DE3139168A1 - Structured chemically reducing metal deposit - Google Patents

Abstract

The process involves the deposition of additively laser-structured metal layers from chemically reducing baths on electrically nonconducting or semiconducting surfaces. The novel process does not employ a mask and makes it possible to apply, in particular, even very narrow metal tracks. In addition, the process operates with extremely high economy of material. It is characterised in that all the known metallisation baths are used at room temperature and the required working temperature is produced with the aid of a suitable laser only at the point on the substrate which is to be coated. Metal tracks are produced by moving laser and substrate relative to one another. After suitably pretreating the substrates (cleaning, degreasing, etching) they are activated in the usual way and placed in a chemically reducing metallisation bath with the side to be coated upwards. The desired structure is then irradiated or heated with the laser, and the substrate is removed from the bath, rinsed and dried. Application in electronics and allied fields.

Description

Description of the invention

Title of the invention Structured chemical reductive metal deposition Fields of application of the invention The method relates to a chemical reductive Deposition of additively structured metal layers on electrically non-conductive ones or semiconducting surfaces.

Depending on the type of metal or alloy, these structures can be used as conductor tracks or resistors in electronics, e.g. for hybrid circuits, interdigital transducer structures, conductor tracks and contact layers on ceramics, etc.

Characteristics of the known technical solutions Metallization of surfaces is a frequently used process step in the production different products In many cases it is important to have a surface for Example of an insulation material, not to be continuously metallized9 but to apply the metal layer in a certain structure. The requirements for such structuring in terms of their geometry can be quite different be.

In many cases, very coarse structuring in the mm range is sufficient; In special cases (ìXikroolektronik9, microacoustics, etc.), structuring in the pm range with exact compliance with the geometry required.

The following are often used to apply the layer of metal itself Process used: - vapor deposition - sputtering - electroless (chemical-reductive) Deposition from baths (possibly with galvanic reinforcement) - coating with Suspensions, pastes and the like, followed by baking of the layer For the structuring of the metal layers have become known processes that are Can be roughly divided into the following variants: - Direct structuring of the metal layer by means of suitable metal masks or screen stencils that already show the structure as a "breakthrough" contain.

It is easy to see that this is only a relatively simple structure applied and no increased requirements placed on the geometry of the structure can be.

Furthermore, electroless deposition is not available for this process Metal salt baths cannot be used as masks and stencils are infiltrated.

- Structuring of a closed metal layer by means of photoresist. Exposure of the varnish and subsequent dissolving processes will result in paint-free or paint-covered on the metal surface according to the desired structuring Zones created that protect the metal or the etchant in the following etching process To grant access.

There are known positive and negative methods. In some cases the photoresist is also applied first and then coated with metal.

It is also known that with light, electron beams or X-rays can be worked.

The various processes are known under the names of photo, electron beam or X-ray lithography.

What these processes have in common is that the metal layer is always closed upset and only then is structured. Is the one you want The structure is small compared to the total area when using precious metals not rational.

- After applying suitable layers to the surface, through Exposure through photo masks through chemical processes creates a "latent image of the structure created in the layer. With appropriate nucleation in the exposed areas it can be achieved that the desired metal is deposited from baths only on the "germs" and thus the structure is created. The germs can be reducing agents (for example Sn2 + OS 2.256.960) or metals (e.g. Pd AS 2.224.471).

The method described last is suitable for the currentless Deposition from baths0 It has the advantage of directly absuscaeiden the structure The disadvantage of this method is the application of a suitable layer for Creation of the latent image. The layer must be applied to the undesired places be removed again. Errors can occur in these process steps lead to a "waxing" of the surface during the subsequent metallization.

OS 2.300.481 describes the production of resistance layers by thermal decomposition of a gas mixture or a salt film, the metal carbonyls, Containing acetylazetonates or precious metal resinates, described by means of laser beams0 There are burn spot temperatures on the substrate surface depending on the application from 200 to 8000C required by these restrictions is the type of used Substrate te and thus the possibility of using the method on resistive layers and temperature-resistant substrates such as ceramic, quartz, polyamide, epoxy, limited.

In the OS mentioned above, no separation from the solution is possible.

The following conclusions can be drawn from the state of the art: - To avoid a total metallization is in many Cases the structure deposited directly.

- For the deposition of precise structures in connection with the chemical Deposition methods are the methods described in the 3rd group, where Auxiliary layers are required that have to be removed afterwards. You own the defects described. In practice, this leads to instabilities and unsuccessful attempts. by creating a closed metal layer (or a faulty structure) or cannot deposit any layer at all. Often the adhesive strength is not sufficient.

OBJECT OF THE INVENTION The aim of the invention is to reduce the Effort the reliability and the accuracy in the structuring of metal layers to increase.

Statement of the Weaving of the Invention The object of the invention is to provide a stable process for the additive structured deposition of metals from bath solutions to create, which prevents the surface from overgrowing, and thus the deposition of microstructures from the chemical-reductive baths.

According to the invention the object is achieved in that the surface a substrate in a chemical metallization bath with a laser locally is heated and thereby a structured metal layer is generated.

All materials that are suitable for a chemical-reductive metal deposition are suitable.

This includes both non-metals that have been pretreated accordingly can be activated for chemical-reductive metal deposition, such as ceramics of all kinds, glasses of all kinds, plastics of all kinds with or without foreign matter inlay, as also semiconductor materials poly- or monocrystalline in all processing stages.

As metals for structured deposition on the substrate surface all heavy metals can be used if appropriate chemically reductive baths are available and desired alloys of these metals or of one or more metals and one or more non-metals, e.g.

Nickel, cobalt, copper, silver, gold, alloys without between them or with a non-metallic fraction from the reducing agent or from those suspended in the bath Particle.

Laser beams with suitable wavelengths are applied to the substrate surface local heating in an otherwise unheated chemical plating solution generated.

This will inhibit the reaction between metal ions and reducing agent overcome and thus find. metal shedding takes place.

Any desired structures can be created by the relative movements of the substrate and the laser are generated on the substrate surface.

It plays a role in the accuracy of the structures and the deposition rate the thickness of the liquid film over the substrate surface plays an important role.

As a minimum, this layer thickness must be equal to the layer thickness of the liquid film on the surface of the fat-free substrate after immersion in the plating bath and take it out again.

The maximum is limited by the increasing thickness of the liquid layer increasing absorption of the beam in the solution.

Thin layers can be created by adding the liquid flows over a sloping substrate.

It is also possible that the deposition of the metal from a on the surface of the substrate there is a dried-up salt film from the metallization solution he follows.

The layer thickness of the deposited metal depends on the duration of the Laser irradiation dependent.

However, it is possible to use substrates with low layer thicknesses in one suitable customary chemical-reductive metallization bath to the desired Reinforce layer thickness.

The invention is explained further with the aid of two exemplary embodiments.

Embodiment 1 A special ceramic, z.3. A1203 (or capacitor ceramic, other special ceramics, silicon and other semiconductor materials of all processing stages, Glasses, plastic materials with or without reinforcement, etc.) is degreased e.g. in 3% Gr-Amulgo, then rinsed and z.3. with palladium chloride and sodium hypophosphite activated.

The substrate pretreated in this way is converted into, for example, a chemically reductive Nickel plating solution (for example according to DD patent 134 653) with the side to be treated inserted upwards. The solution covers the surface to be coated with a specified one Layer thickness, which among other things depends on the power of the laser (mainly between 0.05 and lo mm). The substrate is then applied using an IR laser of suitable power, for example irradiated by the solution. Separates at the point heated by the irradiation In the example, nickel is deposited (more precisely Ni = Py).

xy The structure widths can be between 50 and 2000 / µm.

Embodiment 2 For a hybrid circuit in the GHz range the contact layer structures are to be deposited chemically-reductively additively.

A degreased and etched with a chromic acid or hydrofluoric acid mixture it is alumina substrate with a standard quality in a suitable metal ion solution, e.g., palladium ions, dipped; the metal ions with one known in chemical Deposition technology reducing agents to catalyze the chemical deposition process Germs reduced.

For structured metal deposition, e.g. a Cu layer or NiP layer, a stable chemical bath (e.g. according to DD patent 134 653) is required.

The metallization solution with a working temperature of> 700C covers the nucleated aluminum oxide substrates in a defined manner at room temperature equal distance from the surface (e.g.

5 mm An IR laser is programmed according to the desired structures in t-y coordinates with a speed of e.g. 3 mm-sec 1 over the substrate surface guided.

Due to the energy supplied, the deposition process continues on the irradiated Hiring.

The structures obtained are then stable in a second chemical plating bath reinforced on GPIM.

The structures consist of 1 - 2 mm wide conductor tracks and contact islands of 100 x 100 µm.

The geometric accuracy depends on the substrate, the technological Parameters and the required layer thickness and is + in the examined case 10 µm.

The NixPy layers have an adhesive strength of> 800 N cm 2 zy and a specific electrical conductivity of (0.15 - 1.4) 1O (flcin) 1.

Claims (9)

Invention claim ¼ Structured chemical-reductive metal deposition with substrate, metallization bath and laser, characterized in that a through Degreasing and activating pretreated substrate in a chemical plating bath is inserted with the side to be treated facing the laser, from the metallization bath is covered, localized heating on the surface is covered by the laser irradiation of the substrate it takes place in the otherwise unheated metallization bath and through Relative movement of substrate and laser any structures can be generated. 2. The method according to item 1, characterized in that the localized Heating is done by an IR laser. 3. The method according to items 1 and 2, characterized in that if present appropriate chemical-reductive baths all heavy metals and desired alloys of these metals or of one or more metals and one or more Non-metals are deposited. 4e method according to item 1 - 3, characterized in that the deposition takes place on non-metallic surfaces and / or semiconductor materials. 5 The method according to items 1 and 4, characterized in that preferred used heavy metals nickel, cobalt, copper, silver, gold, alloys between them with or without a non-metallic content from the reducing agent or from im Bath suspended particles are. 6. The method according to items 1 and 5, characterized in that the deposition preferably on ceramics of all kinds, glasses of all kinds, semiconductor material poly- or monocrystalline in all processing stages, plastics of all kinds with or without foreign matter he follows. 7. The method according to item 1 - 5, characterized in that the layer thickness the solution through which the laser beam must penetrate, at least equal to the layer thickness of the liquid film on the surface of the fat-free substrate after immersion is in the plating bath and removal and is limited to the maximum due to the absorption of the jet, which increases with increasing liquid layer thickness in the solution. 8. The method according to item 1 and 7, characterized in that the thin Layer thicknesses are preferably realized in that the liquid over the sloping substrate flows. 9. The method according to item 1-5, characterized in that the deposition of the metal from a salt film dried on the surface of the substrate takes place from the metallization solution.