Fraunhofer ENAS- Institute for Electronic Nano Systems

Next Level Nanofabrication in the interaction of

SIMULATION - Simulation of Semiconductor Processing with process models for virtual process optimization and prototyping 

TECHNOLOGY - Task force advanced CMP and nano processes for future technologies

INLINE METROLOGY - AFM and defect inspection tools

ARTIFICIAL INTELLIGENCE - Knowledge-enhanced digital twins, e.g. demo CMP: digital twin for Chemical-Mechanical Planarization

Fraunhofer ENAS offers research and development services on the whole spectrum of semiconductor and nanotechnological processes for the fabrication and integration of electronic, optical and mechanical micro and nano devices. To this end, individual processes are being further developed and, above all, process and technology integration concepts are being established and implemented. The main focus is on advanced patterning processes based on micro- and nanolithographic methods, a variety of different dry etching processes from reactive ion etching (RIE) to gas phase etching as well as wet etching and cleaning processes. Electron beam lithography and nanoimprint lithography (NIL) are of particular interest, as they allow flexible and cost-effective production of structures with dimensions below 50 nm for industrial applications. Furthermore, a wide range of deposition processes is available to ensure the necessary material diversity. From atomic layer deposition, conventional PE, LP and MOCVD processes, high temperature processes, electrochemical deposition (ECD), electron beam evaporation to specific sputtering processes, many functional materials can be used on 150 and 200 mm substrates. The process portfolio is rounded off by processes for surface treatment and substrate processing. Several systems for chemical mechanical polishing (CMP), grinding and spin etching are available for this purpose. In addition, MEMS packaging processes and a large number of inline metrology and measurement tools are available for the realization of systems.

Fraunhofer ENAS has technologies for the production of micromachined ultrasonic transducers (MUT). Each ultrasonic transducer consists of a number of basic cells which are electrically excited to oscillate. These oscillations are emitted into the environment as a sound signal. If the sound waves hit an object, e.g. tissue, the signal is reflected and the MUT -electronics evaluates the data.

Depending on the application, the MUTs can be capacitive (CMUT) or piezoelectric (PMUT). In addition to the technology for manufacturing the transducers, Fraunhofer ENAS has expertise in developing packaging concepts to protect the MUTs in the respective application environments as well as in developing customized electronics and system integration, even for harsh application environments.

Fraunhofer ENAS offers standard wafer level bonding technologies such as silicon direct, anodic, glass frit and adhesive bonding. These technologies can be adapted according to the specific requirements of target applications.

Other bonding techniques including thermo-compression, solid-liquid inter-diffusion, eutectic, surface activated and reactive bonding are also available and can be optimized for different requirements (e.g. process temperature, yield and bond strength). Other approaches for wafer bonding are primarily driven by the emergence of new materials and processes in micro systems technology. We have articularly studied bonding methods for plastics, metals and ceramics; considering process temperature constraints, substrate chemical resistance and low cost processes. The examples of these processes are thermo-compression bonding or reactive bonding, both based on forming compounds between two metals.

Different techniques are also available for improving the bond quality; some of these pre-treatment processes are: wet or dry surface modification, plasma activation (particularly for direct bonding) and chemical mechanical polishing.

A relatively new trend in wafer bonding is temporary bonding. This has gained a great deal of interest due to the increasing demand for wafer thinning. Wafer thinning (for thicknesses down to 50 µm) facilitates new applications such as 3D interconnections (based on through silicon vias or other stacking technologies), reduced device thickness (thus flexible devices). Temporary wafer bonding/deboning assists with the handling of ultra-thin wafers which is otherwise challenging or not practical. The institute has developed an adhesive based temporary bonding/debonding process for the handling of thin wafers with sufficient mechanically stability. Once the thinned wafer is processed it can be removed from its carrier wafer using a room temperature peel-off debond process.

For both permanent and temporary bonding, clean rooms with fully integrated process line including characterization equipment for the processing of 4"to 8" substrates are available at Fraunhofer ENAS