This page serves as a tutorial for the PVD-75 sputtering system and an introduction to the control system. At the bottom of this page, a PDF document may be found with the condensed SOP for the unit.

The PVD-75 Deposition system. Custom-built by Kurt J. Lesker, this is a three-target sputtering system with a turbomolecular pumping system, two RF targets and a DC target. It is housed in the class-1000 cleanroom at Niagara College and utilized in both thin-film optical work (e.g. dielectric filters and mirrors) as well as semiconductor work.

System Elements:

This frontal view of the system shown the vacuum chamber on the left (with the touch panel control mounted on the door itself above the viewing window), and the control stack on the right. The control stack consists of two RF generators and one DC generator driving the sputtering targets. The heater control and platen rotation are also found on the control stack. A MAXTEK-360 deposition monitor is also mounted in this stack.

The vacuum chamber, open, revealing three Torus three-inch sputtering guns. The mounting platen for substrates is fixed at the top of the chamber onto the rotating shaft via two pins, the entire plate is rotated by hand until pins are aligned for the platen may be removed for substrate mounting.

At the very top of the chamber are two halogen heating elements as well as the intake for the turbomolecular pump behind the platen.

Substrates, either glass or silicon wafers, are mounted to the 30cm diameter platen via small spring clips. The platen is rotated and the entire plate removed from the chamber, substrates are then mounted under clips as seen here. Once substrates are mounted, the entire platen is returned to the chamber and aligned with mounting pins.

Controls:

Operator control of the vacuum system, gas controller (mass flow), and sputtering gun shutters is via a touchscreen mounted on the door of the vacuum chamber.

In the initial state, at atmosphere, the touchscreen looks like this. The WRG (Wide Range Gauge) display in the center of the display shows a pressure of 650 torr (essentially atmosphere). Of particular interest is the Turbomolecular pump speed set point (TS SP) set to 55% here. Be sure it is set to 100% before beginning the pumpdown sequence. Pumpdown is started by pressing the PUMPDOWN control button.

With pumpdown started, the WRG will show falling chamber pressure and the turbo speed will increase gradually to the set point. When the chamber reaches a terminal pressure of 5*10^-5 torr the display will show 'PUMPDOWN COMPLETE'. At this point adjust the turbo set point to a speed of 50% by pressing the Turbo Speed Set Point (TS SP) button and pressing the INC and DEC buttons which will appear. Notice that the Turbo pump and Roughing pump icons appear green here.

When the pump has been set, press the GAS button (bottom row, third from the left) to enter the gas adjust screen.

From the gas screen set the mode of Mass Flow Controller (MFC) 1 to '2' by pressing the MODE button (circled here) and the INC/DEC buttons as required. Then, adjust the SET POINT pressure (circled, upper left) to 12*10^-3 torr as shown here, again using the INC/DEC buttons to adjust the pressure. Finally, allow gas to flow by pressing the 'GAS' button on the left so that it turns green as seen here.

The actual pressure will be seen on the capacitance manometer (CAPMAN) display in the upper left corner. When the target pressure is reached, press the DEP button (bottom row, second button) to enter the deposition screen.

Controls on the deposition screen allow the user to open shutters capping each sputtering target - Shutter 1 is seen OPEN here.

Chamber pressure (CAPMAN) is also displayed here for convenience.

The RF generator is first set to 12 Watts to light the target. If the target fails to ignite, light the DC target first (#2) with shutter #2 closed (DC targets readily ignite) at a power of 12 Watts - the RF target should readily ignite, then, by proximity. If this fails, quickly open then close the shutter for the RF target. Any deposition will be extremely slow (with a power of only 12 W). Once lit, the power of the RF generator can be SLOWLY ramped from 12 W to the target output of 300 Watts. It should take at least one minute to ramp the power to full output. Ensure the Forward power is correct (304 Watts here) and the Reflected power is under 20 Watts (6 Watts here).

With the power ramped up to full output, and the platen is set to rotate, the appropriate shutter is opened to start the deposition. In a sputtering system, depositions are often timed since the rate of deposit (in units of Angstroms per minute) is relatively constant for a given material at a given power output. Alternately, a Maxtek-360 deposition monitor may be utilized to monitor a deposition in-process.

The chamber is seen here during a deposition of magnesium fluoride - a plume of material emerges from the sputtering target surrounded by a plasma of argon gas.

PDF Document outlining the basic procedures required to operate the PVD-75.

Characterization Runs:

NOTES:

1. The preferred material for optical coatings based on hardness, ease of application, and compatibility with other materials is Silicon Monoxide
2. ZnO is incompatible with some materials and can caused flaking of films from chamber surfaces
3. Contamination of the ZnO target can result in 'flaring' which can result in inconsistencies in deposits
4. DC targets (e.g. Aluminum) favour higher gas pressures (12 mTorr), while RF targets can operate at lower pressures (3 mTorr)
5. Use the DC target at low power levels to 'light' RF targets as required