Metal/hydrogenated amorphous silicon/crystalline silicon hetero-structure with directional breakdown: A low-cost, high-density, diode array approach to PROMs

This thesis reports a directional breakdown behavior in metal/intrinsic a-Si:H/n c-Si structures. This discovery has potential to make high density, low cost programmable read only memory (PROM) devices. In the thesis different technologies of conventional PROM devices are given as comparison.;In this thesis we studied the process and characterization of a-Si:H material. The a-Si:H film is deposited using rf PECVD on an electrode driven substrate. Film quality is mainly characterized by PL. The film property is strongly affected by the processing parameters such as power, pressure and temperature. We can see the difference in film quality from the PL signal presented in this thesis. Substrate materials also play a big role in determining the film growth. A mixed phase of uc-Si, a-Si and a-Si:H with different bandgap can co-exists if film grows on glass or uc-Si substrate.;Devices fabricated under different conditions are given in this thesis. A 105 forward current gain is obtained after an electrical stress of large forward bias. Device computer simulation tool analysis of microelectronic and photonic structures (AMPS) is used intensively to help understanding the transport mechanism and guide our design. A model using carrier hopping through the defects states is used to explain the breakdown mechanism. Also demonstrated in this thesis, we can link the material property with device performance using AMPS program. The modeling work explained the space charge limited current due to electron trapping in the defect states and model the trend of thickness and defect density effect in the device before breakdown.;We also demonstrated in this thesis that device as small as 1 x 1 um 2 is able to be fabricated. This work builds up the evidence of making potential large array PROMs based on this technique. ECR PECVD is used to deposit SiOx as the field oxide. The process flow and device characteristic is given in the thesis.;In attempting to further reduce the cost of making PROMs, we explore possibility of making the device on glass substrate. Three different ways of making poly silicon n layer are discussed in the thesis as well as their conductivity, UV and X-ray diffraction measurement. Finally we report a success in making the device on LPCVD poly silicon substrate.