Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

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Fundamentals of Modern VLSI Devices

Rise of silicene: A competitive 2D material

This paper focuses on approaches to continuing CMOS scaling by introducing new device structures and new materials. Starting from an analysis of the sources of improvements in device performance, we present technology options for achieving these performance enhancements. These options include high-dielectric-constant (high-k) gate dielectric, metal gate electrode, double-gate FET, and strained-silicon FET. Nanotechnology is examined in the context of continuing the progress in electronic systems enabled by silicon microelectronics technology. The carbon nanotube field-effect transistor is examined as an example of the evaluation process required to identify suitable nanotechnologies for such purposes.

Beyond the conventional transistor

This review paper explores considerations for ultimate CMOS transistor scaling Transistor architectures such as extremely thin silicon-on-insulator and FinFET (and related architectures such as TriGate, Omega-FET, Pi-Gate), as well as nanowire device architectures, are compared and contrasted Key technology challenges (such as advanced gate stacks, mobility, resistance, and capacitance) shared by all of the architectures will be discussed in relation to recent research results

Considerations for Ultimate CMOS Scaling

To a large extent, scaling was not seriously challenged in the past. However, a closer look reveals that early signs of scaling limits were seen in high-performance devices in recent technology nodes. To obtain the projected performance gain of 30% per generation, device designers have been forced to relax the device subthreshold leakage continuously from one to several nA/µm for the 250-nm node to hundreds of nA/µm for the 65-nm node. Consequently, passive power density is now a significant portion of the power budget of a high-speed microprocessor. In this paper we discuss device and material options to improve device performance when conventional scaling is power-constrained. These options can be separated into three categories: improved short-channel behavior, improved current drive, and improved switching behavior. In the first category fall advanced dielectrics and multi-gate devices. The second category comprises mobility-enhancing measures through stress and substrate material alternatives. The third category focuses mainly on scaling of SOI body thickness to reduce capacitance. We do not provide details of the fabrication of these different device options or the manufacturing challenges that must be met. Rather, we discuss the fundamental scaling issues related to the various device options. We conclude with a brief discussion of the ultimate FET close to the fundamental silicon device limit.

Silicon CMOS devices beyond scaling

A novel disposable polysilicon/RTCVD nitride sidewall process for sub-50 nm CMOS has been developed. This process allows the gate and deep source drain doping and anneals to be performed before the shallow extension and halo, thus enabling independent optimization of gate activation and low-thermal-cycle abrupt junctions. The new process offers much higher etch selectivities in terms of sidewall formation and strip operations than the oxide and nitride sidewall processes. In addition, it also gives much better sidewall dimensional control for device optimization. Sub-100 nm device fabricated with disposable sidewall process show less poly depletion (thinner Tinv) and significantly improved drive current than those fabricated with the conventional process. A high transconductance of 1150 mS/mm is obtained with the shortest device of 32 nm gate length generated by the new disposable polysilicon sidewall process.

New polysilicon disposable sidewall process for sub-50 nm CMOS

A 65 nm prototype embedded DRAM macro on partially depleted SOI (PD-SOI) substrate capable of <2. 0ns latency and the enabling cell technology have been described previously [1,2]. In this paper, we focus on the cell design and optimization for best retention and performance which have been extended to the 45 nm node.

Access Transistor Design and Optimization for 65/45nm High Performance SOI eDRAM

There have been significant differences in principle electrical parameters between amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) and silicon-based devices for their distinct conduction mechanisms. Additionally, threshold voltage is one of the key parameters in device characterization and modeling. In this work, a threshold voltage model is developed for AOS TFTs considering the various density of exponential tail states below the conduction band, including degenerate conduction. The threshold condition is defined where the density ratio of free carriers to the trapped carriers reaches a critical value depending on the distribution parameters of tail states. The resulting threshold voltage expression is fully analytical and is of clear physical meaning, with simple parameter extraction methods. Numerical and experimental verifications show that this model provides appropriate values of threshold voltage for devices with different sub-gap tail states, which could be a useful method for identifying the threshold voltage of a large variety of AOS TFTs.

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J. Cai

Papers

New polysilicon disposable sidewall process for sub-50 nm CMOS

Access Transistor Design and Optimization for 65/45nm High Performance SOI eDRAM

A Threshold Voltage Model for AOS TFTs Considering a Wide Range of Tail-State Density and Degeneration