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Backside processing is standard in the CMOS image sensor industry. Turns out all the metal on the front-side makes it very difficult to get light down to the si

Backside processing is standard in the CMOS image sensor industry. Turns out all the metal on the front-side makes it very difficult to get light down to the silicon where the actual photon-electron transduction takes place. Backside imagine (BSI) has been standard for quite a few years. Wafer thinning is used extensively in stacked-die products which have become common in recent years. This looks like an incremental change applying the tech from image sensor/memory technology to standard silicon. Although, I'm not sure why they chose ruthenium.

philipkglass 7y ago
Copper has long been popular for metallization, but it is running into problems at finer linewidths. Cobalt and ruthenium are two popular alternatives being researched. I don't follow the industry closely enough to know if anyone is using them in volume manufacturing yet. "Imec Presents Copper, Cobalt and Ruthenium Interconnect Results" https://semiwiki.com/semiconductor-services/ic-knowledge/7569-iitc-imec-presents-copper-cobalt-and-ruthenium-interconnect-results/ https://semiwiki.com/semiconductor-services/ic-knowledge/756... Cobalt needs a barrier to prevent mixing under some circumstances where it contacts copper. Ruthenium doesn't need any barriers but chemical mechanical polishing (CMP) processes for it still have problems.
hristov 7y ago
BSI is very simple compared to what they are proposing here. BSI illumination does not require that any features are actually built into the backside. It basically just requires that the backside be polished very nicely. Here we are talking about building elements on the backside and then connecting them to the front side. It is much trickier.
- satya71 7y ago
  That's not entirely true. BSI always had some metallization on the backside for aperture, power and packaging. For example, see this: https://image-sensors-world.blogspot.com/2018/03/techinsights-publishes-samsung-09um.html https://image-sensors-world.blogspot.com/2018/03/techinsight... Perhaps what they're proposing is more sophisticated, but definitely not something entirely new.

philipkglass 7y ago

Copper has long been popular for metallization, but it is running into problems at finer linewidths. Cobalt and ruthenium are two popular alternatives being researched. I don't follow the industry closely enough to know if anyone is using them in volume manufacturing yet. "Imec Presents Copper, Cobalt and Ruthenium Interconnect Results" https://semiwiki.com/semiconductor-services/ic-knowledge/7569-iitc-imec-presents-copper-cobalt-and-ruthenium-interconnect-results/ https://semiwiki.com/semiconductor-services/ic-knowledge/756... Cobalt needs a barrier to prevent mixing under some circumstances where it contacts copper. Ruthenium doesn't need any barriers but chemical mechanical polishing (CMP) processes for it still have problems.

hristov 7y ago

BSI is very simple compared to what they are proposing here. BSI illumination does not require that any features are actually built into the backside. It basically just requires that the backside be polished very nicely. Here we are talking about building elements on the backside and then connecting them to the front side. It is much trickier.

satya71 7y ago
That's not entirely true. BSI always had some metallization on the backside for aperture, power and packaging. For example, see this: https://image-sensors-world.blogspot.com/2018/03/techinsights-publishes-samsung-09um.html https://image-sensors-world.blogspot.com/2018/03/techinsight... Perhaps what they're proposing is more sophisticated, but definitely not something entirely new.