Sputter Deposition of Silicon Dioxide

Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006 Sputter Deposition of SiO2 and Si3N4 Standard Operating Procedure

Equipment Setup:

3 1.Chamber Control Panel 2.Meter Control Panel 1 2 3.Gas Flow Control Panel

Turn on pumps and Load the wafer:

1) Turn on Argon and high purity nitrogen in East room (Argon is for the formation of plasma because of its lower metastable state. The Nitrogen is for flushing the chamber and the Nitrogen gun by the sputterer. The Nitrogen canister near the sputter system is process gas). 2) Turn on the roughing mechanical pump. Make sure the roughing valve is closed (black valve handle behind sputterer, left of the liquid N2 funnel) Currently there is no switch for the pump. Just plug it in. 3) Make sure process gas valves behind instrument are open (N and Ar/O). 4) Turn on graphical high pressure gauge. (NOT ion gauge). See photo below. 5) Flood chamber with high purity N2 to raise to atmospheric pressure. Use valve labeled "N2 leak" on front panel. Once you can feel N2 leaking out from around the chamber, it is at atm pressure (you may have to go to different locations around the perimeter of the chamber). This will take about 3-5 minutes. Close the N2 leak valve. 6) Wearing gloves, raise tray holder using switch to the right of the chamber and load wafer onto thick quartz plate. Rough out the main chamber and gas manifolds:

7)Open the rough-ing valve.

1.Digital high pressure gauge 2.Throttle controller 1 2 3.Graphical pressure gauge 4.Ion gauge controller

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1 Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006

8) Flush the chamber with nitrogen from East room 2-3 times using N2 leak valve in order to clean out the moisture for better pump down.

Rough out the gas manifold:

9) Open Leak valve (UP position)

Leak valve

10) Make sure the valves of the process gas tanks are off, the needle valves are open, and the large valves next to them closed.

Needle valve

Gate valve

11) Rough chamber to 50mT (read Channel 1 on the graphical pressure gauge). 12) Open T-valve located under the machine (this is the valve between the Baritron and the chamber). Turn on the digital high pressure gauge (upper left control box; see previous photo). 13) Close the roughing valve (CW) (It is essential to do this so as not to destroy the cryo pump. If the mechanical roughing pump is pumping out the chamber at the same time the gate valve is open, the cryo pump will suck the pumping oil out of the mechanical pump destroying itself and contaminating the chamber). 14) Turn on throttle controller (upper right control box). Flip throttle control switch up until throttle indicator reads 100%. Open the gate valve (see figure above). (The throttle controller is always active even when the system is off. The throttle controls the openings between the cryo pump and the chamber, the throttle controller has 3 states: open/upwards – increase throttle, close/downwards –

2 Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006 decrease throttle and horizontal – stay constant) if you power down the throttle controller the gauge will stick. 15) At this point the high pressure gauge should read 1 mTorr or lower, and it is now safe to turn on the ion gauge. Never turn on Ion Gauge at high pressure

Throttle indicator

Throttle control (pictured in neutral position, horizontal)

16)Turn on ion gauge. Pump down the chamber to high vacuum. This reduces contaminants in final film, with lower pressure giving higher purity films. Generally 3-5 micro Torr is considered sufficient. (Note: at the time of Rev. A of this SOP, 1 x 10-5 Torr was sufficient). This will take 1.5-2 hours.

17)Turn on digital high-pressure gauge. 18)Zero out (#2) high pressure gauge with jewelers screw driver; 19)Turn off ion gauge 20)Turn on cooling water circulation (big round red valve in back of machine near plug for roughing pump; make sure valve on green tube near machine is open- parallel to green line). 21)Turn on RF power (To the right of the chamber, located low).

Clean the target and wafer:

22) Add process gasses: Close fine needle valves loosely and open all process gas valves in tanks to the right of the machine. Throttle to zero by closing throttle control valve, then putting it back in neutral. Slowly open the big Argon or Oxygen valve depending on process, to stated pressure in recipe. This pressure

3 Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006 will be read out on the Digital high pressure gauge. Use needle valve to fine- adjust; if you overshoot, close needle valve a bit until desired pressure is attained. Next open nitrogen valve to attain final combined pressure of both gasses (Example: for Nitride deposition, add Ar until 13mTorr pressure, then add 4mTorr N2 until you get 17mTorr total).

Inside chamber: There are four pairs of plates facing each other. On the ceiling of the chamber, there are four fixed plates containing the targets SiO2, Si3N4, and pyrex; the remaining one plate without any target is for the sputter etch of the wafer. On one of lower four plates, there is a table for the wafer, and these four plates can be rotated so that deposit occurs when table faces one of the targets. The target selector determines the place of the plasma (near the selected target), table selector defines which target the wafer faces. The Load and Tune are used to match the impedance of the RF power source and the plasma in order to obtain maximum forward power and minimum reflect power. It is essential to watch the system whenever the plasma has been ignited since the impedance of the plasma can change quickly and cause the reflected or forward power to go beyond desired levels.

23)Clean target. Sputter the target to clean organics i)Setup: mode = sputter deposit, target = desired target, table = opposite target (table should be opposite to the target, so that wafer is far away from the target during the target cleaning process). ii)Tune and Load depend on the recipe. Refer to log entries for latest recipes and this SOP for some current settings (reading of the Tune and Load = number in the window X 100 + number pointed by the pointer). iii)Turn on sputter power, then use power adjust and tune together to take forward power to desired level (again refer to table 1 and log entries) and reflected power as small as possible. iv)Wait desired time (e.g. ½-3 minutes). v)Turn power adjust all the way down CCW.

24)Clean wafer: i)Setup: mode = sputter etch, target = Etch, table = Etch; ii)Adjust Load and Tune; iii)Turn on power adjust CW until you see plasma. iv)Wait for 3 minutes or so. Remember you are bombarding your wafer with Ar so you may be removing desired layer, e.g. gold, etc. In general etching is slow, so a 3 min clean will not affect substrates adversely. v)Turn power adjust all the way down CCW.

Deposition

4 Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006

Note: when sputtering silicon nitride, add Argon and Nitrogen in the proportions shown with throttle valve at 0%, then open the throttle valve until there is 8- 18mTorr total pressure in chamber.

25) Setup: mode = sputter deposit, target = desired target, table = desired target; 26) Turn on power adjust CW until you see plasma. 27) Throttle to 15%. Pressure on digital high pressure gauge will read about 8mTorr. 28) Tune and load depending on process. At the time of Rev. A no change was made to load, only tune. Check logbook for last entries. 29) Forward power will bounce around for first few minutes, and then settle to steady state. However, dial must still be watched for entire process. Deposit for set time. Use previously developed recipes to estimate sputter rate. 30) Turn off power adjust. 31) Move wafer stage to the front.

Shut down the system 32) RF power off. 33) Close tank and manifold valves of all the process gases Ar and O2. 34) Close big gas valves, the open all needle valves for next run. 35) Adjust throttle to 100%, then neutral. 36) Power off the throttle. 37) Close T-valve under machine. 38) Close gate valve (CW). 39) Close leak valve on gas manifold (down position). 40) Open nitrogen leak valve to raise the inside pressure to atmosphere pressure. Again feel around outside of chamber to make sure you feel N2 leaking out. 41) Open the chamber and take wafer out and close the chamber. 42) Open rough valve. 43) Rough the chamber down to 100 mTorr (digital high pressure gauge) to avoid contamination. 44) Close rough valve. 45) Unplug roughing pump to depower. 46) Turn off high pressure gauge. 47) Turn off red water valves; failing to do so will drain di water system. 48) Turn off RF power. 49) Turn off nitrogen and argon (in East room). 50) Done!!!

5 Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006

Table of recipes

Silicon Oxide Clean target Clean Wafer Deposit Argon 24 mT 24 mT 24 mT Oxygen 4 mT 4 mT 4 mT Nitrogen 0 0 0 Tune 100 470 100 Load 1040 880 940 Forward Power 200W 200W 350W Dep rate / etch time 3min 3 min 67 A/m

Silicon Nitride Clean target Clean Wafer Deposit Argon 13 mT 13 mT 13 mT Oxygen None None None Nitrogen 4 mT 4 mT 4 mT Tune 25 470 1480 Load 950 870 900 Forward Power 125W 200W 200W Dep rate / etch time 3 min 3 min 100 A/m +

6 Micro-fabrication Recipe: Sputtering of dielectric material Jiandong Fang and Rob MacDonald, 2001 Tai Chen, Sarah McQuaide, Rev. A, 2006

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