JP2000058490A - Forming method of nano-structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a nano-structure to be effectively and precisely formed through a simple means by a method wherein a prescribed part of a silicon oxide film formed on a silicon substrate is irradiated with an electron beam at a certain energy level lower than a specific value to be removed from the substrate to make the surface of the substrate exposed. SOLUTION: A prescribed site of a silicon oxide film formed on a silicon substrate in one piece is irradiated with a low energy electron beam lower than 200 eV, whereby a prescribed part of the silicon oxide film is removed from the substrate without using a resist film. When a silicon oxide film formed on a silicon substrate is irradiated with an electron beam of low energy, it gets more reactive than it is irradiated with an electron beam of high energy. Therefore, a silicon oxide film can be effectively removed. Furthermore, a special equipment or a special device required for accelerating electrons in the case where an electron beam of high energy is used can be dispensed with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a nanostructure. More specifically, the invention of this application provides a new, highly accurate, reliable nanoscale structure for lithography and the formation of nanostructures in semiconductor devices without the use of resist agents. The present invention relates to a method for forming a nanostructure.

[0002]

2. Description of the Related Art With the advance of semiconductor fine processing technology, establishment of nano-scale processing technology has become an important issue. As one of such nano-scale processing techniques, irradiation of a silicon oxide film (SiO ₂ / Si) disposed on a silicon substrate with a focused high energy electron beam using a scanning or transmission electron microscope. Has proposed a method of removing a silicon oxide film, opening a window, and growing silicon or germanium nanoparticles on an exposed silicon substrate surface (K. Fujita et.
al., Appl. Phys. Lott. 70 (1997) 2807; AA Shklyaev e
etal., Appl. Phys. Lett. 72 (1998) 320, etc.).

This method enables lithography without using a resist film and formation of a nanostructure on the surface of a silicon substrate. However, in the processing method of nanosur using the electron beam as described above,
Since a high energy electron beam of about 30 KeV to 300 KeV is used, there is a disadvantage that the reactivity with a silicon oxide film is low, and as a result, the efficiency of nanostructure formation is low. There was a drawback that equipment was required.

[0004] Therefore, it is desired to increase the reactivity with the silicon oxide film on the surface of the silicon substrate to improve the removal efficiency of the silicon oxide film, and to enable the formation of nanostructures by simpler means. Was.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present application solves the above-mentioned drawbacks of the prior art and proposes a more efficient, highly accurate, highly reliable, and simple method for nanostructures. To form, the following invention is provided. That is, first of all, the invention of this application is:
A predetermined portion of the silicon oxide film disposed on the silicon substrate is irradiated with a low energy electron beam of 200 eV or less to remove the silicon oxide film and form a nanostructure exposing the silicon substrate surface. And a method for forming a nanostructure.

Further, the invention of this application is a method of irradiating a low energy electron beam by heating a silicon substrate to a temperature of 750 ° C. or less in the above method, and the low energy electron beam is an STM tunneling electron beam. A method is also provided. Further, the invention of this application is characterized in that a thin film of an element or a compound is provided on the exposed silicon substrate surface in the nanostructure formed by any one of the first to third methods. And a method of depositing a metal thin film in this method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the features as described above, and the embodiments of the invention will be described in more detail below. In the method of forming a nanostructure according to the present invention, first, a predetermined portion of a silicon oxide film provided and integrated on a silicon substrate is irradiated with a low energy electron beam to remove the silicon oxide film, For example, the surface of the silicon substrate is exposed by opening a window in the silicon oxide film.

An important feature of the present invention is that the silicon oxide film is removed by irradiating a low-energy electron beam without using a resist film as in the prior art. In this case, the low energy electron beam has an energy of 200 eV or less. For example, an electron beam having an energy of 50 eV to 200 eV is considered. Such a low-energy electron beam can be used, for example, as a beam of a tunnel current such as a field emission current by an STM (scanning tunneling electron microscope).

For example, when the STM tunnel current beam is used, generally, the distance between the tip of the tip (STM needle) and the silicon oxide film is 200 nm or less.
For example, in the range of 5 to 50 nm, the current (field em)
It is considered that the current range is from 1 nA to 100 nA. It is considered that the bias voltage applied to the STM chip is, for example, 50 to 200V.

When removing silicon oxide by irradiation with a low energy electron beam, it is effective to heat the silicon substrate. The heating may be performed at the time of irradiation with the electron beam, or may be performed before the irradiation. It is generally considered that the heating temperature is 750 ° C. or less, for example, 200 to 750 ° C., and further 400 to 750 ° C.

By irradiating a low-speed, low-energy electron beam, a silicon oxide film (Si
O ₂ ) has a much higher reactivity than the conventional high energy electron beam irradiation of about 30 KeV to 300 KeV, and the silicon oxide film is efficiently removed. Also, unlike the case of high energy electron beam irradiation, there is no need for special equipment or equipment for acceleration.

[0012] By the irradiation of the low energy electron beam,
Predetermined portions of the silicon oxide film can be selectively removed on a nanoscale, and a required pattern can be formed efficiently. In the nanolithography of the present invention as described above, the thickness of the silicon oxide film disposed and integrated on the silicon substrate is not particularly limited, but is generally 0.5 to 3.0 nm. Considered as a degree.

An element or a compound can be provided on an exposed silicon substrate surface as a window or the like in a silicon oxide film obtained by nanolithography. This arrangement can be achieved by a method such as, for example, selective CVD (chemical vapor deposition) or selective electrochemical deposition, and furthermore, atomic deposition by field emission from the tip of the STM needle.

For deposition, for example, W (tungsten),
Specific examples thereof include metals such as Al (aluminum) and Cu (copper) suitable for wiring and the like, and compounds such as silicide. The deposition of elements or compounds on the exposed silicon substrate results in the formation of three-dimensional functional nanostructures. According to the method of the present invention as described above, a process technology for producing a new semiconductor device on a nanoscale is provided.

The present invention will be described in more detail with reference to the following examples.

[0016]

EXAMPLE A sample in which a silicon oxide film (SiO ₂ ) having a thickness of about 0.5 nm was formed on a silicon substrate was used. FIG. 1 shows an STM image (Vb = + 4.0 V, I
_t = 0.3 nA, Scanning speed 18.3 nm / s)
It is shown. A region surrounded by a white line in the drawing is a region defined as an electron beam irradiation region.

This sample was heated and held at 700 ° C.
The tip (needle) is moved to the center of the above area, and the distance between the tip of the STM tip and the surface of the silicon oxide film of the sample is set to 1
It set so that it might be in the range of 00-200 nm. The heating temperature of the silicon substrate was maintained at 700 ° C., and the electron beam was irradiated for 60 seconds under the conditions of the bias voltage of the STM chip of 150 V and the field emission current of 50 nA. The energy of the electron beam at this time was 150 eV, which was much lower than the conventional electron beam.

FIG. 2A shows the state of S after the electron beam irradiation.
FIG. 2B shows a TM image, and FIG. 2B is an enlarged view thereof. It can be seen that the silicon oxide film has been removed in the region surrounded by the white line in FIG. The state where the silicon oxide film was removed and the window was opened was formed. It was confirmed that the surface of the silicon substrate was exposed at the window and that the edge of the window was extremely sharp.

FIG. 3 is an STM image showing the result of etching the silicon oxide film by changing the field emission current following the operation of FIG. The area A in FIG.
The window shown in FIG. Region B is a region irradiated with an electron beam at a bias voltage of 150 V and a field emission current of 25 nA for 120 seconds. Region C is a region irradiated with a bias voltage of 150 V.
V, a region irradiated with an electron beam for 200 seconds at a field emission current of 5 nA is shown.

FIG. 4 is an enlarged view of the area C. In the region C, a window having a diameter of about 70 nm is opened to expose the silicon substrate surface. The energy of the electron beam forming the region B is 150 eV, and the energy of the electron beam forming the region C is also 150 eV. In the above examples, it is understood that the use of the low energy electron beam allows the surface of the silicon substrate to be efficiently and accurately exposed by removing the silicon oxide film.

[0021]

As described above in detail, according to the invention of this application, the silicon substrate surface can be efficiently and accurately exposed by removing the silicon oxide film, and nanolithography can be performed without using a resist film. Becomes Then, wiring metal and the like are provided on the exposed silicon substrate surface.

Therefore, the present invention makes it possible to efficiently form a highly reliable nanostructure.

[Brief description of the drawings]

FIG. 1 is a photograph of an STM image instead of a drawing showing a surface silicon oxide film of a sample.

FIGS. 2A and 2B are an STM image photograph and an enlarged photograph in place of a drawing as an example.

FIG. 3 is an STM image photograph in place of a drawing as an example, in which a continuous operation is performed.

FIG. 4 is an enlarged photograph of a region C in FIG. 3;

Claims (5)

[Claims] 1. A nanostructure in which a predetermined portion of a silicon oxide film provided on a silicon substrate is irradiated with a low energy electron beam of 200 eV or less to remove the silicon oxide film and expose a surface of the silicon substrate. A method for forming a nanostructure, comprising: forming a nanostructure; 2. The method according to claim 1, wherein the silicon substrate is heated to a temperature of 750 ° C. or less and irradiated with a low energy electron beam. 3. The method according to claim 1, wherein the low energy electron beam is a beam of STM tunneling electrons. 4. A method for forming a nanostructure, comprising: disposing a thin film of an element or a compound on an exposed silicon substrate surface of the nanostructure formed by the method according to claim 1. 5. The method according to claim 4, wherein a metal thin film is deposited.