a study of pretreatment process on selective area growth
TRANSCRIPT
Annealing treatment in N₂ ambient (before RIE and acid treatment)
A problem in the beginning of study
A study of pretreatment process on selective area growth of GaN
using SiN masks S. Man1, R. Kayanuma1, Y. Takei1, T. Takahashi3, T. Ide3, M. Shimizu3,
K. Tsutsui1,K. Kakushima1, H. Wakabayashi1, Y. Kataoka2 and H. Iwai2
Tokyo Tech. 1, Tokyo Tech. FRC2, AIST Advanced Power Electronics Research Center3
Email: [email protected]
Backgroud・ Purpose of this work
Improving quality of epitaxial layers（ELO technology）
Fabrication technique of nano devices
Promising for forming a three dimensional structure with
a high quality
a variety of
applications
mask
GaN GaN
MOCVD
Reasons for using SiN mask・Subject
Selective area growth of GaN
It was reported that GaN is not grown on SiN.
Oxygen contamination to GaN by SiO2 mask will be suppressed.
Acid treatment
Experimental Procedures:
SiN GaN
2µm
・Growth of GaN was not
observed.
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Some pretreatment processes are required to solve the problem
that GaN was not grown.
・GaN was grown with island
shapes
5µm
GaN SiN
Acid treament to clean GaN surface had some effects for GaN
growth. However, GaN was not grown appropriately.
RIE(reactive ion etching) treatment
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
depth：20nm
GaN SiN
5µm
・GaN was grown as a continuous
film.
・The surface of grown GaN was
rough.
RIE treatment was effective for growth of GaN. However, surface
roughness and inhibition of growth near SiN mask were problems.
Annealing treatment in MOCVD reactor (between RIE and acid treatment)
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
Sapphire
GaN
SiN
We expect to establish the process of the
selective area growth of GaN using SiN mask
so that GaN is grown appropriately as in the
right figure.
Purpose of this work
GaN
SiN mask
SiN GaN
5µm
SiN GaN
5µm
Annealing treatment in MOCVD reacto rwas remarkable to solve the
problem that GaN was not grown near the SiN mask edges.
However, surface roughness of grown GaN was remained.
(something on the GaN
surface inhibited GaN
growth ?)
SiN GaN
5µm
SiN GaN
5µm
Process of selective area growth of GaN using SiN mask has not been
established yet.
Conclusion
・For growth of GaN, RIE treatment is more effective than acid treatment.
SiN
GaN
Sapphire
1. Deposition of
SiN films on
GaN epi-layer
(by sputtering method)
Resist SiN
GaN
Sapphire
3. SiN etching by BHF
for 5min.
Resist
SiN
GaN
Sapphire
2. Resists patterning
to form
stripe windows
(by photolithography)
4. Resists were removed
5. GaN was grown
by MOCVD with
conditions for 300nm
growth at 1040℃
Grown GaN
Sapphire
GaN
SiN
Results（by SEM）:
(a) plane veiew (b) cross section
Fig 1. SEM micrographs after GaN selective growths
Experimental Procedures (partially omitted):
Treated by
H2SO4/H3PO4(3:1) 200℃ 30min
Resists were removed The growth of GaN
Results（by SEM）:
Fig 2. SEM micrographs after GaN selective growths with acid treatment
(a) plane view (b) cross section
(Some of inhibitors were
removed？)
Experimental Procedures (partially omitted):
Treated by
RIE with BCl3 and Cl2 gas Results（by SEM）:
Fig 3. SEM micrographs after GaN selective growths with RIE treatment
(a) surface (b) cross section
・GaN was not grown near the SiN
mask edge.
Experimental Procedures (partially omitted):
Treated by RIE
with BCl3 and Cl2 gas
Treated by annealing with
NH₃+H₂, 1040℃, 10min
（in MOCVD reactor）
Treated by
H2SO4/H3PO4(3:1)
150℃ 1h
Resists were removed The growth of GaN
The growth of GaN
Results（by SEM）:
Fig 3. SEM images after GaN growths without and with annealing treatment in MOCVD reactor. (a) without annealing (b) with annealing
・GaN was grown as a continuous
film.
・The surface of grown GaN was
rough.
・GaN was grown appropriately
near SiN mask edges.
Experimental Procedures (partially omitted):
Treated by annealing in
N₂, 1040℃, 10min
（by RTA: rapid thermal process）
Treated by
H2SO4/H3PO4(3:1)
150℃ 1h
The growth of GaN Treated by RIE
with BCl3 and Cl2 gas
Results（by SEM）:
Fig 3. SEM micrographs after GaN growths with annealing treatment by RTA in N2 ambient. (a) ) plane view (b) cross section
・GaN was grown appropriately
near SiN mask edges.
・The surface of grown GaN was
flattened.
Annealing treatment in N2 before RIE and acid treatment is
remarkable to solve the problem of surface roughness of grown GaN.
・By annealing treatment, GaN was grown appropriately near SiN edges.
・Surface roughness of grown GaN was suppressed by changing the order
and conditions of annealing treatment. Further optimization is expected.