EUV Lithography Lights the Way to Next-Generation Semiconductors

BERKELEY, Calif., Feb. 4 -- The first full-scale prototype machine has been completed that demonstrates critical capabilities for making computer chips using extreme ultraviolet (EUV) light, announced the consortium of industry and government laboratories that are behind it. They say this breakthrough will lead to microprocessors that are 10 times faster than today's most powerful chips and create memory chips with similar increases in storage capacity.
   Akin to photography, lithography is used to print circuits onto microchips. EUV lithography is being developed because the current chip-printing technology is expected to reach its physical limits in the next few years. Current lithography technology is expected to allow manufacturers to eventually print circuits as small as 0.1 micron in width, or 1/1,000th the width of a human hair.
   EUV lithography technology is being developed to allow semiconductor manufacturers to print circuit lines well below 0.1 micron -- down to at least 0.03 microns (30 nanometers), extending the current pace of semiconductor innovation at least through the end of this decade. Processors built using EUV technology are expected to reach speeds of up to 10 gigahertz (GHz) in 2007. By comparison, the fastest Pentium 4 processor today is 1.5 GHz.
   The consortium includes Berkeley Lab, Sandi-California National Laboratory, Lawrence Livermore National Laboratories, Intel, Motorola, Advanced Micro Devices, Micron Technology, Infineon Technologies and IBM. The prototype machine, called the engineering test stand, was built at Livermore. Berkeley Lab's Center for X-ray Optics provided measurements that enabled the printing of the first tiny lithographic circuits in January.

Measuring Atoms
   "We have a saying in optics: if you can measure it, you can make it," said David Attwood, who heads the Center for X-ray Optics. "New technology at new wavelengths requires expertise in optics, and our specialty (soft x-rays) perfectly fit the needs of the system."
   The Center operates three beamlines at the Lab's Advanced Light Source (ALS). As observed by Gen. John Gordon, administrator for the DOE's National Nuclear Security Administration, "The ALS produces light used to make measurements that are not possible anywhere else."
   To give an idea of size, scientists had to study features that in some cases were 20 to 40 atoms across. The interferometry developed at the ALS -- the most accurate wavefront measuring device in the world, Attwood says -- allowed them to increase the accuracy of the EUV wavelength to about 0.4 angstroms, measuring deviations smaller than the radius of a hydrogen atom. The multilayered molybdenum-silicon coating, the enabling technology for the lithography process, comes in at around 67 angstroms per layer -- half a wavelength. Finding one defect on a printing mask, which the ALS can also do, is equivalent to searching for a golf ball in an area the size of Rhode Island.
   The goal is to etch ever-smaller features on silicon wafers. It is done in vacuum using laser-generated plasma to produce light that cannot be seen with the human eye, using highly sophisticated mirrors that serve as lenses to project computer chip patterns onto silicon wafers. EUV technology is "the leading horse in the race" for next-generation lithography technology in the industry, according to Intel CEO Craig Barrett.

Beamline Teams
   The three laboratories and industry partners -- more than 200 people -- have been working closely on this technology since a cooperative research and development agreement (CRADA) was signed in. They intensively followed up on relevant research whose earliest publication was 1989. The labs formed a Virtual National Laboratory, which has since been a model for similar collaborations. The industry group created a limited liability company to manage the investments.
   Berkeley Lab's metrology effort involved three teams. The first, on beamline 6.3.2., focused on those critical layered coatings and their reflectivity. This group was led by Jim Underwood, one of the pioneers of the coating process, along with Eric Gullikson and Stan Mrowka.
   The interferometry team at beamline 12.0 included the late Hector Medecki, Jeff Bokor, Ken Goldberg, Patrick Naulleau and former student Edita Tejnil, now with Intel. They are now working on the second generation of optics from Tinsley Labs of Richmond as they study improved optics for commercial applications -- "The world's best optics meets the world's best interferometer," Attwood says.
   Beamline 11.3, dedicated to finding defects in the mask patterns, is staffed by Moonsuk Yi of Korea, Tsuneyuki Haga from Japan, and Bokor, a UC Berkeley professor
   As the CRADA with the computer companies completes its fifth year, the three laboratories will improve and refine the test stand machine, a 10-by-10-foot box that sits in a cleanroom at Sandia. Eventually, the precommercial work will be turned over to manufacturers, and if all goes according to plan, by around 2007 we will see super-small, super-fast computers with capabilities for universal language translation, unprecedented medical and biological analysis, nascent artificial intelligence and voice commands.
   Through it all, Attwood said, Berkeley Lab will remain active as the reference standard for EUV metrologies.