I am trying to understand if digital ASICs with tens of millions of silicon-germanium gates exist. A comment in another post states (emphasis mine) "SiGe can hit 5 GHz pretty easily even with half a billion gates"—I am trying to confirm or refute this statement.
Below is how I understand things. SiGe (for example, SiGe 9HP from Global Foundries) is a BiCMOS process which integrates two separate technologies. It contains a "cost-effective mature silicon base" which is the 90 nm Si process. On top of this base, it allows for the use of SiGe NPN transistors with "exceptional high-frequency performance".
Looking at the applications of the SiGe 9HP process, it seems these NPN transistors are used for analogue purposes, e.g. for LIDAR, RADAR, 5G, Ethernet, etc. I have not found applications using NPN transistors to build large scale digital logic. A leading SiGe researcher has a list of "selected SiGe circuits" (see right column) and none seems to be large scale digital circuits.
As a side note, I found SiGe used in the context of strained silicon, but as I understand strained silicon is just Si CMOS.
My questions regarding the SiGe process are:
- Are SiGe NPN transistors used to build digital gates?
- Can digital ASICs be built from tens of millions of SiGe gates?
- If the answer to 2) is "yes", are there public examples?
- If the answer of 2) is "no", why not (e.g. size, power, yield, ...)?