Simulation And Experimental Study On Large Size Single Crystal Diamond Growth By MPCVD

Diamond,known as the "ultimate semiconductor material," is the most promising semiconductor material at present.However,because of the limitation of diamond size and price,it is challenging to rapidly promote diamond semiconductors' development.The most difficult in obtaining large-area and high-quality single-crystal diamond is the inhibition of the polycrystalline.Through many repeated experimental tests,even if a better growth process is found,it is still difficult to industrialize due to the problems of repeatability and unclear internal mechanism.In addition,in the case of immature online monitoring,how to optimize the diamond growth process at low research and development costs is another key point to promote the development of semiconductor diamonds.In this context,to solve the above problems,combined with the self-consistent model under multi-physical fields in the microwave plasma chemical vapor deposition(MPCVD)chamber with the diamond growth model and combined with the experimental results,the growth of large-size single-crystal diamonds was systematically studied.The main innovative achievements of this paper are summarized as follows:(1)The self-consistent model of the MPCVD chamber under multi-physical fields: In order to inhibit the polycrystalline growth at the surface of the substrate,the self-consistent model of the MPCVD chamber was established in a pure hydrogen atmosphere.The substrate temperatures under different process parameters were calculated,which was in good agreement with the experimental results.The successful establishment of the model can effectively make up for the instability of infrared temperature measurement and the inability to achieve large-scale temperature measurement,providing a reliable analysis method for the growth of large-size diamonds.(2)The substrate holder suitable for high-speed and high-quality growth of the diamond:The growth mechanism of polycrystalline on the diamond's surface was systematically studied by the simulations and experiments.The substrate holder was employed to improve the plasma distribution's uniformity on the substrate surface,and the formation of polycrystalline on the substrate surface was effectively inhibited,but the growth rate was greatly reduced.Combined with the growth model,it was found that the plasma density on the substrate surface decreased greatly after employing the substrate holder,which led to the decrease of the growth rate.Therefore,the new substrate holder was designed and optimized,and the diamond can always maintain high-speed and high-quality growth in the growth process.(3)The uniformity of substrate surface morphology: After three steps of repeated growth,the volume of the diamond enlarged by 7.12 times.After analyzing the surface morphology of diamond,it was found that with the lateral growth of the diamond,the temperature gradient will increase,which will affect the uniformity of surface morphology.In order to control the substrate temperature,the air layer was used to control the thermal conductivity of the substrate and adjust the non-uniform distribution of the substrate temperature.(4)The high-quality and high uniformity growth of multi large-size substrates: In order to improve the growth efficiency,the simultaneous growth of multiple large-area substrates was studied.The surface morphologies of the substrates were predicted by three-dimensional simulation,and the substrate holder and deposition chamber structure were modified by combining the prediction results.Finally,successfully expanded the size of each substrate to9 mm,and each substrate showed a high-uniformity growth morphology.