CVC Products Electron Beam Evaporator

Trainers

The e-beam is usually used for titanium, chrome, gold, nickel, platinum, aluminum, and copper coatings. It can be used to evaporate most other metals as well. In a typical process the chamber is pumped down to a pressure of 5 x 10^-7 torr to prevent air molecules from interrupting metal atoms as they travel from the evaporation source to the substrate. Then the metal evaporation source is heated to a high temperature by a beam of electrons. This causes the metal to evaporate and be deposited on the substrate. Typical deposition rates range from two to five Å / second.

Features

• can hold up to six separate evaporation sources, making commonly used materials readily available and allowing for evaporation of multiple materials in a single run
• ability to process a variety of sample sizes ranging from 4" wafers to samples that are less than one cm^2
• uses cryo-pump for rapid pump down
• electron beam power is automatically controlled evaporation for uniform evaporation with little operator work
• can process up to 20? <3" samples simultaneously

Overview of Equipment

	Ion Gauge The ion gauge is used to display the chamber pressure when the chamber is under high vacuum. The pressure is measured in torr.
	Valve Controller The valve controller controls the valves that are used to control the chamber pressure. The gauge in the middle of the controller shows the chamber pressure in torr. The lights on the left side of the gauge show the status of the system's valves. A valve is open if the light is on.
	Crucible Selector The crucible selector moves the selected crucible into position for evaporation.
	Power Supply Controller The power supply controller controls the electron beam power supply. The power supply itself is located in the black box on the floor on the right side of the evaporator. Refer to the instructions below when operating the power supply. For more detail on the power supply lights, see the troubleshooting section.
	X Y Sweep The X Y sweep controller controls the position of the electron beam. For proper operation, the beam must move in a circle inside the crucible. The beam should not touch the edges of the crucible.
	Shutter and Hoist Control The shutter control opens and closes the shutter. Ordinarily, the shutter is controlled by the disposition monitor. The shutter is closed while the metal that is being evaporated is being heated. Once the metal is evaporating at the correct rate, the shutter is opened, exposing the sample to the evaporation. Once the desired amount of metal has been deposited, the shutter is closed to prevent further deposition.
	Additional Features 4" wafer holder multi-sample dome back side heater

Operating Instructions

I. Loading the Evaporator

1. Attach the sample to be processed to one of the sample holders that are kept in the dry box near the doorway. Remember that it will be mounted upside down.
2. Just above the view port there are two knobs. The knob on the right controls the viewport block. Turn this knob clockwise until it stops. Now check that there is no glow inside the chamber. A glow indicates that the metal inside the chamber is still hot and the chamber can not be vented until the metal has cooled.
3. Press STOP on the valve controller.
4. Wait five seconds, then press VENT on the valve controller.
5. The system has a sensor so that the hoist can not be raised until the pressure inside the chamber equals atmospheric pressure. When you hear nitrogen exiting the seal, raise the hoise with the HOIST UP button. If you still hear nitrogen entering the chamber, press the STOP button on the valve controller.
6. Inspect each material to be evaporated. You can switch crucibles by pressing the buttons on the crucible selector. Switch to the first material you will be using and make sure that the crucible is centered in the wedge shaped exposure area. If it is not, move the crucible plate to center.

Caution: An overfilled crucible can become jammed in the electron gun and cause serious damage to the gun.

7. Put the sample holder, upside down, into the square holder at the top of the evaporator.
8. Check to be sure the mirror behind the gun is aligned. If the mirror is too close the the crucible, the electron beam will hit it causing it to break. The base of the mirror should be behind the opening in front of the mirror. The electron beam comes through this opening. You will need to be able to see the exposed crucible through the viewing port on the front of the bell jar. Stand in front of the evaporator and look at the mirror from directly in front of it. You should be able to see the exposed crucible.
9. Test the shutter. To do this, switch the shutter control to MANUAL and test it using the OPEN / CLOSE switch. Be sure that the shutter will not hit the mirror. Put the shutter in AUTOMATIC mode when you are done testing.
10. Before pumping the chamber down, it is a good idea to make sure the deposition sensor is working.
11. Look at the bottom of the deposition controller screen. If "XTAL Fail" appears in the display, this means that the sensor crystal needs to be replaced. If this is the case, see the section "Replacing the Sensor Crystal" below.
12. Vacuum around the chamber seal with the cleanroom vacuum. It is very important that you use the soft rubber tip on the vacuum so that the seal area is not scratched. If you can not find the soft rubber tip, contact a MiRC staff member.
13. Lower the hoist by pressing and holding the HOIST DOWN button. You may have to push the bell jar to the side by hand to make it seat properly. Be careful not to put your fingers under the bell jar as it comes down.

Caution: Be certain that there is nothing in the "throat" (the hole in the base of the chamber) before lowering the hoist. Objects such as metal pellets that fall into the throat can destroy the hi-vac valve.

14. Press START on the valve controller to pump the chamber down.

II. Programming the Deposition Controller

1. If the deposition controller is not on, turn it on by pressing the ON / STBY button in the lower right corner of the controller.
2. Press F6 (Program), then F2 (Process Directory). The controller will display a list of materials.
3. You will need to set up each material you are going to use. Use the arrow keys to highlight the material you want to set up.
4. Press F5 (Process). The controller will display the settings for the material.
5. The only settings that you should change are "Final Thickness" and "Thickness Limit." These both should be changed to the desired thickness. To change a setting, use the arrow keys to highlight it. Then enter a new value and press "E."
6. After you have set up the material, press F6 (Process Directory) to return to the list of materials.
7. Set up any other materials you are using the same way.
8. Highlight the first material you are depositing and press F4 (Select Active). This will set it as the active process. The number of the active process is displayed at the top of the screen.
9. Press F6 (Program), then press F6 (Operate).

III. Running the Process

1. The ion gauge will display the chamber pressure. Most people wait until the pressure is in the 5x10^-7 to 2x10^-6 range to start depositing. However, if you are not concerned with deposition quality, you can start at higher pressures. If you want a low pressure it may take 30 - 45 minutes for the system to reach the pressure you want.
2. Turn the keylock on the electron beam controller to ON and press the green ON button next to it.
3. Before proceeding, you must wait for the power supply's cooling fans to reach operating speed. This will take about a minute. The power supply (the big black box beside the evaporator) will make a clicking sound.
4. Press the "HI VOLTAGE" OFF button. This should make the light labeled "AIR/CAB" come on. If the light does not come on, wait a minute and try again.
5. After the "AIR/CAB" light comes on wait about ten seconds, then press the "HI VOLTAGE" ON button.
6. Wait another ten seconds, then press "FILAMENT" ON.

Crucible during evaporation. Note that the brightest glow comes from the metal in the crucible. Only a dim glow should come from the crucible itself.



7. The knobs labeled "Position" and "Amplitude" control the position and amplitude of the motion of the electron beam. The lights above them show the position of the beam. The latitude knobs control the front to back motion and the longitude knobs control the left to right motion. Set both latitude and longitude so that their amplitude is about three lights wide and roughly center them with the position knob. However, if you are going to be depositing gold or any other material which uses a narrow mouthed crucible, the amplitude should be set to one light wide and centered. If you are unsure which type of crucible is being used, contact a MiRC staff member.
8. When you are ready to start, press START on the deposition controller.
9. Look through the viewing port on the front of the bell jar. The beam pattern should be centered in the crucible. (The crucible is the bowl that contains the material being melted.) It should be big enough to heat the metal evenly, but should not touch the crucible itself. (Look at the picture.) If on part of the crucible begins to glow brightly, the beam is hitting it. If you move the beam back to far, it will hit the mirror and break it.
10. After the process is complete, you can deposit another metal by pressing the button for the material on the crucible selector, then selecting F6 (Program), then F2 (Process Directory) on the deposition controller. Highlight the metal you want to evaporate next and press F4 (Select Active). Then press F6 (Operate). Narrow the beam down to a few bars with the X-Y sweep controls and press START on the deposition controller. Align the beam as described in the previous step.

IV. Unloading the Evaporator

1. On the electron beam controller, turn the "FILAMENT," HI VOLTAGE," main power, and keylock off in that order.
2. Wait for the last crucible that was used to stop glowing. If you vent the system while it is still hot, you may destroy the metal.
3. Press STOP on the valve controller.
4. Press VENT on the valve controller.
5. The system has a sensor which will not allow the hoist to be raised until the pressure inside the chamber equals atmospheric pressure. When you hear nitrogen escaping from the seal, raise the hoist with the HOIST UP button. If you can still hear the hiss of the nitrogen entering the system, press the STOP button on the valve controller.
6. Remove your sample from the chamber.
7. When you are finished, vacuum the inside of the chamber with the soft tip on the vacuum.
8. Press and hold HOIST DOWN to lower the hoist.
9. Press START on the valve controller.
10. Return the sample holder to the dry box.
11. Enter this run in the log book.

Replacing the Sensor Crystal

1. Pull the metal ring out of the top of the sensor unit.
2. Pull the metal piece out of the back of the metal ring.
3. Remove the sensor crystal.
4. Put the new sensor crystal in with the white side facing the hole in the metal ring. Extra crystals are in the drawer in the desk on the left side of the filament evaporator.
5. Put the metal piece back into the metal ring so that the contacts are against the patterned side of the crystal.
6. Put the crystal holder assembly back into the sensor head.
7. Throw the old crystal away.