JPH03158471A - Microwave plasma treating device - Google Patents

Abstract

PURPOSE:To uniformly maintain the plasma near a large-diameter semiconductor substrate at a high density by forming such a magnetic field that the magnetic lines of force parallel with the inside wall of a treating chamber near the inside wall of a plasma treating chamber, and thereby decreasing the loss of the charged particles in the plasma. CONSTITUTION:Plural pieces of permanent magnets 7, 8, 9 are so disposed on the inside wall of the treating chamber 6 that the magnetic poles adjacent to each other have reverse polarities to parallel the magnetic lines of force 12 with the inside wall. Treating gases are supplied into the treating chamber 6 from nozzles 20 in this constitution and the inside of the treating chamber 6 is controlled to a prescribed pressure. The microwaves generated by a magnetron 3 are then introduced via a waveguide 2 into a cavity resonator 1 where the electromagnetic field thereof is intensified. These microwaves are radiated through a slot 4 and a transmission window 5 to the treating chamber 6 to form the plasma. The charged particles in the plasma are, therefore, captured by the magnetic lines of force 12 and make cyclotron motion. The loss of the plasma in the treating chamber 6 is thereby suppressed and the plasma is maintained at the high density. The plasma near the large-diameter semiconductor substrate 19 is stably maintained at the high density in this way and the uniform treatment of the substrate 19 at a high speed is possible.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a plasma processing apparatus that performs dry etching processing of semiconductor substrates, plasma CVD processing, etc. in the semiconductor device manufacturing process, and particularly relates to a plasma processing apparatus that performs high-density and uniform plasma processing. The present invention relates to a microwave plasma processing apparatus suitable for forming the present invention.

[Conventional technology]

For example, in dry etching processing, plasma processing equipment for semiconductor devices introduces processing gas into a plasma processing chamber (hereinafter simply referred to as processing chamber) in a vacuum atmosphere to form plasma, and processes the ionization and dissociation of the processing gas. by generating chemically highly reactive ions and radicals (neutral active species).

These active particles act physically or chemically to etch away a desired portion of the film to be processed on the semiconductor substrate, thereby forming a device pattern. In order to realize an etching process that is faithful to the mask pattern with less so-called side etching using such an apparatus, it is necessary to perform the process at a low pressure in order to increase the directionality of the movement of ions and radicals.

Furthermore, in order to improve the processing speed, it is necessary to increase the concentration of ions and radicals, and therefore it is necessary to form high-density plasma at a low processing gas pressure.

One of the technologies to meet these needs is a plasma generation method using microwaves.

In conventional technology that uses microwaves to generate plasma, even if the microwaves are introduced into a processing chamber where processing gas is kept at low pressure, the electric field strength of the microwaves is not sufficient to generate sufficient energy for the electrons in the plasma. Since no gas is supplied and the pressure is low, the collision frequency of electrons with gas molecules is low, making it difficult to efficiently generate plasma. For this reason, in the plasma generation method using microwaves, in order to obtain high-density plasma with low gas pressure, for example, as described in Japanese Patent Application Laid-Open No. 63-103088, the microwave is A microwave plasma processing device that uses a cavity resonator to strengthen the electromagnetic field strength and introduces this into the processing chamber through a slot provided on the end face of the cavity resonator on the processing chamber side to form high-density plasma. is publicly known.

[Problem to be solved by the invention]

The semiconductor substrate that is the target of microwave plasma processing is
There is a trend toward larger diameters to improve productivity, and 150
φ, 200φ are in practical use.

In order to plasma-process such a large-diameter semiconductor substrate, it is necessary to form large-diameter plasma.

However, in the above-mentioned conventional technology, no consideration is given to forming large-diameter plasma uniformly and stably at high density, and it is difficult to plasma-process large-diameter semiconductor substrates of φ200 or more at high speed, uniformly, and stably. The problem was that it was difficult.

Furthermore, for large-diameter semiconductor substrates, the amount of ions decreases due to a decrease in plasma density, making it difficult to achieve anisotropic etching with little side etching in dry etching.

The causes of the above problems will be discussed below.

In conventional technology, the uniformity of plasma processing is ±15%.
To achieve this below, let D be the outermost pitch diameter of the slots arranged in the cavity resonator, and H be the distance between the electrodes on which the semiconductor substrate is placed and the slots (electrode spacing), then D#
It was necessary to configure the processing chamber within the range of (1 to 3)H.

Therefore, in order to obtain large-diameter plasma, it is necessary to increase the pitch diameter of the outermost periphery of the slot.

Therefore, in order to ensure uniformity of processing, it was necessary to increase the electrode spacing H.

However, as the electrode spacing H increases, the loss of electrons and ions in the plasma to the processing chamber wall increases.

For this reason, not only the plasma density near the semiconductor substrate decreases, but also the plasma density decreases in the radial direction of the processing chamber, making the plasma density distribution near the semiconductor substrate non-uniform.

Furthermore, as the pitch diameter of the outermost circumference of the slot increases, the electric field strength of the microwave radiated from the slot becomes weaker, making it impossible to stably form plasma.

For these reasons, conventionally it has not been possible to form large-diameter plasma at high density, uniformly, and in a stable state.

The present invention has been made in view of the above-mentioned circumstances, and uses microwave technology that can process large-diameter semiconductor substrates at high speed and uniformly by forming large-diameter plasma in a high-density, uniform, and stable state. The purpose of the present invention is to provide a plasma processing apparatus.

[Means to solve the problem]

The above purpose is to provide a cavity resonator that increases the electromagnetic field strength of the microwave immediately before introducing the microwave into the plasma processing chamber;
and a slot for radiating microwaves from the cavity resonator to the plasma processing chamber, and a plurality of magnets for forming a magnetic field near the inner wall of the plasma processing chamber, and the plurality of magnets are directed into the plasma processing chamber. This is achieved by arranging the magnetic poles such that each adjacent magnet has opposite polarity.

When carrying out the present invention, it is desirable to set the magnet arrangement so that the magnetic field is a multipolar cusp magnetic field.

Furthermore, it is desirable that the magnetic flux density at each magnetic pole position in the processing chamber be set so as to form an electron cyclotron resonance magnetic field.

[Effect]

When a magnetic field exists, charged particles such as electrons and ions in plasma are subjected to Lorentz force in a direction perpendicular to the direction of movement of the charged particles and the direction of the magnetic field, so they perform cyclotron motion around the magnetic lines of force. By creating a magnetic field parallel to the wall, charged particles moving from the plasma toward the processing chamber wall perform cyclotron motion with a radius inversely proportional to the magnitude of the magnetic flux density.
Diffusion loss of charged particles to the inner wall of the processing chamber is suppressed.

If the polarities of the adjacent magnetic poles are opposite as in the above-described configuration, the lines of magnetic force coming out of one magnetic pole will flow into the adjacent magnetic pole along the inner wall of the processing chamber without deeply entering the inside of the processing chamber. Therefore, a strong magnetic field parallel to the inner wall is formed near the inner wall of the processing chamber, and a magnetic field formed near the center of the processing chamber has a low magnetic flux density.

As a result, the effect of suppressing the diffusion of charged particles in the plasma is small near the center of the processing chamber, so the density distribution of plasma density in the slot opening area and the non-opening area near the slot will be reduced until it reaches the vicinity of the semiconductor substrate. equalized by

In addition, near the inner wall of the processing chamber, the loss of charged particles to the inner wall of the processing chamber is suppressed by the magnetic field parallel to the inner wall.

As a result, even if the slot pitch diameter and electrode spacing are widened to obtain large-diameter plasma, the decrease in plasma density in the radial direction of the processing chamber is alleviated.

A uniform plasma with a large diameter can be formed.

Furthermore, since the loss of charged particles is suppressed, plasma can be maintained at high density.

Furthermore, the magnetic flux density at each magnetic pole position in the processing chamber satisfies electron cyclotron resonance (ECR) conditions (when the microwave frequency is 2.45 GHz).

At this position, the electron cyclotron frequency and the microwave frequency match and an electron cyclotron resonance phenomenon is induced, so the microwave energy is efficiently absorbed by the electrons and the plasma is stabilized. can be formed in the state.

〔Example〕

Next, a first embodiment will be described with reference to FIGS. 1 to 6.

FIG. 1 is a longitudinal sectional view showing a first embodiment of a microwave plasma processing apparatus according to the present invention. FIGS. 2, 3, and 4 are an AA sectional view of the cavity resonator 1, a BB sectional view, and a CC sectional view of the processing chamber in FIG. 1, respectively. In FIG.

A magnetron 3, which is a 2.45 GHz microwave generator, is attached to the cavity resonator 1 via a waveguide 2. The cavity resonator 1 is designed to have a certain resonant mode, and when the circular cavity resonator is in the TMo mode, the slots 4 are arranged in a concentric arc shape in the direction transverse to the electric field, as shown in FIG. Configure.

The cavity resonator 1 shown in FIG.
The cavity resonator 1 under atmospheric pressure and the processing chamber 6 under vacuum atmosphere are connected to the processing chamber 6 through a microwave transmission window 5.
Separated by .

On the side surface of the processing chamber 6, permanent magnets 7, 8.9 are arranged on the atmosphere side, and a yoke 10, 11 made of a material with high magnetic permeability is arranged on the outer periphery of these permanent magnets.

Here, the magnetic poles of the permanent magnets 7, 8, and 9 are arranged so that the polarities adjacent to N, S, and N on the inner wall side of the processing chamber are opposite to each other. Therefore, a magnetic field is formed as shown by magnetic field lines 12.

Also, permanent magnet 7. The arrangement of magnets 8 and 9 in the cross section of the processing chamber is such that an even number of magnets are arranged as shown in FIGS. 3 and 4, respectively, and adjacent magnets have opposite polarities. Therefore, in the cross section of the processing chamber 6, a multi-pole cusp magnetic field is formed as shown by magnetic lines of force 13 and 14. Here, permanent magnets 7, 8 .
9 is E with a magnetic flux density of 8750 at each magnetic pole position in the processing chamber.
It is composed of a magnet with a high residual magnetic flux density that satisfies CR conditions.

Inside the processing chamber 6 in FIG.
The insulator 16 is installed to be electrically insulated from the ground potential, and the insulator 16 is covered with a metal cover 17 at the ground potential. A high frequency power source 18 is connected to the lower electrode 15, and the semiconductor substrate 19 to be plasma processed is connected to the lower electrode 15.
placed on top. Further, a gas supply device (not shown) is connected to the processing chamber 6, and processing gas is supplied from a gas supply nozzle 20, and after reacting, the supplied processing gas is exhausted from an exhaust port 21 by an exhaust device (not shown). . At this time, the pressure in the processing chamber 6 is controlled to a predetermined pressure by a pressure regulator (not shown).

The operation when performing the tri-etching process on the semiconductor substrate 19 using the above configuration will be described.

When dry etching an AQ alloy film, for example, CO2-+BCQ3 is used as a processing gas, and is supplied from the gas supply nozzle 20 into the processing chamber 6, and the processing chamber 6 is heated at a predetermined pressure of 10° to 10- 'Pa to control. Next, a 2.45 GHz microwave is generated from the magnetron 3 and introduced into the cavity resonator 1 via the waveguide 2. The microwave introduced into the cavity resonator 1 is 1, for example, T
Mo mode resonates and its electromagnetic field is intensified and radiated from the slot 4 to the processing chamber 6, thereby forming plasma in the processing chamber 6.

Charged particles in plasma, especially electrons that move at a thermal velocity two orders of magnitude higher than that of ions, are captured by the magnetic field lines 12, 13, and 14 shown in Figures 1, 3, and 4, and perform cyclotron motion. , loss of electrons to the microwave transmission window 5 and the inner wall of the processing chamber 6 is suppressed. Thereby, the plasma in the processing chamber is maintained at a high density.

Therefore, even if the distance H from the microwave transmission window 5 to the electrode 15 is increased in order to obtain large-diameter plasma, the plasma density near the semiconductor substrate can not only be maintained at a high density, but also the loss of charged particles to the processing chamber wall can be reduced. This suppresses the decrease in plasma density in the radial direction of the processing chamber, thereby making the distribution of plasma density near the semiconductor substrate uniform.

Furthermore, by utilizing the electron cyclotron resonance phenomenon at each magnetic pole position within the processing chamber, plasma can be stably formed.

FIG. 5 is a chart showing the relationship between the distance H (see FIG. 1) and the ion current density flowing into the electrode.

The curve connecting black circles with solid lines is the actual measured value in this example.

Further, the actual measured values when the permanent magnets 7, 8, and 9 are removed from the device of this embodiment and the state is similar to that of the conventional example are a curve in which white circles are connected with chain lines.

According to this example, since the plasma density near the semiconductor substrate can be maintained high, the ion current density is high, especially when the distance H is 1
It is 2 to 3 times more effective in maintaining high-density plasma when it is wide from 00 to 150 m.

FIG. 6 is a chart showing the relationship between the distance from the center of the electrode and the density of ion current flowing into the electrode, where the solid line connecting the black circles is for the present example, and the chain line connecting the white circles is for the permanent magnets 7, 8, etc. described above. 9
0, which is an actual value measured in a device equivalent to the conventional example with the
The ion current density distribution in this example not only has a large absolute amount of ion current density, but also suppresses the decrease in ion current density around the electrode, achieving high uniformity even in a large diameter electrode of φ200 m5. be able to.

According to this embodiment, the plasma near a large-diameter semiconductor substrate of 200φ or more can be maintained in a high-density and stable state, which has the effect of processing large-diameter semiconductor substrates at high speed and uniformly. .

Furthermore, in dry etching, since the amount of ions that enter the semiconductor substrate from the plasma in a straight line is high, it is effective in easily achieving anisotropic etching with less side etching.

FIG. 7 is a longitudinal sectional view showing a second embodiment of the microwave plasma processing apparatus according to the present invention. Figures 8 and 9
The figures show the DD cross section and EE cross section of the processing chamber 6 in FIG. 7, respectively.
It is a cross section. In FIG. 7, FIG. 8, and FIG. 9, the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals. The polarities of the permanent magnets 7° 8 on the wall side of the processing chamber are opposite to each other, but as shown in FIGS. 8, magnetic poles of the same polarity are adjacent to each other on the inner wall side of the processing chamber.

In this example, magnetic lines of force 12' are formed as shown in FIG. In the second embodiment having such a configuration, the same effects as in the first embodiment can be obtained through the same operation.

〔Effect of the invention〕

According to the present invention, a magnetic field is formed near the inner wall of the processing chamber in which magnetic lines of force are parallel to the inner wall of the plasma processing chamber, thereby suppressing the loss of charged particles in the plasma to the inner wall of the processing chamber.

Therefore, even if the area of loss of charged particles increases by increasing the slot pitch diameter and electrode spacing at the outermost periphery in order to obtain large-diameter plasma, it is necessary to maintain high density and uniform plasma near the large-diameter semiconductor substrate. Can be done. In addition, if a magnetic field with electron cyclotron resonance conditions is formed at each magnetic pole position near the processing chamber wall, even if the microwave electric field strength decreases due to the large slot pitch diameter at the outermost periphery in order to obtain large-diameter plasma, Since the energy in the microwave is efficiently absorbed by electrons in the plasma, a large-diameter plasma can be stably maintained.

Therefore, a large-diameter semiconductor substrate can be plasma-treated at high speed and with good uniformity, which is effective in improving productivity in semiconductor device manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of a microwave plasma processing apparatus according to the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. FIG. 4 is a CC sectional view of FIG. 1. FIGS. 5 and 6 are charts for explaining the effects of the first embodiment. FIG. 7 is a longitudinal sectional view showing a second embodiment of the microwave plasma processing apparatus according to the present invention, FIG. 8 is a DD sectional view of FIG. 7, and FIG. 9 is the same <EE sectional view. DESCRIPTION OF SYMBOLS 1... Cavity resonator, 2... Waveguide, 4-... Slot, 5... Microwave transmission window, 6... Processing chamber, 7,
8.9...Permanent magnet, 10.11...Yoke, 12
．． 13.14... Lines of magnetic force, 15... Lower electrode, 18
...High frequency power supply, 19...Semiconductor substrate. Figure 2 (Guidance)

Claims (3)

[Claims] 1. A plasma processing apparatus comprising: a plasma processing chamber; a means for introducing microwaves into the plasma processing chamber; a device for supplying a processing gas to the plasma processing chamber; and a means for evacuating the inside of the plasma processing chamber. A cavity resonator that increases the electromagnetic field strength of the microwave immediately before introducing the microwave into the plasma processing chamber, a slot that radiates the microwave from the cavity resonator to the plasma processing chamber, and a slot near the inner wall of the plasma processing chamber. A plurality of magnets that form a magnetic field are provided, and the plurality of magnets are arranged such that among the magnetic poles directed into the plasma processing chamber, adjacent magnetic poles have opposite polarities. A microwave plasma processing device featuring: 2. The microwave plasma processing apparatus according to claim 1, wherein the plurality of magnets are arranged so that the magnetic field formed near the inner wall of the plasma processing chamber is a multipolar cusp magnetic field. . 3. 2. The microwave plasma processing apparatus according to claim 1, wherein the magnetic flux density at each magnetic pole position in the plasma processing chamber is set so as to form a magnetic field that satisfies electron cyclotron resonance conditions.