Comparison of the Properties of Molybdenum Silicide Films Deposited by D‐C Magnetron and RF Diode Co‐Deposition

Abstract

We report a preliminary study in w~.ch the physical and electrical properties of d-c magnetron and co-deposited rf diode molybdenum silicide films of varying stoichiometry are compared. It is shown that the d-c magnetron films deposited from a composite target tend to be non-optimal in comparison to the rf diode co-deposited films of the same stoichiometry. Extensive degradation of the d-c magnetron films was frequently observed during heattreatment at 1000~ in nitrogen or argon ambient. The rf diode films, however, appear to withstand heat-treatment without signs of degradation. There appear to be significant differences in film stress changes during heat-treatment, i.e., the d-c magnetron films exhibit a severe change in stress level resulting in a highly tensile state which causes film cracking and loss of adhesion, whereas the rf diode co-deposited film stress changes to minimal values during heat-treatment. Additional data on crystal morphology, resistivity change during heat-treatment, and general fihn properties are also discussed.Refractory metal silicides have been proposed as alternatives to polycrystalline silicon ("polysilicon") for gate electrode or interconnection metallizations in field effect transistor devices of VLSI dimensions (1-4). This trend has evolved as a consequence of the prohibitive values of resistance encountered in conventional polysilicon gate technology as device geometries are reduced.One significant problem with these newer materials appears to be the relatively high levels of contaminants (e.g., oxides, carbon, and alkalies) presently found in composite, hot-pressed sputtering sources (targets). These contaminants not only can alter device characteristics irreversibly, but also may result in the loss of film integrity during subsequent high temperature (1000~ device processing steps.Another potential problem with refractory silicide thin films may be the high levels of intrinsic film stress often found in these films. Additionally, many commercial sputter deposition systems do not provide a means of controlling this film stress through controlled d-c or rf substrate bias (5, 6). Films deposited with high levels of intrinsic stress can also fail in subsequent high temperature processing, where thermal expansion coefficient mismatch between film and substrate is exaggerated.In this preliminary study, we describe a co-deposition technique in which rf sputtering is done from separate high purity targets of the refractory metal and silicon with and without substrate bias. Additionally, we compare the physical and electrical properties of molybdenum silicide films prepared by this technique with films deposited from a composite target by the d-c magnetron technique.Experimental D-C magnetron deposition of molybdenum silicide.--All d-c magnetron depositions were done in a PerkinElmer Model 4400 cryo-pumped sputtering system equipped with a hot-pressed source (target) of molybdenum disilicide of 99.9 purity (Metron). The target was solder-bonded to a standard water-cooled copper backin...

Forensic science

“…AES was used to determine the in-depth composition of niobium nitride formed by laser annealing of niobium metal immersed in liquid nitrogen (652). The properties of molybdenum silicide films for very large integrated circuit use were measured (427,674,827,882,979). The XPS spectrum and band structure of RuC13 were reported (601).…”

Crystalline Structure Changes of Molybdenum Silicide Films Deposited by Sputtering and by Coevaporation after Isochronal Annealing

“…Although many publications have been reported on device fabrication with these silicides (1)(2)(3)(4)(5)(6)(7), and on their physical properties (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), the silicide technology is still in its formative stage. Some of the principal problems with these silicides at present are physical properties such as crystalline structure and internal stress, and electrical properties under the subsequent high temperature heat-treatments.…”