标题: | 奈米级萧特基金氧半场效电晶体之载子传输特性与通道背向散射研究 The Carrier Transport and Channel Backscattering Characteristics of Nanoscale Schottky-Barrier MOSFETs |
作者: | 邓安舜 Teng, An-Shun 庄绍勋 Chung, Steve S. 电子研究所 |
关键字: | 萧特基金氧半场效电晶体;载子弹道传输;萧特基位障势;Schottky-barrier MOSFET;Ballistic transport;Schottky-barrier Height |
公开日期: | 2009 |
摘要: | 在前瞻超大型积体电路元件中,为了提升元件的效能,许多新颖的元件结构已被广泛的提出,例如:高介电系数介电层、应变矽通道、金属闸极与金属源/汲极结构。当元件微缩至奈米级尺寸时,通道背向散射理论已经成功的运用在预测元件微缩极限上。而今,由于萧特基金氧半场效电晶体制作的最佳化方法已趋可行,其在前瞻元件演进的地位已大幅的提升。因此,萧特基金氧半场效电晶体的载子传输特性的研究成为主要课题。 本论文中,我们首先着眼于利用活化能(Activation Energy Method)方法求得等效的萧特基位障势。萧特基场效电晶体之汲极电流传导机制与闸极电压的关系式可利用等效萧特基位障势表示。另外,我们同时发现萧特基金氧半场效电晶体在打开状态时,产生一个负等效萧特基位障势,使通道背向散射原理可运用于此。以往,温度相依法(Temperature Dependent Method)常被用来探讨通道背向散射系数。但是,在萧特基金氧半场效电晶体中,载子主要是透过热场发射机制由源极入射制通道内。所以对此元件来说,温度相依法是不可行的。为了要求得载子弹道入射的机率,我们导入了等效弹道迁移率(Effective Ballistic Mobility)的观念,此原理是建立在载子迁移率(Mobility)会随着通道缩小而下降的因素上。因此,我们可以透过等效弹道迁移率的方法得到载子在元件线性区的弹道入射系数与载子热入射(Thermal Injection Velocity)速度。然后,我们运用当电晶体在负等效萧特基位障势发生时的载子平均传输速度(Carrier Average Velocity)与载子热入射速度上,藉由这两个速度的关系式,载子在打开状态时的载子弹道入射机率即可求得。 由本文的研究,我们得到几个结论: (1) 背向散射理论在萧特基金氧半场效电机体中,因负等效位障势的产生而再度的适用, (2) 载子由源极经通道到达汲极的背向散射机率因非局部的热场穿遂机制而较传统金氧半场效电晶体高, (3) 应变矽通道元件对背向散射系数影响较轻,但对载子热入射速度影响较剧烈, (4) 迁移扩散(Drift-Diffusion)模型在quasi-ballistic区仍适用。因此,萧特基金氧半场效电晶体加上高参杂隔离层(Dopant Segregation Implantation)与CESL(Contact-Etched Stoped Layer)技术,可达道元件高速操作的需求。 In advanced VLSI devices, a lot of new structures have been brought up for enhancing drain current such as strained-Si channel, high-κ dielectric, metal gate and metal source/drain. In the nanoscale channel length, the channel backscattering theory has been applied to predict the scaling-limitations of these structures successfully. Nowadays, the Schottky-barrier MOSFETs have aroused much more attention because some optimized processes become feasible. Hence, the carrier transport mechanism of Schottky-barrier MOSFETs from source to drain becomes the most popular topic in researches. In the thesis, first, we will focus on finding the effective Schottky-barrier height from the activation energy method. We can describe the effective Schottky-barrier height versus carrier transport mechanism relationship from this method. A negative effective Schottky-barrier height is found in the ON-state of the Schottky-barrier MOSFETs so that the channel backscattering theory can be used for extracting the carrier ballistic rate. In the past, the ballistic coefficient is extracted by temperature dependent method. However, the major carrier transport mechanism in the Schottky-barrier MOSFET is field emission, the temperature dependent method is failed. We practiced the effective ballistic mobility which is from mobility degradation in short channel devices. We may directly obtain the ballistic coefficient and thermal injection velocity in the linear region. Then, we derive the carrier average velocity versus thermal injection velocity relations in ON-state. By the two velocity components, the ballistic probability of the Schottky-barrier MOSFET can be extracted easily. Based on the results of this work, it was concluded that: (1) the backscattering theory is practicable from the negatively effective Schottky-barrier height, (2) the backscattering probability in the source side of Schottky-barrier is smaller than that in the conventional MOSFETs due to non-local tunneling, (3) the strained technology affects the backscattering coefficient lightly but it affects the thermal injection velocity drastically, (4) the drift-diffusion model is still workable in quasi-ballistic region. Thus, Schottky-barrier MOSFET with dopant segregation implantation and CESL(Contact-Etched Stoped Layer) can enhance the ballistic rate and thermal injection velocity that produced high speed operation in Schottky-barrier MOSFETs. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079611542 http://hdl.handle.net/11536/41675 |
显示于类别: | Thesis |
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