Manufacturing-oriented Microtechnologies

© Fraunhofer EMFT/Bernd Müller
Detailed view processing of foil system to measure temperature

Fraunhofer EMFT is equipped with extensive cutting-edge technological facilities in the area of microelectronics and microtechnology which are maintained by experienced researchers and microtechnologists and used to develop customer-specific solutions. These Manufacturing-oriented Microtechnologies provide the basis for the other areas of expertise at Fraunhofer EMFT, ranging from technology and process analytics to manufacture and testing of components as well as realization of concrete sensor applications by means of system integration.

The EMFT competence manufacturing-oriented microtechnologies is subdivided into the following subthemes: silicium technology and process analytic, low-noise transistors and electrochemical transducers, 3D integration, foil electronics, IC design and system integration.

Silicium technology and process analytic

In the area of technology and process analytics, Fraunhofer EMFT offers an industry-compatible technology platform for testing new process media and optimizing selected process stages, thereby increasing performance and efficiency, for example. On request, it is also possible to realize small-series production – in cases where such small quantities are not available on the world market, for example. A CMOS line (200 mm, structural resolution up to 0.35 µm) is available for producing microtechnology components – all processes comply with the CMOS standard – and there is also a MEMS line (150 mm and 200 mm) for materials which are not CMOS-compatible. In addition to standardized silicon technology, the institution is also able to offer special processes such as silicon-germanium epitaxy as well as a wide range of integration technologies. The latter include 3D integration methods (W-TSV, SLID), anodic bonding at wafer level, the processing of glass substrates (TGV) and various metallization systems (aluminum, tungsten, copper and gold).

This broad range of technologies is complemented with modern in-line – i.e. destruction-free – measuring technology for the purpose of material and process characterization. Alternatively, there are various test structures available for the purpose of off-line process control. In addition, new analysis methods are developed according to customerspecific requirements that are suitable for production which are then integrated in existing production structures. Based on charge carrier lifetime measurements for example, effective methods have been developed to check contamination of high-impedance Float Zone material. Using the technologies available, it is possible to produce numerous components in the institution’s in-house cleanrooms. The focus here is on the development and optimization of electrical and optical components for modern sensor systems. In addition to component manufacture itself, it is also possible to create layouts and carry out extensive testing, e.g. reliability studies (HAST test).

Low-noise transistors and electrochemical transducers

The optical components developed at Fraunhofer EMFT include complex fluorescence modules, classic PIN photodiodes and sensitive silicon photomultipliers for individual photon detection. The latter are used in PET-MRI diagnostic imaging and were developed in close collaboration with an SME. In addition to a suitable sensor, individual photon detection also requires special electronics for signal analysis. In this context, Fraunhofer EMFT researchers develop highly sensitive, low-noise components to detect the very smallest signals. The development and manufacture of low-noise transistors are Fraunhofer EMFT USPs. The institution possesses both the technological and metrological expertise required for JFETs, MOSFETs, varactor diodes and sensors, and this is put to intense use for industry contracts. A recently established lowfrequency noise measurement system is now also being used by Keysight for demonstration purposes. Fraunhofer EMFT has many years of experience in the field of electrochemical transducers, too. Impedimetric, amperometric and potentiometric components are available for this purpose. These enable the detection of various analytes in either the gas phase or in liquid solution.

3D integration

The optical and electrical components available are developed further on an ongoing basis for a range of sensor applications. Entire sensor systems including the appropriate interfaces are designed for demonstration purposes based on market relevance and at the request of customers. Fraunhofer EMFT has systems for pH measurement in liquids, spectroscopic analysis of gases and the monitoring of environmental parameters such as temperature and air humidity as well as the carbon dioxide and hydrogen content of ambient air. The current focus is on networking sensors by means of microsystem integration. Particular attention here is being paid to 3D integration – something that Fraunhofer EMFT has been involved in for many years as a central aspect in linking CMOS-compatible electronics with MEMS-based sensors. In addition, sensors are read out, controlled and networked via standardized interfaces. A collaborative industry venture was set up to create a multifunctional sensor platform for this purpose. This enables all sensors to be activated via USB or on a contactless basis via Bluetooth and NFC. Measurement parameters can then be read out conveniently using a commonly available smartphone, for example.

Foil electronics Flexible, multifunctional electronics offers new possibilities for a range of smart, high-capacity products – in the context of the »Internet of Things« vision, for instance. In-house reel-to-reel production systems enable low-cost processing of foils and other flexible substrates to develop flexible, bendable, flat and large-area electronic systems. Since the beginning of 2020 Fraunhofer EMFT has had a pilot line with reel-to-reel lithography, laser structuring, printing, vacuum-based techniques and system integration. This enables cost-effective processing for the development of electronic systems that are simultaneously thin, flexible and large-area.

To realize flexible electronics, foil processes developed at Fraunhofer EMFT are combined with techniques drawn from various conventional technological fields (e.g. silicon, MEMS or circuit board technologies). Here, heterointegration of silicon and foil technology has a key technological role to play: while silicon technology allows extremely miniaturized components to be realized, foil technology offers greater scope for design, enabling flexible, flat and biocompatible electronics. Examples of applications include sensors on curved surfaces, on-body sensors for health monitoring, multimodal sensorics for robots which will interact with human beings in the future, smart textiles and a wide range of distributed and networked sensor modules for the intelligent control of machines and processes generally grouped under the catchword Industry 4.0. The combination of capabilities in the area of thin silicon and foil technology allows the realization of rewired ICs packaged in foil ( chip-in-foil package) without having to dispense with the advantages of low installation height and flexibility. 

Thin silicon: Extremely thin silicon chips are required for heterogeneous 3D integration and chip-in-foil packages. A fundamental requirement here is the technological expertise to produce thin wafers. The Munich site is excellently equipped for the complex processes required for thinning, so the devices produced at wafer level can be as thin as needed. Fraunhofer EMFT offers its patented »dicing by thinning« technique for the purpose of chip separation for very thin semiconductor wafers. These technologies can be used to create thin and flexible silicon chips with a thickness of 10 µm - 30 µm. Handling extremely thin silicon wafers of this kind poses considerable challenges. The techniques and aids for safe handling of thin silicon such as electrostatic carrier systems ( e-carrier and e-foil) are likewise among Fraunhofer EMFT’s areas of expertise.
IC design

Microchips are at the heart of countless products: they cluster numerous functions inside a minute space. However, very specific applications or the capacity to tap into new functions and areas of use, increased miniaturization, enhanced energy efficiency, low manufacturing costs and greater reliability often require new IC designs that are not available on the market in this form. Here, Fraunhofer EMFT supports its customers in designing complex analog and mixed-signal circuits, focused on novel sensoric concepts and millimeter design (SAR-ADC, Sigma-Delta ADC, PLL, microwave structures).

System integration

By means of demonstrators, prototypes and systems, Fraunhofer EMFT scientists are able to illustrate potential application scenarios for the technologies and components developed at the institution. For customers, this development expertise is an essential part of the Fraunhofer EMFT service portfolio: SMEs in particular often require complete solutions rather than individual components. In particular, extensive expertise in system development provides an essential basis for translating innovative technologies and solutions (such as energy harvesting and ultra-low power consumption) quickly and successfully into applications to create future-oriented products. The development expertise of our experienced interdisciplinary team covers hardware and software, electronics, mechanics, optics and fluidics with micropumps and micro valves as well as the incorporation of innovative numerical signal processing concepts. Services in the area of system development range from drafting initial concepts through to feasibility demonstrators, prototypes and complete systems, depending on requirements.