AVS 51st International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM10
Silicon-rich Nitride Characterization for Polysilicon Gate Patterning

Wednesday, November 17, 2004, 11:20 am, Room 303C

Session: Optical Thin Films
Presenter: F. Celii, Texas Instruments
Authors: F. Celii, Texas Instruments
K. Hewes, Texas Instruments
S. Zheng, Texas Instruments
E. Mickler, Texas Instruments
Correspondent: Click to Email
For manufacturable patterning of sub-0.10 µm poly-Si gates, advanced etch techniques must complement current lithography capability. One approach uses photoresist line-narrowing combined with an etch hardmask that serves the dual purpose of forming a low-reflectivity patterning substrate. The hardmask suitability is determined by the poly-Si etch resistance, the optical properties (if used as an anti-reflection coating (ARC) layer) and integration issues (e.g., cleanup and cost). The requirements on the hardmask will change with subsequent generations, as the material stack layers and thicknesses change. We report the characterization of silicon-rich nitride (SRN) films used in poly-Si gate patterning. SRN films were deposited by PECVD in commercial reactors. Initial characterization used variable-angle spectroscopic ellipsometry (VASE), over the wavelength range 140 - 1100 nm. Modeling of the VASE data provides optical constants at lithography wavelengths (193, 248 nm) of the various film compositions. Based on previous work, the spectral dependence of the optical constants also provided a measure of the Si-loading of the film. The Si-content of the previously-studied sample set (37 to 41%),@super 3@ which gave k@sub 193@ values up to 1.0, was significantly extended with the current set, with k@sub 193@ values up to 2.0. Moreover, the (n,k) values of the current SRN films fall along a fairly narrow line. Additional characterization of these films will include composition measurement by RBS spectroscopy and FT-IR spectroscopy characterization over 400 - 4000 cm,@super -1@ which yield an independent measure of Si-dimer concentration. Simulations of gate patterning structures show (n,k) values which yield reasonable patterning process margin. CD swing curves of patterned films will also be presented.