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首页> 外文会议>Metrology, Inspection, and Process Control for Microlithography XX pt.2 >Bossung Curves; an old technique with a new twist for sub-90 nm nodes
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Bossung Curves; an old technique with a new twist for sub-90 nm nodes

机译：Bossung曲线；低于90 nm节点的具有新扭曲的旧技术

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摘要

The classic Bossung Curve analysis is the most commonly applied tool of the lithographer. The analysis maps a control surface for critical dimensions (CD's) as a function of the variables of focus and exposure (dose). Most commonly the technique is used to calculate the optimum focus and dose process point that yields the greatest depth-of-focus (DoF) over a tolerable range of exposure latitude. Recent ITRS roadmaps have cited the need to control CD's to less than 4 nm Across-Chip-Linewidth-Variation (ACLV). A closely related requirement to ACLV is the need to properly evaluate the implementation of Optical Proximity Correction (OPC) in the final resist image on the wafer. Calculation of ACLV and the process points are typically addressed with the use of theoretical simulator evaluations of the actinic wavefront and the photoresist's interactions. Engineers frequently prefer the clean results of the simulation over the more cumbersome and less understood perturbations seen in the empirical metrology data resulting in a loss of valuable process control information. Complexity increases when the analysis assumes a super-positioning of the responses of multiple feature-types in the search for an overlapping process window. Until recently, simulations rarely validated design response to the process and never incorporated the characteristics of the exposure tool and reticle. Fortunately empirical Bossung curve calculations can supply valuable tool, process and reticle specific interaction information if the techniques are expanded through the use of spatial and temporal perturbation models of the actinic image wavefront. In this implementation the classic focus-exposure matrix is shown to be a powerful tool for the determination of optimum focus and focus uniformity across the full exposure field. Although not the tool of choice for pupil aberration analysis, the method is the best implementation for determining the behavior of device critical feature response when the constructs of OPC, forbidden-pitch and inherent reticle variability are involved. Improved process performance can be achieved with algorithms that provide a calculation of the optimum focus ridge whose resulting feature response-to-dose curves are more easily traced to simulation. Response surface models are presented and applied to a calculation of the Best Focus surface for the exposure field. Unlike specialty reticles used in defocus error, the Bossung curve maps the response of the reticle specific feature or OPC design and can provide information on errors induced by the lens/optomechanical system of the exposure tool. The Bossung curve delivers several additional response surfaces needed for proper qualification of any exposure-tool and reticle set. These include the ability to contour-map the critical Feature-Best-Focus surface response across the exposure field of the reticle that accounts for feature and process design variations, the Depth-of-Focus uniformity surface for each critical feature across the full exposure, an Isofocal ridge analysis of the process and the associated process perturbation response and the effective dose-uniformity response needed to achieve target feature size uniformity across the exposure.
机译：经典的Bossung曲线分析是平版印刷师最常用的工具。该分析将关键尺寸（CD）的控制表面映射为焦点和曝光（剂量）变量的函数。最常见的技术是用于计算最佳聚焦和剂量处理点，以在可承受的曝光范围内产生最大的聚焦深度（DoF）。最近的ITRS路线图提到需要将CD的宽度控制在4纳米以下，跨芯片线宽变化（ACLV）。与ACLV密切相关的要求是需要正确评估晶片上最终抗蚀剂图像中的光学邻近校正（OPC）的实现。通常使用光化波前和光致抗蚀剂相互作用的理论仿真器评估解决ACLV和工艺点的计算。工程师通常更喜欢模拟的干净结果，而不是经验计量数据中更麻烦，更难以理解的扰动，从而导致宝贵的过程控制信息丢失。当分析假设在寻找重叠过程窗口时多个要素类型的响应重叠时，复杂性就会增加。直到最近，仿真很少验证设计对该工艺的响应，并且从未结合曝光工具和标线的特性。幸运的是，如果通过使用光化图像波阵面的时空扰动模型扩展了该技术，则经验Bossung曲线计算可以提供有价值的工具，过程和标线特定的交互信息。在这种实现方式中，经典的对焦矩阵被证明是确定整个曝光场中最佳对焦和对焦均匀性的有力工具。尽管不是瞳孔像差分析的首选工具，但是当涉及到OPC，禁距和固有光罩可变性的构造时，该方法是确定设备关键特征响应行为的最佳方法。可以通过提供最佳聚焦脊的计算的算法来实现改进的过程性能，该聚焦脊的最终特征剂量响应曲线可以更轻松地跟踪到仿真。提出了响应曲面模型，并将其应用于曝光场的最佳聚焦曲面的计算。与散焦误差中使用的专用掩模版不同，Bossung曲线可映射掩模版特定功能或OPC设计的响应，并可提供有关曝光工具的透镜/光学机械系统引起的误差的信息。 Bossung曲线提供了对任何曝光工具和标线片组进行适当鉴定所需的其他几个响应面。这些功能包括在标线片的曝光场上绘制出关键特征-最佳焦点表面响应的轮廓图，以反映特征和工艺设计的变化，整个曝光中每个关键特征的焦点深度均匀性表面，对整个过程进行等距脊脊分析，相关的过程扰动响应以及有效的剂量均匀性响应，以实现目标特征尺寸的均匀性。

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