JPH08195379A - Plasma processing method and device - Google Patents

Abstract

PURPOSE: To provide a plasma processing method where a work is processed with a plasma optimal in distribution and a plasma processing device which is capable of generating a plasma of high density in a comparatively high vacuum. CONSTITUTION: A first electrode 23 on which a substrate 24 is placed is provided inside a vacuum chamber 18, an electromagnetic induction coil 22 and a second electrode 25 are so installed as confront the first electrode 23, and a first high- frequency power supply 26 which applies a high-frequency voltage to the electromagnetic induction coil 22 and the second electrode 25 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus used for manufacturing semiconductors and the like, and more particularly to a plasma processing method using a specific plasma and capable of generating high density plasma at a relatively high vacuum degree. And a plasma processing apparatus excellent in distribution of plasma density.

[0002]

2. Description of the Related Art Recently, in response to miniaturization of semiconductor elements,
In order to realize processing of a high aspect ratio element in the dry etching technology and embedding of a high aspect ratio element in the plasma CVD technology, it is required that these plasma treatments be performed under a high degree of vacuum. . For example, in the case of dry etching, when high-density plasma is generated under a high degree of vacuum, collisions between ions and neutral radical particles in the ion sheath formed on the substrate surface are reduced, so the directionality of the ions is reduced. In addition, since the ionization degree is high, the ratio of the ion fluxes of the neutral radicals and the incident particles that reach the substrate is increased, and the different direction of etching is enhanced.

On the other hand, it is also important to control the ion energy reaching the substrate. If the ion energy is large, the selection ratio may be lowered, and the substrate may be physically or electrically damaged. Therefore, it is necessary to control the ion energy in order to perform optimum etching stably. .

As a conventional general plasma processing method, a method using capacitive coupling plasma and a method using inductive coupling plasma are general. An example of an apparatus to which the method using capacitively coupled plasma is applied is shown in FIG. In the figure, 1 is a vacuum container, in which the upper and lower openings of a tubular body 2 are sealed by an upper wall surface body 3 and a lower wall surface body 4,
Intake and exhaust holes and the like are provided on the side surface of the cylindrical body 2 as needed. 5 is an upper electrode arranged on the inner surface of the upper wall body 3, 6 is a lower electrode arranged on the inner surface of the lower wall body 4 so as to face the upper electrode 5, and 7 is mounted on the lower electrode 6. The substrate 8 placed is a high frequency power source. The operation of this device is to generate a capacitively-coupled plasma in the vacuum container 1 by applying a high frequency voltage from a high frequency power source 8 between the upper electrode 5 and the lower electrode 6. As the temperature rises, the probability of collision between electrons and ions decreases accordingly, making it difficult to generate high-density plasma at high vacuum.

On the other hand, the method using inductively coupled plasma can utilize high density plasma which can obtain a sufficient processing speed even at a high degree of vacuum. The apparatus to which the method using the inductively coupled plasma is applied generates a high frequency magnetic field in the vacuum container by passing a high frequency current through an electromagnetic induction coil provided in the vacuum container, and the induction electric field induced by the high frequency magnetic field is generated. Is generated in a vacuum container to accelerate electrons, and by increasing the current of the electromagnetic induction coil, it is possible to generate a high-density plasma capable of obtaining a sufficient processing speed even at a high degree of vacuum. However, there is a problem in plasma distribution as described later. Examples of devices using this type of electromagnetic induction coil include a cylindrical type as shown in FIG. 4 and a flat plate type as shown in FIG. 5, which will be described below. Since these two examples are completely the same except for the arrangement of the electromagnetic induction coil, they will be described with the same reference numerals.

4 and 5, a vacuum container 9 is formed by sealing the upper and lower openings of a cylindrical body 10 with an upper wall surface body 11 and a lower wall surface body 12, and if necessary, the cylindrical body. Intake and exhaust holes are provided on the side surface of 10. 13 is an electromagnetic induction coil, 14
Is an electrode arranged on the inner surface of the lower wall body 12, 15 is a substrate placed on the electrode 14, 16 is a first high frequency power supply, and 17 is a second high frequency power supply. A vacuum is generated by applying a high-frequency voltage from the first high-frequency power source 16 to the electromagnetic induction coil 13 while evacuating while introducing a suitable gas into the vacuum container 9 and maintaining the inside of the vacuum container 9 at a suitable pressure. Plasma is generated in the container 9, and the substrate 15 can be subjected to plasma processing such as etching, deposition and surface modification. At this time, if a high frequency voltage is applied to the electrode 14 from the second high frequency power supply 17, the ion energy reaching the substrate 15 can be controlled.

[0007]

However, in the method of performing plasma processing using capacitively coupled plasma, the problems of the capacitively coupled device shown in FIG. That is, in this apparatus, the probability of collision between electrons and ions decreases as the vacuum degree increases, and it is difficult to generate high-density plasma at a high vacuum degree, and a sufficient processing speed cannot be obtained. If the high frequency voltage is forcibly increased to increase the plasma density in order to improve this, the ion energy increases and the etching selectivity decreases, or the substrate is damaged. In addition, the method of performing plasma processing using inductively coupled plasma also directly shows the problems of the inductively coupled apparatus shown in FIGS. 4 and 5. That is, in this apparatus, electrons are accelerated in parallel with the substrate surface and along a closed arc, and the probability of accelerating electrons being lost on the wall surface of the vacuum container is reduced, so that high density plasma can be obtained. ,
On the other hand, there is a problem that it is difficult to obtain the optimum plasma distribution for the work piece.

In view of such conventional problems, the present invention is capable of generating a high-density plasma at a relatively high degree of vacuum and a plasma processing method based on an optimum plasma distribution for a workpiece. It is an object of the present invention to provide a plasma processing apparatus having an excellent plasma density distribution.

[0009]

[Means for Solving the Problems]

First means (method): Plasma in which inductive coupling and capacitive coupling are mixed is generated in a vacuum container, and the substrate is processed by the generated plasma.

Second means (apparatus): a first electrode for mounting a substrate provided in the vacuum container, and an electromagnetic induction provided on the wall surface of the vacuum container at a position facing the first electrode. A coil and a second electrode, and a first high-frequency power source that applies a high-frequency voltage to the electromagnetic induction coil and the second electrode, and generate a plasma in which inductive coupling and capacitive coupling are mixed in a vacuum container. It was done like this.

[0011]

Therefore, according to the present invention, the inductively coupled plasma formed by the electromagnetic induction coil and the capacitively coupled plasma formed by the first and second electrodes are mixed, and the electromagnetic induction coil and the first and second electrodes are formed. By adjusting and optimizing the configuration of the electrode of, it is possible to obtain the optimum plasma distribution for the workpiece. Further, when a high frequency voltage is applied to the first electrode from the second high frequency power supply, the ion energy reaching the substrate can be controlled.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, in which 18 is a vacuum container in which the upper and lower openings of a tubular body 19 are sealed by an upper wall surface body 20 and a lower wall surface body 21,
Intake and exhaust holes and the like are provided on the side surface of the tubular body 19 as required. 22 is an electromagnetic induction coil having a diameter of 25 cm and a number of turns of 2; 23 is a first electrode disposed near the inner surface of the lower wall body 21;
Is a substrate placed on the first electrode 23, 25 is a second electrode having an area of about 48πcm ² provided in the inner peripheral portion of the electromagnetic induction coil 22, and 26 is a first high frequency power source Induction coil 22
To the second electrode 25 as shown. In addition,
27 is a second high frequency power supply, which is connected to the first electrode 23.

Next, the operation will be described. Argon gas of 30 SCCM is introduced into the vacuum container 18 and evacuated.
1000W from the first high frequency power supply 26 while maintaining the pressure of Torr
When the power is turned on, plasma is generated in the vacuum container 18. FIG. 2 shows the distribution of the ion saturation current density on the substrate 24 at this time. FIG. 2 (a) shows the state of this embodiment, and FIG.
Shows the state of the conventional example shown in FIG. As is clear from this figure, high-density plasma is obtained in both FIGS. 2 (a) and 2 (b), but the plasma distribution of this embodiment is the substrate 24.
The values are almost uniform at all positions, and the results are very good.However, in the conventional one, the inductive coupling property is dominant, and the maximum value is near the center of the substrate 24, which is a characteristic of the inductive coupling type discharge. The distribution is such that the plasma distribution is non-uniform. In this embodiment, the electromagnetic induction coil
The inductive coupling by 22 is mainly applied to the second electrode.
Since a plasma having mixed capacitive coupling due to 25 is generated, it is possible to achieve high uniformity of capacitive coupling discharge while maintaining high plasma density of inductive coupling discharge. It is possible to obtain a uniform plasma distribution.

Next, an experimental example in which the silicon oxide film is etched will be described. The plasma processing apparatus shown in FIG. 1 was used for the experiment. CHF ₃ 50SCC in the vacuum container 18
While introducing M and evacuating, while maintaining the pressure in the vacuum container 18 at 50 mTorr, 600 W is supplied from the first high frequency power supply 26 and at the same time 300 W is supplied from the second high frequency power supply 27 to the first electrode 23.
Turn on the power. An experiment was conducted using a substrate 24 having a silicon oxide film grown on a silicon substrate.
As a result, the etching rate of the silicon oxide film is 2500Å /
Although the etching rate was slightly lower than the etching rate in the conventional configuration shown in FIG. 3, the present example had a better result in terms of etching uniformity. Further, as a result of etching the polysilicon under the conditions of etching the silicon oxide film, the etching rate in the structure of this example is 450Å
/ Min, and 2000 Å / min in the case of the conventional configuration. It was found that the selection ratio of the silicon oxide film to polysilicon is greatly improved by using the configuration of this embodiment.

As described above, in the conventional inductively coupled discharge, the electrons are accelerated by the inductive electric field generated in the vacuum container along the closed arc, which is parallel to the substrate surface, and the electrons are accelerated on the wall surface of the vacuum container. High-density plasma can be obtained because the probability of accelerating electron loss is reduced, but on the other hand, the number of electrons with very high energy is large and the dissociation of the etching gas progresses extremely, so that fluorine radicals that etch polysilicon are removed. Since a large amount is generated, the etching selectivity for polysilicon in the etching of the silicon oxide film is lowered.

However, in the plasma of this embodiment in which the inductive coupling and the capacitive coupling are mixed, the electrons are parallel to the substrate surface and are accelerated along a closed arc, and at the same time, they are perpendicular to the substrate surface. Electrons with high energy collide with the electrode and are more likely to be lost because they are accelerated in any direction. As a result, it is considered that generation of fluorine radicals was suppressed and a high selection ratio was obtained.

With this configuration, it is possible to obtain the optimum plasma distribution for the workpiece.

[0018]

According to the present invention, it is possible to perform uniform plasma treatment on a workpiece by a method of performing plasma treatment with plasma having a mixture of inductive coupling and capacitive coupling. Optimum for the work piece by adjusting and optimizing the electromagnetic induction coil that generates the coupling plasma, the first and second electrodes that generate the capacitive coupling plasma, and the first and second high frequency power supplies. It is possible to realize an apparatus that obtains various plasma distributions.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of a plasma processing apparatus of the present invention.

FIG. 2 is a characteristic curve diagram for explaining plasma distribution states of the plasma processing apparatus of the present invention and a conventional plasma processing apparatus.

FIG. 3 is a perspective view showing an example of a conventional plasma processing apparatus.

FIG. 4 is a perspective view showing another example of a conventional plasma processing apparatus.

FIG. 5 is a perspective view showing still another example of the conventional plasma processing apparatus.

[Explanation of symbols]

1, 9, 18 ... Vacuum container, 6, 14, 23 ... First electrode,
7, 15, 24 ... Substrate, 5, 25 ... Second electrode, 13, 22 ...
Electromagnetic induction coil, 16, 26 ... First high frequency power supply, 17, 27
… Second high frequency power supply.

Claims (2)

[Claims] 1. A plasma processing method comprising: generating plasma in which inductive coupling and capacitive coupling are mixed in a vacuum container, and processing the substrate with the generated plasma. 2. A first electrode for mounting a substrate provided in a vacuum container, and an electromagnetic induction coil and a second electrode provided on a wall surface of the vacuum container at a position facing the first electrode. And a first high-frequency power source for applying a high-frequency voltage to the electromagnetic induction coil and the second electrode, and generate a plasma having both inductive coupling and capacitive coupling in a vacuum container. Processing equipment.