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CHA Resistive Evaporator Operation Manual

Tool Description:

The CHA SEC-600 resistive evaporator is used to deposit aluminum on four inch silicon wafers. The chamber is pumped in two stages with a mechanical roughing pump, followed by a high vacuum CTI-8 Cryogenic pump. The system typically reaches the 10^-7 Torr range.

The chamber has a single flash evaporation source, and is dedicated for aluminum deposition. A carbon heating element (or boat) is resistively heated as the load on the secondary coil of a transformer. Aluminum wire is metered onto the hot boat where it is vaporized. The vapor is then condenses on the wafers and walls of the bell jar.

The planetary holds up to fifteen four inch wafers in three domes held by a "spider". The curved domes are positioned to lay along the surface of the eight inch diameter sphere. Each of the three domes rests on a water cooled ring. The ring is used to prevent overheating the wafers, and allows friction to turn the domes when as the spider rotates. A triangular support on the top of the spider conncets to a feed through in the top of the bell jar to rotate the spider. As the spider rotates the wafers move from the bottom of the planetary to the top and back again.

Two of the planetary domes are loaded from the back. This places the wafers tangent to the sphere, where the angle of incidence of the aluminum vapor is held relatively constant. These domes are used for wafers with the liftoff technique. The third dome holds the wafers with springs at an angle to the sphere where the aluminum vapor angle of incidence varies greatly as the spider rotates. This dome is used for conformal coverage over steps on the wafer.

This chamber is designated for teaching the EEC 146A, 146B, and 246 laboratory classes, and projects involving those classes have first priority. If the system is idle, you may schedule time on the unit. But the evaporator must be kept free of any substance that would contaminate it for the CMOS processes involved in those labs.

Idle state:

The idle state of the evaporator should be as follows:

The bell jar lowered, and under vacuum
On the Auto-Tech II controller:
1. Knob should be pointed at the lighted AUTOMATIC button.
2. The HI-VAC and AUTOMATIC lamps should be lighted, all others are extiquished.
3. Cycle switch should be in START.
4. All MANUAL CONTROL rocker switches (ROUGH , FORE, HI-VAC, and VENT ) should be off.
Both ion gauges off
On the Granville-Phillips 260 guage controller:
1. The POWER light should be on.
2. The FILAMENT and DEGAS lights should be off.
3. The CHAMBER-FORE switch should be in CHAMBER.
4. The CHAMBER-HI-VAC switch should be in CHAMBER.
5. The EMMISION switch should be set to 1.
6. The RANGE 10^-N switch should be set 4.
Power supply off
On the Heater control panel:
1. The POWER lamp should be extiquished.
2. The VACUUM and WATER lamps should be lighted.
3. The main breaker should be off.
4. The AUTO-MANUAL rocker switch should be in MANUAL.
5. The voltage control switch should be at 0-200A 0-50V.
6. The voltage control potentiometer should be fully counterclockwise.
7. The VOLTAGE-DEPOSITION CURRENT switch should be set to VOLTAGE.
Mechanical and Cryo pumps running
On the front panel:
1. The CRYO PUMP breaker should be ON.
2. The MECHANICAL PUMP breaker should be ON.
3. The HOIST RAISE/LOWER switch should be in neutral.
The planetary should be idle
On the Rotary Motor control panel:
1. The indicating lamp should be off.
2. The OFF-LO-HI slide switch should be OFF.
3. The FWD-BRAKE-REV rotary switch should be in BRAKE.
4. The LO-HI potentiometer should be in fully counterclockwise in LO.
the Wire feed system should be idle
On the Wire Feeder Motor control panel:
1. The indicating lamp should be off.
2. The OFF-LO-HI slide switch should be OFF.
3. The FWD-BRAKE-REV rotary switch should be in BRAKE.
4. The SLOW-FAST potentiometer should be pointed at the mark on the panel.

Loading samples and pumping down:

Vent and Open the bell jar.
1. On the Granville Philips 260 gauge controller, turn off ion gauge controller by pressing the Lighted FILAMENT button the light should go off. Turn the RANGE 10^-N knob to 4.
2. Move the VENT-STANDBY-START rocker switch on the AUTO-TECH II controller to VENT through STANDBY.
3. When the chamber pressure reads atmospheric on the Granville- Phillips 260 and the VACUUM lamp on the heater control panel goes out, move the HOIST switch on the front panel to RAISE. The bell jar should rise.
4. Move the VENT-STANDBY-START rocker switch on the AUTO-TECH II controller to STANDBY. This will turn off the vent valve, and conserve nitrogen.
Load your samples in the chamber.
1. When the chamber is open, remove the spider assembly with the three domes from the track. Flip the spider up-side-down, and load your wafers. The domes are not be removed from the spider except for maintanence.
  There are two types of wafer holders. One type places the wafers flush with the planetary hemisphere for shadow masking processes such as lift-off (2 planetaries - 10 wafer locations total) and the other holds the wafers at approximately a 45 degree angle to the planetary hemisphere (1 planetary - 5 locations total) for producing conformal coatings over surface features.
2. After loading your wafers, put the spider back in the chamber. All three domes should be resting on the cooling ring, inside the lip, and the spider should turn freely.
Lower the bell jar and pump down the system.
1. Wipe any dirt or dust away from the baseplate where the bell jar sits with a clean wipe wetted with isopropanal.
2. Lower the bell jar by moving the HOIST switch on the front panel to LOWER. Keep alert for anything that the might get between the bell jar and the baseplate to prevent a good seal.
3. When the bell jar is down, move the VENT-STANDBY-START rocker switch on the AUTO-TECH II controller to START. The controller will operate the valves automatically to pump down the chamber.
  After a few seconds the ROUGHING lamp will light, and the chamber pressure will drop as monitored by the meter under the CHAMBER-FORE switch. When the pressure gets to about 150 mTORR, the AUTO-TECH II will shut the ROUGHING valve (and extiquish its lamp) and open the HI-VAC valve (and light its lamp).
4. When the HI-VAC valve is open as indicated by the HI-VAC lamp, turn on the ion gauge filamant. Press the FILAMENT button on the Granville Phillips controller. If you do not have the RANGE 10^-N switch to 4, the controller might shut off the filament because the pressure is too high for your scale. If this happens, go to a higher scale (lower number) and try again. As the Cryogenic pump drops the system pressure, you can change the scale. When the chamber pressure is below 5x10^-6 evaporation may begin.

Deposition:

When the chamber is less than 5x10^-6 torr, you may begin deposition.
Start wafer rotation on the rotary motor control panel
1. Turn the LO-HI control potentiometer fully counterclockwise.
2. Slide the OFF-LO-HIswitch to LO. The indication lamp should light.
3. Turn the FWD-BRAKE-REV to REV.
4. Increase the LO-HI control potentiometer to the mark
Start heating the boat using the Heater Control Panel
1. Place the AUTO/MANUAL switch is in MANUAL.
2. Turn the Breaker ON.
3. Verify the POWER, VACUUM, and WATER lamps are lit.
4. Set the selector switch to 200A/50V.
5. Raise the filament current slowly to 200Amps with the potentiometer.
Start supply aluminum wire the WIRE FEEDER MOTOR CONTROL panel
1. Slide the OFF-LO-HI switch to LO. The indication lamp should light.
2. Turn the FWD-BRAKE-REV to FWD.
3. Leave the SLOW-FAST potentiometer at the mark on the panel.
Open the shutter with the by moving the MANUAL-OFF-AUTO switch to MANUAL. The OPEN lamp should light, and the planetary can be seen in the view port. You should monitor the time it takes to do your deposition, since there is no rate monitor attached to the system.
When your deposition is done, close the shutter by moving the MANUAL-OFF-AUTO switch to OFF (The AUTO position is for cryo purging, and should not be used)
Stop the wire feed on the WIRE FEEDER MOTOR CONTROL panel
1. Turn the FWD-BRAKE-REV to BRAKE
2. Slide the OFF-LO-HI switch to OFF. The indication lamp should go out.
3. Leave the SLOW-FAST potentiometer at the mark on the panel
Turn off power to the boat heater on the Heater Control Panel
1. Slowly lower the filament current to 0 Amps with the potentiometer.
2. Turn the Breaker OFF.
Stop the planetary rotation on the rotary motor control panel
1. Rotate the LO-HI potentiometer to fully counterclockwise. LO
2. Turn the FWD-BRAKE-REV to BRAKE.
3. Slide the OFF-LO-HI switch to OFF. The indicating lamp should go out.

Removing samples and shutting down the system:

After the deposition is finished let the chamber cool for 10-15 minutes. This is to prevent exposing the hot boat and the film on your wafers to oxygen in the air during the vent. Since all the things are in a vacuum there is very little convective cooling, and it must all be done by conduction through small areas.
Vent and Open the bell jar.
1. On the Granville Philips 260 gauge controller, turn off ion gauge controller by pressing the Lighted FILAMENT button the light should go off. Turn the RANGE 10^-N knob to 4.
2. Move the VENT-STANDBY-START rocker switch on the AUTO-TECH II controller to VENT through STANDBY.
3. When the chamber pressure reads atmospheric on the Granville- Phillips 260 and the VACUUM lamp on the heater control panel goes out, move the HOIST switch on the front panel to RAISE. The bell jar should rise.
4. Move the VENT-STANDBY-START rocker switch on the AUTO-TECH II controller to STANDBY. This will turn off the vent valve, and conserve nitrogen.
Remove your samples from the chamber.
1. When the chamber is open, remove the spider assembly with the three domes from the track. Flip the spider up-side-down, and remove your wafers.
2. After removing your wafers, put the spider back in the chamber. All three domes should be resting on the cooling ring, inside the lip, and the spider should turn freely.
Lower the bell jar and pump down the system.
1. Wipe any dirt or dust away from the baseplate where the bell jar sits with a clean wipe wetted with isopropanal.
2. Lower the bell jar by moving the HOIST switch on the front panel to LOWER. Keep alert for anything that the might get between the bell jar and the baseplate to prevent a good seal.
3. When the bell jar is down, move the VENT-STANDBY-START rocker switch on the AUTO-TECH II controller to START. The controller will operate the valves automatically to pump down the chamber.
  After a few seconds the ROUGHING lamp will light, and the chamber pressure will drop as monitored by the meter under the CHAMBER-FORE switch. When the pressure gets to about 150 mTORR, the AUTO-TECH II will shut the ROUGHING valve (and extiquish its lamp) and open the HI-VAC valve (and light its lamp).
4. Verify that the HI-VAC valve is open by observing the HI-VAC lamp is lit. Leave the Ion Gauge FILAMENT off.