ALD Preparation And Thickness Crms Development Of SiO₂ Nanosized Thin Layers

SiO₂ nanosized thinlayer has unique properties in optics,electricity and mechanics;and has broad applications in integrated circuit,solar cell,surfacemodification areas,etc.In addition,this kind of SiO₂ film has also been selected as ideal material for many existing thickness CRMs?certified reference material?both in China and abroad,CRMs acting as the traceable and transitive carrier for chemical measurement play an important role in the verification and calibration of equipments and in the confirmation and evaluation analysis method.Considering the broad applications and excellent properties of SiO₂nano-film,this thesis carries out the research on the preparation of SiO₂ nanometer thin film grown on silicon substrate as thickness CRMs candidate material,and focuses on solving the proplems of preparation technology and thickness measuring techniques.Development of CRMs usually includes four procedures: prepareation,uniformity test,definition value,stability morniter.SiO₂ nano-films with a series of thickness were fabricated by atomic layer deposition?ALD?technology and the microstructure of the depositiom films werecharacterized by X-ray photoelectron spectroscopy?XPS?,atomic force microscopy?AFM?,X-ray diffraction?XRD?etc,and the thickness of the deposited films was measured by two independent methods,single wavelength ellipsometer?SWE?and grazing incidence X-ray reflection?GIXRR?,which had different measurement principles.The work,development of SiO₂ thickness CRMs,was done when film thickness' s uniformity and stability data were analyzed and the uncertainty value was calculated carefully.The main research contents and results are as follows:?1?SiO₂ nanometer thin films have been successfully prepared by using ALD fast heat process.Reaction temperature,carrier gas flow,character time?Si pulse time,Si purge time,O pulse time,O purge time?are analyzed through the single variable method,it is found that the O pulse time is the key factor affecting the film thickness distribution,the optimum heat process is as following: reaction temperature equals to 325?,chamber flow and process flow corresponds to 200 sccm and 300 sccm separately,waiting time?W0?before reaction is setas 30 s,four character times,namely,Si pulse time,Si purge time,O3 pulse time,O3 purge time are selected to be 0.05 s,0.40 s,0.70 s,0.40 s individually.Underthis optimum growing process,SiO₂ nanometer thinfilm's growth rate?GPC?approaches to 0.11nm/cycle,thickness uniformity index?thickness relative standard deviation?reaches to 0.90%,which meets the uniformity target of thickness CRMs?less than 1.00%?.SiO₂ samples with different nominal thicknesses are fabricated via adjusting the ALD reaction cycle numbers.?2?SiO₂nano-film made by ALD technique has been characterized by different equipments and the results of structural analysis show that the microstructure of the SiO₂film?thickness interval is from 10 nm to 120nm?is amorphous,the average roughness on film surface equals to 1.55 nm.The whole film area can be divided into several layers according to substrate signal varying with sputtering time from XPS depth analysis experiment,the equivalent thickness of surface comtanmicationapproaches to 0.29 nm via cleaning comparison experiments,the thickness of natural oxide layer is calculated as 1.26 nm based on XPS thickness calculation formula and measurement data,and the theory thickness of two transition layers arranges from 1.00 nm to 1.50 nm proved by XPS sputtering experiment.These characterization data can supply reasonable initial parameters and multilayered model for GIXRR fitting model,which can improve the thickness fitting efficiency and precision.?3?Intense research has been done for two thickness measurement methods;SWE measurement is optimized and fixes the refractive index when measuring process,the relationship between refractive index and thickness is detected by multi-wavelength spectroscopic ellipsometer?SE?.As for GIXRR original data,software fitting and linear formula calculating treatments are discussedseparately,a good consistency is verified between them.An excellent GIXRR fitting model is key factor for accurate software fitting thickness,the optimum five layers model?native oxide layer+transion layer 2+SiO₂ body layer+transiton layer 1+contamination layer?is defined after gradually changing model layer and comparing fitting graph/parameters.Standard materials choosing from each nominal thickness are measured by GIXRR and SWE methods together;the average thicknesses detected by SWE and GIXRR achieve good consistency,and the thickness deviation is less than 0.10 nm.Part samples of thickness CRMs are selected and uniformity test is conducted,the calculated statistic value F,which can be used to judge uniformity of these prepared nanosized films.Stability mornitor data has been dealt with linear formular and the obtained corresponding line slope 1b <0.05 1t?n-2??S?b?,which proves the thickness can remain stable during the whole mornitoring period.In the end,the thickness standard value and expanded uncertainty of eachnominal thickness SiO₂ nano-film are calculated and expressed.