Depth profiling

Analysis of silicon nitride thin films

This work was done in cooperation with National Institute of Chemistry and Faculty of Electrical Engineering, Ljubljana, Slovenia.

Silicon Nitride thin films were produced by Plasma-Enhanced Chemical Vapour Deposition (PECVD) applying NH3 and SiH4 gas flow. Depth concentration profiles of hydrogen, nitrogen and silicon have been measured in several samples deposited at different gas ratios.

Experimental details:
  • RBS detector at scattering angle 1500
  • ERDA detector at the angle 300
  • He projectiles, energy 3.3 MeV
Simulation of the RBS and ERDA spectra was performed by the SIMNRA code:
  • from the RBS spectra the impact dose and Si/N concentration ratio was determined
  • from the known dose, hydrogen depth profile was evaluated
  • fitting procedure was done in few iteration steps

top right: Experimental and simulated ERDA spectra of hydrogen recoils.
Top left: the experimental and simulated RBS spectra of the sample. The target structure in the simulation:
  1. Si:N:H=0.35:0.40:0.25, thickness 4.4 1018 at/cm2
  2. 0.40:0.45:0:0.15, thickness 0.7 1018 at/cm2
  3. Si:H=0.96:0.04, thinckness 0.6 1018 at/cm2
  4. bulk Si

Study of hydrogen in helium niobate

This work was done in cooperation with Department of Inorganic Chemistry, Institute of Chemical Technology, Prague, Czech Republic. (see M. Budnar, et.el., NIM B161-163 (2000) 568-572)

Lithium Niobate crystals are a common material for the production of optical waveguides. In the first step of fabrication, a part of the lithium ions in a crystal is substituted by protons with proton exchange (PE) technique. A large increase of extraordinary refractive index value of PE waveguides is observed. To restore and stabilize the optical properties, the waveguides were annealed in the second step of fabrication.

We measured hydrogen depth profiles after each step of fabrication in X - and Z- cuts of lithium niobate in order to study the mechanism of proton incorporation into the crystal.

Experimental details:
  • He beam with energy of 1.8 MeV
  • simultaneous RBS and ERDA measurements were performed
Analysis:
  • simulation of the RBS and ERDA spectra was done by the SIMNRA code
  • from the RBS spectra the impact dose was determined
  • with the known dose, hydrogen ERDA spectrum was fitted

Top left: Hydrogen depth profiles after the first step of waveguide fabrication (Proton Exchange, PE) for 2 different times of PE and 2 different crystallographic cuts. Orientation of the X-cut allows better permeability for diffusing protons.
Top right : Hydrogen depth profiles after the second step of waveguide fabrication - annealing. After this step the concentrations of hydrogen are lowered.

Contact person:

Dr. Primož Pelicon


Last updated: 01/22/2014