标题: 动态临界电压金氧半电晶体之特性及可靠性研究
A study on the characteristics and reliability of dynamic threshold MOSFETs
作者: 李耀仁
Yao-Jen Lee
黄调元
赵天生
Tiao-Yuan Huang
Tien-Sheng Chao
电子研究所
关键字: 动态临界电压;可靠性;次临界摆幅;逆向萧基位能障;(111);负偏压温度不稳定效应;dynamic threshold voltage;reliability;subthreshold swing;reverse schottky barrier;(111);NBTI
公开日期: 2004
摘要: 在本論文中,吾人先讨論了在不同闸极材质和厚度下的nMOSFETs。在利用动态臨界电压的模式下操作,吾人发现所有在动态臨界电压模式下操作的元件,不管其厚度或闸极材质,其臨界电压皆趋近于0.7V,和厚度或闸极材质无关。这是由于基底效应被消除的原因。而且其臨界电压和次臨界摆幅的公式亦被提出來解释此特别的现象,次臨界摆幅的模拟结果亦同时被提出。接下來,吾人将探讨制作在SOI 晶片上的pMOSFETs,且操作在动态臨界电压模式下,对不同的结构的闸(T 型或H 型)且在不同温度下的热载子效应。操作在动态臨界电压的模式下,在可靠性测量以后,臨界电压的偏移量会降低,但是其最大的转导和驱动电流在室温下确有更惡化的趋势。特别是T 型结构。操作在动态臨界电压模式下的转导放大效应和T 型结构下的电位不均匀是被认为造成T型闸极元件更加惡化的原因。
将逆向的Schottky 位能障制作在动态臨界电压电晶体的基底接触点上,使其可以操作在高电压和高温下,亦在本論文中讨論。藉着这种制作在基底接触点的Schottky 位能障,动态臨界电压电晶体可以操作在高电压下,且高温下亦呈现出理想的次臨界摆幅值,较低的臨界电压和较大的驱动电流。另一方面,这种结构的pMOSFETs 亦在本論文中讨論,而且操作动态臨界电压模式下的NBTI 的特性亦被首次讨論。因为一般的p 型动态臨界电压电晶体仅能操作在-0.7V 以下,以
避免基底和源极间的接面二极体的启动。另一方面,值得注意的是,在NBTI 的量测以后,操作在动态臨界电压模式的pMOSFETs,其臨界电压的偏移量有大幅下降的趋势。
此外,在附錄中,吾人亦对pMOSFETs 不同的区域布植不同剂量的氮離子,进而研究NBTI 的效应。高剂量的氮離子,不論是布植在通道或是源极/汲极的延伸,皆会造成严重的NBTI 效应。而且本論文亦研究动态NBTI 和基板热载子效应。大量的氮離子布植不仅会造成严重的NBTI 效应且会加速基板热载子效应的进行。
最后,本論文最后附錄,将研究制作在(100)或(111)晶片上且具有超薄氧化层的pMOSFETs,关于其闸极氧化层厚度,载子迁移率和氮離子剂量之效应。制作在(111)矽晶片的pMOSFETs 可以把原本制作在(100)矽晶片上的pMOSFETs 之转导提升约64%。吾人亦发现,氮離子的布植可以增加(100)矽晶上pMOSFETs的载子迁移率,但是会降低(111)矽晶片上pMOSFETs 的载子迁移率。另一方面,因为二维的应变效应,在(111)矽晶片上的pMOSFETs 呈现出对长宽比的高度相关性,且在(111)矽晶片上的pMOSFETs 对温度有比较大的靈敏度。
We discuss dynamic threshold MOS (DTMOS) operations for nMOSFETs ofdifferent dielectric types and thicknesses. We found that, under the DT mode of operation, all devices exhibit a threshold voltage close to 0.7 V, independent of the thickness and gate dielectric type of the device. This is due to the diminished influence of the body effect factor. Formulations of threshold voltage and subthreshold swing of DTMOS are developed to gain insights into this unique phenomenon, and simulation of the subthreshold swing is also provided. Then, we compared the hot carrier effects of T-gate and H-gate SOI pMOSFETs operating under DT-mode and conventional mode at various temperatures. By operating under DT-mode, the threshold voltage shift is reduced. However, enhanced degradations in maximum transconductance and drive current are observed when operating under
DT-mode at room temperature, especially for the T-gate structure. The transconductance enlargement effect for devices operating under DT-mode, together with the non-uniform potential distribution in T-gate structure, are believed to be responsible for the observed enhanced degradations. The applications of DTMOS with reverse Schottky barrier on substrate contacts for high voltage and high temperature were presented. By this reverse Schottky
barrier on substrate contact, DTMOS can be operated at high voltage, and exhibits excellent performance at high temperature in terms of ideal subthreshold slope, low
threshold voltage and high driving current. In addition, the characteristics of DT-pMOSFETs using the reverse Schottky substrate contacts are also discussed.
Furthermore, the NBTI effects of DTMOS were also reported for the first time. This is because DTMOS could operate just below 0.7V of VG due to the diode turn-on behavior. It is interesting to note that the shift of the ΔVTH of pMOSFETs under NBTI measurement was significantly alleviated in the DT operating mode. Furthermore, NBTI effects of pMOSFETs with different nitrogen dose
implantation and regions were investigated in the appendix A. High nitrogen dose implantation in the channel or source/drain extension results in serious NBTI degradation. Both the dynamic NBTI effects and substrate hot holes effects were also discussed in this dissertation. Larger nitrogen dose not only results in serious NBTI effects but also serious substrate hot holes effects.. Finally, gate dielectric thickness, carrier mobility, and nitrogen dosage effects on pMOSFETs with ultra-thin gate dielectric on Si-(100) and Si-(111) were investigated in the appendix B. PMOSFETs on Si-(111) show about 64% improvement of carrier mobility than that on Si-(100) counterparts. We found that the nitrogen incorporation enhances the carrier mobility
on Si-(100), but degrades on Si-(111). In addition, compared to Si-(100), pMOSFETs on Si-(111) show a strong dependence with aspect ration effect due to 2-dimensional
strain effect. Finally, pMOSFETs on Si-(111) show slightly large sensitive for temperature dependence.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT008911805
http://hdl.handle.net/11536/76835
显示于类别:Thesis


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  1. 180501.pdf
  2. 180502.pdf
  3. 180503.pdf
  4. 180504.pdf
  5. 180505.pdf
  6. 180506.pdf
  7. 180507.pdf
  8. 180508.pdf
  9. 180509.pdf
  10. 180510.pdf
  11. 180511.pdf
  12. 180512.pdf
  13. 180513.pdf
  14. 180514.pdf
  15. 180515.pdf

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