JPS60138092A - Formation of pattern - Google Patents

Abstract

PURPOSE:To enable control of a pattern width with high accuracy by a simple method with a titled method for condensing an energy beam to the surface of an object to be worked in a liquid or gas by controlling the modulating frequency of said beam. CONSTITUTION:The laser beam 42 emitted from an energy source 31 passes through a modulator 32 and is focused by a lens system 33. The focused beam passes through a plating liquid 36 and strikes the surface of a metallic layer 39 on a substrate 38. The modulator 32 is mechanical, for example, rotary light chopper and it is assumed that the chopper is rotated at a certain frequency f1 and frequency f2=2f. The relation between the laser irradiation density and time in a part 45 irradiated with the laser is as shown in the figures (a), (b). Although the irradiation density per pulse of (b) is half the (a), the total energy in a specified time T is constant as the frequency is two-fold. The laser beam modulated to an optional frequency is obtd. while maintaining the specified total energy by changing continuously the rotating speed of the modulator 32 in the above-mentioned way. The width of the pattern to be formed is thus made adjustable with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pattern forming method, and particularly to a method for forming fine patterns on metals, semiconductors, insulators, and the like.

[Background of the invention]

Conventionally, for example, J. Electrochem, SOc
,, 1282539 (1980), when the surface of a substrate immersed in a plating solution is irradiated with laser light, the surface of the substrate is heated, a local temperature rise occurs, the plating rate increases, and selective plating is achieved. is known to be possible.

For example, the prior art disclosed in Japanese Unexamined Patent Publication No. 55-148797 will be described with reference to FIG.

In FIG. 1, cathode 23 is held in an electrolytic plating solution within container 15. In FIG. The source 21 and the modulator 20 are connected to the anode 17
and the cathode 23. energy source 11
is focused by a plunes system 13 through a modulator 12 and passes through an electrolytic plating solution 16 to deposit metal layer 1 on substrate processing 8.
The laser beam 22 striking on 9 is 11,'2. The laser beam 22 is manipulated by the rotation angle of the scanning mirror 14 so as to hit a predetermined portion of the cathode 23.

Laser beam 22. The container 15 may be moved by the stage 24 so as to hit a predetermined portion of the cathode 23 without moving the container 15.

In this conventional technique, the width of the plating film formed in the plating region 25 is determined by the beam diameter and irradiation density of the laser beam 22 in the plating region 25. For example, with a beam diameter of 20 μm, 2×10' Wlcr! By vibrating the mirror 14 at a speed of 1 hour/second using a continuous laser beam 22 having an irradiation density of 9, 9 line turns with a width of 10 μm are formed. If you want to control the width of the line pattern, you can either adjust the output of the energy source 11 to change the irradiation density, or change the lens system 13 to change the laser beam diameter in the plating area 25. It was getting worse. In the former case, if the irradiation density is increased, the thermal spread 9 in the plating area 25 will be increased.
The larger the angle, the wider the turn will be. Furthermore, by changing the focal length of the lens in the lens system 13 and increasing the diameter of the irradiated beam, the pattern width becomes thicker.

In this conventional technique, the pattern width is uniquely determined by the irradiation density and the lens system. Therefore, if a plating film with a new pattern width is to be formed, the output of the energy source 11 must be readjusted or the lens system 13 must be changed. Furthermore, when attempting to form a continuous line, it is impossible to change the pattern width midway.

[Purpose of the invention]

An object of the present invention is to provide a pattern forming method that can form a highly accurate pattern width using a simple device.

[Summary of the invention]

The feature of the present invention that achieves the above object is that even if the energy of the energy beam is constant, the width of the formed pattern is controlled by controlling the modulation frequency.

When an energy beam is applied to a workpiece in a plating or etching medium, liquid or gas, selective plating or etching occurs due to an increase in temperature of the irradiated area.

As shown in FIG. 2, it is assumed that a workpiece 52 is irradiated with a modulated energy beam. At this time, the part ■ where the energy beam 50 is absorbed. , an fcg region Vth occurs outside of , due to the diffusion of heat induced by the energy beam. The size of this heat diffusion region Vth is defined by the box in the figure, and is considered to be close to a semicircle with R as the center. Specifically, R is 1/2 of the increase in plating or etching.

Yumei Moto et al. conducted an experiment to investigate the relationship between this R and the modulation frequency f of the energy beam.

As a result, it was igneously confirmed that R is a function of f. It has also been found that the width of plating or etching can be controlled by the modulation frequency f of the energy beam even if the amount of energy is small.

The present invention provides a pattern forming method in which the width of plating or etching can be arbitrarily set based on the results of the deformation.

[Embodiments of the invention]

A first embodiment of the present invention will be described with reference to FIG.

In FIG. 3, the cathode 43 is held in a copper sulfate-based plating solution 36 in a container 35. Cathode 4 which is the workpiece
3 is a glass substrate 38 and a substrate 38 with a thickness of 0.8 m.
The metal layer 39 is composed of a 500-thickness Cr metal layer formed on one main surface of the metal layer and a 1000-thickness Cu metal layer 39 formed thereon. Power source 41 is connected between anode 37 and cathode 43. The container 35 is held on a stage 44 and is moved by the stage 44 at a constant speed. The laser beam 42 emitted from the energy source 31 is transmitted to the modulator 3
2 , is focused by a lens system 33 , passes through a plating 36 and impinges on a metal layer 39 on a substrate 38 .

Modulator 32 is a mechanical optical chopper as shown in FIG. This optical chopper has a certain frequency lt1. When rotating at f1 and modulating the laser light, the laser irradiated area (
FIG. 3(45) shows the relationship between the laser irradiation density and time, and the upper one is shown in FIG. 5(a).

Further, FIG. 5(b) shows a similar relationship when rotating at a frequency f2=2f1. In Fig. 5(b), the laser irradiation density of 1 pulse 67' (6) is 7 in Fig. 5(a), but since the frequency is doubled, the total energy (in Fig. (the shaded area) remains constant.In this way, by continuously changing the rotational speed of the modulator 32, a laser beam modulated at any frequency can be created with the total energy being constant.This example Here, a mechanical optical chopper with a continuously variable frequency from 1 to 5000H2 was used as the modulator 32.The frequencies ili, n,
The frequency is determined by the frequency control system 45 and can be changed to an arbitrary frequency while the laser beam 42 is being irradiated.

In this embodiment, the energy source 31 is an Ar laser having a wavelength of 488 nm and an output of 110 mW.

The diameter of the laser beam 42 in the plating area 45 is set to 100
The m6 diagram shows the relationship between the frequency and the plating width when the frequency of the modulator 320 is changed when the value is .mu.m.

This figure is a graph showing the IA ratio between the logarithm of the plating width on the vertical axis and the logarithm of the frequency on the horizontal axis. From the graph, Log h=-0,12970gf+L33...
...(1) It can be seen that here h: cut width (μm) f: frequency (H2).

Generally, when the width of anastomosis, plating, or elatin, in which selective plating or etching is performed by irradiating a modulated laser beam onto a workpiece in a liquid or gas, is togh=-λLogf0k...・・・・・・(2
) Here, the inventors experimentally found that λ is a constant.

λ and k are determined by the thermal conductivity of the medium, the absorption efficiency of the energy beam by the medium, the energy beam diameter, the beam irradiation density, the thermal diffusivity of the solid sample, etc. In particular, λ differs depending on the medium. This is because selective plating or etching is only possible when the energy beam 50 (FIG. 2) is irradiated onto the workpiece 52 and the temperature of the medium 53 near the heat generating source Vep increases. It is.

It can be seen that a pattern with the desired width can be obtained by determining a certain frequency given by equation (2).

The value of λ changes depending on the thermal diffusivity of the liquid or gas medium and the thermal conductivity of the workpiece. The present inventors have confirmed that when a material is used, λ takes a value around 0.2.

In this embodiment, the laser beam is irradiated under the above conditions, and the container 15 holding the cathode 23 is moved to 60
It was moved at a speed of μm/leG. At this time, as shown in Figure 7, the modulator 320 frequency is set to 3H2 and the width is 150μ.
After forming pattern A of m, the frequency is set to 2400. H2
It was possible to continuously form pattern B with a width of 60 μm. For example, if a pattern with a width of 100 μm is desired, the laser beam may be modulated at a frequency of 61 Hz according to equation (1).

In this embodiment, the plating solution 36 is shown as an electrolytic plating solution, but a chemical plating solution may also be used.

In this case, the anode 17 is no longer necessary. Also, plating solution 36
may be used as an etching solution.

The medium in which the workpiece is held may be gas instead of liquid.

A second embodiment of the invention will be described with reference to FIG.

The workpiece 63 is held in SiH4 gas 61 within the container 60. Laser beam 42 exiting energy source 31 passes through modulator 32 , is focused by lens system 33 , passes through gas 61 and impinges on workpiece 63 . Si generated by gas decomposition is dry plated only on the laser irradiated portion of the workpiece 63.

In this embodiment, the energy source is mainly a CO2 laser with an output of 5W. At this time, the result of changing the modulation frequency f is the formula (2
), a result of λ=0.5 was obtained.

In the two embodiments of the present invention, an example is shown in which the modulator 32 changes the frequency formula by rotating a mechanical optical chopper, but an optical chopper with a set of shutters may also be used. or,
If a narrower pattern is desired, it is desirable to use an optical modulator with a large frequency range. or,
Even without continuous wave modulation, a modulated laser beam can be obtained by using a pulsed laser as the energy source.

〔Effect of the invention〕

According to the present invention, since the pattern width can be controlled by the convenient method of controlling the frequency equation of the modulator, a desired pattern width can be formed with a simple device.

Furthermore, since the modulation frequency itself is controlled by electrical signals, it is possible to easily program the modulation frequency.

Furthermore, the precision of the pattern width to be formed can be controlled up to several μm, and the V
'':) Patterns can be formed with precision not available from etching and etching techniques.

[Brief explanation of drawings]

Figure 1 shows a conventional technique in which a laser beam is irradiated on the second side of a workpiece where selective plating is performed, and Figure 2 shows a state in which a modulated energy beam is irradiated onto a workpiece. Figure 3 is a diagram showing the first embodiment of the present invention that incorporates a modulator with a control system to form a pattern with an arbitrary plating width, and Figure 4 is a mock-up. Fig. 5 is a diagram showing the relationship between laser irradiation density and time when the laser beam is modulated; Fig. 6 is a diagram showing the main chopper.
The figure shows the frequency of the modulator and the plating width, Fig. 7 shows the actual plating pattern, and Fig. 8 shows the second embodiment of the present invention in which an energy beam is irradiated onto a solid sample in a gas. FIG. 50...Energy beam, 51...Lens, 52
... Workpiece, 53 ... Medium near the beam absorption region, 31 ... Energy source, 32 ... Modulator, 33.
...Lens system, 38...Cathode, 36...Plating solution, 45 1 and 2 figures

Claims (1)

[Claims] 1. Controlling the modulation frequency of the energy beam in a method of selectively forming a pattern by concentrating an energy beam on an arbitrary location on the proboscis of a workpiece in a liquid or gas. A pattern forming method characterized in that the pattern width is controlled by. 2. A pattern forming method according to claim 1, characterized in that the pattern is formed using the solid or gaseous plating medium. 3. The pattern forming method according to claim 1, wherein the number substance or gas is an etching medium. 4. The pattern forming method according to claim 1, wherein the energy beam is a laser beam.