AJA systems

07-Apr-2014:This is the wikipedia page for the 2 AJA systems located on the 2nd floor room D218. The system is maintained by the technical staff: Shiv, Claus and Nader. Willy and Morten K are the Czars/super users. Contact Shiv for technical questions and basic training. Contact Willy or Morten if you can't get hold of Shiv.

Captain's log Stardate 43125.8:

• 01-Mar-2014: AJA1 was opened up and the alignment was adjusted. To load/unload:
  • Rotate the stage till the permanent mark around 270
  • Tighten the brass knob until the permanent markers meet
  • Load/Unload! The loading should be smooth enough to push the pins in with two fingers. If you force it, you are directly responsible for pushing the stage out of alignment.

Systems 1 and 2 are identical in terms of operating procedures. Password for logging in is 'apex' (no quotation marks). They differ slightly in their outfitting:

• System 1: Two DC sputtering targets, heater in sample mount and Kaufmann ion source for cleaning.
• System 2: One DC sputtering target, one RF sputtering target and an RF supply to substrate. No heater and no Kaufmann ion source, can produce RF plasma (see details below)
  

Remember to use the AJA log sheet (located on the desktop of both machines) every time you use the machinery! Messages from the ansvarlige will be highlighted in orange in the excel file.

Here are some instructions for using the AJAs (thanks to Susan Watson for writing these down).

System 1

This system is expected to at least reach a vacuum of about 1.0x10^(-7)Torr after pumping for 24 hours on main chamber.

Current materials loaded:

1	2	3	4	5	6	DC 1	DC 2
Cr	(empty)	SiO2	Pd	Ti	Au	Ti	Nb

Using the Kaufman ion source

To utilize the ion milling, rotate your sample to point towards the Kaufman source and power it on. In some cases it is beneficial to have your sample at an angle and/or rotate the sample while milling. The figure below shows how to use the software on the control computer to turn on the ion flow.

The software settings on the control computer to enable the ion source. Click in the order indicated.

When operating normally, the chamber should light a clear whiteish hue, and the kaufman power source should read numbers similar to these:

Approximate standard values on power supply when running the milling

You have to time the milling 'by hand', i.e. use a stopwatch. To turn of the ion source simply reverse the steps outlined in the above figure.

Miscellaneous notes / values for milling

Please update this list with good tips / mill rates for materials:

• The approximate mill rate for InSb heterostructure is 15 nm/min. It is advised to tilt the sample to 30 degrees and use 30 speed on the rotating engine. This gives a cleaner and more smooth surface.

• Photolith AZ1505 millrate is approximately 15nm/min (at angle 30 degrees and rot speed 30).

• The optimum milling time for making superconducting contact to InSb nanowires at Harvard was 30 seconds (at 300 V, 13 (?) mA). We tried various things, like milling straight on for 10 seconds, and milling at 45 degrees on both sides of the wire for 10 seconds each, but the total time is the most important thing. Too much and you destroy the wire, too little and contact is bad. There was some variability in the optimum time over a period of 6 months, so don't assume the recipe will be constant.

• The beam current density depends on the beam voltage, beam current and the accelerator voltage. Profiles of the dependence can be found in the ion source manual supplement, which can be found here: File:KDC40 4cm DCS Sup Micro Moly V2.pdf. For example, for a beam current density of 0.14mA/cm^2 with 150V beam voltage, Kaufman recommends a beam current of 17 mA with a 300mV accelerator voltage.

• As of 6-11-2013 the ion source needs to be warmed up before use. If you experience variable result when contacting (!!) or a power law like law for your experimentally determined milling rate it means that you were using the ion source when it was still ramping up the emission ( 46 mAmps is the default values and it takes 3 minutes to reach it).

Milling rates

Here are some approximate milling rates measured for AJA 1 at 300V:

	SiO2	PMMA	Al/AlOx	Al2O3 (ALD)	Gold	User
1 min	3 nm	23 nm	3 nm			Nino
1:30 min				3.5 nm		Merlin
1:30 min - 30° + rot.				2.0 nm		Merlin
2:30 min				5 nm		Merlin
3 min	8 nm	55 nm	8 nm			Nino
6 min	15 nm			9 nm	42 nm	Anders J
8 min - 30° + rot.				31.5nm		Merlin
2 min (Fil. warmed up before)	9 nm					Rawa/Shiv
5 min (Fil. warmed up before)	25 nm					Rawa/Shiv

Using the sputtering system

Because of the software upgrade on system 1, when the system was moved from harvard to cph, the old recipes from harvard no longer work.

Anders has made a .pdf of many of the old recipes. If you want to use any, you need to type them in by hand. The .pdf can be found here: AJA sputtering processes.pdf

Using the heater

As of today (2/11/2013) the heater is broken, at max it goes up to 50 and then sops heating. Willy is working on this.

System 2

This system is expected to at least reach a vacuum of about 8.0x10^(-8)Torr after pumping for 24 hours on main chamber.

For safe operation of the rf ALWAYS enter a ramp rate such that the rf circuitry never ramps faster than 1W/second. Enter ramp rate BEFORE changing wattage!

Current materials loaded:

1	2	3	4	5	6	RF 2	DC 1
Al	Pt	Ge	Au	Cr	SiO2	Ti	Nb

The mirror is a piece of Si/SiO2 wafer (150nm).

Igniting plasma using RF

The RF plasma can be ignited using the following guidelines:

• Argon: 80sccm, set cryopump valve controller to pressure mode and set pressure to 30mTorr. The RF1 (stage) should be set to 25 and RF2 (sputtering target) set to 50. Once the plasma ignites, the pressure can be lowered to 3mTorr. Check that the plasma is visible (a faint purple blueish hue inside the main chamber). There is a little pink indicator in the software that should light up in the control software congruent with when the plasma is visible in the chamber. Remember to check that the power is on for the RF circuitry!

Purchasing

Materials for evaporation can be bought from many sources, e.g.

• http://www.espimetals.com/index.php
• http://www.lesker.com/newweb/index.cfm
• http://www.ajaint.com/

The boats we use approximately take 50g of material. Material should be high purity (about 3-4N ~ 9.999% purity). Preferably buy nuggets or pellets, sizes 1/8" ~ 3-6mm in size.

For ordering of copper gaskets:

• http://www.n-c.com/CatalogSet.aspx?p=UHV_Flanges_%26_Fittings.CF_Flanges_Fittings_%26_Hardware.Hardware_%26_Accessories.Seal_Components&set=Seal_Components&i=06FCF04

Type: G-1650 16.5" OD CF Copper Gasket, Package of 1

Maintenance

The standard configurations on the systems are:

File:Configuration system1.jpg

Configuration settings on system 1

File:Configuration system2.jpg

Configuration settings on system 2

If you are unable to ignite the plasma (either dc, rf or ion plasma) start by checking for shorts between pins on the powersupply input on the sputtering arm / ion source.

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