JPS6334236B2 - - Google Patents

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, e.g. J.Electrochem.Soc., 128 2539
(1980), when a laser beam is irradiated onto a substrate surface immersed in a plating solution, the substrate surface is heated, a local temperature rise occurs, the plating speed increases, and selective plating occurs. It is known that it is possible.

For example, the prior art disclosed in Japanese Patent Application Laid-Open No. 148797/1982 will be described with reference to FIG.

In FIG. 1, cathode 23 is held in electrolytic plating solution within container 15. In FIG. Power supply 21 and modulator 2
0 is connected between the anode 17 and the cathode 23. Energy source 11 passes through modulator 12 and is focused by lens system 13 to form a laser beam 22 that passes through electrolytic plating solution 16 and impinges on metal layer 19 on substrate 18 . laser beam 2
2 is operated by the rotation angle of the scanning mirror 14 so as to hit a predetermined portion of the cathode 23.
The container 15 may be moved by the stage 24 so that the laser beam 22 hits a predetermined portion of the cathode 23 without moving.

In this prior art, 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×
A line pattern with a width of ^{10 μm} is formed by vibrating the mirror 14 at a speed of 1 mm/sec using a continuous laser beam 22 having an irradiation density of 10 5 W/cm ² . If you want to control the width of the line pattern here, you can adjust the output of the energy source 11 to change the irradiation density, or use the lens system 13
Either method has been used in which the diameter of the laser beam in the plating area 25 is changed by changing the diameter of the laser beam in the plating area 25.
In the former case, increasing the irradiation density will reduce the plating area to 25
Thermal spread in the pattern increases, and the pattern width increases. Furthermore, by changing the focal length of the lens in the lens system 13 to increase the diameter of the irradiated beam, the pattern width can be increased.

In this prior art, the pattern width is uniquely determined by the irradiation density and the lens system. Therefore, if a plated 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]

A 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 irradiated onto a workpiece in a liquid or gas as a plating or etching medium,
Selective plating or etching occurs due to the increased 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, a region V _th where heat induced by the energy beam is diffused is generated outside the portion V _pp where the energy beam 50 is absorbed. The size of this heat diffusion region V _th is defined by R 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.

The present inventors conducted an experiment to investigate the relationship between this R and the modulation frequency of the energy beam. As a result, it was experimentally confirmed that R is a function of . They have also found that the width of plating or etching can be controlled by the modulation frequency of the energy beam even if the energy is constant.

Based on this result, the present invention provides a pattern forming method in which the width of plating or etching can be arbitrarily set.

[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. The cathode 43 that is the workpiece is a glass substrate 3 with a thickness of 0.8 mm.
8 and a 500 Å thick Cr formed on one main surface of the substrate 38, and a 1000 Å thick Cr formed thereon.
It is composed of a metal layer 39 of Cu. power supply 41
is connected between the anode 37 and the 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 liquid 36, and impinges on a metal layer 39 on a substrate 38.

Modulator 32 is a mechanical optical chopper as shown in FIG. When this optical chopper is rotated at a certain frequency ₁ to modulate the laser beam, FIG. 5a shows the relationship between the laser irradiation density and time at the laser irradiated area (FIG. 3, 45).
Further, FIG. 5b shows a similar relationship when rotating at a frequency of ₂ = ₂₁ . The laser irradiation density per pulse in Figure 5b is 1/2 of that in Figure 5a, but since the frequency is twice as high, the total energy amount (the shaded area in the figure) over a certain period of time T is constant. be. In this way, by continuously changing the rotational speed of the modulator 32, a laser beam modulated at any frequency can be created with a constant total energy. In this embodiment, a mechanical optical chopper whose frequency is continuously variable from 1 to 5000 Hz is used as the modulator 32. The frequency is determined by a 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 has a wavelength of 488 nm,
It is an Ar laser with an output of 110mW. The diameter of the laser beam 42 in the plating area 45 is 100 μm.
FIG. 6 shows the relationship between the frequency and the plating width when the frequency of the modulator 32 is changed.

This figure is a graph showing the relationship between the logarithm of plating width on the vertical axis and the logarithm of frequency on the horizontal axis. From the graph, it can be seen that log h=-0.129log+2.33 (1) where h: plating width (μm); frequency (Hz).

In general, when selective plating or etching is performed by irradiating a workpiece in liquid or gas with a modulated laser beam, the width of plating or etching is h, log h=-λ log+k......( 2) The inventors have experimentally found that λ and k are constants here.

λ and k are constants 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 varies depending on the medium. Because selective plating or etching requires energy beam 50
(Fig. 2) is irradiated onto the workpiece 52, and the heat generation source
This is because plating or etching becomes possible only when the temperature of the medium 53 in the vicinity of V _pp rises.

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

The value of λ is the thermal diffusivity of the liquid or gas medium,
Although it varies depending on the thermal conductivity of the workpiece, for example, when using a workpiece with a metal thin film deposited on a glass substrate using a simple dulling solution of copper sulfate, λ
The inventors have confirmed that the value is 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 the stage 2.
4 at a speed of 60 μm/sec. At this time, as shown in FIG. 7, the frequency of the modulator 32 is set to 3 Hz to form a pattern A with a width of 150 μm, and then the frequency is changed to 2400 Hz to form a pattern B with a width of 60 μm.
could be formed continuously. For example, if you want a pattern with a width of 100 μm, use formula (1)
It would be better to modulate the laser beam at a frequency of 61Hz.

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. Further, the plating solution 36 may be used as an etching solution.

The medium in which the workpiece is held may be gas rather than liquid.

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

The workpiece 63 is SiH ₄ gas 61 in the container 60.
held inside. A laser beam 42 from an energy source 31 passes through a modulator 32, is focused by a lens system 33, passes through a gas 61, and impinges on a workpiece 63. Si generated by gas decomposition only on the laser irradiated part on the workpiece 63
is dry plated.

In this example, the energy source is _CO2 with an output of 5W.
It's a laser. At this time, as a result of changing the modulation frequency, a result of λ=0.5 in equation (2) was obtained.

In the two embodiments of the present invention, an example has been shown in which the modulator 32 changes the frequency by rotating a mechanical optical chopper, but a shutter-type optical chopper may also be used. Furthermore, if a narrower pattern is desired, it is desirable to use an optical modulator that can handle a large frequency. Moreover, even if a continuous wave is not modulated, a modulated laser beam can be obtained by using a pulsed laser as an energy source.

〔Effect of the invention〕

According to the present invention, the pattern width can be controlled by a simple method of controlling the frequency of the modulator.
A desired pattern width can be formed using a simple device.

Furthermore, since the modulation frequency itself is controlled by electrical signals, it is simple and various programming is possible.

Furthermore, the accuracy of the formed pattern width is several μm.
It becomes possible to control up to m, and it is possible to form patterns with precision that could not be obtained from conventional laser-based etching and etching techniques.

[Brief explanation of the drawing]

Figure 1 shows the laser beam being irradiated onto the surface of a workpiece for selective plating, which is a conventional technique, and Figure 2 shows the state of the workpiece being irradiated with a modulated energy beam. 3 shows a first embodiment of the present invention showing that a pattern with an arbitrary plating width can be formed by incorporating a modulator with a control system, and FIG. 4 shows a mechanical optical chopper. Figure 5 is a diagram showing the relationship between laser irradiation density and time when the laser beam is modulated, Figure 6 is a diagram showing the modulator frequency and plating width, and Figure 7 is an actual diagram. A diagram showing a pattern,
FIG. 8 is a diagram showing a second embodiment of the present invention in which a solid sample in a gas is irradiated with an energy beam. 50...Energy beam, 51...Lens,
52... Workpiece, 53... Medium near the beam absorption region, 31... Energy source, 32... Modulator, 33... Lens system, 38... Cathode, 3
6...Plating liquid, 45...Frequency control system, 61...
...Reactive gas, 63...Substrate.

Claims (1)

[Claims] 1. In a method of selectively forming a pattern by concentrating an energy beam on an arbitrary part of a workpiece in a liquid or gas, by controlling the modulation frequency of the energy beam, A pattern forming method characterized by controlling pattern width. 2. A pattern forming method according to claim 1, characterized in that the plating medium is the liquid or gas described above. 3. The pattern forming method according to claim 1, wherein the liquid or gas is an etching medium. 4. The pattern forming method according to claim 1, wherein the energy beam is a laser beam.