Accelerating Sustainable Manufacturing

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III-V Materials ESH and

Process Hazards

Steven R. Trammell, P.E. Steve.Trammell@ismi.sematech.org

SEMATECH Symposium

Korea 2012

Why Gallium Arsenide (GaAs)?

• For the 10-7nm tech node strained silicon is expected to

reach low power performance limits, requiring alternative

channel materials

• Higher electron mobility allowing functionality at higher

frequencies (i.e. faster than Si transistors)

– Applications: mobile phones, satellites

• Recent advances in processing with GaAs

– Scaling and throughput has been the historical challenge

– Recent success in layering of GaAs structures on Si substrates

• Challenges

– Introduction of thin buffer III-V materials on Si in High Volume

Manufacturing platforms

16 October 2012 2

Overview of III-V materials

16 October 2012 3

Current elements of interest:

Ga, In, As, Sb

Coming soon:

P, others??

III-V compounds – semiconductors, PV

Other compounds – photovoltaics, etc.

III-V material / process ESH ISMI Studies

• As / AsH3 Exposure Potential

– Operations and Maintenance

– Equipment Surface Contamination

– Exhaust and Effluents

• Process Equipment Issues

– Cross Contamination of Equipment

– Off-gassing of Post Processed Wafers

• Facility and Infrastructure Issues

– Handling of Pyrophoric Precursors, Toxic Gases, H2

– Maintenance of Support Equipment, Ducts, etc.

• Waste / Effluent Issues

– As Detection in Complex Waste Streams

– Treatment / Removal Technologies

– Solid Waste Handling

16 October 2012 4

Arsenic and arsine exposure limits

* SEMI S-12, Section 10.1, Table 5

Exposure Limits Arsine Arsenic

- in air

Arsenic –on

Surfaces

(mg/m3) (mg/m3) (mg/100 cm2)

NIOSH REL (15 min Ceiling) 0.002 0.002 -

NIOSH Immediately Dangerous to Life

and Health (IDLH)

10

(from 3 ppm)

5 -

ACGIH TLV 0.016 0.01 -

OSHA Action Level – Continued

Monitoring Required

- 0.005 -

OSHA PEL 0.200 0.010 -

SEMI Decontamination Level* - - 0.050

16 October 2012 5

III-V Benchmarking

• Benchmarking of traditional III-V GaAs

manufacturers to determine:

– General ESH best practices for As, AsH3

– Hazardous materials handling (H2, Hydrides)

– Tool specific hazards

(MBE, MOCVD, CMP)

– Exhaust / Waste water

treatment options

16 October 2012 6

Exhaust Treatment Example

III-V Benchmarking

16 October 2012 7

• Hazardous Materials

Handling

Materials Delivery

Example

As detection in waste water

• Waste water discharge limits for As vary widely

by location

• Detection to 2 ug/L is needed

– Laboratory methods (ICP-MS or TXRF) is possible

– In-situ methods are a challenge

16 October 2012 8

TXRF showed promising results to 20 ug/l. Additional studies underway.

Off-gassing evaluations - IMEC

16 October 2012 9

Source: IMEC

34th Annual SESHA Symposium, March 2012

Off gassing assessment - CNSE

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Small coupons (III-V films on Si) experiments – chemistries tested are diluted HF

(50:1) and (10:1), HF and Nitric acids

60 sec dip into followed by DI rinse

Experiments carried out in an enclosed 124L glovebox – arsine concentration was

analyzed with CM4 (providing sampling flow of 3L/min with 10sec sampling

intervals)

HF or Nitric

beaker

Sealed glove box (volume : 124L)

CM4

sampling

port intake –

3L/min DI water for

rinse

1. 60sec DIP

2. Rinse

Nitrogen

purge supply

Glove box lid

Off gassing assessment - CNSE

16 October 2012 11

Small coupons experiments – 60 sec dip into HF 10:1 followed by DI rinse in the

enclosed 124L glovebox – arsine concentration analyzed with CM4 (providing

sampling flow of 3L/min)

Preliminary Results:

Experiments Repeated For:

• Concentrated HF

• 50:1 Dilution

• Nitric Acid

• Nitric / HF mixture

Wipe – cassette bottom

• Wafer holder

removed

• Shipping

cassette pre-

cleaned using

10% IPA

• Bottom of

cassette wiped

to determine

baseline

contamination

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Wafer in cassette bottom

• Wafer elevated

for easy

breaking

• III-V layer on top

16 October 2012 13

Wafer break procedure with AsH3

monitor

• Long screwdriver

inserted through

hole in cassette top

• Wafer broken with

singular, forceful

stab in middle

• Test occurred in

laboratory hood

• Exhaust from top to

bottom

16 October 2012 14

Arsine (AsH3) handheld monitor

• Monitor sample

tube opening

held over

opening in

cassette top

• Sample time a

few minutes, as

dust allowed to

settle

• Results: No

detection of

arsine

16 October 2012 15

Broken wafer

• Wafer

shattered into

many shards,

bits and dust

16 October 2012 16

Broken wafer bits

• Wafer bits and

dust

remaining

after dumping

shards into

waste bag

16 October 2012 17

Post-break post-dump bits

• Photo showing

scale of wafer

dust

16 October 2012 18

Post-break post-dump of shards wipe

• Wafer shards

dumped into

waste bag

• Wipe sample

taken of

bottom of

cassette

• Result:

16 October 2012 19

Vacuuming box bottom

• Bits and dust

vacuumed (into

dedicated

HEPA arsenic

vacuum), from

cassette bottom

• There was not

significant

material

adhered to

cassette top

16 October 2012 20

Post-break dump and vacuum clean

• Cassette

bottom

cleaned after

shards

dumped out

and bits and

dust

vacuumed out.

• A 2nd more

aggressive

clean was also

performed.

16 October 2012 21

Wafer break wipe samples

analytical results (Detection Limit = 0.002 mg for Arsenic)

Tool ID/Process Activity Sample Location

As

Results

(mg)

Area

Wiped

(cm2)

Conc.

(mg/100 cm2)

Shipping Cassette Pre-Wafer Break Bottom <0.002 100 <0.002

Shipping Cassette Pre-Wafer Break Side <0.002 100 <0.002

Shipping Cassette Pre-Wafer Break Top <0.002 100 <0.002

Shipping Cassette Post-Wafer

Break Bottom 0.260 100 0.260

Shipping Cassette Post-Wafer

Break Side 0.093 100 0.093

Shipping Cassette Post-Wafer

Break Top 0.047 100 0.047

Shipping Cassette Post-Clean Bottom 0.018 100 0.018

Shipping Cassette Post-Clean Side 0.021 100 0.021

Shipping Cassette Post-2nd Clean Side <0.002 100 <0.002

Wafer Sliver Post-Break Broken Edge <0.002 <5 <0.04

* SEMI S-12, Section 10.1, Table 5 decontamination level is 0.010 mg/100 cm2

16 October 2012 22

Wafer break study summary

• Broken wafers with GaAs layers will release measurable

amounts of arsenic as dust and small particles. – Small particles can be removed with a vacuum.

– Dust can be removed with a wet wipe, but a detailed cleaning is

necessary to remove it all.

– Respiratory protection typically not needed in ventilated/exhausted

areas.

• Edges of broken wafer shards do have measurable

amounts of arsenic. – Arsenic dust settling from wafer break is likely source

– Shards should be swept or vacuumed, or picked up by hand using

thick neoprene or equivalent gloves.

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