193-nm immersion simulations extend down to 22-nm node
By Mark LaPedus
Silicon Strategies
02/23/2004, 7:45 PM ET
SANTA CLARA, Calif.--During the SPIE Microlithography conference here this week, researchers from the University of New Mexico will claim that they have simulated 22-nm half-pitch lines, by deploying 193-nm immersion lithography technology.
The disclosure confirms that 193-nm immersion technology could be a viable lithography solution beyond the 45-nm node. It also implies that the technology could push out the need for 157-nm or extreme ultraviolet (EUV) technologies, according to analysts.
"Taking advantage of a water (n=1.44 at 193-nm) immersion lens with NA equal up to 1.3, the 45-nm half-pitch node should be accessible," according to a paper, which will be presented by the University of New Mexico at SPIE. "However, extension of optical lithography to the 22-nm node poses a bigger challenge."
To solve this issue, the university and others have proposed imaging interferometric lithography (IIL). This is a new imaging concept that provides an approach for accessing the fundamental limits of optics. With IIL, the University of New Mexico enabled 22-nm simulations with immersion via KLA-Tencor Inc.'s Prolith simulation tools.
"To get the highest available spatial frequencies, light has to interfere at large angles in the resist and the image contrast become highly polarization dependent," according to the paper. "The choice of polarization in different exposures dramatically improves the resist patterns."
IIL also eases many of the constraints in optical lithography. Besides the University of New Mexico, others are moving down a similar path.
Pushing the theoretical limits of optics, Rochester Institute of Technology (RIT) last week disclose that it has demonstrated image resolutions down to 38-nm with a prototype 193-nm immersion lithography tool (see January 23 story).
Also last month, Taiwan Semiconductor Manufacturing Company Ltd. said it plans to introduce immersion lithography for critical layers of the 65-nm node, starting in the middle of 2005. TSMC also said that 193-nm "wet" lithography could extend to the 22-nm manufacturing process node (see January 28 story). |
