CA2048669A1

CA2048669A1 - Coating process

Info

Publication number: CA2048669A1
Application number: CA 2048669
Authority: CA
Inventors: Hilmar Esrom
Original assignee: Individual
Current assignee: ASEA BROWN BOVERI AG
Priority date: 1989-12-22
Filing date: 1990-12-20
Publication date: 1991-06-23
Also published as: DE3942472A1; WO1991009984A1; JPH04505481A

Abstract

Abstract Coating Process The invention relates to a process for coating a substrate surface (1A). To this end, the surface (lA) of the substrate (1) is irradiated with UV radiation having a defined wavelength. The substrate (1) used comprises a chemical compound that has at least one readily oxidizable or readily sublimatable component.
Irradiating all or part of the substrate surface (lA) liberates the readily oxidizable or readily sublimating component of the chemical compound, so that the irradiated regions (lB) of the surface (lA) are formed by the remaining components of the chemical compound. These regions can then be reinforced with a reinforcing layer (4) using conventional coating processes.

Significant figure: Fig. 2

Description

-`' 20~69 PCT/EP 90/02270, December 20, 1990 COATING PROCESS

The invention relates to a process for coating substrates as ~enerically defined by the preamble to claim 1.
Such processes are used wherever the surface of a substrate is to be metallized partially or completely, or provided with an alloy or a dielectric layer.
The object of the invention is to disclose a process with which metallizing and/or the application of a layer to a substrate can be performed in a simple manner.
According to the invention, this object is attained by the characteristics of claim 1.
With the process according to the invention it is possible in a simple manner to partially or completely metallize the surface of the substrate, which is manufactured from aluminum nitrite, for example. By irradiating the substrate surface with UV radiation of a defined wavelen~th and pulse rate, the nitrogen in the irradiated region of the substrate surface can be liberated. The surface of the substrate in the irradiated regions, once the irradiation has ended, will be formed of pure aluminum. In currentless wet-chemical metall1zing baths, an alloy, a dielectric or a metal in the form of copper, nickel, gold, and so forth can then be applied to these regions.

Furthermore, all the surface reglons that are formed by~pure :, ~ , ' - :
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aluminum after the irradiation can be reinforced by other processes, for instance by a conventional thermal chemical vapor deposition or electrolytic metallizing process. As a result of irradiating a substrate of silicon nitride the possibility also exists of liberating the nitrogen in the irradiated regions, so that the irradiated surface regions of the substrate are formed by pure silicon. The possibility also exists of irradiating ceramic substrates, prepared from chemical compounds that have at least one component that sublimates readily. The readily sublimating component is liberated by the irradiation, and the irradiated surface regions of the substrate are then formed by the components of the chemical compound that remain behind.
The invention will be described below in further detail in terms of examples. Shown are:
Fig. 1, the treatment of a substrate surface by the process according to the invention;
Fig. 2, an irradiated substrate:
Fig. 3, a coating substrate; and Fig. 4, a substrate provided with bondiny.
Fig. 1 shows a generally flat substrate 1, which in the exemplary embodiment shown here is manufactured of aluminum nitride (AlN). To form regions on the surface lA of the substrate 1 that are formed by a pure metal, the æubstrate 1 is irradiated with UV radiation. A high-power W emitter 2, in the form of an excimer laser or an excimer emitter is therefore .
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disposed a defined distance above the substrate surface lA. A
detailed description of a high-powered emitter 2 of this kind can be found in European Patent Application 0 ~54 110. The high-power emitter 2, hereinafter called an excimer emitter for short, comprises a discharge chamber (not shown here) that is filled with a noble gas or gas mixture and is defined by metal electrodes (not shown here) cooled on one side and by a dielectric (also not shown here). The dielectric and the second electrode located on the surface of the dielectric remote from the discharge chamber are transparent to the radiation generated by corona electrical discharge. By means of this construction and a suitable selection of the filling gas, a high-power W
emitter of high efficiency with a large surface area is created.
The high-power emitter 2 operates in a quasi-pulsed mode. In the exemplary embodiment shown here, it is ~illed with krypton fluoride and can therefore produce UV radiation in the range from 240 to 270 nm. To produce UV radiation having a wavelength between 60 and 165 nm, a noble gas filling of helium or argon is used. With a xenon gas filling, a wavelength between 160 and 190 ~0 nm can be generated. With an argon fluoride gas filling, the wavelength is from 180 to 200 nm, while w1th a gas mixture of xenon and chlorine, a UV wavelength of from 300 to 320 nm can be attained. The excimer laser has a pulse rate of from 100 to 200 Hz, and the pulse energy is 100 to 200 mJ. With the gas mixtures Ar/F, Kr/F, XeCl, and Xe/F, the corresponding wavelengths 193 nm, :

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248 nm, 308 nm and 351 nm can be generated. If the entire surface of the substrate l is not to be irradiated, then a mask 3 is disposed between the surface lA and the excimer laser 2. This mask has openings 3D. The openings 3D are disposed precisely where irradiation of the substrate surface 1 is desired. By irradiating the substrate surface 1, the nitrogen in the AlN
compound is liberated. As a result, after the irradiation has ended, the irradiated regions lB are formed by pure aluminum.
The non-irradiated regions lN of the substrate surface lA
continue to be formed of aluminum nitride. If the entire surface of the substrate is to have an aluminum coating, then the irradiation can be performed without the mask 3. The surface regions lB, now formed by aluminum and shown in Fig. 2, can be used as catalysts, for instance, if the substrate 1 is further treated in currentless metallizing baths, so that a layer~of copper, nickel, gold or zinc, for instance, can be applied to these regions lB in a thickness of up to 30 ~m. A substrate 1 provided with such layers 4 is shown in Fig. 3. As can be seen from Fig. 3, the regions lN that comprise aluminum nitride remain ~-~
~0 free of any coating. According to the invention, the possibility also exists of reinforcinq or coating the regions lB by other processes. For instance, electrolytic metaIlizing can also be employed for coating or reinforcing. A current can also be passed continuously or in pulsed fashion through the regions lB.
In a CVD (chemical vapor deposltion) reactor, a thermal CVD

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- ' 2 ~ 6 ~ -process can also be performed locally in this way. The regions lB comprising aluminum can be oxidized or nitrified locally as well. By suitable disposition of a mask 3 between the substrate surface lA and the excimer laser 2, the regions lB can be embodied as conductor tracks for a circuit, by purposefully irradiating the surface lA. By means of the local oxidation or nitriding of certain regions of these conductors tracks, these tracks can be provided with interruptions for carrying electrical signals at desired points. With the aid of the excimer laser 2, the aluminum nitride substrate 1 can also be drilled through.
With the aid of focusing optical elements in the form of lenses and an XY displacing device, aluminum tracks can also be inscribed, in the course of which the AlN substrate is moved relative to the focusing beam of UV light. With the aid of a focusing optical element (not shown here), the beam arriving from the excimer laser can be bunched in such a way that the bore 5, shown in Fig. 4, can be formed with the particular desired diameter. As already mentioned, the suhstrate 1 is fabricated completely of aluminum nitride. During the formation of the bore 5, the nitrogen present in the wall defining the bore 5 is liberated, so that the defining wall, after the bore 5 has been finished, is formed exclusively of aluminum~ If the bore 5 is in direct electrically conductive contact with the region lB on the surface lA on the substrate 1, then this region 1~ is connected electrically conductively, via the wall of the bore 5, with the ",~ ' 2 (~ 9 layer 10 that is immediately adjacent the underside of the substrate 1.
The process according to the invention can be employed not only on substrates of aluminum nitride; there is also the possibility of irradiating substrates of silicon nitride (Si3N4) with the excimer laser. With this substrate as well, the nitrogen in the irradiated surface regions (not shown hexe) is again liberated. The possibility also exists of irradiating ceramic substrates that are formed of a chemical compound that has a readily sublimating component. The readily sublimating component is liberated by the irradiation. The irradiation surface regions of the substrate are then formed by the remaining components of the chemical compound. Since both the aluminum layers and the layers formed in the case of other substrates form an atomic bond with the layers located beneath them, a very high adhesion strength is effected thereby.

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Claims

CLAIMS:

1. A process for forming layers on a substrate, characterized in that a substrate or a layer (1) comprising a chemical composition that has at least one compound which can be readily oxidized, nitrided or sublimated is irradiated partially or over the entire surface area to eliminate this component, such that the irradiated regions (1B) of the surface (1A) of the substrate (1) is now formed only by the remaining components of the chemical compound.

2. The process of claim 1, characterized in that the substrate or layer (1), which is produced by sputtering, vapor deposition or CVD processes, is irradiated with UV radiation having a wavelength between 60 and 370 nm.

3. The process of claim 1, characterized in that the substrate or layer (1) is irradiated with a high-power emitter (2) described in European Patent Application 0 254 111 or with an excimer laser, which has a pulse rate of 100 to 200 Hz and a pulse energy of 100 to 200 mJ.

4. The process of one of claims 1 to 3, characterized in that a substrate (1) of aluminum nitride (AlN) is irradiated with a high-power emitter (2) that has a gas filling of krypton fluoride and emits a UV radiation in the range from 240 to 270 nm.

5. The process of one of claims 1 to 4, characterized in that a substrate or layer (1) of a ceramic material is irradiated by a high-power emitter (2) that emits UV radiation in the wavelength range between 60 nm and 320 nm.

6. The process of one of claims 1 to 4, characterized in that the surface regions (IB), comprising aluminum, of the substrate (1) fabricated from aluminum nitride are reinforced in a currentless metal bath, by means of CVD processes or electrolytic metallization, with a layer of copper, nickel, gold, or zinc having a thickness of up to 30 nm.