Report on Image Sensors Europe 2012 (2)

Valerie Nguyen (CEA-LETI) opened the show on Wednesday morning.  According to Valerie, the market trend in imaging will be : “Pixels Everywhere”.  If solid-state imaging is going to be used for creating and generating nice images, then the trend will be MORE PIXELS.  But if solid-state imaging is going to be used for control purposes, then the trend will be MORE THAN PIXELS.  Based on existing marketing reports, the year 2009 has delivered 2 M image-sensor wafers with a growth rate of 11 %, and the prediction is that we will get 4 Mwafers in 2015, still with a growth rate of 15 %.  So on the short term, the growth in imaging business is for sure not coming to an end.  But one should realize that in the last 10 years the volume for VGA sensors (as an example) is grown by a factor of 100, but the price went down by a factor of 25 !  A consumer does get more silicon for less money, the manufacturer do get less money for more silicon.

Valerie gave a very nice overview of the imaging activities in the eYe valley around Grenoble.  Apparently a lot of companies in that area are active in solid-state imaging.  She also illustrated what CEA-LETI can do for the imaging industry, such as : thinner BEOL, lightpipes, inner lenses, BSI, colour filter with IR cut-off included, nanoprint for micro-lenses, TSV, etc.  Apparently Grenoble is the place to be for sensor innovations (and maybe also for skiing ?).

Valerie concluded with some statements about the combination of several imaging techniques in one device.  For example micro-bolometers in combination with a visible sensor, or InGaAs underneath Si.  In this way a fusion can be realized between several imaging methods/techniques.  The fusion idea of putting several imaging methods and techniques into one device was mentioned a couple of times by different speakers.

Next was Mats Wernersson (Sony) who convinced the audience that “Mother nature is a bitch”.  He focused on the system aspects of future mobile imaging, and clearly proved that one has to think on system level if one tries to improve the sensor performance.  For instance, low light performance is much more than just sensor sensitivity !  Even if you can count single photons, it is not possible to make nice images with a single photon, but it takes a billion of photons.  Another nice example of the impact on system level of improving the sensor : BSI does allow the use of faster lenses.  So the combination of higher light sensitivity and the possibility of a lower F number is the real benefit of BSI, and this combination is much larger than just the light sensivity increase of the sensor.  Very nice talk with the typical dry humor of Mats.   

Gennadiy Agranov (Aptina) talked about pixel developments.  It is not really new that the industry is going to smaller pixels, but the main challenge is of course to keep up the performance of these tiny small pixels.  Gennadiy showed a lot of interesting data about performance of the devices, for instance QE and dark current of various generations of sensors.  Also worthwhile to mention is the work of Aptina on global shutter CMOS devices.  Over the years they improved the in-pixel storage concept and went from a device with 40 electrons of noise and a QE of 40 % in 2000, to a device with 1.5 electrons of noise and a QE of 85 % three generations later in 2012.  These numbers hold for global shutter devices.  The latter device has a shutter efficiency of 99.96 % (comes close to the transport efficiency of CCDs : 99.99995 %).

In the last part of his presentation, Gennadiy showed the first results about a CMOS device intended for stereo vision.  A single image sensor is used for 3D, based on a pixel with an asymmetric angular response.  Very interesting idea !

Albert, 22-03-2012.

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