Non-Dispersive Infra-red Gas Sensor

Cambridge CMOS Sensors (CCS) has identified a clear gap in the market of NDIRs and aims to address the
issues described above by using a lower cost, higher reliability proprietary technology. Thus, CCS has
invented and developed a technology that could replace the bulky, expensive and power-hungry IR sources
with significantly lower power miniature micro-hotplates (MHPs) that have the ability of reaching extreme
temperatures (in excess of 700°C). The MHPs are made using the standard microelectronics technology, the
Complementary Metal Oxide Semiconductor (CMOS) with a single Micro-Electro-Mechanical System
(MEMS) step to form thin dielectric membranes with embedded micro-heaters. The entire process is done at
a high volume commercial silicon foundry allowing very low cost and high volume manufacturing. The CMOS
MHP technology from CCS is unique and protected by 3 international patents. One more patent application
has been filed and one further application is currently with our patent attorneys.
CMOS Circuits
_s..~r---Oxide membrane
Backside ORIE/
Silicon
MHP@ sooc Cross-sectional view ot·patented MHP technology
Figure 2: MEMS Low Power IR Source
The exceptional high temperature and low cost capability of our MHPs makes this technology very attractive
for NDIR gas sensing applications. Figure 2, shows schematically the structure and scale of our MHPs
together with a photo showing the CCS MHP emitting in IR and visible domain at 800 oc. The diameter of
the MHP heater is only 200 microns. CCS has performed reliability and stability tests on the MHPs and have
proved that they operate reliably at 600 oc (for over 2 Million pulses with 2000h in an accelerated test).
Unlike, the conventional IR bulbs with tungsten wires as IR filaments, our heaters feature thin film, CMOS
based Tungstenrritanium layers embedded in a thin silicon dioxide to prevent the metal oxidation and avoid
possible explosion, (a common safety issue with current NDIR operating at very high temperatures).