The evaporation stack holds the OFET source-drain shadow masks (sold separately) and substrates in close contact for thermal evaporation. This is crucial for effective device fabrication as the source-drain channel is usually the most critical feature on an OFET. For use with the and .
Specifications
Size
75 mm x 75 mm
Thickness
1 mm (exc. bolts)
Material
Stainless steel
Capacity
12 substrates
Architecture of an Evaporation Stack
At the base of the system is the shadow mask support which prevents the thin and flexible shadow masks from warping. The shadow masks (sold separately) are then placed on top of the support. Above the shadow mask, the substrate support holds the substrates in alignment with the mask. The lid is used to bolt everything together into a mechanically stable system that can be mounted in a deposition system at any orientation. Finally, a low strength magnetic sheet is placed on top of the lid to pull the shadow mask in close contact with the substrates.
Update: The Evaporation Stack no longer uses a second substrate holder as the additional lower support.
Left: Low density stack shadow mask support (technical drawing). Right: Photo of the low-density-stack evaporation mask support
System Overview
The low density fabrication system has four different masks available (, , and ) to allow the fabrication of devices in any geometry (top/bottom gates and top/bottom source-drain). The diagrams below show the features on each of the individual masks as well as how they fit together on a substrate.
Schematic diagram showing how the different evaporation masks fit together on a device. For back-gate Si/SiO2 substrates, the insulator and gate masks are not required as the gate contacts on the source-drain mask wrap around to contact the central Si layer of the substrate.
The layer order for an FET using the low density evaporation masks.
The layer order for a back-gated FET using Si/SO2 substrates.
Note that silicon oxide substrates do not need a gate mask which simplifies fabrication, however the use of a gate mask with can allow lower operating voltages and lower parasitic capacitance.
Resources and Support
How to load the Low density OFET stack
This video demonstrates how to load the Low density OFET stack typically used to thermally evaporate (vacuum deposit) source-drain contacts. The video shows how to carefully place the evaporation mask on the lower support of the evaporation stack.
