OHS017
OHS Risk Assessment and
Control Form
Faculty/Division: Faculty of Science
DVC Research
Document number
RA02.01
Initial Issue date
July 2008
Risk assessment completed by: Peter Reece
Staff Number: s2173999
School/Unit:
School of Physics, Optoelectronics Group
UNSW Analytical Centre
Current version
Current Version Issue date
1.0
July 2008
Next review date
July 2009
For additional information refer to the OHS Risk Assessment and Control Procedure, the OHS Risk Rating Procedure and the Hierarchy of Risk Controls.
Risk Assessment title: Electrochemical anodization of silicon wafer to form porous silicon.
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Risk Assessment and Control Form RA02.01
Date Effective: 01/07/2008
Uncontrolled document when printed
Current Version: 1.0, 01/07/2008
Step 1: Identify the activity
Electrochemical anodization of silicon wafer to form porous silicon.
The following section outlines the main procedure for electrochemical etching silicon using ethanolic HF etching solution. This procedure may only be carried out
by someone who is fully conversant in the proper usage of the electrochemical cell. Appropriate training will be provided by the process/equipment owner (Dr P
Reece) before inducted users are signed off by the lab manager for this process.
4.1
When handling and decanting from concentrated HF etching solutions inside the fume cupboard, a lab coat, safety goggles, nitrile examination gloves and
medium weight Viton or nitrile over-gloves must be worn. Throughout the etching and detachment process the sash of the fume-hood should be pulled
down enough to eliminate the potential risk of splashes induced by pipette tip flicks.
4.2
Cleave silicon wafer pieces to an appropriate size for the electrochemical cell to be used.
4.3
Ultrasonically clean the wafer pieces in 10mL of acetone followed by 10mL of ethanol; rinse in deionised water (milli Q) and then dry in nitrogen gas flow.
Discard the acetone and ethanol to the solvents waste.
4.4
Mount the silicon into the recess at the back of the upper chamber of the electrochemical cell using a Viton o-ring to make a liquid-tight seal between the
polished face of the silicon and upper chamber of the cell (which will contain the etching solution).
4.5
Place the stainless steel electrode in contact with unpolished back surface of the wafer and screw in the outer Teflon shell to ensure pr oper electrical and
mechanical connection. Invert the cell and place inside the fume cupboard. Connect the bottom stainless steel electrode to the programmable power
supply.
4.6
Pour approximately 50ml of HF etching solution into the top chamber of the electrochemical cell and insert the Teflon lid containing the top platinum
electrode; the electrode ring will be immersed in the etching solution.
4.7
Connect the top electrode to the programmable power supply and perform the etching sequence.
4.8
Remove the Teflon lid and rinse any residue from the top electrode using ethanol; place rinse waste into a beaker marked HF waste.
4.9
Return the HF etching solution to its original container using a pipette (PTFE or polyethylene).
4.10 OPTIONAL: If electrochemical detachment of the porous silicon layer is required, pour in approximately 50 mL 15% ethanolic HF acid solution into the cell;
return the Teflon lid and apply the appropriate etching sequence. Remove the Teflon lid and rinse any residue from the top electrode using ethanol; place
rinse waste into a beaker marked HF waste.
4.11 Rinse the top chamber of the electrochemical cell twice with ethanol, discarding the waste at after each rinse (via a pipette) into a beaker marked HF waste.
4.12 Release the etched wafer from the electrochemical cell with tweezers and immerse in approximately 10 mL of pentane. Remove from pentane and dry the
sample in nitrogen gas flow.
4.13 Discard the contents of the HF waste beaker to the container marked low concentration HF waste.
4.14 Return ethanolic HF acid etching solution to the corrosives cabinet.
4.15 Discard the pentane to the solvents waste.
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Risk Assessment and Control Form RA02.01
Date Effective: 01/07/2008
Uncontrolled document when printed
Current Version: 1.0, 01/07/2008
Describe the location: Old Main Building K15, Room LG48A.
Step 2: Identify who may be at risk by the activity
A number of people may be at risk from any activity. This may affect the risk controls needed. These people may include fellow workers, visitors, contractors and the public. The location of the activity
may affect the number of people at risk.
Researchers intending to be involved in the electrochemical etching activities: Peter Reece, Hong.
Risk associated with other users of the facility, including researchers, contractors and cleaning staff.
Steps 3 to 7: Identify the hazards, risks, and rate the risks
1. An activity may be divided into tasks. For each task identify the hazards and associated risks.
2. List existing risk controls and determine a risk rating using the UNSW Risk Rating Procedure.
3. Additional risk controls may be required to achieve an acceptable level of risk. Re-rate the risk if additional risk controls used.
Tasks
Hazards
Associated risks
(Step 3)
(Step 4)
Risk rating with existing
controls *
Additional risk controls
required
Risk Rating with
additional controls *
(Step 5)
(Step 6)
(Step 7)
Existing risk controls
C
Use of solvents for
rinsing: acetone, ethanol,
pentane.
Inhalation of vapour
Spill and exposure to skin
and eyes
Irritation to respiratory
tract
Skin and eye irritation
Handling in fume hood
2
L
D
R
L
(Apply the hierarchy of
risk controls)
No further risk controls
necessary.
C
2
L
D
R
L
Use PPE (gloves &
goggles)
Handle small quantities
and dispose of waste to
solvents waste container
Highly flammable
Extremely flammable
(pentane)
Risk of fire
Keep away from ignition
sources
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Risk Assessment and Control Form RA02.01
Date Effective: 01/07/2008
Uncontrolled document when printed
Current Version: 1.0, 01/07/2008
Electrochemical etching of
silicon using concentrated
ethanolic HF acid.
Inhalation of
concentrated HF vapour
HF spill and exposure to
skin and eyes
Highly corrosive to mucus
membranes and
respiratory tract.
Potentially fatal.
Serious tissue damage,
Fluoride poisoning,
decalcification of bone,
burning, fluorosis as a
consequence of long
exposure, potentially
fatal.
Corrosive to eyes,
permanent eye damage,
blindness.
Conduct process in a
fume cupboard rated for
HF handling
4
D
M
Use the following PPE:
nitrile examination gloves
and medium weight nitrile
over-gloves; goggles and
lab coat.
1. Ensure that another
trained researcher is
aware that the procedure
is being performed and
that they are available at
short notice.
4
E
M
2. The HF waste is
neutralised upon disposal
and stored as low
concentration HF (< 1%)
waste. No more than 10L
of waste is stored in the
lab.
Decant only small
quantities (up to 100mL)
of concentrated HF and
remove and neutralise
spent HF waste to
appropriate waste
container.
During HF handling lab
restrict lab access to only
researchers involved in
the process.
Have HF acid spill kit
available at all times.
Have first aid kit and
emergency shower and
eye wash available at all
times.
Have calcium gluconate
available in the lab.
Drying of etched silicon
using reticulated nitrogen
gas flow.
Keep solvents away from
ignition sources
Highly flammable solvent.
Risk of fire
Asphyxiation in high
concentrations
Loss of consciousness
and potentially fatal.
* C = consequence
Control the nitrogen gas
flow with a hand held air
gun.
L = likelihood
R = risk rating
3
E
L
No further risk controls
necessary.
3
E
L
from the UNSW Risk Rating Procedure
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Risk Assessment and Control Form RA02.01
Date Effective: 01/07/2008
Uncontrolled document when printed
Current Version: 1.0, 01/07/2008
Step 8 Documentation and initial approval
Completed by: (name)
(signature)
Authorised by: (name)
(signature)
Date:
Step 9: Implement the additional risk controls
identified
Indicate briefly what additional risk controls from Step 6 above were implemented, when and by whom.
Risk control:
All researchers have calcium gluconate gel at home
Date: May 2008
Implemented by: Prof. J.J. Gooding.
Risk control:
Date:
Implemented by:
Risk control:
Date:
Implemented by:
Risk control:
Date:
Implemented by:
Risk control:
Date:
Implemented by:
Step 10: Monitor and review the risk controls
It is important to monitor risk controls and review risk assessments regularly. Review is required when there is a change in the process, relevant legal changes, and where a cause for concern has
arisen. Reviews could be scheduled on an annual basis. If the risk assessment has substantially changed a new risk assessment is warranted.
Review date:
Reviewed by:
Authorised by:
Review date:
Reviewed by:
Authorised by:
Review date:
Reviewed by:
Authorised by:
Review date:
Reviewed by:
Authorised by:
Review date:
Reviewed by:
Authorised by:
Documentation
It is a requirement that legal and advisory documentation that supports this risk assessment be listed. Such documentation includes Acts, Regulations, Australian Standards and Codes of Practice,
where applicable.
Office of environment, Health and Safety, University of California, Berkeley (http://www.ehs.berkeley.edu)
Section B2.15 of AS 2243.2:1997
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Risk Assessment and Control Form RA02.01
Date Effective: 01/07/2008
Uncontrolled document when printed
Current Version: 1.0, 01/07/2008
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Page 6 of 6
Risk Assessment and Control Form RA02.01
Date Effective: 01/07/2008
Uncontrolled document when printed
Current Version: 1.0, 01/07/2008