Fabrication Of Diamond Films By Laser-microwave Plasma Chemical Vapor Deposition

Diamond films have excellent application prospects in many high-tech fields such as high-density integrated circuit packaging materials,missile radome protective coatings,and electrochemical electrodes,due to its excellent mechanical,electrical,acoustical,optical and thermal properties.Based on the traditional microwave plasma chemical vapor deposition?MPCVD?system,this paper introduced a continuous laser with gaussian distribution to form a laser-microwave plasma chemical vapor deposition?LMPCVD?system for the preparation of CVD diamond films,whose optical effect and thermal effect were used to promote the progress of the precursor reaction and improve the quality of the CVD diamond film.In this paper,diamond films were deposited on Si?100?in CH₄-H₂ system by MPCVD and LMPCVD.We focused on the effects of methane concentration??c?,microwave power(p_mw),and laser power density?E?on the growth of the diamond films.Finally,the effects of laser introduction on diamond growth and its influencing mechanism were explored by comparing the experimental results of the two methods.In the MPCVD system,the effects of?c and pmw on the growth of diamond films were investigated.The content and crystallinity of the diamond phase decreased with the increase of?_c,and the residual stress of diamond films gradually changed from compressive stress to tensile stress.When?_c=1.5%and p_mw=800 W,the film growth rate R_G reached a maximum value of 0.51?m/h.With the increase of p_mw,the quality factor Q,hardness?H?and Young's modulus?M?increased and then decreased.When p_mw=800 W and?_c=1.0%,the maximum values of Q,H and M were reached,Q_max=96.5%,H_max=632 GPa,M_max=86 GPa.When p_mw=850 W and?_c=1.0%,the R_G reached the maximum value of 0.63?m/h.In the LMPCVD system,the effect of E and pmw on the growth of diamond films were investigated.With the increase of E,the morphology of diamond grains changed from triangle and square to nano shape and diamond content increased and then decreased.The property of the residual stress gradually changed from compressive stress to tensile stress and then to compressive stress.When E=40W/cm²,?_c=1.0%,and p_mw=750 W,the maximum values of R_G,Q,H and M were reached,while FWHM reached the minimum value,R_{G max}=0.378?m/h,H_max=91GPa,M_max=721 GPa,Q_max=100%,FWHM_min=4.2 cm^-1.According to the surface morphology,the coupling effect map was divided into three regions of A,B and C,which corresponding to the crystallization zone,the transition zone and the nano zone respectively.At the same p_mw,R_G and Q gradually increased with the increase of E,and the excessive E value caused it to decrease.Comparing the experimental results of diamond films deposited by MPCVD and LMPCVD,it was found that the introduction of low power density laser forms a higher temperature plasma,promotes the precursor reaction process,reduces non-diamond components such as graphite and amorphous carbon,and improves the quality of the diamond film.While gradually increasing the power density of the laser,the diamond?111?and?100?faces were successively etched by laser,resulting in the growth of the nanodiamond.