Applications of Microstructured Silicon Wafers as Internal Reflection Elements in Attenuated Total Reflection Fourier Transform Infrared Spectroscopy

Abstract

A novel internal reflection element (IRE) for attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectral acquisition is introduced and applied for several surface-sensitive measurements. It is based on microstructured double-side-polished (100) silicon wafers with v-shaped grooves of {111} facets on their backside. These facets of the so-called "microstructured single-reflection elements" (mSRE) are formed by a crystal-oriented anisotropic wet etching process within a conventional wafer structuring process. They are used to couple infrared radiation into and out of the IRE. In contrast to the application of the commonly used silicon multiple-reflection elements (MRE), the new elements provide single-reflection ATR measurements at the opposite wafer side by using simple reflection accessories without any special collimation. Due to the short light path, the spectral range covers the entire mid-infrared region with a high optical throughput, including the range of silicon lattice vibrations from 300 to 1500 cm(-1). In addition to typical ATR applications, i.e., the measurement of bulk liquids and soft materials, the new reflection elements can be effectively used and customer-specifically designed for in situ and ex situ investigations of aqueous solutions, thin films, and monolayers on Si. Examples presented in this article are in situ etching of native as well as thermal SiO(2) and characterization of polydimethylsiloxane (PDMS) films on Si under various measuring conditions.

Characterization of Surface Processes During Oxide CMP by in situ FTIR Spectroscopy With Microstructured Reflection Elements at Silicon Wafers

“…In an earlier study [1], the change in surface chemistry in the form of oxygenated or nonoxygenated Si hydrides on the SiO 2 or Si(100) surface during a hydrogen fluoride etch of a thin native oxide was observed. In this study, similar surface species during CMP could not be observed.…”

“…figure 1). Details about the fabrication process of these wafers, called microstructured single reflection elements (mSRE) [1], and the basics of the ATR-FTIR spectroscopy [3,4] are described elsewhere.…”

“…In this study me make use of novel, specifically prepared, and self-designed Si wafer called microstructured single reflection elements (mSRE) utilizing the IR transparency of silicon [1]. The mSRE's enable in and ex situ attenuated total reflection (ATR) Fourier transform infrared (FTIR) investigations at the interface between silicon and the ambient with an enhanced usable spectral range.…”

3D Printing for Low-Cost and Versatile Attenuated Total Reflection Infrared Spectroscopy

“…16 Furthermore, microstructured single-bounce ATR crystals make use of the easy access to Si fabrication, while allowing to extending the IR transmission of Si beyond multireflection elements. 13 All these emerging systems can be further exploited by custom-made and fit-forpurpose scientific instrumentation. Since its introduction in the 1980s, 3D-priniting has evolved into a versatile platform for rapid manufacturing of customized parts made of metals, ceramics and polymers.…”

Anisotropic Etching of Pyramidal Silica Reliefs with Metal Masks and Hydrofluoric Acid

“…DOI: 10.1002/smll.202002290 the fabrication of inverted silicon pyramids for various applications, e.g., for atomic force microcopy (AFM) tip fabrication, photovoltaics, or infrared spectroscopy. [4][5][6] Adding surfactants to KOH allows for changing the typical wet etch taper. [7] Metal films have been used for highly selective etching of diamond.…”