JPH09330915A - Surface treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the uniformity of surface treating characteristic in the surface of a sample by respectively applying high-frequency voltages having different frequencies across a sample stage and electrodes and, at the same time, a pulsative high-frequency voltage across the sample stage. SOLUTION: An electrode 2 and a circular sample stage 6 are respectively arranged in parallel with each other on the upper and lower surfaces of a vacuum vessel 1. The electrode 2 on the upper surface is made of a metal or semiconductor and connected to a high-frequency power source 4 through a matching circuit 3 and further connected to the ground through a high-pass filter 5. The stage 6 is insulated from the vessel 1 and a sample 7 which is subjected to surface treatment, such as etching, etc., is placed on the stage 6. A pulsative power source 9 is connected to the stage 6 through a capacitor 8. The cycle frequency of the power source 9 and the frequency of the filter 5 are respectively set at 200kHz and 13.56MHz. In addition, the cut-off frequency of the filter 5 is set at 30MHz and chlorine is made to flow to the vessel 1 so as to generate plasma.

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 device, and more particularly to an apparatus for etching or forming a film on a semiconductor surface 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. There is an apparatus in which two or more power supplies are provided in one of the apparatuses, one is used for plasma generation, and one is used for drawing charged particles such as ions generated in plasma to the surface of a sample to be treated. In this type of equipment, Proceeding of Sy
mposium on Dry Process In 1995, page 39, a device for applying a pulse voltage to a sample to attract charged particles to the sample is known. In this device, a fast rising pulse (eg, 1 v / ns) is applied to the sample to draw electrons into the sample at a high acceleration voltage, prevent local electrification in a fine shape on the semiconductor wafer, and etch the sample. To improve. A microwave of 2.45 GHz is used to generate plasma, and electron cyclotron resonance is caused by a magnetic field to generate high-density plasma.

Further, as a technique related to the present invention, Jouna
l of Vacuum Science and Technology A Volume 10 No.5 1
There is a device described on page 3048 in 992. In this device, different frequencies are applied to the sample table and the electrodes arranged in parallel with the sample table. The high frequency applied to the electrode is intended to generate plasma in the vacuum container, and the high frequency applied to the sample stage is intended to draw ions generated in the plasma into the sample. By this method, the energy of the ions incident on the sample and the density of the plasma can be controlled independently. In this publicly known example, there is no description of a method for preventing abnormal shape of the sample, and no method for applying a pulse to the sample without any inconvenience.

When etching a semiconductor sample, for example, with these apparatuses, a halogen gas such as chlorine or fluorine is used as a gas that becomes plasma. In addition to etching, these devices are also used for film deposition.

[0005]

Semiconductor wafers are currently 8 inches and are on the rise. Then, the uniformity of surface treatment characteristics such as the etching rate and the etching shape within the wafer surface becomes an important issue. There is no specific description for solving this point in the known example.

It is an object of the present invention to provide a surface treatment apparatus with improved uniformity of surface treatment characteristics in a sample plane.

[0007]

A pulse voltage is applied to a sample and an electrode surface is provided in parallel with the sample in order to improve the uniformity of the etching rate and the etching shape in the wafer surface. A high frequency for generating plasma was applied to the electrodes.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

[0009]

First Embodiment An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of the present invention as viewed from the side. In FIG. 1, an electrode 2 is provided on each of the upper surface and the lower surface of the vacuum container 1.
And a circular sample table 6 arranged in parallel therewith. The electrode 2 on the upper surface is a metal such as Al or a semiconductor such as C, Si, or SiC, and a high frequency power source 4 is connected via a matching circuit 3.

Further, the electrode 2 is connected to the ground via a high pass filter 5. The sample table 6 is insulated from the vacuum container 1, and a sample 7 to be surface-treated by etching or the like is placed on the sample table 6. A pulse power supply 9 is connected to the sample table 6 via a capacitor 8. In the vacuum container 1,
The vacuum exhaust pipe 10 and the gas introduction pipe 11 are connected. The introduced gas is ejected into the container through the fine holes provided in the electrode 2. The gas introduction method is not limited to this method.
The vacuum container 1 is at ground potential. 2 and 3 are cross-sectional views of the fine pattern on the sample 7.

Next, the result of etching polysilicon with this apparatus will be described. The voltage of pulse power supply 9 is pulse height 100
At V, the rising speed was 1 V / ns, the repetition frequency was 200 KHz, and the pulse duty ratio was 5%. The power of the high frequency power source 4 is 800
W and frequency was 13.56MHz.

The cutoff frequency of the high-pass filter 5 is 30M.
It was set to Hz. Chlorine 10 mTorr was flown into the vacuum container 1 to generate plasma. As a result of etching the 8-inch wafer in this state, as shown in FIG. 2, the silicon 16 and the polysilicon 13 on the oxide film 15 could be etched without a shape abnormality as the pattern (0.35 μm) of the resist 14. Also, good uniformity was obtained within ± 3% of the etching rate uniformity.

The reason why this method does not cause a shape abnormality such as the notch 17 in a thin pattern as shown in FIG.
As described in eeding of Symposium on Dry Process 1995 page 39), electrons are accelerated by a positive voltage pulse with a fast rising edge and vertically enter the sample 7. This is because they can be softened and the electric field does not bend in the groove.

The reason why the in-plane uniformity is further improved by the present invention is as follows. The current of the pulse power supply 9 applied to the sample 7 passes through the plasma 12 and flows to the ground.
Since plasma has impedance, if the impedance between each point on the surface of the sample 7 and the ground is different, the magnitude and phase of the current flowing in the sample surface will be different. Then, the etching rate and shape are different in the sample plane. If a flat plate-shaped electrode 2 is provided in parallel with the sample 7 and is connected to the ground plane via a high-pass filter 5 through which a fast rising component of the pulse flows, the distance between the surface of the sample 7 and the ground becomes uniform in the plane. .

Further, when a high frequency for plasma generation is applied to the electrode 2 to generate plasma, the uniformity of the plasma density is also improved, so that a pulse current flows uniformly in the surface of the sample 7 and the in-plane uniformity of etching is improved. At this time, the cutoff frequency of the high-pass filter must not pass the frequency of the high frequency power supply 4 and must sufficiently pass the high frequency component of the pulse. The higher the frequency of the high frequency that generates the plasma, the higher the density of the plasma.

As a result of the experiment, the frequency of the high frequency power source 4 is 100M.
When the cutoff frequency of the high-pass filter 5 was set to be higher than the frequency of the high-frequency power source 4 below Hz, stable discharge and pulse effects were obtained.

[0017]

Second Embodiment FIG. 4 shows another embodiment in which a cylindrical ground electrode 17 is provided around the sample table 7. In the embodiment of FIG. 1, the current of the high frequency power source 4 flows between the electrode 2 on the upper surface and the vacuum container 1 which is at the ground potential. Then vacuum container 1
If the shape of is not axisymmetric, a problem such as bias of plasma density will occur and the degree of freedom in the shape of the vacuum container will be lost.

In this embodiment, a ground electrode 17 is provided to improve this point. As a result, uniform plasma can be generated regardless of the shape and potential of the vacuum container.

[0019]

Third Embodiment FIG. 5 shows still another embodiment. Here, a bandpass filter 18 that passes only the frequency of the high frequency power source 4 is connected to the sample table 6. Then, a current for generating plasma flows through the sample table 6. With this configuration, it is not necessary to take another ground as in the previous embodiment.

With this configuration, the pulse repetition frequency of the pulse power source 9 is set higher than the frequency of the high frequency power source 4, and the high pass filter 5 that passes the pulse repetition frequency or more on the electrode 2 side and the high frequency power source on the sample stage 6 side. A bandpass filter 18 that passes the four frequencies may be provided.

[0021]

Fourth Embodiment Next, a method of etching a silicon oxide film with the above apparatus will be described. In this case, a gas containing at least C and F such as CF4, C4F8, C2F6, C3F8, CHF3, CH2F2 is used as the etching gas. A rare gas such as argon is mixed with these, and the pressure in the vacuum container 1 is adjusted to several hundred m.
Torr and generate plasma. With this method, fine oxide film holes of submicron or less can be etched. Since the oxide film is an insulator, local charging is likely to occur, and the effects of the present invention are particularly likely to be exhibited.

[0022]

As described above, according to the present invention, a fine pattern on a semiconductor sample can be etched without abnormal shape and with good uniformity within the sample surface.

[Brief description of drawings]

FIG. 1 is a cross-sectional view as seen from the side in a configuration diagram of an embodiment to which the present invention is applied.

FIG. 2 is a sectional view of a fine pattern on a semiconductor sample.

FIG. 3 is a sectional view of a fine pattern on a semiconductor sample.

FIG. 4 is a cross-sectional view as seen from the side in a configuration diagram of another embodiment to which the present invention is applied.

FIG. 5 is a cross-sectional view as seen from the side in a configuration diagram of another embodiment to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Electrode, 3 ... Matching circuit, 4 ... High frequency power supply, 5 ... High pass filter, 6 ... Sample stand, 7 ... Sample, 8
… Capacitor, 9… Pulse power supply, 10… Exhaust pipe, 11…
Gas inlet pipe, 12 ... Plasma, 13 ... Polysilicon, 1
4 ... Resist, 15 ... Oxide film, 16 ... Silicon, 17 ...
Ground, 18 ... bandpass filter.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H05H 1/46 H05H 1/46 R

Claims (6)

[Claims] 1. A surface treatment apparatus comprising a container whose interior can be evacuated to a vacuum, a sample stage in the chamber, and electrodes arranged in parallel with the sample stage, wherein high frequencies of different frequencies are applied to the sample stage and the electrodes. A surface treatment device characterized in that the high frequency applied to the sample stage is pulsed. 2. The surface treatment apparatus according to claim 1, wherein the electrode is connected to ground through a high-pass filter that passes a frequency component higher than a high frequency frequency applied to the electrode. 3. A surface treatment apparatus, wherein the rising speed of the pulse voltage applied to the sample stage according to claim 1 or 2 is 1 V / ns or more. 4. The surface treatment apparatus according to claim 1, wherein
A surface treatment apparatus, characterized in that a high-frequency frequency applied to the electrode is 100 MHz or less, and a high-pass filter for flowing a frequency component above the frequency to the ground is provided on the electrode side. 5. The surface treatment apparatus according to claim 1, wherein
A surface treatment apparatus characterized in that the sample stage is connected to the ground through a bandpass filter that passes only the high frequency applied to the electrode. 6. The surface treatment apparatus according to claim 1, wherein
A surface treatment apparatus, wherein a gas containing at least C and F is caused to flow in the vacuum container.