Precision Fabrication of Nanostructures by Optimal Mixed H2/H Control of Microcontact Next Generation Lithography Systems

目前开始探索许多不同的所谓的NGL(下一代光刻)技术，以继续迄今为止令人难以置信的成功的光学光刻技术，其可以将PI带到具有70 nm临界尺寸的器件上，其中更有趣的NGL技术类别之一，称为微接触或软光刻，即使在制造10 nm特征尺寸和工作的集成器件时也表现出了非凡的图案化保真度。微接触光刻方法涉及1：1保形掩模或模板，使其与衬底的表面直接接触，接触后完成印刷过程的几种不同方法，包括物理、化学和光子手段。最近，PI的斯坦福半导体制造集团开发了一种利用可渗透膜材料(PMM)的新型微接触NCL策略。在这种方法中，图形转移是通过可渗透的多孔模板通过反应物种的分子传输来实现的，从而在基板表面形成空间选择性的抗蚀刻掩模。在微接触NGL技术所设想的尺寸上，掩模和基板在整个印刷轨迹(包括延伸、保持和收回)中需要非常精确的定位和对准。PI公司建议为此目的开发一种最优多变量控制系统，并将他们最近开发的PMM系统作为具体的测试工具。初步探索使他们专注于双伺服6轴压电式纳米定位挠性工作台，以及实时掩模-基板间隙检测和激光干涉定位和对准。总体而言，精细工作台系统将使用6个压电致动器和19个高分辨率定位探测器。虽然控制律将在他们的PMM技术和相关的近场直写图案系统上开发和演示，但该策略将普遍适用于采用挠性定位方法的其他微接触NCL技术。首先，将利用斯坦福大学Cho和Kailath开发的所谓的子空间方法的最新进展，确定挠曲阶段的状态空间模型。在规划的方法中，将生成频域数据并计算线性时不变模型。子空间辨识技术提供了一种生成多变量状态空间模型的非迭代方法。对于它们在传感器集合中具有相当大的冗余度的应用，子空间方法对于模型辨识是有用的，因为利用位移结构理论的结果可以获得快速算法。他们还计划使用子空间识别输出来确定控制单元的最小检测器和执行器集。利用识别的模型，他们将设计最优的混合H2/H控制器。H2/H控制目标适用于该项目，因为需要优化定位速度以增加吞吐量，同时防止掩模与基板表面发生最坏情况的碰撞。由于振动引起的随机和带限扰动，以及梁的非线性弯矩、滞后、可变的初始条件和地形效应等内部效应进入对象，必须沿着期望的定位轨迹进行补偿。总之，该方案设想扩展和应用最新的控制设计理论来设计非常高性能的纳米定位控制系统。一种特定的新的所谓PMM技术将成为开发的试验台。然而，这些技术与几种微接触技术相关；它们还应用于特定的应用，如在曲面上制造，以及制造MEMS(微电子机械系统)、微合成和微流体系统。

0000541KailathA number of different so-called NGL (next generation lithography) techniques are currently begin explored for continuation of the so-far incredibly successful optical lithography techniques, which can take the PI's to devices with 70 nm critical dimensions, one of the more interesting classes of NGL techniques, called microcontact or soft lithography, has demonstrated exceptional patterning fidelity in even the fabrication of 10 nm feature sizes and working integrated devices. Microcontact lithography methods involve a 1:1 conformal mask or template, brought into direct contact with the surface of the substrate with several different approaches for completing the printing process subsequent to contact, including physical, chemical, and photonic means. Recently, a novel microcontact NCL strategy utilizing permeable membrane materials (PMM) has been developed in the PI's Stanford semiconductor manufacturing group. In this approach, pattern transfer is achieved by molecular transport of reactive species through a permeable porous template to form a spatially selective etch-resistant mask on the substrate surface.At the dimensions envisaged for microcontact NGL techniques, extremely precise positioning and alignment of mask and substrate will be needed during the entire printing trajectory including extension, hold, and retraction. The PI's propose to develop an optimal multivariable control system for this purpose, with their recently developed PMM system as a specific test vehicle. Preliminary explorations have led them to focus on a dual servo 6-axis piezeo-driven nanopositioning flexure stage along with real-time mask-substrate gap detection and laser interferometry for positioning and alignment. Overall, the fine-stage system will employ six piezoactuators and nineteen high resolution positioning detectors. Although the control laws will be developed and demonstrated on their PMM technology and a related near-field direct write patterning system, the strategy will be generally applicable to other microcontact NCL techniques that employ flexure positioning methods.Some details on their proposed approach follow. First, a state-space model of the flexure stage will be identified using recent advances in the so-called subspace methods developed by Cho and Kailath at Stanford. In the planned approach, frequency domain data will be generated and a linear time invariant model will be computed. Subspace identification techniques offer a non-iterative method to generate multivariable state-space models. For their application which has considerable redundancy in the sensor set, the subspace approach to model identification is useful since, by employing results from displacement structure theory, fast algorithms can be obtained. They also plan to investigate the use of the subspace identification output to determine a minimal set of detectors and actuators to control the unit.Using the identified model, they will design an optimal mixed H2/H controller. The H2/H control objective is applicable to this project because of the need to optimize the positioning speed for an increase in throughput while guarding against worst-case crashes of the mask to the substrate surface. Both stochastic and bandlimited disturbances due to vibrations, as well as internal effects such as nonlinear beam bending moments, hysteresis, and variable initial conditions and topography effects, enter the plant and must be compensated along the desired positioning trajectory.In brief, this proposal envisages the extension and application of recent control design theories to design a very high performance nanopositioning control system. A specific new so-called PMM technology will be the testbed for the development. However the techniques are relevant to several microcontact technologies; they should also be useful for specific applications such as fabrication on curved surfaces, and for manufacturing MEMS (microelectro- mechanical systems), microsynthetic and microfluidic systems.***