A process based on hot viscous molding of glass has been developed at Fraunhofer ISIT. With the help of this process, it is possible to structure glass wafers with high aspect ratios at wafer level in such a way that the good optical properties are retained.
For this purpose, glasses must be used whose softening temperature is significantly below that of silicon. A structured silicon wafer is selected as the so-called master mold. This has the advantage that the standardized processes for structuring silicon in a clean room can be used here. The structures or cavities introduced later correspond to the molded areas in the glass. The etched silicon wafer is then anodically bonded to a glass wafer. In this process, a defined pressure can be enclosed within the cavities. This later determines whether the glass is drawn into the structures or blown out. Depending on the application, the glass can now be further processed by grinding and polishing. The silicon wafer is then removed by wet chemical means.
With the help of this unique technology, new components can be manufactured from glass at wafer level for the first time that meet the qualitative requirements of optics. Thus, microlenses, reflectors and specially shaped optical windows can be realized in large quantities at wafer level without further mechanical processing, which enables cost-effective mass production of micro-optical devices (wafers with gold-plated concave mirrors). In combination with MEMS scanners and active optical devices, this manufacturing process is the key to hermetically encapsulated MEMS devices that meet the high demands of optical functionality (MEMS mirrors with slanted windows). The slanted windows avoid the back reflection of the incoming laser beam into the projected image area. The components are integrated into systems and find application in the fields of image projection, light structuring, data transmission by laser radiation and material processing, among others.
Our innovative glass flow technology is particularly well suited for silicon optics. The process benefits from standardized procedures for structuring silicon in a clean room. Learn more about this process in our video.
Fraunhofer Institute for Silicon Technology
