CMP
The POLI-400L CMP (Chemical Mechanical Polishing) system is designed to polish standard 4” wafers (no pieces). CMP is often used to polish wafers, to planarize patterned surfaces, and to smooth surface roughness.
Contents
Training to Become a Tool User
Picture and Location
The tool is located in Room 159 (the Wafer Saw Room) directly across from the Stockroom.
Background
The process uses an abrasive and corrosive chemical slurry (commonly a colloid) in conjunction with a polishing pad and retaining ring, typically of a greater diameter than the wafer. The pad and wafer are pressed together by a dynamic polishing head and held in place by a plastic retaining ring. The dynamic polishing head is rotated with different axes of rotation (i.e., not concentric). This removes material and tends to even out any irregular topography, making the wafer flat or planar. This may be necessary in order to set up the wafer for the formation of additional circuit elements. For example, this might be necessary in order to bring the entire surface within the depth of field of a photolithography system, or to selectively remove material based on its position. (from Wikipedia)
For more information about CMP research, here is link to the AVS CMP Working Group Proceedings: https://nccavs-usergroups.avs.org/proceedings_cmpug/
Process Capabilities
SNF Provided Consumables:
SLURRY:
Si & poly Si - Ultra-Sol S-10 colloidal silica (no mixer needed)
* Functional Particle Size: 0.070µ (microns)
* Percent Solids: 30% (wt%)
* pH 10.9
Oxide - Ultra-Sol 2EX colloidal silica (no mixer needed)
* Functional Particle Size: 0.070µ (microns)
* Percent Solids: 30% (wt%)
* pH at 20-25C: 10
PADS:
IC 1000 for topology applications, stiffer. Order grooved & stacked (slightly softer layer between pad & adhesive for better uniformity)
Cleanliness Standard
CLEAN NON METAL or GOLD CONTAMINATED consumable group:
1. Check the sign above the left CMP door to see which set of consumables are installed (CLEAN NON METAL or GOLD CONTAMINATED).
2. Be sure that you are using the correct platen, polishing head and conditioner for the contamination level of your wafers.
3. CLEAN NON METAL consumables: to polish silicon, poly silicon, thermal oxide, LTO.
3.1. Wafers will need to be KOH decontaminated after polishing as detailed on the SNF website under Processes, KOH Decontamination.
4. GOLD CONTAMINATED: to polish wafers that have, or has had, any type of metal on them.
4.1. These wafers cannot be decontaminated & cannot go back into clean or semi-clean tools in SNF.
5. Contact staff if you need to change from CLEAN NON METAL to GOLD CONTAMINATED consumables.
6. Change the sign to the appropriate consumables group.
7. Contact staff if you want to polish non-standard materials.
Performance of the Tool
What the Tool CAN do
- Polish 100mm diameter wafers, 500-550um thick
What the Tool CANNOT do
- Polish partial wafers or chips
- Polish extremely thin or extremely thick wafers, check with staff
Training to Become a Tool User
The CMP tool is very sensitive to cleanliness and requires significant attention to detail for the set up and cleaning procedures. Our training procedure to become a user on the CMP is to first become familiar with the information on this page. The next step is to shadow users on the CMP until you are comfortable that you know the procedures well. Then contact staff to set up a time to take a closed-book written exam. After successful completion of the exam either staff or a superuser will evaluate your first run.
Operating Procedures
1. Safety:
WARNING: Always wear safety glasses & gloves while using the tool. Use a bouffant hair cover, blue lab coat or plastic apron if desired.
WARNING: NEVER RUN THE SYSTEM WITH ANY OF THE DOORS OPEN OR ANY SAFETY INTERLOCKS DEFEATED.
WARNING: MISUSE OF THE SYSTEM IN ANY FORM OR NOT FOLLOWING THE DEFINED PROTOCOL WILL RESULT IN IMMEDIATE REVOKE OF YOUR TOOL USE PRIVILEGES.
WARNING: DRIED SLURRY IS EXTREMELY DIFFICULT TO REMOVE. BE SURE TO WIPE ALL SURFACES, INSIDE & OUTSIDE THAT HAVE SLURRY RESIDUE.
The System
2. System turn on:
2.1. Contact staff to install the end-point detection system if required.
2.2. The red main power switch on the right side of the tool is left on. Do not turn off.
2.3. Turn on the DI water supply at the back left side against the wall.
2.4. Turn on the vacuum at the back left side against the wall.
2.5. Verify the Nitrogen is turned on. The valve is located on the left side of the tool.
2.6. Verify there are a sufficient number of empty waste Carboys available.
2.7. Verify the level of waste in the Carboy in the light blue polypropylene box to the left of the tool.
2.8. Verify there is sufficient slurry, type and volume available.
2.9 Verify table pad is clean, no visible dirt or wafer particles or foreign objects are embedded in the pad.
2.10 Check that the membrane on the polishing head is not torn, ripped, or damaged.
3. Slurry waste disposal in Carboy:
3.1. The waste slurry & rinsing water goes into a white plastic 5-gallon container called Carboy.
3.2. The Carboy is inside the covered plastic polypropylene box to the left of the tool on the ground.
3.3. Inside the polypro box there is a ~2.5” clear tube from the tool that drains into the Carboy.
3.4. There is no drain line to treat & neutralize the waste, so it must be collected in the Carboy & taken away for disposal.
3.5. The level of the waste needs to be monitored frequently to prevent overflowing of the Carboy into the polypropylene box.
3.6. When the Carboy is close to full, stop processing and switch the Carboys, installing an empty one.
3.7. Fill-out and attach the paper waste disposal tag to the full Carboy with the required information including your name, contact information, slurry vendor, name & number, or type of the slurry you are using. Use the full name of the chemical, no abbreviations or formulas. Securely tie the tag to the handle.
3.8. Move the full Carboy to the slurry storage area & place in a double containment plastic tray.
3.9. Put an empty Carboy into the box & reattach the clear tube. Cover with the lid.
3.10. Empty Carboys are located in the chemical storage room.
4. Slurry line priming:
4.1. Get the slurry container you want to use from the chemical storage room & shake as best you can for 1 minute before using. Do not let the cap come off or spill the slurry while shaking.
4.2. Open the doors under the tool & place slurry tube into slurry container.
4.3. Run slurry in manual mode until the liquid color coming out of the slurry line is milky white.
5. Pre-Conditioning of pad prior to use:
5.1. Step 1, Pad Pre-Conditioning a Dry Pad: A dry polishing pad must be thoroughly wetted with DI water for 30 minutes before use.
5.2. Wet the pad using the DI water gun to spray DI water on the pad.
5.3. You may use wet lint free clean wipes to keep the pad wet.
5.4. Repeat often to make sure there is DI water covering the pad for a full 30 minutes.
5.5. Do Not run the DI continuously
6. Step 2, Pad Pre-Conditioning with Slurry: Requires 10 minutes of slurry flow with the conditioner head running, Recipe 2.
6.1. Position the slurry line dispenser tube at the middle of the platen pad.
6.2. Do not let slurry dispense on Head 1 or Head 2.
6.3. Adjust the slurry flow to 2-3 drops per second.
6.4. There should be enough slurry flowing to keep the platen pad wet.
6.5. Increase the slurry flow slightly if the platen pad is getting dry during the polish.
6.6. No wafers and the polishing head must be up.
7. On the touch pad screen, press Auto 2
Platen – ON @ 100RPM Oscillation – ON
Head1 – OFF Slurry - ON
Head2 – ON @ 60RPM DI Water – OFF
Polishing Pressure – 250 g/cm2 Head1 – UP
Retainer Ring Pressure – 350 g/cm2 Head2 – DOWN
Polishing Time – 600 seconds
8. Step 3, Pad Pre-Conditioning Running Dummy Wafers: Run a silicon wafer for 5 minutes using the following recipe, Recipe 3.
8.1. On the touch pad screen, press Auto 3
Platen – ON @ 100RPM Oscillation – ON
Head1 – ON @ 60RPM Slurry - ON
Head2 – OFF DI Water – OFF
Polishing Pressure – 250 g/cm2 Head1 – DOWN
Retainer Ring Pressure – 350 g/cm2 Head2 – UP
Polishing Time – 150 seconds
8.2. Run this Recipe for 2 –150 second cycles
8.3. Rinse off the wafer using the DI water gun.
8.3.1. You do not need to de-chuck the wafer until you have completed both cycles.
8.3.2. After you have conditioned the pad, be sure to rinse off the conditioning head of all slurry. Do not let the slurry dry on the conditioning head, as it will be nearly impossible to remove.
Operating Procedure
9. Chucking a Wafer:
9.1. Use the DI water gun to wet the wafer chuck and the wafer.
9.2. Using a gloved hand, with the side to be polished facing down, place the wafer under Head1.
9.3. Load the wafer so that it rests inside the retainer ring. Make sure the wafer is completely inside the retaining ring.
9.4. While holding the wafer, press the upper right green “chucking” button. This will pull a vacuum on Head1 to hold the wafer.
9.5. Yellow chucking light on the touch screen is releasing wafer, red chucking light is holding wafer.
9.6. Verify the wafer is correctly chucked by checking for wafer movement. You should not be able to move the wafer, at all if it is correctly chucked.
9.7. If you find movement in the wafer, the chucking process must be repeated.
10. Polishing wafer:
10.1. The polishing pad must be correctly conditioned prior to running your wafer.
10.2. It is recommended to start with a dummy wafer before doing real wafer.
10.3. Maximum polishing time is 600 seconds. Using a longer time heats up the retaining ring & the adhesive breaks down and could come off & break your wafer.
10.4. Recommended starting polishing recipe, Auto 1
Platen – ON @ 100RPM Oscillation – ON
Head1 – ON @ 60RPM Slurry - ON
Head2 –-OFF DI Water – OFF
Polishing Pressure – 250 g/cm2 Head1 – DOWN
Retainer Ring Pressure – 350 g/cm2 Head2 – UP
Polishing Time – 600 seconds MAXIMUM
Warning: If you see milky slurry liquid in the 2 small clear tubes on top of Head1, the retaining ring needs to be replaced. Stop polishing and immediately contact staff.
10.5. The conditioning Head2 can be down while running your wafer. If your wafer de- chucks during processing, there is a high probability of breaking when it hits Head2.
10.6. Keeping Head2 down during polishing yields a higher, more consistent polishing rate.
11. Removing a Wafer after Polishing:
11.1. Immediately rinse Head1 and your wafer using the DI water gun.
11.2. Place your hand under the wafer & press the chucking button to release the wafer.
11.3. Immediately move your wafer over to the polypropylene bottle wash wet bench and thoroughly rinse the wafer with DI water at the goose neck.
WARNING: It is extremely important to not let the slurry dry on the wafer as it will be virtually impossible to remove.
WARNING: It is important to use the polypropylene bottle wash bench for cleaning your wafer. This will greatly reduce the amount of waste collected in the Carboy.
11.4. Thoroughly rinse off all the milky white slurry.
11.5. After rinsing, get a clean room wipe, wet it with DI water and wipe the wafer with the wet wipe. Continue to wet the wafer with DI as you are wiping it- it is critical to keep the wafer very wet to prevent slurry from solidifying.
11.6. Rinse thoroughly again with DI water.
11.7. Blow dry with N2 gun, front side first being careful to not let any water streaks on the wafer.
11.8. When you are finished polishing a wafer, prepare a CMP contaminated wafer transfer box to take the wafers from CMP to wbdecon for KOH decontamination. Wafers that are designated CLEAN NON METAL can be KOH decontaminated at wbdecon. GOLD CONTAMINATED wafers cannot be KOH decontaminated.
12. Re-Conditioning between wafers:
12.1. After 10 minutes of polishing, a 60 second pad conditioning needs to be run. Flow slurry and run the conditioning Head2 only. No wafer is required
12.2. On the touch pad screen, press Auto 4
Platen – ON @ 100RPM Oscillation – ON
Head1 – OFF Slurry - ON
Head2 – ON @ 60RPM DI Water – OFF
Polishing Pressure – 250 g/cm2 Head1 – UP
Retainer Ring Pressure – 350 g/cm2 Head2 – DOWN
Polishing Time – 30 seconds
12.3. This will return the pad to the initial condition and restore your polishing rates.
12.4. Be sure to thoroughly rinse the conditioning head2 to remove all the slurry.
13. Purging the slurry line when you have finished all your wafers:
13.1. Fill the 1 gallon plastic bottle with DI water, about half full.
13.2. Remove the slurry tube from the slurry container & put it in the 1 gallon plastic bottle labeled DI Water.
13.3. If the bottle is low, refill with DI wafer at the polypro bottle wash sink using the gooseneck.
13.4. Manually run the slurry until the liquid coming out of the slurry dispense line is clear.
13.5. Remove the tubing from the DI water (while the pump is running).
13.6. Lift the tubing above the pump level.
13.7. Hold until no more DI water is coming out of the DI dispense nozzle.
13.8. Stop the slurry.
13.9. Remove the plastic bottle containing the DI water and dump out the remaining DI water in the bottle wash bench.
14. Pad & tool clean up:
14.1. Thoroughly rinse the bottom & sides of Head1 (polishing head) & Head2 (conditioning head).
14.2. Use a lint free wipe to gently clean the thin rubber membrane on head1.
14.3. Carefully rinse Head1 with the water gun and dry with the air gun.
WARNING: Be gentle as there is a thin black rubber diaphragm that can easily be punctured.
14.4. There are toothbrushes in the storage area below to clean off any accumulated slurry on Head2.
14.5. Use the air gun to blow off Head 1 & 2.
14.6. Thoroughly rinse the platen pad & any accumulated slurry on the side of the platen. You may use a toothbrush to clean the sides of the platen.
14.7. Use the air gun to blow off most of the water on the platen pad & sides of the platen.
14.8. Use the air gun to blow dry the small allen head bolts that hold the platen to the rotating head. By blow drying the bolts dry, it will be easier to remove the platen.
14.9. Use Kimwipes to clean off any slurry splashed on the inside of the plastic windows, flat area outside the platen, touch pad & buttons on the control panel.
14.10. Please leave the tool cleaner than you found it.
14.11. Take any full tagged waste slurry Carboys & unused slurry back into the chemical storage room.
15. Shut down:
15.1. Turn off the vacuum, DI water
15.2. Leave the red main power switch ON at the right side of the tool.
15.3. Inform the staff to remove the end-point detection system if you have used it.
15.4. Disable tool.