JPH0449174Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention is a plasma CVD method using high-frequency discharge.
The present invention relates to a high frequency discharge plasma processing apparatus applied to a sputtering apparatus, a sputtering apparatus, a plasma dry etching apparatus, a plasma cleaning apparatus, etc.

(B) Conventional Technology In recent years, many semiconductor manufacturing process devices that utilize plasma reactions have been developed as the process becomes drier. Among these, high frequency discharge is often used as a method for generating plasma.

In addition, with the spread of CVD equipment that utilizes plasma reactions, the large-area processing capabilities of plasma processing equipment are becoming increasingly important due to larger-area film formation and the use of dry etching for microfabrication technology for these films. There was a need to measure improvement.

In conventional plasma processing equipment, the discharge chamber is cubic, and the electrodes are also square.
The electric field distribution for generating plasma is not uniform between opposing electrodes. Furthermore, in conventional chambers that confine plasma with walls made of metal such as stainless steel, high-frequency discharge occurs mainly between the power supply electrode and the ground electrode. Even in between, it occurs slightly. Therefore, in such conventional devices, the plasma generated between the electrodes becomes non-uniform due to the above-mentioned non-uniform electric field between the electrodes and discharge between the feeding electrode and the wall surface.
Etching equipment has drawbacks such as polymer adhesion and contamination of impurities due to back spatter. These drawbacks become more noticeable as the device becomes larger.

In order to solve these drawbacks, it has been proposed to replace the entire surface of the chamber with an electrode, as disclosed in Japanese Patent Application Laid-Open No. 15977/1983. FIG. 2 shows its basic structure, in which 1 is a power supply electrode, 2 is a ground electrode provided opposite to the power supply electrode 1, 3 is a wall made of an insulating material or a metal material whose inner surface is covered with an insulator, 4 is a capacitive load, 5 is a high frequency power source, and 6 is a sample to be subjected to plasma treatment. That is, in such prior art, by using an insulating material for the wall surface 3 of the chamber, it is possible to suppress the discharge between the power supply electrode 1 and the wall surface 3 as much as possible,
In addition, as shown in the figure, by extending both electrodes 1 and 2 to the wall surface 3 and making the electric field distribution uniform throughout the chamber, even if the sample 6 has a large area, the surface of the sample 6 can be uniformly spread. Can be exposed to plasma.

However, although such prior art allows plasma to be distributed uniformly between the electrodes, the discharge at high frequencies is unstable, so slight fluctuations in gas pressure or discharge power may cause the discharge to stop, or the discharge may stop when the plasma is in contact with the plasma. Phenomena appear when abnormal discharge occurs where the discharge concentrates on a protrusion within the chamber, or when the generated plasma concentrates on the outlet hole for reactant gas or inert gas. If these phenomena occur, the density of the plasma generated between the electrodes will fluctuate spatially and temporally, and in the case of film forming equipment, abnormal generation of fine particles, film adhesion to the chamber wall 3, and etching equipment may be affected. If this is the case, the etching rate will drop significantly and polymer will be generated, resulting in the problem that good plasma processing cannot be performed.

(c) Problems to be solved by the invention The present invention solves the above-mentioned problem of unstable discharge at high frequencies and performs good plasma processing by performing stable discharge.

(d) Means for solving the problem The present invention consists of a power feeding electrode and a grounding electrode that are arranged opposite to each other to induce plasma discharge, and an insulating material provided between the electrodes to confine the plasma induced. In order to solve the above-mentioned problem, the area of the ground electrode is equal to the area of the power supply electrode. It is characterized by being larger.

(E) Effect As described above, in the high frequency discharge plasma processing apparatus of the present invention, by making the area of the ground electrode larger than the area of the power supply electrode, the potential gradient between the electrodes is largely biased toward the power supply electrode side.

(f) Embodiment FIG. 1a is a cross-sectional view showing an embodiment of the present invention, and the same parts as those in the prior art shown in FIG. 2 are given the same numbers, and their explanation will be omitted. That is, the difference from the prior art is that, as shown in FIG. 1b, the ground electrode 2
The electrode surface is made to stand up along the wall surface 3, and the effective electrode area of the ground electrode 2 is made larger than the area of the power supply electrode 1.

The inside of the chamber of the capacitively coupled plasma processing apparatus of the present invention and the conventional apparatus is 0.1 Torr by means of reduced pressure evacuation means such as a rotary pump (not shown in the figure).
After reducing the pressure to below, a source gas is introduced into the film forming apparatus and an etchant gas is introduced into the etching apparatus until the pressure reaches about 0.1 to 10 Torr. When a high frequency voltage of 100 KHz or more is applied to the power supply electrode 1 by the high frequency power supply 5, a discharge occurs between the electrodes and plasma is generated between the electrodes. At this time, a dark space called a dark space is generated between the electrodes near the power supply electrode 1 and the ground electrode 2, and chemically active species (radical species) are mainly generated here. Contributes to various reactions. On the other hand, the DC component potential difference in the dark space on the power supply electrode 1 side is V ₁ , the DC component potential difference in the dark space on the ground electrode 2 side is V ₂ , and the areas of the power supply electrode 1 and ground electrode 2 are A ₁ and A ₂ , respectively. Then, in general, the formula V ₁ /V ₂ = (A ₂ /A ₁ ) ⁴ holds true, and between the electrodes, the electrons with low mass in the generated plasma move in response to the high frequency, and are transferred to the ground electrode 2. When it reaches the power supply electrode 1, it flows directly to the ground, and when it reaches the power supply electrode 1, it is accumulated in the capacitive load 4. Therefore, the power feeding electrode 1 has a negative DC potential, and at the same time has a positive DC potential because there are fewer electrons between the electrodes and positive ions with heavy mass remain. Furthermore, since the ground electrode 2 has an OV potential, both electrodes have a lower potential than the potential between the electrodes. That is, the above-mentioned V ₁ and V ₂ have potentials of opposite polarity. Therefore, according to the above equation, in the conventional device in which the feeding electrode 1 and the grounding electrode 2 have the same area, the potential difference between the two dark spaces becomes V ₁ =V ₂ , and the potential gradients between the electrodes are approximately equal. Therefore, since discharge occurs in both directions of the power supply electrode 1 and the ground electrode 2, it is assumed that the discharge becomes unstable.

Therefore, in the device of the present invention, by making the area of the ground electrode 2 larger than the area of the power supply electrode 1, the above equation becomes V ₁ ≫ V ₂ , and the potential gradient between the electrodes is largely biased toward the power supply electrode 1 side. , discharge tends to occur only in one direction. Therefore, the discharge of the device of the present invention is performed stably in one direction. As a result, phenomena such as stoppage, concentration, and fluctuation of discharge do not occur in the device of the present invention, and in the film forming device,
A uniform, high-quality film can be obtained with good reproducibility, and the etching apparatus can perform desired etching uniformly and with good reproducibility.

Further, in this embodiment, the chamber is cylindrical, but the same effect can be obtained even if the chamber is cubic.

FIG. 3 shows another embodiment of the device of the present invention. As shown in the figure, in this embodiment, the area of the electrode raised along the wall surface 3 of the ground electrode 2 is tapered to make contact with the plasma, thereby further expanding the electrode area and obtaining a greater effect. By preventing the concentration of discharge, more stable discharge can be achieved.

FIG. 4 shows still another embodiment of the device of the present invention. In this embodiment, the portion along the wall surface 3 of the ground electrode 2 that comes into contact with the raised plasma is made uneven to increase the effective electrode area.

FIG. 5 shows still another embodiment of the device of the present invention. In this embodiment, the ground electrode 2 is raised along the wall surface 3, and a mesh-shaped electrode 21 is placed between the power supply electrode 1 and the sample 6.
In addition, by connecting the surface along the wall surface 3 of the grounding electrode 2 to the ground potential, the high frequency discharge is connected to the surface along the wall surface 3 of the feeding electrode 1.
This is done at the portions along the wall surface 3 of the mesh-like electrode 21 and the ground electrode 2. As a result, even in a plasma processing apparatus in which a mesh-shaped electrode is used and the sample is not directly exposed to plasma, the area of the ground electrode 2 becomes larger than the area of the power supply electrode 1, and stable discharge can be performed.

In all of the above embodiments, the wall surface 3 is only the side surface of the chamber, but the wall surface 3 may cover the entire chamber including both electrodes.

(g) Effects of the invention As is clear from the above explanation, the device of the present invention makes the area of the ground electrode larger than the area of the power supply electrode, and by biasing the potential gradient between the electrodes toward the power supply electrode side, stable discharge can be achieved. Since it can be obtained, good plasma processing can be performed. That is, when the device of the present invention is used in a film forming device, a uniform and high-quality film can be obtained with good reproducibility, and when the device of the present invention is used in an etching device, the desired etching can be performed uniformly and reproducibly. can do well.

[Brief explanation of drawings]

Figure 1 shows an embodiment of the device of the present invention;
is a cross-sectional view of the same, b is an external view of the ground electrode, and the second
The figure is a sectional view showing a conventional device, and FIGS. 3 to 5 are sectional views showing different embodiments of the device of the present invention. 1... Power supply electrode, 2... Ground electrode, 3... Wall surface, 4... Capacitive load, 5... High frequency power supply, 6...
sample.

Claims (1)

[Scope of utility model registration request] A feeding electrode and a grounding electrode arranged to face each other and inducing plasma discharge, an insulating wall surface provided between the electrodes to confine the plasma induced, and a capacitive load and a high frequency wave connected to the feeding electrode. A high-frequency discharge plasma processing apparatus, comprising: a power source, wherein the area of the ground electrode is larger than the area of the power supply electrode.