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.

Maskless Photolithography – DLP and LCoS

Update 8/26/17: Developing Patterning Process for Homemade Microelectronics

Update 8/14/17: Submicron Maskless Photolithography

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Installation of Varian Navigator TV 141 Turbomolecular Pump

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IMG_9305 IMG_9251Installation of Varian Navigator TV 141 Turbomolecular Pump on a 6″ CF to ISO 100 elbow – custom Lesker part. Pump controller is integrated and is powered by 240v single phase. Backing line is KF16 to KF25 conical adapter and the KF25 stainless hose runs to a heated vapor trap and then to an Edwards oil rotary vane pump. Turbo pump speed is ~120L/s!!