Status and future of maskless lithography

For the last 25 years, maskless lithography (ML2) has always been perceived as a promising technology because of its superior resolution and flexibility. However, the very low throughput of ML2 compared to that of optical lithography has prevented it from being used in high volume manufacturing. Consequently, this technology has always been used for niche applications. With ever decreasing critical dimensions (CD), increasing cycle time and escalating mask-set cost, ML2 may become a reliable solution to the following applications:
• device engineering driven by resolution requirements,
• fast and economical product prototyping driven by the cycle time,
• low volume manufacturing driven by the high cost of mask sets.Currently, only single beam tools are used, but worldwide efforts are being carried out in order to develop new tools based on the concept of multi beams (10,000–100,000 beamlets). These tools use photons, high energy electrons (100 kev) or low energy electrons (10 kev). Cost of ownership modelling (COO) was carried to determine the conditions when ML2 approach is more economical than all mask based lithography for prototyping or low volume production. It is assumed that ML2 is applicable for patterning the critical layers only. There exists a business operating case at which a decrease in the mask set expense outweighs an increase in the depreciation cost, which would render utilization of ML2 economically beneficial. The conditions of economically justifiable use of ML2 will be examined.