WO2008152675A2

WO2008152675A2 - Method for depositing ag on glass supports or the like

Info

Publication number: WO2008152675A2
Application number: PCT/IT2008/000398
Authority: WO
Inventors: Ivan Fiorini; Rodolfo Candelo
Original assignee: NANTECH Srl
Current assignee: NANTECH Srl
Priority date: 2007-06-15
Filing date: 2008-06-13
Publication date: 2008-12-18
Anticipated expiration: 2009-12-15
Also published as: WO2008152675A3; ITGE20070054A1

Abstract

Method for depositing Ag on glass supports by magnetron sputtering, such method comprising the steps of: placing a glass support to be metallized as well as Ag targets in a low pressure chamber; treating the substrate with an O2 flow for a given time period while applying a given power in the chamber; subsequently replacing the O2 flow with an inert gas flow such as N2 or Ar, for a given time period, then depositing an Ag layer under the inert gas atmosphere.

Description

METHOD FOR DEPOSITING Ag ON GLASS SUPPORTS OR THE

LIKE

TEXT OF THE DESCRIPTION The present invention relates to treatments for coating non metallic materials with metallic materials, and particularly to a method for coating glass supports or the like with Ag.

Deposition of metals on non metallic supports has always drawn considerable interest from both aesthetic and technical points of view. In the former aspect, consider containers and objects in general, which are covered with a layer of metal, particularly a noble metal such as, for example, Ag; in the latter aspect, consider the advantage of achieving reflective surfaces which are light, inexpensive, and shapeable in a plurality of different ways. To date, several coating technologies have been used such as galvanoplastics and electroplating, varnishing, the varnish being obtained by forming colloidal dispersions of a metal. All these techniques show both developmental aspects and considerable drawbacks. Particularly with reference to Ag, difficulties are apparently more remarkable, primarily due to its great susceptibility to oxidation. Most modern technologies such as, for example, sputtering and particularly magnetron sputtering are apparently not able to ensure a long-lasting adherence of Ag to glass as well. On the other hand, this kind of material coupling is highly demanded in the market from both technical and aesthetic points of view. The main problem is the oxidation of Ag when contacting the glass support surface, followed by the detachment of the Ag coating even without the application of great stresses.

During the research which led to the development of the method according to the present invention, it has been tried to find out the cause leading to the detachment of the coating and, once this cause has been identified, an aim of the present invention is thus to improve a method for depositing Ag on glass by using techniques of magnetron sputtering, which method allows to deposit metal layers on glass supports in a stable manner.

Therefore, object of the present invention is a method for depositing Ag on glass supports by magnetron sputtering, such method comprising the steps of: placing a glass support to be metallized as well as Ag targets in a low pressure chamber; treating the substrate with an O₂ flow for a given time period while applying a given power in the chamber; subsequently replacing the oxygen flow with an inert gas flow such as N or Ar, for a given time period, then depositing an Ag layer under the inert gas atmosphere.

Preferably, the initial pressure in the chamber is from about 1 x 10^~5 mbar to about I x IO^"4 mbar, more preferably it is about 5 x 10^~5 mbar. Advantageously, the pressure within the chamber is, in any case, no more than about 1-5 x 10^'3 mbar. The chamber is supplied with an O₂ flow having a flow rate from about 20 seem to about 100 seem (standard cubic centimetres per minute), and preferably from about 30 seem to about 60 seem.

The substrate can be treated with O₂ for a time period which can range from about 2 minutes to about 20 minutes, and preferably for a time period from about 4 minutes to about 12 minutes. The replacement of the O₂ flow with an inert glass flow is carried out over a time period comparable to the time period of the preceding step, and particularly over a time period from about 4 minutes to about 12 minutes. During the pre-treatment step, the initial power applied to magnetrons is from about 1 kW to about 5 kW, preferably from about 1.5 kW to about 3 kW. The applied voltage is from about 400 V to about 1 ,200 V, preferably from about 600 V to about 1 ,000 V.

Further advantages and features of the method according to the present invention will be apparent from the following detailed description of an embodiment thereof, provided by way of illustration and not by way of limitation.

The process takes place within a vacuum chamber made of stainless steel, which is provided with a series of (planar and/or circular) magnetrons powered by pulsed DC sources; the chamber is brought to a vacuum of about 5x10⁵ mbar. The substrate to be covered is properly manipulated within the chamber by means of computer-aided robots which allow the substrate to be handled and then evenly exposed to a metallic plasma produced by the magnetrons. Further RF, DC₁ MF sources are used according to process variables in order to obtain RF plasmas and/or ionic discharges which are needed for the substrate to be cleaned, and such cleaning is carried out before the metallization process. Such pre-treatment plasmas/discharges can be produced by suitable ionic and/or RF sources, which are also placed within the vacuum chamber and then properly powered. The whole pre-treatment and metallization process occurs under a plasma environment aided by using various process gases such as nitrogen, argon and/or oxygen according to the cleaning and/or depositing plasmas.

Initially, the process is preceded by a step of preparing the substrate whereby when the requisite vacuum has been attained within the chamber, an activating plasma is produced, and then the metallization step is performed. O₂ is introduced into the chamber at a flow rate of 45 seem; initial power is 2.5 kW, voltage is about 800 V, and current intensity is 16 A; a constant pressure of 3x10³ mbar is maintained in the chamber for a time period of about 8 minutes. The peculiarity of the present process arises from the progressiveness of the oxidative action applied to the glass substrate and from the dynamic control of the process values, resulting in maintenance of a constant value of process vacuum. Deposition of a thin silver layer is preceded by a step of oxidizing the substrate and depositing silver oxide (Ag₂O). While maintaining the vacuum at a constant level, the presence of oxygen is gradually decreased according to established parameters, and the amount of ionizing inert gas (Ar or N₂) is correspondingly increased to allow a gradual increase of the metallic layer to the disadvantage of the oxide layer. In practice, the percentage of inert gas is gradually increased while the percentage of O₂ is gradually decreased for a further time period of about 8 minutes. In fact, by continuing the process, the amount of deposited oxide will be reduced until it completely disappears, while the initially absent layer of metallic Ag will be increased until the oxide layer is completely covered. The Ag layer deposited on the glass support can be from about 50 nm to about 1 μm, preferably from about 100 nm to about 500 nm, more preferably from about 200 nm to about 300 nm in thickness.

The intervening silver oxide layer between glass and metal will ensure a perfect sealing and an excellent resistance to abrasion for the metallic layer.

In contrast with ordinary scenarios, since such deposit is structurally anchored to the substrate, the present process can avoid any subsequent treatment of the coating with protective clear varnishes, so as to maintain unaltered the properties of the metallic coating such as, for example, electrical conductivity or oxidation property.

If properties such as, for example, oxidation property are not desired, then, in a final step, protective clear elements are applied by the same sputtering technique under a high vacuum environment, or alternatively by electron gun or thermal evaporation; such protective elements can be suitable compounds such as silica (SiO₂), alumina (AI₂O₃) and/or other compounds selected according to specific requirements, such elements in all cases being able to remove the unwanted features.

Claims

1. Method for depositing Ag on glass supports by magnetron sputtering, comprising the steps of: placing a glass support to be metallized as well as Ag targets in a low pressure chamber; treating the substrate with an O₂ flow for a given time period while applying a given power in the chamber; subsequently replacing the O₂ flow with an inert gas flow such as N₂ or Ar, for a given time period, then depositing an Ag layer under the inert gas atmosphere.

2. Method according to Claim 1 , characterized in that the initial pressure of the chamber is from about 1 x 10^"5 mbar to about I x IO^"4 mbar.

3. Method according to Claim 2, wherein the initial pressure of the chamber is about 5 x 10^~5 mbar.

4. Method according to any one of the preceding Claims 1 to 3, wherein the pressure within the chamber is, in any case, no more than about 1-5 x 10^'3 mbar.

5. Method according to any one of the preceding Claims 1 to 4, wherein the chamber is supplied with an O₂ flow having a flow rate from about 20 seem to about 100 seem (standard cubic centimetres per minute).

6. Method according to Claim 5, wherein the chamber is supplied with an O₂ flow having a flow rate from about 30 seem to about 60 seem.

7. Method according to any one of the preceding Claims 1 to 4, wherein the substrate is treated with O₂ for a time period which can range from about 2 minutes to about 20 minutes.

8. Method according to Claim 7, wherein the substrate is treated with O₂ for a time period from about 4 minutes to about 12 minutes.

9. Method according to any one of the preceding Claims 1 to 8, wherein the replacement of the O₂ flow with an inert glass flow is carried out over a time period comparable to the time period of the preceding step, and particularly over a time period from about 4 minutes to about 12 minutes.

10. Method according to any one of the preceding Claims 1 to 9, wherein the initial power applied to magnetrons is from about 1 kW to about 5 kW, and preferably from about 1.5 kW to about 3 kW.

11 . Method according to Claim 10, wherein the applied voltage is from about 400 V to about 1 ,200 V, and preferably from about 600 V to about 1 ,000 V.

12. Method according to any one of the preceding Claims 1 to 11 , wherein the thickness of the Ag layer deposited on the glass support can be in a range from about 50 nm to about 1 μm, and preferably from about 100 nm to about 500 nm.