John A. Iacoponi

Combined spectroscopic ellipsometry and reflectometry for advanced semiconductor fabrication metrology

Spectroscopic reflectometry has been a mainstay of optical semiconductor metrology for many years, as has single wavelength ellipsometry performed at a fixed angle of incidence. More recently, spectroscopic ellipsometry has been employed to provide film thickness and optical constant measurements with greater precision and accuracy. In this work we demonstrate the combined use of spectroscopic ellipsometry (performed from 420 - 720 nm at 75 degree angle of incidence) and spectroscopic reflectometry (performed from 200 to 800 nm at normal incidence) for the characterization of thin films and multilayer stacks commonly encountered in semiconductor device fabrication. By employing sophisticated parametric dispersion models and simultaneously fitting both the reflectance and ellipsometric spectra, we are able to perform accurate and precise characterization of many structures that cannot be characterized with either technique alone or with combined reflectometry and single wavelength ellipsometry.

Novel Approach to Reduce Source/Drain Series and Contact Resistance in High-Performance UTSOI CMOS Devices Using Selective Electrodeless CoWP or CoB Process

This letter reports a selective metal deposition process using an electrodeless technique for MOSFETs fabricated in an ultrathin silicon-on-insulator (UTSOI) substrate. A layer of metal (CoWP or CoB) is formed on the source and drain nickel and cobalt silicides without depositing on the dielectric spacers. Leakage current information, which is an indication of selectivity of the process, is presented in this letter. The shortest channel length of the UTSOI NMOSFETs is 20 nm, and the SOI thickness is 10 nm. The data show that excellent selectivity is achieved without increasing the leakage current of the transistors.

Chemical rate model for the surface pyrolysis of tetrakis(dimethylamido)titanium to form titanium nitride films

A chemical kinetic rate model for the deposition of titanium nitride films from the surface reaction of tetrakis(dimethyl-amido)titanium (TDMAT) was developed. Without ammonia addition, TDMAT forms a titanium nitride film by pyrolyzing on the hot substrate surface. Experimental data from the applied materials 5000 deposition tool was modeled using a CSTR formulation. With the parameters of the surface reaction model regressed to fit portions of the experimental results, reasonably accurate model predictions over the entire domain of experimental data were obtained.