DSLR Image Sensor Innovation – Who Is Challenging Canon and Nikon’s lead?
After discussing leading-edge logic processes in the last few weeks, I think it’s time to take a line from the Monty Python cult TV show: “And now, for something completely different.” (It’s hard to believe that show was 40 years ago — it’s still in re-runs!)
My colleague Ray Fontaine has crafted a thoughtful piece about digital SLR cameras, one of the fast growing sectors in the competitive consumer arena. It’s obvious from the continuous stream of new models that there is steady innovation in this field, and Ray has detailed some of them for us.
DSLR Image Sensor Innovation — Who Is Challenging Canon and Nikon’s lead?
By Ray Fontaine, Image Sensor Sector Analyst
Canon and Nikon have long been the twin DSLR giants. A 2008 BCN Japan review showed each to have a 39% market share of the Japanese DSLR market (Figure 1). These numbers would naturally fluctuate for worldwide DSLR sales, but certainly Canon and Nikon are dominant.
Fig. 1: 2008 Japanese DSLR Market Share (from BCN Japan/SlashGear) [1]
It is not hard for Canon or Nikon to predict encroachment on its market space by other camera makers. The segment that seems to offer the most growth potential is enthusiast/semi-pro grade class DSLRs with HD video functionality. In what areas are the challengers being innovative to give them competitive performance and feature sets? We’ve analyzed the image sensors from the recent Pentax K-7 and Panasonic DMC-GH1 and compared them to their respective predecessors. In both cases, we’ve found significant innovation in the image sensor fabrication processes and the sensor design.
The Pentax K-7 replaces the K20D and features 720p HD movie functionality [3]. The first generation Samsung sensor from the K20D was itself full of firsts. The Samsung S5K1N1FX (K20D) was the first DSLR CIS we found to use copper metallization in the back end of line (BEOL). Figure 2a shows cavities that were etched into the pixel BEOL, and subsequently filled with an organic spin-on planarizing film. This was a trick borrowed from Samsung’s small pixel development first observed by Chipworks in their 1.75 µm generation pixels. The 5.0 µm pitched pixels used by the K20D and K-7 also feature an oxide cap over the organic microlenses. In addition, we also discovered pitch-matched metal-insulator-metal (MIM) capacitors in the column circuits. Figure 2b shows the MIM capacitors from the S5K1N1FA (K-7).
Additional innovation in the K-7 CIS are change in packaging, major re-engineering of the wells and substrate, a modified pixel poly and metal layout, and the addition of a VSS contact to each pixel for a reduction in color cross-talk.
Fig 2a (left): Samsung CIS Pixel BEOL; Fig. 2b: MIM Capacitors
The Panasonic DMC-G1 was a noteworthy release, as it was the first in the Micro Four Thirds system, a “mirrorless DSLR format” created by Olympus and Panasonic. The aluminum BEOL used by the DMC-G1 pixels is shown in Figure 3a. The major knock on that first release was the absence of HD video functionality, a feature added for the second generation DMC-GH1. Upon receiving the DMC-GH1, we fully expected to see a fabrication process similar to the DMC-G1, but partnered with a new design to add HD video functionality. While still early in our analysis, we have been pleasantly surprised to see Panasonic switch fabs and radically re-design their fabrication process and pixel architecture. Figure 3b shows the four metal (one aluminum, three copper) BEOL used by the DMC-GH1. Additionally, Panasonic has moved away from their traditional LiveMOS architecture, which previously allowed them to implement their pixel wiring in a two metal BEOL process.
Fig. 3a (left): Panasonic First Gen. CIS (Al BEOL); Fig. 3b: Second Gen. CIS (Al/Cu BEOL)
Clearly, the competition is on the move, so what about the bellwethers? We don’t have the most recent data points from Canon or Nikon in this class of DSLR, but Nikon has certainly brought innovation to its DSLRs simply by designing its own sensors instead of outsourcing to Sony.
Canon seems to follow the “if it’s not broken, don’t fix it” philosophy by using essentially the same fabrication process on 2 generations of DSLR sensors — generations that were 3 years apart. Despite a modest evolution in pixel architecture, to date Canon’s pixel fabrication seems to be locked down, and we suspect Canon is getting significant performance gains from its Digic line of image processors.
In summary, we are seeing quite a lot of process innovation in reasonably priced DSLRs with HD functionality. This class of cameras is sure to be popular with consumers, and we fully expect to see innovation from the leaders as they are forced to defend their positions. For additional images visit Chipworks’ blog.
Related Chipworks Reports
Panasonic DMC-G1: IPR-0812-801
Panasonic DMC-GH1: IPR-0909-801
References
[1] http://www.slashgear.com/two-big-continue-to-stomp-digital-slr-market-in-japan-3128291/
[2] http://www.photographyblog.com/news/cipa_predicts_falling_camera_sales_in_2009/
[3] http://www.dpreview.com/reviews/specs/Pentax/pentax_k7.asp
[4] http://www.dpreview.com/reviews/specs/Panasonic/panasonic_dmcgh1.asp
[5] “Nikon 12.1 Mp CMOS Image Sensor from a D3 DSLR Camera with NC81338L Die Markings,” Chipworks, IPR-0710-801
[6] “Canon EOS 5D (706P) 12.8 Megapixel CMOS Image Sensor,” Chipworks, IPR-0511-802
[7] “Canon 1100 21.1 Mp, 6.4 µm Pixel Size Full Frame CMOS Image Sensor from the Canon EOS 5D Mark II Camera,” Chipworks, IPR-0811-801
