Hybrid Amorphous and Polycrystalline Silicon Devices for Large-Area Electronics

Distinct features of amorphous and polycrystalline silicon are attractive for large-area electronics. These features can be utilized in a hybrid structure which consists of both amorphous and polycrystalline silicon materials. For example, an extension of active matrix technology is the integration of peripheral drivers for the improvement of reliability, cost reduction and compactness of the packaging for large-area electronics. This goal can be approached by a combination of amorphous silicon pixel switches and polysilicon drivers. A monolithic fabrication process has been developed based on a simple modification of the amorphous silicon transistor process which uses selective area laser crystallization. This approach allows us to share many of the process steps involved in making both the amorphous and polysilicon devices. Another example of the hybrid device structure is a self-aligned amorphous silicon thin film transistor with polysilicon source and drain contacts. The advantages of the self-aligned transistor are reduction of the parasitic capacitance and scaling down of the device dimension. With a selective laser doping technique, self-aligned and short-channel amorphous silicon thin film transistors have been demonstrated.