Very small inertial measurement units (IMU) are necessary for measuring the aircraft wing deformation during flight. This objective can be only met, if the sensor system is highly integrated. GEMAC and AMAC developed in the project an ASIC in which all necessary analog blocks are implemented (high performance switches, charge amplifier, temperature probe, gain and offset, ADC, eventually voltage reference). The first development step was the analysis of the specification and the existing mock-up to investigate and to confirm the feasibility of ASIC integration, to evaluate risks and to setup the detailed planning. In this phase, GEMAC needed continuous support from the consortium partner Sagem. After a Go-Ahead decision the final system architecture was defined, followed by the design and simulation of the single blocks and the whole system including the interfaces to the MEMS element and the surrounding system electronics. Mentor tools were used for all simulations in the design flow. In order to minimise risks and to save time, the first run covered only the main components of the system. The designed and checked layout were transferred for preparation to XFAB. The company is one of the leading semiconductor and ASIC manufacturers in Europe and offers all state-of-the-art technologies for analogue, digital, mixed signal designs. GEMAC has business contacts to this fab for many years, all necessary libraries are available.
After delivery the ASIC samples were tested together with Sagem. In the result, a list of necessary redesign activities were setup. In parallel the design was completed with the still missing functional blocks. After successful simulation of back-annotated netlists the second run started. The samples supplied by XFAB were tested again together with Sagem.
GEMAC and AMAC are R&D oriented SMEs with experiences in ASIC design and microsystem technology as well as MEMS based acceleration sensors for many years. AMAC is a spin-off of GEMAC and has taken over the Micro-IMU project in March 2016. With its participation in Clean Sky the companies intended to contribute to the goal of Clean Sky to speed up new and greener aviation designs to protect our environment.
One of the main goals of the Clean Sky Joint Undertaking (CSJU) is to speed up new aviation designs to protect our environment. This requires a complex innovation of all parts of the airplane. For instance, very small inertial measurement units (IMU) are necessary for the measurement of the aircraft wing deformation during flight. For this purpose, highly integrated sensor systems are needed. The goal for GEMAC/AMAC was the integration of the analogue part of a MEMS based accelerometer into an ASIC to reduce size and power consumption as much as possible and to fulfil the overall system requirements.
The MEMS based accelerometer consists of the sub-blocks high performance switches, charge amplifier, temperature probe, gain and offset, integrated 14-bit-ADC and voltage reference.
After a deep analysis of the system requirements and the capabilities of existing technologies, the XH035 CMOS technology from XFAB was selected for the ASIC manufacturing. After refinements of project planning and specification the design process started. To minimise the design risk, two preparations were planned. The first ASIC contains only the main components of the analogue part of the MEMS accelerometer, the switches ("ASIC A1"). Additionally, another main block was integrated in a separate test chip, the charge amplifier. In parallel to the fabrication phase of ASIC A1, the design, simulation, layout generation of the remaining blocks for the accelerometer system to be integrated in the final ASIC ("ASIC C") as well as the system integration of this ASIC started.
In March 2016 the ASIC department of GEMAC, the only partner in the Micro-IMU project (single submission) was outsourced into a new company, the "AMAC ASIC- und Mikrosensoranwendung Chemnitz GmbH". The project was transferred to AMAC in form of a PTRO (Partial Transfer of Rights and Obligations). Due to administrative reasons, especially the XFAB order, this resulted in a delay of the first preparation (ASIC A1 and test chip) and a modification of the project planning.
After delivery from XFAB the ASICs were tested. Except one parameter of ASIC A1, both ASICs have the requested functionality. The problem was the power consumption. ASIC A1 works only up to a voltage of +/-7V correctly. When operating with a voltage of +/-9V (as specified) the power consumption exceeds the specified value. After a complex failure analysis, parasitic effects in the layout were detected as reason. Complex design measures were taken to overcome the problem. Because a part of the wafers had been stopped it was possible to modify the layout on metal mask level and to continue the fabrication of this batch with a modified layout. However, not all modifications could be implemented. That's why the modified ASIC A1 did not meet the specification, too. The full set of modifications was implemented in the layout of ASIC C. Unfortunately, a fabrication problem arose in the fab. This caused a delay in the supply of ASIC C. Because a prolongation of the Micro-IMU project was not possible, the ASIC C will be tested now at AMAC after the official project end at own expense. It shall be guaranteed, that the CSJU partner SAFRAN will get the needed ASICs for industrialisation. In this way it will be possible to meet not only the scientific, but also the economic objectives of the project.
AMAC will replicate the acquired know-how for sophisticated analogue designs in other customer projects and for the development of own products. This will improve the market position of AMAC. In case of a correctly working ASIC C, a direct economic benefit will result from the purchase of ASICs to SAFRAN.
Because of the special characteristic of the project (single submission), dissemination activities were not planned. Publications and other dissemination activities will be made by the members of the Cleansky consortium.