New fluorine-free compounds for use in 193-nanometer lithography
23 Feb 2010 -- Researchers with the IBM Semiconductor Research and Development Center have announced new compounds for a critical step in chip manufacturing that can offer improved environmental benefits over those used in current processes today. The IBM-invented compounds are for use in semiconductor photolithography - the process by which chip circuitry is imprinted on silicon wafers - one of the most challenging steps in chip manufacturing.
The IBM researchers will describe the new materials at the SPIE Conference on Advanced Lithography, February 21-25 in San Jose, California, in a paper titled "Design, Synthesis and Characterization of Fluorine-free PAGs for 193nm Lithography."
The invention is a new type of photo-acid generator (PAG) for the production of semiconductors using 193nm lithography. The photo-acid generator is one of several components of a system of chemicals used in the photolithography process to transfer circuit patterns onto semiconductor wafers. It helps to amplify and clarify the circuit image, which has become a critical and challenging step in semiconductor manufacturing as chip dimensions continue to shrink with each technology generation. The semiconductor industry currently uses 193nm photolithography equipment and processes to manufacture advanced chips with 65- and 45-nanometer (billionth of a meter) circuit dimensions, and is expected to use them for next-generation processes down to as small as 15nm.
This new suite of compounds is the industry's first fluorine-free PAG for 193nm lithography chip processing. The compounds used for this process in the industry today are typically flourine-based perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Research has showed that these compounds can persist in the environment and gradually increase in concentration over time. Since IBM's new compounds are fluorine-free, they can offer an environmentally preferable solution for the semiconductor photolithography process.
IBM's solution is an example of "green chemistry" in action - applying molecular design to invent new more environmentally benign compounds. IBM researchers studied how the molecular structure of existing PFOS- and PFOA-based chemicals functioned as photo-acid generators. They designed an array of alternate chemical structures that would provide the desired performance without the use of fluorine, and then synthesized and tested the newly-formed compounds.
IBM researchers have demonstrated the new chemicals meet the performance requirements for both dry and immersion 193nm photolithography in semiconductor manufacturing, with equivalent performance in 45nm technology for optical transparency, solubility, thermal stability and shelf-life.
This latest achievement adds to IBM's more than 30-year history of materials innovation for the semiconductor industry.
"IBM has a long history of inventing winning chemistries and providing breakthrough materials solutions for advanced semiconductor processes," said Dr. Rao Varanasi, manager of patterning materials research and development for IBM "This latest fluorine-free photo-acid generator invention adds another dimension to IBM's intellectual property portfolio and provides unique opportunities to help develop environmentally preferable patterning materials through strategic engagements with the photoresist industry."
IBM holds several patents on the new compounds and is in discussions with a number of chemical suppliers concerning their license.