We have calculated a quaternary phase diagram of the Al–Ti–O–N system, valid in the range of temperatures between 450 and 550 °C. In particular, the respective composition ranges of all the binary compounds were taken into account and are listed along with their composition and structure. The four simplified ternary diagrams (Ti–Al–O, Ti–N–O, Ti–Al–N, and Al–N–O) were first calculated to constitute the four faces of the tetrahedron representing the quaternary phase diagram. The interior tie lines of the quaternary diagram were calculated with the same proposed procedure that was used to obtain the ternary diagram. Two of these tie lines are important, one of which links TiN and Al2O3 and one which links AlN and TiO2. The utility of this diagram is illustrated by predicting the phases that are likely to occur during the reaction between Al and TiN layers, the latter compound being oxydized or not.
A novel resistless lithography process using a conventional electron beam system is presented. Metallic lines with widths of less than 50 nm were produced on silicon substrates. The process is based on localized heating with a focused electron beam of thin platinum layers deposited on silicon. It is demonstrated that silicide formation occurs at the Pt-Si interface. By using a dilute solution of aqua regia, it is possible to obtain a sufficient difference in etch rates between exposed and unexposed regions of the platinum thin film to selectively remove only the unexposed areas.
The stability of TiN barriers deposited between Si or SiO2 substrates and AlSiCu metallic alloy contacts was investigated as a function of the sintering temperature and of the application of an oxidation step to the barrier. It was found that Al penetrates the barrier during the sintering at 450 °C for 1 h, which also results in the diffusion of Ti inside the Al alloy. This mutual interdiffusion increases with temperature but when oxygen is present at the barrier surface, the intensity of diffusion processes decreases considerably. It is also established that the barrier remains more stable on SiO2 than on the Si substrate. It is suggested that the better reaction resistance of oxidized TiN compared with oxygen-free nitride may be due to the blocking of fast-diffusion paths of Al diffusion by oxygen and subsequently the formation of Al2O3, AlN, and TiAl3 phases during sintering.
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