V' Au, C' Charles, R' W' Boswell

1
Evolution of stress in plasma-deposited films

• V. Au, C. Charles, R. W. Boswell
• Space Plasma and Plasma Processing, Plasma
  Research Laboratory
• Research School of Physical Sciences and
  Engineering, The Australian National University,
  Canberra ACT AUSTRALIA 0200

Stress-thickness relationship Ex-situ
post-deposition etch-back
ABSTRACT We have investigated the
stress-thickness relationship for single phase
and multiple layers of silicon dioxide films (up
to 1mm thickness) deposited by helicon activated
reactive evaporation, a plasma assisted
deposition with electron beam evaporation. The
stress-thickness behaviour in the initial 400nm
is found to be strongly influenced by the number
of film layers deposited by stop-start
deposition.
Single phase vs multiple layer deposition
In-situ stress-curvature measurement

• We measure a deflection in the laser spot. Two
  considerations to the deflection measured
• a) Increasing film thickness during deposition
• b) Position of laser on the bowed film and
  substrate

• Bowing due to stress plotted as a function of
  film thickness. The bowing was measured using a
  Tencor P-10 surface profiler.
• A linear relationship of the form B mtc was
  determined for bowing vs film thickness.

Experimental deposition details

• The helicon activated reactive evaporation
  system (HARE) is a low temperature (200?C), low
  pressure (10-6 Torr), high density plasma
  deposition system.
• Solid source silicon is evaporated by the e-beam
  transported through an oxygen argon plasma
• In-situ stress-curvature measurements can be
  performed, as shown below

Experiment
Model

• Multiple layer deposition the distinct
  depositions of the 4x ATM PR sample are clearly
  shown.

• Single phase deposition measurements taken at 5
  minute intervals indicate the deflection trend
  during a continuous deposition of approx. 30
  minutes. Deflection occurs in both cases when a
  deposition is stopped and most distinctly when
  the system is brought to atmospheric pressure.

CONCLUSIONS By employing both an ex-situ
post-deposition etch-back technique and an
in-situ stress deflection measurement method, we
have shown the stress within a single phase
continuous film deposition to differ remarkably
strongly from that of a multiple layer
stop-start deposition, despite comparatively
little variation in the final measured stress of
the total film thickness. The in-situ deflection
method appears to be a promising direct and
non-invasive technique for the measurement of
stress during deposition. Calibration of the
laser setup is being undertaken.
Experiment

• Ex-situ stress study SiO2 films of 1mm total
  thickness were deposited a single phase
  continuous film of 1 layer x 1mm, and multiple
  layer depositions of 2 layers x 0.5mm, 4 layers x
  0.25mm and 8 layers x 0.125mm
• E-beam plasma were OFF between layer
  depositions for 1.5 minutes.
• In-situ stress-curvature study Deflection due to
  stress-induced curvature was measured during the
  depositions of a single phase 1mm thickness SiO2
  film and a multiple layer 4 x 0.25mm SiO2 film.
• Deposition system was brought to atmospheric
  pressure (ATM PR) between layer depositions. One
  layer was deposited per day.

Model