Sputtering Setup V2

I machined a delrin insulator with fiberglass center rod for the CF 4 pin electrical feedthrough to provide power to the two incandescent substrate heaters in my new sputtering setup and to allow for instrumentation hookup.

New sputtering setup has dual substrate heaters as well as insulated feedthroughs for both target and substrate so that it can operate in DC, RF, Bias sputtering modes, or any combination therein. A quartz microbalance thickness monitor will be added soon.

The second to last image shows multiple colors in glow discharge during sputtering possibly due to DC bias. Bottom and top electrodes are both at different potentials with respect to chamber ground, so it is possible that different gasses are ionized due to differences in ionization energies of the residual gaseous species.

Microwave Plasma Interferometer Prototyping

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Prototyping of a microwave interferometer setup has begun using modified police radar and satellite television parts, namely Gunn Diode oscillators (gunnplexer) and LNBs with dielectric resonant oscillators as well as PLL synthesized ones. Tests are being conducted at X, Ku, and K bands. The goal of this is to non-intrusively measure electron density in plasmas in my chamber. Results of these experiments will be posted.

SEM Sample Preparation – DC Sputtering

Thin films of copper were prepared on non-conductive samples to be observed under the Electron Microscope. This process is called DC Diode Sputtering and took place at just below 100mTorr and 2000v @ 150watts.

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This same setup can be used at lower powers to plasma clean or etch the top layer surface of the sample for better images under the SEM. Oxygen (and sometimes a small amount of Nitrogen) is usually a much more effective gas for this cleaning than Argon and leads to less unwanted sputtering as well.

Sputtering system v2 was made to support DC and RF sputtering so I can make dielectric coatings as well and it supports larger target and substrate samples. An insulator will be constructed to mount the target holder to the main chamber walls so that RF can be used more effectively.

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SEM Demo

Miscellaneous Vacuum Chamber Upgrades

Miscellaneous Upgrades – Vent Valve/TC Gauge CF Tee Construction, Gas Cylinder Holder Fabrication, and Ion Gauge Controller Analog Output Hack

My HP (Granville Phillips)  hot cathode ionization gauge controller (59822b) had provisions for an analog output however the optional connector was not installed on the back panel and the connection points on the main PCB of the controller did not show any voltage deflection proportional to pressure so I took the pressure output from one of the stages in the electrometer which happened to be one of the outputs of a quad opamp chip. This output is fed to a NI DAQ USB6009 and displayed in a LabView VI so that the pressure of the chamber while pumping down can be held constant when requested by PID feedback loop with one or more of the mass flow controllers.

A pressurized gas cylinder holder was designed and fabricated by Diversatech Manufacturing, INC (www.diversatech.com) for safer operation of my vacuum chamber when using gasses such as Oxygen, Nitrogen, or Argon for processes such as sputtering or plasma cleaning.

 

6mhz TTL Oscillator Used as Quartz Microbalance

 

A 6mhz oscillator can was cut up with pliers and the top was removed to expose the quartz crystal. The output is AC coupled (high pass filtered) to the positive (+5v) rail so that a single coax cable can be used to connect this to the thickness monitor as the power is basically just a DC offset on the signal. If you buy a pack of crystals from somewhere like Lesker they will (depending on your thickness monitor) most likely require the usage of an external oscillator. Such a circuit can be made by a complimentary pair or NPN and PNP transistors and couple passive components. Thanks to Ben from Applied Science for the idea.

Abstract: The quartz microbalance is a quick way of monitoring thin film thicknesses in real time, a bare quartz crystal which oscillates at a known frequency is placed in the chamber near the substrate involved in deposition. As the film accumulates on the crystal, it gains mass and the resonant frequency is lowered. The cumulative frequency change is analyzed and interpreted as the rate of accumulation the rate is integrated into a total thickness. Note that accumulation rate is the proper term for deposition rate, as in many cases (sputtering) the actual deposition rate is higher but some atoms are resputtered off the substrate due to high energy molecules in the chamber, substrate temperature, etc. and the total film thickness can momentarily decrease. The net result of the deposition and resputtering is known as accumulation

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+/- 0.1nm resolution!

Custom Flange Block Off Plate Installation

My vacuum chamber which I am setting up for thermal evaporation has a large rectangular flange which has grooves for ISO style clamps and 2 locator pins. This flange may have been used for something like a load lock but as far as I could tell it is not a standard size so a custom block off plate was designed and machined from SS with grooves on the back for clamps, 2 pressed locator pins, and a viton o-ring. Mating surface was hand lapped to ensure good vacuum seal. Made by the extremely talented J.D Guerard machining company.