Research On High Quality Diamond Films In Microwave Plasma CVD

Diamond has perfect properties in mechanics, electronics, optics, thermotics, acoustics and wide use. Its potential and maximal application field is for semiconductor films and optic films that mainly rely on the high-orientation and single crystal diamond films and big area transparent diamond films. But it is widely existent for defects in the process of diamond films growth and also it is difficult to get parameters stability such as temperature etc in wide area, as a result, the diamond films' orientation is changed, and it is very difficult to get the high-orientation and single crystal diamond films and big area transparent diamond films. So it is an maximum challenge and difficulty to product heteroepitaxial big size high-orientation and single crystal diamond films and big area transparent diamond films in nodiamond substrate's surface for present diamond films' R&D.By the design of microwave electric field mode and microwave mode converter (MMC), the thesis participated in equipping an domestic microwave plasma chemical vapor deposition (MPCVD) equipment with a quartz glass window and water-cooled stainless steel resonant chamber in 2450MHz/5 KW, introduced the basic machineries and functions of the sub-systems, including microwave system, gas-route system, vacuum system, detecting system and safeguard system. The system can control the CVD process via controlling the CVD parameters accurately to reduce the defects in the process of diamond films growth, by the way, adopt optical fiber optic spectra meter measuring and analyzing the visible spectra of microwave plasma to detect the process of MPCVD.Using the microwave selective heating property for materials, by setupequivalent equation, and first time inducing the electromagnetic field perturbation theory to the design of heating materials for substrate in MPCVD, three temperature distribution modes were established, including temperature distribution comprehensive mode of inhomogeneous plasma, temperature distribution composite mode of composite substrate materials, temperature distribution perturbation mode of composite materials, whichiiprovided an whole new technology route to the design of substrate heating system in MPCVD and guided the preparation of heating materials for substrate. And then the heating materials for substrate were designed and optimized to obtain large area homogeneous temperature distribution even larger than substrate holder's diameter.As an important part, this thesis researched the nucleation and growth of diamond films in MPCVD, systematically researched the effects of substrate pretreatment, methane concentration, deposition pressure and substrate temperature etc experimental technologic parameters on diamond films' quality on (100) single crystal silicon substrate in the process of MPCVD, characterized the films qualities in laser Raman spectra (Raman), X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared transmission spectra (IR), atomic force microscopy (AFM), determined the optimum parameters for MPCVD high quality diamond in the MPCVD-4 mode system . By the control of deposition process, it is succeeded in preparing (100) high-orientation diamond films with maximum single grain's size about 100×100um and 4.693?FWHM (full width of half maximum) in XRD shocking scan curve, and also preparing 75mm large area transparent diamond films with 68.3% average transparence.