Chapter
3.6
1.0
Title
Iron Oxide Mask Processing
2.0
Purpose
Iron oxide masks are glass substrates coated with a thin iron oxide film and AZ1350J photoresist. They are developed and stripped in APT chrome developer machine, but manually etched.
3.0
Scope
This chapter covers the iron oxide mask making procedure, which includes: exposing the mask in the GCA Pattern Generator; developing the photoresist in the aptchrome; and manually etching the iron oxide film. Photoresist finally gets stripped from the mask in the aptchrome.
4.0
Applicable Documents
5.0
Definitions & Process
Terminology
N/A
6.0
Safety
Before you proceed with mask processing, please note the following: The door to the Aptchrome process chamber should be kept closed and latched at all times except when loading or unloading masks.
7.0
Statistical/Process Data
N/A
8.0
Available Process, Gases, Process
Notes
8.1
Iron oxide masks are easy to align because they are
transparent to visible light, though opaque to UV light and are also strong
enough to stand up to contact printing.
8.2
The Microlab stocks iron oxide masks in one size: 5”; plates are 0.090 mils thick. The
aptchrome mask developer will accommodate this size.
9.0
Equipment Operation
9.1
Enable the aptchrome on the WAND.
9.1.1
The system power to the aptchrome can be turned on by
flicking the blue power on rocker switch which is located on the
left side of the aptchrome. The program status will then be displayed on the
program recipe display screen on the front panel. The processing Programs 90 (develop) and 92 (strip
resist) for this operation are each separately activated by a red rocker
switch that will illuminate when selected. The STOP/RESET is a square red
button and the RECIPE START a square black button.
9.1.2
To operate the tool, the program recipe display screen will
prompt you to SELECT A PROGRAM AND PRESS START. Select a recipe by
pressing the desired rocker switch which will illuminate when selected. Next
press the START button. Once a recipe has been started, it will continue until
it finished and the program recipe display screen will read END OF PROGRAM.
While the recipe is running, the display on the screen will show how much time
has elapsed since the start of the recipe.
9.1.3
If the red STOP/RESET button is pressed, the tool
will immediately cancel the remainder of the recipe and stop whatever it is doing.
The program recipe display screen will show you that the recipe has been
stopped and will ask you to reset the system by pressing the STOP/RESET
button once more. The display will then once again prompt you to select a
recipe and press START.
9.1.4
Only one recipe may be run at a time: if more than one
recipe is selected and the START button is pressed, neither recipe will
run.
Important Note:
The STOP/REST button does exactly that: it stops the recipe at
once and does not automatically skip to the next step.
9.2
Checking Chemical Lines
Before starting your process, you will need to run a test
program (Program 99- test lines) to check that each
chemical is flowing properly at each step. The chemicals should dispense from
the nozzle(s) as a fan-shaped spray. The program is set up to allow each
required chemical to spray in sequence with water rinses in-between.
9.2.1
Select program number 99- test lines. The lamp is on at all
times during this program.
9.2.2
Press the START button.
9.2.3
When the program starts, make sure that the desired chemical
starts to spray out of its respective nozzle (30 seconds.)
9.2.4
Let the water rinse cycle run through (30 seconds.) The next
chemical should then begin to spray. Continue in this fashion until you have
worked your way through the program.
9.2.5
If too much water beads up on the door and prevents you from
being able to see through, briefly open the door and wipe it dry with a
techni-cloth. The techni-cloths are kept in a dispenser on top of the
aptchrome.
9.2.6
If everything checks out, you can begin processing your iron
oxide mask. If there is a problem, contact the Process Staff for help and
report the problem on the WAND using the FAULTS program.
9.3
Processing Iron Oxide Masks
9.3.1
Run the develop Program 90 without a
plate initially to make sure the lines are clear.
9.3.2
Load the mask, iron oxide side up, onto the spinner, seating
all four corners securely so that it does not fly off and break during the
spin.
9.3.3
Close and latch the door and select the desired program
number.
9.3.4
Press START.
9.3.4.1 Develop:
Program 90
Program 90, which is the initial
develop step, does not turn on the lamp during the entire process so that the
plate is not exposed. After a standard develop time the plate should be
inspected for complete development and the Leitz microscope in R2.
9.3.4.2 Manual
Etch
Iron oxide masks are manually etched. Use the deck at
sink12. A small rectangular white Teflon® dish labeled iron oxide
etch only can be found on the deck.
A white Teflon tweezers for holding the mask is clipped onto the large white Teflon
beaker which can also be found at this sink. This etch step should only be done
in this dish.
Use the Cyantek FE-12 Iron oxide etchant, which can be found in the APT Chemicals c-locker in R1. (Additional bottles are stocked in the blue developer cabinet in the lobby.). Etch time is approximately 75 seconds for dark field masks; clear field masks may take as much as 15 seconds longer.
Use the white Teflon tweezers to gently agitate the mask during this step. When the etch is complete, rinse the mask by using the deck hose at the sink then dry with the N2 gun which is mounted at the pattern generator chamber in R2. Inspect the etch at the Leitz microscope in R2.
If the etch is complete the etched area should look like a
white matte. If under etched, repeat the process.
Note: Use fresh etchant for each mask. When
finished, pour the used etchant into the large white Teflon beaker at the sink
in order to carry it over to sink4 in Y1 for disposal. The aspirator at sink4
is used for this step.
9.4
Photoresist Strip: Program 92
The remaining photoresist is exposed with the lamp on in the first step and then removed with
developer concentrate.
Program 92 is a strip only
process which removes the photoresist from the mask following the develop and
etch steps.
9.4.1
When the process is completed, check to see if the plate is
completely dry on both sides. If not, use the N2 static gun in R2 to blow it
dry.
9.4.2
Dispose of the iron oxide etchant at sink4 in Y1. Pour the
used etchant into the large white Teflon beaker at this sink which is kept for
this purpose. Carefully carry the beaker over to sink4 in Y1 and use the
aspirator to dispose of it then use the deck hose at this sink to rinse out the
beaker. Please return the beaker to sink12 afterwards. Reminder: do not pour
the etchant down the drain at sink12 in R1 as this sink is not a certified fume
hood. Use techni-cloths to wipe up any spills.
9.4.3
When you have completed your Iron Oxide mask processing, run
rinse program 93, then disable the APT chrome on the wand.
10.0
Troubleshooting Guidelines
If the program recipe display screen is blank, report on
FAULTS promptly as this indicates a blown fuse.
11.0
Figures & Schematics
|
Step |
Chemical |
Output |
Description |
Spin Speed (103 RPM) |
Time (sec.) |
|
1 |
Shipley Microposit Developer 452 |
Lamp on |
Developer Nozzle |
.00 |
30 |
|
2 |
Water Rinse |
Lamp on |
Top/Bottom Rinse |
.00 |
30 |
|
3 |
Concentrated Chromium Etchant CR-7 |
Lamp on |
Etchant Nozzle |
.00 |
30 |
|
4 |
Water Rinse |
Lamp on |
Top/Bottom Rinse |
.00 |
30 |
|
5 |
Shipley Microposit Developer 452 |
Lamp on |
Stripper Nozzle |
.00 |
30 |
|
6 |
Water Rinse |
Lamp on |
Top/Bottom Rinse |
.00 |
30 |
|
Step |
Chemical |
Output |
Description |
Spin Speed (103 RPM) |
Time (sec.) |
|
1 |
Water Rinse |
Lamp off |
Top/Bottom Rinse |
.22 |
10 |
|
2 |
Shipley Microposit Developer 452 |
Lamp off |
Developer Nozzle |
.22 |
75 |
|
3 |
Water Rinse |
Lamp off |
Top/Bottom Rinse |
.22 |
45 |
|
4 |
Spin Dry |
Lamp off |
(Spindry) |
.95 |
120 |
|
Step |
Chemical |
Output |
Description |
Spin Speed (103 RPM) |
Time (sec.) |
|
1 |
Spin |
Lamp on |
(Lamp on) |
.22 |
480 |
|
2 |
Water Rinse |
Lamp on |
Top/Bottom Rinse |
.22 |
10 |
|
3 |
Shipley Microposit Developer 452 |
Lamp on |
Stripper Nozzle |
.22 |
60 |
|
4 |
Water Rinse |
Lamp on |
Top/Bottom Rinse |
.22 |
45 |
|
5 |
Spin Dry |
Lamp on |
(Lamp on) |
.95 |
120 |
12.0
Appendix
N/A
Teflon® is a
trademark of Dupont.