关键词: MPCVD, 金刚石, 拉曼光谱, 金属化, 热导率

Abstract: To investigate the effects of diamond crystal quality and metallization processes on thermal conductivity, this study adopted Microwave plasma Chemical Vapor Deposition technology to prepare diamond films with different crystal qualities by regulating methane concentration and growth temperature. Diamond-copper clad heat sink substrates were fabricated via a combination of two metallization processes (magnetron sputtering and AgCuTi high-temperature vacuum brazing) followed by electroplating copper. Characterizations were performed using a white-light interferometer and Raman spectroscopy, while mechanical and thermal properties were evaluated via pull-out tests and a laser flash apparatus (LFA).Samples synthesized at a low growth rate (2.14 μm/h) exhibited low defect and impurity contents, achieving a thermal conductivity of 1 742.59 W/(m·K). As the growth rate increased, the density of grain boundaries, voids, and other defects rose, leading to a gradual reduction in thermal conductivity to 1 156.70 W/(m·K). Increased surface roughness of diamond was found to enhance the bonding strength of the metal layer; the bonding strength via AgCuTi brazing (maximum 3.72 MPa) was superior to that of magnetron sputtering (maximum 2.51 MPa). The influence of metallization on thermal conductivity depends on metal layer thickness, interfacial bonding quality, and interfacial thermal resistance. Notably, the thermal conductivity of samples processed by magnetron sputtering decreased from an initial 1 518.07 W/(m·K) to 1 334.37 W/(m·K), showing a smaller reduction magnitude, which is more favorable for fabricating high thermal conductivity diamond-copper clad heat sink substrates.

Key words: MPCVD, Raman spectroscopy, metallization, thermal conductivity