Novel Chemical Mechanical Polishing/Plasma-Chemical Vaporization Machining (CMP/P-CVM) Combined Processing of Hard-to-Process Crystals Based on Innovative Concepts

Abstract

In this research, we aim to establish systematic knowledge of ultraprecision processing of hard-to-process crystal wafers for next-generation "green devices", and design and develop a high-efficiency, high-quality process to contribute to an early commercialization of SiC, GaN, and diamond-based devices demanded for a low-carbon society. Upon designing an ultrahigh-precision process for hard-to-process materials, we divided the process into two steps: a pretreatment step and a finishing step. In the pretreatment step, a pseudoradical area was formed by introducing ultrafine defects to control the surface condition suitable for finishing. In the finishing step, we attempted to combine the closed-chamber chemical mechanical polishing (CMP) and plasma-chemical vaporization machining (P-CVM) methods. To evaluate the concept of the second step, a fundamental study needed to design and prototype the machine was conducted. As a method of creating a pseudoradical area, femtosecond (fs) laser irradiation and coarse processing (grinding), which leaves a crystallographically disordered layer, were considered. Microindentation test, cross-sectional transmission electron microscopy (TEM) observation, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED) were used to confirm the 404 Sensors and Materials, Vol. 26, No. 6 (2014) pseudoradical area at the uppermost surface. Also, we studied the characteristics of the pseudoradical substrates subjected to CMP and P-CVM. P-CVM showed an increased processing rate for the pseudoradical substrates having microdefects. It will be necessary to optimize the degree and depth of crystallographic disorder in the pseudoradical area in the future. On the basis of the results presented here, we are starting to prototype the innovative CMP/P-CVM combined processing machine, which can selectively flatten the nanotopographies of hard-to-process materials by conducting CMP and P-CVM while continuously creating a pseudoradical area through an in situ physical effect such as polishing.

Rapid Estimation of Removal Rate of Chemical Mechanical Polishing of Gallium Nitride Substrate by Quantitative Diagnosis of Cathodoluminescence Images

“…The removal rate of CMP process is generally speculated to be higher for the polishing of the rougher and/or defected crystal surface than that of the smoother and/or defect-less one. [35][36][37][38] Therefore, there was possibility of reduction of removal rate with progress of CMP process. For further precise analysis, it may be necessary to involve a decay of the removal rate during the CMP process in consideration.…”

Surface Morphology Evolution Induced by Multiple Femtosecond Laser Ablation on 4H-SiC Substrate and Its Application to CMP

“…This was considered that fs laser-ablated periodic rippled structures had poor crystallinity due to oxidization and the amorphous layer. 40,41 The effect of rippled structures on chemical mechanical polishing (CMP).-To investigate the effect of fs laser irradiation on chemical mechanical polishing (CMP), polishing experiment was carried out for lapped C-face of single crystal 4H-SiC substrates. An original (ORI) SiC substrate and the substrate ablated in Cross Scanning Mode (CSM) were simultaneously polished in CMP process for 26 mins.…”

Approaches to Sustainability in Chemical Mechanical Polishing (CMP): A Review

“…This method is reported to be able to improve the MRR by facilitating the oxidation of SiC substrates in nitrogen (N) and oxygen (O 2 ) atmospheres. To improve the MRR of hard-to-process crystals, Doi et al [107] proposed a process method that combines plasmachemical vaporization machining (P-CVM) and CMP with a bell-jar-type CMP machine.…”