Applying drop-on-demand inkjet printing method to maskless lithography

Writing patterns directly on a substrate with liquid droplets generated by Drop-On-Demand (DOD) inkjet devices on a print head provides a maskless, non-contact, low temperature, flexible, and data driven patterning approach. All current ink-jet printing systems are designed specifically for commercial printers and have relatively large droplets and limited numbers of inkjet devices. Therefore, this research focused on building a monolithic inkjet printhead with high resolution and high throughput for maskless lithography applications.; In this thesis, we will first present our theoretical study of the droplet generation conditions on the micron to sub-micron scale. We found that the required actuation pressure increases almost to an inverse proportion to the targeted droplet radius. Using thinner inkjet nozzles, liquids with lower surface tension, and appropriate pressure pulse shapes could make the droplet generation process easier.; Based on our theoretical study and thermal bubble inkjet printing technology, we have designed an inkjet printhead with micron scale droplet resolution. The print head also has the advantages of high operation frequency, small device area, high droplet generation stability, low energy consumption, as well as robust structure.; We have also developed two processes, based on silicon micro-machining technology, to fabricate the designed inkjet print head, including a wafer-wafer bonding process and an original Ge sacrificial structure etching process. The second process is more mature and is capable of forming monolithic print heads with large arrays of inkjet devices and high yield.; The test chips have been observed to generate droplets as small as 2.8mum using a high resolution video imaging system. These droplets are 5 times smaller than those produced by typical inkjet cartridges. We also found that the droplet generation process is stable, with a small droplet trajectory distribution at short droplet flying distance; the micron scale device also has a large operation window for single droplet formation.; Suspensions of gold nano-particles have been used as printing materials for our inkjet device. We have printed Au lines as small as 8mum, the smallest features that have ever been reported by inkjet printing fabrication methods. Installing our printhead into an automatic patterning system allows us to investigate many pattern-formation related issues. Our printhead can also use aqueous nanotube suspensions to realize direct deposition of carbon nano-tubes.; The print head technology developed in our research can then form the basis of a high-throughput maskless lithography system for building micro scale electronic circuits and MEMS devices. In addition, we propose using thin film PZT material and d33 mode actuator to build a piezoelectric inkjet print head, as well as utilizing liquid droplet evaporation to further reduce the droplet size, allowing sub-micron to even deep-submicron scale pattering applications.