Procedure - General Clean Room Chemical Work
In addition to standard chemical safety procedures


Make sure the DI water is turned on in the service bay.
Do not leave the clean room while you have any chemical procedures in process.

Chemical Gloves (orange gloves)
o After use, rinse the chemical gloves thoroughly with DI from the faucet or DI water gun.
o Dry the chemical gloves with either a towel or nitrogen gun.
o Do not pull the gloves inside out when removing them. The gloves will not dry properly if stored
inside out and it puts liquids on the inside of the glove.
o Store the gloves organized in pairs.
Chemicals gloves inside out

Chemical gloves properly dries and stores in pairs
Timed faucet
o The left hand faucet is controlled by a timer. It will start when the button is pressed and will stop at
the end of 75 seconds. Do not turn off the valve on the faucet or the valve on the front panel. This
faucet is useful for rinsing chemical bottles, chemical beakers and containers, tweezers, and gloves.
Chemical bottle rinsing under timed faucet

Timed faucet activation buton
Empty chemical bottles
o When a chemical bottle is used up and empty, rinse three (3) times and put by the trash can in
the chemical room without the bottle cap. This lets the lab manager know the bottle has been
rinsed. Write “rinsed” and the date on the bottle label.
Rinsed chemical bottle placed by the trash can in the chemical room

Chemical Containers
o When you are finished with a container (dishes, beakers, etc.), rinse and leave open end up
under the chemical hood. Putting the container open end down does not allow it to dry.
o There are two containers that contain HF (Hydrofluoric Acid). One is 10 parts DI water to HF
(10:1 HF) used in the wafer cleaning and one is BOE (Buffered Oxide Etch) used for etching SiO2
o When moving wafer carriers from chemicals to rinse tanks, always place a tray under the wafer
carrier to catch any dripping chemicals

Wafer cleaning
o There are pre-marked containers for use in measuring the hydrogen peroxide and sulfuric acid.
Use them. It is not necessary to get an exact amount, close to the mark is acceptable. Used
hydrogen peroxide/sulfuric acid should be dumped in the used hydrogen peroxide/sulfuric acid
peroxide container once the mix has stopped reacting.
Beakers for sulfuric/peroxide with marks for amount of each
Containers for used sulfuric/peroxide
o When finished, be sure to wipe down the chemical hood surface area with a towel and then
rinse the towels in DI water thoroughly before disposing in the rash.
o Only tweezers with a green tape are to be used for chemical work. Tweezers should be rinsed
and dried after use. Wet tweezers will leave a stain on clean wafers!
o There is a rinse tank at the corner of the fume hood, near the tweezers beaker. It can be used
as a pre-rinse. Dip the wafers in the tank with the DI running for a few seconds and then put
the wafer carrier into the normal cascade rinse tank. This will allow the normal cascade rinse
tank to reach the required resistivity quicker. Turn off the DI when not in use.
Front rinse tank and valve for quick rinse prior to using the cascade rinse tank

Cascade rinse tank (where water enters from the bottom and overflows the top like a dam)
o The DI water quality is measured with a water resistivity (conductivity) meter. Higher resistivity
means less mobile ions and contaminants in the water. When wafers with residual acids are
immersed in the DI cascade tank, the resistivy drops and as the wafer rinses away the acid
contamination, the water resistivity increases.
o The resistivity meter for the cascade rinse tank is located on the control panel above the deck.
It has two ranges, kilo-ohm and mega-ohm. Occasionally the meter will begin reading in kiloohm. Be sure the reading is in mega-ohm and meets the minimum resistivity of the DI wafer
before removing the wafers.
o The resistivity reads 25 mega-ohm when there is no DI water running as the probe is in free air
with infinite resistivity. Once DI water starts to flow and cover the probe, a normal resistivity
will be shown.
o Also occasionally, the resistivity meter goes into alarm mode. You can usually return it to
measuring the resistivity of the wafer by pressing the “ACK” “RES” or “Range”.
Cascade rinse tank resistivity meter
Cascade rinse tank valve

Rinser/dryer
o The rinser/dryer is only used in the dry mode. The nitrogen needs to be turned on before use
and turned off after use.
o The wafer carrier with the yellow and red buttons is the only wafer carrier to be used in the
rinser/dryer.
o Be sure the open end of the wafer carrier is facing up to prevent the wafers from falling out
when you remove the carrier.
o Wafers can be flipped transferred to your wafer box (and eliminate touching the clean wafers
with a tweezers) if you carefully align the pins and holes on each carrier
Yellow and red button wafer carrier for the rinser/dryer

Two wafer carriers aligned for flip transfer
Consumables – Nitrogen and DI water
o Be sure to turn off the DI cascade rinse tank when done rinsing your wafers. DI water is very
expensive and should not be wasted.
o When using the rinse/dryer, be sure to turn off the nitrogen after. The wafer carrier in the
rinse/dryer is unique and is not interchangeable with the other wafer carriers.