Edinburgh-based Siemens’ spin-out Pyreos is to make pyroelectic detectors using standard semiconductor techniques.
“Current sensors are produced from a slurry of PZT [lead zirconate titanate] which is made into a ceramic, then polished back to 40-100[micro]m,” Pyreos CTO Carsten Giebeler told EW. “Then you have to cut the ceramic tile, pick and place onto a substrate, then bump it. This is not a very nice process.”
Pyreos’ alternative takes advantage of cheaper chip making techniques. “You can start with a six or eight inch wafer and get a PZT film by sputtering a few micrometres thick,” said Giebeler. “This is 40 times thinner than the standard process. Then you can pattern it using standard semiconductor processes.”
To work, the ceramic has to have an electric field locked within it. “Ours is permanently poled during the deposition process, no electric field is necessary,” said Giebeler.
Chip-like processing also allows the firm to produce pixelated sensors which, Pyreos CEO Jeff Wright told EW, are possible but uneconomical to make from bulk PZT. “You have to etch through hundreds of microns so it is impossibly slow as it is a tough material,” he said, adding: “You can pattern pixels on bulk material without cutting, but there is a lot of crosstalk between pixels.”
The firm is aiming its multi-pixel devices at fire and motion detectors. “A 4x4 detector separates a room into 16 segments and allows us to track people - to extract significantly more information and eventually reduce the false alarm rate,” said CTO Giebeler. “And we can get away from fly eye lenses and can now use plain Fresnel lenses.
The sensitivity of PZT devices improves with thickness, whereas imaging speed is better with a thin sensor. “Our sensitivity is about the same as bulk as what is lost by being thinner is gained by a better dipole,” said Wright.
Initial products will be 3x3 and 4x4 pixel arrays, although larger devices have been made during research.
Pyreos was set up in Scotland in July last year from Siemens Technology Accelerator in Germany. “There are good people, there is good infrastructure, and there is a good venture capital scene here at the Scottish Microelectronics Centre,” said Giebeler.
Last month, the firm attracted £2m from VC firm Braveheart in partnership with Siemens Technology Accelerator and the Scottish Venture Fund.