Atomic layer deposition of boron-containing films using B2F4

Ultrathin and conformal boron-containing atomic layer deposition (ALD) films could be used as a shallow dopant source for advanced transistor structures in microelectronics manufacturing. With this application in mind, diboron tetrafluoride (B2F4) was explored as an ALD precursor for the deposition of boron containing films. Density functional theory simulations for nucleation on silicon (100) surfaces indicated better reactivity of B2F4 in comparison to BF3. Quartz crystal microbalance experiments exhibited growth using either B2F4-H2O for B2O3 ALD, or B2F4-disilane (Si2H6) for B ALD, but in both cases, the initial growth per cycle was quite low (≤0.2 A/cycle) and decreased to near zero growth after 8–30 ALD cycles. However, alternating between B2F4-H2O and trimethyl aluminum (TMA)-H2O ALD cycles resulted in sustained growth at ∼0.65 A/cycle, suggesting that the dense –OH surface termination produced by the TMA-H2O combination enhances the uptake of B2F4 precursor. The resultant boron containing films we...