Widening Interest in Printing Vertical Transistors

Printed transistors can have the controlled current pass horizontally in the traditional geometry invented forty years ago and used in silicon chips. Alternatively, a vertical geometry can be used, so the channel length is no longer determined by the printing resolution. This gives a smaller transistor that works at higher frequency and is capable of managing higher currents.

 

Cambridge University in the UK has shown how their manufacture can be simplified and ORFID in the USA is commercializing them. However, although Matsushita and many other Japanese companies have researched vertical printed transistors and they are even used in a minority of silicon chips, only a minority of companies in the printed transistor business are developing them, the sticking point being the difficulties of manufacture, which reflects in yield and cost.

 

However, there is some return to the subject and they are even considered interesting for light emitting transistors and OLEDs that incorporate drive transistors. They usually attempt to use organic semiconductors in an attempt to overcome their performance limitations while keeping the benefits such as printability and avoidance of precious metals. These devices are usually referred to as Vertical Field Effect Transistors VFETs or Vertical Organic Field Effect Transistors VOFETs. Potentially, they are therefore a route to such things as driving current driven devices like OLEDs, getting high speed video, circuits that are not embarrassingly large in area and making RFID labels that work at UHF and above. IDTechEx has tracked many patents on the subject, notably from the year 2000 onwards.

 

{Chiba University