Polishing-pad-free electrochemical mechanical polishing of single-crystalline SiC surfaces using polyurethane-CeO2 core-shell particles
Polishing-pad-free electrochemical mechanical polishing of single-crystalline SiC surfaces using polyurethane-CeO2 core-shell particles
复制标题
DOI：
10.1016/j.ijmachtools.2016.11.007
复制
发表时间：
2017-03-01
影响因子：
14
通讯作者：
Ban, Kazuma
中科院分区：
文献类型：
--
作者：
Murata, Junji;Yodogawa, Koushi;Ban, Kazuma
报道了一种单晶 SiC 表面电化学机械抛光 (ECMP) 的新方法，与传统电子材料相比，该方法具有极高的机械和化学强度。该方法不使用抛光垫；它包括SiC表面的电化学氧化以及随后通过CeO2从聚氨酯-CeO2核壳颗粒中去除氧化物。核壳颗粒用于保持抛光板（阴极）和SiC晶片（阳极）之间的间隙，从而能够对惰性SiC表面进行有效的阳极氧化。该核壳颗粒由弹性聚氨酯核覆盖着小而软的CeO2颗粒磨料层组成，通过简单且低成本的工艺制备，可以在不使用抛光垫的情况下获得光滑的SiC表面。优化核壳颗粒中聚氨酯与CeO2的比例，以获得被壳颗粒完全覆盖的核颗粒，而不留下多余的CeO2颗粒。使用制造的核壳颗粒，传统的 CMP 工艺无法在不进行阳极氧化的情况下去除 SiC 表面。电流测量和X射线分析证实，抛光过程中连续偏压会因处理表面残留氧化膜而产生粗糙的SiC表面，而周期性施加偏压（其条件由氧化膜的理论生长速率和残余厚度决定）可减少划痕数量，并获得亚纳米粗糙度的光滑表面。所得的表面粗糙度值与利用传统磨削理论确定的计算值非常吻合。与使用胶体 SiO2 浆料的传统抛光工艺相比，所提出的方法显示出优异的抛光效率，且无需抛光垫。核壳颗粒的SEM观察表明，该颗粒对电极之间的强电场具有耐受性。
A novel method for electrochemical mechanical polishing (ECMP) of the single-crystalline SiC surface, which has extremely high mechanical and chemical strength compared to conventional electronic materials, is reported. The method does not employ a polishing pad; it comprises electrochemical oxidization of the SiC surface and subsequent removal of the oxide by CeO2 from the polyuretharie-CeO2 core-shell particles. The core-shell particles are used to maintain a gap between the polishing plate (cathode) and the SiC wafer (anode), which enables efficient anodic oxidation of the inert SiC surface. The core-shell particles, composed of the elastic polyurethane core covered with an abrasive layer of small and soft CeO2 particles prepared by a simple and low-cost process, can be used to obtain a smooth SiC surface without using a polishing pad. The ratio of polyurethane to CeO2 in the core-shell particles is optimized to obtain core particles that are fully Covered with the shell particles without leaving excess CeO2 particles. Using the fabricated core-shell particles, the conventional CMP process is unable to remove the SiC surface without anodization. While a continuous bias during polishing produces a rough SiC surface owing to the oxide film remaining on the treated surface, as confirmed by current measurements and X-ray analysis, a periodically applied bias, whose conditions were determined by the theoretical growth rate and residual thickness of the oxide film, reduces the number of scratches, and a smooth surface with sub-nanometer roughness is obtained. The obtained value of surface roughness is in good agreement with the calculated value determined using conventional grinding theory. Compared to a conventional polishing process with a colloidal SiO2 slurry, the proposed method shows superior polishing efficiency without the need for a polishing pad. SEM observation of the core-shell particles shows that the particles have durability against the strong electric field between the electrodes.