JPH01316931A - Fine pattern formation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to substrate processing for forming semiconductor integrated circuits.

The present invention relates to fine pattern forming methods used in thin film processing, and particularly relates to processing methods such as etching and thin film formation using focused ion beams.

[Conventional technology]

In order to increase the density and speed of semiconductor integrated circuits, miniaturization of elements is being considered. To achieve this, it is important to establish microscopic and high-precision semiconductor substrate processing and thin film processing technology. Focused ion beam technology has the potential to be optimal for this type of purpose, and it is expected that the technology will be established in terms of both equipment and processing technology. In other words, a pattern can be created by electrically freely deflecting a finely focused ion beam. Selective ion implantation can be performed by selecting the ion species, and etching and thin film formation can be performed by utilizing the kinetic energy of ions. In particular, etching and thin film formation that utilize the kinetic energy of ions is a major feature of focused ion beam processing that is not found in electron beam methods, which can similarly create patterns.

[Problem to be solved by the invention]

A focused ion beam device ionizes gas or liquid metal near a needle-shaped electrode to which a high electric field is applied, focuses it with an electrostatic lens, and creates a pattern of any shape on a sample by electrostatic deflection. Among the aberrations of an ion optical system that represent focusing characteristics, in an electrostatic optical system, chromatic aberration generally well represents the focusing characteristics of the system. Chromatic aberration is approximately inversely proportional to ion energy and proportional to ion energy dispersion and ion gun opening angle, and it is necessary to reduce chromatic aberration in order to obtain a finely focused beam. The ion energy dispersion is determined by the principle of ion generation, and the ion gun opening angle, which is proportional to the ion current, is determined by the required processing speed. is difficult.

Therefore, in order to obtain a finely focused beam, it is necessary to increase the ion energy. In a focused ion beam device using liquid metal Ga, a focused beam with a diameter of 0.3 μm is obtained with an energy of 30 keV, but in order to obtain a focused beam with a diameter of 0.1 μm under these conditions, 1
It is necessary to set the energy to 00 keV.

On the other hand, from the aspect of processing using focused ions, in an ion energy range higher than necessary, processing efficiency is not only reduced, but also problems such as damage to the substrate occur. For example, in the S1 sputtering using a focused Ga ion beam, the sputtering yield is 2 at OrrV at 30 keV.
'ion can be obtained, but with 100 keys, the sputtering yield decreases to latom/ion. Furthermore, Ga is implanted as an unnecessary impurity into the lower part of the etching region, and defects such as voids are formed.

To solve this problem, it is conceivable to apply a positive bias voltage to the sample to achieve a finely focused beam with high energy as an ion optical system, while effectively obtaining low ion energy at the sample surface.

However, in addition to the mechanism for moving the sample with high precision, it also has to be electrically suspended at high voltage, which poses many practical obstacles.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to easily and simply form fine patterns with high reliability by using molecular ions as focused ions. The purpose of the present invention is to provide a method for forming fine patterns.

[Means to solve the problem]

The fine pattern forming method according to the present invention uses molecular ions composed of three or more atoms as focused ions when processing the surface of a sample by irradiating the sample with finely focused ions.

[Effect]

In the present invention, the characteristics of the ion optical system that forms fine focused ions are utilized, and processing is performed using energy suitable for processing.

〔Example〕

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

The figure shows an outline of the principle for explaining an embodiment of the fine pattern forming method according to the present invention. In the figure, 1 is a molecular ion, 2 is a sample substrate, and 11 is an atom constituting the molecule. The accelerated and focused molecular ions 1 collide with the sample substrate 2 and are split into molecular constituent atoms 11 on the substrate surface. The kinetic energy E of a molecular ion is expressed by the following equation using the mass M and velocity V of the molecule.

E=(1/2)・(MY) ・・・・・・(
1) Also, a molecule is composed of n atoms, and its mass is m
If l (1=l~n), it can be said that the velocity of each individual atom is the same as the velocity of the molecular ion immediately after the collision, so Es=(1/2)・(rntV2) sa・
es(2) From equations (1) and (2), El == (mt 7M) 'E
@ @ * 1111 (3) In other words, when the molecular ion 1 collides with the sample substrate 2 and is split, the kinetic energy of the molecular ion 1 is distributed to the individual atoms 11 that make up the molecule according to the texture ratio. Which indicates that.

Benzene (C6 as molecular ion (energy 1:) 1
When this is split into individual atoms 11 by collision with the sample substrate 2, the energy of carbon (C) is 0.15E, the energy of hydrogen (H) is 0, and OIK. Therefore, the molecular ion 1 is accelerated and focused at 100 keV, which is suitable for the ion optical system, to form a finely focused beam, and on the surface of the sample substrate 2, carbon is accelerated at 15 keV, and hydrogen is at 1 keV.
V and energy suitable for processing. Similarly, trisilane ion (St3H8”, energy: E)
In the case of 0.3E for silicon (Sl) and hydrogen (H)
Then it becomes 0.01 E.

A first embodiment of the present invention is the sputter etching of a nickel film (Nt) by a focused trisilane ion beam (Si, H8'').

Silicon ion (81”) is an ion of a simple element.

In sputter etching using hydrogen ions (H+), the ion energies at which the sputtering rate becomes maximum are 40 keV and 1 keV, respectively. If each ion is generated individually, accelerated and focused, it is difficult to form a fine ion beam as described above. In response, trisilane ions are generated and the ion energy 'e
By accelerating and focusing to 100 keV, it becomes a fine ion beam of 0.1 μm, and moreover, the ion beam is 30 keV on the substrate surface due to silicon (Si).

Water X(H) can provide an ion energy of 1 keV, which is suitable for sputter etching. Therefore, fine and high-speed sputter etching of the nickel film becomes possible.

The second embodiment of the present invention uses nitrogen oxide ions (H204+
) is the ion beam assisted etching of the resist.

First, a silicon substrate coated with resist is heated to an appropriate temperature.
It is maintained at oxygen gas pressure to adsorb oxygen (02) on the surface. Next, nitric oxide ions (N2O4'') focused at 0.5 μm are irradiated with an energy of 30 keV, and etching is performed by supporting the bonding reaction between oxygen and resist constituent atoms such as carbon and hydrogen.The resist surface is divided. Nitrogen (
The energies of N) and oxygen (0) are 7 keV, respectively.
At about 5 keV, highly efficient reactive etching can be realized by reducing sputtering of oxygen, which is a reactive species adsorbed on the surface.

In this processing example, nitrogen ions (N''), oxygen ions (
0+), it is necessary to set the ion energies to 7 keV and 5 keV, respectively, in order to obtain similar processing characteristics. However, under these conditions, the diameter of the focused ion beam is several microns, making it impossible to achieve submicron microfabrication.

Note that although the above-mentioned embodiments have been explained with reference to etching, similar effects can be obtained even when applied to the formation of a finely shaped film by ion beam assisted deposition. In this case, the gas used is, for example, silane, WF6
Alternatively, an elemental gas such as w(co) 6 is used.

〔Effect of the invention〕

As explained above, according to the present invention, when processing a sample surface, by using molecular ions composed of three or more atoms as fine focused ions, the characteristics of the ion optical system that forms focused ions can be improved. Since processing can be performed using energy suitable for processing, reliability is high and fine patterns can be easily formed. Furthermore, by selecting a combination of elements that form molecular ions, extremely excellent effects such as simultaneous ion implantation of multiple elements and unprecedented new processing methods can be obtained.

[Brief explanation of the drawing]

The figure is a diagram showing an outline of the principle for explaining an embodiment of the fine pattern forming method according to the present invention. 1・@φ・Molecular ion, 2...φ sample substrate, 11・φ
...Molecular constituent atoms. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] A method for forming a fine pattern in which the surface of a sample is processed by irradiating the sample with finely focused ions, characterized in that a molecular ion composed of three or more atoms is used as the focused ion.