Research On High-efficiency And Low-damage Processing Of Sapphire

Sapphire crystal is used in a wide range of fields including optics, electronics, and temperature sensing etc. owning to its excellent optical, physical and chemical properties such as high hardness, high melting point, good optical transparence, good electric insulation, high heat conductivity and favorable chemical stability. Along with the high demand for sapphire production, it puts forward higher request for profile accuracy and surface. Traditional sapphire process including loose abrasive lapping, chemical mechanical polishing has unavoidable shortages such as low efficiency, high price, unstable process, which becomes the main obstacles of wide sapphire application. Therefore, it is necessary to research the novel high-efficiency and low-damage machining process of sapphire.Aiming at improving sapphire surface quality and machining efficiency, this paper proposed new lapping process which fixed abrasive lapping with diamond lapping tool and the mechanical chemical lapping with fixed abrasive mechanical chemical polishing tool. The main research contents and results of this paper are as following:(1) This paper proposes the fixed abrasive lapping technology for sapphire and analyzed the principle of the technology. The dressing method for fixed abrasive lapping tool is developed. Different diamond lapping tools with different bonds and grain sizes for sapphire lapping were developed in this paper. The material removal rate (MRR) and surface quality are evaluated to investigate the lapping performance of tools.(2) This paper uses the taper lapping and polishing technique to directly observe subsurface damage of lapped coatings, and the categories and the caused reasons were concluded and analyzed. The relationship between abrasive size and subsurface damage layer depth is studied.(3) In order to solve the shortage of chemical mechanical polishing, this paper proposes the fixed abrasive mechanical chemical polishing technology for sapphire which remove material by combination of mechanical action and chemical reaction in the polishing process. The Fixed-Abrasive-Chemical-Mechanical-Polishing (FACMP) tool for sapphire and dressing method are developed. The polishing performance of the FACMP tools were evaluated through lapping experiment.(4) Aiming at the targets of increasing machining efficiency and decreasing surface/subsurface damage of sapphire, the new process which combines fixed abrasive lapping technology and fixed abrasive mechanical chemical polishing technology is proposed:the W20 diamond tool is used first to remove most of the machining allowance in coarse grinding stage; then in semi-fine lapping stage, the W7 diamond tool is used to remove subsurface damage layer induced by previous grinding process; finally, FAMCP tool used to get nanometer order surface roughness of wafer...