ITO 박막의 특성 개선을 위한 CMP 공정 파라메터의 최적화

Abstract

CMP process is effectively used to flat dielectric layer such as IMD, ILD, PMD and metal layer such as W, Al, Cu in order to perform multi layer structure of deep sub micron integrated circuit. It is also done to make various devices and new materials. Recently as speed of semiconductor gets higher and integration capacity gets bigger, multi-layer interconnection technique becomes important problem in sub micron process. Especially, decrease of wavelength related to the source of light is necessary to perform minute pattern in the process technique under 0.35㎛. As the wavelength decreases, resolution is improved but depth of focus decreases, which brings unflatize in multi layer process. There are two methods in the conventional process. The first method is to employ Etch-Back after making oxidation film with high liquidity, reflow, and then RP coating. The second method is heat treatment after spin coating of volatile macromolecule materials, SOG and reflow. But the method was only partial flatization and so it can not satisfy global flatization - technical requirement. As the aluminum wiring materials has been replaced by copper and wiring materials with low-K have been developed, the new process - CMP can flat globally. Since 1980 the method has been used by IBM. Chemical and mechanical process is introduced to get over these technical problems. CMP provides slurry particles whose size is hundreds of Å on the pad of macromolecule material attached to platen. It presses wafer carrier and polish the surface of wafer. Processed material presses elastic pad. Good corroded liquid and micro particle eliminates chemically. In the surface of pad, pressure and temperature gets higher. So chemical and mechanical processing makes flatization processing. Indium tin oxide (ITO) thin film is a transparent electrode, which is widely applied to solar battery, illuminators, optical switches, liquid crystal displays (LCDs), plasma display panels (PDPs), and organic light emitting displays (OLEDs) due to its easy formation on glass substrates, good optical transmittance, and good conductivity. ITO thin film is generally fabricated by various methods such as spray, CVD, evaporation, electron gun deposition, direct current electroplating, high frequency sputtering, and reactive DC sputtering. However, some problems such as peaks, bumps, large particles, and pin-holes on the surface of ITO thin film were reported, which caused the destruction of color quality, the reduction of device life time, and short-circuit. Chemical mechanical polishing (CMP) processis one of the suitable solutions which could solve the problems. CMP process has been widely used in semiconductor fabrication and microelectronics industry. CMP process must provide a high removal rate (RR) and good planarity through the simultaneous action of chemical dissolution with mechanical abrasion. CMP performances can be optimized by several CMP components such as equipment and consumables (pad, backing film and slurry). Among the above CMP components, slurry consumables and process parameters controlled by equipment are very important parameters in determining the removal rate and within-wafer non-uniformity (WIWNU%). In this study, the optimum process parameters and the influences of process parameters (slurry flow rate, polishing time, and table speed) were investigated for ITO-CMP with the sufficient removal rate and the good planarity. ITO-CMP was performed by change of de-ionized water (DIW) temperature in pad conditioning process. DIW with high temperature was employed in pad conditioning immediately before indium tin oxide (ITO) CMP. Removal rate, within-wafer non-uniformity (WIWNU%), and surface morphology of ITO thin film were investigated.