JPH06140374A - Fine processing method for semiconductor - Google Patents

Abstract

PURPOSE:To improve resistance against chlorine in the fine processing of semiconductors by locating a needle-shaped electrode having a potential different from that of a semiconductor substrate closely to the surface of a semiconductor substrate, by applying a current between the semiconductor substrate and the needle-shaped electrode and by contacting a second gas-like substance capable of thermally etching the semiconductor substrate to the surface of the semiconductor substrate. CONSTITUTION:Potential of a needle 15 is set to -2V, and a tunnel current 16 of 20 nA is applied between the needle 15 and the sample surface. Then, a desired pattern is drawn by scanning a tunnel current 16 in-plane direction of sample. In the region 17 irradiated with an electron beam, an oxide film (oxide film of aluminum) is desorbed to vacuum by electron excitation and desorption. Next, voltage application is stopped, and the needle 15 is moved away from the surface of sample. Then, the sample is carried to an etching chamber. A gas introducing apparatus is provided in the etching chamber, chlorine gas 18 is introduced to the etching chamber by said gas introducing apparatus and this gas is contacted to the surface of sample.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a semiconductor, and more particularly to a method for finely processing a semiconductor using an STM structure using an aluminum oxide film formed on the surface of a semiconductor substrate as a resist mask.

[0002]

2. Description of the Related Art A technique for forming a fine pattern on the surface of a semiconductor is an indispensable technique for producing various semiconductor elements. In recent years, with high integration and high functionality of elements, fine processing technology from submicron to nanometer order has been required.

In particular, a vacuum integrated process is required to manufacture a highly functional device such as an optoelectronic integrated circuit, and an organic resist is not used as a pattern forming method suitable for this,
A method for directly forming a pattern on a semiconductor by using an ion beam, a laser beam, or the like capable of focusing on an extremely small diameter is being actively studied.

The method using the above ion beam has a problem that a large number of crystal defects are induced in the processed semiconductor crystal. Further, when a laser beam is used, the focused beam diameter depends on the wavelength and its limit is said to be about 100 nm, and further fine processing is difficult.

Therefore, the method using an electron beam has been attracting attention because it has low damage and is compatible with fine processing. As a conventional method of forming a fine pattern using an electron beam, electron beam excited gas etching (Journal of Applied Physics vol. 67, N.
o. 9, P. 4297) will be described below.

First, GaAs was formed on the surface of a (001) GaAs substrate by the molecular beam epitaxial growth method (MBE method).
Form the layers. The surface of the formed GaAs layer is photooxidized. As a result, an extremely thin oxide film is formed on the surface.

Thereafter, the surface of the oxide film is irradiated with an electron beam by using an electron beam gun while heating the substrate in a chlorine gas atmosphere. As a result, only the oxide film in the area irradiated with the electron beam is removed, and GaAs in the area where the oxide film is removed is removed.
The layer is etched with chlorine gas. In the region not irradiated with the electron beam, the oxide film acts as an etching mask, so that etching does not occur. The pattern thus drawn by the electron beam is transferred to the GaAs layer.

FIG. 3 shows an electron beam gun used for forming a conventional fine pattern. This electron beam gun includes an emitter 301, an electron extraction electrode 302, an electron acceleration electrode 303, an electrostatic condenser lens 304, an alignment electrode 305, a blanking electrode 306, a movable control diaphragm 307, a beam scanning electrode 308, and astigmatism correction. The electrode 309 and the objective lens 310 are provided.

The electron beam from this electron beam gun is
The sample 320 is focused and scanned just below the electron beam gun. This type of electron beam gun is widely used in an analyzer that uses a general electron beam, and has a beam diameter of 5 nm, which enables fine processing.

[0010]

However, the electron beam gun has a problem that its structure is very complicated and adjustment is difficult. Further, the electron beam has a long path and is easily influenced by an external magnetic field or an external electric field, and the beam diameter and the irradiation position are changed even by a slight fluctuation, resulting in lack of long-term stability.

Therefore, it is very difficult to form a desired pattern on the order of nanometers by the conventional fine processing method using an electron beam gun.

Although a GaAs photo-oxidation film is used in the conventional example, this film is not sufficient in chlorine resistance for a long time or at high temperature.

An object of the present invention is to provide a semiconductor microfabrication method which has a simple structure and uses a device capable of obtaining a stable electron beam and which is excellent in chlorine resistance.

[0014]

In order to achieve the above object, in the method for finely processing a semiconductor according to the present invention, an extremely thin layer containing at least one of aluminum and an aluminum compound is formed on the surface of a semiconductor substrate. A step of contacting a surface of the semiconductor substrate with a first gaseous substance containing at least one of oxygen and an oxygen compound to form an oxide film on the surface of the semiconductor substrate; A step of bringing a needle-shaped electrode having a potential different from the potential of the semiconductor substrate close to each other, and causing a current to flow between the semiconductor substrate and the needle-shaped electrode; Contacting a second gaseous substance that can be etched.

[0015]

When the semiconductor surface is irradiated with the etching gas, the etching progresses only in the portion of the oxide film where electron excitation and desorption are performed, and in the region where the tunnel current is not irradiated, the oxide film acts as a resist mask for chlorine gas etching, and the etching is not performed. Does not progress.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a vacuum integrated process device used in the semiconductor fine processing method of the present invention. 2, the load lock chamber 21, the MBE chamber 22, the pattern drawing chamber 23, and the etching chamber 24 are connected to the sample transfer chamber 25 via passages each having a gate valve.

A vacuum pump (not shown) is provided in each room so that the room can be evacuated independently. The MBE chamber 22, the pattern drawing chamber 23, and the etching chamber 24 have magnet feedthroughs 26a,
26b and 26c are provided, and these can be used to transport the sample to each chamber.

An embodiment of semiconductor microfabrication using this ultrahigh vacuum apparatus will be described below with reference to FIGS. 1 and 2.

In the figure, first, a (001) GaAs substrate 11 is introduced into a load lock chamber 21. Next, the load lock chamber 21 is evacuated to about 1 × 10 ⁻⁷ Torr by using a turbo molecular pump (not shown) and an ion pump (not shown). At this time, the back pressure of other rooms is 1 × 10 in advance.
^-9 Torr.

Next, the GaAs substrate 11 is placed in the sample transfer chamber 25.
Through the MBE chamber 22. In the MBE chamber 22, as shown in FIG. 1A, the GaAs layer 12 having a thickness of 0.5 μm and the AlG having a thickness of 1 nm are transferred onto the GaAs substrate 11.
The aAs layer 13 is continuously grown.

After the growth, the GaAs substrate 11 is transported to the pattern drawing chamber 23, oxygen gas is introduced from the oxygen gas introduction device 231, and the surface of the AlGaAs layer 13 is exposed to high-purity oxygen. As a result, a very thin and strong oxide film 14 is formed on the surface of the AlGaAs layer 13.

The MBE chamber 22 and the pattern drawing chamber 23 are
Since the inside is kept in ultrahigh vacuum in advance, AlGaAs
The surface of the layer 13 is kept clean, and almost no impurities are found in the formed oxide film 14.

After forming the oxide film, the introduced oxygen is evacuated. The pattern drawing chamber 23 is equipped with an electron beam generator 232. The electron beam generator 232 has the same configuration as a scanning tunneling microscope (STM), that is, as shown in FIG.
A proximity mechanism (not shown) for bringing 5 into proximity with the sample;
It has a voltage supply unit (not shown) for applying a voltage to the needle 15. The transported sample is held by the sample holder. As shown in FIG. 1B, the needle 15 is brought close to this sample by a proximity mechanism to a distance where the tunnel current 16 flows.

For example, the potential of the needle 15 is set to -2 V and the needle 1
A tunnel current 16 of 20 nA is passed between 5 and the sample surface. Then, a desired pattern is drawn by scanning the tunnel current 16 in the in-plane direction of the sample.

In the region 17 irradiated with the electron beam, the oxide film (aluminum oxide film) is desorbed in vacuum by electron-excited desorption.

Next, the voltage application is stopped and the needle 15 is moved away from the sample surface. Then, the sample is transported to the etching chamber 24.

In the etching chamber 24, a gas introduction device 24
1, the chlorine gas 18 is introduced into the etching chamber 24 by this gas introduction device 241, and this gas is brought into contact with the sample surface.

In the desorbed region (tunnel current irradiation region) of the aluminum oxide film, a chemical reaction between the chlorine gas 18 and the GaAs layer occurs, and etching proceeds as shown in FIG. 1 (c). In the region where the tunnel current is not irradiated, the oxide film 14 functions as a resist mask for chlorine gas etching, and etching does not proceed.

In this embodiment, a region for irradiating a tunnel current has a linear pattern with a width of 10 nm, and the substrate temperature is 70 ° C.
When chlorine gas etching is performed for 2 minutes, etching with a width of 10 nm and a depth of 25 nm can be performed.

According to the method of the present invention, the distance between the needle 15 and the sample surface can be made extremely short, so that the instability of the electron beam due to an external electric field or the like is hardly recognized. Further, since the alignment of the electron beam is uniquely determined by the position of the needle, an electrostatic lens or the like is not required, and the electron beam generator 23
2 is very small. Further, it is expected that the present study of the surface observation technique by STM can realize the formation of a fine pattern of about 1 nm by further reducing the distance between the needle 15 and the sample and further reducing the tunnel current value.

The present invention can also be applied to the following cases. (1) When the semiconductor material is other than GaAs (InGaA
s, InGaAsP, Si, Ge, etc.). (2) When the gas used for oxide film formation is other than pure oxygen (H ₂ O, CO ₂ , NO _2, etc.). (3) When the etching gas is other than chlorine gas (F ₂ , I
₂ , HF, NF ₃ , CH ₄ , C ₂ H ₆ etc.). (4) When a material other than tungsten is used as the material of the needle (platinum, carbon, etc.).

[0033]

According to the present invention, a fine pattern on the order of nanometers can be formed. In particular, by using the needle-shaped electrode used in STM for electron beam irradiation, the diameter and position of the electron beam can be accurately controlled, and the pattern formation can be made uniform and reproducible, and highly functional and highly integrated semiconductor devices can be created. Available for

[Brief description of drawings]

FIG. 1A to FIG. 1C are diagrams of a microfabrication process according to an embodiment of the present invention.

FIG. 2 is a schematic view of an ultra-high vacuum device used in the present invention.

FIG. 3 is a configuration diagram of a conventional electron beam gun.

[Explanation of symbols]

 11 GaAs substrate 12 GaAs layer 13 AlGaAs layer 14 Oxide film 15 Needle 16 Tunnel current 17 Irradiation region 18 Chlorine gas 21 Load lock chamber 22 MBE chamber 23 Pattern drawing chamber 24 Etching chamber 25 Sample transfer chamber 26 Magnet feed through 231 Oxygen gas introduction device 232 Electron beam generator 241 Gas introduction device

Claims (1)

[Claims] 1. A step of forming an extremely thin layer containing at least one of aluminum and an aluminum compound on the surface of a semiconductor substrate; and a step of containing at least one of oxygen and an oxygen compound on the surface of the semiconductor substrate. Contacting the gaseous substance of No. 1 to form an oxide film on the surface of the semiconductor substrate; and bringing the needle electrode of a potential different from the potential of the semiconductor substrate close to the surface of the semiconductor substrate, And a step of passing an electric current between the needle-shaped electrode and a step of bringing a surface of the semiconductor substrate into contact with a second gaseous substance capable of thermally etching the semiconductor substrate. Fine processing method.