GB2155042A - Laser induced ion beam generator - Google Patents

Abstract

The generator, which selects, accelerates and focusses ions onto substrates to be coated either completely or in tracks such that said neutralised ions are firmly bonded to said substrate, comprises laser source 1, annular laser beam reflector 3, annular lens 5 which focusses the beam onto rotating cathode 7, an ion selection electrode 9, ion accelerator 11 and ion beam focussing system 12 which produces an output beam 13 which impinges on substrate 14 positioned on a table 16 controlled by computer 17 which also controls operation of laser 1. The invention has application in the electronics industry for the manufacture of circuit boards, in the optical industry to coat precision optical components and in the manufacturing industry to make composite materials. <IMAGE>

Description

SPECIFICATION Laser substrate coater and track layer This invention relates to a method of an apparatus for forming layers or coatings on a substrate and more particularly, to a system for producing a beam of ions and directing them at sufficient energy onto a non-conducting substrate so that they enter the body of said substrate adhering strongly to its structure in such a manner that the flow of such ions can be used to build up a layer on the surface of said substrate which may be metallic or non metallic depending on the nature of the ions used, consisting of a laser activated ion source, ion beam manipulating optics, ion beam accelerator an ion beam focussing system and a computer controlled table for passing the substrates to be coated under the ion beam.

The invention has application in the production of circuit boards in the electronics industry and in the manufacture of composite materials where individual layers of said composite material are deposited in turn on top of each other.

Prior art systems for depositing metallic and non-metallic layers on various substrate are based on chemical, electro-chemical and thermal depositing techniques and have suffered both from the poor bonding of said layers together and the toxic nature of the processes involved. In the case of circuit board manufacture, prior art systems coat the whole of the substrate with copper metal which is then acid etched to remove most of said copper leaving behind the reqhuired circuit pattern.

In my invention, the laser induced ion beam generator products the output ion beam at sufficient intensity to deposit a rigidly bonded line of metallic or non-metallic elements, or compounds of said elements, which can either form a predetermined circuit pattern via a sequence of off-set lines along the surface of said sub-strate so that the whole of said surface is uniformly coated. Alternatively, by using a laser exciter with a line output in the laser induced ion source it is possible to deposit a line of ions at a time on said substrate so that its surface can also be fully covered by the forward motion of said substrate relative to the ion line output.The invention can lay an initial track of thin metallic or non-metallic layers on said substrates to ensure ridgid adherence then follow this up with lower energy, much higher intensity ion beams to build up the thickness of said layers as required. It should also be pointed out that once the critical bonding layer has been ridgidly attached to the substrate to very small thicknesses, it is possible to complete the process to much larger thickness by conventional chemical means, thus utilising the invention as a high speed, thin layer depositer of the highest quality. The thin and thick track laying sequences can either be laid down independently of each other or with a slight delay between the initial and final track deposits.Tracks on both sides of said substrates may be laid down at the same time but bearing in mind that if the track patterns on on the top and bottom surfaces differ from each other then the table or mount holding the substrate has to execute two different movements. Experiments carried out by the inventor showed that ion species that can be produced by focussing intense laser beams onto various targets are emitted in three groups, namely fast ions with energies well into the MeV range (million electron volts), hot ions with much less energy but in the tens to hundreds of thousands of electron volts, and the low energy, and most intense ion group with lesser energy still, some of which are well below 1 OKeV (ten thousand electron volts).

Also, the charge on the laser induced ions depends on the power density of the laser beam incident on the target. At the threshold of 1014 watts per cm2 observed for the generation of fast ions using a neodimium doped glass laser system operating at a wave length of 1.06 microns (1.06 X 10-4 cms), the ionisation stages of gold atoms, for example, could be increased well above ten charge states. Such multiply charged ions are relatively easy to accelerate. For example, a 10 + charged ion accelerated through a 1 MeV (one million volt) potential gradient would emerge with an enegrgy of 10MeV whereas a singly charged ion would emerge with an energy of 1MeV.

The ions allowed to emergy from the output aperture of the invention can be controlled by electrodes positioned within the system between the target and the ion accelerator both to block the passage of the ions and to deflect unwanted speceies out of the acceleration path. n this way fast ions for ridgidly bonding the track onto the substrate, followed by the solwer, lower energy ions to build up the track thickness. Since the lower energy ions can be generated at currents of many tens of amps with current techniques plenty of thermal ions can be generated to accomplish the tasks in hand as far as building up on the base tracks are concerned.

Since the laser irradiation of targets can produce both metallic and non-metallic ions singly or in groups, it is possible to lay down tracks which are electrically conducting and nonconducting and opaque and transparent to light.

The width of the tracks deposited on said substrates can be varied by adjusting the ion focussing system of the invention. The invention also allows for the depositing of conducting, both electrical and optical, layers within pre-drilled holes in the insulating card so electrical and optical conduction can take place between the circuits deposited on both sides of the substrate.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows the layout of the laser induced ion source/track laying system; Figure 2 shows a sample copper track deposited by the method of the invention on a substrate; Figure 3 shows an arrangement of apparatus for the depositing of tracks on both sides of a substrate simultaneously; and Figure 4 shows appropriately focussed ion beams used to coat the surface of pre-drilled holes with either electrically or optically conducting layers.

In Fig. 1, numeral 1 indicates the laser source whose output beam indicated by numeral 2 is reflected off an annular laser beam reflector indicated by numeral 3 through an annular lens indicatged by numeral 5 which focusses the beam as indicated by numeral 6 onto the rotating cathode indicated by numberal 7 which results in the laser induced, high density plasma indicated by numeral 8.By selecting the voltage on the particle selection electrode indicated by numeral 9, ions are emitted along a path indicated by numeral 10 through the hole in reflector 3 into ion accelerator indicated by numeral 11 then, after acceleration into ion beam focussing system indicated by numeral 12 with the focussed output beam indicated by numeral 13 impinging on the track indicated by numeral 14 on the substrate indicated by numeral 15 which is positioned on a table indicated by numeral 16 which is controlled by a computer indicated by numeral 17 which also controls the operation of laser 1 and all other changeable components in the system via leads (not shown).

In Fig. 2a sample track indicated by numeral 18 has been deposited and bonded to substrate 15. In Fig. 3 two laser induced ion beam generators indicated by numeral 19 focus the said ions into track 14 on the top and bottom of substrate 15 held in table 16, the whole operation being controlled via computer 17 which stores details of the circuits to be deposited on the substrate 15. In Fig. 4 numeral 20 indicates the defocussed ion beams 13 coating a hole pre-drilled in substrate 15, thus allowing conduction to occur between the top and bottom circuits on substrate 15.

The invention can be used to deposit layers of reflective coatings on optically polished surfaces as well as antireflective coatings thus producing laser mirrors and low scatter/reflective optics respectively.

The invention produces circuit boards working on electrical pulses along the tracks if said tracks are made of a metal such as copper. on the other hand if the tracks are made of nonmetallic but optically transparent materials such as silicon or glass or dielectric layers, laser pulses can be transmitted along said circuits at a velocity considerably in excess of that achievable with electrical pulses. The invention can be used to manufacture layered structures of material which do not otherwise bond to each other whether they be metallic, non-metallic or both.

The invention has application for the manufacture of circuit boards in the electronics and electro-optic industries, the coating of optical components and the manufacture of laser mirrors in the optical industries. Furthermore, the invention has application in the manufacture of composite materials where each layer is firmly bonded to its neighbour. It should be pointed out that to neutralise the ions either stray electrons or laser produced electorns in the invention can be used.

Claims (12)

1. A system for the generation and selection of laser induced ions their acceleration and focussing onto the surface of a substrate such that said ions are of sufficient energy to penetrate into the body of said substrate allowing for a firmly bonded track of said ions to build up on said substrate when it is moved relative to said ion beam, said ions being neutralised by environmental electrons to form atoms of metals in said tracks and the form of said tracks being as electronic circuits stored in the control computer.

2. A system as claimed in claim 1 where one ion beam generator is places either side of said substrate so that circuits can be formed on both sides of said substrate simultaneously.

3. A system as described in claim 2 where the ion beam outputs are defocussed to allow for the metalic coating of the inside surfaces of holes pre-drilled in said substrate allowing for the connection of said circuits on the top and bottom surfaces of said substrates.

4. A system as claimed in claim 1 where the ions forming the output beam are nonmetallic forming atomic layers of optically conducting tracks on said substrate.

5. A system as claimed in claims 1 and 4 where the substrates to be coated are precision optical components.

6. A system as claimed in claim 5 where the substrate is that of a laser mirror.

7. A system as claimed in claim 5 where the substrate is a lens which has to be antireflection coated.

8. A system as claimed in claim 1 where the substrate is being built up of deposited layers of atomised ions forming a composite structure.

9. A system as described in claim 4 where a mixture of ions are used to form compound on said substrate.

10. A method of forming layers or coatings on substrates, substantially as hereinbefore described with reference to the accompanying drawings.

11. Apparatus for forming layers or coatings on substrates, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. A substrate having a coating or layer formed in accordance with any one of the preceding claims.