III-V precursor delivery solutions for large scale Si …€“ Liquid precursors – Solid precursors • Large scale delivery – Liquid precursors – Solid precursors • Conclusions

© 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


Outline

• Introduction

• Experimental set up

• Consistent flux delivery

– Liquid precursors

– Solid precursors

• Large scale delivery

– Liquid precursors

– Solid precursors

• Conclusions


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

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Co

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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

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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


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


Introduction

• Chemicals supplied in high integrity vessels as below

Simple and complex geometries have been

developed to maximise

precursor contact with

carrier gas


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


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 (%

)


Solid Precursor Issues

Channelling

degrades

performance over time


Improved solid source bubblers

Reverse Flow Dual chamber Perforated Disc


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


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


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


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


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


Process Time Saving


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


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


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


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

Documents

III-V precursor delivery solutions for large scale Si …€“ Liquid precursors – Solid precursors • Large scale delivery – Liquid precursors – Solid precursors • Conclusions