The reactions of metal layers with their silicon substrates resulting in the formation of various silicides are considered generally not only as phenomena common to all diffusion couples where new phases are formed, but also as typical of all transitions from two to three phases. The conditions under which such transitions will display the same characteristics as encountered in the usual one-to-two phase transitions (condensation, crystallization, boiling) are analyzed by comparison to the classical theory of nucleation. Because of the lack of knowledge about the exact values of the relevant parameters, the discussion is carried out mostly in descriptive thermodynamic terms. Although nucleation effects are analyzed in general terms, the main focus of attention is a class of reactions where nucleation dominates the formation of a new phase; a salient feature of these reactions is the absence of any equilibrium temperature, although the nucleation temperatures are relatively well defined within narrow limits. Nucleation effects are correlated to such material characteristics as the stability of the nucleated phases, and to such kinetic characteristics as the sequence of phase formation. The modification of the energy levels of the different phases brought about by stress, ion bombardment, or the replacement of usual phases by metastable ones, are considered with respect to their effect on nucleation processes. The nearly total absence of literature references to nucleation in metal-metal diffusion couples is discussed with respect to some specific aspects of the metal-silicon reactions.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400002557

Nucleation of a new phase from the interaction of two adjacent phases: Some silicides

https://ir.nctu.edu.tw:443/bitstream/11536/30330/1/000087849500001.pdf

Progress in the developments of (Ba,Sr)TiO3 (BST) thin films for Gigabit era DRAMs

We have investigated reactively sputtered films of RuO2 for possible application in very large scale integrated circuits. Sputtering yields stoichiometric ruthenium dioxide in a large window of oxygen pressures and the films are reasonably low stressed in the 10−9 dyn cm−2 range. The resistivity of as deposited films is 40 μΩ cm. The films are excellent barriers against interdiffusion of Si and Al.

Characterization of reactively sputtered ruthenium dioxide for very large scale integrated metallization

A manufacturable self-aligned titanium silicide process which simultaneously silicides both polysilicon gates and junctions has been developed for VLSI applications. The process produces silicided gates and junctions with sheet resistances of 1.0-2.0 Ω/square. This paper describes the application of the self-aligned titanium silicide process to NMOS VLSI circuits of the 64K SRAM class with 1-µm gate lengths. Comparison of circuit yield data and test structure parameters from devices fabricated with and without the silicidation process has demonstrated that the self-aligned silicide process is compatible with both VLSI NMOS and CMOS technologies. The self-aligned titanium silicide process has some very significant manufacturing advantages over the more conventional deposited silicide on polysilicon technologies. In particular, the problems associated with etching and depositing a polycide gate stack are eliminated with the self-aligned process since the polycide etch is replaced with a much more straightforward polysilicon only etch. As gate lengths, gate oxide thicknesses, and source-drain junction depths are scaled, linewidth control, etch selectivity to the underlying gate oxide, and cross-sectional profile control become more critical. The stringent etch requirements are more easily satisfied with the self-aligned silicide process.

Development of the self-aligned titanium silicide process for VLSI applications

Tantalum pentoxide (Ta2O5) thin films have rapidly evolved into an important field of research/development for both basic and applied science with the promise of creating a new generation of advanced micro devices for electronics applications. This paper provides a broad review of the current status and future trends of Ta2O5 thin films as a highly promising storage dielectric material for high-density dynamic random access memory applications. Various methods of thin film material processing are briefly reviewed. The physical, electrical and dielectric characteristics of Ta2O5 thin films with specific examples from recent literature and the associated conduction mechanisms are summarized and discussed. Some suggestions to improve the electrical properties of the films are finally included. ©1998Kluwer Academic Publishers

https://ir.nctu.edu.tw:443/bitstream/11536/31493/1/000079946300003.pdf

Preparation and properties of tantalum pentoxide (Ta2O5) thin films for ultra large scale integrated circuits (ULSIs) application - a review

ZrN diffusion barrier in aluminum metallization schemes

Atomic motion of dopant during interfacial silicide formation

In the first part of this paper the role of rapid thermal annealing in sulicide processing is viewed from a theoretical point of view with respect to what is known about metal-silicon reactions. The second part is a brief survey of the quickly expanding literature on the rapid thermal annealing of silicides. Whereas RTA does not appear to solve all, or perhaps even any, of the problems encountered in the use of silicides, it is concluded that RTA presents a number of definite advantages.

Silicides and Rapid Thermal Annealing

We have studied reactively sputtered ZrN, the most thermally stable of the refractory metal nitrides, for its diffusion barrier properties in aluminum metallization schemes with Rutherford backscattering spectroscopy and transmission electron microscopy (TEM). We find this compound to be very effective against aluminum diffusion up to 500 °C, independently of substrate temperature during sputtering. The useful temperature range can be extended by 50 °C with proper preannealing prior to aluminum deposition. The TEM study of the ZrN grain size as a function of annealing temperature revealed that the grain size does not change significantly upon annealing and that the grains are relatively small even at the highest annealing temperatures (about 300 A at 900 °C). In addition, for annealing temperatures of and below 500 °C large portions of ZrN films were found to be of either amorphous or extremely fine–grain material, thus inhibiting the diffusion along grain boundaries. The presence of Zr 3 Al 4 Si 5 ternary compound in samples annealed at 600 °C, as determined by X-ray analysis, may suggest that the ZrN barrier fails by decomposition of the film by aluminum.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400300033

ZrN Diffusion Barrier in Aluminum Metallization Schemes

The redistribution of implanted dopant atoms during silicide formation has attracted much interest recently because of its important implications for shallow junction device technology. Ion channeling and electrical measurements have shown that dopant atoms are pushed ahead in front of the moving silicide-silicon interface during the growth of near-noble metal silicides. However, dopant redistribution has not been observed with refractory metal silicides. This unique feature of near-noble metal silicides is discussed in conjunction with the growth kinetics of these silicides.

C.-Y. Ting

Papers

ZrN diffusion barrier in aluminum metallization schemes

Atomic motion of dopant during interfacial silicide formation

Silicides and Rapid Thermal Annealing

ZrN Diffusion Barrier in Aluminum Metallization Schemes

Atomic Motion of Dopant During Interfacial Silicide Formation