… Waveguide 16 …… Tuner 18 …… Discharge chamber 20 …… Reaction chamber 24 …… Susceptor 38 …… Control circuit 42 …… Current detection circuit

Claims (2)

[Claims] 1. An apparatus for treating an object to be processed by irradiating a microwave to generate plasma, detects a current flowing through a susceptor provided with the object to be processed, and maximizes the susceptor current. A plasma processing apparatus, wherein tuning is performed on a tuner provided between the microwave supply system and a plasma generation unit. 2. A tuner provided in a microwave transmission path between a microwave generator and a vacuum container, and a current detecting means for applying a bias voltage to a susceptor of the vacuum container to detect a current flowing through the susceptor. A control means for tuning and controlling the tuner so that the detected susceptor current has a maximum value, and the vacuum container and the microwave transmission path are automatically matched with each other. The plasma processing apparatus according to the item.