臺灣博碩士論文加值系統

傳統的金屬-氧化物-半導體場效應電晶體(MOSFET)一直存在著所謂的波茲曼統治(Boltzmann tyranny)的限制，使得電晶體在室溫下至少需要60mV/decade的閘極電壓變化才能從關閉狀態切換至導通狀態。這導致了金氧半場效應電晶體的工作電壓無法進一步的縮小，進而限制了MOSFET功率消耗也無法加以縮小。為了減少或消除所謂的Boltzmann tyranny的限制，在電晶體的閘極串聯一個負電容是一個可行的方法。在理論及實驗上已經證明這個方法可以有效地將次臨界擺幅(Subthreshold Swing，或稱為次臨界斜率(subthreshold slope).)降低至60mV/decade以下。
通常負電容是利用鐵電材料來製作，這是因為鐵電材料具有極化電荷所造成的。部分的有機材料也具有鐵電特性，在本研究中我們採用聚偏二氟乙烯(polyvinylidene difluoride，簡稱為PVDF)為絕緣層之金屬-絕緣層-金屬(metal-insulator-metal, MIM)結構的負電容。
由於負電容並不容易以一般的量測儀器量得，故在本篇論文中，我們嘗試研究將正電容與負電容分別串聯在金氧半場效應電晶體的閘極來量測其次臨界斜率並互相比較，透過次臨界斜率的改善來確認負電容的存在。而本篇論文所使用的電晶體為市售的金氧半場效應電晶體，其編號為HCF4007UBE。依據我們實驗所得的結果，使用PVDF為絕緣層的負電容在串聯於金氧半場效應電晶體閘極後，確實可降低金氧半場效應電晶體的次臨界斜率。

Conventional metal-oxide-semiconductor field-effect transistor (MOSFET) has been facing a fundamental limit called Boltzmann tyranny, which is a result of Boltzmann distribution of electrons at the source/channel interface, making at least a gate voltage change of 60 mV/decade at room temperature is required to switch the transistor from off state to on state. This limits the operating voltage of MOS FETs being scaled down further, and restraining the power dissipation in MOS FETs from becoming less. One possible way of eliminating the Boltzmann tyranny is to use a negative capacitance capacitor connected to the transistor gate in series. It has been proven both theoretically and experimentally that a serially connected negative capacitance capacitor to MOSFET transistor gate can effectively reduce the subthreshold swing to below 60 mV/decade.
Usually, negative capacitance capacitor can be fabricated by using a ferroelectric dielectric layer because of the existence of polarization charge inside the ferroelectric dielectric. It is noted that some of the organic materials are also ferroelectric in nature. In this wrok, we adopted an organic material polyvinylidene difluoride (PVDF) as the insulator layer of the negative capacitance capacitor with metal-insulator-metal (MIM) structure
Since negative capacitance is not easy to measure by using common measuring equipment, we try to investigate the negative capacitance effect by comparing the effect of connecting a capacitor with either normal capacitance or negative capacitance in series with the gate of a MOSFET and checking the subthreshold slope changes in this work.
Commercially available MOSFETs HCF4007UBE are purchased directly from vendors and are used in this work. From our experimental results, it is found that a negative capacitance with PVDF dielectric can truly reduce the subthreshold slope of the MOSFETs.

目次

摘要 …………………………………………………………………………………i
Abstract ……………………………………………………………………………ii
目次 …………………………………………………………………………………iv
表目次 ………………………………………………………………………………v
圖目次 ……………………………………………………………………………vi
第一章　緒論 ……………………………………………………………………… 1
　1-1　研究背景…………………………………………………………………… 1
　1-2　研究動機…………………………………………………………………… 2
第二章　文獻回顧 ………………………………………………………………… 5
　2-1　波茲曼統治………………………………………………………………… 5
　2-2　負電容效應………………………………………………………………… 6
2-3　聚偏二氟乙烯(polyvinylidene difluoride, PVDF)………………………… 6
第三章　實驗材料及步驟 ………………………………………………………… 9
　3-1　實驗材料…………………………………………………………………… 9
　3-2　實驗流程…………………………………………………………………… 9
　 3-2-1　PVDF電容製作 ……………………………………………………… 10
3-2-2　元件特性量測 …………………………………………………………10
第四章　結果與討論 …………………………………………………………… 17
第五章　結論及未來工作 ……………………………………………………… 27
參考文獻 ………………………………………………………………………… 28
　


表目次

表 1-1 文獻中採用鐵電介質負電容改善場效應電晶體之次臨限擺幅之比較… 4
表 3-1場效應電晶體HCF4007UBE之特性 ……………………………………… 12

圖目次

圖 1-1 MOSFET定電場微縮規…………………………………………………… 4
圖 2-1 鐵電材料的P-E遲滯曲線 ………………………………………………… 7
圖 2-2 鐵電材料的U-P關係曲線………………………………………………… 7
圖 2-3 PVDF分子結構圖 …………………………………………………………8
圖 3-1 本實驗之有效電路圖………………………………………………………13
圖 3-2 場效應電晶體HCF4007UBE之功能圖及接腳圖 ………………………14
圖 3-3 本實驗的電性量測示意圖…………………………………………………15
圖 3-4 電晶體閘極串接電容的電性量測示意圖…………………………………16
圖 4-1 原始電晶體之 圖……………………………………………………19
圖 4-2 原始電晶體之 圖……………………………………………………20
圖 4-3 原始電晶體串聯正電容之 圖………………………………………21
圖 4-4 原始電晶體串聯正電容之 圖………………………………………22
圖 4-5 原始電晶體串聯PVDF電容之 圖…………………………………23
圖 4-6 原始電晶體串聯PVDF電容之 圖…………………………………24
圖 4-7 當 時電晶體有無串聯電容之 圖…………………………25
圖 4-8 當 時電晶體有無串聯電容之 圖…………………………26

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