- A CMOS-compatible manufacturing process for the targeted sensor microsystem has been developed, which is proven to work in principle. This includes processing of the CMOS front-end, and non-standard sensor specific back-end process modules such as planar structuring of Ag, Pt, Au, Ti and Polyimide on top of the CMOS front-end.
- for the first time, three major electrochemical measurement principles (potentiometric ISFET, amperometric and conductometric) have been integrated on a cost-effective CMOS-compatible microsystem platform, along with signal processing and system control functionality (temperature control, potentiostat, multiplexing, non-volatile memory). In the combination of these measurement principles, it could be shown that any combination of the following analyte classes can be realized very flexibly on the same chip substrate, by just varying dispensed sensitive/selective membranes on top of the ISFET gates or the electrochemical micro-electrodes:
- gas partial pressures in fluids, like ph, pO2, pCO2
- electrolyte ions like Ca, K, Na, Cl
- other ions like NH4, Nitrate
- organic ions / metabolites like Glucose, Lactate, Glutamine, Lactose, Saccharose, Maltose, Galactose
- conductivity-characteristic features of fluidic mixtures, like hematocrit
- Ready-to-use wafer-level dispensing equipment for various fluids with leading-edge specifications has been developed, which is scaleable for automated volume production. Positioning accuracy of the systems is better than 10 µm, dispensing of volumes in the nanoliter range on a spot size of 100µm was achieved.
- supporting technology such as housing, assembly, fluid handling circuit, calibration solutions, and some aspects of a sterilization procedure, has been developed in parallel.
- The major remaining risks and problems are:
- insufficient yield of the last batch run, such that available sensor wafers would not be suitable for a market introduction. If market exploitation were considered, the process would have to be transferred from IMEC into a commercial fab environment with a suitable quality control infrastructure, and then fine-tuned to increase the yield such that market-compatible prices for the sensor microsystem can be achieved.
- a quality-assured and volume-scaleable electroplating process for Ag/AgCl on wafer level still requires major investment.
Objectives and content
There is a very high market potential for multiparameter microsensor systems, which are capable of monitoring continuously and on-line important constituents of liquids in a production process, such as partial gas pressures, electrolytes, or metabolites. Process monitoring permits a much faster reaction on a process variation improving quality and reproducibility of the process. There are urgent user needs for such process monitoring devices especially in the biotechnological industry, but also in the food industry. Other highly important fields for monitoring constituents in liquids is health care (monitoring critically ill patients in intensive care units or in the operating room) and environmental measurements (water quality, pollutants). Sensor devices suitable for such monitoring should ideally fulfil these requirements: be small (to be implemented directly in processing equipment, save analyte material), measure many different parameters, and be cheap. Silicon microsensors based on ISFETs (Ion-Selective Field-Effect Transistors) are a very promising technology which fulfils these requirements:
- they have the potential for cheap mass production, using planar thinfilm photolithography technology
- a broad spectrum of measured parameters is possible, all using the same sensing technology
- the sensor elements are very small, they can he integrated in sensor microsystems
The extensive research in this field in the last decade lead to a solid understanding of the functional bases of this sensor technology, and the satisfying performance has been proven in many evaluation studies. But these sensors up to now were only manufactured in scientifically oriented institutions, the costs per sensor are still far beyond a price that allows marketing the sensor. Market acceptance will only he given if the sensor is cheap. The sensor will only be cheap if cost-effective mass-production can be achieved. What is needed today is the transfer of the scientific know-how to the development of a cost-effective high volume production technology. In this project, a sampletaking multiparameter ISFET sensor device, developed by Siemens Corporate R&D, measuring po2, pCo2 and pH, will be used. The major obstacle of a cheap high volume production technology is the current non-compatibility of the technology with industrial CMOS lines. The major goals of the project are:
- redesign of the manufacturing process to be compatible with industrial planar thinfilm production lines.
- implementation of the compatibility with a broad application range during the design phase of the process
- adding further measurement parameters to open up more applications - increase degree of integration in the microelectronics of the sensor, to further decrease the price.
The following achievements are expected after successful completion of the project:
- development of a manufacturing technology for an ISFET based multiparameter sensor microdevice in monolithic integration with CMOS electronics, which closes the gap between scientific manufacturing of single pieces and industrial high volume production by being both cost-cffective and transferable.
- tailoring the manufacturing process for SMEs, since the expected market volume of some million pieces per year is too high for scientifically oriented organisations, but too low for typical mass production lines. - development of cost-optimised microassembly and packaging, including fluid circuit, for the microsensor.
- use the synergetic potential of the microsensor by assuring the applicability in a broad range of applications - to make available to the industry a leading edge technology for process monitoring.
Funding SchemeCSC - Cost-sharing contracts
3000 DR Rotterdam
171 95 Solna
13040 Saluggia Vercelli