Chapter 6.07
Edwards Auto 306 DC and RF Sputter Coater
(edwards)
1.0
Title
Auto 306 DC and RF Sputter Coater
2.0
Purpose
The Edwards system sputters metal and dielectric materials
3.0
Scope
Films are deposited by bombarding the target material with high-energy
ions from a plasma. The films deposited by this method
are uniform in thickness and capable of covering areas usually shadowed by
other deposition methods.
The Edwards
system consists of two parts:
►
Deposition chamber,
vacuum system and control panel
►
DC and RF power
supplies and MFC control panel
Inside the
deposition chamber are two magnetron guns (DC on right, RF on left, a substrate
holder (6-inch standard, with 4-inch adapter plates), a thermocouple and a
substrate heater. Maximum temperature for the substrate heater
is 250ºC. Do not exceed this value. The control panel controls the vacuum, the rotation of the
substrate holder and heating of the substrate.
One mechanical pump is installed for rough pumping and one turbo
pump for fine pumping. A crystal monitor
is installed in the system but not currently configured for use.
A DC and RF power supply provides the power needed to generate
plasma in the deposition chamber.
4.0
Applicable
Documents
Description of a basic vacuum
system:
http://microlab.berkeley.edu/text/labmanual/chap6/vacuum.pdf
Vendor manuals: Edwards Auto 306 DC and RF Sputter
Coater. Auto 306 Accessories:
Vendor materials on web: http://www.bocedwards.com/pdf/planar.pdf,
http://www.bocedwards.com/pdf/CoatingSystems_Components.pdf,
http://www.bocedwards.com/pdf/auto306em.pdf
5.0
Definitions &
Process Terminology
5.1
Deposition Chamber:
Contains DC and RF magnetrons, wafer holder, crystal monitor (not installed
yet) and heat lamp. The door has a magnetic bearing and users should gently
close the door without adding forces on it to assure good seal of the chamber.
5.2
Control Panel:
Allows you to vent and pump the chamber.
5.3
DC Power Supply:
Middle of the equipment rack to left of deposition chamber. OFF unless process
interlock on.
5.4
RF Power Supply: Bottom
of the equipment rack to left of deposition chamber. OFF unless process
interlock on.
5.5
Workholder
Control: Controls the rotation of the wafers.
5.6
Crystal Monitor
(not yet configured): Monitors the evaporation rate by correlating deposited metal
thickness to the amount of deviation from its original crystal resonant
frequency.
5.7
Sputtering Materials:
Targets available from Microlab: Ag, Al, Co, Cr, Cu, In, ITO (90/10%), Ni, Pd,
SiO2, Ti, W. Members may supply their own targets for use in this system after
getting permission by e-mailing edwards at silicon.eecs.berkeley.edu
and requesting a new sputter material. Gold, palladium, platinum and other
precious metal targets will no longer be stocked by the Microlab after the
current inventory is exhausted.
5.8 Target: Diameter: 7.5 cm. Standard thickness: 6 mm. Can order from Super Conductor Materials,
Inc. Dielectric materials and poor thermal conductors should be ordered indium-bonded
to a 1/16” (~1.5 mm) copper backing plate.
6.0
Safety
6.1
Read all relevant instructions
before you operate any accessories.
6.2
Surfaces within the AUTO 306 may
hot. Do not touch surfaces without cooling first.
6.3
Intense light will be emitted from
the plasma.
6.4
Observe all safety precautions
when you come into contact with dangerous substances which have been used with
the evaporation materials.
6.5
Wear clean lint-free gloves when
you handle components in the chamber to prevent contamination of the evaporation
materials and its accessories.
6.6
Do not add extra forces when you
close the chamber door. It will damage the magnetic bearing.
6.7
Metal dust is a hazard. Never use compressed gas to clean the
chamber. A house vacuum drop is available
to the right of the chamber.
7.0
Statistical/Process
Data
The
following recipes (parameter settings/dep rates)
provided by Hellman group (Physics) can be used to sputter different films in the
Edwards machine (see Tables below (data dated 10/17/06). Please note, all these
recipes use power settings below the cut off limit (350W <), defined
by staff for this tool.
7.1
Standard Processes
|
Material |
Magnetron Gun Type |
Power (W) |
Pressure (MTorr) |
Rate (A/min) |
|
Cr |
RF |
100 |
6.5 |
38 |
|
Ti |
RF |
100 |
5 |
20 |
|
Al |
DC |
300 |
5 |
182 |
|
Cu |
DC |
300 |
5 |
248 |
|
Au |
DC |
200 |
5.5 |
277 |
|
Pt |
DC |
300 |
5 |
198 |
7.2
Low Film Stress Processes
|
Material |
Magnetron Gun Type |
Power W) |
Pressure (MTorr) |
Rate (A/min) |
Film Stress |
|
Pt |
DC |
300 |
8 |
200 |
16.5 MPa, tensile |
|
Cu |
DC |
100 |
2 |
106 |
218 MPa, compressive |
|
Cr |
DC |
300 |
0.4 |
189 |
53.4 MPa,tensile |
8.0
Available
Process, Gases, Process Notes
Pumping Speed: < 10 min. to reach process pressure.
Available Targets: Al, Cr, Cu, ITO, Ni, SiO2,
Ti, W, Ag, Pd, Co
Precious metal
targets, such as gold and platinum are not stored by the edwards.
Precious metal targets are available for checkout from the Microlab office.
Maximum power for the Edwards for any bonded target is 350W.
Note: For the Edwards 3” magnetron guns this power
setting corresponds to a power density of ~50 W/in2. Power density greater than 50 W/in2
results in excessive heating of the target. If the target becomes too hot, it
may crack due to thermal stress or it may delaminate due to softening of the
solder material used to bond the target to its backing plate.
Labmembers are cautioned against comparing the RF or
DC power setting of a specific tool in the MIcrolab
to the power setting published in some reference for some other tool. Most
references do not provide any critical tool geometry information (target size
and distance from source). Power density - not the absolute setting of the
power supply - is the significant variable for determining deposition rate. For
example, on the Randex (another general use sputter
tool in the Microlab) the target size is 5” diameter, and the maximum allowable
power is 1000 W – which also corresponds to a target power density of ~50 W/in2.
Note: Lab members can use process conditions noted in
section 7.0, as a good starting point for their own process.
9.0
Operating
Procedure
9.1
Enable edwards
on WAND.
9.2
Check that the cooling system and
cabinet interlock are on. Report fault
if not. The vacuum interlock should also
be on if the system was properly left in standby mode and pumped down by the
previous user.
9.3
Vent the chamber (press seal and then vent). The vacuum
interlock will turn off shortly after the system output reads atmospheric
pressure. It will take a little longer
for the chamber to be able to be opened.
9.4
Place targets in the RF (front
left) or DC (back right) magnetrons.
Note: DO NOT TOUCH THE TARGET WHEN IT IS HOT, IMMEDIATELY AFTER PROCESSING
WAFER/S. THIS CAN RESULT IN INJURY AND/OR TARGET CONTAMINATION (SURGICAL GLOVES
CAN EASILY MELT ONTO THE TARGET SURFACE).
9.4.1
Open the shutter for the
appropriate magnetron. A manual lever on
the left hand side of the chamber operates the RF shutter and the control unit
to the right of the chamber operates the DC shutter (SS1 button).
9.4.2
Lift off the target shield
cylinder surrounding the magnetron. Care
should be taken to not hit the inside of the chamber as this is being
done. The workholder
may need to be rotated to remove the cylinder from the chamber.
9.4.3
Unscrew the copper ring on top of
the target and place the target in the center of the top surface. Use caution when placing magnetic targets
onto the sputter gun. There are strong
magnets in the gun that will attract the target and this is a pinch
hazard. Place the copper ring back in
place and screw it down in a diagonal/star pattern - a metric Allen wrench is
provided and should stay with the machine at all times.
9.4.4
A pad is also provided to clean
off any surfaces that have materials from previous runs flaking off. This should also remain with the machine at
all times. Inspect the target clamp and shield
for excessive material build up. Report
a fault if either needs a thorough cleaning.
9.4.5
Place the cylinder back around the
magnetron. If you have the standard
target thickness of 6mm, the smallest slot should be used for the RF target
shield and the middle slot should be used for the DC target shield. A standard 6 mm thick target will have 5 mm
spacing for the shield for RF sputtering and will have 3 mm spacing for DC
sputtering. If your target is a
different thickness consult the Edwards Auto 306 DC and RF Sputter Coater manual in the
Microlab office. Magnetic materials need
to be much thinner (1-2 mm) and should use a Cu backing plate to obtain the
overall desired thickness.
9.4.6
Close the shutters once the target
is in place. If a target is not being used, the cover should remain over the
shield.
9.6
If the small cylinder vacuum cap
in the front right of the chamber has popped off, replace it in the correct
position.
9.7
Close the chamber door and press CYCLE to evacuate the chamber. Pressing cycle
evacuates the chamber without enabling the process interlock.
9.8
When the vacuum is sufficient to
begin the sputter process, the PROCESS button will light up on the vacuum
control panel. Press PROCESS to begin
the sputter process. Once the process
interlock is enabled, the gas flow controller and the DC and RF power supplies
are enabled. Start flow of the Ar/N/O2
gases depending on process parameters.
9.9
Mass Flow Controller (MFC)
9.9.1
Enable Gas 1 (AR) or Gas 2 (O2) by
toggling the pneumatic toggle switches
just above the Brooks Controller. The Left toggle switch is for Argon and the Right toggle switch is for Oxygen/Nitrogen. This opens the pneumatic valves only. Either Nitrogen or Oxygen may be selected
by turning the valve below the vacuum control panel.\
9.9.2
Set MFC flow at front panel of the Brooks
controller. Press the “Channel Selection” Key until you see “>” symbol after 1 or 2, i.e. “1>”
= Gas 1 is Active channel.
9.9.3
Set the desired flow by pressing
the “Up” or “Down” arrow keys to your desired flow
setting. The double up arrows increments by 1’s and the single up arrow button
increments by .05.
9.9.4
Press “Enter” (the set-point will not be entered until you press
enter).
9.9.5
The controller display will automatically
cycle back to flow reading within a few seconds. You should see gas flow at this time. You must be in “Process” mode on the Edwards
for gas flow.
Note: PLEASE DO NOT ADJUST ANY OTHER VALUES OTHER
THAN GAS SETPOINTS ON THE BROOKS CONTROLLER.
9.10
Adjust settings for appropriate
power supply. Please see applicable
documents in Section 4.0 if process parameters are not
already known for your material or consult superuser/Microlab
staff. Process data will be supplied in
this document once materials have been evaluated.
9.11
DC Sputtering – AE MDX-1.5K
9.11.1 Press setpoint and adjust
the set point using the level knob.
9.11.2 Press actual until watts
are shown. Do not exceed 350 Watts for unbacked metal
targets. Targets attached to a backing plate should be limited to 300 Watts or
less.
9.11.3 Do not adjust RAMP – the knob should be locked.
9.11.4
Turn on the power supply and look
for plasma – color will depend on material being sputtered.
9.12
RF Sputtering – AE RFX-600
9.12.1 Hold down SETPOINT while adjusting the LEVEL knob to set the sputter
power. Do not exceed 350 Watts for metal
targets. Dielectric targets and targets attached to a backing plate should be
limited to 300 Watts or less. Use caution with power settings for thermally
sensitive materials.
9.12.2 Make sure that the auto-tuner is set to AUTO.
9.12.3 Turn on the power supply and look for plasma – color will depend on
material being sputtered.
9.12.4 Tips for igniting the RF plasma
9.12.4.1 Set the Ar pressure to ~20 mTorr and turn on the power supply. When the plasma ignites the Ar pressure can reduced to the desired pressure.
9.12.4.2 Start with a metal target in the DC gun and ignite the plasma. (The shutter does not need to be
opened.) Turn on the RF power
supply. The DC power supply may be
turned off once the RF plasma has ignited.
9.13 Start rotating the wafers. Open
shutter and start deposition time.
9.14 Once done sputtering, close the shutter, turn off power supply, and
then stop the wafer rotation. Set the MFC
to zero flow and press CYCLE to evacuate the process gas from the chamber. If the process interlock turns off while
sputtering, you will need to extend the time delay for the interlock. See the troubleshooting Section
10.1 for more information.
9.15 Press SEAL and then VENT if the process interlock is still
enabled. If the time delay set point has
passed and the process interlock is disabled and only VENT needs to be
pressed. Make sure that the chamber has
sufficient time to cool down before venting.
9.16 Wait for the chamber to come up to atmospheric pressure and remove
wafers from the holder. System may be
hot inside deposition chamber if sputtering times were long.
9.17 Repeat from 9.5
if additional wafers need to be processed.
Otherwise proceed to 9.18.
9.19 Once all wafers and targets have been removed, close the chamber door
and evacuate the system by pressing CYCLE.
9.20
Once the system is pumped down,
disable the equipment on wand and provide the following information in the
comment section: material sputtered, gas type and flow rates, DC or RF power,
and deposition time (for desired thickness if known). If a previous user had left a target in the
system, please make a note.
10.0 Troubleshooting Guidelines
10.1 Process interlock shuts off.
If the time delay set point is too short and the process interlock disables
before you are done sputtering, you can adjust the time by going into the set
point-relay menu.
10.1.1 Press NO for main menu, scroll to set point-relay and press YES.
10.1.2 Scroll to time delays and press YES.
10.1.3 Scroll to time delay 7 (if not already there).
10.1.4 To adjust time, press yes and a blinking B should be seen. Using arrow keys, set the first digit of the desired
time and press yes. Set the second digit
and press YES or press YES again (while B is still blinking) to go the
minute/second display. Set to minutes
(M) or seconds (S) and press YES to set new time.
10.1.5 Once the new time is set, press NO to exit menus until you reach the
main menu. Select Process Sequence and
press YES to go back to the normal screen.
10.2 Gases are not flowing. If all the appropriate switches are open and
no gas is flowing check to make sure edwards is
enabled.
10.3
VOLTS ERR is displayed on the
vacuum control panel. This error is displayed when the high vacuum
(Penning) gauge has a flake in it. The
vacuum controller will not let you enter the process mode if this condition
exists. File a fault on the wand to have
the gauge cleaned by the process staff.
11.0 Figures & Schematics
Figure 1 - DC and RF Sputter Coater
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9