Formation of TiN_x ohmic contacts to InGaAs/InP by means of a load-locked integrated process

The authors have demonstrated the viability of forming an ohmic contact to InGaAs/InP structures by means of a load-locked integrated process. The wafer was loaded into a rapid-thermal low-pressure metallorganic chemical vapour deposition (RT-LPMOCVD) reactor and was exposed to a sequence of processes which led to the formation of an ohmic contact. After in situ cleaning of the wafer through a thermal cycle at 500 degrees C under a flow of tertiary-butylphosphine (TBP), which provided the free hydrogen needed for a mild etching of the surface, a layer of silicon oxide (SiO_x) was deposited onto the InGaAs/InP via a rapid thermal cycle (500 degrees C, 30 s) in a low-pressure O₂ and 2% diluted SiH₄ chemical vapour deposition (CVD). Dry etching of 50 mu m wide contact windows was carried out using a contact stainless steel stencil mask, after unloading the wafer from the RT-LPMOCVD reactor chamber via the load-lock and loading it into an electron cyclotron resonance (ECR) dry etching chamber. In the final step the wafer was returned through the load-lock to the main chamber and a TiN_x layer was selectively deposited into the via-holes and processed to provide an ohmic contact to the InGaAs/InP substrate. This work provides a solid demonstration of the feasibility of the single-wafer integrated process (SWIP) as an approach to replace the batch process traditionally used for InP-based optoelectronic devices.