鄰近耦合效應對超薄金氧半電容深空乏穿隧電流之影響

Abstract

金氧半穿隧二極體因為具有深空乏區特殊的電特性，可以當作感測器使用。本篇論文主要探討鄰近耦合效應，強化此現象可以有效提高p型金氧半穿隧二極體的深空乏區穿隧電流。藉由增加被量測元件附近的浮接金氧半電容元件數目，或是藉由縮短它們彼此之間的距離，這兩個方法都可以強化蕭基位障調變機制，進而增益鄰近耦合現象，適合用來增加元件的工作電流。 n型金氧半穿隧二極體本身具有較高的穿隧電流，但是不適合做為感測器因為對元件周圍的少數載子濃度變化並不敏感；如果把p型金氧半穿隧二極體周圍的氧化層移除，穿隧電流會變得很小，但是光敏感性會變得非常強烈。這兩個現象來自於它們皆缺乏蕭基位障調變機制，前者是因為不具備蕭基位障所以會有較大的飽和穿隧電流，適合用於對周遭干擾絕緣、需要高工作電流的元件；後者是原本有蕭基位障但是因為移除氧化層的過程造成蕭基位障無法被調變引起的極小電流以及介電系數的改變引發的強化電場，可以用作需要高度光敏感性的感測器。 同時，在金氧半穿隧二極體中也可以測得負轉導現象，來自於少數載子的鄰近耦合效應。在TCAD模擬中可以看到電子的分布情況輔助所提的推測。該鄰近耦合效應可望將金氧半穿隧二極體用在製作非揮發性記憶體。

Metal-insulator-semiconductor (MIS) tunneling diode is a very promising sensor due to the maneuverability within the deep-depletion region in which the neighboring coupling effect between two adjacent devices is the major issue of concern in this thesis. To study the MIS deep-depletion tunneling current coupling phenomenon, a device pattern of one centric circle encircled by one or two surrounding rings was devised. It was found that central MIS(p) tunneling current, with the help of Schottky barrier height modulation mechanism, is enhanced merely by locating more floating MIS(p) structures nearby, or by shortening their relative distance. Such could again be observed under light exposure. MIS(n) structure was also fabricated for comparison. It was found, with the lack of Schottky barrier height modulation mechanism, tunneling current is greater and almost immune to light irradiance compared to MIS(p). Besides, MIS(p) with its edge oxide being removed was also conducted to abate its Schottky barrier height modulation capability. Significantly lower deep-depletion tunneling current and invulnerability to adjacent minority-carrier condition were therefore achieved. Surprisingly, it offered smaller saturation voltage and better photosensitivity. The negative transconductance behavior in MIS(p) structure owing to the inversion-charge-coupling effect assisted by TCAD simulation verification was studied. It turned out with the removal of Schottky barrier height modulation mechanism weakens that behavior and the gate injection takes over. Furthermore, the neighboring coupling effect is a potential candidate for the application in emerging nonvolatile memory.