Tylan LPCVD Furnace Module
The Tylan LPCVD furnaces are used to deposit films of nitride, undoped poly, undoped LTO and phosphorous doped LTO. Wafers processed in the LPCVD furnaces are cleaned prior to processing at the Lab's highest cleanliness level.
Please review the Materials allowed list before using the Tylan and LPCVD furnaces:
- Tylanpoly, Tylannitride: No metals allowed
- Tylanbpsg: The front or load end of the boat - No metals allowed!
The back or source end of the boat - Al, Ti and W ONLY.
Substrates allowed: Si, SiGe, quartz, and SOI. No glass or plastic wafers All wafers must be clean and free of fast diffusers (metals, sodium, KOH, etc) and materials which could contaminate the system. Wafers must be fully inspected for photoresist removal following any lithography process prior to cleaning.
NONMETAL: Wafers that have never had metal on them must get the standard pre diffusion clean at the wbdiff prior to the nonmetal LPCVD tubes (tylanpoly, tylannitride, or nonmetal side to tylanbpsg tube). 50:1 HF NOTE: Wafers going to LPCVD should get the 50:1 HF dip last instead of between the sulfuric and the HCl steps. This prevents hazy depositions.
STD METAL: Wafers going to the METAL SIDE of the LTO BOAT. These wafers should be cleaned at the wbmetal (NOTE: only standard metals allowed - Al, Ti or W). If they had the metal stripped or turned to silicide the clean could be done at wbsilicide (see cleaning procedures for these benches).
Substrates must have gone through the clean within one hour of loading them into the furnace.
NOTE: Add cleaned Test Wafers. Bare silicon for LTO and for nitride, 1000A oxide on silicon for poly runs.
These systems are high use tools, so please try to remove any reservations you will not need.
With LPCVD furnaces, since a pre-diffusion clean is mandatory, one can easily see if a lab member is going to be using their reservation. You may use the reservation if the person signed up is not at least cleaning wafers 15 minutes into the reservation time. Also, if a furnace is not reserved, go ahead and reserve it for your use.
Please do not leave the furnace open for more than 15 minutes. This is to avoid wear and tear on the heating elements and warpage to the tube. You will need to know the exact total time of your program. The only exception to this rule is LTO when the dummies must be stripped.
Enable the furnace
You must be on the qualified users list to enable any equipment. Check the furnace status on coral; is there a problem message? Is it on shutdown? Is it enabled by another lab member? Check out any problems which may have been reported. Do not use a furnace which has been shutdown.
LPCVD Check Pump Program
The LPCVD systems are all left with the pump programs running. Check the status of the tube before you start your clean. Go to the furnace and using the STATUS button verify that the system is in RUN mode with the pump program in step 25. If you find it in READY mode, one of two things went wrong -- it failed the pump program or someone forgot to run the pump program. Since there is no way to check this, you should run the pump program. Push RUN to see if it will pump down and hold at step 25 -- before you attempt to use the system.
LPCVD Ending Pump Programs
At least 10 minutes before you finish your wafer clean you should end the pump program by pushing ALARM ACK twice on the ROP (the one on the right side of the panel, the other one is for furnace temperature controller problems).
VERIFY THE TUBE IS VENTED
IMPORTANT NOTE * LPCVD - WARNING!! If you run a program before the tube is vented it will pull the tube (breaking it).
Ten minutes after the pump program has ended you must manually test that the tube is vented. Push MANUAL on the boat puller, push FAST, then LOOK AT THE TUBE while you hold down OUT. You should see immediate response (i.e. the boat starts to come out), if not stop and wait for 10 more minutes and test it again.
After you have manually verified that the tube is vented you may load your program.
Check Film Deposition Rates
Check the LPCVD log book for the most recent deposition rates for the program you plan to use. Check for the most recent dates the program you were interested in was run. Note the tube and dummy thickness last recorded (when you disable you will add your thickness to those numbers and log them). This keeps a running log as to how much buildup is on the tube and dummies so that maintenance knows when it is time to clean the tube.
Note: It is important to measure your deposition and RECORD the results when you disable the equipment. This information is used by others to determine deposition times.
Review your program
Select the disk (brown labels are the most recent versions) where your
program is located (i.e. Poly, Nitride, LTO and type DI DI <RET>
to see what recipes are on the disk, look at a recipe’s steps (DI RE recipe
Make a list of each step and the time you will be in each step (it would be good to keep this in your cleanroom notebook so that you can refer to it every time you use the recipe).
Read and make sure you understand what is taking place during each step of the recipe.
Load your program
Load the desired program with the TYCOM keyboard by typing "LO <filename> <furnace#>" <RET>. You will be asked to enter any variables the program requires.
TIME: VARIABLE - when there is a variable time you must enter it in the format -- 00:00:00 (hours:minutes:seconds). Be sure to look at it carefully when you enter the time as you will not see it again until you are in that step in the process. If you are not sure you entered it correctly -- enter it again. Verify program was loaded by checking that "good load" appears on the screen.
Check furnace status:
Check the desired tube status with the TYCOM keyboard by typing "DI ST
NOTE: Across the top of the screen you see the following:
- TUBE - the # of the tube you are monitoring.
- STATUS - the mode (i.e. READY, RUN or HOLD)
- READY - you may load a program
- RUN - a program is already running, you may not load a program.
- HOLD - a program is running and is being held at the indicated step.
- PROCID - the name of the program that is loaded
- ET - the elapsed time since run was pushed
- STEP - the current step number
- TIME-TO-GO - the time to go in the current step
- STEP ET - the elapsed time in the current step
INPUTS - this is what you actually have (temperatures, gas flows, etc.) IMPORTANT: If there is a small b to the right of one of the temperatures, it means the backup thermal couple is broken. Write it up as a problem. It is OK to use the tube.
If there is a capital B to the right of one of the temperatures, it means the main thermacouple is broken. Write it up a shutdown. You may not use the tube.
If there is a question mark ? to the right of any of the temperatures, it means that the last time it checked that was the temperature, but the power has gone out and it has no idea what the temperature is (it is most likely room temperature). Write it up as a shutdown and do not use the tube.
If you see a suspicious temperature (ie 400C for all three zones or 250C for all 3 zones) when you want 800C or 300C. And if there is no TCU% (this shows if the zone is pulling power), it may mean that the tube is cold. You should also see a message below the temperature of the 3 zones such as "TCU error 80.." Write it up as a shutdown. It means the power went out and the temperature readings went down as low as they can (oxidations bottom out at 400C and LPCVD's bottom out at 250C).
If you see an MFC alarm message under the spot where the temperature of the 3 zones is listed, check the furnace. There may be an alarm going off because the gas tried to come on and overshot what it should have been. The gas will try to come on again if you push ALARM ACK. Write it up as a problem. If it keeps alarming (and the flow when you check furnace status is reading 0) write it up as a shutdown. It may be out of gas or the mass flow controller is not working.
If the other alarm on the panel in front of the
tube is alarming (light is on for SCR or OT), write it up as a shutdown
because the temperature controller is not working (either it overtemped or the
controller is not controlling). This alarm is located to the right of the boat
Start your program
Check that the tube is vented. See IMPORTANT NOTE above for details.
If your wafers are ready to load and your furnace status looks good, you can start your program. Push RUN. The boat will come.
Load your wafers: When the boat is out, load your wafers facing the front of the tube (except LTO is loaded back to back). The major wafer flat should not loaded toward either side bar of the boat (the wafer will not stand up straight if the major flat is on either bar). When loading is complete push ALARM ACK (see program step 5) and the boat will be loaded back into the tube.
Monitor your furnace
You must monitor BASE PRESSURE, LEAK PRESSURE and PROCESS PRESSURE. This is done by repeatedly checking the furnace status during the steps to be monitored (base is -- how low did it go during the pump and gross leak step; leak is-- how high did it go during the leak check step; process is-- what is the pressure during the deposition step).
CAUTION: NEVER push ABORT on an LPCVD tube (unless you KNOW that it is safe to do it). If abort is pushed while gases are flowing they will be trapped in the tube (gate valve closes) and the tube would then vent and the gases will be released into the lab from the front of the tube!
LPCVD BURN BOX IMPORTANT NOTES
If you hear an alarm that sounds just like a furnace alarm but you can not locate a problem at the furnaces AND when you open the door to the area behind the furnaces it gets louder, the burn box has failed. It is located on the far wall behind the LPCVD furnaces. Verify that it is alarming (put your hand over each of the two alarms and check for change in sound level, also you should see some red lights (normally green lights).
If maintenance personel are here, let them know immediately.
Check to see if your run is in deposition step.
If it is not yet at deposition (NO TOXIC GASES ARE FLOWING). You can SAFELY push ABORT. Wait 20 minutes for the tube to vent before you attempt to bring the boat out to remove your wafers.
If it is after your deposition is over. Let the run continue.
If it is during deposition (TOXIC GASES ARE FLOWING), go to TYCOM keyboard load the correct disk into the TYCOM and get ready to load the pump program for . When you are ready to load it.... go to the tube and push ABORT. Immediately load the PUMP program and push RUN so that it will pump down.
Doing this stops the toxics from being vented into the exhaust and prevents them from being vented into the lab. THIS IS VERY IMPORTANT. MAKE SURE YOU UNDERSTAND THIS BEFORE YOU ARE QUALIFIED TO USE THE EQUIPMENT!
Then write up the burnbox (the name is written on the front of the burnbox) as a SHUTDOWN. This will prevent someone else from enabling and running any equipment that requires the burnbox.
BE AT THE FURNACE WHEN BOAT COMES OUT!! It should not sit out more than 15 minutes (tube could be damaged). The only exception to this rule is LTO when the dummies must be stripped.
NOTE: For tylanbpsg tube you must check the dummy accumulated thickness. If is over 3u after your deposition you MUST strip them and put in fresh dummies. The wafers in the front two boats are loaded into a wbdiff cassette and stripped in the wbdiff 6:1 HF bath and the wafers in the back two boats are stripped in wbsilicide cassettes at the wbsilicide 6:1 HF bath until hydrophobic (~30 minutes), then dump rinse and spin dry. There should already be enough clean stripped dummies (metal and nonmetal) in the cart for you to fill the boats while you strip the others and return them to the cart for the next person. Remember if you leave dummies with 2.95u or don’t strip the dummies for the next person -- they will not be pleased.
Unload your wafers, push ALARM ACK to send the boat back in. The status will change to END and it will alarm again. Press ALARM ACK to end the alarm. This will leave the status in READY mode.
Measure the thickness and enter value in appropriate areas LPCVD log book.
LOAD THE PUMP PROGRAM
Load the pump program Check the status of the door interlock. Push RUN. Make sure it gets to step 25 before leaving the lab.
Disable the furnace.
Tylan LPCVD Furnace Module (short)
Clean substrates: diff clean with HF last
Enable the furnace
Verify Pump program running
Go to the furnace and use the STATUS button to verify that the system is in 'RUN' mode and running the “PUMP program”.
End Pump program:
ALARM ACK twice
Verify the Tube is vented
Ten minutes after the pump program has ended you must manually test that the tube is vented. Push MANUAL on the boat puller, push FAST, then LOOK AT THE TUBE while you hold down OUT. You should immediately see the boat start to come out. If it does not, stop and wait 10 more minutes and test it again.
Load your program
(only after verifying manually that tube is vented)
From TYCOM type "LO <program name> <furnace#>" <RET>. You will be asked to enter the deposit time.
Load your wafers
Send in tube
ALARM ACK once
Take pressure readings during the gross leak check, leak check and the deposition steps of the program and write the values in the logbook.
ALARM ACK twice
Load pump program
Run Pump program
Measure wafers and log results
Disable the furnace.
Process Monitoring and Machine Qualification
To provide a standard procedure to monitor Nitride thickness and uniformity both wafer-to-wafer and within-a-wafer.
To be completed after major maintenance such as a tube change or on a set schedule to be determined or as needed based on user feedback.
Test results are recorded on Coral.
- Use four new 'L' test wafers; <100>, P-type (boron), 10-20 ohm-cm.
- Clean at wbdiff in the following sequence; 5:1:1 DI:H2O2:NH4OH ten minutes, rinse, 5:1:1 DI;HCl:H2O2 ten minutes, rinse, 50:1 DI:HF 30 sec, rinse, spin dry.
- Load program NewLSN into Tylannitride furnace. Time variable is 00:30:00.
- Load wafers into boats using very clean tweezers or vacuum wand. Load wafers with the major flat up into the boats in the following positions:
1st boat: (Front), 20 empty slots,
1st two dummies,
1st boat: two test wafers(slot 23 & 24),
1st boat: one dummy.
2nd boat: one dummy,
2nd boat: two test wafers (slot 2 &3),
2nd boat one dummy, 21 empty slots.
Use Nanospec to measure poly thickness at the flat, center, bottom, left and right on each wafer. Test sites should be no more than about 15mm from the edge of the wafer.
Record results on the on coral. If test’s values aren’t not within 10% of plotted test average, contact the Diffusion Process/Maintenance team.
Save wafers in a box with the date, furnace number, program name and growth time. They may be re-tested sometime in the future.