BORON DOPING OF SILICON USING COALLOYING WITH ALUMINUM

We present a new technique for boron (B) doping of silicon. In this le tter we show that a B doping profile of more than 2 mu m thickness wit h a maximum active doping concentration of 3x10(19) cm(-3) can be form ed by a fast (<1 min) alloying process at a temperature of 850 degrees C. Thick-film aluminum is used to obtain an alloying and epitaxial re growth process in accordance with the Al-Si phase diagram. The atomic concentration profile of the B- and Al-doped Si layer was determined b y secondary ion mass spectrometry. The active doping concentration was measured with an automatic electrochemical capacitance/voltage profil er. By the addition of B to the Al paste, the epitaxially regrown laye r is doped with B and Al to the solid solubility of these elements in Si at the particular regrowth temperature. The applicability of this f ast low temperature B doping process in Si solar cell processing is di scussed. (C) 1994 American Institute of Physics.