Manufacturing using printing
In the late 1990s, standard semiconductor micro-fabrication techniques were used to manufacture ferro-electric memories, by sputtering and evaporating the electrode materials and patterning the memories using photolithography. While design rules can be very small, and passive array memories with high densities have been shown to work using a hybrid structure, these techniques typically result in a significant fabrication cost.
Recent work has shown that mass production using print techniques can achieve very low cost, as it is an additive process and requires fewer steps and less costly deposition methods. The key enabling attributes are that the devices are solution processable and that the materials can be cured and sintered at low temperature, which allows for use of low cost substrates such as PET and PEN.
Thinfilm memories are currently produced by various print processes. At one of our partners, Inktec ltd in South Korea, silver electrodes are printed using gravure, the polymer memory film is coated using micro-gravure while the protection layer and the carbon pads are printed using rotary screen printing. The carbon contact pads are used to connect the memory cells to external read and write circuitry. The resulting memories as printed on a web of PET are also shown in figure 3 (top). Memories produced by another partner, PolyIC gmbh, are shown in figure 3 (bottom).
Figure 3. PET rolls with printed memories