TECHNICS HUMMER V SPUTTER COATER
Lubbock, Texas Tech University
OPERATION OF THE TECHNICS HUMMER V SPUTTER COATER
NOTE: This instrument can be used for standard tungsten SEM imaging (S-570) or for High or Ultrahigh resolution SEM imaging (field emission; S-4300 SE/N; S-5000, H-8100STEM). The set-up and start-up of the sputter coater is the same in either case, although the actual operation parameters change depending on the sample and the imaging instrument used. The deposition parameters for coating samples for either type of microscope have been empirically determined to place a thin (tungsten SEM) or particulate UHRSEM) coating. It is up to the operator to determine what is/are the most appropriate operational parameters for their particular needs.
NOTE: You can always add more coating on to a sample, but you cannot remove it once it has been sputtered on. Therefore, it is recommended that you be conservative on the initial coating and check it on the SEM (this is particularly critical for ultra-high resolution imaging). If charging occurs, image the sample at a lower KV and/or beam current.If this does not fix the problem, re-coat the sample as before, but tilt it slightly in the coater.
NOTE: This is not a jewelry-making class. The sputter should always be light enough that you can see the sample through the metal coat. You do NOT want to make a continuous thick coat across the sample surface. Thick coats will limit topographic resolutionand increase noise due to increased back scatter production.
I. START UP
1. Allow any paints, glues or adhesives to dry thoroughly before placing the sample in the sputter coater.
Lift the lid of the coater. It might stick to the bell jar gaskets, so be careful and do not allow the lid of the coater to fall back on to the bell jar (twisting the bell jar on the bottom seal will help break it free of the base).
3. Remove the bell jar and place it on its side on the counter (DO NOT place the bell jar on its end since this will allow dust or fibers to stick to the gasket, and cause eventual vacuum and plasma generation problems).
4. Place your samples on to the stage (the anode) a large number of samples can be done at one time.
AVOID TOUCHING ANY PART OF THE COATER THAT WILL BE IN THE VACUUM. THIS INCLUDES THE STAGE (ANODE), TARGET, THE INSIDE OF THE BELL JAR, ETC. IF YOU DO, SEE THE TECHNICIAN SO IT CAN BE CLEANED.
NOTE: Fingerprints or other oils will volatilize in the vacuum, react in the plasma, and re-deposit on the sample. For low resolution, low magnification imaging, where the beam is spread, this not a great concern. However, at higher magnifications, the high beam intensities will cause any hydrocarbons that had been deposited on the sample during coating or sample preparation to contaminate the area under the beam and cause a concomitant decrease in resolution.
CHECK THAT THE GASKET SEALS ARE SEATED PROPERLY AROUND THE ENDS OF THE BELL JAR BEFORE REPLACING THE JAR ON TO THE COATER BASE.
5. Replace the bell jar onto the coater base.Do not drag the gaskets across the anode (stage)
6. Gently close the lid and lower the VENT toggle. Make certain the lid is properly set on the bell jar. If it is not, vacuum cannot be obtained.
7. Turn on the POWER toggle switch. This will turn the mechanical pump on and pumping will begin immediately. Listen for the sound ofthe pump. The pump sound should change tone and become quieter as the vacuum increases in the bell jar. Also, the vacuum gauge needle should start deflecting towards the left.
If the pump sound does not change tone and become significantly quieter within a few seconds, the lid is not seated properly. Move it until it is seated appropriately and the vacuum begins to pull down, by noting both the pump tone and vacuum gauge. Allowing the mechanical pump to pump on atmosphere for an extended period will destroy it
II. ADJUSTING THE BELL JAR GAS PRESSURE
1. While watching the vacuum gauge, allow the vacuum gauge to drop below 60m Torr (this can take From 5-30 minutes depending the type and number ofsamples). Carefully and slowly turn the
PRESSURE control clockwise (toward DECREASE) until the proper vacuum is achieved.
The PRESSURE control is an easily damaged precision needle valve. DO NOT turn it unless carefully Monitoring the pressure on the vacuum gauge and allowing time for equilibration. DECREASE (Clockwise) on the needle valve decreases the gas pressure (increases the vacuum). Closed (DECREASE) on the needle valve is actually about three (3) revolutions on the knob before any Resistance is felt. IF ANY RESISTANCE IS FELT: BACK OFF!!!! DO NOT CLOSE THE NEEDLE VALVE TIGHTLY AS THIS WILL DAMAGE IT!!!!!
NOTE: The last person to use the sputter coater should have left the PRESSURE control at a point close to where proper vacuum can be achieved when you turn it on (40-60mTorr). Allow the vacuum time to equilibrate before turning the PRESSURE control again (SEE THE 'CAUTION' ABOVE).
2. Open the Argon gas cylinder with the gray handle on top of the cylinder and immediately close it.
There is enough pressure in the gas line for several sputter coater runs.
3. Check the regulator gauge and make sure the secondary gauge (the one farthest from the cylinder).The gauge pressure should read slightly less than 10 lbs.(the first mark on the scale). If this gauge is not reading around 10 lbs., inform the technician so it can be adjusted appropriately.
4. a) Flush the bell jar with Argon by turning the PRESSURE control to 'INCREASE' and allow the pressure to rise above 200 mTorr.
b) Carefully close the PRESSURE control ('DECREASE') and allow the vacuum to reach at least 50 mTorr. DO NOT OVERTIGHTEN THE PRESSURE CONTROL.
5. Repeat steps 4a and 4b 2-3 times to insure all of theionizible gas (i.e. air) within the bell jar has been replaced by non-ionizible Argon gas.
6. Allow the vacuum to reach 50 mTorr while adjusting the PRESSURE control.
7. If the pressure decreases below 50 mTorr, add Argon tothe bell jar by INCREASING the PRESSURE control until this pressure is achieved.
III. SPUTTER COATING
1. check that the PROCESS control rocker switch\s set to'MANUAL' and the PULSE toggle witch is set to 'OFF'.
2. Check that the top switch is set to PLATE D/C.
3. Make sure the HIGH VOLTAGE rheostat (VOLTS) is turnedto '0' (zero).
4. IF:You are sputter coating for a tungsten emitter SEM: GO TO (A)
You are sputter coating for a field emission SEM: GO TO (B).
A) SPUTTER COATING FOR THE S-570 (tungsten filament)
1. Turn the HIGH VOLTAGE rocker switch 'ON'. The adjacent red lamp should light [If the red light does not come on, check to make certain the PROCESS CONTROL rocker switch is set to MANUAL].
TUNGSTEN SEM COATING PARAMETERS
10 mAmps at l0kV, 1-1.5 minutes
these coating parameters will deposit Au/Pad at a rate of100 Å (10 nm)/minute. Therefore, a 1-1.5 minute sputter coat is a thin coat of10-15 nm generally a sufficient particulate sputter coat for the tungsten filament instruments. Samples with high topography may require slightly longer coating times that must be determined by the user based on the appearance of the image in the SEM.
2. Slowly turn the HIGH VOLTAGE rheostat (VOLTS) slowly up to '10' while watching the MILLIAMP METER at all times. This meter should not deflect, or deflect only slightly at this time as the plasma is beginning to form inside the bell jar.
3. Adjust the PRESSURE control (INCREASE) to achieve a current of 10 mAmps (≈ 55 mTorrs) ('MILLIAMPS' on the MILLIAMP METER). Remember that the coating is being deposited when the purple plasma becomes visible.
The 10 mAmp current is maintained by adjusting the Argon pressure with the PRESSURE control. The voltage must remain constant at l0kV, so DO NOT adjust the current by changing the HIGH VOLTAGE rheostat (VOLTS).
4. Set the PROCESS control timer knob to the appropriate time (1-1.5 minutes).
5. Flip the PROCESS CONTROL rocker switch to AUTO. This is the timer and will shut the voltage off automatically when the set time is up.
6. Adjust the pressure control to maintain 10 mAmps during the coating process.
NOTE: DO NOT LEAVE the sputter coater while is coating is in progress since constant monitoring and adjustment of the PRESSURE control is required to maintain the 10 mAmp current during the process. Monitor the MILLIAMP meter and not the vacuum. Adjust the PRESSURE control slightly to maintain the desired current ('INCREASE' to increase the current; 'DECREASE' to decrease the current).
B) SPUTTER COATING FOR THE S-4300 SE/M or S-5000 (Field Emission)
1. Turn the HIGH VOLTAGE rocker switch 'ON'. The adjacent red lamp should light [If thered light does not come on, check to make certain the PROCESS CONTROL rockerswitch is set to MANUAL.
FIELD EMISSION SEM COATING PARAMETERS
5 mAmps at l0 kV, 15-30 seconds
The lower sputtering current and shorter coating times will deposit a particulate coating rather than the thin continuous film of Au/Pd required for a tungsten emitter. This particulate coating is generally sufficient for low beam current FESEMs. Samples with high topography may require slightly longer coating times that must be determined by the user based on the appearance of the image in the SEM. The particulate coating will not interfere with x-ray signal to any great extent if EDS microanalysis will be performed on the sample, but will help in removing residual charge.
2. Slowly turn the HIGH VOLTAGE rheostat (VOLTS) slowlyup to '10' while watching the MILLIAMP METER at all times. This meter should not deflect, or deflect only slightly at this time as the plasma is beginning to form inside the bell jar.
3. Adjust the PRESSURE control (INCREASE) to achieve acurrent of 5 mAmps ('MILLIAMPS' on the MILLIAMP METER). Remember that the coating is being deposited when the purple plasma becomes visible.
The 5 mAmp current is maintained by adjusting the Argon pressure with the PRESSURE control. The voltage must remain constant at l0 kV, so DO NOT adjust the current by changing the HIGH VOLTAGE rheostat (VOLTS).
4. Set the PROCESS control timer knob to the appropriate time (15-30 seconds).
5. Flip the PROCESS CONTROL rocker switch to 'AUTO?. This is the timer and will shut the voltage off automatically when the set time is up.
6. Adjust the pressure control to maintain 5 mAmps during the coating process.
NOTE: DO NOT LEAVE the sputter coater while is coating is in progress since constant monitoring and adjustment of the PRESSURE control is required to maintain the 5mAmp current during the process. Monitor the MILLIAMP meter and not the vacuum. Adjust the PRESSURE control slightly to maintain the desired current ('INCREASE' to increase the current; 'DECREASE' to decrease the current).
IV. SHUTDOWN AFTER SPUTTER COATING
1. When the coating time is up, tum the HIGH VOLTAGE (VOLTS) rheostat to '0' (zero).
2. Turn the HIGH VOLTAGE rocker switch 'OFF'.
3. Return thePROCESS CONTROL (the timer) rocker switch to 'MANUAL'.
4. Make certain the Argon tank is 'OFF' (gray handle ontop, clockwise).
5. Decrease the PRESSURE control until the VACUUM meter reads at most 50-60 mTorr (this will allow the next user to assume the sputter coater will immediately pump down to its minimum without having to adjust the PRESSURE needle valve).
6. Turn the POWER toggle 'OFF' and IMMEDIATELY lift the VENT toggle. Initially, lift the vent toggle slightly to allow air to slowly enter the bell jar.
7. After the bell jar has reached atmosphere (about 10 seconds, or after the hissing of gas entering the bell jar has stopped). Leave the VENT toggle in its 'OPEN' position ('UP').
NEVER LEAVE THE BELL JAR UNDER VACUUM WHEN THE ROUGHING PUMP IS OFF. IF YOU DO, PUMP OIL WILL BE PULLED INTO THE BELL JAR
V. RETRIEVING THE SAMPLES
1. Carefully lift the bell jar lid to remove the specimens (use your thumbs under the lip of the cover to initially break the seal). DO NOT let the cover drop back down on the bell jar.
2. Remove the bell jar and place it on its side in the tray provided on the counter (twisting the bell jar on the bottom seal will lhelp break it free of the base).
NOTE: DO NOT place the bell jar on either end (the gaskets) since this will allow dust or fibers to stick to the gasket, and cause eventual vacuum and plasma generation problems.
3. Retrieve your specimens without touching any part of the sputter coater that will be under
vacuum. Usually, it is easiest to remove the bell jar and lay its side in the tray provided on thecounter. MAKE CERTAIN THE BELLJAR DOES NOT ROLL.
ALWAYS LAY THE BELL JAR ON ITS SIDE, AND NOT ON EITHER END where dust andfibers can contaminate the gasket!!!!!
VI. CLEANING THE BELL JAR
NOTE: Each time the sputter coater is used, it must be cleaned to remove any sputtered metal and hydrocarbon contamination that may have been deposited there during the process. A light coat of detergent is applied to the interior of the bell jarto the interior of the bell jar after each sputter coat process to provide a non-stick surface that is easily cleaned. It is required that the bell jar is cleaned after each use.
1. Place a small drop of the provided dish detergent to a clean cloth found in the lap drawer below the sputter coater.
2. Wipe the inside surface of the bell jar thoroughly halfway from one end of the jar. Go to the other end and repeat the procedure for the other half of the jar. Add some more detergent to the cloth if you need to, but in the end, you want only a very thin layer of the detergent on the interior of the bell jar.
3. Black residue should come off onto the cloth. This is the residual metal from the sputter coater run. Wipe the surface until it appears dry.
4. Critically inspect the bell jar and make sure it has been thoroughly cleaned and the soap is evenly spread and the metal has been removed. If any spots of metal or residual detergent remain, wipe them off.
CHECK THAT THE GASKET SEALS ARE SEATED PROPERLY AROUND THE ENDS OF THE BELL JAR BEFORE REPLACING THE JAR ON TO THE COATER BASE.
5. Replace the bell jar on to the sputter coater, beingcareful not to drag the gasket across theanode (stage).
6. Gently lower the lid onto the bell jar. Make sure the VENT toggle is 'UP'.
7. Check again that the Argon cylinder is 'OFF' (gray handle on to, fully clockwise).
NOTE: The technician will clean the anode (stage) in a similar manner weekly or monthly depending on usage.