Open-air type plasma chemical vaporization machining by applying pulse-width modulation control
Open-air type plasma chemical vaporization machining by applying pulse-width modulation control
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DOI：
10.1088/0022-3727/47/11/115503
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
Y. Takeda;Y. Hata;K. Endo;K. Yamamura
中科院分区：
文献类型：
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作者：
Y. Takeda;Y. Hata;K. Endo;K. Yamamura
光刻技术已被用于实现将图案低成本和高速地转移到硅片上。然而，由于半导体的高度集成化，将越来越多地使用极端紫外线作为曝光光源，所有光学元件都必须是反射的，才能聚焦光线，因为光的波长太短，无法通过透镜。反射光学器件的形状精度影响转移的精度，根据国际半导体技术路线图，6英寸光掩模基板上的平坦度要求小于32 nm。等离子体化学汽化加工是一种超精密加工技术，能够获得纳米级的形状精度。在我们以前的研究中，通过改变工作台的扫描速度来控制去除体积。然而，当速度变化很快时，由于工作台的惯性，理论扫描速度和实际扫描速度之间会出现偏差。为了解决这个问题，我们通过控制等离子体产生过程中施加的电功率来控制去除体积，同时保持恒定的扫描速度。我们采用的控制方法有调幅(AM)控制和脉宽调制(PWM)控制。在这项工作中，我们评估了材料去除速度在AM和PWM控制模式下的可控性。
Photolithography techniques have been used to enable the low-cost and high-speed transfer of a pattern onto a silicon wafer. However, owing to the high integration of semiconductors, extreme ultraviolet will be increasingly used as the exposure light source and all optics must be reflective to focus light because the wavelength of the light will be so short that it cannot pass through a lens. The form accuracy of reflective optics affects the accuracy of transfer, and a flatness of less than 32 nm on a 6 inch photomask substrate is required according to the International Technology Roadmap for Semiconductors roadmap. Plasma chemical vaporization machining is an ultraprecise figuring technique that enables a form accuracy of nanometre order to be obtained. In our previous study, the removal volume was controlled by changing the scanning speed of the worktable. However, a discrepancy between the theoretical scanning speed and the actual scanning speed occurred owing to the inertia of the worktable when the change in speed was rapid. As an attempt to resolve this issue, we controlled the removal volume by controlling the electric power applied during plasma generation while maintaining a constant scanning speed. The methods that we adapted to control the applied electric power were amplitude-modulation (AM) control and pulse-width modulation (PWM) control. In this work, we evaluate the controllability of the material removal rate in the AM and PWM control modes.