DD277455A1 - DIFFUSION MASK FOR ION EXCHANGE IN GLASS - Google Patents

Abstract

The invention relates to a diffusion mask for ion exchange in glass. Such masks are needed to fabricate planar waveguide structures. The invention relates to an embodiment which is intended for use in less acid resistant glass. It consists of a layer applied to a glass substrate preheated to 200 to 250, which consists of approximately equal proportions of chromium and nickel and has a thickness of 100 to 300 nm.

Description

Subsequently, the glass substrate passes through the sputtering target by rotation of the sample tray. As the target material, a Ni-Cr alloy having a chromium content of about 60% is used. By sputtering is now applied to the glass surface, a Ni-Cr layer of about 250 nm thickness.

2. Photolithographic structuring

Positive resist is recorded on the Ni-Cr layer. This photoresist layer is exposed through a photomask and then Entwicke't.

3. wet chemical etching

The glass substrate with metal layer and applied lacquer structure is exposed for about 150 seconds to an etching bath of the following composition:

165mg Ammoniumcer-IV-nitrate 43ml perchloric acid (70%)

(Values refer to 11 process solution).

In this etching process, the non-photoresist-covered parts of the metal layer are etched to the glass surface. An attack of the glass surface takes place only with an etch rate of 0.3 μηη / min against (3 to 4) Mm / min when using aluminum and titanium masks. This weak glass attack no longer affects the properties of the manufactured waveguides

 Finally, by means of acetone and ethanol, the detachment of the remaining on the metal layer photoresist.

Claims (1)

Diffusion mask for use in ion exchange in low-acid resistant glass, consisting of a layer applied to a glass substrate preheated to (200 to 25) ⁰ C, characterized in that it consists of approximately equal proportions of chromium and nickel and has a thickness of (100 to 300 ) nm. Field of application of the invention The invention relates to a metallic diffusion mask for ion exchange in glass for the production of planar waveguide structures. Such diffusion masks are applied to the glass surface so that upon contact of the glass surface with a melt containing metal ions, ion exchange between the network transducer ions of the glass and the metal ions of the melt can only occur through the windows of the diffusion mask. The ion exchange generates waveguiding structures in the glass. Characteristic of the known technical solutions For ion exchange in glass, diffusion masks of titanium, aluminum and chromium have hitherto been used (Applied Optics, Vol. 23, No. 11, June 1,1984, pp. 1745-1748; Electronics Letters, vol. 22, No. 17,14th August, pp. 925-926; Weiß, Th., Diploma thesis, FSU Jena, 1984). In the production of diffusion masks, a metal layer applied to a glass substrate is covered with a photoresist structure and then exposed to an etching bath. The areas of the metal layer not covered with photoresist are etched away. When using titanium and aluminum as the mask material, strongly acidic etching baths are necessary for the wet-chemical etching of the metal layers. However, these etching baths also lead to an etching of the glass surface ar. the places where the metal layer was previously etched. Etched glass surfaces lead to considerable transmission losses in the waveguides produced by ion exchange. In order to prevent the etching of the glass surface, chromium was therefore used as mask material *. Chromium can be treated wet-chemically with a less acidic etching bath. Using this chromium etching bath, the glass attack was greatly reduced, so that it no longer has any influence on the properties of the waveguides. During the ion exchange, however, an inward diffusion of chromium ions over the diffusion mask takes place in the glass surface, which leads to a change in the refractive index profile and thus to increased transmission losses of the waveguides produced. Object of the invention The aim of the invention is to avoid quality losses in the production of waveguiding structures, which are caused by etching of the glass surface or indiffusion of the mask material. Explanation of the essence of the invention The invention has for its object to develop a material for diffusion masks for ion exchange in glass, which can etch wet etching with an etching, which does not or only slightly attacks the glass surface, and does not diffuse into the glass surface during the ion exchange process. This object is achieved by a diffusion mask for use in ion exchange in low-acid resistant glass, consisting of a layer applied to a glass substrate preheated to (200 to 250) ° C, in that it consists of approximately equal proportions of chromium and nickel and a thickness of (100 to 300) nm. It is therefore essential that the metal layer applied to the glass substrate consists of approximately equal parts of chromium and nickel. On the one hand, this layer can be wet-chemically treated by means of a chromium etching bath, without a strong attack of the glass surface occurring at the same time. prevented, so that the properties of the produced waveguides are no longer affected by the mask material. With a significantly higher proportion of nickel than chromium in the metal layer, however, this can no longer be treated with a chromium etching bath, which in turn leads to severe glass attack. embodiment The invention will be explained with reference to an exemplary embodiment for the production of a diffusion mask. Dio Maskonherstellung follows the following technological steps: 1. sputtering The application of the NiCr layer on a glass substrate by means of DC Plasmatron sputtering. Here, the glass substrate to be coated is mounted on a drohbnron sample tray in the recipient of the sputtering. In the first position of the sample tray is the glass substrate untor oinor tungsten lamp, which heats the glass to about (200 to 25O ⁰ C).