The era of Moore's law winding down, says Broadcom's CTO

In an on-stage interview at an event celebrating the 40^th anniversary of Ethernet, Broadcom's chief technology officer Henry Samueli viewed the semiconductor industry's party nearing its end. Samueli also believed that the industry has to work out its plans for 3D chip stacks.

"Moore's Law is coming to an end—in the next decade it will pretty much come to an end so we have 15 years or so," Samueli told several dozen Silicon Valley technology veterans. "Standard CMOS silicon transistors will stop scaling around 5 nm and everything will plateau," he said.

"I am comfortable we will get to terabit networking speeds, but I'm not sure I see a path to petabit speeds," said the co-founder of one of the world's largest communications chip companies. "You will see density of network switch boards leveling off and when you see the network progress level off it will change the dynamics of the entire industry," he said.

"We still have another 15 years or so to enjoy, but we need to prepare at some point for a network that doesn't double in bandwidth every two years," he added.

Figure 1: Samueli spoke out on a panel with execs from Arista, Brocade and HP.

Plenty of pundits have predicted the end of CMOS scaling before, but rarely veteran executives of well-established chip vendors with deep technical understanding. Before co-founding Broadcom in 1991, Samueli was a professor of electrical engineering at UCLA, specialising in communications chips.

The end of CMOS scaling "has been one of my biggest concerns for some time," Samueli told EE Times after participating in a panel discussion. "We've been talking to customers about this for a while," he said.

Samueli said he has briefed customers that prices for leading edge chips will increase, starting with the 20nm generation due to rising fabrication costs. Market watcher Gartner Inc. recently estimated the average 45,000 wafer/month fab could pay a premium of about $500 million per process node due to the need to use two or more lithographic exposures to etch finer lines.

Stacking chips into so-called 3D ICs promises a one-time boost in their capabilities, "but it's expensive," said Samueli. Broadcom expects to use 3D stacks to add a layer of silicon photonics interconnects to its high end switch chips, probably starting in 2015 or later, he said.

"We are talking with potential [3D IC] partners, but we don't have it all sorted out yet," he said.

Another industry veteran and EE on a panel with Samueli took issue with the Broadcom exec's predictions. "The real situation is we have 10-15 years visibility and beyond that we just don't know how we will solve [the problems of CMOS scaling] yet," said Dave House, chairman of switch maker Brocade and a veteran of 23 years at Intel.

At Intel, House interacted regularly with Intel co-founder Gordon Moore who articulated the theory that roughly every two years chip makers would be able to double the number of transistors on a CMOS chip.

"In the 1970s I started preaching Moore's Law will solve all our problems, and Gordon stopped me and said, 'Ten years out, I don't think it can continue,'" House said. "Ten years later, Gordon said again, 'I only see about ten years here.'

"It became a regular thing at Intel strategic meetings where Gordon would say beyond ten years I don't see it continuing," said House who is also an EE by training. "As time went on there was always enough money spent and smart scientists" to solve CMOS scaling issues, he said.

"It could be we will have a firm barrier [at 5nm], but I wouldn't bet on it [because] the consequences will be so severe" he added.

In conversation after the event, Bob Metcalfe, one of the original inventors of Ethernet and the keynoter of the event shared his thoughts with Samueli and others.

"One of the big things I learned today is Moore's Law is related to the elasticity of bandwidth—it not only creates the machines that need more bandwidth, it also creates the machines that provide that bandwidth," he told Samueli. "If you are right and Moore's Law ends, so will this bandwidth elasticity," Metcalfe said.

- Rick Merritt
??EE Times