NIRT: Architectures and Devices for Quantum-dot Cellular Automata

CCR-0210153 Kogge，Peter该提案是响应NSF 01-157，类别NIRT的纳米科学与工程倡议而收到的。 量子点元胞自动机（QCA）是一种革命性的计算范式，非常适合于纳米电子实现和分子尺度的扩展。QCA的中心特征是二进制信息被编码在形成单元的一组点中的单个电子的位置中。这代表着与基于晶体管的范例的重大突破，在基于晶体管的范例中，信息是由晶体管电流开关的状态编码的。在QCA中，电子在单元内的量子点之间切换，但没有电流在单元之间流动。这导致极低的功耗，避免了最终限制晶体管电路集成密度的发热问题。事实证明，从架构和设备的角度来看，QCA电路的时钟都极其重要。它允许QCA单元的阵列被分解成子阵列以进行流水线处理，并且它使单元能够产生信号功率增益以替换损失到环境中的信号能量。功能QCA设备已经被证明在铝/氧化物隧道结方案，确认QCA单元，移位寄存器，逻辑门，和存储器元件的操作。在QCA移位寄存器的功率增益也已实现。该项目将推进QCA的架构发展，研究纳米电子器件中的开关速度问题，并开发先进的制造技术来实现架构和电路理论概念。由于QCA代表了对传统设备的巨大突破，因此需要对架构进行重大更改以充分利用QCA的功能。在QCA布局中，时序和架构密切相关，需要统一的设计方法。这类似于米德和康威开始的方法，通过在架构和布局之间建立联系，并在这种联系的基础上使设计师能够快速合成大型复杂的功能块，从而彻底改变了VLSI设计。同样，QCA系统设计人员将能够利用布局之外的时序来产生高密度功能设计。特别是，我们将研究简单，但完整的，基于QCA的“现场可编程门阵列”，其中相同的单元的二维阵列平铺在一起，可编程互连和功能的发展。时序在QCA设计中起着至关重要的作用，因此对耦合电子阵列中的开关和开关动力学有一个完整的理解是至关重要的。最近的一些理论结果表明，电子开关速度将是数量级低于预期的电容和电阻的点和隧道结，相反的理论工作在巴黎圣母院。为了解决这一问题，我们将应用高频测量技术来研究QCA单元和单元阵列中的开关。目前，由于铝隧道结产生的大电容，QCA器件的实验演示仅限于少数单元。为了支持和实验证实在架构和电路理论的进步，我们将采用先进的制造技术的基础上AFM光刻生产QCA大大增强了操作特性。这将使我们能够制造和测量具有显著范围和复杂性的细胞阵列。QCA提供了一个独特的机会，对学生的教育经验产生广泛的影响，并在电子设备领域的研究。我们将开发基于QCA模拟工具的教学模块，向本科生和研究生教授QCA架构的概念。这些模块将通过向学生介绍替代建筑概念使学生受益。此外，通过扩大他们的视野，它将通过强调建筑概念的基本概念来加强他们对传统建筑的理解。

CCR-0210153Kogge, PeterThis proposal was received in response to the Nanoscale Science and Engineering initiative, NSF 01-157, category NIRT. Quantum-dot cellular automata (QCA) is a revolutionary computing paradigm that is well suited to nanoelectronic implementation and scaling to molecular dimensions. The central feature of QCA is that binary information is encoded in the position of single electrons among a group of dots forming a cell. This represents a significant break with the transistor-based paradigm in which information is encoded by the state of the transistor current switch. In QCA, electrons switch between quantum dots within a cell, but no current flows between cells. This leads to extremely low power dissipation, avoiding the problem of heat generation that will ultimately limit the integration density of transistor circuits. Clocking of QCA circuits has proven to be extremely important from the standpoint of both architectures and devices. It allows arrays of QCA cells to be broken into sub-arrays for pipelined processing, and it enables cells to produce signal power gain to replace signal energy lost to the environment. Functioning QCA devices have already been demonstrated in an aluminum/oxide tunnel junction scheme, confirming the operation of QCA cells, shift registers, logic gates, and memory elements. Power gain in a QCA shift register has also been achieved. This project will advance the architectural development of QCA, investigate questions of switching speed in nanoelectronic devices, and develop advanced fabrication techniques to implement the architectural and circuit theory concepts. Since QCA represents a dramatic break from conventional devices, significant changes in architecture are needed to fully exploit the capabilities of QCA. In QCA layout, timing, and architecture are intimately related, requiring a unified design approach. This is analogous to the approach begun by Mead and Conway which revolutionized VLSI design by making a connection between architecture and layout and building on that connection to enable designers to quickly synthesize large and complex functional blocks. Likewise, QCA system designers will be able to exploit timing in addition to layout to produce highdensity functional designs. In particular we will investigate the development of simple, yet complete, QCA based "Field Programmable Gate Arrays", where 2D arrays of identical cells are tiled together, with programmable interconnect and function. Timing plays a pivotal role in QCA designs, so it is vital to achieve a complete understanding of switching and switching dynamics in arrays of coupled electrons. Some recent theoretical results indicate that electron switching speeds would be orders of magnitude lower than that expected from the capacitances and resistances of the dots and tunnel junctions, contrary to theoretical work done at Notre Dame. To resolve this issue we will apply high frequency measurement techniques to the study of switching in QCA cells and in arrays of cells.At present, experimental demonstrations of QCA devices are limited to a small number of cells by the large capacitances produced by the aluminum tunnel junctions. To support and experimentally confirm the advances made in architecture and circuit theory, we will employ advanced fabrication techniques based on AFM lithography to produce QCA with greatly enhanced operating characteristics. This will allow us to fabricate and measure arrays of cells with significant extent and complexity. QCA presents a unique opportunity for a broad impact on the educational experience of students, and on research in the field of electronic devices. We will develop instructional modules based on QCA simulation tools to teach the concepts of QCA architecture to undergraduate and graduate students. These modules will benefit students by introducing them to alternative architectural concepts. In addition, by broadening their horizons, it will strengthen their understanding of conventional architectures by emphasizing the foundational concepts of architectural concepts.