Film‐Substrate Interaction in Si/Ta and Si / Ta2 O 5 Structures

Abstract

Gravimetric and SIMS analyses of vacuum‐deposited Ta films on Si substrates as well as Ta2O5 films obtained by their thermal oxidation demonstrate a significant interaction in normalSi/normalTa false(Ta2O5false) structures well below the usual temperatures required to form TaSi2 or SiO2 on silicon. The interaction begins during the deposition of the Ta film, leading to the incorporation of silicon in the film. It is suggested that oxygen gettered by tantalum facilitates this process. During oxidation of the Ta film, the silicon in the film is cooxidized and oxygen diffusing through the already formed oxide enhances the further entry of silicon into the film. Oxygen diffusing through the completely oxidized Ta film further reacts with the silicon substrate during postoxidation heat‐treatment in oxygen. There is no evidence that the interaction during any of these three steps is caused by intermixing elemental tantalum and silicon. The results of gravimetric and SIMS analyses are qualitatively consistent with the measured dielectric parameters of the film and the observed electronic properties of the normalSi/Ta2O5 interface.

Selective Studies of Crystalline Ta2 O 5 Films

“…These studies attempt to utilize the high dielectric constant, low leakage, and high breakdown properties available with amorphous Ta20~ films formed by anodization processes (4). In view of the high electrical leakage exhibited by crystalline CVD Ta20~ films (5), the emphasis of recent studies has focused upon the evaluation of "dry" amorphous Ta205 films formed either by the low temperature thermal oxidation of deposited Ta films on silicon substrates (6)(7)(8) or by sputter deposition (9).…”

The role of passive film growth kinetics and properties in stress corrosion and crevice corrosion susceptibility

“…In Figure 6 are compared repassivation rates for the 18, 15,9,6 and 3% alloys at their respective open circuit or corrosion potentials. It is immediately obvious that repassivation is exceptionally difficult for the 6 and 31 alloys.…”

“…A neon field ion micrograph obtained from an iron specimen exposed to a small partial pressure of air, 30K, 9400 volts. Flydrogen field ion micrographs obtained from a uranium specimen exposed to hydrogen imaging conditions for about 15 It can be seen from the above discussion that Si 0 2 films can be very perfect in spite of, rather, because of the fact that they are noncrystalline.…”

“…30 Also, an oxidizing reaction due to oxygen diffusion through the Ta 2 0 5 takes place at the Si/Ta 2 0 5 interface at a temperature which is not sufficiently high to oxidize bare silicon. 15 Kinetic rather than thermodynamic considerations are crucial in thin film phenomena where the interface energy is often high and overcomes other energy barriers . These "thin film effects" further complicate the situation in noncrystall i ne oxide films which is already complicated due to the lack of crystallinity.…”

Task 3.0: Advanced power systems. Semi-annual report, April 1--June 30, 1993

“…Tantalum and tantalum pentoxide have long been used in thin film microelectronic devices (64)(65)(66)(67)(68)(69). Several methods exist for deposition of dense uniform Ta205 films, including chemical vapor deposition (CVD)(70-72), physical vapor deposition (PVD) (73)(74)(75)(76), anodic deposition (77,78), and thermal oxidation (79) of tantalum metal films.…”