Archive for December, 2009

Merry Christmas and Happy New Year

Friday, December 25th, 2009

At the end of the 2009 I would like to take the opportunity to wish all my readers a Merry Christmas and a Happy New Year. 

Everyone is telling that the economy is recovering, let’s hope that this will be the driver for a successful 2010.  I heard from various industrial sources that CCD fabs as well as CMOS fabs are completely filled with image sensor wafers.  Apparently the future for imaging looks bright.

Looking back to 2009, it was a difficult year for many of us in the imaging business.  If I look to my own activities, 2009 started with a drastic reduction in attendees of the ISSCC2009.  If I recall the numbers, the amount of participants was about 66 % of the previous years.  Being the vice chair of the technical program committee, I was reponsible for the evening and educational activities.  Also within the ISSCC organization ”cost-cutting” became a buzz-word.    As far as my own teaching activities were concerned, in the first half of 2009 the number of in-house trainings dropped, and several public courses had to be cancelled because of lack of participants.  Despite all the negative signals, the International Image Sensor Workshop in June was a big success.  Being the general chair of the workshop, I was very much concerned about the financial consequences if we had to face a low number of papers and/or participants.  But the workshop was sold out in just a few days, Johannes Solhusvik helped me putting together a very strong technical program, and we combined the workshop with a one-day symposium on BSI which attracted a lot of attention. 

After the Summer holidays, the teaching and training activities started to recover.  New in-house courses were organized, and in the Fall of 2009 only one public course needed to be cancelled.  The drop in number of courses in the middle of the year gave me the time to work on other items, and the result of that will be a brand new course in 2010.  Although I am still working on it, the course will become available in the second half of 2010.  It will be the first course ever in digital imaging with hands-on evaluations and measurements in the class room.  New hardware is acquired (11 cameras, light boxes, power supplies, laptops, etc.) and at this moment I am preparing the exercises for the course.  The first four experiments are ready : illustrating the improvement in S/N when multiple images are averaged, measuring the fixed-pattern in dark (pixel, column and row FPN), measuring the temporal noise in dark and measuring the pixels with random-telegraph pattern (RTS pixels).  More assignments will follow.  It is a lot of work, but it is also a lot of fun to prepare the set-ups.  I am really looking forward to work with it in a class room.  So 2010 will bring its own challenges, but it so much more motivating to work on these positive challenges to expand and improve my own business.

I wish all of you the very best for 2010, and hope that we will regularly “meet” through this blog.  Thanks for visiting the website of Harvest Imaging !

Albert, 24-12-2009.

Highlights CMOS Detector Workshop Toulouse 8-9 December 2009

Thursday, December 10th, 2009

In this short blog I would like to report on (what were for me !!) the highlights of the workshop entitled : “CMOS Detectors for High Performance Applications”, organized by Alex Materne (CNES), Oliver Saint-Pe (Astrium) and Christophe Renard (Thales Alenia Space).  Unfortunately I could not attend all presentations, so there might have been more important things presented than just shown over here.  Sorry to the presenters that I missed.

-          P. Robert (ULIS) explained how to increase the dynamic range of infra-red imagers by implementing extra capacitance in the column circuitry,

-          B. Dupont (Caeleste) showed a hybrid photon counting sensor based on SPADs,

-          B. Fowler (Fairchild Imaging) had another talk about their 5.5 Mpixel low-noise sensor.  New to me was the availability of the colour version of this sensor, as well as the back-side thinned version.  The combination of colour and back-side illumination will not be offered.  In the same talk a rad-hardness of 30 Mrad was mentioned.  Seems extremely high to me, but then the discussion popped up how the rad-hardness is defined ?  No data was given about the performance of the device in global shutter mode.  We have to wait till the upcoming SPIE conference in January 2010.

-          T. Baechler (CSEM) presented their work on in-pixel amplification with p-type transistors configured as a regulated cascade in the columns.  Cleaver idea, but at this moment no measurements are available.  An interesting model was presented to show the importance of the dark current if single photon detection is needed.

-          G. Lepage (CMOSIS) talked about the TDI option in CMOS, and how his project evolved from an analogue storage towards a digital storage on-chip for the intermediate data of the TDI.

-          J. Bosiers (DALSA) showed that a front-side illuminated CMOS imager can be light sensitive till 250 nm, at least if the appropriate measures are taken in the technology,

-          J. Pratlong (E2V) presented a large pinned (?) photodiode of 24 um x 24 um with the readout circuitry nicely placed in the middle of the diode.  Unfortunately no real details of the lay-out were shown, it would be of great interest to see how  a large conversion gain (90 uV/e-) can be obtained by such a structure.  Image lag of 5 electrons are reported, this seems a very good value for such a large pixel.

-          B. Cremers (Cypress) reported about an imager with a partially pinned photodiode.  Interesting to notice is the fact that the author talked about a couple of artifacts of the devices.  This is not that often the case that companies report about issues.

-          A. Peizerat (CEA) gave an interesting overview of requirements and options for ADCs in CMOS image sensors (die-level, column-level and pixel-level).

-          I. Djite (ISAE) talked about MTF simulation and showed his simulation results together with measurements.

-          S. Demiguel (SAGEM) focused on back-side illumination of CMOS imagers for low-light level, but the major part of his presentation was on a very nice overview of low-light level imaging options (tubes, EM, intensified, back-side illumination, other materials).

-          P. Jerram (E2V) talked about 2 CMOS imagers that are back-side illuminated.  Very nice talk with a lot of information on the BSI process itself. 

-          J. Bosiers (DALSA) highlighted their large CMOS tile of 77 mm x 145 mm, 3 sides buttable and intended for X-ray applications.  During the talk, the BSI process of DALSA was described as well, based on back-side charging to passivate the back-side of the thinned sensors.

-          P. Cemeli (Soitec) explained the back-side process in the case the starting material is SOI.  Quite a bit of technology information was given and actually this talk together with the one from P. Jerram gave an excellent overview of the ins and outs of BSI on bulk silicon and on SOI.

-          B. Dryer (E2V) presented first results on radiation damage introduced in 0.18um CMOS imagers.  Nice results but more experiments will follow.

-          Round table discussion : a panel of 8 people discussed the issues of getting access to CIS foundries for small volumes and/or for process changes.  It was concluded that process changes are out of the question (except for some small changes in implantation dose) and that the scientific/space community is that much fragmented that higher volumes can never be reached.  The only option left is to search for a common ground to increase the volumes.  This can be done by putting all roadmaps of all agencies on the table and focus on a common interest for all devices.  Otherwise the situation will not change …. and in times that the fabs are filled, the situation can only get worse.

Conclusion : interesting workshop, no registration fee, small group of people (100), good atmosphere, open discussions, no proceedings.  Thanks to the organizers !

Albert, 10-12-2009.

Image Sensors in Brazil

Tuesday, December 1st, 2009

 

During the last two weeks I was not able to spend enough time preparing a new technical blog about the continuing story of the PTC.  The reason is very simple : a trip to Brazil kept me busy.

I was invited by prof. Jose Gabriel Rodriguez Carneiro Gomes (Universidade Federal do Rio de Janeiro, UFRJ) and prof. Davies William de Lima Monteiro (Universidade Federal de Minas Gerais, UFMG) to give a talk in order to promote solid-state imaging technology in Brazil.  The workshops were organized in close cooperation with the local IEEE Chapter on Circuits & Systems. 

At this moment the overall semiconductor activities in Brazil are continuously growing, but there is still very limited work going on in the field of imagers.  A few start-up companies are doing quite nice work, but they do not (yet) reach the level of the companies present in North America, Europe or the Far East.  So it was a great initiative of prof. Gomes and prof. de Lima Monteiro to promote image sensors in front of an audience composed out of undergraduate students, graduate students, professors and people from industry.  If the R&D work on image sensors gets more attention, it will be easier to get funding from the government for future projects.  And this holds for academic work as well as for industrial activities.

My talk was split into two parts (each part lasted for 2 hours) :

-       “CMOS Image Sensors : Past, Present and Future”.  The content of this session was based a short historical background, a brief overview of the state-of-the-art and focused mainly on future challenges of CMOS imaging.  If pixels get smaller and/or if more pixels are put on a sensor, the overall speed of the sensor will go down (in frames/s), the dynamic range will lower, the light sensitivity will decrease, and ultimately the signal-to-noise will deteriorate.  The talk gave an overview of the few techniques that can be used to increase the speed, to create a wide dynamic range, to increase the light sensitivity (by means of back-side illumination) and to optimize the signal-to-noise ratio (by means of pixel binning),

-       “Colour Processing”.  In a talk of 2 hours it is pretty difficult to give a detailed overview of the complete signal processing present in a digital camera.  For that reason the content of the presentation was limited to the following subjects : short overview of colour imaging, auto-white balance, colour matrixing and demosaicing.

Other speakers in the workshop were Simon Schneiter (talked about 3D Imaging) and Carlos Mendoza (talked about Smart Vision Systems).  Each workshop was attended by about 100 participants.  Based on the reaction after the workshops, the talks were very well received by the audience.  Hopefully the participants were convinced that imaging in general is a great field to work in.  If so, then more students might be attracted by the subject of solid-state imaging, and it can be a great stimulation to submit more projects.  In the end more projects will be granted, and that was the original goal of the bringing all these people together.

My first visit to Brazil was possible thanks to this great initiative taken by prof. Gomes and prof. de Lima Monteiro.  Thanks to them for inviting me this opportunity to promote digital imaging and congratulation for the perfect organization of the workshops !

Albert 01-12-2009.