JPH07106097A - Plasma processing device - Google Patents

Abstract

PURPOSE:To provide a plasma processing device, which can perform the etching to a substrate at a high speed without generating charge-up of a substrate and damage due to the charge-up. CONSTITUTION:RF power sources 15, 19 are respectively connected to parallel flat electrodes 11, 12 arranged in a vacuum vessel 20. A substrate 16 is placed on the electrode 11, and furthermore, a phase shifter 40 is connected to the power sources 15, 19 so that the RF power to be respectively applied to the electrode 11, 12 have a phase difference at 180 degree from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to an apparatus for plasma processing materials such as metals, semiconductors, and insulators that make up semiconductor products and other electronic components.

[0002]

2. Description of the Related Art The present invention is not limited to semiconductor products, but if an integrated circuit of a semiconductor product is taken as an example, the degree of integration will be dramatically improved, and it will be possible to improve the degree of integration before film formation on a substrate. The etching method for cleaning the surface is also rapidly changed from wet etching using a solution to dry etching using an etching gas, and technical improvements are being energetically pursued. For example, the cylindrical electrode plasma processing equipment that was originally used had different processing speeds depending on the position where the substrate was placed, and the uniformity within the same substrate was not sufficient. Devices are the mainstream.

Further, the plasma processing apparatus using the parallel plate electrodes originally applied a high frequency to the electrode on which the substrate is not placed, but recently, in order to easily generate the bias voltage, the substrate is placed. A high frequency is applied to the placed electrode. This type of parallel plate electrode plasma processing apparatus is taken as a first conventional example and its schematic diagram is shown in FIG. In FIG. 6, an electrode 1 and an electrode 2 as parallel plate electrodes are arranged in parallel in a vacuum chamber 10 so as to face each other.
The electrode 2 is connected to the ground, the substrate 6 to be cleaned is placed on the electrode 1, and the RF electrode 5 is connected to the vacuum chamber 10 by being insulated from the vacuum chamber 10. The inner wall of the vacuum chamber 10 is used as the ground electrode 3.

To explain this effect, when the vacuum chamber 10 is evacuated and an etching gas is introduced and RF power is applied from the RF electrode 5 to the electrode 1, plasma is generated between the electrode 1 and the electrode 2. , The ions in the plasma are accelerated by the bias voltage at the electrode 1 and collide with the substrate 6,
The substrate 6 is etched due to the sputtering effect.

However, the plasma processing apparatus according to the first conventional example generally has a low etching rate and is not suitable as a production means. On the other hand, it is conceivable to increase the plasma density in order to increase the etching rate, but if the RF power applied for that purpose is increased, a high-density plasma is obtained and a bias voltage higher than necessary is generated in the electrode 1, The substrate 6 placed on the electrode 1 is charged up (electrostatic charge accumulation).

Although the mechanism of charge-up has not been fully clarified, the charge-up of the substrate itself is a serious problem in manufacturing integrated circuits. That is, as the degree of integration of the integrated circuit is improved, the thickness of the gate oxide film is thinned in the unit of nm. When the substrate on which many integrated circuits are formed is charged up, this charge destroys the gate oxide film, This is because the yield of integrated circuits is extremely reduced, which is called charge-up damage.

As a plasma processing apparatus for generating high-density plasma other than the above-mentioned high applied RF power, there is a second conventional example in which a magnetic field is superposed, and its schematic diagram is shown in FIG. This device is configured in exactly the same manner as the first conventional example, except that it is located close to the electrode 2 outside the vacuum chamber 10.
A flat plate magnet 7 is arranged along with the rotating mechanism 8 in parallel with the electrodes 1 and 2. The flat plate magnet 7 forms a magnetic field perpendicular to the electric field between the electrodes 1 and 2, and is often rotated at the eccentric position of both magnetic poles. Then, the flat plate magnet 7 makes the magnetic field strength substantially uniform in the substrate 6.

In order to explain the operation of the second conventional example, the vacuum chamber 10 is evacuated and an etching gas is introduced to introduce R into the electrode 1.
When F power is applied, plasma is generated between the electrode 1 and the electrode 2, and the ions in the plasma are accelerated by the bias voltage at the electrode 1 and collide with the substrate 6.
Similar to the conventional example, the electrons in the plasma draw a cycloid curve in the direction of the vector product (vector E × vector B) of the electric field E between the electrodes 1 and 2 and the magnetic field B generated by the plate magnet 7. Since a drift motion is formed and the drift motion forms a closed locus, the frequency of ionization collisions between electrons and etching gas molecules is increased, and a high-density plasma is formed. Then, in order to prevent the distribution of the high density plasma from being biased, the rotating mechanism 8 rotates the plate magnet 7.

However, in the second conventional example, the high density plasma is liable to be always formed in the vicinity of the central axes of the electrodes 1 and 2, so that the substrate 6 is easily subjected to nonuniform etching, and the nonuniform plasma density causes It is easy to accompany the expected charge-up.

[0010]

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 plasma processing apparatus capable of obtaining a high etching rate and not causing charge-up damage to a substrate.

[0011]

SUMMARY OF THE INVENTION In the plasma processing apparatus in which a gas for plasma generation is introduced into a vacuum chamber and a pair of parallel plate electrodes are arranged, one of the first electrodes is provided. Is mounted with a substrate and is connected to a high frequency power source for biasing the substrate, and the other second
A high-frequency power source for plasma generation is connected to the electrodes, and when performing plasma processing on the substrate, the first
The plasma processing apparatus is characterized in that high-frequency power is applied to the electrode and the second electrode so as to have a phase difference of 180 degrees from each other.

[0012]

In the plasma processing apparatus in which the pair of parallel plate electrodes are arranged, the high frequency power is applied to the first electrode (on which the substrate is placed) and the second electrode so as to have a phase difference of 180 degrees from each other. High-density plasma is generated uniformly between the electrodes,
A high etching rate can be obtained. On the other hand, high-frequency power can be applied to the first electrode on which the substrate is mounted so that a bias voltage higher than the bias voltage required for etching is not generated, so that charge-up does not occur on the substrate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A plasma processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

That is, FIG. 1 is a schematic diagram of the plasma processing apparatus according to the first embodiment. In the vacuum chamber 20, electrodes 11 and 12 as parallel plate electrodes are arranged in parallel and face each other. Moreover, the area of the electrode 12 is 2.5 times the area of the electrode 11. This is cathode coupling so that the ions in the generated plasma are
This is because it is accelerated by the bias voltage of 1. The inner wall of the vacuum chamber 20 is used as the ground electrode 13, but this is the same as in the conventional example.

The electrode 12 has an RF for plasma generation.
A power source 19 (frequency 13.56 MHz) is connected to the vacuum chamber 20 via an insulator 17, and an RF for biasing the substrate 16 to the electrode 11 on which the substrate 16 is placed.
A power supply 15 (frequency 13.56 MHz) is connected to the vacuum chamber 20 via an insulator 14. The RF power source 15 and the RF power source 19 are connected to the phase shifter 40 so that the applied RF power has a phase difference of 180 degrees between the electrode 11 and the electrode 12, and the signal from the phase shifter 40 is transmitted. Each power supply is used for amplification. The phase difference is 1
The phase difference is fixed at 180 degrees because the etching rate and the etching uniformity are best when the angle is 80 degrees.

Furthermore, in order to make the bias applied to the substrate 16 uniform and to avoid metal contamination of the substrate 16 by the metal electrode 11, a dielectric quartz (SiO ₂ ) is provided between the electrode 11 and the substrate 16. ) The plate 18 is interposed.

The plasma processing apparatus according to the first embodiment of the present invention is constructed as described above. Next, its operation will be described.

After the inside of the vacuum chamber 20 is evacuated by a vacuum pump (not shown), argon (Ar) as an etching gas is introduced from an introduction pipe (not shown). The gas pressure in the vacuum chamber 20 was adjusted to 7 by adjusting the inflow rate of argon gas and the exhaust rate.
It is Pa. The gas pressure is set to a low pressure of 7 Pa so that the ions in the generated plasma sufficiently reach the small holes (for example, diameter 5 μmφ) existing on the surface of the substrate 16 to enable complete etching. . And gas pressure 7
RF power is applied while maintaining Pa. At this time, phase shifter 4
By 0, the RF power is applied to the electrode 11 and the electrode 12 with a phase difference of 180 degrees from each other, but the RF power is applied to the electrode 11 on which the substrate 16 is mounted so that an unnecessary bias voltage is not generated. It is controlled and applied by the RF power supply 15.

Phase difference 180 between electrode 11 and electrode 12
High density argon plasma is uniformly generated between both electrodes by the applied RF power of 10 degrees, and the argon ions (Ar ⁺ ) in the plasma are accelerated by the bias voltage of the electrode 11 and collide with the substrate 16, thereby Is etched at a high etching rate. In addition, the product of the etching becomes a gas and is exhausted. Alternatively, it adheres to the wall surface in the vacuum chamber 20.

On the other hand, in addition to the controlled bias voltage on the electrode 11, there is an effect of the alumina plate 18 interposed between the electrode 11 and the substrate 16, so that an appropriate bias is uniformly applied to the substrate 16. Therefore, the substrate 16 is not charged up and is not damaged thereby.

FIG. 4 is a diagram comparing the etching rates of a substrate having a diameter of 200 mm for the plasma processing apparatus according to the present embodiment and the plasma processing apparatus according to the first conventional example, which are applied to both the substrate mounting electrodes 1 and 11. The RF power is the same for comparison. In FIG. 4, the vertical axis represents the etching rate, the horizontal axis represents the position within the substrate along the diameter, the solid line A in the figure represents the etching rate of this embodiment, and the broken line B represents the etching rate of the first conventional example. As is apparent from FIG. 4, the plasma processing apparatus according to this embodiment exhibits an etching rate about three times that of the plasma processing apparatus according to the first conventional example.

Further, FIG. 5 is a diagram comparing the degree of charge-up to the substrate when the substrate having the diameter of 200 mmφ is similarly plasma-processed between this embodiment, the first conventional example and the second conventional example. This is a comparison for the case where almost the same etching rate is obtained. In FIG. 5, the vertical axis represents the degree of charge-up, and the horizontal axis represents the position within the substrate along the diameter. In the figure, a solid line A is the charge-up of this embodiment, a broken line B is the first conventional example, and a chain double-dashed line C is the second conventional example.
As is apparent from FIG. 5, charge-up is recognized in the first conventional example and the second conventional example, whereas no charge-up is recognized in this embodiment.

FIG. 2 is a schematic diagram of a plasma processing apparatus according to a second embodiment of the present invention. This embodiment has almost the same configuration as that of the first embodiment. Therefore, the same parts as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The difference between this embodiment and the first embodiment is that
A cylindrical ground electrode 22 is installed around the electrodes 11 and 12 which are parallel plate electrodes so as to be vertically movable as indicated by an arrow with a gap. In order to explain its action, most of the substances produced by etching are exhausted, but those which are not exhausted are trapped by the cylindrical ground electrode 22, so that the inner wall of the vacuum chamber 20 is contaminated by the deposition of the etching products. Can be prevented.

FIG. 3 is a schematic diagram of a plasma processing apparatus according to the third embodiment of the present invention. Since this embodiment is also configured almost the same as the first embodiment, the same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The difference of this embodiment from the first embodiment is that
In the first embodiment, a pair of electrodes 31, 32 are embedded in the alumina plate 18 interposed between the electrode 11 and the substrate 16 and connected to a DC power source 33 outside the vacuum chamber 20 to electrostatic chuck. Is being configured.

To explain this effect, a Coulomb force acts between the substrate 16 and the alumina plate 18 due to the electric charge induced on the surface of the alumina plate 18 by the DC electric field generated by the electrodes 31 and 32, and the substrate 16 and the alumina plate 18 are separated from each other. In close contact. The floating potential of the DC power source with respect to RF does not affect the plasma processing at all.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, although argon is used as the etching gas in each of the above embodiments, a rare gas other than argon suitable for etching, such as neon, krypton, or xenon, can be used.
Reactive etching gases such as ₄ and CCl ₄ may also be used.

In each embodiment, the high frequency power applied to the parallel plate electrodes has a frequency of 13.
Although a high frequency of 56 MHz is adopted, needless to say, it is not limited to 13.56 MHz as long as it is a high frequency suitable for use in etching.

In each embodiment, the electrode 11 and the substrate are
A quartz plate 18 is used as a dielectric to be interposed between the plate 16 and the plate 16.
Used for other known dielectrics such as alumina.
(Al ₂ O₃ ) It may be a plate.

Further, in the second embodiment, the cylindrical ground electrode 22 is adopted to capture the etching products, but this may be used as a cylindrical mesh electrode.

In each of the embodiments, the plasma processing apparatus of the present invention has been described as being used in an etching process for cleaning a substrate, but other plasma processing, for example, charge-up damage is also serious. It can also be applied to an ashing process of various resist films on various substrates.

[0034]

As described above, according to the plasma processing apparatus of the present invention, the pair of parallel plate electrodes are connected to each other by 180 °.
Since the high frequency power having a phase difference of 10 degrees can be applied and the high frequency power can be applied to the electrode on which the substrate is mounted by controlling so that an unnecessary bias voltage is not generated, the plasma processing apparatus of the present invention can For example, a high-density plasma can be obtained and the substrate can be etched at high speed, and the substrate will not be charged up or damaged due to it.

[Brief description of drawings]

FIG. 1 is a schematic view of a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic view of a plasma processing apparatus according to a third embodiment of the present invention.

FIG. 4 is a diagram comparing the etching rates of the first embodiment of the present invention and the first conventional example.

FIG. 5 is a diagram comparing the degree of charge-up between the first embodiment of the present invention and the first conventional example and the second conventional example.

FIG. 6 is a schematic view of a plasma processing apparatus of a first conventional example.

FIG. 7 is a schematic view of a plasma processing apparatus of a second conventional example.

[Explanation of symbols]

 11 Parallel Plate Electrode 12 Parallel Plate Electrode 14 Insulator 15 RF Power Source 16 Substrate 17 Insulator 18 Dielectric 19 RF Power Source 20 Vacuum Chamber 40 Phase Shifter 22 Cylindrical Ground Electrode 31 Electrostatic Chuck Electrode 32 Electrostatic Chuck Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taro Nomura 2500 Hagizono, Chigasaki City, Kanagawa Japan Vacuum Technology Co., Ltd.

Claims (11)

[Claims] 1. A plasma processing apparatus in which a gas for plasma generation is introduced into a vacuum chamber and a pair of parallel plate electrodes are arranged, wherein a substrate is placed on one of the first electrodes and the substrate is placed on the first electrode. Is connected to a high frequency power source for biasing the second electrode, and the other second electrode is connected to a high frequency power source for plasma generation. When performing plasma processing on the substrate, the first electrode and the second electrode are connected. A plasma processing apparatus, wherein high-frequency power is applied so that the electrodes have a phase difference of 180 degrees from each other. 2. The plasma processing apparatus according to claim 1, wherein the high frequency power source connected to the first electrode and the high frequency power source connected to the second electrode both have a frequency of 13.56 MHz. 3. The plasma processing according to claim 1, wherein a phase shifter is connected to a high frequency power source connected to the first electrode and a high frequency power source connected to the second electrode. apparatus. 4. The plasma processing apparatus according to claim 1, wherein the area of the second electrode is 1 to 2.5 times the area of the first electrode. 5. The plasma processing apparatus according to claim 1, wherein a dielectric is interposed between the first electrode and the substrate placed on the first electrode. 6. The plasma processing apparatus according to claim 5, wherein the dielectric is alumina (Al ₂ O ₃ ). 7. The plasma processing apparatus according to claim 5, wherein the dielectric is quartz (SiO ₂ ). 8. The plasma processing apparatus according to claim 5, wherein the dielectric has embedded therein a pair of electrodes connected to a DC power source outside the vacuum chamber. 9. A cylindrical ground electrode is arranged so as to be vertically movable in the vacuum chamber with a gap between the space sandwiched between the first electrode and the second electrode. The plasma processing apparatus according to any one of claims 1 to 5. 10. The pressure of the plasma generating gas is 7
The plasma processing apparatus according to any one of claims 1 to 8, which has Pa or less. 11. The plasma processing apparatus according to claim 1, wherein the gas for generating plasma is argon (Ar).