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Berkeley Microlab

Chapter 6.04

CPA Sputtering System

(cpa - 584) 1.0 T it l e CPA Sputtering System 2.0 Pu rp o s e This document has specific operation and process information about the CPA 9900 Sputtering System. This machine is used to sputter Ti, Al/ 2% Si, Ni and W films on 4" and 6" and 8" wafers. 3.0 S co p e The CPA 9900 sputtering system has four targets for DC magnetron sputtering and load-locked, heated end stations. The targets currently available are: Ti Al/2% Si Ni W Location #1 Location #2 Location #3 Location #4 99.999% Pure

These targets are labeled on the front of the system. Dedicated pallets are provided for each metal film that will be sputtered. They are stored in the storage unit below the right loading station and clearly labeled on front of the case door. Do not mix pallets. This will cause cross contamination issues. The system has the ability to sputter targets sequentially. It is equipped with a 10-inch cryopump and -7 has a base pressure of 2 x 10E Torr. Substrates processed in this tool must be inorganic, low vapor pressure materials. 4. 0 Ap p l i ca b l e Do cu m en t s Revision History 5. 0 Def in it io n s & Pr o c e s s T e rm in o lo g y N/A 6.0 S af et y 6.1 6.2 6.3 7. 0 Make sure pallets are all the way into the elevator before closing the load lock gate valve. Turn on the water to a target before turning on the DC power to the target. Turn off the ion gauge before opening the throttle valve (gas will flow with open throttle).

St at i st ic al / P ro c e s s D at a CPA statistical data are posted under the process monitoring section of the Microlab home page.

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Chapter 6.04

8. 0

Av ai l ab l e P ro c es s , G as e s, Pr o c e ss N o t e s Available Process 8.1 The CPA machine uses DC magnetron cathodes to sputter uniform film from Four Targets currently available for this tool (Ti, Al/2%Si, Ni and W). The CPA's linear design has three major sections; two load locks, end chambers, and a main process chamber. The CPA elevator (right load lock) can hold up to 9 pallets, at slots below the top dummy pallet. Each pallet can hold nine 4" wafers or four 6" wafers and with a dedicated pallet, one 8" wafer. Since there is not enough room to open the chamber door fully to load and unload pallets in the left L/L station, only use the right L/L station for loading and unloading. An elevator in the load locks automatically loads the pallets onto a constant-speed conveyer which moves them from the load lock, the pallets moving through the main process chamber to the opposite load lock and automatically sputtering the wafers in the process. The conveyor or track may be reversed for multi-pass or sequential deposition. Substrates processed in this tool must be inorganic, low vapor pressure materials in the standard mode of operation. High vapor pressure materials, polymers, photoresist and organics may be permitted in this tool, but only following process/application review and approval by Process Engineering Manager. Failure to do so could result in cryopump damage beyond repair, which means long CPA down time, and tens of thousands of dollars in cryopump replacement cost. Kapton tape may be used in CPA with power setting at or below 1000 W. Make sure to give enough delays for multiple passes to cool down the substrates, and never exceed the 1000 W power on any of the recipe setting/target material, while using Kapton tape. Failure to follow these precautions can also result in cryopump damage. Dedicated pallets are provided for each metal film. Please do not mix the pallets in the storage unit or during sputtering. Mixing pallets will cause cross contamination issues, hence, profoundly impact other members' device/products, possibly destroy their work. Moreover, cross-contaminated pallet cannot be adequately cleaned by our metal etch/cleaner, and will have to be replaced at a cost.

Process Notes 8.2

8.3 8.4

8.5

8.6

9. 0

Eq u ip m en t O p e r at io n 9.1 9.2 Enable the system on the Mercury. Operation of the system is automated when the AUTO MODE LED's are lit on the Left Load Lock (left L/L), Right Load Lock (right L/L), and the Main Chamber of the AUTOMATIC VACUUM CONTROLLER, located in the center of the system. Most members however, use the tool in manual mode (Auto/manual mode is flipped to manual) on the same panel. In either automatic or Manual mode of operation if any of the MAINT LEDs (maintenance LED's) or Alarm LED's are lit, then DO NOT operate the system. Report the problem on the Wand. Check the right side and left side L/L heaters to see if they are on (L/L should be warm to the touch). Ask staff to turn them on, if they are not. Do not adjust the setting. Vent the right L/L station as per follows: 9.4.1 Turn off the ion gauge. 9.4.2 Push the STANDBY button either over the right L/L, on the L/L Control panel, or by using the Automatic Vacuum Controller. This closes the L/L gate valve, isolating the chamber from the rest of the system. Wait for the L/L gate valve to close -- you will hear a distinct clank when it does. This takes approximately 10-15 seconds.

9.3 9.4

9.4.3

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cpa 9.4.4 9.4.5 9.5

Chapter 6.04 Push the VENT button to bring the L/L chamber to atmosphere. If you vent too soon (while gate valve is open), you might raise the pressure of the chamber. Unlatch the chamber door.

Check to make sure that an empty pallet is sitting in the top slot of the elevator assembly. It will catch any flakes falling from the top chain and protect the wafers on the pallets underneath from being contaminated. Use the raise/lower switch above the L/L to raise the elevator so it is near the top of the chamber. When you reach the top, the upper limit LED (on the L/L Control panel) will light up. Place your process wafers on a pallet(s) and slide it into a slot in the elevator; make sure it is level and in the center of the elevator. Check pallets again to insure they are level -- it is easy to misalign them. Manually (using the raise/lower switch) move the elevator down until the bottom pallet is ONE SPACE above the tracks (if not already there). Make sure to follow material compatibility/process rules noted in sections 8.3-8.5, before proceeding to the next step. Close the L/L door and, while holding firmly, press the PUMP button on the L/L Control panel. Wait for the pump to kick in, and check that the L/L door is held firmly by the vacuum. The gate valve of the load station will automatically open and the system will cross over into hi-vac at ~200 mTorr. When crossover into high vacuum is complete (you can hear the cryo kick in), you may turn on the ion gauge.

9.6 9.7

9.8

9.9

The following steps can be done while the system is pumping down (about 15 - 30 minutes): 9.10 The opposite L/L chamber must be prepared for receiving processed pallets. Lower the pallet elevator to the bottom position, enough to get the processed pallets in, by using the RAISE/LOWER switch to lower. 9.11 Set SPEED SELECT switch to VARIABLE. 9.12 Set the TRACK SPEED setting as necessary. You can use the following equation to get an idea of the speed you will need: C=T*V C = Deposition Constant (Å*(cm/min)) T = Film Thickness (Å) V = Track Speed (cm/min) The current aluminum process parameters and Deposition Constant you need to determine the required track speed for a given thickness are listed at the Nanolab process monitoring web site. The track speed can be obtained by dividing the Constant by the desired film thickness for the process condition. Additional deposition constants can be obtained through relatively simple experiments, see process staff for details. Aluminum/2% Silicon Power: Pressure: Constant: Example: Note: Note: 4 kWatts 6 mTorr 40,610 A*cm/min. 20 cm/min. gives ~ 2030 A of Al/Si

The constant changes with target usage. The track speed is inversely proportional to the thickness, and the power is directly proportional to thickness. Keep track speed above 9 cm/min. Perform at least two passes to prevent substrate overheating and keep power out of the extreme upper and lower ends for consistent results.

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cpa 9.13 Set TRACK TRAVEL DIRECTION to REVERSE (i.e., to the left). 9.14 Wait for the pressure to reach a minimum of 5 x 10

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Chapter 6.04

Torr on the ion gauge readout.

9.15 Select High or Low process pressure via the pneumatic switch above the etch controller. Turn off the ion gauge and push the THROTTLE button on the Main Chamber section of the Automatic Vacuum Controller. This will turn on the process gas. Wait for the pressure to stabilize, 15 to 30 seconds. 9.16 Turn the GAS FLOW ADJUST knob, located below target #2, to set the Process Gas FLOW LED display. 9.17 Initiate cooling water to your target by using the rotating lever now on the right-hand side of the machine (as you're facing the front of the machine). A green button will light up, showing that water is flowing, and only then will it allow you to turn on the DC power. Note: If you do not turn on the target cooling water, you will not be able to strike a plasma! Adjust the power level by using the CONTROL knob. Observe plasma through viewport and make sure it looks stable. If the target is arcing, it needs to be conditioned. Do not run the machine. Report the problem on Mercury.

Note:

9.18 Set power to your recipe settings. Note max power for Ti = 1.5kW, W = 2.0 kW, Ni = 2.0kW and Al = 4.0kW. 9.19 Push the L/L index toggle switch down to LOWER and release to index the pallet elevator down one slot. Repeat until the pallet reaches the chain track. DO NOT lower the elevator past the pallet slot until the pallet has left the L/L. When the pallet lowers down to the chain track, if placed incorrectly if may start rotating on the track, becoming stuck on the vertical rollers.

It will then be impossible to move it backwards or forwards. If your pallet does start to rotate on the track, immediately return to the load lock.* Open the L/L and check to make sure the pallet is not warped. Next, if the pallet is not warped, reposition it correctly. To move things along more rapidly, you may leave the SPEED SELECT in the FIXED position (80 cm/min.) until your dummy pallet gets to the target and at that point switch it to the VARIABLE position to get the desired process track speed. Be sure to switch the speed BEFORE your wafers arrive at the target, about an inch from the deposition chamber, to insure a uniform metal layer. Pallets will move sequentially under the targets and end up in the left load lock. 9.20 Pallet removal may begin once all the pallets are in the L/L. Note: If you want to run another pass, proceed with a) below, reset per step 10 for opposite direction, push throttle, turn on P.S. and push start.

9.20.1 Turn off the power of the D.C. power supply and push the PUMP button on the Main Chamber section of the Automatic Vacuum Controller. This will turn off the process gas and open the high vacuum valve. To avoid breaking the gate valve by cranking the pallet,

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Chapter 6.04 make sure that ALL the pallets are in the L/L, then stop the track by setting the TRACK TRAVEL DIRECTION switch to the center position. 9.20.2 Press STANDBY on the left End Station L/L Control panel or on the Automatic Vacuum Control panel. This will close the end station L/L valve. 9.20.3 WAIT until you hear the L/L gate valve close and press VENT to backfill the end station to atmosphere. 9.20.4 Unlatch end chamber door. 9.20.5 Remove pallets from end station from the bottom up to prevent particles from contaminating your samples. 9.20.6 Close door and latch. 9.20.7 Push PUMP while pressing FIRMLY on the L/L door to insure it is closed and check to see it seals properly. This will rough out the chamber and cross over to high vacuum automatically. To prevent debonding, make sure that you have run the cooling water at least 10 minutes after turning off power to your target. 9.21 When you are finished, 9.21.1 Turn on the ion gauge tube, to monitor machine pressure. 9.21.2 Make sure the RF sputter etch controller is left in MANUAL. This will disable it. 9.22 Disable the system and enter your process parameters and results in comments. Note: Every time the targets are changed and the chambers are exposed to air, the targets have to be reconditioned. This is done by a staff member.

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Chapter 6.04

10 . 0 T ro u b l e sh o o t in g G u i d el in e s N/A 11 . 0 F ig u r es & Sc h e m a t i c s N/A

CPA Study Guide

Be sure to know: 1. Which materials are NOT allowed in CPA 2. Maintenance LEDs 3. Pre-Start-up checks 4. Ion gauge when it should be on or off 5. Venting the load-lock 6. How to obtain process parameters for Al deposition 7. Base pressure 8. Throttle 9. Using the viewport 10. Track speed 11. Loading and unloading pallets. 12. Troubleshooting problem pallets. 13. Target pre-sputtering. 14. Setting the target. 15. Typical film quality problems and troubleshooting them. 16. DC power supply, and cooling water. 17. What plasma is; how it is used?

12.0 Ap p en d ix 12.1 Low Power Titanium (Ti) and Tungsten (W) Deposition Recipes Ti deposition: Power = 1.5 kW Pressure = 7 mT Track speed = 30 cm/min Dep rate ~ 600 A/pass W Deposition Recipe: Power = 2.0 kW Pressure = 10 mT Track speed = 35 cm/min Dep rate ~ 1000 A/pass Target Inventory: AlSi (99.999% pure), Ti, W (99.999% pure)

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