SAWLASE: Nano-fabrication of DFB lasers and SAW devices by off-axis holographic lithography

• Unité de recherche: PCRD EU
• Numéro de projet: 98.0000
• Titre du projet anglais: SAWLASE: Nano-fabrication of DFB lasers and SAW devices by off-axis holographic lithography

Mots-clé (Anglais)

DBF lasers; saw filters; holography; sub-micron lithography;

Autre Numéro de projet (Anglais)

EU project number: BRPR-CT98-0679

Programme de recherche (Anglais)

EU-programme: 4. Frame Research Programme - 2.1 Industrial and materials technologies

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

Coordinator: Alcatel (F)

Résumé des résultats (Abstract) (Anglais)

The project's objectives were to develop fabrication technologies for higher performance distributed feedback (DFB) lasers and surface acoustic wave (SAW) devices for optical telecommunications and cellular telephones respectively. Holtronic Technologies' role is to develop a new high-resolution lithographic technology based on off-axis TIR holography to enable patterns with features down to 120 nm linewidth to be printed using an exposure wavelength of 364 nm.
After having experimentally validated this technology on an experimental test-bed, a step-and-repeat recording equipment was designed, fabricated and tested. This system includes UV beam shaping optics, scanning UV illumination, focus control of the mask with respect to the hologram substrate, high-precision motion of the prism controlled by an interferometer, as well as electronics and software for fully automatic operation. It allows the recording of a small pattern (typically 5x5 mm2) to be repeated in a 2-dimensional array over a 4 inch x4 inch full field hologram. Such a hologram, although recorded with a special off-axis illumination of the mask, is fully compatible with Holtronic Technologies' standard printing equipment, namely its holographic mask aligner HMA150, enabling a large number of device patterns to be printed over the complete wafer in a single exposure.
The recording equipment has been employed to record holograms of sets of gratings with a dispersion of grating periods centered on 240 nm, corresponding to the periods needed in DFB lasers for DWDM application. The holograms have then been reconstructed on Holtronic's HMA150 lithographic equipment to print the grating patterns into 60 nm photoresist on 2' diameter indium phosphide wafers. The structures thus formed have been confirmed by the customer to be fully compatible with their standard semiconductor laser manufacturing process. The technique thus provides a powerful means for monolithically fabricating DWDM laser sources for high-density fibre-optic communication, especially for internet application.
Holograms have also been recorded of high-resolution patterns for SAW filter application. In this case the device patterns are not pure gratings but interdigital patterns of lines and spaces whose individual widths vary along the device structure. Initial testing was conducted with patterns comprising 150 nm lines with a randomised distribution of separations. The results have demonstrated that the off-axis holographic technique can also be successfully applied to such cases. 3' diameter aluminium coated quartz and LiTaO3 wafers printed with these patterns using the HMA150 equipment have undergone post-exposure processing prior to evaluation. Device manufacture using other pattern geometries and design techniques, corresponding to alternative filter functions are currently underway.

Références bases de données (Anglais)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 98.0000