LONDON ChipSensors Ltd. (Limerick, Ireland), a fabless chip company started in 2006, has developed a technology that allows the surface of an IC to be used to sense temperature, humidity, certain gases and pathogens, the company has claimed.
The patent-pending technology makes use of the low-k dielectric material used in standard sub-micron CMOS process technology as an insulator between metal interconnect. That material is porous, and by selectively admitting or blocking ingress of the agent to be sensed, the dielectric constant of the material can be changed, forming a capacitive sensor.
Normally the surface of an IC is passivated to prevent ambient conditions affecting it. Similarly the pores of low-k material are often surface treated. However ChipSensors indicated that by letting ambient conditions affect a prepared area the resulting electrical characteristics can be detected and measured accurately using on-chip circuitry.
The technology also allows the development of a single-chip wireless sensor using wireless circuitry on the same chip to transmit measurements. At present the company has a chip-based sensor and an off-chip wireless link communicating to a laptop PC displaying real-time measurements.
The ingress of moisture is usually considered detrimental to the long-term reliability of an IC. ChipSensors did not discuss whether steps are required in packaging to prevent ambient effects until the moment of use, or what sort of useful life it expects for its sensors.
The company has a demonstrator IC fabricated in a 130-nm CMOS process, and states that the technology could be used as an all-electronic replacement for electromechanical thermostats and humidistats used in building management and environmental monitoring systems. ChipSensors is also currently developing an ultra-low-power wireless version of this sensor - which integrates all the signal conditioning, microcontroller, memory and RF transceiver functions onto the same chip as the sensor itself - for incorporation into passive and active ID tags.