基于软X射线干涉光刻的自溯源光栅倍频技术

Nanoscale measurement is the precondition of developing nanofabrication. The measuring instruments, such as atomic force microscope, etc., have intrinsic errors, and need to be calibrated by the nanoscale standard materials to precisely determine the critical dimensions of the devices. As the scaling down of nanoscale devices, in order to calibrate the measuring instruments at small scale with high accuracy, the International Technology Roadmap for Semiconductors requires that the critical dimensions of standard materials should have a uncertainty below 0.29nm at the 14nm node. The general standard materials hold a critical dimension error at 1 nm level, it cannot calibrate the measurement instruments with high accuracy. For the self-traceable standard materials, the critical dimensional error is at 0.001 nm level, which can do the high accuracy calibrations. But the reality is that there is no reliable self-traceable standard materials at sub-200nm scale. A new solution is proposed here to combine the atom lithography and soft X-ray interference lithography (XIL) to fabricate new self-traceable standard materials, in which the spatial frequency of the 212.8nm Cr self-traceable gratings get doubled with the self-traceability transferred. By investigating the formation of Cr self-traceable nano-gratings, the diffraction efficiency of the mask can be maximized. The line edge roughness of the fabricated nano-gratings can be minimized by optimizing the process of exposure and lower the influence of the mask. Together with the examination of self-traceability of the fabricated nano-gratings by the metrological methods, a series of self-traceable standard materials with pitches of 106.4 nm, 53.2 nm and 26.6 nm are expected to be fabricated.

纳米测量是发展纳米制造的前提条件。AFM等纳米测量工具均存在误差，需用纳米长度标准物质进行校准，才能精确测量器件特征尺寸。随着纳米器件越来越小，国际半导体技术蓝图组织要求标准物质特征尺寸在14nm节点以下误差需小于0.29nm，方可进行小尺度高精度校准。普通标准物质在小尺度下误差为1nm量级，无法进行高精度校准；自溯源标准物质误差为0.001nm量级，可实现高精度校准，但目前无成熟的亚200nm自溯源标准物质。本项目提出结合“Cr原子光刻”与“软X射线干涉光刻”的新方法，可以在保持自溯源性的基础上对Cr自溯源光栅（212.8nm）进行倍频复制。通过研究Cr自溯源光栅结构形成机理使衍射效率最大化，优化曝光工艺并降低掩膜版影响使线边缘粗糙度最小化，并使用计量型表征验证倍频光栅自溯源特性，研制满足应用要求的节距为106.4nm、53.2nm、26.6nm的系列自溯源标准物质。

纳米测量是发展纳米制造的前提条件。AFM等纳米测量工具均存在误差，需用纳米长度标准物质进行校准，才能精确测量器件特征尺寸。本项目提出结合“Cr原子光刻”与“软X射线干涉光刻”的新方法，拟在保持自溯源性的基础上对Cr自溯源光栅（212.8nm）进行倍频复制，研制满足应用要求的节距为106.4nm、53.2nm、26.6nm的系列自溯源标准物质。自项目实施以来，项目组研究了Cr自溯源光栅结构形成机理使衍射效率最大化，优化曝光工艺并降低掩膜版影响使线边缘粗糙度最小化，最终新研制出4种新的自溯源光栅：（1）周期为106.4nm的一维硅自溯源光栅；（2）周期为53.2nm的一维硅自溯源光栅；（3）周期为212.8nm的二维铬自溯源光栅；（4）周期为150.4nm的二维硅自溯源光栅。其中，经世界权威计量机构德国联邦物理技术研究院计量测试表明，周期为106.4nm的一维硅自溯源光栅不确定度仅0.009nm，处于国际领先水平，该光栅也成功获批成为国家一级标准物质（GBW13983）。系列自溯源光栅的研制扩展了我国计量标准光栅的尺度和维度，为提升我国纳米测量准确性水平奠定了器件基础。