大口径大陡度曲面基底极紫外/软X射线多层膜膜厚横向梯度控制

Laterally graded EUV/Soft X-Ray multilayers have been widely used in EUV/SXR telescope, Soft X-Ray microscope, EUV lithography, X-ray plasma diagnosis, and EUV/SXR laser. In the prior research, the applicant proposed a method to reverse the sputtering distribution of the source by fitting the coating thickness profiles of flat substrates at different heights using genetic algorithm. A precision of ±0.1% for controlling multilayer thickness gradients on a curved substrate with diameter of 200 mm and maximum slope angle of 16°, has been achieved by orbit velocity modulation of substrate in a magnetron sputtering system. However, the peak reflectance of multilayers deposited on the edge of curved substrate with larger slope angle decreased obviously. Furthermore, for controlling multilayer thickness gradients on a curved substrate with larger diameter and larger slope angle, modulating the orbit velocity of substrate is not enough to obtain multilayer thickness gradients with high controlling precision, due to the limited accelerating capability of servo motor. By combining the theoretical calculation with experimental testing, the project will investigate how to realize high performance laterally graded EUV/SXR multilayers on large steeply curved substrates. First, the general rule that how the variation of process parameters in magnetron sputtering effects the interface quality of multilayers deposited on large steeply curved substrates will be found by theoretical calculation, and accordingly a process window will be obtained by balancing the interface roughness and interface diffusion of multilayers. Then, in this process window the optimal process parameters will be determined by experimental testing and comprehensive characterizations of interface quality of multilayers. Finally, on the condition of optimal process parameter, extremely precise control of lateral thickness gradients of multilayers on large steeply curved substrate will be achieved, by simultaneously using shadowing mask and velocity modulation of substrate. By the implement of the project, two theoretical models will be established. The first one is used for calculating the interface roughness and interface diffusion of multilayers deposited on large steeply curved substrate with different process parameters and the second one is used for controlling lateral thickness gradients of multilayers on large steeply curved substrate by using shadowing mask and velocity modulation of substrate in magnetron sputtering. The research finds will provide scientific basis and technical reserves for controlling the lateral thickness gradients of high reflectance multilayers on large steeply curved substrate.

极紫外/软X射线(EUV/SXR)横向梯度多层膜在EUV光刻等领域具有重要应用前景。前期研究中，申请人提出了基于遗传算法的磁控溅射源分布特性反演方法，通过调节基底公转速度在口径200mm、边缘倾角16°曲面基底上实现了±0.1%膜厚梯度控制精度，但当曲面基底口径更大、边缘更陡时，边缘大倾角下多层膜反射率下降较大，且仅靠调速无法满足梯度控制需求。本项目拟采用修正挡板加基底调速对膜厚横向梯度进行联合控制的方案，建立磁控溅射中大口径大陡度曲面基底多层膜沉积工艺优化及膜厚梯度控制理论模型，研究磁控溅射工艺参数影响曲面基底上沉积多层膜界面粗糙度和扩散的规律，建立修正挡板形状和基底速度曲线与膜厚梯度分布的定量关系，实现大口径大陡度曲面基底上高反射率多层膜及其膜厚梯度的高精度控制。项目研究成果将为大口径大陡度曲面基底上高反射率多层膜横向梯度控制提供科学基础和技术储备。

极紫外/软X射线(EUV/SXR)横向梯度多层膜在EUV光刻等领域具有重要应用前景。极紫外多层膜光学元件基底一般为曲面基底，一般情况下可通过公转调速控制多层膜的膜厚梯度，但当曲面基底口径更大、边缘更陡时，边缘大倾角下多层膜反射率下降较大，且仅靠调速无法满足梯度控制需求。本项目完成了磁控溅射沉积极紫外多层膜模型和修正正挡板加基底公转速度调制对膜厚梯度进行控制的理论模型构建，在此基础上，完成了大口径大陡度曲面基底上极紫外多层膜高反射率工艺研发和膜厚梯度控制研究，平均反射率大于69%，边缘处的峰值反射率与中心处相比其降幅不大于1%，大口径大陡度曲面基底上多层膜膜厚梯度控制精度优于±0.1%。项目研究成果将为大口径大陡度曲面极紫外多层膜光学元件开发提供了有力的支撑。