Low-volume custom designs add CMOS image sensors

CMOS image sensors are available as part of multiproject wafers.

IBM's CMOS image sensing technology is now available at low cost via the Mosis multiproject wafer service.

This means that companies working on imaging applications for everything from camera phones to high end digital cameras can access the technology at less than one-tenth the cost of using a dedicated wafer run.

They share wafers with other designs, paying only for the proportion of each wafer that they use.

The IBM CIMG7SF process uses 180nm technology to produce a four-transistor, 3.0um reference pixel.

It incorporates fully integrated colour filters and webbed microlenses for high quantum efficiency and wide viewing angles.

The surface area that is sensitive to light is maximised, allowing adjacent microlenses to overlap, and photodiode technology minimises dark current.

The process uses aluminium for the last metal layer and copper wiring for the remaining metal layers.

Thin back end-of-line metal stacks and good dielectric tolerance make the process suitable for most imaging requirements.

The Mosis MPW service is based on 8in wafers with a reticle size of 18 x 20mm.

Approximately 60 reticle copies are stepped on the wafer.

Typical turnaround time from release of the design to manufacturing is less than 60 days.

Mosis Deputy Director, Wes Hansford, comments: "The growth in demand for colour imaging continues to accelerate as it becomes more affordable in an ever-widening range of consumer electronic products".

"This new MPW service gives imaging system designers access to affordable prototyping and low volume production, minimising both their design risks and costs".

"Because they can often get evaluation samples into the hands of customers earlier using MPW, it can also shorten time to market, which is a crucial success factor for consumer devices".

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