…economics of lithography slow scaling.
Moore’s Law had been on life support ever since the industry started needing Double-Patterning (DP) at 1/4-pitch of 193nm optical lithography. EUV lithography shows slow and steady progress in source and resist technologies, and ASML folks tell me that they now have a pellicle to protect the reflective masks, yet it remains in R&D. All other lithographic technologies under consideration—e-beam direct write, nano-imprint, directed self-assembly—can help with patterning certain layers for certain chips, but lack the broad applicability and economic advantages of 193nm.
At this year’s SPIE Advanced Lithography event, renowned lithographer and gentleman scientist Chris Mack led an extended toast (https://www.youtube.com/watch?v=IBrEx-FINEI) that ended with, “Moore’s Law is over, long live Moore’s Law.” While Wednesday, February 26, 2014 may seem like a rather arbitrary moment, we seem to have the informal consensus of the world’s leading lithographers.
The 4th blog in this series will discuss the “Why” of Moore’s Law continuing as a marketing term…with each company in the industry using the term as well as “More than Moore” to mean slightly different technology advances. Henceforth, “Moore’s Law” may mean that the next IC will be smaller, or faster, or cheaper…but we are past the era when new chips will be simultaneously smaller and faster and cheaper.
The adjacent figure from SEMI shows the rate of scaling since we hit 90nm half-pitch…the last time that the term “node” directly correlated to the lithographic half-pitch. The clear inflection-point at the “32nm node” (which was really 45nm half-pitch) was the moment that DP was needed for patterning critical layers. In a panel discussion at the 2014 imec Technology Forum in San Francisco during SEMICON/West, John Chen, vice president of technology and foundry management, NVIDIA clearly declared, “Double-patterning is a technological and economic discontinuity.”
I should note that, as the EUV developer for the world, ASML strongly feels that the technology will enable future cost-effective scaling.
Meanwhile, 193nm lithography currently provides the economic limits to scaling, so we can easily understand recent and future phases of the industry in terms of fractions of this wavelength:
½ of 193nm = 90nm half-pitch as the end of simple scaling,
¼ of 193nm = 45nm half-pitch (~32nm “node”) begins Double Patterning,
1/8 of 193nm = 22nm half-pitch begins Quadruple Patterning, and
1/16th of 193nm = 11nm half-pitch which would need Octuple Patterning.
Note that the half-pitch limits shown above are approximations, and the lithography community has been using every trick in the book to lower the resolution limit of 193nm lithography. Water immersion for higher-NA, ‘inverse lithography’ to optimize phase-shifting masks, and off-axis illumination have all been deployed to allow 45nm half-pitch patterning.
Quartz lenses become opaque below 193nm, and thereby limit use of any lower wavelengths. Thus, 193nm has become an economic limit on affordable IC production, just as 1234 km/hr has been proven as the economic limit on commercial aircraft speed. The “Concorde analogy” explains that physical world constraints combine with economics to create real limits on exponential progress.
Since the air-travel industry hit the economic limit of the speed-of-sound, air-travel innovation has continued but not in raw speed. Quiet airplane cabins and huge improvement in in-flight entertainment and food, when combined with refreshments and entertainment in airports improves the overall experience. Wireless computer networks on airplanes and in airports allow travelers with mobile computers (including smart-phones and tablets) to work and play throughout the travel day.
Innovation in the semiconductor industry will certainly continue after we can no longer afford to shrink digital switches. We already have billions of logic elements with which to form circuitry, and we can combine logic with embedded-memory and with sensors and actuators into 3D nanoscale systems. We can do this today. The truth is, when we run out of room at the 2D bottom we have plenty of room to play at the 3D top…remembering that the cost of chip stacking is set by 2D processing economics.
Past post in the blog series:
Imminent posts in this blog series will discuss:
Moore’s Law is Dead - (Part 3) Where we reach atomic limits,
Moore’s Law is Dead - (Part 4) Why we say long live “Moore’s Law”!