Structural Analyses of Fluorine-Doped Silicon Dioxide Dielectric Thin Films by Micro-Raman Spectroscopy
- PDF / 174,906 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 0 Downloads / 178 Views
STRUCTURAL ANALYSES OF FLUORINE-DOPED SILICON DIOXIDE DIELECTRIC THIN FILMS BY MICRO-RAMAN SPECTROSCOPY Jeffery L. Coffer* Department of Chemistry Texas Christian University, Ft. Worth, Texas 76129 T. Waldek Zerda Department of Physics Texas Christian University, Ft. Worth, Texas 76129 Kelly J. Taylor and Scott Martin Texas Instruments, Kilby Center, Dallas, Texas 75243. Abstract Fluorine-doped silicon dioxide, a dielectric material compatible with copper integration, has received considerable attention for applications requiring a k value in the 3.5 to 4.0 range. Given the influence of structure on desired properties, convenient experimental structural probes of this type of material are of widespread interest. This work focuses on Raman spectroscopic analyses of ring defects in fluorine-doped silicon dioxide films prepared by plasma enhanced chemical vapor deposition (PECVD) as well as high density plasma methods (HDP). These measurements are complemented by ab initio computational simulations of the ring defects in these films and the impact of nearby fluorine on their stability. The impact of aging on these structures and correlations of observed trends with experimental techniques such as X-ray fluorescence are also described. Introduction There is an ever-pressing need for rapid, non-destructive methods in the structural characterization of silicon dioxide-based low k dielectric films, including fluorine-doped variants. The vibrational spectroscopic technique of Raman scattering provides unique information with regard to the presence of strained silicon-oxygen ring defects in these materials.1,2 Specifically, these defects are noted by characteristic bands attributed to so-called 3member ring defects (Si3O3) at 608 cm-1 as well as a 4-member ring mode (Si4O4) near 503 cm1 3,4 .
Si 3-member ring defects
O
O
Si
O Si
Si O
Si O
O Si
Figure 1. Structures of ring defects in plasma-grown CVD films. D5.10.1
O
Si
4-member ring defects
This study focuses on an evaluation of the effect of fluorine incorporation on the relative number of such defects in these films, the type of plasma deposition technique employed, as well as the impact of aging on the evolution of these defects. These observations are complemented by a series of ab initio simulations evaluating the effect of fluorine incorporation on the ground state energy of three and four member silica ring structures. Given the sensitivity of these defects to adsorbed water, these studies have important implications for possible interfacial reactions and subsequent device breakdown. II. Experimental Four classes of oxide-based films were prepared on 200 mm Si (100) wafers for Raman analyses by standard plasma enhanced CVD (PECVD) and high density plasma CVD (HDPCVD). All PECVD films were deposited in a Novellus Systems Concept 2 Sequel reactor of standard configuration. All HDPCVD films were deposited in a Novellus Systems Speed reactor. Table 1 shows a summary of the different films studied. Undoped SiO2 films were prepared by PECVD from both SiH4/N2O/N
Data Loading...
