For the first part of this paper, several nitrogen(N2) purge experiments have been performed on a200-mm SMIF Pod full of bare silicon wafers. Vari-ous N2 inlet flow rates are used to understand thechanges in oxygen (O...For the first part of this paper, several nitrogen(N2) purge experiments have been performed on a200-mm SMIF Pod full of bare silicon wafers. Vari-ous N2 inlet flow rates are used to understand thechanges in oxygen (O2) and moisture (H2O) concen-trations with time. As expected, it is found that asthe N2 flow rate increases, the O2 and moisture con-centrations inside the Pod decrease. Initially, thereduction in O2 and moisture concentrations is veryrapid (convection dominated), and slows down atlower concentrations and becomes diffusiondominated. The leak back rate of O2 and moistureinto the Pod was also analyzed by measuring O2 andmoisture concentrations without N2 flow into thepod, and with a trickle charge (very slow flow) ofN2. It was noticed that the leak back rates of O2 andmoisture is fast during the initial stages of retention,and slows down when the O2 and moisture concen-trations reach higher levels. With trickle charge ofN2, it is found that the O2 and moisture concentra-tions inside the Pod can be maintained at very lowlevels for a long time.In the second part of the paper, the effects ofN2 purge on limiting the growth of native oxides areexplored. The particular application of extending theallowable HF Poly deglaze to Tungsten Silicide depo-sition queue time is analyzed. Extension of the al-lowable queue time provides two benefits. First,utilization of upstream wafer HF cleaning equipmentis improved due to reduced dependence on an idledownstream deposition chamber. Second, HF re-cleaning is eliminated. Increased exposure duringHF re-cleaning results in residues at the Polysiliconto Tungsten Silicide interface which later causeblocked etch (reduced yield). It is concluded thatas a result of the N2 purge, the queue time betweenHF deglaze and DCS deposition can be increasedwithout any negative impact resulting from nativeoxide growth.展开更多
文摘For the first part of this paper, several nitrogen(N2) purge experiments have been performed on a200-mm SMIF Pod full of bare silicon wafers. Vari-ous N2 inlet flow rates are used to understand thechanges in oxygen (O2) and moisture (H2O) concen-trations with time. As expected, it is found that asthe N2 flow rate increases, the O2 and moisture con-centrations inside the Pod decrease. Initially, thereduction in O2 and moisture concentrations is veryrapid (convection dominated), and slows down atlower concentrations and becomes diffusiondominated. The leak back rate of O2 and moistureinto the Pod was also analyzed by measuring O2 andmoisture concentrations without N2 flow into thepod, and with a trickle charge (very slow flow) ofN2. It was noticed that the leak back rates of O2 andmoisture is fast during the initial stages of retention,and slows down when the O2 and moisture concen-trations reach higher levels. With trickle charge ofN2, it is found that the O2 and moisture concentra-tions inside the Pod can be maintained at very lowlevels for a long time.In the second part of the paper, the effects ofN2 purge on limiting the growth of native oxides areexplored. The particular application of extending theallowable HF Poly deglaze to Tungsten Silicide depo-sition queue time is analyzed. Extension of the al-lowable queue time provides two benefits. First,utilization of upstream wafer HF cleaning equipmentis improved due to reduced dependence on an idledownstream deposition chamber. Second, HF re-cleaning is eliminated. Increased exposure duringHF re-cleaning results in residues at the Polysiliconto Tungsten Silicide interface which later causeblocked etch (reduced yield). It is concluded thatas a result of the N2 purge, the queue time betweenHF deglaze and DCS deposition can be increasedwithout any negative impact resulting from nativeoxide growth.
