In situ spectroscopic ellipsometry monitoring of diamond multilayers grown by microwave plasma enhanced chemical vapor deposition

Abstract

Thanks to its unique properties, diamond is intensively investigated for the development of optical and electronic devices. These applications, such as pseudo-vertical Schottky diodes or Bragg mirrors, rely on the synthesis of boron-doped (p+) and non-intentionally doped (nid) stacked epilayer with well-controlled thicknesses, doping level and sharp interfaces. Such structures require a time-consuming optimization of the growth processes throughout the use of destructive techniques such as Secondary Ion Mass Spectroscopy (SIMS), Transmission Electron Microscopy (TEM) or transport measurements. From this perspective, the use of an in situ characterization tool is a considerable asset. In this paper, we demonstrate that spectroscopic ellipsometry, implemented to be used in situ during the Plasma Enhanced Chemical Vapor Deposition (MPCVD) process, is a powerful and non-destructive technique to characterize diamond based devices. Moreover, it can also be sensitive enough to access the gas flow dynamics in the reactor. To this aim, two doped and nid multilayer stack have been investigated. The doping profile of a doped layer, extracted from the optical spectra is compared to the one obtained by SIMS and the growth rate of nid epilayers grown under various flow rate, is derived based on this technique.

Multiparameter Investigation of Diamond Plates with Optical Time-Stretch Quantitative Phase Imaging

“…Conventional detection methods, such as microscopy, Raman, X-ray diffraction, and so forth, can only detect the quality of diamond crystals after growth and just a single parameter or parameters of the same type, after which the growing parameters, such as substrate temperature, gas pressure, and gas concentration, are tuned to improve the growth quality. , Hence, it is difficult to link the product defects with specific growing parameters, and the efficiency of these methods is extremely low. To accelerate the parameter tuning and precisely control the diamond growth, online monitoring methods, which monitor the diamond growth in real time, are essential to improve the quality and yield of diamonds. , However, current online monitoring methods, − including reflection high-energy electron diffraction, optical emission spectroscopy, spectroscopic ellipsometry, and so forth, are still unable to achieve the high-speed, high-quality, and continuous monitoring of the morphology evolution of the diamond crystals, and morphology monitoring is the most intuitive method to detect defects. In order to overcome the shortcomings, optical time-stretch quantitative phase imaging (OTS-QPI) is considered as one of the promising methods for its capability of acquiring images with a frame rate above GHz and a spatial resolution better than 780 nm. − In addition to obtaining “intensity images” by measuring the power of the laser pulses, OTS-QPI can also acquire “phase images” by measuring the transmission delay of light after passing through the target.…”