Very high aspect ratio through silicon via reflectometry

Abstract

Through Silicon Via (TSV) technology is a key feature of new 3D integration of circuits by creation of interconnections using vias, which go through the silicon wafer. Typically, the highly-selective Bosch Si etch process, characterized by a high etch rate and high aspect ratio and forming of scallops on the sidewalls is used. As presented in this paper, we have developed an experimental setup and a respective evaluation algorithm for the control and monitoring of very high aspect ratio TSV profiles by spectroscopic reflectometry. For this purpose square via arrays with lateral dimension from 3 to 10 µm were fabricated by a Bosch etch process and analyzed by our setup. By exploiting interference and diffraction effects of waves reflected from the top and bottom surfaces as well as from the side walls of the TSV patterns, the measurements provided etch depths, CD values and scallop periods. The results were compared with data obtained by a commercial wafer metrology tool. Aspect ratios of up to 35:1 were safely evaluable by our setup.

Novel UV-transparent 2-component polyurethane resin for chip-on-board LED micro lenses

“…In order to obtain additional information, mainly on the film thicknesses, to be integrated into our fitting model for accurate k and n determination, thin film interferences were evaluated as well. The interference data were obtained by a self-built reflectometer setup (DeepView), described elsewhere [40]. The setup provides a spectral resolution of ∼ 0.6 nm in a wavelength range of about 400-600 nm and good interference contrast.…”

“…Contact angles of polyurethane resPUR-OT on different modified substrates: (left) glass with the surface tension of σ d = 35 dyn/cm and σ p = 31 dyn/cm and (right) polytetrafluorethylene (PTFE) modified glass substrate with the surface tension of σ d = 14 dyn/cm and σ p = 2 dyn/cm, measured by contact angle measurements with water and methylene iodide. Both surfaces are used for the determination of the surface tension of the liquid polyurethane according to [38][39][40]. Figure 5 and 6 shows R&T spectra of PU thin films.…”

Electromagnetic analysis for optical coherence tomography based through silicon vias metrology

“…Several optical techniques can be used for measuring TSV depths, including spectral reflectometry [4][5][6][7][8][9][10][11], backside infrared spectral reflectometry [12][13][14], ellipsometry (for rather shallow trenches) [15], confocal chromatic microscopy [16] and time domain OCT [16][17][18][19], and hybrid systems [19,20]. Time domain OCT, whose principle is sketched in fig.…”

“…Works on TSV height measurement by any optical technique incorporate up to our knowledge either non-electromagnetic models for light propagation inside TSV [4][5][6][7]26] or time-consuming rigorous computations with the Rigorous Coupled Wave Analysis (RCWA) [8][9][10][11]. This paper aims at an estimate and improvement of the accuracy of TSV depth measurements by application of electromagnetic but rapid calculations.…”

“…This paper aims at an estimate and improvement of the accuracy of TSV depth measurements by application of electromagnetic but rapid calculations. Although our work is focused on time domain OCT, any optical measurement technique such as spectral reflectometry [4][5][6][7][8][9][10][11][12][13][14] could benefit from the results of our rigorous modal calculations at single TSVs based on Fourier-Bessel functions [27,28] and our simplified yet accurate, more efficient models derived from it.…”