Mathematical Modeling And Experimental Study Of Various Sputter Deposition And Corresponding Film Properties

Sputtering is one kind of the most important methods to prepare various kinds offilms. However, now there are still some problems to resolve from electrical deviceapplications such as thickness uniformity, control of the composition of the films, trenchdeposition, defect of the films, et al. A great many of factors should be considered todecrease the cost of manufacture or optimize the process of deposition. In the currentstudy, we investigated the optimization of film properties prepared by DC magnetronsputtering, reactive sputtering, high power impulse magnetron sputtering, and ion beamsputtering. Some new and systematic works have been done to focus on the fabricationprocess to obtain high property thin films using both theoretical and experimentalmethods.1. The thickness uniformity of thin film deposited by magnetron sputtering systemwith rotation and revolution was studied. The theoretical model of sputtering processwas presented. Based on this physical model, the deposition time of various points onthe substrate was obtained using both analytical method and numerical method analysis.Meanwhile, the thickness of thin films was calculated by taking the racetrack profile ofthe target into consideration. The influence of the ratio of rotation speed to revolutionspeed（rev/rot）on the thickness uniformity was discussed. It is indicated that theoptimized thickness uniformity of thin films was obtained when rev/rotis around0.6.The relative deviation is around0.0256. Also, the thickness uniformity prepared bytraditional magnetron sputtering system (without revolution) was simulated. Therelative deviation of it is around0.1936. These two conditions were tested in theexperiment. The relative deviation of those is0.0224and0.1431, respectively.2. The existed modeling for reactive sputtering is only for single-valenceconditions. A modified model for vanadium oxide system was created. In the model, thepresence of metal vanadium, superoxide V2O5, and suboxide VO was involved. Thebasic idea of this work is to find an extended, reliable process model that is abe topredict the hysteresis effects of multivalence composition material thin film. Thefraction of metal and compounds on the substrate has been investigated as a function of reactive gas flow during the reactive sputtering. From the simulation results, substratesurface coverage has been estimated. On the other hand, this paper simulated reactivesputtering in a Vanadium-O2/Ar system equipped with a DC power supply by timedependent model. The target voltage has been investigated as a function of reactive gasflow. Both experiments and simulations demonstrate a hysteresis curve with respect tothe oxygen supply. The time-dependent variation of the target mode is studied bymeasuring the target voltage for various reactive oxygen gas flows and pre-sputteringtimes. It was concluded that the presented theoretical models are in qualitativeagreement with the experimental results and can be used to comprehend the targetvoltage behavior in the deposition of vanadium oxide thin films.3. An effort to optimize the magnetic field configuration specifically for highpower impulse magnetron sputtering (HIPIMS) was made. Magnetic fieldconfigurations with different field strengths, race track widths and race track patternswere designed using COMSOL. Their influence on HIPIMS plasma properties wasinvestigated. The I-V discharge characteristics were measured. The temporal evolutionof electron temperature (Te) and density (ne) was studied employing a triple Langmuirprobe. In the experimental study, the probe was scanned in the whole discharge regionto characterize the plasma distribution and transport. Based on the studies, a closed pathfor electrons to drift along was still essential in HIPIMS in order to efficiently confineelectrons and achieve a high pulse current. As the magnetic field strength increasedfrom200to800Gauss, the ionization rate decreased from60%to30%. It wasexplained by the different distribution of plasma sheath. On the other hand, theexpansion became faster and less isotropic, i.e., more directional towards the substrate.The electric potential distribution was accounted for the effects. Varied racetrack widthsand patterns altered the plasma distribution from the target to the substrate. A spiral-shaped magnetic field design was able to produce superior plasma uniformity on thesubstrate in addition to improved target utilization. Finally, the ionization rate wascompared with the ionization rate of films prepared by DC and MPP power. It’sconcluded that the HIPIMS could perform a much higher ionization rate.4. Particle formation is a major problem in EUV masks and one source of theseparticles has been identified to be the targets used to produce the mask surfaces. Inparticular, the silicon (Si) and ruthenium (Ru) target appear to produce more particles, especially silicon. The evidence of this was seen as a rough region on the edges of thesilicon target. The features in the region were found to be triangular mesas pointing inthe direction of the incident beam. The aim of this research is to prevent the mesaformation features on the target and thus reduce particle formation on the multilayers.Both Si and Ru targets were sputtered using different ion beam conditions to understandthe mesa formation mechanisms on the target. This study also explored the ion beamconditions that can mitigate mesas.2D and3D Monte Carlo computer model (iSAM)were used to understand the formation of mesas with different incident angles of ionbeam (0o,35o,54o,75o) that agrees with the shapes of mesas seen in the experiments.Additionally, SRIM was used to calculate sputtering yields to better understand thedifferent mechanisms between Si and Ru. It’s concluded from both experiment andcalculation results that an effective way to stop mesas formation is to have a sampleoscillating between0oand the desired angle (54°in this work) during sputtering.Finally, a modified model describing the angle spread of ion beam during the sputteringprocess was presented. The model can correctly describe the varied mesa formation onthe varied position of the target.