iii-v precursor delivery solutions for large scale si …€“ liquid precursors – solid...
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© 2010 SAFC Business confidential
III-V precursor delivery solutions for large scale Si applications
Simon Rushworth
SAFC Hitech, Bromborough, UK
EMRS Symposium H Thursday 10th June 11.45
© 2010 SAFC Business confidential
Outline
• Introduction
• Experimental set up
• Consistent flux delivery
– Liquid precursors
– Solid precursors
• Large scale delivery
– Liquid precursors
– Solid precursors
• Conclusions
© 2010 SAFC Business confidential
Introduction
• Metalorganic precursors are vaporised and fed to the growth chamber where they are employed to deposit thin films on heated substrates in a controlled manner
• To achieve the compositional control required the delivery of chemical vapours to the chamber must be highly uniform and scalable
Tim e
Ga
s p
ha
se
Co
nc
en
tra
tio
n
© 2010 SAFC Business confidential
Introduction
• Metalorganic precursors are vaporised and fed to the growth chamber where they are employed to deposit thin films on heated substrates in a controlled manner
• To achieve the compositional control required the delivery of chemical vapours to the chamber must be highly uniform and scalable
G as flow rate
Ga
s p
ha
se
Co
nc
en
tra
tio
n
© 2010 SAFC Business confidential
Introduction
• In III-V compound semiconductor MOVPE the molecules employed are highly reactive and hazardous hence high integrity systems must be used to avoid release as well as ensure contamination does not occur
TMG under nitrogen
© 2010 SAFC Business confidential
Introduction
• In III-V compound semiconductor MOVPE the molecules employed are highly reactive and hazardous hence high integrity systems must be used to avoid release as well as ensure contamination does not occur
TMG in air
© 2010 SAFC Business confidential
Introduction
• Chemicals supplied in high integrity vessels as below
Simple and complex geometries have been
developed to maximise
precursor contact with
carrier gas
© 2010 SAFC Business confidential
Experimental set upNitrogen
cylinder line
getters MFC
MFC
Press.
gauge
Epison
Trap Press.
control
Pump
V1
V2
V3A V4A
V6 V7
V5
V8 V9 V11V10
V14V13
V15
V12
VB1 VB2
V3B V4B
V16 V17
V19V18
Test vessel
(inc precursor)Measurement cell
Gas control manifold
Pressure
control unit
Vapour collection
© 2010 SAFC Business confidential
Typical liquid source plot
Cross dip leg
design beneficial
for larger bubbler
diameters to
improve stability of output
Solution TMIn Standard, 10°C, 300sccm, 500mbar in Crossed Dip
Leg Bubbler
0.1
0.11
0.12
0.13
0.14
0.15
10:1
6:02
:14
10:2
0:19
:06
10:2
4:35
:14
10:2
8:52
:06
10:3
3:08
:14
10:3
7:25
:06
10:4
1:41
:14
10:4
5:58
:06
10:5
0:14
:14
10:5
4:31
:06
10:5
8:47
:14
11:0
3:04
:06
11:0
7:20
:14
11:1
1:37
:06
11:1
5:53
:14
11:2
0:10
:06
11:2
4:26
:14
11:2
8:43
:06
11:3
2:59
:14
11:3
7:16
:06
11:4
1:32
:14
Time
Epis
on R
eadin
g (%
)
© 2010 SAFC Business confidential
Solid Precursor Issues
Channelling
degrades
performance over time
© 2010 SAFC Business confidential
Improved solid source bubblers
Reverse Flow Dual chamber Perforated Disc
© 2010 SAFC Business confidential
Disc Bubbler Results
0
0.1
0.2
0.3
0.4
0.5
0.6
T im e
Ep
iso
n %
Gas phase concentration measurements for Epiflux
configuration at steady flow using TMI at 17C
EpiFluxTM
vessel data
© 2010 SAFC Business confidential
Next Generation Results
• New design modelling has led to an improved approach suited to larger batch size without compromising dosimetry control
Transport conditions
17C @ 225 torr @ 800 sccm
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 100 200 300 400 500 600 700 800 900 1000
Time
Ep
iso
n
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60 80 100 120
Run Number
Co
nc
en
tra
tio
n
900sccmTheoretical
Experimental data from deposition trials
Data from in-house trials EpiFlowTM vessel data
© 2010 SAFC Business confidential
Bulk delivery Benefits
• Increased uptime
– Eliminate shutdown for bubbler change out
– Eliminate qualification and calibration runs
• Reduced precursor cost
– Eliminate waste of partially used bubblers
– Eliminate post change out purge to vent as well as waste from qualification and calibration runs
• Increased safety
– Minimize volume of precursor at the tool
– Precursor may be stored remote from tool
– Eliminate bubbler change out at the tool
© 2010 SAFC Business confidential
Liquid System Design
• Basic EpiFillTM system design identical to units used in the
silicon industry
• Modified for the safe handling of
pyrophorics
• Simple operation, pneumatic valves, pressure transfer
• Precursor from a bulk reservoir
is transferred to the small tool
vessel to refill insitu rather than
replacing it when empty
Bulk precursor vesselSmall tool vessel
Precursor
transfer lines
NOT TO SCALE
© 2010 SAFC Business confidential
Accurate chemical level measurement
• Capacitance system provides± 1 % accuracy for liquid fill
1 2 3 4 5 6 7 8
100%
0%
S
27 50 6
0
20
40
60
80
100
0 500 1000 1500 2000 2500 3000 3500
Time (days)
% R
ea
din
g
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
© 2010 SAFC Business confidential
Process Time Saving
© 2010 SAFC Business confidential
Vapour System Design
• Basic EpiVaporTM system design identical to units used in the silicon industry
• Modified for the safe handling of pyrophorics
• Simple operation, pneumatic valves, pressure transfer
• Precursor vapour from a bulk reservoir is transferred to vapouriser unit equilibrising tank and output as constant concentration gas stream to tool thus eliminating need for small tool bubblers
• Also vapour transport suitable for sufficiently volatile solid precursors ie Me3In
Bulk precursor vessel
Vapouriser unit
Liquid chemical
transfer lines
NOT TO SCALE
Precursor gas stream output
lines
© 2010 SAFC Business confidential
Stability Test
Ampoule 15 degs, flow 0.2l/m pressure 1000T
0
5
10
15
20
25
30
35
40
10:19:12 10:33:36 10:48:00 11:02:24 11:16:48 11:31:12 11:45:36 12:00:00 12:14:24 12:28:48 12:43:12
Time
Co
nc
en
tra
tio
n (
%)
First 10 Minutes
0
5
10
15
20
25
30
35
40
10:33:36 10:35:02 10:36:29 10:37:55 10:39:22 10:40:48 10:42:14
Very stable
output
recorded
Rapid achievement
of steady
state
© 2010 SAFC Business confidential
Multiple Source Requests
Varying Source Requests
10
12
14
16
18
20
22
24
26
28
30
9:36:00 9:50:24 10:04:48 10:19:12 10:33:36 10:48:00 11:02:24 11:16:48
Time
Pe
nta
ne
%
1 Source 2 Source 3 Source 4 Source 1 Source 4 Source
Very stable
under all
conditions
© 2010 SAFC Business confidential
Conclusions
• To provide organometallic precursor vapours to deposition tools requires specialised equipment
• Health and safety risk from hazardous chemicals must be minimised
• A range of approaches have been investigated to provide controlled dosimetry on large scale
• Optimisation for customer processes can lead to significant cost of ownership benefits
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