1. Introduction Techniques Conclusions Contamination control on bulk Ge and GaAs As dopants in Ge S Monolayer passivation on Ge Si passivation and HfO 2 dielectric layers on Ge CMOS for sub-32 nm technology: high-k dielectrics on high-mobility substrates All CMOS Si processes need to be re- engineered: cleaning, dopant activation, passivation, dielectric deposition, etc… Our work: how trace analytical techniques total reflection X-ray Fluorescence (TXRF) and Atomic Absorption Spectrometry (AAS) can assist Fig 2: Application of Direct- and VPD-DC-TXRF in cleaning experiments: (a) Cleaning of controlled contaminated Ge wafers using dilute HF chemistries; measurement before clean: Direct- TXRF, after clean: VPD-DC-TXRF; and (b) Cleaning of ‘real process’ GaAs wafers using controlled oxidation using H 2 O 2 based solutions and etching in HCl based solutions. (no bar indicates a result < detection limit). Conventional application of trace analytical techniques Direct-TXRF for Ge substrates - minor development: sensitivity same than for Si -> no additional calibration standards - higher detection limits than on Si due to more background scattering Vapor Phase Decomposition – Droplet Collection (VPD-DC) pre concentration - major development for each substrate: different wetting properties and matrix removal - Applications in cleaning of Ge and GaAs substrates Ge wafers GaAs wafers Fig. 1: Optimization of S coverage on Ge wafers in a deposition process from gaseous H 2 S, using Direct-TXRF analysis. Approach of chemisorption of (sub)monolayers as preparation for high-k deposition to realize smooth interface Combination of Total Reflection X-Ray Fluorescence (TXRF) and Reflection High Energy Diffraction (RHEED): determination of bonding geometry of S on Ge Quantitative TXRF: accuracy within 10% if relative sensitivity factors are determined Application for gas phase deposition H 2 S on Ge Dopant concentration to be tuned to the application Determination As concentration is challenging application - Mass spectrometry (SIMS, ICPMS): interference 70 Ge (21%) and 75 As (100%) - X-ray methods (ED-XRF): Interference GeK  (10.98 keV) and AsK  at (10.53 keV) Selected method: wet chemical etch + graphite furnace – AAS - selective excitation atomic absorption lines, matrix removal in the ashing steps - etching chemistry: ammonia/peroxide mixture - optimization of etch volume: detection limits down to 3  10 16 As/cm 3 Ge Application on As dopants in GeOI substrates Fig. 4: Method optimization for As dopant determinations in GeOI wafers: validation study for the use of low etch volumes to improve detection limits with one order of magnitude; comparison of results obtained in 1 mL versus 10 mL solution volume. Fig. 5: Coverage analysis of Si on Ge using different techniques: Direct analysis using grazing incidence – XRF and TXRF, or via wet-chemical etching in combination with GF-AAS. The growth rate of the epi process on Si wafers is presented as a reference. Conventional technique for coverage analysis of layers = Rutherford Backscattering Spectroscopy Grazing incidence – XRF technique with high potential also for light layers on heavy substrates (problem for RBS) - combination of experimental recording angle dependent XRF curves and theoretical modeling [4]: rather complex method - demonstrated for ALD HfO 2 on Si TXRF Wet etch + GFAAS - fast; simple calibration - labor intensive; reference method Application for Si layers on Ge -Deviation TXRF from GFAAS and GIXRF: origin in inaccurate calibration factor - All techniques: saturation curve: real effect in growth - Growth at start faster than on Si: formation of super islands? Analytical - TXRF: Atomika 8300W, WL  excitation, 70% crit angle - GFAAS: Perkin Elmer 4110ZL - VPD-DC: WSPS, GeMeTec Materials - Ge: Umicore,, 100mm - GaAs: in house deposited MOCVD or CMK, Processing - Cleaning: immersion in statical chemical bath, HPW overflow rinsing, N 2 dry - S-passivation: H2 bake, H 2 S deposition, temp 80-330 deg C, ambient N 2 or H 2 - Epi Si deposition: ASM Epsilon 2000 reactor, pressure 5.3x10 3 Pa (40 torr), using N 2 as a carrier gas - HfO 2 deposition: ASM ALCVD™ Pulsar 2000 reactor, from HfCl 4 and H 2 O precursors at 300°C and 1 Torr Trace analytical techniques maintain role as work horse in contamination monitoring but more applications beyond this demonstrated Advantages TXRF Quantitative character with accuracies > 90%: showed beneficial for S passivation study Here demonstrated for thin layer analysis Si on Ge Other methods GI-XRF and GFAAS Demonstrated useful for validation purposes (see Si on Ge); GFAAS as technique in case strong analyte selectivity is required (see: As analysis in Ge) Recently also Inductively Coupled Plasma Mass Spectrometry available for applications in Micro- and Trace Analytical Chemistry How Trace-Analytical Techniques Contribute to the Research and Development of Si, Ge and III/V Semiconductor Devices – some examples Fysische en Analytische Chemie Prof. S. De Gendt and Prof. C. Vinckier