One of the most consistent features of the long development path of EUV lithography from research towards manufacturing has been delay, especially when it comes to meeting source power and throughput milestones. Source power roadmaps have always resembled the classic marketing hockey stick graph: progress may be slow now, but it is about to take off! When questions arose about whether such dramatic improvements (always scheduled for next year) were reasonable, we began to see the roadmaps shown on a semi-logarithmic scale. Past progress now seems steeper; future requirements look less dramatic.

Last year ASML took a different tact, eschewing source power as a metric of progress towards the goal EUV manufacturing and instead focusing on tool throughput. After all, it is throughput that matters. And of course this is correct, but the change in units makes comparison of current performance to past predictions just that much more difficult. No longer is a 100 W source promised for the end of the year; instead we’ll have a throughput 70 wafers per hour by the end of 2014 and 125 wph in 2015.

At the end of 2013 these goals, 70 wph in 2014 and 125 wph in 2015, were still the official line at ASML. But now we have another unit change. Today, current performance of the EUV production tool, the NXE:3300, is described as 100 wafers per day, and the new goal is to reach 500 wafers per day by the end of 2014.

What’s going on here? When I hear a throughput spec for a manufacturing tool quoted in wafers per hour, I expect that tool to be able to operate for more than one hour. I expect it to operate all day. Sure, tool availability will always be less than 100%, and it is very important to know what that tool availability is. In that sense, wafers per day actually is a better metric to judge manufacturing readiness (or maybe it should be wafers per week). But let’s do the math here. A throughput of 500 wafers per day is an average of 21 wafers per hour. That’s a far cry from the 70 wph promised just a few months ago. In fact, 70 wph translates to 500 wafers per day if you assume only 30% availability for the tool. That’s low even by EUV standards.

So what has ASML done? They have delayed their roadmap. And to make the delay less obvious, they have changed the units. There will be much weaseling, no doubt. Was the promise of 70 wph really a promise to demonstrate the “capability” of 70 wph by the end of 2014? What does it mean to demonstrate the capability of a given throughput number anyway?

Ultimately, ASML must demonstrate the practical use of their tools in manufacturing at a throughput that lowers the cost per die compared to alternate lithography approaches, such as double or triple patterning. No hiding behind unit changes or ambiguous phrases can help them there. But between now and then the semiconductor manufacturers must maintain sufficient faith that ASML will meet that goal and do so on a schedule that enables planning of future fabs and future processes. And it is this faith that ASML is desperate to keep in place.