(class) Of Diamond Films, Microfabrication, Characterization And In Icf Target Fabrication

Chemical Vapor Deposition(CVD) diamond films has a lot of distinguished properties,such as high hardness,high abrasiveness,good thermal conductivity,wide band gap,very low coefficient of fraction,high radiation tolerance,chemical inertness, and so on.These advantages,therefore,make it as an ideal functional materials for many applications,including the areas of national defence,spaceflight,electronics, medicine,materials of ICF(initial confinement fusion) targets,industry and agriculture,etc.It is one of the material research focuses in the field of materials, physics and chemical since 1980's.In this thesis,mainly discussed the diamond films deposition,characterization, micro-machining and its applications in Initial Confinement Fusion(ICF) targets fabrication,which supported by the China Academy of Engineering Physics(CAEP) foundation of "Studies on the fabrications,structure,properties and applications on supper hard nano-amorphous-carbon films",granted number:2005Z0805.The followings are the main contents of this thesis:1.Diamond films deposited by Hot Filament-Chemical Vapor Deposition technology and characterizationed by Raman spectrum.Various techniques,including hot filament-assisted CVD(HF-CVD),microwave plasma-assisted CVD(MP-CVD),radio-frequency plasma-assisted CVD(RF-PCVD), direct current plasma-assisted CVD(DC-PCVD),and combustion flame-assisted CVD,have been employed to deposition CVD diamond films.Since the deposited diamond films have high quality,HF-CVD and MP-CVD are often adopted for the fabrication of applied diamond films.In this paper,diamond films deposited on the Si(100) substrate.The roughness of the surface was 60nm～100nm when the thickness was 4μm～10μm.Diamond films deposited by HF-CVD with low concentration of graphite can be seen in Raman spectroscopy.The surface-enhanced Raman spectroscopy of diamond films coated Au and Ag with different thichness are also discussed in this chapter,but the enhanced coefficient number is only 2～3.2.Micromachining diamond films using Reactive Ion Etching(RIE) techniques.Although diamond films have very good electronic properties,the first challenge in really application encountered is the pattering techniques of diamond films.For its chemical inertness,often use techniques of patterned selective growth and reactive ion etching to pattern diamond films.Considering the compatible with other processes, Oxygen-RIE method is used for pattering diamond films.In experiment,microwave as plasma exciting power,oxygen as reactive gas and argon as assisted gas,negative bias(-80V) added on sample,gases flow ratio is O₂/Ar=4/1,working gas pressure is 0.25Pa,the etching rate is probably 4.21μm/h under above experiment conditions.The diamond film with line wide 20μm～40μm and depth 4μm fine pattern was obtained by oxygen reactive ion etching method in which a patterned aluminium film with thickness of 150nm as the protective mask layer,micro-star and micro-gear were also gained with same experiment conditions.3.Fabrication of diamond micro free-standing structures and cantilever structures by dry etching and wet etching methods.Currently,most of the micro-electro-mechanical system(MEMS) devices are fabricated in silicon due to the present availability of the surface machining processing technology,such as lithography and etching,derived from Si micro-electronics.In many cases,silicon's higher friction and wear limited its applications.Diamond and diamond-like amorphous carbon films can offer excellent tribological properties, low-stiction(hydrophobic) surfaces.However,the main problem in achieving the above lie not only in preparing high performance low stress thick films,but also in establishing an efficient fabrication process,the problem solved through combination of diamond films dry etching and silicon substrate wet etching.First,microstructure made of diamond films are fabricated on the silicon substrate by Oxygen-RIE technology. Second,SiO₂ film coated on the Si surface during Oxygen-RIE process was etched by isotropic wet etching method in a solution mixture of HNO₃ and HF.At last, if the free-standing microstructure are wanted,using Si isotropic wet etching solution etched for a longer time,if the cantilever microstructure are wanted,using Si anisotropic wet etching solution(KOH solution) etched for a longer time,for the undercutting of the microstructure,cantilever structure can be obtained.Using methods mentioned above,free-standing micro-gear and micro-comb are fabricated.The results from SEM testing show that the microstructures have slide side-wall and perfect surface.The etching rate of the isotropic wet etching was much faster compared to the anisotropic wet etching,both of them have relationship with the concentration and the solution temperature.4.Application of Diamond Like Carbon films(DLC) and RIE in the process of ICF targets fabrication.DLC films and RIE technology are also widely used in ICF targets fabrication.In this paper,Al-dot embedded target,CH/Au/Ni multilayer target and DLC shells fabrication processes are described.The Al-dot embedded target is one of the most important targets in the ICF experiment,it consists of a hydrocarbon(CH) film with a Al dot embedded in the center.The target is fabricated through several steps:firstly, depositing the hydrocarbon film and aluminium film,then getting Al-dot by chemical etching,at last,removing residual CH film by Oxygen-RIE technology.Compared with traditional process,this technique can machine many targets in one times. CH/Au/Ni structure is a multilayer structures,Au and Ni patterned by wet etching and electroform technics,CH films deposited by CVD and structured by Oxygen-RIE. Diamond Like Carbon film has a unique physical properties for the ICF ablator application,such as appropriate optical properties,high atomic density,high yield strength,and high thermal conductivity,is one of the important ignition target(IT) materials.This paper presents a feasible process to fabricate DLC ablator shells.The fabrication of DLC hollow shells is a multi-step process,which involves DLC films deposition on copper mandrels by magnetron sputtering using graphite as target, followed by micro-fabrication of holes with laser,and removing of the Cu mandrel by wet etching process with HNO₃ solution.This work is just a elementary study,it is a base for future research on this project.