Preparation Of Thick Film Of Single Crystal Diamond By MPCVD Method

Because of its advantages of electrodeless discharge pollution,fast deposition rate and strong stability,microwave plasma chemical vapor deposition(MPCVD)is considered to be the best method for preparing high quality single crystal diamond.At present,the biggest obstacles restricting the application of CVD single crystal diamond are the following three main points: growth quality,growth efficiency and substrate area.This research focuses on the above three points.The research on the growth of homoepitaxial single crystal diamond is carried out on the 10 k W and 2.45 GHz loop antenna MPCVD devices independently developed by the laboratory.The research contents include:First,the single crystal diamond wafer with IIa type(100)crystal plane was used as the substrate,polishing,pretreatment and epitaxial growth were carried out,and the influence of hydrogen-oxygen plasma etching was studied in combination with the actual growth.The experimental results show that: 1)the etching ability of pure hydrogen plasma is limited,and the defects and impurities on the surface of the seed crystal are difficult to be etched away.During the growth of diamond,the carbon-containing groups in the plasma are easily defective and scratched.The non-diamond phase is accumulated and nucleated at a relatively low potential energy;2)Under oxygen-containing conditions,the diamond phase is easily etched by hydrogen at a high temperature,and the higher the oxygen concentration,the more the etching effect It is obvious;3)Excessive hydrogen-oxygen etching not only does not improve the crystal plane orientation of the diamond,but also destroys the crystal structure of the seed crystal itself,produces more defects,and improves the surface roughness of the crystal during growth.Second,the continuous growth of single crystal thick crystals and the re-growth of thick crystals were studied,and the continuous growth of single crystal thick crystals with a thickness of 2.4 mm was realized.The results show that: 1)(100)crystal face single crystal diamond has a tendency to expand in the growth process;2)the generation of polycrystalline edges is mainly caused by the inconsistency of the growth surface growth environment(such as growth Inconsistent temperature and plasma energy density,etc.)caused by the tip edge of the seed crystal,rather than the inevitable trend in the diamond growth process 3)When a single piece of diamond thick crystal is grown using an open substrate stage,its growth thickness will be limited due to changes in external environmental conditions(Generation of "yellow powder" and discharge of substrate and substrate holder).Thirdly,combined with the results of microwave electric field simulation and physical discharge,the power adjustable range of single crystal diamond during bulk growth was determined,and the bulk growth of single crystal diamond was realized.Corresponding research and analysis were carried out on the relevant phenomena appearing in the experiment.The experimental analysis results are as follows: 1)With the increase of microwave power,the field strength of the microwave electric field and the range of the strong field in the cavity are obviously increased.When the range of the strong field completely covers the substrate,the surface temperature distribution of the substrate The uniformity is ideal;2)Under the condition of similar deposition environment,the growth rate of diamond at relatively low temperature is higher,and the whole growth process of batch diamond has obvious competitive growth trend.Fourthly,The problem of internal crystal embrittlement during bulk growth of large-area single crystal diamond was analyzed and studied.The experimental results show that :Due to the influence of the outer edge discharge,the local temperature difference of the surface of the substrate located in the edge region of the substrate stage during the growth process is excessive,thereby generating growth stress.Internal crystal embrittlement when the internal growth stress of the substrate reaches a certain level and cannot be released.In the plasma environment,the internal crack of the crystal is affected by the microwave field and the discharge phenomenon occurs,eventually we see the "black stripe".