The choice of surface treatment prior to silicon wafer bonding is crucial both for the reliability of the bonding process and the electrical properties of the bonded structure. In the case of silicon direct bonding for manufacturing of buried electrical junctions, the bonding step is particularly critical for accurate and reproducible results. In this work, the attraction between HF-etched surfaces and the effect of a following water rinse were investigated by studying the bonding spontaneity, velocity of the initial bonding wave, and the electrical properties of the bonded junctions. Spontaneous bonding occurred when no subsequent water rinse was made after the HF-etch, while water-rinsed wafers dia bond only with the help of an applied pressure and also ended up with more voids. The highest contact wave velocity, together with good electrical properties, was obtained for surfaces treated in a 10% solution of BF in water, without subsequent water rinse. For unipolar bonded junctions annealed at 600-degrees-C, no influence of the bonded interface was found on the electrical characteristics. In contrast, samples annealed at 800-degrees-C exhibited slightly nonlinear current vs. voltage characteristics and a larger dynamic resistance. For water-rinsed samples, annealed at 800-degrees-C, the dynamic resistance showed a larger spread, indicating a lower reproducibility as compared to nonrinsed samples.