OPERATION OF VACUUM COATING UNIT

FAMILIARIZE WITH THE COATING UNIT

GETTING STARTED

ROUGH VACUUM IN THE CHAMBER

BACKING OPERTION

HIGH VACUUM OPERATION

DEPOSITION OF THIN FILM

SHUTTING DOWN THE UNIT

GETTING STARTED

PRE-OPERATIONAL CHECK

Assuming that you have familiarized with the various switches/controls/valves.

Ensure that the valves are closed especially the baffle valve and V1 is in close position.

Gauges switched off.

V1- two way combination valve

V2- high vacuum valve

V3- Chamber air admittance valve

START THE SYSTEM

• Ensure V1 and V2 are closed
• Turn on the mains switch and start the rotary pump.

Turn on the pirani Gauge in GH-1 – It should read 1 x10^-3 mbar in about a minute

ROUGH VACUUM IN THE CHAMBER

• Open air admittance valve (V3) if it is already evacuated.
• Lift the chamber carefully.
• Clean the chamber/base plate thoroughly.
• Load the filament/boat with the required material (evaporant-say aluminum or bismuth).
• Fix the substrates.
• Replace the chamber.
• Turn the valve V1 to roughing slowly.
• Turn on the pirani gauge and select GH-2

Wait till it shows less than 0.05 mbar.

BACKING OPERATION

• Ensure that the valve V2 is closed.
• Turn V1 to backing position slowly. This evacuates the Diffusion Pump. The pressure should fall steadily to less than 0.05 mbar.
• Turn on the water supply.
• Now turn on the diffusion pump by selecting the rotary switch to DP
• The diffusion pump will take about 30 minutes to reach the operating temperature.

The above “backing operation” cycle can be done first before doing the roughing cycle to save time in the sense that while the diffusion pump takes about 30 minutes, the chamber preparation can be done and get it closed after loading filament/evaporant material. To avoid the risk of V2 accidentally opened when the chamber is at atmospheric pressure, we suggest you to do the roughing cycle first.

HIGH VACUUM OPERATION

• Sectio After 30 minutes having waited for the Diffusion pump to be ready:
• If you turn on the Pirani Gauge –GH-2, you will notice that the pressure in the chamber would have increased-why?
• So turn the Valve V1 to roughing again and wait until it is better than 0.05 mbar say in about 5 minutes.
• Turn V1 in backing position again.
• Select GH-1 and wait until it is better than 0.01 mbar
• Now slowly open the high vacuum valve V2.
• Soon the pressure will start falling in the chamber if the gauge GH-2 is selected. Keep the pirani gauge selected in GH-1
• Switch on the Penning Gauge in RNG1 to read the high vacuum in the chamber.

N.B.: sometimes, the Ionization phenomena by which the Penning Gauge works will not initiate as soon as the gauge is switched on. It takes some time to initiate the discharge. So keep it in “ON” position in case it doesn’t initiate immediately.

DEPOSITING A THIN FILM

• Turn on the LT by selecting –HT, RH, LT rotary switch from the front panel. Ensure that the front service doors are closed.
• And turn on the circuit breaker also.

N.B.: If they are not closed properly the safety switches will not enable the Circuit breaker/LT switch

• Slowly turn up the Variac control and observe the evaporation through the front window, when the evaporant is melting.
• When the evaporation is complete, zero the variac control. Switch off the LT and Circuit Breaker switch.

Continue pumping to high vacuum for about 10 more minutes and then close the High vacuum Valve V2.

SHUTTING DOWN THE UNIT

• Turn off the Penning Gauge
• Clsoe high vacuum valve V2
• Switch off the Diffusion pump
• Continue to run the rotary pump in backing position for about 30 minutes.

N.B.: Even when the unit is not in use it is advised to leave the chamber under vacuum at all the time to prevent exposure of the chamber’s interior to atmosphere. So if you have removed the substrates close the chamber again and evacuate it for some time.

• Turn the valve V1 to close position.
• Switch off the rotary pump.
• Close water supply.
• Switch off the mains.