Gas and Liquid Flows in Chemical Vapor Deposition and Spin Coating

• Main Authors: Gong, Shih-Chin, 龔詩欽
• Other Authors: Chou, Fu-chu
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/20108395858707674838

博士 === 國立中央大學 === 機械工程學系 === 84 === Chemical vapor deposition (CVD) and spin coating are two important processes in the fabrication of semiconductor devices and integered circuits.This study, recognization that a better of these aspects of fabrication in very large scale integration ( VLSI) facilities and ultra large scale integration( ULSI ) facilities, addressed this issue. Chemical vapor deposition and spincoating processes are discussed in this study. The effects of wall cooling on the flow pattern and the uniformity ofdeposition in a rotating CVD reactor are examined. In the rotation-induced-flowregime, the wall cooling effect can reduce the size of vortex. The plug flow regime would exist at higher disk rotation rate for a cooled reactor wallthan that for an adiabatic reactor wall. When increasing the rotating rate ofthe disk, the effect of the walls'' cooling is significant. An underatanding of the flow characteristics of the recirculation zoneis critical in the designing a horizontal CVD reactor and in controlling thedeposition process. Therefore, the length of the recirculation zone of a central jet flowing into an enlarged chamber is studied. A correlation equationis found to predict the length of the recirculation zone when the expansion ratio is larger than 2. The correlation equation has been confirmed by theexperimental data with an expansion ratio 15.3, and agrees with the existingdata for an expansion ratio 2.6. This correlation equation may be used for the proper design of a CVD reactor with a high expansion ratio. Spin coating is utilized extensively in the microelectronics to forma thin uniform film of photoresist or polyimide on silicon wafers. During thisprocess, a small amount of liquid, typically in a form of solution with a volatilesolvent, is dispensed by a nozzle onto a high speed rotating disk, thereby convering the wafer''s entire surface. This disk is then accelerated to a higherspeed to sweep off the liquid. The solvent continues to evaporate and the film eventually dries. Reducing the amount of liquid dispensed is essential to costreduction since the photoresist and polyimide are quite expensive. It is foundthat after the spreading film covers the entire disk, the more liquid dispensedonto the wafer is useless. Restated, the amount of liquid dispensed can be reduced by controlling the dispensation time and/or increasing the dispensation rate. To our knowledge, no numerical study of wind shear effect on two- dimensional film thicknessdistribution over doughnut disks has been performed. Wind shear effect is moresignificant when the device feature shrink to submicron level. We developeda numerical method to predict the successiveliquid surface cintours on the rotating doughnut disks. Also, the results are compared with the experimental data. There are discrepancies between the experimental data and the present numerical results. We found that the airshear flow can not be approximated by Cochran''s solution, and it is causedmainly by the presence of a hub.