Table A-Ill. Radial temperature profile polynomial coefficients for 5% inlet silane in krypton or 100% inlet silane. Temp., K 923 950 976 1002 1056 1161 c~ 0 -0.18 -0.30 -0.36 -0.40 -0.44 -0.74 c~1 7.411 11.959 14.623 16.122 17.726 29.978where ~i are the polynomial coefficients, Tcentral is the central thermocouple reading at 13 mm radius, and r/rchamber is the wafer radius divided by the chamber radius. The polynomial coefficients al are detailed in Tables A-I, A-II, and A-III for the process conditions used in polysilicon deposition experiments. The radial temperature profiles for the various gas mixtures were calculated by weighting the measurements of the pure gas species i by the mole fraction of i in the mixture.Direct measurement using SiH~ is not possible due to electrical shorting of the thermocouple leads during polysilicon deposition, and Kr ambient was used in only a single temperature measurement. Since the thermal conductivities of silane and krypton are relatively close to that of N2, these results were obtained by assuming that the temperature profiles in krypton and silane could be emulated using the measurements made with N2. This assumption was corroborated by a single measurement in krypton gas which gave a time-averaged central-to-edge temperature difference of 8.7 K (1062 K central temperature), close to the result in N2 of 7.8 K. REFERENCES A.ABSTRACT A rapid thermal anneal (RTA) process has been investigated in detail for the applications of emitter diffusion and TiSi2 anneals in an advanced double-polysilicon bipolar process. The significance of thin oxide at the emitter-polysilicon-to-silicon interface for a low thermal budget process using RTA is presented in this paper. A change in wafer loading temperature from 400 to 600~ at emitter polysilicon deposition increased the emitter resistance from 30 to 700 ~ for emitter diffusion using RTA at 1025~ for 30 s. In contrast, emitter resistance of wafers that went through diffusion in a furnace at 1000~ for 15 rain was insensitive to the wafer loading temperature at emitter polysilicon deposition. Such a large increase in emitter resistance for the RTA process is attributed to oxidation of the silicon surface during wafer loading at elevated temperatures at the emitter polysilicon deposition step. The interaction of RTA and subsequent heat cycles on the heavily doped polysilicon sheet resistance is discussed in the second section. Sheet resistance of arsenic-and boron-doped polysilicon increased by more than 50% when the wafers were annealed in a furnace at 800~ after the RTA emitter diffusion at 1050~ for 30 min. The reverse annealing was explained by the dopant deactivation from (i) segregation to grain boundaries and (it) return to equilibrium concentration from supersaturation and dopant precipitation. The bipolar process employs an RTA heat cycle at 850~ for 10 s to transform the C49 phase of TiSi2 to the low resistivity C54 phase. The short RTA cycle resulted in superior silicide morphology and low contact resistance at the interface be...