Comparative Studies of Thin-Film Ti-Si and Ti-SiO 2 Rapid Thermal Reactions Using the RIP/TEM Technique
- PDF / 1,885,483 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 64 Downloads / 208 Views
COMPARATIVE STUDIES OF THIN-FILM Ti-SI AND TI-SIO2 RAPID THERMAL REACTIONS USING THE RIP/TEM TECHNIQUE
MENACHEM NATAN Martin Marietta Corporation, Martin Marietta Laboratories, Baltimore, MD21227
1450 S. Rolling Rd.,
ABSTRACT One requirement of self-aligned microelectronics metallization processes Is selectivity of reactions, e.g., a deposited, thin metal film must react with SI to form a silicide, yet avoid reaction with SIO2 Rapid thermal processing (RIP) techniques may enhance selectivity by utiIzIng differences in competing reaction kinetics. In this paper, we apply the RTP/transmission electron microscopy (RTP/TEiM) technique to determine processing temperature (T)/time (t) "windows" for selective sulicide formation In TI-Si vs Ti-SiO2 reactions. Free-lying Si/TI/SI and SiO/Ti/S10 2 films deposited on electron microscope grids were RTP'd In pairs and immediately examined by TEM. The products of the interfacial reactions, their sequence of appearance, and the T/t conditions for silicide nucleation and growth In each system are described.
INTRODUCTION In the self-aligned TI silicide processill, a silicide/polysilicon (polycide) gate and silicidized contacts to junctions in MOSdevices are formed simultaneously, reducing the resistivities of both to less than 1 ohm/sq. The process includes depositing a blanket Ti film over both Si and SiO2 areas and then annealing at a high temperature to react only the TI/Si regions. The unreacted TI on S102 Is then etched away. The annealing parameters (temperature and time) must be judiciously chosen since thermodynamic considerations indicate that Ti will also react with SI0 2 121 at sufficiently high temperatures. However, the kinetics of the TI-Si reaction are significantly faster than those of the TI-SiO2 reaction, allowing a processing window in temperature and time, particularly under rapid thermal annealing condltions.131 Finding the exact boundaries of this'window could require extensive trial-and-error processing; the RTP/TEM techniquel41 can significantly
simplify and speed-up the procedure.
The films used In RTP/TEM studies are either polycrystalline or amorphous. The products of the metal/Si reactions appear to bel5I independent of the type of Si Isingle crystal (x-Si), polycrystalline (c-SI), or amorphous (a-SI)I. However, the kinetics of silicide growth on evaporated (i.e., amorphous) SI are faster than on x-Sii61, probably because the TI/a-Si Interface is cleaner than the TI/x-SI Interface. The self-aligned process involves TI reaction with x-Si (source and drain regions) and c-SI (gate), whereas the as-deposited Si films in RIP/TEM samples are emorphous. Thus, the relevance of our results to real-life processing depends to a great extent on the assumption that Improvements In Si surface treatments prior to Ti deposition will bring the kinetics of Ti/x-Si and Ti/c-Si closer to those of Ti/a-SI reactions. As shown later, this restriction is eased by the fact that the Si crystallizes to c-Si prior to the reaction with Ti.
EXPERIMENTAL Trilayer SI/TI/SI and S
Data Loading...
