Investigation and Control of MOVPE Growth by Combined Spectroscopic Ellipsometry and Reflectance-Difference Spectroscopy

Abstract

The detailed characterization of epitaxial growth by metal organic vapor phase epitaxy (MOVPE) and its closed-loop feedback control at the sample level require a combination of thin-film, nearsurface, and surface-sensitive techniques to determine layer thicknesses and compositions, the composition of the most recently deposited material, and surface chemistry, respectively. These data can be obtained nondestructively by spectroscopic ellipsometry (SE) and reflectance-difference (-anisotropy) spectroscopy (RDS/RAS). We describe the first unified optical system, basically a rotating-polarizer ellipsometer (RPE) integrated within a modified commercial rotating-sample MOVPE reactor, that performs both SE and RDS simultaneously in a single optical path. We provide examples of its use, showing in particular that GaP can intermix with Si during the initial stages of heteroepitaxy, and demonstrating sample-driven closed-loop feedback control of epitaxy through the fully automatic deposition of an In x Ga 1--x P parabolic quantum well. These results illustrate capabilities of the presented configuration and its potential for future use.

Reflection anisotropy spectroscopy

“…Examples of its use include an assessment of the efficiency of As and P precursors in the MOVPE growth of GaAs(001) and InP(001) [251] and the characterization of the dependence of the growth morphology of InGaAs grown on GaAs(001) on the growth rate and pressure of As. The technique has been integrated into commercial growth reactors [252][253][254].…”

Optical Diagnostics for Thin Film Processing

“…Rapid reliable information is now becoming routine by using parallel spectroscopic detection (for spectroscopic or multiwavelength analysis), HERMAN realistic models of the films (including surface and interface roughness and composition uncertainties), and efficient analysis algorithms. Progress in developing and implementing real-time SE has progressed on a range of materials and processes (112,(213)(214)(215)(216)(217)(218), and is expected to continue even deeper in the UV (to the VUV, for photoresists and optical coatings) and the IR (to the mid-and far IR, for phonons and free carriers). In fact, IR SE, which gives sensitivity to vibrations, has been used for real-time analysis of growth (219).…”

Virtual interface approximation model applied to spectroscopic ellipsometry for on-line composition determination of metalorganic chemical vapor deposition grown ternary nitrides

“…For comparison, kinetic reflectometry ͑i.e., dynamic optical reflectivity͒ 11 measurements have been performed in parallel. 12 The main goal of the present work is to verify the feasibility of a future closed loop control of the MOCVD deposition of GaN and Al x Ga 1Ϫx N by means of SE, as it has been already demonstrated for ternary phosphides 13 and arsenides. 14 In this perspective, as a first step we compare reflectometry, which is to date the standard optical technique employed for in situ monitoring of MOCVD nitrides, with ellipsometry as a tool for the in situ control.…”