D. Nagel et al., RAPID THERMAL-DIFFUSION OF ALUMINUM IN SILICON AND ITS INTERACTION WITH PHOSPHORUS, Applied physics A: Materials science & processing, 60(1), 1995, pp. 61-65
Aluminum diffusion profiles in silicon were produced under rapid therm
al processing conditions using a Si-sandwich structure to avoid losses
of aluminum by reaction with the quartz reactor. The impact of phosph
orus on the diffusion behaviour of aluminum was investigated by predep
osition of P into Al-diffused wafers and vice versa. Dopant profiles w
ere determined by SIMS (Secondary-Ion-Mass Spectroscopy), electrochemi
cal CV- and SRP (Spreading Resistance) analysis. The resulting profile
s after Al predeposition at 1293 K exhibit high Al-surface concentrati
ons up to the solid solubility limit of about 2 x 10(25) m(-3). It is
shown that phosphorus has a great influence on the drive-in behaviour
of Al, leading to an accelerated Al diffusion in front of the P profil
e (enhanced Al diffusion caused by self-interstitial supersaturation)
and an ''up-hill migration'' of Al in the high-concentration regime, w
hich can be explained by field-assisted diffusion. A strong retardatio
n of aluminum diffusion combined with concentrations well above the so
lid-solubility limit was observed during the Al predeposition into P-d
iffused wafers.