Developer Free Positive Tone Lithography by Thermal Direct Write

Technology

Dewetting of thin films as a positive tone process through a variety of focused laser spike (FLaSK) annealing techniques is a relatively nascent technique and has only really begun to show its potential for development-free positive tone patterning of 1D or, barring overlap, 2D structures. As currently presented, it exists in two distinct forms: (1) patterning of isolated trench-ridge lines near the optical limit, and (2) patterning of subwavelength lines by overlapping the exposures. While capability (2) is more exotic, capability (1) should not be diminished; submicron 2D structures in a method that requires no developer step and only uses inexpensive, commodity polymers, free space optics, and visible (sub watt) lasers could be a potentially competitive process, especially for industrial scale fabrication tools where price is a critical concern.  

Problem Addressed

This system is designed to do 2D patterning via a dewetting mechanism that can reach competitive resolutions with current systems without the need for several key attributes: (1) photosensitive media, (2) post-exposure baking, and (3) development. Step (1) has two distinct implications: (1.i) Polymers for dewetting can be much cheaper than photoresist polymers (lab grade polystyrene is ~$0.20 per gram (which is 2 wt% of the solution) and coating solvent is ~$0.05 per mL compared to ~$2 per mL of a typical photoresist) and (1.ii) lab facilities where photosensitive media are handled often must have dark-room-like environments or exposure limits must be enforced. Step (2) simply reduces the number of steps. Step (3) can be a major cost consideration as labs where development is a necessity require both (3.i) a large supply of fresh developer and also (3.ii) the means to dispose of used developer. Removal of this step could present a large reduction in both the chemical costs and also the environmental footprint of a facility. Beyond equipment companies, companies who do their own in-house patterning, such as those who manufacture photomasks and stamps, could employ this method in a custom system to produce grating structures in a much more affordable fashion.  

Advantages

• Reduced cost and environmental effects
• Highly scalable