Decisions, Decisions, Decisions…

Fifteen years ago fabless companies flourished because production became somewhat routine and foundries could provide more than adequate manufacturing capacity. Many IDMs also realized they no longer needed to invest in internally developed, proprietary technology. Marketing and product development was the way to gain market share. After reviewing the technology announcements and presentations from DAC and the VLSI Symposium over the past two weeks it hit me. Manufacturing is once again becoming a differentiator.

The ITRS (International Technology Roadmap for Semiconductors) has outlined a transition path for us that was adopted by a majority of manufacturers. Most advanced logic products use copper, and now high-k, metal gate. A majority of companies with advanced manufacturing capabilities have moved to immersion lithography. Many processes and materials had a way of becoming accepted as standard.

Moving into the next generation process technology, semiconductor manufacturers, both fabless and IDM, have to make a number of significant manufacturing decisions which could impact their product’s market applications and the ability to deliver timely, future products. The semiconductor manufacturing decision involves more than just a process node or cost of ownership. Manufacturing technology is becoming a major decision point with numerous options.

Two years ago TSMC came out with their 40nm node. What used to be a half node is now a sweet spot. Now we have fully developed processes at 45nm, 40nm, 32nm, soon 28nm and 22nm.
Which node do you use for your next design? Companies are even skipping a generation altogether. For their high performance product lines, Freescale went from 90nm directly to 45nm/40nm.

At 32nm/28nm do you go with gate-first or gate-last? Samsung claimed bragging rights as the first foundry with a qualified 32nm gate-first process. Proponents of gate-first believe it’s a simpler solution. Intel and TSMC are using gate-last or replacement metal gate. Intel started production on their 32nm replacement metal gate process last year. Proponents of gate-last plan on using the technology for future generations and believe that gate-first is a “one hit wonder”, good for only one generation.

Admittedly there has always been a difference between the SOI wafer proponents and the non-SOI users. The anti-SOI wafer camp continues to search for ways to avoid the use of SOI wafers. At the VLSI Symposium in June, Intel presented an update on their floating body cell technology. Their solution requires several steps to add an insulative BOX, only where necessary, hence the term localized SOI. Intel claims the result is a customized ultrathin SOI providing optimized back-gate and body doping. Why go through these extra steps instead of using an SOI wafer? Currently IBM’s R&D SOI process requires a step to thin existing SOI wafers. But SOITEC’s roadmap does include a 10-20nm ultrathin wafer expected to be available for 22nm production and beyond.

Certainly, there is always more than one way to solve a problem. But can the industry afford to run so many different processes? Will we find that one process truly is better than the other? Two years ago I didn’t think it was feasible for TSMC to buck the trend with their 40nm process. Nonetheless, they are a leader and when they rolled out 40nm, other foundries felt they had to follow.

Semiconductor manufacturers have encountered many decision points when it comes to technology options. In the past, companies would eventually converge onto similar paths in terms of materials and processes because the best solution had a way of rising to the top. At a time when the industry is under pressure to reduce costs and time-to-market we seem to be driving ourselves to more complex and diverse ways to reach the same goal. Choosing your foundry partner involves a lot more than just wafer price. Could the selection of a particular process technology actually make or break a product line? It appears we are following the advice of Yogi Berra: When you get to a fork in the road, take it.

Joanne Itow,
Managing Director