JPH08222545A - Surface treating apparatus - Google Patents

Abstract

PURPOSE: To miniaturize the apparatus and to make the surface treating speed uniform by forming the surface, parallel to and facing to the sample, from a conductor to make the distance between an arbitrary point in the surface of the sample and the conductor constant for forming the paths of an RF current, flowing through the plasma, uniformly on the sample surface when an RF voltage is applied to the sample. CONSTITUTION: A sample 10 is mounted on a sample base 9. An RF power supply 11 with an oscillating frequency of several hundreds to several MHz is connected to the sample base 9. When the RF voltage is applied to the sample, ions in plasma 8 are accelerated to be incident on the sample 10 and etching proceeds by the energy thereof. At that time, an RF current flows through the plasma, and the current is nearly uniform in the sample surface 10 because the upper wall of a conductor 2 is parallel to the sample, so that the etching speed is also made uniform in the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment apparatus for semiconductor elements.

[0002]

2. Description of the Related Art A plasma-based apparatus is widely used at present for etching semiconductor elements.
Among these devices, there is a device called ECR (electron cyclotron resonance) system. In this device, plasma is generated by microwaves in a vacuum container to which a magnetic field is applied from the outside. Electrons carry out cyclotron motion due to the magnetic field, and by resonating this frequency with the frequency of the microwave, plasma can be efficiently generated. Further, the magnetic field suppresses the diffusion of plasma to the wall, and high density plasma can be generated. An RF (radio frequency) voltage is applied to the sample in order to accelerate the ions incident on the sample. For example, a halogen gas such as chlorine or fluorine is used as the plasma gas when etching is performed. In addition to etching, this device is also used for film deposition.

Various types of this device have been proposed in the past, and the structure thereof is described in, for example, Nikkei Microdevice October 1991 issue. For example, in the apparatus shown in FIG. 2, the vacuum container is formed by the side wall 16 and the upper wall 15, and the electromagnet 3 is placed outside the side wall 16. The upper wall 15 is made of a microwave transmitting material such as quartz, from which microwaves are introduced by the microwave power source 13 and the waveguide 14. Further, in the apparatus shown in FIG. 3, the magnet 17 is placed above and below the vacuum container, and microwaves are introduced from the upper wall 15.

[0004]

In recent years, the diameter of silicon wafers to be processed has been increasing. Currently, the diameters of 150 mm to 200 mm are mainly used, but in a few years, the diameter of 400 mm will appear. Is expected. Along with this, an increase in the size of the device has become a problem.
For example, as shown in FIG. 2, in the case where the electromagnet is arranged on the outer side wall of the vacuum container, the outer diameter of the electromagnet is 8 mm when the sample diameter becomes 400 mm.
It will be huge, over 100 mm. In order to solve this, a mold in which magnets are arranged above and below the vacuum container as shown in FIG. 3 has also been proposed. However, it has been found that in this type, the surface treatment speed such as the etching speed becomes non-uniform within the wafer surface.

An object of the present invention is to provide a device which is small and has a uniform surface treatment speed.

[0006]

In order to downsize the apparatus, electromagnets are arranged above and below the vacuum container. In addition, the container surface facing the sample stage was made of a conductor in order to make it uniform.
Along with this, microwaves were introduced from the side wall of the container.

[0007]

When the electromagnets are arranged above and below the vacuum container and the outer diameter thereof is substantially the same as the outer diameter of the vacuum container, the height is increased but the floor area is reduced and the size is reduced. By forming the surface facing the sample in parallel with the conductor, the distance between any point on the sample surface and the conductor becomes constant, so the path of the RF current flowing in the plasma when the RF voltage is applied to the sample is the path of the sample. Formed almost uniformly on the surface. As a result, the energy of the ions incident on the sample becomes almost constant, and the in-plane uniformity of the etching rate improves.

[0008]

EXAMPLE An example will be described below with reference to FIG. FIG.
1A is an explanatory view of the present invention seen from the side, and FIG. 1B is a sectional view taken along a dotted line A in FIG. 1A. The vacuum container is made of a material such as quartz or ceramics which transmits microwaves and a side wall 1 and a metal such as aluminum or Si, S.
It is formed of an upper wall 2 made of a semiconductor such as iC. The upper wall 2 is at earth potential. Gas is supplied into the vacuum container from a plurality of gas supply pipes 7 provided on the upper wall. For example, when etching a silicon oxide film with this apparatus, CF ₄ , C ₄ F ₈ , C ₂ F ₆ , C ₃ F ₈ , CH
A gas composed of C, H, and F such as F ₃ and CH ₂ F ₂ is supplied.

An annular waveguide 4 is arranged around the side wall 1, and microwaves are supplied to it by a microwave power source 13 and a waveguide 12. A slot 5 is cut in the annular waveguide 4, from which microwaves are radiated into the vacuum container, and plasma 8 is generated. A metal guard 6 is attached to the waveguide 4 and covers the side wall 1 so that the microwaves from the slot 5 do not leak to the outside. By generating a magnetic field with the coil-shaped electromagnet 3, high-density plasma is generated.

The sample 10 is set on the sample table 9. The sample table 9 has an RF power source 1 with an oscillation frequency of several hundreds to several MHz.
1 is connected. By applying an RF voltage to the sample, the ions in the plasma 8 are accelerated and are incident on the sample 10, and the energy advances the etching. At this time, an RF current flows in the plasma 8. However, since the upper wall 2 of the conductor is parallel to the sample, the current flows almost uniformly in the surface of the sample 10 and the etching rate becomes uniform in the surface.

Using C ₄ F ₈ as an etching gas, the pressure in the vacuum chamber is 5 mTorr, and the microwave power is 800.
When the silicon oxide film is etched with the power of W and RF power supply 13 set to 300 W, the etching rate is 600 nm / mi.
A uniformity of plus or minus 3% was obtained for n. Under the same conditions, when the conventional apparatus shown in FIG. 2 having a structure in which the upper wall is not a conductor was used for etching, the uniformity was significantly degraded to plus or minus 20%.

The thickness of the waveguide 4 is about 30 if a thin one is used when the microwave frequency is 2.45 GHz.
mm. On the other hand, since the thickness of the electromagnet 3 including the magnetic shield material is 100 mm or more, the diameter of the electromagnet 3 can be reduced by about 150 mm as compared with the conventional type in which the magnet is provided on the side wall.

In the case of etching, reactive radicals such as fluorine are generated in the plasma in addition to the ions, and become an etchant together with the ions. Radicals are adsorbed or chemically reacted on the wall of the vacuum container, so that temperature control of the wall is important. Therefore, if a heater and a cooling pipe (not shown) are attached to the upper wall 2 and the side wall 1 so that the temperature can be controlled, the performance is further improved. For example, when a deposition gas such as C ₄ F ₈ is used as the etching gas, the amount of radicals adsorbed on the wall is reduced by setting the wall temperature to about 200 ° C., and the cleaning time after etching is shortened. There are advantages such as

In order to reduce the influence of the wall, the area of the wall should be made as small as possible. Therefore, it is desirable that the distance between the sample table 9 and the upper wall 2 is 100 mm or less. The distance between the side wall 1 and the sample table 9 is preferably 50 mm or more.

[0015]

According to the present invention, the apparatus can be downsized and the in-plane uniformity of the processing speed can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a conventional device.

FIG. 3 is an explanatory diagram of a conventional device.

[Explanation of symbols]

1 ... Side wall, 2 ... Upper wall, 3 ... Electromagnet, 4 ... Annular waveguide,
5 ... Slot, 6 ... Guard, 7 ... Gas supply pipe, 8 ... Plasma, 9 ... Sample stage, 10 ... Sample, 11 ... RF power supply, 12
… Waveguide, 13… Microwave power supply, 14… Waveguide, 15
... Introduction window, 16 ... Side wall, 17 ... Magnet.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H05H 1/46 9216-2G H05H 1/46 B H01L 21/302 F (72) Inventor Koichi Okamura Shimomatsu, Yamaguchi Prefecture Large-scale Higashi-Toyoi 794 Hitachi Ltd. Kasado Plant (72) Inventor Satoshi Ito Shimomatsu, Yamaguchi Prefecture Large-scale Higashi-Toyoi 794 Hitachi Ltd. Kasado Plant (72) Inventor Saburo Kanai Shimomatsu, Yamaguchi Prefecture Large-scale Higashi-Toyoi 794 Hitachi Ltd. Kasado Plant (72) Inventor Tetsunori Kaji Large-scale Higashi-Toyoi 794 Address Hitachi-Kasado Plant

Claims (1)

[Claims] 1. A side surface of a container in a container equipped with a device for evacuating the interior, a sample stage for installing a sample in the container, a microwave source for generating plasma in the container, and an electromagnet. Is a member that transmits microwaves, the upper surface of the vacuum container facing the sample table is a conductor, and electromagnets are arranged above and below the sample table surface and the conductor member surface, respectively.