热管理用3英寸硅衬底金刚石薄膜的制备

Preparation of 3-inch Diamond Film on Silicon Substrate for Thermal Management

金刚石膜材料用作GaN电子器件散热器具有巨大潜力,低应力、大尺寸、高质量、原子级光滑表面的金刚石膜层是GaN器件的整体传热能力提升的关键。本研究提出了一种用于3英寸(1英寸=2.54 cm)硅衬底多晶金刚石薄膜的生长和晶圆级抛光技术,用以实现大尺寸金刚石膜材料在散热器方向上的应用。首先对微波谐振腔内的等离子体进行多物理场自洽建模,通过仿真模拟技术分析2.45 GHz多模椭球谐振腔微波等离子体化学气相沉积(Microwave plasma chemical vapor deposition,MPCVD)装置沉积大尺寸金刚石薄膜的可行性,并优化生长工艺参数。然后对金刚石薄膜进行研磨抛光处理,以满足GaN器件的键合需求。模拟结果表明,输入相同的微波功率,腔室压强增大导致等离子核心电子和原子H数密度增加,但径向分布均匀性变差。在优化的工艺条件下沉积了金刚薄膜。实验结果表明,金刚石薄膜厚度不均匀性为17%。较高的甲烷浓度导致金刚石晶粒呈现以(111)晶面为主的金字塔形貌特征,并伴有孪晶的生成。Raman光谱中金刚石一阶特征峰半峰全宽(Full width at half maximum,FWHM)为7.4 cm^(−1)。抛光后表面粗糙度达到0.27 nm,硅衬底金刚石薄膜平均弯曲度为13.84μm,平均内应力为−40.7 MPa。采用上述方法,成功制备了大尺寸、较高晶体质量、低内应力、原子级光滑表面的硅衬底金刚石晶圆。

The diamond film material holds great potential as a heat sink for GaN electronic devices.The diamond film layer with low stress,large dimensions,high quality,and an atomically smooth surface is crucial for enhancing the overall heat transfer capacity of GaN devices.This study presents a technique for growing and polishing polycrystalline diamond films on 3-inch(1 inch=2.54 cm)silicon substrates to facilitate the use of large-sized diamond film materials in radiator applications.Firstly,the study carries out multi-physical field self-consistent modelling of plasma in a microwave resonator.It then analyses the feasibility of depositing large diamond films using a microwave plasma chemical vapour deposition(MPCVD)device with a 2.45 GHz multi-mode ellipsoid resonator through simulation technology.The growth process parameters are optimized accordingly.After that,the diamond film is polished to meet the bonding requirements of GaN devices.The simulation results show that under the same microwave power input,the increase of chamber pressure leads to the increase of number density of plasma core electrons and H atoms,but the uniformity of radial distribution becomes worse.Diamond film is deposited under optimized conditions and mensurates that the thickness inhomogeneity of diamond film is 17%.In this process,methane at high concentration leads to pyramidal morphology of diamond grains dominated by(111)planes,accompanied by formation of twins.Full width at half maximum(FWHM)of the first-order characteristic peak of diamond in Raman spectrum is 7.4 cm^(−1).After polishing,the surface roughness reaches 0.27 nm,the average bending degree of diamond film on silicon substrate is 13.84μm,and the average internal stress is−40.7 MPa.Silicon substrate diamond wafers with large size,high crystal quality,low internal stress and atomically smooth surface are successfully prepared by the above method.