JPH0982491A - Surface treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce plasma efficiently by furnishing an electrode surface parallel with a sample, and inserting an antenna between the two so that high frequency waves to produce plasma flow. SOLUTION: Electrons and ions in a plasma produced in a vacuum vessel make spiral motions round a magnetic force generated by a magnet 9. When a high frequency voltage is impressed on a sample 3 by a bias power supply 13 and a matching circuit 12, the ions produced in the plasma are accelerated and put incident to the sample 3 so that etching propagates in the vertical direction. An antenna 5 is interposed between the conductors of a sample rest 2 and an oversurface electrode 1, and thereby a plasma small in reflection and high in efficiency is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for treating a surface of a semiconductor element, and more particularly to an apparatus for etching or forming a film on the surface of a semiconductor by using plasma.

[0002]

2. Description of the Related Art An apparatus currently widely used for etching and film forming of semiconductor elements is an apparatus utilizing plasma. One of them is an apparatus called an ECR (Electron Cyclotron Resonance) system. In this method, plasma is generated by microwaves in a vacuum vessel to which a magnetic field is externally applied. Electrons make cyclotron motion due to the magnetic field,
Plasma can be generated efficiently by resonating this frequency with the frequency of the microwave. Further, the diffusion of the plasma to the wall is suppressed by the magnetic field, and high-density plasma can be generated. A high frequency voltage is applied to the sample in order to accelerate the ions incident on the sample. For example, when etching is performed, a halogen gas such as chlorine or fluorine is used as the plasma gas. In addition to etching, this device is also used for film deposition.

Various types of this device have been proposed in the past. For example, Japanese Patent Laid-Open No. 2-16731 discloses a device that generates an ECR discharge at a power supply frequency of 2 GHz or less and 100 MHz or more. In this device, electromagnetic waves are introduced from the upper side of the vacuum container by a waveguide or coaxial cable. An object of the present invention is to improve the uniformity by increasing the electron cyclotron radius as compared with the conventionally known microwave of 2.45 GHz. Further, Japanese Patent Laid-Open No. 3-238800 discloses a device for generating ECR discharge at a power supply frequency of 0.7 to 1.2 GHz. The object of the present invention is also the uniform treatment of a large-area sample as in the previously known example. The microwave introduction method is described as capacitive coupling type (parallel plate) or inductive coupling type (loop type, coil, etc.), but there is no more specific description.

[0004]

As a result of the test, it was found that the method of introducing high frequency described in the known example is not yet sufficient in the efficiency of plasma generation. A first object of the present invention is to provide an efficient power supply method.

Further, it has been found that the in-plane uniformity of the sample such as the etching rate cannot be achieved only by the uniformity of the plasma density as described in the known example. The second object of the present invention is to further improve the uniformity of etching characteristics.

[0006]

In order to increase the efficiency of plasma generation and further improve the uniformity of etching characteristics, an antenna is provided in parallel with the sample, and an antenna through which a high frequency for generating plasma is generated between them. It has a structure to insert.

[0007]

The antenna sandwiched between the two conductors allows high-frequency current to flow without a cutoff frequency, just like a coaxial cable, so that there is little reflection and efficient power supply is possible and plasma is also efficiently generated.

[0008]

【Example】

(Embodiment 1) An embodiment will be described below with reference to FIG. FIG.
FIG. 1 (a) is a top view of the device of the present invention, and FIG. 1 (b) is a sectional view of the device of the present invention seen from the side. The vacuum container is composed of an upper electrode 1 and a sample table 2 whose upper and lower surfaces are arranged in parallel. Top electrode
1 is a metal such as Al or a semiconductor such as C, Si or SiC.
The sample table 2 is insulated from the side wall 4, and the sample 3 to be surface-treated by etching or the like is placed thereon. A vacuum exhaust pipe 10 and a transfer pipe 11 for loading and unloading the sample are connected to the side wall. The sample carrier is omitted. A loop-shaped antenna 5 is installed between the sample table 2 and the top electrode 1. The material of the antenna is metal such as Al or C, Si, Si
It is a semiconductor such as C. Alternatively, these materials are covered with an insulating material such as a quartz tube to prevent the sputtering by ions. The antenna may be a double or more loop. High frequency power is supplied here by the high frequency power supply 8 and the matching circuit 7. A vacuum is maintained at the power line seal section 6. Ring-shaped permanent magnets 9 are arranged above and below the vacuum container. When the vacuum container is filled with a gas having a pressure of 0.1 mTorr to several hundred Torr and high-frequency power is supplied to the antenna 5, plasma is generated.

The advantage of this structure is that the antenna 5 is the top electrode 1
And because it is sandwiched between the two conductors of the sample table 2, electric force lines are generated from the antenna to the upper and lower conductors, just like a coaxial cable. For this reason, the electromagnetic wave can generate plasma at the same time as it propagates in the vacuum container, so that highly efficient plasma generation with less reflection becomes possible.
Moreover, there is no cutoff frequency in the propagating frequency. That is, it can be used over a wide frequency band.

Next, the role of the magnetic field will be described. The electrons and ions in the plasma generated in the vacuum vessel spiral around the lines of magnetic force generated by the magnet 9. Therefore, the diffusion of plasma to the side wall 4 is suppressed, and high-density plasma is generated. Furthermore, the cyclotron motion of electrons (helix motion)
If the frequency of the power source 8 and the frequency of the power source 8 are made to coincide with each other, ECR plasma is generated and the density can be made higher. For example, when the frequency is 2.45 GHz, this condition is satisfied by setting the magnetic field strength to 875 Gauss. When a magnetic field of this strength is generated at the center of the sample, high density plasma can be formed directly above the sample.

Next, an example of actual surface treatment will be described. For example, when etching a silicon oxide film with this equipment, CF
A gas composed of C, H, F such as 4, C4F8, C2F6, C3F8, CHF3, CH2F2 is filled with a pressure of several mTorr to generate plasma. Further, a high frequency voltage is applied to the sample 3 by the bias power source 13 and the matching circuit 12. This frequency is different from that of the power source 8 for plasma generation in order to avoid interference. Then
Ions of F or CFx generated in the plasma are accelerated and are incident on the sample 3, and etching proceeds vertically due to the energy and the directionality thereof. At this time, a high-frequency current from the bias power supply 13 flows in the plasma, but because the upper surface electrode 1 at the ground potential is parallel to the sample, the plasma resistance to the high-frequency current becomes uniform within the sample 3 surface, The current flows almost uniformly, and the etching rate becomes uniform in the plane.

With this configuration, it is possible to use in a wide frequency band as described above. Specifically, the frequency of the power source 8 is 100
MHz to 2.45 GHz are suitable. Transmission line 14 depending on frequency
Is a coaxial line or uses a waveguide. At present, in semiconductor processes, the size of sample 3 is increasing, and the year 2000
It is expected that the sample diameter will be 30 cm or more around this time. This problem can be dealt with by lowering the frequency of the power supply 8. That is, when the frequency is set to 400 to 900 MHz (wavelength in vacuum 75 to 33 cm), the size and wavelength of the vacuum container are almost the same. Then, high-order standing waves do not stand in the container, the plasma density becomes uniform, and the etching rate becomes uniform. Further, the magnetic field strength required for the electrons to resonate with the cyclotron also becomes smaller, so that the magnet 9 becomes smaller and the enlargement of the device can be suppressed.

Further, if the distance between the sample table 2 and the upper electrode 1 is set to be half the high frequency wavelength or less, no standing wave is generated in the height direction of the vacuum container, so that the strength of the electrolytic strength in the height direction of the sample is weakened. The instability caused by is eliminated. Further, since the processing speed becomes non-uniform when the antenna is close to the sample 3, the influence of the antenna is reduced by setting the distance between the antenna and the parallel electrode to be half the distance between the sample stage and the parallel electrode. Is effective. Also. With respect to the high-frequency voltage applied to the sample 3, the shorter the distance between the sample stage 2 and the upper surface electrode 1, the shorter the distance of the current passage and the smaller the effect of the plasma resistance, so that the high-frequency current becomes uniform. From this point of view, it is appropriate that the distance between the sample table 2 and the top electrode 1 be 10 cm or less.
Depending on the application, it should be 3 cm or less.

(Embodiment 2) FIG. 2 is a side view of an apparatus according to another embodiment of the present invention. In this device, a magnetic field is generated by the electromagnet 15. Electric magnets have a problem of power consumption, but they do not deteriorate in magnetic field strength as compared with permanent magnets. The magnets may be located above and below the vacuum container as in FIG. Alternatively, the number of electromagnets may be one.

(Embodiment 3) FIGS. 3 and 4 show another embodiment of the antenna shape. In this device, the plasma density distribution can be controlled by the shape of the antenna. For example, as shown in FIGS.
The shape close to the heavy loop can improve the nonuniformity of the plasma intensity depending on the distance from the antenna.

(Embodiment 4) FIG. 5 shows a structure in which an antenna is provided outside a vacuum container. In this case as well, the antenna 18 is sandwiched between the upper electrode 19 and the sample table 20 to obtain the same effect as that of the previous embodiment. In this structure, the side wall 21 needs to be made of a dielectric material such as quartz, alumina, and silicon nitride. The positional relationship between the antenna 18 and the upper surface electrode 19 is important, and in order to efficiently propagate the electromagnetic wave, the distance L (shown in FIG. 5) from the end of the upper surface electrode 19 to the antenna 18 is applied to the electromagnetic wave of the power source 8 in a vacuum. This structure, which has been experimentally found to be required to be ⅛ or more of the wavelength of 1, is advantageous in that there is no influence of sputtering of the antenna 18.

[0017]

As described above, according to the present invention, it is possible to provide a surface treatment apparatus having a high plasma generation efficiency and capable of uniformly treating a large-diameter sample of 30 cm or more by the present apparatus.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus to which the present invention is applied, in which (a) is a top view and (b) is a side view.

FIG. 2 is a side view of another embodiment.

FIG. 3 is a top view of another embodiment.

FIG. 4 is a top view of another embodiment.

FIG. 5 is a side view of another embodiment.

[Explanation of symbols]

1-upper surface electrode, 2-sample stage, 3-sample, 4-side wall, 5-
Antenna, 6-power line seal part, 7-matching circuit, 8-power source, 9-magnet, 10-vacuum exhaust pipe, 11-sample carrier pipe,
12-matching device, 13-bias power supply, 14-transmission line, 1
5-electromagnet, 16-antenna, 17-antenna, 18-antenna, 19-top electrode, 20-sample stage, 21-side wall.

Claims (7)

[Claims] 1. An apparatus comprising a container whose interior can be evacuated to a vacuum, a sample table in the container, and a magnet for forming a magnetic field in the container, wherein parallel electrodes are arranged facing the sample table, and the sample table and parallel electrodes are arranged. A surface treatment device characterized in that an antenna is provided between the surfaces and a high-frequency current is passed through the antenna to generate plasma in the container. 2. The surface treatment apparatus according to claim 1, wherein the high frequency current has a frequency of 400 MHz to 900 MHz. 3. The surface treatment apparatus according to claim 1, wherein the magnetic field strength matches the cyclotron frequency of electrons in the plasma. 4. The apparatus according to any one of claims 1 to 3, wherein the distance between the sample stage and the parallel electrode is one half of the wavelength in a high frequency vacuum.
The surface treatment apparatus characterized in that the distance between the antenna and the parallel electrode is set to be equal to or less than half the distance between the sample stage and the parallel electrode. 5. A surface treatment apparatus according to claim 1, wherein the distance from the parallel electrode chopstick to the antenna is not less than ⅛ of a wavelength in a high frequency vacuum. 6. The surface treatment apparatus according to claim 1, wherein a high frequency having a frequency different from a high frequency for generating plasma is applied to the sample stage. 7. The surface treatment apparatus according to any one of claims 1 to 6, wherein the distance between the sample stage and the parallel electrode is 10 cm or less.