Method for Manufacturing Silicon X-Ray Masks Via Plasma Chemical Etching
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for Manufacturing Silicon X-Ray Masks Via Plasma Chemical Etching A. N. Gentseleva, *, F. N. Dultsevb, c, B. G. Goldenberga, and K. E. Kupera aInstitute
of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia b Novosibirsk State University, Novosibirsk, 630090 Russia c Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected] Received December 29, 2019; revised January 29, 2020; accepted January 31, 2020
Abstract—A simple method for manufacturing silicon masks for deep X-ray lithography, conducted with the application of exposure radiation of the spectral range (0.5–7 Å), is described. This method is based on planar silicon technology, which is widely used in the production of semiconductor devices. A significant difference between this method and previously known analogues is that it does not apply the creation of a stop layer by doping during formation of the support membrane of the mask. As the initial blank, a standard (100) oriented silicon wafer is used. The silicon support membrane of the mask is formed in the final stage of its manufacture by plasma-chemical etching of the rear-side of the wafer to a predetermined depth. The thus obtained X-ray masks on a silicon wafer are characterized by relative ease of manufacture, radiation and chemical resistance, geometric stability, and relatively high levels of mechanical strength and X-ray transparency of the support membrane, depending on its thickness, which can be manufactured with good accuracy and within a fairly wide range of ~2.5–50 μm, depending on the purpose of the mask. Keywords: deep X-ray lithography, X-ray masks, LIGA technology DOI: 10.1134/S1027451020040266
INTRODUCTION Historically, X-ray lithography was developed as a possible alternative to photolithography and the wavelength range of the exposure radiation (λ ≈ 3–50 Å) used was conditionally divided, mainly from the point of view of the resolving power, into subbands of short (3–7 Å), medium (7 –10 Å) and long (10–50 Å) waves [1]. In experiments on X-ray lithography, synchrotron radiation (SR) is predominantly used as the exposure radiation due to its low divergence and high intensity [2]. X-ray masks have the following typical design: an X-ray-absorbing topological pattern (formed, as a rule, by the galvanic deposition of heavy metals through a resistive mask) is attached by adhesion forces to the working surface of a thin X-ray-transparent support membrane (made of materials with a low atomic number), and that, in turn, is secured via its edges to the support ring [3]. The advantages of the subrange (3–7 Å) compared to the others are expressed in a decrease in the influence of diffraction effects on distortion of the topological pattern during its transfer and less attenuation of the exposure radiation of the mask support membrane and separation windows of the SR output channel. This makes it possible to produce X-ray masks with membranes of relatively large thickness and
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