A conductive MOF gate survives the chemistry needed to pattern it

A copper-based metal–organic framework has been patterned into working transistor gates on three semiconductor platforms. The researchers used the same material with MoS₂, MoTe₂ and IGZO, but achieving useful device behaviour depended on finding an etching sequence that cleared unwanted film without destroying what remained.

A conductive film still has to survive the chemicals used to turn it into a device. Here, residue removal and damage to the retained material pulled the process in different directions.

The team grew Cu₃(C₆O₆)₂ films by chemical vapour deposition, then investigated two etchants with different weaknesses. Ammonium persulfate provided controlled removal but could leave fragments behind. A chromium etchant cleared residues more aggressively, with the risk of removing too much of the film. Using them in sequence allowed the first treatment to establish the pattern and a brief second treatment to finish the clearing.

After processing, the retained film’s structure and electrical conduction were largely preserved. The paper reports roughly 50 nm film thickness and patterned lines around 4.2 μm wide for a nominal 5 μm design. These dimensions put the fabrication result in context: this is a thin film research platform, well before a claim of advanced logic integration.

The attraction of a conductive MOF is the scope to alter its electronic properties through chemistry. The film in this study has a work function of 4.51 eV. Other compositions could potentially shift that value and offer another way to set transistor behaviour, although the present experiments use one composition across the different channels.

The MoS₂ comparison is particularly useful. A platinum gate and a MOF gate controlled the same channel, producing similar threshold voltages and extracted field-effect mobilities. Sharing the channel makes this a stronger comparison than placing two unrelated devices beside one another and attributing every difference to their gate materials.

All 23 transistors in an IGZO array operated after their gates were patterned together. Separate stability checks covered 400 gate-voltage cycles in an IGZO device and roughly a year of ambient storage for a MoS₂ transistor.

Those results establish a processing route and working electrodes. They leave the power claim open: KAIST says voltage reduction and lower power operation are still to be investigated, alongside finer patterning and reproducibility over larger areas. The study appeared in Advanced Materials on 15 September and was described by KAIST on 26 October.

Sources

• Original research: Lithography-Compatible Conductive Metal–Organic Frameworks for Scalable Electronics
• KAIST research release

Image: NASA Glenn semiconductor cleanroom. Archive illustrative photograph. NASA Glenn Research Center. Image source. Public domain (NASA).