The Critical Process Study Of The Gaas/algaas Dual-band Qwip Detector

As the representative of the third generation infrared focal plane of thedevice,based on two different types of photodiodes stacking vertically which inresponse to two different wavelengths,the dual-band infrared detector is well knownfor their highly integration,reliability,ultra-high-speed and miniaturization.Thedual-band QWIP detector processed are significantly different from the conventionalmicroelectronic processing and micromachining.The micro-mesa lithography andetching process are needed in the structure manufacture,and the isolation of the micromesa was necessary in the array peocess.This project was finished cooperating with the institute of Semiconductors,Chinese Academy of Sciences,mainly responsible for the processes.In thisresearch,the critical processes of the chip manufacturing were studied.The ICPetching parameter suiTab.le for the chip manufacturing. was found after many ICPetching experiments,which is with appropriate etching rate,highly etching ratio androughly side wall.The rough surface was obtained after appling the optimizationlithography parameters in the lithography process.This optimization was also appliedto the metal electrode pattern,and met the requirement of pattern making under thedeep trench.The major onnovative achievements are as follows:(1)The relationship between the step height and the photoresist thickness wasdiscussed and numerical described. Based on the description of Beer model about thelight absorption coefficient, the diagram of different light transmittance at differenttime was analysed,and the underexposure of the deep trench was explained. Reasonsfor the light transmittance change at different time were explained, and the lightabsorption coefficient related with the photoresist thickness.On this basis, thelithography processes were optimized. The graphics with narrow line-width under thedeep step on the wafer was obtained.The lithography process was re-optimized andapplied to the metal electrode process.The integrity of the metal pattern wasmaintained and laid a good foundation for the matalic process through the metalbridge.(2) The size effect of the micro mesa etching,the the size gain and particle scattering model was also proposed to explain the fact that the slope angle of themicro mesa coatingwith large photopersist thickness varies apparently. On thebasis,the influence of different etching parameters were also studied.The fact wasexplained on two aspects，which contains dry etching mechanism and the effect ofICP etching parameters to the physical and chemical processes.The ICP etchingparameter suiTab.le for the chip manufacture was obtained after many ICP etchingexperiments based on the previous research,and has good uniformity and roughmorphology.