Chapter 2.6
Sink6 (MOS Clean)
1.0
Title
VLSI Sink 6
Operation (MOS)
2.0
Purpose
Wet
sink6 provides two sets of piranha baths: HF tanks and quick dump rinse
stations (QDR). There is one piranha bath on the left side. Next to it, there are
two HF tanks in the middle. These are 25:1 HF (49%), and 10:1 HF (49%) tanks
followed by a piranha bath on the right side and two QDR stations in front of
sink6 station.
3.0
Scope
Wet
sink6 is a furnace pre-clean sink. It is to be used for cleaning wafers prior
to initial oxidation (wafers out of the vendor box). This is the last cleaning
step before they go into any furnace. Any wafer that goes into a furnace should
go through this cleaning procedure. NON-MOS processed wafers shall be cleaned
in sink8 first, then go into sink6 as a furnace pre-clean step. MOS processed
wafers, which went through the photo-resist stripping step, should also be
cleaned in sink8 prior to their pre-clean steps in sink6. ABSOLUTELY
NO METAL WAFERS CAN BE PUT IN THIS SINK (ANY METAL).
4.0
Applicable Documents
Chapter 2.1 of
the lab manual, which explains wafer boxes, tweezers, and other tool cleaning
prior to using VLSI sink.
5.0
Definitions and Process Terminology
5.1 Full Plenum Lockout Alarm:
Early warning alarm indicating sink drain failure.
5.2 Quick dump Rinse (QDR): DI
water station programmed to rinse wafers to an acceptable resistivity level
(>10 Mega Ohm-cm), and to get rid of excess acid and/or contaminant.
Therefore, it is very important to make sure cassette/wafers go through full
QDR cycle/s, as any remaining acid can easily ruin the consequent SRD machine
and/or contaminate other equipment in the lab, particularly the furnaces.
5.3
Spin Rinse Dryer (SRD):
DI water rinse followed by a spin dry cycle.
5.4
STAT-PRO 1000 cassette:
Black Teflon® cassette with name STAT-PRO 1000 printed on
their side. These cassettes will minimize static charge built up in the SRD,
hence more appropriate for the device (MOS) processing.
6.0
Safety
Follow the general safety
guidelines for the lab, the safety rules outlined in Chapter 1.2
and the following:
6.1 This sink contains HF acid and
Piranha (heated sulfuric acid). Therefore, appropriate safety attire should be
worn while working at this station. This means chemically resistant gloves
should be worn on top of the surgical gloves, plus a face shield and apron must
be worn at all times while working at or around sink6. Do not use metal
tweezers in this sink. Only clean Teflon® tweezers can be used here.
6.2
Do not adjust the
heater controllers as they have been preset to produce proper temperatures for
the piranha baths.
6.3
Only use the black Teflon® chemically resistance cassettes provided for
this sink. They are marked STAT-PRO 1000 in black color. Failure to do
so can cause damage to the station and/or compromise the operator’s safety.
6.4
Glove Wash: Located in the front
center, right of this sink. Water spray
is sensor activated.
6.5 EPO
red button: Cuts power to the sink in
emergencies. Report promptly on FAULTS.
7.0
Statistical
Process Data
N/A
8.0
Available
Processes, Glove Policy, and Process Notes
8.1 Processing
Furnace pre-clean processes (Piranha
clean and HF dip) are available at this sink as well as the quick dump rinse
process to a desired resistivity for both 4" and 6” wafers. Black STAT-PRO
1000 4” cassettes, 6” cassettes and designated white
Teflon® handles, marked as MOS, are available by the station.
The same cassettes should be used in this sink, then put them into the SRD for
the final rinse. The black STAT-PRO 1000 cassettes are
properly balanced for the SRD by sink6.
DEDICATED BLUE TRANSFER BOXES (4”
and 6” BOXES WITH BLACK STAT PRO CASSETTES IN IT) MUST BE USED FOR TRANSFERRING
PRE-FURNACE CLEANED WAFERS TO THE FURNACE STATION. BRING THE BOX BACK TO SINK6
IMMEDIATELY AFTER WAFERS ARE LOADED IN THE FURNACE.
8.2
Chemical
location
All
sink6 (and 9) chemicals are purchased pre-mixed, except for diluted HF. They
are available in the chemical cabinets in the front lobby. Additional sink6
chemicals can be found in the C-locker in service chase CV2 also (located
between sinks 6 and 7 in the VLSI area of the lab).
8.3
Glove
and Safety Attire Policy
Whenever
you are handling chemicals and/or place wafers into the chemical baths, you
must wear appropriate safety attire:
chemical-resistant gloves on top of surgical gloves, apron, and face shield.
Whenever handling any cassettes or handles from VLSI sink6 (or 9), the poly
gloves (clear gloves) MUST be worn on top of whichever gloves you already have
on.
Example 1: surgical
gloves/poly gloves
Example 2:
surgical gloves/chemical-resistant gloves/poly gloves
Never
touch any surface while wearing chemical-resistant gloves that other lab
members may come into contact with, such as table tops, door handles, computer
keyboards, face shields, aprons, etc. If you need to step away from the sink at
anytime, rinse off gloves at the glove wash, dry with techni-cloths and put
away in your drawer until you are ready to resume your work at the sink.
8.4
Process Notes
The
VLSI Sink 6 (and 9) is maintained for MOS-clean processes. Special care must be
taken when using them. Do not contaminate them. If they are contaminated, they
could have a lab wide/furnace ramification. Staff changes the chemicals in Sink
6 regularly (as per portions defined in Table 1, below). If it appears that any
of the solutions have been contaminated, notify a staff member (or e-mail
processtaff at silicon.eecs.berkeley.edu)
to change it, and post the problem report on FAULTS.
Hint:
If there is a ring around any of the rinse tanks after you remove your wafers,
you have contaminated the tank, cassette, and handle. Report the contamination
on FAULTS immediately.
|
Bath |
Chemicals |
Portions |
|
Heated Baths Left Non-Heated Tank Right Non-Heated Tank |
Sulfuric Acid (Piranha*) 25:1 HF* (49%) 10:1 HF* (49%) |
6000 ml (6 liters) 6000 ml H2O:240 ml HF** (49%) 5500 ml H2O:550 ml HF** (49%) |
Table 1
►
Piranha is made by adding 100 ml of hydrogen peroxide to the sulfuric
acid bath. Use the 100 ml beaker kept next to the hydrogen peroxide bottle on
the table adjacent to the sink. You must add the hydrogen peroxide just before
immersing every batch of wafers. After cleaning your wafers in piranha, they
must rinse in the QDR station. Rinse the wafers until the resistivity reading
is 10 M OHM-CM or higher.
8.5
Wafer Breakage
in the Sink
If you
accidentally break a wafer in either the piranha baths or the HF tanks, first try
to retrieve the broken wafer pieces by using the 10” long Fluoroware tweezers
located on the worktable next the sink. DO NOT PUT METAL TWEEZERS INTO THE
BATHS OR TANKS.
If the wafer pieces cannot be retrieved by this method, you will
need to turn off the heater and let bath cool to 100ºC. Next, drain the piranha. Thoroughly rinse
the bath with DI water; then drain the DI. Retrieve all pieces of broken
wafers; rinse; drain once more; refill the bath with fresh suphuric, then turn
the heater back on. Report the chemical change on FAULTS.
If there is an issue with the solutions in these heated tanks,
report a sink problem via the WAND.
Microlab staff will respond, change baths and clear the FAULT.
9.0
Sink
Operation
The
sink operation is relatively easy, however special care must be taken not to
contaminate this MOS clean station and subsequent processes. The piranha and HF
sinks are set up much like the old sink 6. The main difference is that now
members invoke the dump rinse cycle (QDR) from a special keypad mounted on the
face of the station (one for each station). QDR stations are programmed to run
two complete DI fill/rinse cycles with wafers submerged in the water at the end
of the program.
9.1 Control
Key Description
There are three
control/displays at this station (see Figures 1-3). Members should only need to
use the DUMP RINSER control pad marked as “UFT –48-8 ”. This is the control pad
for the quick dump (QDR) station, which is currently set for two dump rinse cycles.
Wafers are initially showered with DI water followed by two DI fill-dump
cycles. These cycles end with wafers submerged in the water for operator to
extract and place them in the SRD. During the QDR cycle, the resistivity can be
monitored via the UFT-223 RESISTIVITY MONITOR control panel. Piranha bath
temperature can also be read on the UFT-820 TEMPERATURE CONTROLLER display for
each piranha bath. Each station performs a self-clean every 60 minutes by
running one QD cycle automatically.
UFT-820 TEMPERATURE CONTROLLER (Figure 3)
POWER ON/OFF Turns on/off the master power for the
temperature controller (Figure3).
HEATER ON/OFF Turns on/off the heated piranha bath.
TIMER RUN Starts the timer.
TIMER STOP/RESET Stops or resets the timer.
ALARM SIL - Silences the timer and other
alarm conditions.
-
Cancels flashing alpha code in the
displays.
- Examines
the process set point and the Time Preset.
DRAIN Press twice to empty
the baths/tanks. Make sure chemical baths are sufficiently cooled down before
draining. To only drain a small amount, press the DRAIN button twice, then once
again when you want to stop the draining.
PROG Access
to change or step through various setup parameters.
SAVE Permanently
save the system setup parameters.
RESET This
key is utilized to exit the PROGRAM mode.
UFT-223 RESISTIVITY MONITOR (Figure 1)
UP/DSPLY Toggles
between resistivity and temperature readings.
DOWN/CHAN Toggles between the viewing of
channel 1 and channel 2.
RETURN/SIL Silence the alarm. Exit the set
up mode.
UFT-48-8 DUMP RINSER (Figure
3)
START Activates
the dump rinse cycle/ Reactivates dump rinse cycle.
RESET -
Deactivates the Dump Rinser.
-
Silences alarm.
-
Automatically reset itself in preparation for another run.
-
Exits program mode.
HOLD When the system is
running, it halts the operation temporarily. When it is in STANDBY mode, it
dumps the tank manually.
PROG Parameters
to be written in the EEPROM memory.
9.2
Control Key
Functions for Overall Sink Operations (Figure
4)
POWER ON Main
power on for top control panels.
EPO Big red
button for emergency stop on the entire sink operation.
SILENCE
ALARM Silence the plenum flush lockout alarm.
ALARM
RESET Reset the plenum flush system.
9.3
Control Panel
Programs are shown in Appendix 2
The parameter codes for the
programs on the UFT-223 resistivity monitors, UFT-820 temperature controllers
and UFT-48-8 quick dump rinsers are listed in Tables 2-4
in Section 12.2. The parameter codes are not to be altered by the Microlab
members. Please only use them as your reference check.
9.4
Basic Piranha Clean
Piranha
is an excellent oxidant capable of removing most organic contaminants.
9.4.1
Add 100 ml hydrogen peroxide to the heated sulfuric acid bath,
which is kept at 120ºC to activate (spike) the piranha (see Figure
3 for more details on the temperature controller display).
9.4.2
Piranha clean wafers for 10 minutes.
9.4.3
DI water rinse your wafers by carefully lifting the cassette out
of the (piranha) bath, and holding it above the bath until it stops dripping
before placing them in the quick dump rinse station.
9.4.4
Start the DI rinse in the QRD station per the instructions
provided in Section 9.4.3 and make sure you reach proper resistivity level.
9.4.5
HF dip if desired; however, make sure to run another DI rinse in
QDR by repeating step 9.4.3 and 9.4.4.
Note: Repeat
the rinse cycle as described above after each acid clean step done in sink6
(piranha or HF).
9.5
Quick Dump Rinse
(QDR) Operation
This is a two-cycle DI
dump/rinse process that is needed to bring wafers to above 10 Mohm-cm
resistivity before one can proceed to next step in the spin rinse dryer.
Proceed as follows:
9.5.1
Place wafers in the QDR
tank: it should initially have no DI water in it.
9.5.2
Press RESET (if status
light is blinking), then START button to activate the dump rinse cycle (see Figure 3 for keypad schematic).
9.5.3
Monitor the resistivity
by selecting the proper resistivity channel on the RESISTIVITY MONITOR control
pad (Figure 1). Select proper channel by pressing CHAN
button (channel 1 for the QDR #1 on the left station, or channel #2 for the QDR
#2 on the right station). Make sure Mohm-cm light is on when selecting this
measurement mode. Water temperature or resistivity can be monitored on the same
LED display by selecting/deselecting one or the other display mode via DSPLY
button.
9.5.4
Make sure your
resistivity reading is 10 Mohm-cm or greater than 10 Mohm-cm at the end of your
dump rinse cycle before going into SRD. If not, repeat the rinse program.
9.5.5
Upon the completion of two
rinse cycles in the QDR, remove wafers from the bath, and place them in the
spin rinse dryer (SRD) station for the final rinse dry cycles. Make sure to
place the cassette with the H-bar facing in. Dump the QDR water by
pressing the HOLD button, then RESET button, as soon as the water is drained.
Leave the QDR with no water in it, and closed the lid, before leaving the
station.
9.5.6
Press start on the SRD
station. SRD will go through rinse and dry cycles. Final resistivity should be
greater than 12 Mohm-cm for the SRD during its rinse cycles.
9.6
Important Operational Notes
Metal
tweezers are NOT to be used at this sink! Use the vacuum wand with the black
cord to load dirty wafers. Use the vacuum wand with the red cord to unload
cleaned wafers from the black STA-PRO 1000 cassette. The spin/rinse dryer next
to Sink 6 can only be used with the cassettes from Sink 6- each sink has its
own set of cassettes! Transferring
cassettes from one sink to another introduces contaminants.
After wafers have been piranha cleaned, DI water
rinsed (QDR) and spun dry (SRD), inspect each wafer under the inspection light,
which is mounted on the wall at each sink. If any particles are found on the
wafers, post it as problem on FAULTS.
Extra cassettes and handles for Sink 6 are stored in a
blue bin labeled "extra cassettes for sink6" located on the worktable
in V1 (next to Sink 6). If a black STAT-PRO cassette and/or white handle
appears to be contaminated, please observe the following procedure:
9.6.1
Remove the contaminated piece from sink6 immediately;
transfer your wafers into a clean cassette from the worktable next to Sink 6.
9.6.2
Place the contaminated cassette into the blue bin on
the process island table in V1 labeled
"contaminated cassettes.
If the cassette and/or handle have been dropped on the floor,
label it as such. Contaminated cassette/handle will be removed from the VLSI
area for the next scheduled RCA 1 and 2 clean.
9.7
Transferring Properly Cleaned Wafers to Furnace Stations
9.7.1
Always use the blue boxes at the station with the MOS clean Teflon®
cassettes to transfer pre-furnace cleaned wafers to the furnace station. There
are one 4” and one 6” boxes available, labeled as Wafer Transfer Box to
Furnace.
9.7.2
Do not use these boxes and their cassettes for any other
application. These boxes are used for transferring clean wafers to the furnace,
and should immediately be returned back to sink6, once wafers are loaded into
the furnace.
10.0
Troubleshooting
Guidelines
10.1 Rinse cycle stopped in the middle QDR cycles: Press RESET/HOLD
buttons to dump the water out, then press RESET/START buttons to restart the
quick dump rinse cycles.
10.2 Cannot reach resistivity above 10 M Ohm-cm in QDR: Go through
another rinse program (2 cycles). If resistivity is still below specification
limit, then change the cassette and try the rinse cycle again (dirty cassettes
need to be RCA cleaned by staff). If it still cannot make the resistivity, then
there may be other issues involved. Stop and report it on FAULTS.
10.3 –LO-: Display indicates that the resistivity
reading is below the system minimum.
10.4
Err: Display
indicates that the sensor reading is erroneous. The sensor has exceeded a
reasonable value on the resistivity display or a malfunction in the sensor on
the temperature display.
10.5
Status
Indicators on Temperature Control Panel (Figure 3):
Red
LED will light up to indicate a problem:
HGH TEMP OVER
TEMP DEFFECTIVE SYSTEM
SENSOR FAULT
LOW TEMP LOW
LIQUID POWER HEAT
FAILURE
10.6 Sink
System Status Indicators (located on
top of the sink panel)
LOW PURGE Red indicator light will come on when there is low
air purge to cool off electronics for the sink.
PLENUM L/L Red indicator light will come on when the plenum
liquid level is too high.
ASPIRATOR Red indicator light will come on when aspirator is in use.
DRAIN Red indicator light will come on when acid is
draining.
PLENUM L/L HIGH: If it sounds, push the ALARM
SILENCE button on the sink, and notify the process staff and post the
problem on FAULTS as a full plenum lockout is an early warning alarm indicating
sink drain failure. The area under the deck of a wet process station (sink) is
known as the plenum. This area receives the water and chemicals when they drain
from the tanks and the utility sink. When the level of water in the plenum
reaches 3 inches, a float activated switch opens a valve and the waste is
removed. Should the water rise too high in the plenum because of a failure of
the system, all sources of water to the sink are shut off and the alarm will
sound. This is to prevent an overflow. If the user silences the alarm, it will
again sound when the problem is solved and the water level has returned to
normal.
10.7
If EPO is
pushed, follow instructions:
10.7.1
Pull out EPO button.
10.7.2
Open head case pull
down breaker switch and then lift up.
10.7.3
Push button on front of
sink that says on.
10.7.4
Push power button on
heater controller.
10.7.5
Push heat button on
controller.
Spin Rinse/Dryer HElp
Messages
|
HELP-0 Power
Failure
|
The
power failed while the unit was operating. Check the electrical lines in the
unit, and for a blown fuse. Press START to reset the microprocessor.
The rinser/dryer indexes the rotor and resets to the beginning of the
interrupted cycle. |
|
HELP-1 Bladder Pressure |
There
is inadequate nitrogen pressure to inflate the door seal. Check the door
bladder, the nitrogren pressure, and the pressure switch. Be sure there is
20-21 psi on RG2 and that the pressure switch turns off when the pressure
reaches 17-18 psi. |
|
HELP-2 Nitrogen Pres |
There
is insufficient pressure in the system nitrogen line. Check the nitrogen
pressure switch (PSW1). It should be set to approximately 13 psi. Check the
system line for leaks. Be sure that the pressure at RG1 is 23 psi dynamic. Check
the Clean Coil thermostat and reset if necessary. |
|
HELP-3 Door Open |
The
door is not completely closed. Check the door. If the door is properly
aligned, check the micro-swtich actuating arm. |
|
HELP-4 Index Failure |
The
unit is not able to index the rotor. Check the rotor positioner. |
|
HELP-5 Excessive Speed |
The
rotor speed has exceeded 3400 RPM. Retry the cycle a few minutes. If the
problem persists, there is a hardware problem. Call maintenance or VERTEQ for
assistance. |
11.0 Figures and Schematics
Figure 1
Figure 2
Figure 3
Figure 4
Piranha Bath
12.0 Appendices
12.1 Deck
Hose Instructions
The de-ionized (DI) water deck hose for the sinks is ALWAYS
available for emergencies; it provides a good safety backup in the event of
exposure to chemicals.
12.2
|
|
UFT-820
Temperature Controllers |
|
UFT-48-8
Dump Rinsers |
||||
|
SP1 |
10.00 |
|
C5 |
10:00 |
|
CY |
2 |
|
SS1 |
12.00 |
|
PA |
:20 |
|
rC |
0 |
|
Hi1 |
.00 |
|
P5 |
120.0ºC |
|
Fp |
99 |
|
Lo1 |
.00 |
|
Hi |
125.0 |
|
||