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Effects of Heat Treatment on the Microstructure and Stress of Cr/Au Bilayer Thin Films

Author: WangBoYang
Tutor: FeiWeiDong
School: Harbin Institute of Technology
Course: Materials Engineering
Keywords: annealing substrate heating stress thin film gold chromium
CLC:
Type: Master's thesis
Year: 2013
Downloads: 29
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Abstract

In this dissertation, Au films on glassy SiO₂were prepared by DC magnetronsputtering. The adhesion between the Au films and the substrate is poor as themismatch coefficient is too large. So deposited Cr films on the substrate as anintermediate layer before the deposition of Au. Finally the system SiO₂0.36mm, Crfilm30nm, Au layer composite film200nm. Double-layer films were preparedunder different conditions of heat treatment: annealing and heating the substrateduring deposition. XRD θ-2θ scan technique are used to characterize the phases andmicro-strain of Cr/Au bilayer films,2θ-ω scan technique are used to characterizethe macroscopic stress of the film. Atomic force microscopy is used to characterizethe surface morphology. The four-probe tester is used to characterize the conductiveproperties. The properties and performance of Cr/Au bilayer films transition on heattreatment is studied in detail and systematic.As the study results, the Au film of prepared Cr/Au film layer with a strong（111） texture plane which exists tensile stress, in the case of no heating of thesubstrate. The texture of films after annealing is not abating significantly. Butannealing can effectively eliminate macroscopic residual stress in the film and themicrostrain caused by the defects such as dislocations and the hole. Stress-strainreduction can strengthen by increasing the annealing temperature and annealingtime extension. Heating the substrate during sputtering deposition the Au film layer,which can weaken the texture phenomenon of Au film. But the microstrain of Aufilm would significantly increase, and residual stress in Au film is tensile stress. Thesurface morphology of the film is impacted vulnerable by heat treatment process.Whether to increase or extend the annealing temperature annealing time, the surfaceroughness of the film can reduce, the particle size of surface would decreases. Afilm was prepared by heating the substrate would change the surface morphologysignificantly. The surface particle size increased dramatically and roughnessbecomes large. And with the substrate temperature rise, this change has becomeincreasingly clear that when the substrate temperature reaches200℃, the maximumheight difference of Au film will be greater than80nm. Annealing also causes thelattice spacing of Au thin film is reduced. The out rate of Au film spacing is notproportional with the annealing temperature. Changes in its relationship with the annealing temperature was "S" shaped curve. There is a critical point of about300℃. When the annealing temperature is below the critical point, the narrow rateof spacing slower, and the rate of reduce increase of the annealing temperature, thespeed is also smaller. This change is due to interdiffusion of elements betweenCr/Au bilayers films which caused by annealing. When the annealing temperature isbelow200℃, as the microstructure strain decreases by annealed, the surface sheetresistance of the film can reduce and the conductivity of the film can increase. Oncethe annealing temperature exceeds200℃, element diffusion between layers byheating will cause the negative effects, which will exceed the effect of microstrainreduced. The rise of sheet resistance will accelerate. Heating the substrate while Inthe preparation of the films will decrease conductivity of the films. When theannealing temperature is below200℃, as the microstructure strain decreases byannealed, the surface sheet resistance of the film can reduce and the conductivity ofthe film can increase. Once the annealing temperature exceeds200℃, elementdiffusion between layers by heating will cause the negative effects, which willexceed the effect of microstrain reduced. The rise of sheet resistance will accelerate.Heating the substrate while In the preparation of the films will decreaseconductivity of the films. General aspects of the film performance can be seen, thehigher annealing temperature will reduce film properties. But the annealing processless than175℃can be improved the film properties.

Effects of Heat Treatment on the Microstructure and Stress of Cr/Au Bilayer Thin Films

Abstract

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