JPH0394426A - Formation of pattern - Google Patents

Abstract

PURPOSE:To execute an ultrafine processing operation by a method wherein a compound semiconductor is processed under a condition of a reactive gas pressure under which an etch rate of a gas etching operation caused by supplying only a reactive gas is set to 10Angstrom /min or lower. CONSTITUTION:While a reactive gas containing halogen atoms is being supplied, a III-V compound semiconductor substrate 107 is irradiated with a focused electron beam 103 to directly process the compound semiconductor. At this time, the semiconductor is processed under a condition of a reactive gas pressure under which an etching rate of a gas etching operation caused by supplying only a reactive gas is set to 10Angstrom /min or lower. In this case, it is suitable that chlorine gas is used as the reactive gas and that a condition of a chlorine gas pressure is selected in such a way that a product of a substrate temperature multiplied by a chlorine gas pressure value is 1.2X1-<-2> deg.C.Torr or lower. Thereby, an ultrafine processing operation can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a pattern of a compound semiconductor using an electron beam, and more particularly to a method for forming a pattern with nanometer level precision.

[Conventional technology]

(2) Pattern formation on V group compound semiconductors is important in semiconductor processing. Particularly recently, pattern formation at the nanometer level, where quantum effects appear, has been attracting attention. As a method for forming such nanometer-level patterns, chlorine gas assisted etching using a focused electron beam is proposed in Japanese Patent Application No. 300785/1985. FIG. 3 is a schematic diagram of an electron beam assisted etching apparatus used in this conventional example.

This electron beam assisted etching apparatus consists of an electron beam irradiation system consisting of a converging lens 309, a lens barrel 310, and an electron beam gun 311, a sample chamber 308, a sub-sample chamber 306, and a reactive gas storage chamber 301. There is. In the conventional example, a reactive gas is used to directly process the substrate 305 by focused electron beam irradiation. That is, a reactive gas is put into the reactive gas storage chamber 301, and the substrate 3 is
05 is set on the sample stage 304 and heated. The lens barrel 310 of the electron beam irradiation system and the sample chamber 308 are heated to 10-' Torr.
Evacuate to a high vacuum level or higher. A bin hole 307 installed in the sub-sample chamber 306 is installed to maintain a difference between the inside and outside of the sub-sample chamber 306 and as a passage for irradiating the electron beam 302 onto the substrate 305. Sub sample room 3
06 and the reactive gas storage chamber 301 are connected by a pipe 303', and by evacuating the sample chamber 308, the inside of the sub-sample chamber is evacuated through the pinhole 307. The reactive gas passes through the pipe 303 and the micro nozzle 312 at its tip, and the inside of the sub-sample chamber 306 is filled with the reactive gas. The heated substrate 305 is irradiated with a focused electron beam through the via hole, and the substrate at the irradiated location is etched.

This type of electron beam assisted etching uses electrons that are more than 10,000 times lighter than ions, so there is no damage caused by ion bombardment like in conventional dry etching that uses ion irradiation, resulting in extremely low damage. It is.

[Problem to be solved by the invention]

In conventional techniques, by supplying a reactive gas to a heated substrate, gas etching occurs even in areas not irradiated with an electron beam.

For example, when the substrate is a GaAs substrate 314, chlorine gas 313 is used as a reactive gas, and assisted etching is performed using an electron beam 302 for 5 minutes at a GaAs substrate temperature of 70°C and a chlorine gas pressure of I X 10-'Torr. A cross-sectional view of the GaAs substrate 314 is shown in FIG.

In this example, the assisted etching amount d of the electron beam irradiation area is
2 was 1,000 people, and the gas etching amount d of the area not irradiated with the electron beam was 1,500 people. In this way, etching occurs even in areas that are not irradiated with the electron beam, so the conventional example cannot be said to be maskless etching. In particular, it is difficult to apply conventional methods to nanometer-level pattern-shaped commands where quantum effects appear.

An object of the present invention is to provide a pattern forming method that can etch only the electron beam irradiated area, thereby enabling ultra-fine processing.

[Means for solving problems]

The present invention provides a pattern-forming method in which a compound semiconductor is directly processed by irradiating a focused electron beam while supplying a reactive gas containing a halogen atom to a group I-III compound semiconductor, in which only the reactive gas is supplied. The process is characterized in that processing is carried out under conditions of the reactive gas pressure such that the etching rate of the gas etching that occurs is 10 Å/min or less.

In the case of the present invention, the reactive gas is chlorine gas, and the chlorine gas pressure condition is such that the product of the substrate temperature and the chlorine gas pressure value is 1.2X.
It is preferable to select it so that it is 10-''°C-Torr or less.

[Effect]

In the present invention, by controlling the gas pressure of the reactive gas containing halogen atoms near the surface of the ■-V group compound semiconductor,
Gas etching of the electron beam irradiated area is suppressed and only the electron beam irradiated area can be etched.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the main parts of an electron beam assisted etching apparatus used in one embodiment of the present invention.

This device includes an electron beam gun 101 and a converging lens 102.
, an electron beam irradiation system consisting of a lens barrel 104, and a sample chamber 10.
8 and a micro nozzle 106. Micro nozzle 1
Although not shown, 06 constitutes the tip of a pipe connected to the reactive gas storage chamber.

In this example, a GaAs substrate 107 is placed on a sample stage in a sample chamber 108, and the GaAs substrate 107 is heated at 60°C.
chlorine gas 105 from a micro nozzle 106.
The electron beam 103 was introduced onto the surface of the As substrate 107, and a rectangular area of 100 μm×20 μm was irradiated with a focused electron beam 103 from an electron beam irradiation system at an acceleration voltage of 5.6 keV for 5 minutes to perform etching.

At this time, the chlorine gas pressure near the surface of the GaAs substrate 107 was IXIO-'Torr, and no gas etching was observed in the portion of the GaAs substrate that was not irradiated with the electron beam. On the other hand, an etching depth of 200 mm was obtained in the electron beam irradiated area.

FIG. 2(a) shows the relationship between the assist etching amount dz of the electron beam irradiated area and the gas etching amount d1 of the non-electron beam irradiated area with respect to the chlorine gas pressure near the surface of the GaAsi plate heated to 60°C in this example. An example of measurement data is shown.

When the chlorine gas pressure is higher than 2 XIO-' Torr, the gas etching rate in the area not irradiated with the electron beam is 10
The etching rate becomes larger than 50 Å/min, and becomes approximately the same as the assisted etching rate of the electron beam irradiated portion, which is 50 Å/min. On the other hand, when the chlorine gas pressure is 2 XIO-'Torr or less, the gas etching rate is suppressed to 10 Å/min or less, but the etching reaction between the chlorine gas and GaAs is excited in the electron beam irradiation part, and electron beam assisted etching occurs.

By controlling the chlorine gas pressure as described above, only the electron beam irradiated portion can be etched.

Further, electron beam assisted etching was performed while changing the substrate temperature from 60°C to 100°C, and the assisted etching amount d2 and the gas etching amount d1 were measured. FIG. 2(b) shows the selectivity ratio (aX/dI) of the etching amount with respect to the product of the substrate temperature and the chlorine gas pressure. From this figure, the product of the substrate temperature value and chlorine gas pressure value is 1.2X10-
The selection ratio (ax/dl) is 10 or more at a temperature of 10° C.-Torr or less, that is, only the region irradiated with the electron beam is etched.

In a region larger than 1.2×10 −2° C. Torr, gas etching becomes comparable to assisted etching, and the selectivity (a./d.) decreases significantly.

〔Effect of the invention〕

According to the present invention, since only the electron beam irradiation part can be etched, ultra-fine processing is possible by converging and etching the electron beam diameter to about 100 people.

Therefore, the present invention can be applied to nanometer level pattern formation where quantum effects appear.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an electron beam assisted etching device used in an embodiment of the present invention, Fig. 2 is an example of measurement data in an embodiment, and Fig. 3 is a schematic diagram of an electron beam assisted etching device used in a conventional example. FIG. 4 is a cross-sectional view of a GaAs substrate subjected to conventional electron beam assisted etching. 101, 311...electron beam gun 102. 30
9... Converging lens 103, 302... Electron beam 104, 310... Lens barrel 105, 313... Chlorine gas 106, 312... Micronozzle 107, 305, 314... GaAs substrate 108,
308...Sample chamber 301...Reactive gas storage chamber 303...
...Piping 304 ...Sample table 306 ...Sub-sample chamber 307 ...Binhole O1 electronic camera ↓ Viewing diagram 1

Claims (2)

[Claims] (1) In a pattern forming method of directly processing a III-V compound semiconductor by irradiating the compound semiconductor with a focused electron beam while supplying a reactive gas containing a halogen atom, the method comprises: supplying only the reactive gas; A pattern forming method characterized in that processing is carried out under conditions of the reactive gas pressure such that the etching rate of the gas etching that occurs is 10 Å/min or less. (2) The reactive gas is chlorine gas, and the chlorine gas pressure condition is that the product of the substrate temperature and chlorine gas pressure value is 1.2 x 10^
2. The pattern forming method according to claim 1, wherein the pattern forming method is selected so that the temperature is -^2[deg.] C.-Torr or less.