JPH05121366A - Dry etching method - Google Patents

Abstract

PURPOSE:To obtain a method of etching by the use of a plasma in the process of manufacturing a semiconductor device, by which formation of a polymerization film or a protective film is enhanced and the anisotropy of the film is improved. CONSTITUTION:This is one where an ion or electron beam generation source 18 is provided separately from plasma for etching, and the irradiation with the beam is performed obliquely to a wafer 17. Hereby, even if the energy of ions entering vertically a sample is low, a protective film can be formed on the sidewall of a pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method using plasma used in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art Recently, as semiconductor devices have been highly integrated, their elements have been miniaturized, and high-precision processing techniques have been required. As part of this, dry etching using plasma is widely used at present in the etching process, which is one of the manufacturing processes of semiconductor devices.

In this method, as is well known, a high frequency is generated by using a magnetron or the like, and the accelerated ions are generally applied to a sample (semiconductor substrate or wafer) by excitation by accelerated electrons and ionization (plasma formation), that is, discharge. Etching is performed by vertically colliding.

In such an etching method, as a method of obtaining an anisotropic shape, a deposition gas is added to an etching gas to form a polymer film on a side wall portion of a pattern on a sample (semiconductor substrate or wafer), etc. Protecting electrically neutral radical species, which is an anisotropic etching species (as is well known, gas molecules dissociate into electrons, ions, and radical species when energized by accelerated electrons), can be protected by polysilicon. It is used in (Poly-Si) etching and the like.

[0005]

In the side wall protection method using the polymer film described above, the thickness of the polymer film formed on the pattern side wall becomes thicker as the incident ion energy is higher. Further, in order to form a polymer film necessary to maintain an anisotropic shape (a shape that is etched perpendicular to the mask), the incident ion energy must be high to some extent, but if it is higher than necessary, it is preferable. No polymerized film is possible.

That is, in order to form the above-mentioned polymer film, it is usually 20 eV.
It is believed that some low energy ions can be involved. In other words, it is considered that the formation of the polymerized film on the side wall portion is because the ions, which have become low energy due to scattering on the surface of the sample, fly to the side wall and accelerate the polymerization reaction. The higher the RF (high frequency) power, the greater the amount of these low-energy ions that fly, the thicker the polymer film is, and the stronger the anisotropic shape.

When the RF power is high as described above, the polymerized film is formed thick, the dimensional conversion difference (difference between mask size and etching size) is small (ideally, 0 is good), and a good anisotropic shape is obtained. However, the selection ratio with respect to the resist used as a mask and the underlying oxide film (see FIG. 1) is lowered, which causes a problem that unnecessary portions are etched (cut).

In order to prevent the above-mentioned decrease in the selection ratio, the present invention provides an ion source or an electron beam source for forming a polymerized film in addition to the plasma source for etching, so that the selection ratio is improved. An object of the present invention is to provide an etching method capable of obtaining a high and favorable anisotropic shape.

[0009]

To achieve the above object, the present invention provides a dry etching method using plasma, in which an ion source or electron beam source for forming a polymer film is provided separately from a plasma source for etching. Then, the low energy ion or electron beam generated thereby is obliquely irradiated to the sample to form the side wall protective film.

[0010]

As described above, according to the present invention, the ions of low energy (20 eV or less) are obliquely irradiated to the sample during the plasma etching, so that the ion energy incident vertically on the sample is low. However, a sufficient protective film can be formed on the side wall, and a high selection ratio can be obtained while maintaining a good anisotropic shape.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a block diagram of a plasma etching apparatus used in an embodiment of the present invention. The plasma source for etching is 2.45 GH oscillated by the magnetron 11.
EC due to the interaction between the microwave of z and the magnetic field formed by the electromagnetic coil 13 installed around the discharge chamber 12.
R (Electron Cyclotron Reso
(NCR) phenomenon is used to generate plasma
A plasma source was used. The etching gas SF ₆ and the deposition gas C ₂ Cl ₂ F ₄ are respectively supplied from the gas introduction pipe 14 for 7 s.
ccm, 63sccm flow, etching pressure 10mTo
Plasma is generated under the conditions of rr and microwave power of 400 w. The plasma generated in the discharge chamber 12 is irradiated toward the sample (wafer) 17 placed on the sample stage (wafer susceptor) 16 from the opening 15 of the discharge chamber according to the divergent magnetic field, and is a film to be etched. Po on wafer 17
The ly-Si is etched using the resist as a mask (see FIG. 1).

In this embodiment, in addition to the plasma source, an ion source or electron beam source 18 is provided obliquely above the sample (wafer) 17 in the plasma etching apparatus as shown in FIG. Ion or electron beams from 18 are obliquely applied to the wafer 17. It goes without saying that the ion source or electron beam source 18 is a known ion beam generator or electron beam generator.

In this embodiment, in addition to the above-mentioned etching plasma, this embodiment uses the ion source or the electron beam source 18 during the etching, and when the ion source is used as shown in FIG. When an electron beam source is used, the wafer 17 is obliquely irradiated with ions having an energy of 20 eV or less. By the irradiation, as shown in FIG. 1, a polymerized film is formed on the side wall of the pattern on the wafer 17 to prevent etching by radical species as in the conventional case.

As described above, according to the present embodiment, the ions scattered by the etching plasma do not form the polymerized film, that is, the protective film on the side wall of the pattern, but the polymerized by the irradiation from the ion or electron beam source 18 provided separately. Since the film is formed, the polymer film can be controlled regardless of the energy of the etching plasma.

[0015]

As described above, according to the method of the present invention, the sample (wafer) is obliquely irradiated with the ion or electron beam separately from the plasma during plasma etching. Even if the energy of ions incident perpendicularly to the wafer is low, that is, regardless of the ion energy for etching, a protective film can be formed on the side wall of the pattern, and a good anisotropic shape can be maintained. At the same time, a high selection ratio in etching can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 17 Wafer 18 Ion source or electron beam source

Claims (2)

[Claims] 1. A dry etching method using plasma, which is used in a manufacturing process of a semiconductor device, wherein an etching gas and a deposition gas for forming a polymer film are introduced as gas species, and an etching plasma source is used. The method of dry etching, wherein the ions accelerated by the plasma are vertically incident on the sample, and the sample is etched while being obliquely irradiated with ions from an ion source provided separately from the plasma source. 2. A dry etching method using plasma, which is used in a semiconductor device manufacturing process, wherein an etching gas and a deposition gas for forming a polymer film are introduced as gas species, and the etching plasma source is used. Dry etching method characterized in that the ions accelerated by the plasma are vertically incident on the sample, and the sample is etched while being obliquely irradiated with an electron beam from an electron beam source provided separately from the plasma source. .