JPH0950898A - Plasma treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate in-plane ununiformity of an impedance of a pulse bias circuit by providing a conductor which is parallel to a sample and substantially functions as a ground electrode. SOLUTION: Plasma treatment device is provided with a plasma generating chamber 2 for introducing an electromagnetic wave 1 and a discharge gas, a means for introducing the electromagnetic wave 1 therein, and a dielectric window 46 for partitioning the plasma generating chamber 2 and the electromagnetic wave introduction means. It is also provided with a holder 3 on which a sample to be treated using plasma generated by the electromagnetic wave 1 is mounted and a means 5 for applying pulse voltage on the holder 3 as a bias. It is characterized as a structure that a conductor is provided in parallel to the sample and substantially functions as a ground electrode 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a bias to a plasma processing apparatus and a plasma processing apparatus equipped with a means for uniformly applying the bias to the entire surface of a sample.

[0002]

2. Description of the Related Art Conventionally, in a dry etching or CVD apparatus for processing or depositing a sample by using plasma and a high frequency bias applied to the sample, a charge-up phenomenon to the sample called electron shading effect and Distortion of the processed shape (mainly notching in dry etching) resulting from this is a problem. Therefore, as a bias high frequency, a positive short pulse is applied by using a pulse power source to pull electrons into the sample to electrically neutralize the sample positively charged up, thereby suppressing notching. -6
1182, etc.

[0003]

The above-mentioned prior art requires, for example, a repetition frequency of 100 KHz, a duty ratio of 1% or less, and a pulse width of about 100 ns. This means that when this pulse wave is considered in the Fourier spectrum, it has a band of 100 KHz to 100 MHz,
Special techniques are required to apply the pulse evenly to the sample without distorting the pulse waveform. That is, in this case, what is particularly problematic is the path from the center of the sample to the ground electrode through the plasma in the bias circuit, and the path impedance from the center of the sample to the ground electrode and the path from the sample end to the ground electrode. If the impedances are the same and do not have a wide bandwidth, there is a problem that in-plane non-uniformity of processing and sample damage caused by the unevenness occur.

Particularly, in an ECR type plasma processing apparatus in which magnetic lines of force are applied substantially perpendicularly to a sample and plasma is generated by microwaves, the ground electrode is generally located in the side wall direction of the processing chamber, and the lines of magnetic force are also present. The impedance of the bias circuit that tries to flow across the
In the band of up to 100 MHz, the in-plane non-uniformity of bias application to the sample becomes very large because it becomes very large.

An object of the present invention is to provide a plasma processing apparatus which eliminates in-plane nonuniformity of impedance of a pulse bias circuit and realizes uniform sample processing.

[0006]

In order to achieve the above object, a plasma generating chamber into which an electromagnetic wave and a discharge gas are introduced,
A means for introducing the electromagnetic wave into the plasma generation chamber, a dielectric window for partitioning the plasma generation chamber and the electromagnetic wave introduction means, a holder for mounting a sample to be processed using the plasma generated by the electromagnetic wave, and a holder In a plasma processing apparatus equipped with a means for applying a pulse voltage as a bias, a conductor parallel to the sample and substantially functioning as a ground electrode is provided.

Desirably, a means for generating lines of magnetic force is provided so that a microwave is used as the electromagnetic wave so as to be substantially orthogonal to the sample.

Desirably, an electrode is provided which is in contact with the dielectric window and allows electromagnetic waves to pass substantially uniformly over the entire surface, and the electrode is substantially set to the ground potential.

Preferably, a coaxial waveguide is used as the microwave introducing means.

Preferably, the electromagnetic wave is 1 to 100 MH
It is characterized by using a high frequency inductive method in the z band.

[0011]

FIG. 2 shows an equivalent circuit of a high frequency current path in plasma. In this case, the microwave E
The case of CR is described as an example. R in FIG.
And C are the resistance and capacitance in the sheath between the plasma samples,
L is an inductance when a current flows in the plasma across the line of magnetic force B. Since the electrons in the plasma cannot move across the lines of magnetic force, the ions are responsible for electrical conduction, but due to inertia, it is difficult for current to flow and equivalently acts as the inductance L. Impedance jωL that crosses the magnetic field line is calculated as j10 at 1 MHz by theoretical calculation.
Since it is about 0Ω and is proportional to the frequency, it reaches j10 kΩ at 100 MHz. R of sheath and 1 / jωC
Is 100Ω or less, so jωL is dominant at high frequencies of 10 MHz or more. There will be a large difference in impedance between the center and the end of the sample, resulting in non-uniformity. (That is, there is a disparity between I ₁ and I _2. )
If the ground electrode could be placed on top of the sample in parallel with the sample, the impedance in the direction parallel to the magnetic field lines would originally be so small that it could be ignored, and there would be no difference between the center and the end of the sample, resulting in non-uniformity. Will be resolved. I ₃ and I ₄ become equal. An embodiment will be described below as a method for specifically realizing this.

[0012]

FIG. 1 is a diagram showing a first embodiment of the present invention. This is an example applied to a microwave ECR device. In FIG. 1, the microwave 1 is guided in the circular TE11 mode and introduced into the plasma chamber 2. A pulse power source 5 is applied to the electrode 3. In the TE11 mode, the power supply vector is aligned in one direction on the plane perpendicular to the waveguiding direction, so even if a conductor with a slit cut perpendicular to it is installed, microwaves pass through without interruption. To do. In FIG. 1B, such a slit conductor 4
A was set to the ground potential, and it was attached to the microwave introduction window 4b. The slit electrode 4a may be provided with, for example, a thin cover quartz 4c so as not to be directly exposed to plasma and cause metal contamination. The thickness is
The impedance of the high-frequency circuit is set to such a degree that it does not hinder (eg, 3 mm or less).

FIG. 3 shows an example of application to an inductively coupled high frequency plasma device. In the case of induction plasma, the coil 14 is wound concentrically, and the electric field vector 4h entering the plasma also faces the same direction as the coil. Therefore,
The slit electrodes 4a may have a radial shape as shown in FIG.

FIG. 4 shows the case of the microwave ECR, but shows an example of introducing the microwave in the coaxial TEM mode. In such an example, since the microwave is emitted from the outer peripheral portion of the upper surface of the chamber, the ground electrode 4a can be directly attached to the central portion of the upper surface.

[0015]

As described above, according to the present invention, it is possible to ensure the uniformity of sample processing when a pulse bias is applied.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory view showing a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microwave, 2 ... Processing chamber, 3 ... Sample stand, 4 ... Introduction window, 4a ... Ground electrode, 4b ... Dielectric material, 4c ... Dielectric material, 5
... pulse bias power supply, 4h ... electric field vector.

Claims (5)

[Claims] 1. A plasma generating chamber into which an electromagnetic wave and a discharge gas are introduced, a means for introducing the electromagnetic wave into the plasma generating chamber, a dielectric window for partitioning the plasma generating chamber and the electromagnetic wave introducing means, and the electromagnetic wave. In a plasma processing apparatus comprising a holder for mounting a sample to be processed using the generated plasma and a means for applying a pulse voltage as a bias to the holder, a conductor is provided parallel to the sample and substantially functioning as a ground electrode. A plasma processing apparatus characterized by the above. 2. The plasma processing apparatus according to claim 1, further comprising means for generating a magnetic force line so that a microwave is used as the electromagnetic wave so as to be substantially orthogonal to a sample. 3. The electromagnetic wave according to claim 1, wherein the electromagnetic wave is 1
A plasma processing apparatus characterized by using an induction high frequency in the range of up to 100 MHz. 4. A plasma processing apparatus according to claim 2, further comprising an electrode which is in contact with said dielectric window and which transmits an electromagnetic wave substantially uniformly over the entire surface thereof, and which is set to a substantially ground voltage. 5. The plasma processing apparatus according to claim 2, wherein a coaxial waveguide is used as the microwave introducing means.