First it was AMD which licensed the capacitor-less DRAM memory, known as ZRAM, in 2005. AMD wanted to use ZRAM to add memory to microprocessors with less usage of silicon than that taken by a conventional DRAM based on a transistor + capacitor cell structure.
Then Renesas announced, also in 2005, that it had developed a similar, capacitor-less DRAM structure. Renesas wanted the technology, which it calls TTRAM (twin transistor RAM), to add memory to its SOCs which would take up the minimum possible amount of silicon area.
Now Hynix has licensed ZRAM, and this time it’s not for embedded applications but for for discrete, standalone memories. Moreover Hynix says that the deal by which it has licesned ZRAM technology precludes any more licenses being sold for three years.
Whereas the ZRAM being used by AMD was said to provide allow an embedded memory five times denser than the conventional six transistor SRAM, the new version of ZRAM, licensed to Hynix, permits a memory which is twice as dense as conventional DRAM.
According to Sung-Joo Hong, v-p of R&D at Hynix, the company is putting in significant resources to develop standalone ZRAM memory.
“ZRAM promises to provide an elegant approach to manufacture dense DRAMs on nanometre processes,” says Hong.
Hynix, like AMD, has licensed the technology from its developer, a company called Innovative Silicon (ISi).
“Embedded memory technology is becoming the dominant factor affecting the cost of leading edge SOCs and microprocessors today,” says Mark-Eric Jones, CEO of ISi, adding, “memory chips built using ISi’s Z-RAM technology will be much smaller and cheaper to manufacture.”
ZRAM was first developed in 2002 in Switzerland by two scientists working at the Swiss Federal Institute of Technology of Lausanne (EPFL).
One of them, Dr Pierre Fazan, had previously worked at Micron Technology of Idaho; the other, Dr Sergei Okhonin previously worked at the Institute of Semiconductor Physics at Novosibirsk, Russia.
The technology uses the floating body effects of SOI, a parasitic or unwanted effect that leads to current leakage in typical SOI applications, as a switch, doing away with the need for a capacitor in a DRAM cell.
In 2002, Fazan and Okhonin founded Isi. In 2004, ISi raised $6m in a first funding round backed by Index Ventures, Auriga Partners, Highland Capital and Soitec. In 2005, it raised a further $16m from the same backers plus Austin Ventures.
ISi taped out its first 60nm 1Mbit 90nm ZRAM memory in 2004 and completed its first 65nm in July 2005.
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