Community Research and Development Information Service - CORDIS

Periodic Report Summary 1 - SIMIC (Silicon Microphone)

1. Publishable Summary
Summary of the project :
MEMS (Micro-Electrical-Mechanical System) based microphones, so called “silicon microphones” - are relevant in many applications as their manufacturability is better compared to electret condenser mics (ECM). Often MEMS mics hold embedded ADCs (Analog-to-Digital Converter) on the same CMOS chip. Those “digital output mics” perfectly fit into innovative digital products e.g. smart phones. Extremely small form factors and better performance in dynamic range and high sound pressure levels (voice recognition&command, music recording) are highly requested.
The project aims to develop revolutionary components for Silicon based microphones (SiMic) that can satisfy the new challenging requirements of multiple marketplaces. Smart phones need up to three microphones each and the produced volumes tend into several billion pieces per year – one of the strongest increasing market demands worldwide. It is of vital interest for European academia and semiconductor manufacturers to be at the top with developments. Academia needs possibilities to work on solutions nobody has ever thought of and industry has to follow the needs of the global customers. The requirements of microphones for mobile applications have significantly increased from acceptable telephone quality with signal to noise ratio of 58dB(A) up to a State-of-the-Art SNR of >64dB(A). The desire to record music with ultimate dynamic range of more than 110dB still pushes for lower ground noise and higher linearity.
UC3M is well known for its highly innovative concepts and forefront research. Quality of those concepts strongly depends on features of the technologies needed for system integration, competitiveness of academia is connected to the access to latest manufacturing technologies. SiMic collaboration approach guarantees, that UC3M system and circuitry concepts will be leading edge within the EU.
IFAT is the second largest supplier of SiMiCs using ASIC designs, similar to those used with ECM. From customer feedback IFAT anticipates the need for advanced electronics and sensors with focus on developing new ASICs for novel read-out topologies for existing and new MEMS sensors.
IFAT envisions possible techniques to cope with the challenges but it is extremely difficult to find the researchers (and a budget) to cover the risks related to unproven concepts. Therefore the requested funding will be used for target oriented innovation with room for creative concepts thus enabling new products for a growing market and investment in more resources at the research institute.

Summary description of project objectives and work performed
Performance of silicon microphone system is mainly influenced by 3 parts: the signal sensor MEMS - the interface, circuit (transforming the signal into processable data) - and a converter (ΣΔ ADC) delivering the digital output signal. SiMic project will address all those 3 parts. The objective of the SiMic project is to address and improve all these three core parts.

Objective 1: Core part MEMS
Work is performed in WP2
WP Leader: Enrique Prefasi (UC3M) + Richard Gaggl (IFAT)
An evaluation of ideas and concepts shall allow to define a way out of the limits given by the state-of-the art MEMS. As the project is limited due to budget and resources the main focus is on modelling of the different MEMS concepts. The focus will be on MEMS for pressure management. With this we are also able to answer direct market requests from customer requirements asking for an integration of microphone and pressure sensor functionalities.
During the project run it was found out that the main focus for the SiMiC shall be on ASIC development. MEMS direct development is done in the MEMS development center of Infineon in Munich. All necessary MEMS requirements for implementation of SiMiC are available as models.

Results of Objective 1:
- Simulation models for different types of MEMS are available
- Models are ready for design of read-out circuits

Objective 2: Core part Interface
Work is performed in WP1 and WP2
WP Leader: Luis Hernandez (UC3M) + Andreas Wiesbauer (IFAT) and Enrique Prefasi (UC3M) + Richard Gaggl (IFAT)
Evaluation on a beyond-state-of the art solution for handling of higher sound pressure levels (HSPL) and explore a) time encoded microphone interfaces and b) interface-topologies measuring the change of current (not voltage)

Results of Objective 2:
- A test chip has been proposed with a second order noise shaping sigma delta architecture. The initial design (block diagram) for this chip was proposed in T1.1. In this new specification phase, the block diagram has been evolved into a fully digital design which does not need analog integrators.
- A study of the actual Capacitive-to-Digital Converter (CDC) implemented by IFAT was done by UC3M. After this stage a second order DT-SD ADC was implemented. A tape-out including the preamplifier and the DT-SD ADC was done by IFAT. At this moment the first C-V stage plus the DT-SD ADC has been characterized by IFAT in the lab and the main results have been discussed between IFAT and UC3M.

Objective 3: Core part AD converter
Work is performed in WP3
WP Leader: Susana Paton (UC3M) + Dietmar Straeussnigg (IFAT)
Research and evaluation of concepts for a power and area efficient ADC concept for high sound pressure (HSPL) applications.

Results of Objective 3:
- Ultrasonic: We have developed a concept to extend the usable bandwidth of the ADC, with minimum hardware modification, and preserving the microphone high resolution. It can be applied to the existing Switched capacitor ADC, by adding some capacitors in the analog side and a digital filter at the output.
- Audio: Several architecture studies have been done. As a result one architecture, fulfilling all requirements, has been selected. With support from IFAT senior experts, in research on possible architectures, the IFAT reference architecture (used in the first High SPL product) for ADC was provided to UC3M.

Expected final impact:
For IFAT the work so far is highly interesting in both technical/scientific as well as cooperation wise with the UC3M in the fight for the best talents on the market.

Development of new/old intersectoral cooperation
The cooperation is very fruitful as it is based on already existing first experiences. There has not been any delay as the key scientists in charge already knew each other and could start on a reliable network. The researchers exchanged in the secondments are all highly motivated. The cooperation is going beyond the current project work. This is also shown by the visits Dr. Dietmar Straeussnigg had in Madrid where he gave lectures to students at the University. This was fully supported by Infineon.

Expectations to create a long-lasting strategic cooperation:
The results of the project are very promising for futher cooperations. Senior experts have been exchanged and additional plans for projects are already in the pipeline. Furthermore IFAT is giving secondees a chance to do project work in Villach (employment contract) after the project end.
The research carried out by UC3M enables Infineon to make use of concepts that are created outside the harsh business environment with all the restrictions given by budget and time pressure. These concepts are developed in a kind of “free” research area and ready for studies on possible applications. Therefore already at this stage of the project concepts have been evaluated and feasibility studies have been carried out.

Impact on the future career prospects of the secondees:
All secondees are directly involved in the structures and organization of IFAT in Villach, being directly exposed to real industrial procedures, methodologies and processes. Furthermore they get direct insight into real business interactions.

Benefit to the mobility to the REA:
There is a frequent exchange of students (internships) between Austria and Spain building up a close cooperation via networks established during these exchange periods

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Life Sciences
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