Gas temperature measurement in C F 4 , S F 6 , O 2 , Cl 2 , and HBr inductively coupled plasmas

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vol. 27; no. 3; pp. 471 - 478
• Main Authors: Cunge, G., Ramos, R., Vempaire, D., Touzeau, M., Neijbauer, M., Sadeghi, N.
• Format: Journal Article
• Language: English
• Published: American Vacuum Society 01-05-2009
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.3106626

Neutral gas temperature
(
T
g
)
is measured in an industrial high-density inductively coupled etch reactor operating in
C
F
4
,
S
F
6
,
O
2
,
Cl
2
, or HBr plasmas. Two laser diodes are used to deduce
T
g
from the Doppler widths of 772.38 and
811.5
nm
lines absorbed by
Ar
*
(
P
2
3
)
metastable atoms, when a small amount of argon (5%) is added to the gas flow. With the
811.5
nm
beam passing parallel to the wafer,
T
g
near the wafer surface is obtained by laser absorption technique. With the
772.38
nm
beam entering the top of the reactor perpendicular to the wafer surface, the volume averaged temperature is deduced by laser induced fluorescence technique. The volume averaged
T
g
increases with radio frequency power and with pressure, although the temperature near the walls is only weakly dependent on gas pressure. The main effect of increasing the pressure is an enhancement of the temperature gradient between the discharge center and the wall boundary. Due to the thermal accommodation, the authors always observe a significant temperature jump between the surface and the gas in its vicinity. This gap is typically about
200
K
. Gas temperatures for a wide range of pressure and rf powers are reported. These data will be useful to validate and improve numerical models of high-density reactive plasmas.