Purpose The purpose of this study is to investigate the mechanisms of degradation of aluminum metallization under conditions of thermal shock caused by rectangular current pulses (amplitude j < 8 × 1010 A/m2, duration t < 800 μs). Design/methodology/approach The results were obtained using oscillography and optical microscopy and through the construction of an empirical model of the thermal degradation of metallization systems. Findings Initially, for the authors’ studies, they deduced an equation that associated the depth of melting with the parameters of a current pulse. Research limitations/implications The authors were able to observe effects only in systems with appropriate adhesion of the thin metal films. For the systems with bad adhesion, the main mechanisms of degradation were associated with the melting of the metal, the formation of melted drops (up to 20 mcm in size) and the movement of these drops along the electrical field due to the electrocapillary effect. Practical/implications The mechanisms the authors studied could only occur in high-power semiconductor devices. Originality/value The principal mechanism of melting of a metallization track is linked to the heat dissipation at the interface of solid and liquid phases under conditions of thermal shock. The authors estimated the mechanical stresses in subsurface layers of silicon in the proximity of a non-stationary thermal source. The authors’ results show that the mechanical stresses that are strong enough to form dislocations emerge with current flow with power measuring approximately 0.7 Pkr.

In assessing the reliability of metallization systems, most researchers focus their attention on long term experiments under conditions of subcritical current densities and study degradation processes that are not related to the formation of fused zones [1,2]. How ever, increased electric powers and other severe work ing conditions (in particular, in high current electron ics) favor the degradation of metallization layers up to their fusion. Special investigations have been devoted to the development of methods for diagnostics of met allization systems [3][4][5], including their operation under high thermal loads leading to local phase transi tions [6,7].The present work was aimed at studying phase tran sitions in metallization systems under conditions of thermal impacts caused by rectangular current pulses with amplitude up to j = 8 × 10 10 A/m 2 and durations within τ i = 100-1000 μs.The experimental setup was analogous to that used in [8] and included a source of rectangular current pulses with amplitude of up to 60 A and durations up to 1 ms, a master oscillator, a digital storage oscillo scope, and a microscope (Metam R1) with "numeri cal" eye glass for determining the length of a fused zone. The measurements were performed on test sam ples with a metallization stripe (length, 3 mm; width, 75 μm; thickness, up to 5 μm) on a semiconductor substrate (Fig. 1, inset A).The main current carrying layer in test structures was made of aluminum, which is the main metal used for the metallization of semiconductors. The substrate was made of phosphorus doped (111) oriented silicon plate with a resistivity of 0.01 Ω cm covered with a 60 μm thick n type epilayer (15 Ω cm), which pre vents shunting of the metallization. Some substrates were covered by additional dielectric layers of silicon oxide (SiO 2 ) or silicon nitride (Si 3 N 4 ) (Fig. 1, inset B). The nitride layer was deposited via reaction of dichlo rosilane with ammonia at reduced pressure (~50 Pa) in a temperature interval of 700-900°C. The thermal oxide layer was grown in a temperature interval of 1150-1250°C by standard technology in a diffusion furnace filled with dry oxygen. Some samples were Abstract-First order phase transitions induced in aluminum metallization layers by the passage of single rectangular current pulses with amplitude up to 8 × 10 10 A/m 2 and durations within 100-1000 μs are consid ered. The formation of local fused zones and their subsequent migration during current passage have been experimentally studied. The main mechanisms of interphase boundary propagation due to heat evolution at the solid/liquid interface under conditions of nonstationary heating of the metal film are established. The velocity of liquid phase propagation (~25 m/s) along the metallization stripe has been determined in exper iment and a method of calculating the length of a fused zone upon the current pulse passage is proposed.

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The work is devoted to the study of contact melting in the Al-Si system, which is an aluminum film deposited on a silicon single-crystal substrate. The impulse action of high-density currents (j> 8.1010 A / m2) passing through an aluminum film is analyzed. It was found that under the considered electric heat loads in the system, the degradation processes associated with the appearance of a molten aluminum zone and subsequent contact melting in the metal-semiconductor system develop. From the analysis of contact melting processes, a technique for estimating the coefficients of multiphase diffusion in the system under consideration is a thin aluminum film-single-crystal silicon substrate.

The effect of constant magnetic fields on dislocation anharmonicity of p type silicon single crys tals with a conductivity of 6 Ω cm has been studied. It has been found that preliminary exposure of dislocation silicon (with a dislocation density of 10 4 -10 6 cm -2 ) to a constant magnetic field (B = 0.7 T, t = 30 min) at room temperature causes a change in the nonlinear fourth order elastic modulus β d . The observed changes are associated with the dynamics of magnetosensitive complexes of structural defects and, hence, with the changes in the length of the vibrating dislocation segment. Based on the dynamics of β d (t) after sample expo sure to a magnetic field, the conclusion is made about an increase in the vibrating dislocation segment length L d by 30%, and the characteristic relaxation times of observed effects are estimated.