DD157989A3 - METHOD OF STRUCTURED CHEMICAL REDUCTIVE METAL SEPARATION - Google Patents

Abstract

The method relates to a chemical-reductive deposition of additively structured metal layers with the aid of laser beams on electrically non-conductive or semiconductive surfaces. The inventive method works without a mask and allows the application especially of very narrow metal sheets. In addition, the process works with maximum material economy. It is characterized in that all known Metallisierungsbaeder find use at room temperature and the required working temperature is generated by means of a suitable laser only at the location of the substrate to be coated. By relative movement of laser and substrate metal tracks are generated. After appropriate pretreatment of the substrates (cleaning, degreasing, etching) they are activated as usual and placed with the side to be coated up in a chemically reductive metallization. The desired structure is then irradiated or heated with the laser, the substrate removed from the bath, rinsed and dried. Applications in electronics and related fields.

Description

22 UU A 8

Title of the invention.

Process for structured chemical-reductive metal deposition

Field of application of the invention

The method relates to a chemical-reductive deposition of additively structured metal layers on electrically nonconducting or semiconducting surfaces. * Depending on the nature of the metal or alloy, these structures may be used as traces or resistors in electronics, e.g. for hybrid circuits, interdigital transducer structures, printed conductors and contact layers on ceramics and the like

Characteristic of the known technical solutions

The metallization of surfaces is a frequently used process step in the production of different products.

In many cases, it is important to have a surface, e.g. from a Isolationsmaterdal not continuously metallize, but to apply the metal layer in a specific structure. The requirements for such structuring in terms of their geometry can be quite different.

-7 illH -10 QO * i \\ b Γ-: i -j

-2- 2244

In many cases, very coarse structuring in the mm range is sufficient, in special cases (microelectronics, microacoustics, etc.) structuring in the um range with exact adherence to the geometry is required. For applying the metal layer itself, the following methods are often used:

- steaming '

- sputtering

- Electroless (chemical-reductive) separation from baths (possibly with galvanic reinforcement)

- Coating with suspensions, pastes and the like and then baking the layer

For the structuring of the metal layers methods have become known, which can be roughly divided into the following variants:

Direct structuring of the metal layer by means of suitable metal masks or screen templates, which already contain the structure as a "breakthrough".

It is easy to see that this applied only relatively simple structures and no increased demands on the geometry of the structure can be made. '

Furthermore, electroless plating from metal salt baths is not applicable to this process because masks and templates are infiltrated.

- Structuring of a closed metal layer by means of photoresist. By an exposure of the paint and subsequent dissolution processes paint-free or paint-covered zones are created on the metal surface according to the desired structuring, in the following

-3- 22ΛΛΛ8

To protect the etching process of the metal or to grant the etchant access ·

Positive and latent methods are known. In some cases the photoresist is also applied first and then coated with metal.

Furthermore, it is known that it is possible to work with light, electron beams or X-rays. The various methods have become known under the names of photographic, electron beam or X-ray lithography.

The common feature of these methods is that the metal layer is always applied closed and then structured. If the desired structure is small compared to the total area, this is not rational when using noble metals.

After applying suitable layers to the surface, a "latent" image of the structure in the layer is created by exposure via photomasks by chemical processes. · With appropriate nucleation at the exposed areas, it can be achieved that only at the "germs" of baths the desired metal The nuclei can be reducing agents (for example Sn ²⁺ OS 2,256,960) or metals (for example Pd AS 2 · 224 · 471).

The method last described is suitable for electroless deposition from baths. It has the advantage of depositing the structure directly. The disadvantage of this method is the application of a suitable latent image forming layer. The layer must be removed at the undesirable spots.

22 Λ A A B

In these process steps, errors can occur which lead to a "growth" of the surface in the subsequent metallization.

From the state of the art, the following conclusions can be drawn:

To avoid a total metallization, the structure is deposited in many cases directly. For the deposition of precise structures in connection with the chemical Abseheidungsverfahren are the methods described in the 3 · Group, wherein auxiliary layers are required, which must be subsequently removed. You own the described defect. In practice, this leads to instabilities and failures in that a closed metal layer (or faulty structure) or no layer at all can deposit. Often the adhesive strength is insufficient.

Object of the invention

The aim of the invention is to increase the reliability and the accuracy in the structuring of metal layers in the reduction of the effort.

Explanation of the essence of the invention

The object of the invention is to provide a stable process for the additive structured deposition of metals from bath solutions, which prevents growth of the surface and thus enables the deposition of microstructures from the chemically reductive baths.

2 2 Λ 4 A 8

According to the invention the object is achieved in that the surface of a substrate is heated locally in a chemical metallization with a laser and thereby a structured metal layer is produced. As substrates, all materials can be used which are suitable for a chemical-reductive Metailabscheidung. These include both non-metals, which can be activated by appropriate pretreatment for the chemical-reductive metal deposition, such as Keram · Β · ceramics of all kinds, glasses of all kinds, plastics of all kinds without or with foreign material, as well as semiconductor materials poly- or monocrystalline in all processing stages ·

As metals for structured deposition on the substrate surface, in the presence of appropriate chemically reductive baths, all heavy metals and desired alloys can be deposited from this metal or from one or more metals and one or more non-metals.

Nickel, cobalt, copper, silver, gold, alloys between them with no or non-metallic portion of the reducing agent or suspended in the bath particles.

By means of laser beams of a suitable wavelength, local heating in an otherwise unheated chemical metallization solution is produced on the substrate surface. As a result, the reaction inhibition between metal ions and reducing agent is overcome and thus takes place a metal deposition.

As a result of relative movements of substrate and laser, any structures can be produced on the substrate surface. For the accuracy of the structures and the deposition rate, the thickness of the liquid film over the substrate surface plays a major role.

-6 - '2244 4

At a minimum, this layer thickness must be equal to the layer thickness of the liquid film on the surface of the fat-free subatratea after immersion in the metallizing bath and removal.

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

The layer thickness of the deposited metal is dependent on the duration of the Laaerbestrahlung. However, it is possible to reinforce substrates with small layer thicknesses in a suitable conventional chemical-reductive metallization bath to the desired layer thickness.

Thin layers can be created by flowing the liquid over an inclined substrate. Furthermore, it is possible for the deposition of the metal from a salt film dried on the surface of the substrate to take place from the metallization solution.

The invention will be further explained with reference to two exemplary embodiments.

Embodiment 1

A special ceramic, eg Al ₂ O ₃ (or capacitor ceramic, other special ceramics, silicon and other semiconductor materials of all processing stages, glasses, plastic materials with or without reinforcement) is degreased eg in 3% G _r -Amulgo, then rinsed and ζ.Β. Activated with palladium chloride and sodium hypophosphite. "Daa pretreated in this way is placed in an, for example, ohemisch-reductive nickel plating solution (for example, according to GDR patent 136,653) with the side to be treated upwards,

-7- 2244 Λ 8

inserted. The solution covers the surface to be coated with a specified layer thickness, the u * a. depends on the power of the laser (mainly between 0.05 and 10 mm). This is indicated e.g. with an IR laser of suitable power, the substrate is irradiated by the solution. At the point heated up by the irradiation, nickel is formed in the example case (more precisely Hi PJt 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 additively in a chemical-reductive manner.

A defatted standard grade alumina substrate etched with a chromic acid or hydrofluoric acid mixture is transformed into a suitable metal ion solution, e.g. Immersed in palladium ions, which reduces metal ions by a reducing agent which catalyzes the chemical process of separation in a chemical known deposition technology.

For structured metal deposition, e.g. a Cu layer or NiP layer, a stable chemical bath (e.g., according to GDR Patent 134,653) is needed.

The metallization solution with a working temperature of> 70 ⁰ C covers. At room temperature, the germinated Aluminiumoxidsubstrate at a defined equal distance from the surface (eg 5 mm).

An IR laser is programmed according to the desired structures in x-y coordinates at a speed of e.g. 3 mm see "" over the substrate surface. Due to the supplied energy, the deposition process begins at the irradiated points.

- β -

Subsequently, the resulting structures are amplified to 6 μm in a second stable chemical metallization bath.

The structures consist of 1-2 mm wide tracks and contact pads of 100 χ TOO jum.

The geometric accuracy depends on the substrate, the technological parameters and the required layer thickness and is +10 pm in the case studied.

The Ni "P layers have an adhesive strength of

y -2

> 800 F cm and a specific electrical conductivity of (0.15 - 1.4) 10 ⁴ (Qcm) " ¹ .

Claims (2)

~ 9- 22ΛΛΛ8 claim for invention. " A process for the structured chemical-reductive life-time labeling on substrates, characterized in that the substrate pretreated in a known manner is locally heated by laser beams within a non-heated chemical metallization solution at the desired deposition sites. 2 · Method according to item 1, characterized in that for structuring substrate and laser are moved relative to each other.