Kenneth E. Gonsalves

Nanocomposite resist systems for next generation lithography

A novel nanocomposite resist system was developed for sub-100 nm resolution e-beam lithography by dispersing surface-treated silica nanoparticles in a commercial ZEP520® resist. At 4.0 wt.% loading of silica nanoparticles, the system exhibited a much higher resolution than ZEP520® without sacrificing the intrinsic sensitivity and contrast of the starting polymer. The first major result is that 46 nm-wide isolated lines were obtained in the nanocomposite system (∼250 nm-thick layer), whereas comparatively 130 nm-wide lines were obtained in ZEP520® under the same experimental conditions. Contrary to standard e-beam resists, this important reduction of line broadening already occurred at 20 keV while higher energy e-beams (up to 100 keV) did not lead to further line broadening reduction. Moreover, it was shown that the addition of silica nanoparticles resulted in a higher resistance of the nanocomposite to plasma etching with 02 gas. Subjecting this nanocomposite resist to 75-keV Xe+ ion irradiation showed that it is also particularly suitable for ion projection lithography as a preliminary resolution of 114 nm (1/s) was obtained while the sensitivity increased by a factor of 40 compared to 30-keV electrons. Extending the nanocomposite approach to KRS-XE®, a chemically amplified resist, led to both enhanced resolution and mechanical stability for electron beam lithography. The major resolution and etch resistance improvements in both resist systems indicate that nanocomposite systems are promising candidates not only for sub-100 nm resolution e-beam lithography but also for ion projection lithography. Supported by preliminary Monte Carlo simulations a tentative mechanism highlighting the electron-nanocomposite interactions as the explanation for line broadening reduction is proposed.

Effects of material design on extreme ultraviolet (EUV) resist outgassing

Optics contamination is a huge concern for extreme ultraviolet (EUV) lithography. In efforts to protect EUV optics, all materials used in EUV vacuum exposure chambers must be screened prior to use. Photoresists are a concern since a freshly coated wafer will be introduced into the chamber approximately every minute in a high volume production tool. SEMATECH has initiated a resist outgassing program to screen new resists and to learn outgassing characteristics using model compounds. This paper presents outgassing data for commercial resists as well as resists made by university researchers. Several resists made at the University of North Carolina at Charlotte (UNCC) were measured, including polymer-bound photoacid generator (PAG) resists such as poly (HOST-co-EAMA-co-PAG). Previous papers have reported that a large portion of outgassing is due to PAG fragments and deblocking groups. The UNCC resists outgas an order of magnitude less than most commercial resists tested by SEMATECH. This may be due to the low diffusion of the acid-cleavable adamantyl groups after exposure. In addition, fewer PAG species outgassed in the polymer-bound PAG resist than in blend PAG resists.

High sensitivity nanocomposite resists for EUV lithography

A novel nanocomposite photoresist was synthesized for extreme ultraviolet lithography (EUVL) by a radical polymerization process. This resist system exhibited enhanced sensitivity and contrast for EUVL. The potential for EUVL nanofeatures is also examined. The high sensitivity and the desirable contrast in this resist, indicates that it is a promising candidate not only for sub-100 nm resolution EUVL, but also for X-ray lithography and low voltage electron beam lithography.

A Versatile Approach for Biomaterial Patterning: Masked Ion Beam Lithography

We describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (methyl methacrylate) (PMMA) film was used as a model system and subjected to Ca + and P + ion implantations through masks. Ca + ion implantation was performed at an energy of 85 keV with a fluence of 1x10 14 ions/cm 2 . P + ion implantation was done at an energy of 85 keV with fluences of 1x10 15 and 1x10 16 ions/cm 2 . Arrays of holes were generated during these processes. AFM showed that the depth of the holes is in the nanoscale region. The surface hydrophobicity of the exposed PMMA films was investigated by contact angle measurement. The results indicated that ion implantation changed the surface hydrophobicity.