Chapter 6.03
Randex Sputtering System
(randex)
1.0
Title
Randex Sputtering System
2.0
Purpose
The Randex system sputters metal and
dielectric materials.
3.0
Scope
The deposition source is generated by bombarding the target
material with high-energy ions from plasma. The film deposited by this method
is uniform in thickness and capable of covering areas usually shadowed by other
deposition methods.
The Randex system consists of three parts:
► The deposition
chamber and control panel
► The vacuum system
►
The ENI OEM 12A RF power supply
Inside the deposition
chamber are three targets, a substrate table, and an etch station circulating
system. The control panel selects the target and substrate position and
controls the sputtering power. The vacuum system contains a mechanical pump, a
cryopump, throttle valve, automatic
valve controls and
chamber. An ENI OEM 12A RF power supply provides the RF power needed to
generate plasma in the deposition chamber.
4.0
Applicable Document
Ion Implantation, Sputtering
and Their Applications by Townsend,
Kelly and Hartley, Academic Press (1976).
5.0
Definitions and Process Terminology
6.0
Safety
6.1
Substrates made of materials with high vapor pressure or with a mobile ion content should
not be used in the Randex. Putting photoresist in the Randex should
be avoided if at all possible.
Consult the Microlab Process Engineering Manager if you have unusual substrate
material.
6.2
Use new gloves when you work within the chamber, or when handling parts entering the chamber.
6.3
The cryo temperature readout
should read less
than 20K.
6.4
The high vacuum valve should be OPEN in standby mode.
6.5
Gas pressure feeds should be kept between 20 and 25 psi. Gas
cylinders should not be turned off.
6.6
If you need a gas cylinder changed, create a FAULT report.
6.7
Sputtering power should
never exceed 1000
Watts. Reflected power should never exceed 100 Watts or 10% of the
forward power.
6.8
The ion gauge filament and the ion gauge power should be off when sputtering. The ion gauge filament should be turned
off when beginning pump down. It can
be turned on after the high vacuum valve has opened.
7.0
Statistical/Process Data
8.0
Available Process, Gases, Process Notes
8.1
Available recipes for some of the targets (Table
1):
Refer to Table1 in Appendix 1 for process parameter set up and the
estimated deposition rate for various targets. Lift off process is note in
Appendix2.
8.2 Target Inventory
Ag
Al
Al2O3
Bismuth Titanate
Cr
Cu
Flint Glass
Ge
InSb
ITO
Lead Glass
LiF
MgF
MgO
Neodymium Oxide (Nd2O3-SiO2)
Niobium (Nb)
Nickel (Ni)
Iron (Fe)
Palladium (Pd)
Si
Si3N4
SiO2
Sn
SnO2
Ta
Tantalum Oxide
Ti
TiW
W
WSiX
Yittrium
Alumunous Neodymium (YO3-Al2O3-Nd2O3)
ZnO
Zr
7059 Glass
9.0
Equipment Operation
Note: A large inventory of
targets exists for the
Randex. Should you require a target changed, please observe the
following target change policy.
9.1
Target Changes
9.1.1
Target changes are made by staff and labmembers who have been
trained for target changes. Labmembers qualified for the randex are not allowed
to do target changes.
9.1.2
Current targets in the randex are listed on the WAND in equipment
comments.
9.1.3
To request a target
change, send email to randex@eecs.berkeley.edu, stating what target(s) you
would like and when you need them. Staff will add your requested targets
to the target change queue in the order they were received and do whatever is
possible to meet your schedule. Staff will enter the target change
schedule into equipment comments and send a copy to labmembers qualified to use
randex. The latestschedule can be accessed on the wand at any time.
9.1.4
Announced target
changes will not take place if the labmember(s) who requested the target(s) has
no reservations for the period which the target(s) is scheduled to be
installed. Anyone wanting to purchase a new target should contact Bob
Hamilton (bob@eecs).
9.1.5
Targets will stay in
place for a week at a time unless users indicate that they are done sooner and
others are waiting. If there is no request, targets will not be changed.
9.1.6
Anyone wanting to
purchase a new target should contact Bob Hamilton (bob@eecs).
9.1.7
Staff may ask labmembers for assistance with periodic
cleaning of the randex. Noncompliance
will result in loss of qualification to use the randex.
9.2
Loading a Sample – Pumpdown
9.2.1
Users of the randex must supply their own aluminum or copper disc
to cover the substrate table, or wrap the substrate with oil free aluminum foil
available in the dispenser on the orange clean workstation. The disc should be
6 inches in diameter, and ~1/8 inch thick.
9.2.2
Check to see if the system has been reserved. If not, enable it
through the Wand.
9.2.3
Check the cryo pump readout to confirm that the temperature is
less than 18K. If not, STOP, and report this problem using FAULTS on the
Wand.
9.2.4
Turn on the ion gauge power and filament and confirm that the pressure
is less than 1x10-6 Torr. If not, STOP, and report this
problem on FAULTS.
9.2.5
Push the VACUUM button to terminate pump cycle. This will
close the high vacuum valve.
9.2.6
Vent the chamber by pushing the VENT button. (The system
has a 10 second time delay relay to assure the gate valve has closed.) Vent
until an N breeze can be felt around the baseplate. Turn off the 2 VENT.
9.2.7
Put on clean polyethylene gloves and raise the top plate. Be
prepared to catch the O-ring if it sticks to the top plate.
9.2.8
Change gloves. Load the substrate plate and sample.
9.2.9
Make sure the o-ring sits properly in the groove of the bell jar.
Then lower the top plate.
9.2.10
Before starting pumpdown, confirm that the ion gauge is off.
9.2.11
Push the VACUUM button. The roughing valve should open and
the chamber should pump down. When the pres- sure falls to ~500 microns, the
roughing valve should close and the high vacuum valve should open. If the
crossover does not occur, push the VACUUM button to close the roughing
valve, and report a problem on FAULTS. Make sure the throttle valve is not
engaged during pump down. After the hi-vac valve opens, turn on ion gauge
filament.
9.2.12
When the system achieves a pressure in the mid 10-7 range, turn on
the cooling water (both knobs to the left) and the power supply (see Section
9.3).
9.2.13
Turn off the ion gauge filament, close the throttle valve, and set
the flow rates of the gases you'll be using to the desired values. Note:
Check that the gas bottles are open (They are not supposed to be closed, but it
has been known to happen.). Check the outlet pressure at the tank - it should
be about 20 psi for optimal mass flow controller performance. The mass flow
controller is mounted on the lower right of the Randex. Push toggle up to POWER
to turn on. Push toggle down to SET to set desired flow. Set to READ
to read flow. Position 1 is Ar, position 2 is O : Ar [1:1], and position 3 is
N. (Note: There are only two mass flow controllers - the second is used
for both nitrogen and oxygen.) Gas will not flow until the appropriate toggle
switch on the left panel is on. Typical sputtering pressures are 5 - 8 mTorr.
9.3
Operating Instructions for ENI OEM 12A RF Generator
9.3.1 Power Up Procedure
9.3.1.1
Turn on the ENI OEM 12A generator.
9.3.2
Operation
9.3.2.1
Increase the power setting on the ENI generator to 100 watts
reflected. No forward power with flow until the plasma is ignited.
9.3.2.2
Push IGNITE button to ignite the plasma on your target -
this is essential for proper tuning. It is easier to ignite the plasma at
higher pressures, i.e. at 10 - 20 mTorr, and then reduce the pressure for
processing.
9.3.2.3
Tune target load for maximum forward power and minimum reflected
power using load and tune knobs.
9.3.2.4
Adjust output level for desired power. Read watts on forward power meter. Reflected power should not exceed 10% of forward power.
9.4 Sputtering
Do not apply more than 300 watts of power to a dielectric target
because the poor thermal conductivity of dielectrics heat is not effectively
transferred to the coolant and the target may crack.
9.4.1 To
sputter clean a target, place the system in the following position:
Mode: Sputter Deposit
Target Selector: Your choice
Table Position: 180º rotation away from your target
Introduce about 50 Watts of RF power using POWER ADJUST. Reflected
power should never exceed 100 Watts. If plasma is not formed, adjust tune and
load so that reflected power is at a minimum. Ignite by pushing the button on
the power adjust knob.
9.4.2 After
plasma is clearly visible, retune the system to minimize the reflected
power. The TUNE knob has a greater
effect on reflected power than the LOAD knob.
Slowly adjust the TUNE knob first, and then use the LOAD knob to
minimize reflected power. Adjust the
power to the desired forward rate and sputter clean for the desired time.
9.4.3
Sputter clean substrate, using sputter bias mode, if so desired.
9.4.4
After Sputter clean, turn the table position to your target and
begin deposition. Check frequently and
minimize the reflected power for the first 20 minutes.
9.4.5
After desired sputtering time, turn the power to adjust to zero.
9.4.6
Cool down the system (~5 to 10 minutes depending on sputtering
power used); turn power off on the Henry power supply. Turn off gas toggle
valves. The mfc controller should be
left on. DO NOT SHUT OFF THE GASES
AT THE TANKS.
9.4.7
Place the throttling valve to the open position, and close the
hi-vac valve. Wait 10 seconds. Press
the vent button until the chamber is at atmosphere, unloading sample and substrate plate with fresh
gloves.
9.4.8
Turn off the cooling water.
9.4.9
Place the radix in the standby mode by:
9.4.9.1
Pump down system. Turn off
AC breaker to RF supply.
9.4.9.2
Check HV valve (ON), Roughing valve (OFF), Gas valves (OFF),
Throttling valve (open), and pressure
in chamber is less than 5 x 10-6. You may leave the ion gauge power
and filament on.
9.4.9.3
Sign out. Enter a comment
in the log at that time describing your run. Since the Randex is a
general-purpose system, this will allow subsequent users to be aware of
potential contaminants to their process.
9.5
Cryo Pump
Regeneration Procedure
1. Press the Regen button on the CTI controller.
2.
Press the 1
button to start the regeneration process.
3.
Press the 2 or 3
button to confirm.
10.0
Troubleshooting Guidelines
The randex has a
sputter-etch capability. For some members, this can be very important for
obtaining a clean interface and good adhesion.
Use of aluminum foil in
the randex -- especially wrapping foil directly on the chuck -- can short out
the RF or drop particles of foil into the chuck, causing intermittent shorts
later on. This can prevent ignition of the RF or damage the RF generator.
Members should also be
aware that the randex has a water cooled chuck. This can only be effective if
the wafer has good thermal contact to the chuck. To provide a smooth, flat
surface while protecting the chuck from deposition, copper plates are provided.
Using aluminum foil on the copper plates will degrade the thermal contact
dramatically and essentially defeats their purpose. The copper plates need to
be periodically etched or lapped to maintain a smooth surface. If the copper
plates need cleaning, report a problem for the randex. If you choose to scour
the plates yourself with an abrasive aluminum oxide pad such as scotchbrite,
keep the sample wet or under running water to avoid generating potentially
harmful metal dust. Rinse with DI, dry and then wipe with isopropanol while
handling with clean gloves.
11.0 Figures & Schematics
12.0 Appendices
12.1 Process Recipes (parameter set up)
Target |
Ar(sccm) |
Ar /O2*(sccm) |
P(mTorr) |
RF Power (W) |
Rate(Ǻ/min) |
|
Si |
72 |
|
40 |
100 |
128 |
|
Ti |
72 |
|
40 |
100 |
106 |
|
W |
72 |
|
40 |
100 |
130 |
|
SiO2 |
|
44 |
40 |
100 |
24 |
|
Al2O3 |
|
44 |
40 |
100 |
23 |
|
Al |
72 |
|
40 |
150 |
164 |
|
Ru |
42 |
|
30 |
300 |
177 |
|
TiW |
42 |
|
30 |
300 |
330 |
|
Cu |
42 |
|
30 |
300 |
320 |
|
Nb |
100 |
|
50 |
400 |
315 |
|
Pt |
72 |
|
40 |
200 |
300 |
|
Pt |
100-110 |
|
40-50 |
200 |
400 |
|
Cr |
72 |
|
40 |
200 |
175 |
|
Ti |
75 |
|
40 |
300 |
106 |
|
Ti |
100-110 |
|
40-50 |
100 |
200 |
|
Ni |
70 |
|
40-50 |
100 |
150 |
*90%Ar + 10%O2
Table 1 - Process
Parameters for Various Targets and Their Estimated Deposition Rates
12.2