用于极紫外光刻的双镜面小面投影系统

中文摘要 AI 辅助

我们提出了一种用于极紫外（EUV）光刻的全反射双镜投影系统，工作曝光波长为13.5 nm（Mo/Si）和11.2 nm（Ru/Be），在数值孔径接近1（NA_max ≈ 0.993）时，对周期性掩模图案实现四倍（4×）缩小。与包含6至10个非球面镜、总光学吞吐量低于15%的传统EUV投影物镜相比，所提出的设计通过一对专用的平面镜小面，将掩模散射的每个可接受的离散空间衍射级次重定向到晶圆上。对于所有可接受的级次，反射次数严格固定为两次，在每个可接受的级次中保留离开掩模功率的50%至60%。我们推导出一种空间几何结构，可在所有衍射级次间实现严格的光程长度均衡，从而消除与级次相关的传播相位偏移。使用传输矩阵方法结合全局进化优化算法，为每个小面设计了单独优化的30层布拉格多层膜涂层。该架构被推广到具有二维周期掩模的三维矢量公式。利用逆光刻技术、傅里叶参数化和可微分的电磁模态波导求解器，我们解决了二元吸收体掩模（La吸收体位于Ru/Be/Sr多层镜上）的合成问题。我们展示了晶圆上亚10纳米特征的模拟航空图像（孤立峰的半高全宽（FWHM）约为5.4 nm，线对的临界尺寸为6 nm），并发现对于沿z轴从0到5 nm的测试晶圆离焦值，两个峰保持可分辨。

英文摘要

We propose an all-reflective two-mirror projection system for extreme ultraviolet (EUV) lithography operating at exposure wavelengths of $13.5$~nm (Mo/Si) and $11.2$~nm (Ru/Be), delivering a fourfold ($4\times$) demagnification of the periodic mask pattern at a numerical aperture approaching unity ($\mathrm{NA}_{\max} \approx 0.993$). In contrast to conventional EUV projection objectives that incorporate 6--10 aspheric mirrors with an overall optical throughput of less than $15\%$, the proposed design redirects each accepted discrete spatial diffraction order scattered by the mask onto the wafer via a dedicated pair of planar mirror facets. The number of reflections is strictly fixed at two for all accepted orders, retaining $50$--$60\%$ of the power leaving the mask in each accepted order. We derive a spatial geometry providing rigorous optical path length equalization across all diffraction orders, thereby removing order-dependent propagation phase shifts. Individually optimized 30-bilayer Bragg multilayer coatings are designed for each facet using the transfer matrix method combined with global evolutionary optimization algorithms. The architecture is generalized to a three-dimensional vector formulation with a two-dimensionally periodic mask. Utilizing inverse lithography technology, Fourier parameterization, and a differentiable electromagnetic modal waveguide solver, we solve the synthesis problem for binary absorber masks (La absorber on a Ru/Be/Sr multilayer mirror). We demonstrate simulated aerial images of sub-10-nm features on the wafer (isolated peaks with a full width at half maximum (FWHM) of approximately $5.4$~nm and line pairs with a critical dimension of $6$~nm) and find that the two peaks remain resolved for the tested wafer defocus values from $0$ to $5$~nm along the $z$-axis.

发表机构

• University of Nizhny Novgorod（下诺夫哥罗德大学）

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