OPERATION| 3-1 | GENERAL | ||||||||||
| Operation of the Plasma-Prep II consists of loading the object to be processed, evacuating the reaction chamber, applying the process gas and applying the energizing RF power. The RF amplifier must be resonated and power level adjusted to the appropriate level. Upon completion of the process, the RF power switch is turned off, the vacuum valve switch is turned off. The primary power must remain on for the chamber to bleed back to atmospheric pressure. | |||||||||||
| 3-2 | CONTROLS AND INDICATORS
| Table 3-1 and Figures 3-1, 3-2 are a table of controls and indicators and illustrations
of their location on the machine respectively.
| 3-3 | OPERATION | To operate the Plasma-Prep II, proceed as follows: | | ||||||
| a. | Power, vacuum and RF switches should be off. Meter and AAS switches on. |
| b. | Start vacuum pump. Turn on AC power by depressing the AC switch (No. 1, Fig. 3-1). The pilot lamp will light and the filament of the tubes will glow yellow. Allow the tubes and the vacuum pump to warm up for at least 2 minutes. |
| c. | Open the chamber access door. Make sure the inner chamber is fully into the outer chamber and the gasket is sealed between inner and outer chambers.* Turn on vacuum switch (No. 2, Fig. 3-1), allow approximately 1 minute for pump down. Close access door. |
| *CAUTION: Do not put excessive pressure on the inner chamber. This can cause stress on the glass extension to the vacuum connection and possible failure by implosion of the chamber. | |
| d. | Check to be sure the alarm switch (No. 8, Fig. 3-2) and meter switch (No. 7, Fig. 3-1) are on(upward position). Turn the RF power switch (No. 3, Fig. 3-1)on(upward position). Advance (clockwise) the power level control (No. 4, Fig. 3-1) until there is an indication on the plate current meter (No. 6, Fig. 3-6) of approximately 30ma. Turn the tuning control (No. 5, Fig. 3-11) 90EC counterclockwise and clockwise until a dip in the plate current meter is seen. Rock the tuning control back and forth until a minimum is achieved. Advance the power level control until the meter is indicating 100maE and again rock the tuning control until a minimum is achieved. Full power out will be when the meter indicates 100maE(+/- 20%) at the minimum setting of the tuning control. Operating at lower levels of power is achieved by reducing the power level but maintaining a minimum with the tuning control. |
| NOTE: After the Plasma-Prep II is tuned on the initial use, allow the unit to run for approximately one hour before using it. This will eliminate any contamination which might be present in the chamber. Either air or process gas (O2) can be used for this purpose. | |
| e. | When the alarm sounds, the final amplifier should be retuned to resonance which will be indicated by a dip in the plate current meter and simultaneously an increase in plasma. The audio alarm will stop but may not respond immediately as the infrared of the plates will not dissipate instantly. |
| f. | When operating the unit unattended, the meter switch should be turned off. In this position the power limit circuit is engaged and will protect the power amplifier tubes. To retune, turn the meter switch back on. |
| a. | Turn LEVEL control fully counterclockwise. |
| b. | Turn RF switch off (down). |
| c. | Turn VACUUM switch off (down).* |
| d. | The machine can now be loaded and a process performed. |
| e. | If this is the last cycle of the day, precautions must be taken to avoid contaminating the exhaust line with pump oil. [See NOTE 1]. |
| * If the main power switch is turned off before the chamber returns to atmosphere, it may take a long time to vent. The main power should remain on and the vacuum switch off to vent the chamber. | ||||
| 1. | Remove the sample from the chamber. Remove the inner chamber. | |||
| 2. | With AC on (lighted) and VACUUM toggle switch DOWN, shut off the vacuum pump. | |||
| NOTE 1: Make sure tank pressure is shut off or else gas will continue to bleed and empty the bank. | ||||
| 3. | Leave the pump off for about a minute. | |||
| 4. | Throw the VACUUM toggle UP, then turn the pump back on again for another minute, then shut it off [See NOTE 2]. | |||
| NOTE 2: When using system for asbestos filter preparation, place inner chamber back before proceeding with Step 4. | ||||
| 3-4 | OTHER USEFUL INFORMATION | |||
| a. | oxygen | blue/white |
| b. | argon | fuchsia |
| c. | carbon tetrafluoride | blue/white |
| a. | vacuum line to back of Plasma-Prep to mechanical pump. |
| b. | "O" ring seal between the chambers (check to make sure no extraneous particles are present that would interfere with the vacuum). |
| c. | vacuum line from back of Plasma-Prep to the glass etching chamber. |
| Sometimes mixtures of gases are required in order to accomplish specific ends. One very important case is the removal of epoxy or silicone thermosetting materials (such as the plastic package of an electronic device). Although basically "organic", they are oftentimes filled with various inorganic (most common SiO2) fillers. The gas composition usually used is 10% CF4, 90% O2, with the CF4 removing the filler and the O2 taking away the polymer. Typical etch times are as follows: | |
| a. | Removal of 1ìm SiO2: 25-30 minutes. |
| b. | Removal of 1ìm Si3N4: 30-35 minutes. |
| c. | Cleaning of hybrid device: several minutes. |
| d. | Package decapsulation of I.C.s with several mils of polymer remaining: 85 minutes. In this case, the top portion of the package is ground or milled away so that what remains is only several mils. |
| e. | "Etching" or "ashing" away of a "Nuclepore" membrane filter: 30 minutes. |
| f. | Etching of a "thick section" of OsO4 stained biological material for SEM observation: 3 minutes or less. |
| g. | Gentle etching to reveal inorganics in an organic polymer matrix, such as magnetic storage media, pigment plastics, etc.: several minutes. |
| h. | Cleaning of metallographically prepared samples prior to electron probe microanalysis for carbon: several minutes. |
| TABLE 3-1 AND CONTROLS AND INDICATORS | ||||
| ITEM | CONTROL OR INDICATOR | POSITION | TYPE | FUNCTION |
| 1 | AC | PUSHBUTTON/LAMP | PUSHBUTTON/LAMP | CONTROLS PRIMARY POWER WITH INDICATOR LAMP |
| 2 | VACUUM UP | DOWN | TOGGLE SWITCH | VACUUM SOLENOID VALVE OPEN AND BLEED SOLENIOD VALVE CLOSED VACUUM SOLENOID VALVE IS CLOSED AND BLEED SOLENOID VALVE IS OPEN. CHAMBER IS OPEN TO ATMOSOPHERE |
| 3 | RF | UP | TOGGLE SWITCH | RF POWER IS ON |
| DOWN | RF POWER IS OFF | |||
| 4 | LEVEL | POTENTIOMETER | CONTROLS RF POWER LEVEL | |
| 5 | TUNING | VARIABLE CAPACITOR | TUNES RF POWER AMPLIFIER | |
| 6 | METER | 0 THROUGH 5 | EFFICIENCY METER | POWER AMPLIFIER PLATE CURRENT |
| 7 | METER (SWITCH) | UP (ON) | TOGGLE SWITCH | METER OPERATES TO DISPLAY POWER TRANSFER. PULSER IS DISABLED SO THAT THE RF CAN BE TUNED FOR BEST IMPEDANCE MATCH |
| DOWN (OFF) | METER IS OFF. PULSER IS OPERANTIONAL | |||
| 8 | ALARM ON | ON | TOGGLE SWITCH | AAS ALARM IS OPERATIONAL |
| OFF | OFF | AAS ALARM IS DISABLED | ||
| 9 | AUDIO ALARM (HORN) | OPERATES WHEN RF OUT OF TUNE AND BEING PULSED | ||
| 10 | FLOW METERING VALVE (INSIDE TOP COVER) FACTORY SET | SET AT FACTORY FOR GAS FLOW (INSIDE TOP COVER) RATE TO PROVIDE 200 MICRONS AT 5 PSIG OF OXYGEN | ||
| 11 | TO VACUUM PUMP | VACUUM FITTING PROVIDES CONNECTION TO VACUUM PUMP | ||
| 12 | GAS IN | 1/4" HOSE BARB | PROVIDES CONNECTION FOR INPUT GAS | |
| 13 | PRESS | FITTING FOR OPTIONAL PRESSURE TRANSDUCER | PROVIDES ACCESS FOR PRESSURE TRANSDUCER | |
| 14 | ASB | FUSE | 7AMP SLOW BLOW FUSE, A/C POWER | |
| 15/16 | OSC CNG | TEST POINTS | PROVIDES ACCESS TO POWER AMPLIFIER GRID CURRENT FOR RETURNING GRID DRIVE | |
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