Among the seven promising inventions shortlisted from over 140 for this year's Berlin-Brandenburg Innovation Award is a project developing thin-glass deposition onto substrates. The micro- and even nanometer layers could revolutionize countless applications in opto- and microelectronics.

In principle, its chemical resistance and transparency make glass the perfect material for electronic optical components thanks. However, it is also brittle, requires high processing temperatures and is difficult to process mechanically. These drawbacks have meant that glass is rarely employed in microelectronics. One of the few examples of its use to date has been for insulation.

Researchers from the company MSG Lithoglas AG and Fraunhofer IZM have now developed a new process called “additive microstructuring” that makes manufacturing image and photo sensors for applications such as high-resolution camera chips or photodiodes for BluRay drives extremely simple and cost-effective. Thanks to its biocompatibility it also holds great potential for medical technology.

Established methods such as wet etching or sand blasting have traditionally been used to apply micrometer structures to glass. Here, tiny layers of glass substrate are eroded or, to put it another way, subtracted. Other processes also exist in which extremely fine structures are applied to the glass substrate. However, the generally high processing temperatures of such additive processes, which include for example screenprinting, often change the optical characteristics and the range of suitable substrate materials is extremely limited and organic carriers cannot be used. Moreover, the processes are also extremely expensive.

The method developed by the Berlin researchers not only avoids these pitfalls, but also yields structures 50-times more precise.

The researchers based the technique on a principle discovered over 30 years ago: electron-beam vaporization. In this vacuum process, a solid (borosilicate glass) is vaporized and then subsequently condensed in extremely fine structures on a glass surface – hence the term “additive microstructuring”. The Berlin-based scientists developed this process further, producing glass microstructures with a width of less than 2 µm – one-fortieth of the width of a strand of hair.

Because the temperatures do not rise above 120 °C during the structuring process and established processes such as lithography can be used for several wafers in parallel, the outstanding optical characteristics of glass are retained while processing costs are kept low.

Applications for this technology are virtually limitless. It can be employed cost-effectively and for high-volume manufacturing wherever optical information is processed in microelectronics, including for micromirrors in scanners and displays, in acceleration and pressure sensors, as light sources such as semiconductor lasers and LEDs.

Fraunhofer IZM as incubator
Dr. Jürgen Leib, former research head for wafer-level packaging at SCHOTT AG and co-founder of MSG Lithoglas AG: “Our team is the outcome of a very productive and long-term cooperation with Fraunhofer IZM in Berlin. The special environment and collaboration with the institute, which a world leader in the area of advanced packaging, prompted to us start an independent initiative and also to establish it in Berlin. Fraunhofer IZM was a type of incubator for our young company and the cooperation made it possible for us to reach the necessary critical mass necessary to take on challenging development tasks.”

MSG Lithoglas AG researches, develops and manufactures products that involve hermetic passivation of semiconductors with glass. The core technology of the spin-off, which numbers employees from Berlin’s Fraunhofer IZM and former staff from SCHOTT AG, includes a patented process for vaporizing and microstructuring borosilicate glass at low processing temperatures on semiconductor substrates.

With its flexible technology, which skillfully exploits optimal material characteristics while keeping manufacturing costs low the young start-up may indeed be a strong contender the Berlin award.

The Innovation Award is presented every December to a maximum of 5 entries, which each receive 10,000 euros. An independent jury of 16 members nominates and decides on the winners.

The lithoglass pioneers and their colleagues from Fraunhofer IZM have now reached the last round. All going well, they will also be included when the awards are presented on 5.12.2008.