Advanced metallization and applications to large area active matrix arrays and polysilicon thin film transistors

This dissertation investigates and develops novel metallization processes for the fabrication of active matrix arrays of polysilicon devices. Particular emphasis is placed on metallization processes suitable for application to the new field of active matrix organic light emitting diode (AMOLED)) display technology. Specifically, this dissertation includes: (1) the development of a robust metallization suitable for AMOLED display fabrication; (2) determines the thermal and chemical stabilities of nickel and cobalt silicide and incorporates a silicidation process into an AMOLED display fabrication sequence; and (3) develops a process for fabricating the first polysilicon devices and circuits on stainless steel substrates, for possible use in an AMOLED process.; A study of bilayer metal films (aluminum with titanium, cobalt or nickel) exposed to a variety of annealing conditions was conducted in order to develop interconnect metallizations for AMOLED and other large area array applications. This resulted in the development and adoption of a successful nickel-aluminum bilayer metallization that succeeded in suppressing hillock formation, formed ohmic contacts to ITO, and proved an effective etchant stop to aqueous hydrofluoric acid. The interfacial reactions of the various bilayers were examined and used to explain the behavior of the different films.; Cobalt and nickel silicides were tested for their usefulness in a low temperature silicidation process that could be incorporated into a process sequence for fabricating a large area array of polysilicon devices. The relative thermal and chemical stabilities of nickel and cobalt silicides were examined and compared, and the nickel silicide was chosen as the better candidate, proving to be stable when exposed to a variety of chemistries and was successfully incorporated into the AMOLED display process flow. The thermal and chemical reactions involved were investigated and discussed with respect to the relative advantages of these two silicidation processes.; The first polysilicon devices and circuits were fabricated on steel substrates. This use of steel substrates offers the possibility of a flexible substrate having a high thermal budget compatible with an inexpensive polysilicon process. This work on microelectronic processing on stainless steel also creates the possibility of an inexpensive roll-to-roll manufacturing sequence. The processes for successfully fabricating polysilicon devices and circuits on steel substrates are detailed, and the effects of the steel substrate on device performance are derived and demonstrated.