Growth Mechanism Of Hafnium Nitride Films Investigated By Dynamic Scaling Theory

IVB transition metal nitride films has attracted considerable attention due to itsexcellent mechanical, electrical and optical properties. The surface morphology,structure and properties of the films depend strongly on the growth process, therefore,understanding the surface evolution process and growth mechanism of IVB transitionmetal nitride film is very necessary. Although people have researched on the growthcharacteristics of IVB transition metal nitride films, but the research still has thefollowing problems:(1) Using the dynamic scaling theory to research the growthmechanism of IVB transition metal nitride film is rarely reported, and mainly in theexisting research on TiN films, HfN films has not been to study.(2) The existingresearch mainly reports themiddle and late surface evolution process of IVB transitionmetal nitride films, and theinitial evolution process is not clear.(3) The existence ofmultiple phase structure of IVB transition metal nitrides, the growth mechanism of thefilms with different phase structures may be different, but there is no comparativestudy of the current literature in different phase structure growth mechanism. To solvethe above problems, this paper uses magnetron sputtering at different substratetemperature and nitrogen flow rate ratio deposited hafnium nitride phase structure(HfNx) thin films, by atomic force microscopy, scanning electron microscopy,dynamic scaling simulation and surface morphology of Gwyddion weresystematically studied, the evolution behavior of thin film surface and the growthmechanism, the main findings are as follows:For the first time, it was found that the salt hafnium nitride film prepared at400DEG (-HfN) dynamic scaling exponent at three growth stages was significantlydifferent, namely the initial, middle and late. In the initial growth, the scalingexponentsareβ1=0.20±0.01，1=0.55~0.98. It is in the island merging stage, and theisland merging process has strong grain boundary energy which makes the depositionof particle diffusion to grain boundaries, so the growth rate at the horizontal directionis greater than the vertical growth rate, and changes in surface morphology isrelatively slow. In the middle growth, the scaling exponents are β2=0.43±0.02，2≈1.The island merging completed makes grain boundary energy to be greatlyreduced, so the power level of growth weakened. But ES barrier which hindersdeposition of particles diffusion between layers makes the vertical growth to be strong,so vertical growth become faster. So that the two minus one by one achieve a relativebalance, the surface morphology is relatively stable. In the late growth, the scalingexponents areβ3=1.04±0.01，3≈1.53. Because of the shadow effect, this film growthrate in the vertical direction is significantly greater than the horizontal direction, thesurface morphology evolution very rapidly, so that the anomalous scalingphenomenon appeared.For the first time, it was found rock-salt phase (δ-HfN), c-Th3P4(c-Hf3N4)andtheir mixed phase (δ-HfN+c-Hf3N4) films prepared at200DEG have different growthbehavior and dynamic scaling exponents. The rock-salt phase and c-Hf3N4film are two growth stages, but their scale exponents was significantly different. The firststage of the scaling exponent of rock-salt phase films asβ1=0.104±0.013，1=0.25~0.6,second stage exponent forβ2=0.181±0.088，2=1.30. The first stage of phase c-Th3P4film scaling exponent of1=0.165+0.036beta, alpha1=0.6, second stage exponentforβ1=0.165±0.036，1=0.6. The comparison between the rock-salt phase andc-Th3P4in the first stage, the nitrogen atoms in c-Th3P4phase are rich and the atomichafnium rare, that the scaling index satisfies the DT model shows that N atoms bindsstrongly the Hf rare. And this leads to diffusion of Hf atoms is difficult in thehorizontal direction, the raised surface to grow more to the vertical direction, whichleads that β is bigger than rock-salt phase and the island merging process becomesweakness. The weak island merging process makes of c-Hf3N4phase did not appearto continuously increase situation like rock-salt phase. In the second stage, with theincrease of film thickness, the deposition rate of film will effect thin film growth. Thedeposition rate of rock-salt phase is almost two times faster than the c-Hf3N4phase,the rock-salt phase tend to grow around, namely become "big"; while the c-Hf3N4phase tended to grow vertical, namely become "high". The β of the rock-salt phase issmaller than the c-Hf3N4phase, and is bigger. Compared with the rock-salt phaseandc-Hf3N4phase, the mix phase only a growth stage, the surface evolution withoutthe mutation phenomenon. The scaling exponent meet the random shot depositionmodel which shows that the rough effect is mainly the shot noise, the smoothingeffect is mainly the surface diffusion in the mix phase growth, there is no reason toincrease rough effect in the mix phase, so the rough effect and smooth effect has indynamic equilibrium, resulting in surface evolution without the mutation.This study reveals that the surface of hafnium nitride film evolution behavior andgrowth mechanism, provide an experimental basis for the surface morphology andstructure control of IVB transition metal nitride films, has a certain academic value offilm unbalanced growth theory.