LONDON — ChipSensors Ltd., a Limerick, Ireland-based startup with a pedigree in sensors and mixed-signal CMOS design, has unveiled a technology that it claims will let the surface of an IC sense temperature, humidity, pathogens and certain gases.

Sitting above a conventionally manufactured complex CMOS IC, the embedded-sensor technology may be used to create miniature yet conventional industrial, scientific and medical sensors, with the IC implementing the microcontroller and wireless transmitter to send collected data off-chip.

Central to the technology is the low-k dielectric found in standard submicron CMOS processes. The material's porous nature makes it possible to change its dielectric constant by selectively admitting or blocking ingress of the agent to be sensed, thereby forming the basis of a capacitive sensor.

Normally, the surface of an IC is passivated, so ambient conditions don't affect it. Similarly, the pores of low-k materials are often closed using surface treatment. But ChipSensors claims that exposing a prepared area to ambient conditions allows the resulting electrical characteristics to be detected and measured by means of on-chip circuitry.

Challenging the prevailing view that moisture compromises an IC's long-term reliability, ChipSensors CEO Tim Cummins insists that modern low-k dielectrics aren't prone to swelling. "We can selectively open up part of the surface of the chip, he said. "We usually use only the top level of a multilevel interconnect. The etch-stop layer can prevent buried layers from being affected. The variation in dielectric constant due to moisture or gas ingress can be measured using an 18-bit sigma-delta A/D converter the company has developed.

The sensor technology may be applied as a separate process after conventional chip production or as a method for measuring the fringe capacitance of a prepared dielectric on the surface of a chip, Cummins said. ChipSensors has proposed the use of an in-circuit heater element to purge moisture and return the porous dielectric to its original condition, ready for reuse.

Cummins expressed confidence that the technology will work with CVD and spin-on dielectrics from multiple suppliers. "We've made 0.18-micron CMOS prototypes with UMC through the Europractice multiproject wafer service without any special steps, he said.

ChipSensors has also attracted the attention of a U.S. company, which is providing 0.13-micron devices. Cummins would identify the partner only as "a microcontroller company.

Though it appears the technology would readily allow the development of a single-chip wireless sensor, ChipSensors' current demos comprise a chip-based sensor and an off-chip wireless link communicating to a laptop PC that displays real-time measurements.

The technology could serve as an all-electronic replacement for electromechanical thermostats and humidistats. It may also prove effective for monitoring the behavior of processors and other complex chips, with the results fed back to help them control their own performance and power consumption.

ChipSensors is also developing an ultralow-power wireless version of the technology for incorporation into passive and active ID tags. So far, the startup has no products on the market. It expects to provide chip sensors without the radio or microcontroller integrated in the first quarter.

This story appeared in the EE Times Europe print edition covering September 17 - October 7. European residents who wish to receive regular copies of EE Times Europe, subscribe here.

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