In this paper, we propose an unique metrology technique for the measurement of three-dimensional (3D) nanoscale structures of semiconductor devices, employing imaging-based massive Mueller-matrix spectroscopic ellipsometry (MMSE) with ultra-wide field of view (FOV) of 20×20 mm2. The proposed system enables rapid measurement of 10 million critical dimension (CD) values from all pixels in the image, while the conventional point-based metrology technique only measures a single CD value. We obtain Mueller matrix (MM) spectrum by manipulating wavelength and polarization states using a custom designed optical setup, and show that the proposed method characterizes complex 3D structures of the semiconductor device. We experimentally demonstrate CD measurement performance and consistency in the extremely large FOV, and suggest that the combination of MMSE and massive measurement capability can provide valuable insights: fingerprints originated from the manufacturing process, which are not easily obtained with conventional techniques.
In recent years, the overlay specifications of advanced semiconductor devices have become extremely stringent. This challenging situation becomes severe for every new generation of the device development. However, conventional overlay metrology systems have limited throughput due to their point-based nature. Here, we first demonstrate the novel imaging Mueller-matrix spectroscopic ellipsometry (MMSE) technique, which can measure the overlay error of all cell blocks on a device wafer with extremely high throughput, much faster than conventional point-based spectroscopic ellipsometry (SE) technologies. It provides the super large field of view (FOV) ~ 20 × 20 mm2 together with high sensitivity based on Mueller information, which will be truly innovated solution not only for the overlay metrology, but also for critical dimension (CD) measurement, eventually maximizing process control and productivity of advanced node.
Understanding the band alignment at metal/2D semiconductor (SC) contacts is essential for electrical characterizations of 2D SC materials and for fabrication of high performance 2D SC devices. Many researchers have attempted to understand the electrical properties of metal/2D SC contacts and have revealed that they have unique features distinct from those of 3D SC counterparts. In this work, we investigated the surface potential (Vsurf) of exfoliated MoS2 flakes on bare and Au-coated SiO2/Si substrates using Kelvin probe force microscopy. The Vsurf of MoS2 single layers was larger on the Au-coated substrates than on the bare substrates; our theoretical calculations indicate that this may be caused by the formation of a larger electric dipole at the MoS2/Au interface leading to a modified band alignment. Vsurf decreased as the thickness of the flakes increased until reaching the bulk value at a thickness of ~20 nm on the bare and ~80 nm on the Au-coated substrates, respectively. This thickness-dependence of Vsurf was attributed to electrostatic screening in the MoS2 layers. Thus, a difference in the thickness at which the bulk Vsurf appeared suggests that the underlying substrate has an effect on the electric-field screening length of the MoS2 flakes. This work provides important insights to understand the band alignment and the charge transport at the metal/2D SC interfaces.
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