GB2207395A

GB2207395A - Producing a pattern in a material

Info

Publication number: GB2207395A
Application number: GB08718006A
Authority: GB
Inventors: Charles Richard Jarvis; Stephen Geoffrey Tyler
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1987-07-29
Filing date: 1987-07-29
Publication date: 1989-02-01
Anticipated expiration: 2007-07-29
Also published as: GB2207395B; GB8718006D0

Abstract

A pattern in a material, for example a pattern of conductive tracks, is produced by laying down a layer of first material (3) adjacent to a layer of second material (2). Energy is applied to a selected region or regions to cause diffusion between the first and second materials to produce a third material (5) which is a mixture of the two. Then one of the first and third materials is selectively etched to produce the pattern. <IMAGE>

Description

Method for Producing a Pattern in a Material This invention relates to a method for producing a pattern in a material.

In many applications it is. often desirable to form a pattern in a material with extremely high accuracy; such as for example, a pattern of conductive tracks on an insulating substrate. However, it is difficult to achieve the accuracies required using conventional methods.

The present invention seeks to provide an improved method for producing a pattern in a material.

According to this invention, a method for producing a pattern in a material includes the steps of: arranging a layer of first material on a layer of second material different to the first; applying energy to a selected region of the first material to cause diffusion between the first and second materials, such that a third material comprising a mixture of the first and second materials is produced at the region; and applying a process which selectively attacks one of the first and third materials.

The energy may be applied in a highly selective way, enabling well defined lines and areas of pattern to be produced, such that greater accuracy may be achieved with fewer manufacturing stages than is generally possible using conventional techniques which usually involve photolithographic processes. Preferably the process is etching. This may be wet etching, or dry etching involving ion beam milling, for example. The etchant may be chosen, for example, to etch the third material and the second material but not the first. In this case, both the third material and the underlying second material may be etched, but not that part of the second material protected by the first.The layers of first and second materials may be laid down in any order, although obviously, where they are laid down on a substrate, it is more convenient if the layer of first material to which energy is to be applied is laid down after the layer of second material.

However, it may be possible to apply the energy to the first material via the second material. The amount of applied energy required is dependent on the types of materials used and the thicknesses of the layers. It is necessary that sufficient diffusion occurs between the first and second materials to produce a third material which has a different characteristic from the first material to enable them to be distinguished so that selective processing be carried out. Generally, it will be necessary to ensure that diffusion occurs throughout the first material such that atoms of the second material are present at the surface of the first material. The amount of energy required to obtain the required degree of diffusion may be readily determined by one skilled in the art by a series of routine experiments.

Preferably, the layer of the first material is substantially thinner than the layer of the second material. In this context substantially should be taken to mean sufficiently thin to enable etchant to selectively act on only one of the first and third materials. The thinner the layer of first materials is made, the less energy is required to produce complete diffusion through it of atoms of the second material.

Advantageously the applied energy is in the form of a laser beam or a high energy particle beam, such as an electron beam. Such beams may be focussed to a very small size and may be accurately controlled to produce a high definition pattern.

It is preferred that the layer of first material has a free surface to which the energy is directly applied. By "directly" is meant that it is not applied via an intervening layer, for example the layer of second material or an additional layer deposited on the first material. However, it may be possible to apply energy through such an additional layer.

According to a feature of this invention, apparatus is arranged to carry out a method in accordance with the invention to produce a device which includes a desired pattern of conductive tracks. According to another feature of the invention, a device is manufactured by a method in accordance with the invention, the device comprising an insulating substrate bearing conductive tracks.

One way in which the invention may be performed is now described by way of example with reference to the accompanying drawings, in which Figures 1, 2, 3 and 4 illustrate successive steps in a method in accordance with the invention.

In a process in accordance with the invention for producing a pattern of conductive copper tracks on an insulating substrate, a 35 micron layer 1 of copper is laid down on an insulating substrate 2 as shown in Figure 1. The entire surface of the copper layer 1 is then plated with gold to give a layer 3 of about 0.3 microns thickness over the copper layer 2, as shown in Figure 2.

A laser beam 4 is focussed on to the gold layer 3 and guided over its surface in a predetermined path. The laser beam has a power level of a few milliwatts and is driven at a speed over the surface which enables copper atoms from the layer 2 to diffuse to the open surface of the gold layer 3. This is illustrated in Figure 3 of the accompanying drawings. The gold-copper alloy produced in the regions where the laser beam has been applied forms a pattern 5 over the surface. Etchant is then applied, being in this case ferric chloride. The ferric chloride etches the alloy layer 5 and the underlying copper. The thin gold layer 3 is sufficient to prevent etching in those areas which it covers. Thus a pattern of conductive tracks 6 may be accurately produced over the surface of the substrate 2, as shown in Figure 4.

Of course, other forms of energy beam may be employed, such as an electrom beam, and the alloy 5 and top layer 3 may be selectively processed using other techniques

Claims

CLAIMS 1. A method for producing a pattern in a material including the steps of: arranging a layer of first material on a layer of second material different to the first; applying energy to a selected region of the first material to cause diffusion between the first and second materials, such that a third material comprising a mixture of the first and second materials is produced at the region; and applying a process which selectively attacks one of the first and third materials.
2. A method as claimed in claim 1 wherein the process is etching.
3. A method as claimed in claim 2 wherein the etchant etches the second material such that the second material underlying the said one is etched.
4. A method as claimed in claim 1, 2 or 3 wherein the first material is a metal.
5. A method as claimed in claim 1, 2, 3 or 4 wherein the second material is a metal.
6. A method as claimed in any preceding claim wherein the layer of the first material is substantially thinner than the layer of second material.
7. A method as claimed in any preceding claim and wherein the applied energy is a laser beam.
8. A method as claimed in any of chimps 1 to 6 wherein the applied energy is a high energy particle beam.
9. A method as claimed in any preceding claim wherein the layer of first material has a free surface to which the energy is directly applied.
10. A method as claimed in any preceding claim and including an insulating substrate on which the second layer is laid down.
11. Apparatus arranged to carry out a method as claimed in any preceding claim to produce a device which includes a desired pattern of conductive tracks.
12. A device manufactured in accordance with a method as claimed in any of claims 1 to 10, the device comprising an insulating substrate bearing conductive tracks.
13. A method substantially as illustrated in and described with reference to the accompanying drawings.
14. A device manufactured in accordance with a method substantially as illustrated in and described with reference to the accompanying drawings.