| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 106 === The thesis studies the fringing field carrier coupling effect in the view point of capacitance characteristics. A two capacitance states operation is proposed and demonstrated to have memory behavior.
It is known that the carriers of adjacent devices would interfere and coupling with each other if the distance between them is short. The electrical characteristics of an inner MOS circle with an outer MOS gate ring was measured and studied with three different minority carrier coupling conditions. The I-V and C-V relations was measured with the outer MOS gate ring biased under inversion region (near flat band), strong inversion region, and accumulation region, respectively. When the outer MOS gate ring was under weak inversion region (negative but near flat band bias), the amount of minority carriers was the main factors of minority carrier coupling effects. But when the outer MOS gate ring was under strong inversion region (positive bias), the energy barrier between inner MOS circle and outer MOS gate ring became an important factor since the electron energy level of outer gate decreased. The two factor competes and the energy barrier between inner MOS circle and outer MOS gate ring was the dominant factor when outer gate ring was under strong inversion region. When outer ring was under accumulation region, injection tunneling currents occurred since the oxide was very thin. The injection current sensed by inner MOS circle was strongly disturbed by the AC measurement of capacitance and caused noise in C-V relations. A frequency dispersion behavior was also observed with outer gate ring biased under strong inversion region.
It was observed that floating gate and grounded gate would have quite different impact on carrier coupling effect. The carriers under floating was free to move and respond to AC signals while those under grounded gate was confined by determined electric field and energy level. The high capacitance of inner MOS circle (Cinner) of floating gate can be considered as one state (S1), while the low Cinner of grounded gate can be considered as another state (S2). It was measured that Cinner changed quite fast from S1 to S2, while some transient time was needed for Cinner to change from S2 to S1. This can be seen as memory behavior. Several factors that could affect the transient time were evaluated and explained for future works and designs.
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