Cliff Hirsch, Publisher, Semiconductor Times

An inside look at innovative semiconductor start-ups

Not surprisingly, the past quarter hasn’t been the most stellar for semiconductor start-ups. Many have folded, and new investment dollars have been scarce. Most entrepreneurs would blame the market and venture capital community. Most investors would blame the capital intensity of the fabless semiconductor start-up business model and lack of return on investment (ROI). I see bits of truth on both sides. However, putting on my investor/shareholder hat, business is business—the goal is to make money, and poor performance is not rewarded.

Taking a softer stance, the low-hanging fruit is long gone; the semiconductor business has become big business. The classic digital system-on-chip (SOC) start-up model is stressed, to say the least. In fact, for the past few months, I have been exploring the viability of the virtual application-specific standard product (ASSP) business model, based on intellectual property (IP) combined with field-programmable gate arrays (FPGAs) and perhaps the next logical step in the shift from integrated device manufacturing (IDM) to fabless and then to chipless.

However, semiconductor innovation still thrives, even if it is the result of an accidental discovery, as is the case with SiOnyx, which was founded in 2006 to commercialize shallow junction photonics, a patented semiconductor process coined “black silicon” by researchers at Harvard University who first discovered the phenomenon. SiOnyx has secured $13.2 million from Harris & Harris, Polaris Venture Partners, RedShift Ventures and private investors.

The most common material used in photonic systems is silicon. While silicon makes an excellent visible light detector, it is useless in detecting other wavelengths commonly found in nature. Exotic materials, such as indium gallium arsenide, lead and cadmium, have been used to overcome this limitation of silicon; however, they are expensive and toxic.

SiOnyx is focused on commercializing the unique optoelectronic properties of pulsed laser modified semiconductors for imaging, power generation and low-light detection applications. Black silicon is created by shining a series of very short, very intense laser pulses at a silicon surface in a chamber filled with gas such as sulfur hexafluoride or chlorine. The SiOnyx implant method is compatible with established semiconductor manufacturing processes and introduces no new material.

In the presence of the laser light, the gas reacts with the silicon surface, leaving a pattern of conical spikes. SiOnyx first thought that the spiked silicon surface was responsible for the characteristics it observed. However, further research revealed that shallow junction photonics was the phenomenon responsible for the remarkable performance.

Shallow junction photonics is a patented semiconductor process that exploits unique atomic-level alterations that occur in materials irradiated by high-intensity lasers. Crystalline materials subject to these intense, localized energy events undergo a transformative change without any thermal interaction; the atomic structure becomes instantaneously disordered, and new compounds are “locked in” as the substrate re-crystallizes.

When applied to silicon, the result is a highly doped, optically opaque shallow junction interface that is thousands of times more sensitive to light than conventional semiconductor materials.

The unique atomic configuration established in the SiOnyx process produces a thin-film, broad spectrum detector that delivers astonishingly high response in comparison to typical semiconductor devices. Black silicon is 100 times more sensitive to light than silicon, detects energy from ultraviolet (UV) to short-wave infrared (SWIR), operates at a low-voltage bias, is extremely thin (>0.50μm), and is compatible with existing CMOS process flows.

Higher sensitivity means better resolution at low-light levels for everything from scientific instrumentation to radiological imaging and laser ranging/tracking. Broader spectral response will make SiOnyx’s shallow junction photonics the technology of choice for laser detection in the infrared waveband.

For image sensors, shallow junction photonics technology enables 1μm² pixels that produce more signal than 36μm² traditional silicon pixels, while capturing photons within a thin half-micron layer, solving crosstalk and red/infrared sensitivity issues.

SiOnyx detectors, operating at bias voltages as low as 3.3V, outperform the industry’s best avalanche photodiodes (APDs). Shallow junction photonics promotes the integration of detectors with other circuitry and holds the promise of ultra thin-film solar cells with a fraction of the required silicon bulk material.

Applications range from simple light detectors to advanced medical imaging systems. Samples of initial devices, most likely simple photodetectors, are planned for late 2009. Initial target markets are medical imaging and other high-value markets. SiOnyx is currently engaging with industry partners.

That’s a reasonably interesting and compelling story. One could probably dedicate a small army of doctorates to researching and developing technology equivalent to SiOnyx's. Yet, in this case, innovation is the result of an accidental discovery, which saves a lot of cash and time. Now that SiOnyx has made these discoveries, the technology appears to be extremely promising and can be applied to a myriad of applications and markets to deliver devices with vastly superior performance.

Cliff Hirsch (cliff@pinestream.com) is the publisher of Semiconductor Times, an industry newsletter focusing on semiconductor start-ups and their latest technology. For information on this publication, visit www.pinestream.com.