JPH0472723A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To perform the etching process with high precision in the inner surface direction and vertical direction of a substrate without using any large scale device by a method wherein a reactive gas to form the substrate and a volatile reaction product is fed to the substrate while a conductive pointer is approached near the specific part on the substrate making a gap between the pointer and the substrate capable of starting a current to run for impressing a voltage on the space between them to etch away the substrate. CONSTITUTION:Within the device of this invention composed of a piezoelectric element for moving a pointer 207, a gas containing chamber 203 and a substrate holder 201, a vacuum vessel 205 is exhausted using ClF3 gas 204 for etching Si in a substrate 208 and then the ClF3 gas 204 is fed from a vacuum valve 206. The pointer 207 is controlled by the piezoelectric element 202 while the bias voltage and the current between the pointer 207 and the substrate 208 are controlled by an electric control system 209. In such a constitution, when the pointer 207 is approached near the specific position of the specimen 208 making a gap of about 2nm between the pointer 207 and the specimen 208, the current rapidly starts running to dissociate the surface atoms of the substrate 208 as suspending SiF3 gas so that a rectangular pattern may be formed on the specific position when the ClF3 gas is stopped to be exhausted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of forming a fine pattern using a minute electric field.

(Conventional technology) Conventionally, in the technology of etching the substrate using gas,
This is carried out by the steps shown in FIGS. 3(a) and 3(b). First, the Si substrate 33 is placed in a vacuum and heated to clean the surface, and then a reactive gas such as xeF2 or ClF3 reacts with the atoms constituting the substrate to form volatile reaction products.
is poured onto the substrate to form an adsorbed portion consisting of adsorbed molecules 31 on the substrate surface.

Next, when the substrate surface is irradiated with energetic light, electron beam, or ion beam as shown in FIG. ) 34, the substrate is evacuated and etched.

(Problems to be Solved by the Invention) However, the light, electron beam, and ion beam used to impart energy to the adsorbed molecules 31 in the above method are each subject to certain restrictions. For example, when using light, an appropriate wavelength (energy) is required to cause the substrate atoms to react with the adsorbed molecules, but it is difficult to extract and irradiate only an arbitrary wavelength. There are limits to wavelength. When forming fine patterns with electron beams or ion beams, it is necessary to focus the beam, which requires large-scale and complicated beam accelerators and beam focusing devices.

An object of the present invention is to provide a method for forming a fine pattern that can be etched not only in the plane of a substrate but also in a direction perpendicular to the substrate with high accuracy without requiring a large-scale and complicated device as in the past.

(Means for Solving the Problems) The present invention allows a reactive gas that reacts with atoms constituting the substrate to form a volatile reaction product to flow over the substrate, and furthermore, a tapered conductive needle is connected to the desired surface of the substrate. While the needle is close enough to the substrate that a tunnel current flows between the needle and the substrate, a voltage is applied between the needle and the substrate to create an electric field that spreads over a minute range.
This is a pattern forming method characterized by etching a substrate. Further, the present invention is a pattern forming method characterized in that after the reaction gas molecules are caused to flow onto the substrate and adsorbed, the reaction gas molecules are evacuated to leave only the adsorbed portion on the substrate, and etching is performed by forming the electric field.

Reactive gases that react with atoms constituting the substrate to form volatile reaction products include XeF CI when the substrate is Si.
Fluorine gas such as F, C1□, CCI□F3. for GaAs and InP substrates. CHCl3. A chlorine-based gas such as CCl4 is used.

The conductive needle, which is tapered by electric field polishing or mechanical polishing, is made of metal such as tungsten (W) or platinum (PT), or a substance such as diamond whose surface is coated with metal.

While applying a voltage (several volts) between the needle and the substrate, the needle is brought closer to the substrate surface, and when the distance between the needle and the substrate becomes several angstroms, a current of several nanoamperes flows. Generally, this current is called a tunnel current or field emission current depending on its current/voltage characteristics, and it is easy to measure the magnitude of this current.

The distance between the needle and the substrate can be easily controlled by using a piezoelectric element (PZT). This piezoelectric element (PZT) has a piezoelectric ratio of about 5 angstroms N and is easy to process because it is made of ceramic. Such a device is a scanning tunneling microscope (STM).
It is called a microscope and is normally used to measure minute irregularities on the surface, but in the present invention it is used as a tool when etching the object.

(Operation) The operation of the invention of claim 1 will be explained using FIG. 1. After cleaning the substrate 14 placed in an ultra-high vacuum, a reactive gas that reacts with the atoms 13 constituting the substrate 14 to form volatile reaction products is flowed over the substrate 14. At this time, as shown in FIG.
2 and the rest becomes floating gas 11 in the container. In this state, when the needle 15 is brought close to the substrate surface 13 and a voltage 17 is applied between the substrate 14 and the needle 15, a minimal electric field 16 is formed as shown in FIG. 1(b). Adsorption component 1 under electric field 16
2 and the floating gas 11 react with the substrate atoms 13 to form volatile reaction products 18 which are dissociated from the surface of the substrate 14. Based on the above principle, the extremely small electric field 16 is applied to the surface of the substrate 14,
A fine pattern is formed. Generally, the intensity of the minimum electric field 16 is low, so the etching rate is low and the etching controllability is good.

In the second aspect of the invention, since the floating gas 11 is evacuated, only the adsorbed gas contributes to etching, and only the essential atoms of the substrate are etched.

Therefore, the controllability of the etching rate is extremely good.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 2 is a schematic diagram showing the configuration of an apparatus used in an embodiment of the present invention. This device is composed of a piezoelectric element 202 for moving the needle, a gas storage chamber 203, and a substrate holder 201. In this embodiment, Si etching gas ClF3 gas 204 is used for the substrate 208. First, an embodiment of the invention of claim 1 will be described. 10 inside the vacuum container 205
After evacuation to Torr, CIF gas 204 is passed through vacuum pulp 206 . The needle 207 is controlled using a piezoelectric element 202. Bias voltage and current are controlled through an electrical control system 209 between the needle 207 and the substrate 208. When the bias pressure is set to 1■ and the needle 207 is brought closer to the desired position of the sample 208, the distance between the needle 207 and the sample 208 is 2 nm.
At about this point, the current begins to flow rapidly. As a result, surface atoms dissociate into the substrate 208 as SiF gas, and the vacuum vessel 2
05 floating inside. After stopping the flow of ClF3 gas, the gas in the vacuum container 205 is exhausted. In this example, a rectangular pattern of 50×50 nm and depth of 1.2 nm could be drawn at a desired position.

Next, an embodiment of the invention of claim 2 will be described. The inside of the vacuum container 205 is evacuated to 10 Torr. Thereafter, when ClF3 gas 204 is caused to flow through the vacuum valve 206, CIF molecules are adsorbed onto the substrate 208. Then ClF3
Stop and evacuate to remove floating gas. Next, in the same manner as in the above embodiment, by applying a bias voltage and bringing the needle 207 closer, it was possible to etch the essential atoms of the substrate.

(Effects of the Invention) As described above, according to the present invention, etching can be performed with high precision in the in-plane direction and in the vertical direction of the substrate without requiring a large-scale device unlike the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing fine pattern formation according to the present invention, FIG. 2 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention, and FIG. 3 is a schematic diagram of a conventional technique. . In the figure, 11...Floating gas, 12.31...Adsorption amount, 13°32...Substrate atoms, 14.33...Substrate, 15...Needle, 16...Minimum electric field, 17 ... Voltage, 18.43-... Volatile reaction product, 201...
Substrate holder, 202... Piezoelectric element, 203... Gas storage chamber, 204... CIF, 205... Vacuum container, 206... Vacuum pulp, 207... Needle, 208
...Substrate, 209. ,,Electrical control system.

Claims (1)

[Claims] 1) A reactive gas that reacts with atoms constituting the substrate to form a volatile reaction product is flowed over the substrate, and a tapered conductive needle is applied to a desired portion of the substrate. A pattern forming method characterized by etching by applying a voltage between the needle and the substrate while approaching the needle to a distance where a tunnel current flows between the needle and the substrate to form an electric field that spreads over a minute range. 2) A pattern forming method characterized in that the reactive gas molecules are caused to flow onto the substrate and adsorbed, and then evacuated, and the electric field is formed and etched using only the adsorbed portion on the substrate.