JPH06104218A - Dry etching method - Google Patents

Abstract

PURPOSE:To etch only an electron-beam irradiating section without side etching by adding an oxygen gas or oxygen radicals to a reactive gas or a radical atmosphere. CONSTITUTION:A GaAs substrate 107 is placed onto a sample base in a sample chamber 108, the GaAs substrate 107 is heated at 60 deg.C, a reactive gas 105, in which a chlorine gas and an oxygen gas are mixed, is introduced onto the surface of the GaAs substrate 107 from a fine nozzle 106, and a fine line region in 0.1mum width and 100mum length is irradiated with electron beams 103 focussed from an electron-beam irradiation system for five min and etched. Accordingly, an etching sidewall is not side-etched, and an etching groove in 0.1mum width can be formed extending over 100mum length in 50nm depth in the same warmer as an electron-beam irradiation region.

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 for a compound semiconductor substrate using an electron beam, and more particularly to a precision dry etching method at the nanometer level.

[0002]

2. Description of the Related Art A dry etching technique for a 3-5 compound semiconductor substrate is important in the semiconductor process. Particularly in recent years, attention has been paid to a nanometer level dry etching technique in which a quantum effect appears. For such nanometer level dry etching, chlorine gas assisted etching using a focused electron beam is used.
No. 85 is proposed. FIG. 3 is a configuration diagram of an electron beam assisted etching apparatus used in this conventional example.

This electron beam assisted etching apparatus includes a focusing lens 309, a lens barrel 310, and an electron beam gun 3.
11, an electron beam irradiation system, a sample chamber 308, a sub-sample chamber 306, and a reactive gas storage chamber 301. In the conventional example, a reactive gas is used and the GaAs substrate 305 is directly processed by focused electron beam irradiation. That is, the reactive gas is put into the reactive gas storage chamber 301, and the GaAs substrate 305 is set on the sample table 304 and heated. The barrel 310 of the electron beam irradiation system and the sample chamber 308 are evacuated to a high vacuum of about 10 ⁻⁵ Torr or more. The pinhole 307 installed in the sub sample chamber 306 is
It is provided as a passage for maintaining a difference between the inside and outside of the sub sample chamber 306 and for irradiating the GaAs substrate 305 with the electron beam 302.

Sub-sample chamber 306 and reactive gas storage chamber 301
And a sample chamber 308.
Is evacuated, the interior of the sub-sample chamber is evacuated through the pinhole 307. Reactive gas is pipe 30
3 and the micro nozzle 312 at the tip of the sub sample chamber 3
The inside of 06 is filled with the reactive gas. The heated electron beam 302 is irradiated onto the heated GaAs substrate 305 through the pinhole, and the irradiated GaAs substrate is etched.

Since such electron beam assisted etching is an irradiation that irradiates an electron which is 10,000 times lighter than an ion, there is no damage due to ion bombardment unlike the conventional dry etching method using ion irradiation. Etching can be done with very low damage.

[0006]

However, in the above-mentioned conventional technique, gas etching occurs even in the electron beam non-irradiated portion by supplying the reactive gas. Since the gas etching is isotropic etching, side etching occurs at the etching portion, and thus the conventional example is difficult to apply to the nanometer level pattern formation in which the quantum effect appears.

An object of the present invention is to provide a dry etching method capable of etching only an electron beam irradiation portion without side etching, thereby enabling ultrafine processing.

[0008]

The dry etching method of the first invention is a compound semiconductor substrate in which a group 3-5 compound semiconductor substrate is irradiated with a focused electron beam in a reactive gas or radical atmosphere containing a halogen atom. In the dry etching method of directly processing, the oxygen gas or the oxygen radical is added to the reactive gas or the radical atmosphere.

In the dry etching method of the second invention, the shower head-like electron beam is irradiated to the Group 3-5 compound semiconductor substrate through the opening of the mask material patterned in a reactive gas or radical atmosphere containing a halogen atom. By doing so, in the dry etching method for processing the compound semiconductor substrate, oxygen gas or oxygen radicals are added to the reactive gas or radical atmosphere.

[0010]

In the present invention, oxygen (O ₂ ) gas or oxygen radicals are added to a reactive gas or radical atmosphere containing a halogen atom, whereby etching proceeds while the etching sidewall is oxidized. Therefore, since the etching side wall is always protected by the oxide film, side etching due to gas etching is suppressed and only the electron beam irradiation portion can be etched.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the main part of an electron beam assisted etching apparatus used in the first embodiment of the present invention.

This apparatus comprises an electron beam irradiation system consisting of an electron beam gun 101, a focusing lens 102, and a lens barrel 104, a sample chamber 108, and a minute nozzle 106 for introducing a reactive gas 105. Although not shown, the fine nozzle 106 constitutes the tip of a pipe connected to the reactive gas storage chamber.

In the first embodiment, the GaAs substrate 107
Is placed on the sample table in the sample chamber 108, the GaAs substrate 107 is heated to 60 ° C., and the reactive gas 105, which is a mixture of chlorine gas and oxygen gas, is discharged from the minute nozzle 106 to GaAs.
The thin film region having a width of 0.1 μm and a length of 100 μm was irradiated with a focused electron beam 103 having an accelerating voltage of 5.6 keV from the electron beam irradiation system for 5 minutes to perform etching.

At this time, the chlorine gas pressure near the surface of the GaAs substrate 107 was 1 × 10 ⁻³ Torr, and the reactive gas 105 was mixed at a mixing ratio of 80% chlorine gas and 20% chlorine gas. As a result, the etching sidewall was not side-etched, and an etching groove having a width of 0.1 μm could be formed at a depth of 50 nm over a length of 100 μm as in the electron beam irradiation region. Similar effects were obtained by using a shower-shaped electron beam instead of the focused electron beam in the first embodiment.

FIG. 2 is a block diagram showing the main part of the electron beam assisted etching apparatus used in the second embodiment of the present invention.

This apparatus is equipped with an electron beam irradiation system consisting of an electron beam gun 201 and a lens barrel 202, a sample chamber 208 and a nozzle 205 for introducing a reactive gas 204. The nozzle 205 constitutes the tip of a pipe (not shown) connected to the reactive gas storage chamber.

In the second embodiment, the GaAs substrate 207 is used.
Is placed on the sample table in the sample chamber 208, the GaAs substrate 207 is heated to 60 ° C., the reactive gas 204 in which chlorine gas and oxygen gas are mixed is introduced from the nozzle 205 to the surface of the GaAs substrate 207, Etching was performed by irradiating a shower-shaped electron beam 203 with an accelerating voltage of 1.0 keV from the beam irradiation system for 5 minutes through the opening of the patterned mask 206.

At this time, the chlorine gas pressure near the surface of the GaAs substrate 207 was 1 × 10 ^-3 Torr, and the reactive gas 204 was mixed at a chlorine gas ratio of 80% and an oxygen gas ratio of 20%. As a result, the etching sidewall was not side-etched, and the pattern of the mask 206 could be etched in the GaAs substrate 207 at a depth of 50 nm.

[0020]

As described above, in the dry etching method according to the present invention, since only the electron beam irradiation portion can be etched without side etching by gas etching, the electron beam diameter is focused to about 10 nm for etching. By doing so, ultrafine processing of the compound semiconductor substrate is possible. Therefore, the present invention can be applied to nanometer-level pattern formation in which the quantum effect appears.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electron beam assisted etching apparatus used in a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an electron beam assisted etching apparatus used in a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an electron beam assisted etching apparatus used in a conventional example.

[Explanation of symbols]

 101, 201, 311 electron beam gun 102, 309 focusing lens 103, 302 focused electron beam 104, 202, 310 lens barrel 105, 204 reactive gas 106 micro nozzles 107, 207, 305 GaAs substrate 108, 208, 308 sample chamber 203 shower Electron beam 205 Nozzle 206 Mask 301 Reactive gas storage chamber 303 Piping 304 Sample stage 306 Sub-sample chamber 307 Pinhole

Claims (2)

[Claims] 1. A dry etching method for directly processing a compound semiconductor substrate by irradiating a group 3-5 compound semiconductor substrate with a focused electron beam in a reactive gas or radical atmosphere containing a halogen atom, wherein: A dry etching method characterized by adding oxygen gas or oxygen radicals to a radical atmosphere. 2. A compound semiconductor substrate is processed by irradiating a Group 3-5 compound semiconductor substrate with a shower-like electron beam through an opening of a mask material patterned in a reactive gas or radical atmosphere containing a halogen atom. In the dry etching method described above, oxygen gas or oxygen radicals are added to the reactive gas or radical atmosphere.