Research On The Stress Of Homoepitaxial Grown Of The Single Crystal Diamond

In this paper,the stress of single crystal diamond homoepitaxial grown by microwave plasma chemical vapor deposition(CVD)methed is analyzed,the preparation of crack-free and large-size single crystal diamond is studied.The specific research contents are listed below:1.Effects of seed temperature,nitrogen incorporation,and seed quality on the homoepitaxial growth of single crystal diamond were studied thoroughly.The influence of seed temperature on the Raman peak position of single crystal diamond and radical concentration in the plasma was analyzed.And the influence of the defect sites on the stress of single crystal diamond was also investigated.Then,the effect of incorporation nitrogen on the growth of single crystal diamond was studied.In addition,we contrast heteroepitaxial growth based on seed crystals with different quality.It is showed that seed temperature had almost no effect on the radical concentrations in the plasma.In the range of 700-720°C,the quality of single crystal diamond was poor and the shift of Raman peaks was large.The internal graphite phases led to generation of stress of in single crystal diamond,and the total stress was in the form of tensile stress.In the range of 870-890°C,the single crystal diamond with homoepitaxial growth showed good quality.Therefore the shift of Raman peak is relatively large and no graphite peak appears.However,the polycrystalline spots of diamond surface appeared and resulted in stress concentration in the local area,which caused cracks in the single crystal diamond.The total stress is presented in the form of tensile stress.High-quality single crystal diamond with homoepitaxy growth without cracks was proved to be deposited in the range of 770-830°C.The shift of Raman peaks was small,and the total stress was smaller than samples prepared in other temperature ranges.The total stress is presented as compressive stress.The growth rate of single crystal diamond increased with the raise of nitrogen concentration.The incorporation of nitrogen could affect the surface morphology of single crystal diamond,and polycrystalline spots would easily appear on the growth surface;With the increase of nitrogen concentration,Raman peak shifts and total stress of single crystal diamond increased,and it shows compressive stress.After homoepitaxial growth of high-quality CVD seed crystal,it's Raman peak almost unchanged,and the total stress was almost zero.However,for the poor quality CVD seed crystal,the Raman peak of single crystal diamond homoepitaxy growth was similar to seed crystal.In general,diamond epitaxial layer prepared by CVD method was generally better than seed crystal.2.The preparation of single-crystal diamond without cracks was researched in detail.We discussed the effect of nitrogen concentration on the plasma annealing,the effect of annealing time on the stress in homoepitaxial grown single crystal diamond,and the effect of annealing on the surface morphology of single crystal diamond.In addition,we also studied the laser cutting parameters and obtained the most suitable cutting process.And the stress distribution at different positions of the single crystal diamond after cutting was analyzed.The conclusions showed that Raman peaks of the single crystal diamond grown under different nitrogen concentrations shift significantly after annealing and total stress is converted to tensile stress.With the increase of the flow rate of nitrogen,the Raman shift of single crystal diamond increased.And the release of thermal stress increased as the rise of nitrogen concentration.Moreover,plasma annealing could improve the quality of single crystal diamond.As the annealing time increased,the total stress gradually increased and surface was etched.The laser cutting along the boundary between the single crystal and the polycrystal could lead to cracking.The centre of diamond has the best quality and the stress is zero.The total stress of junction between single crystal and polycrystal is the largest,which is represented as the tensile stress.The quality of the cross-section after cutting is the worst,and the total stress is in the middle and presented in the form of compressive stress.