An investigation on defect-generation conditions in immersion lithography

Evaporation of water droplets on photoresist surfaces – An experimental study of contact line pinning and evaporation residues

“…Frequently, post-rinsing steps are performed in order to reduce the watermark defect density. 41,63,64 Our results in Fig. 7 show that the evaporation residues may not be completely removed by a short post-rinse step.…”

Defects reduction at BEOL interconnect within 300mm manufacturing environment

“…There appears to be less defect on device #1 & #3 than device #2(a). Bubble, antibubble, blister, watermark (W/M), microbridging defect, non-visible, protrusion, blob, print particle, stain defect, dust, line deformation, and water droplet are several immersion lithography defects that have been studied by several authors [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Out of these experiments, solutions like thicker topcoat, lower PAB, smaller filter pore size, longer developer time, longer rinse time, longer spin dry time, using Nikon Engineering Evaluation Tool (EET), using BF/3D DUV inspection tool, using Dark Field inspection SP2 tool UV laser light, using Defect source analysis (DSA), using Sokudo post developer rinse technique, improving material and rinse composition, using Advance Rinse Process (ADR) rinse process, optimizing rinse cycle time, using filtering system, using "on-the-fly" automatic defect classification (OTF-ADC), using surfactant rinsing, and pumping with filtration stability are all viable solution to further reduce defect at lithography step [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][23][24][25][26]…”

Advances in Patterning Materials for 193 nm Immersion Lithography

“…Despite the inability of the topcoats to prevent water penetration into the resist film, they are an effective means by which to prevent PAG leaching into the immersion fluid. Typically, greater than 90% reduction in the amount of PAG leaching is observed with the use of a topcoat. ,,,,, Interestingly, topcoats are unable to reduce PAG leaching levels in direct proportion to their thickness. ,, In general, PAG leaching with a topcoat is predominantly from the topcoat surface with little PAG diffusion through the topcoat film itself. ,, Analysis of topcoat−resist film stacks reveals that PAG and other resist components can migrate into the topcoat film during casting. ,,,− For certain topcoat−resist pairs, this intermixing layer is substantial (see Figure ) . The intermixing of resist components with the topcoat is strongly dependent on the polarity of the topcoat casting solvent, with alcoholic solvents causing increased intermixing relative to less polar ethereal or hydrocarbon solvents. ,, In addition, the presence of a strong intermixing layer generally results in a region with slower dissolution rate during development, increased surface roughness after development, and T-top formation in the final resist profiles. , …”

“…Drying stains are the result of deposition of contaminants during droplet evaporation and can take the form of a singular island or well-known “coffee stain” patterns depending upon the physics of the droplet drying process . Controlled contamination studies have placed droplets of pure or contaminated water (containing photoacids, PAGs, and base quenchers) on model silicon, resist, and topcoat materials and observed the resultant staining and impact on resist performance. ,,,, Frequently, drying stains from “pure” water droplets are observed even on clean silicon wafers due to dissolved silica or contaminants picked up from the environment such as dust, phthalates, or siloxanes …”

“…If water droplets are left on the resist surface, they can induce so-called watermark defects, which are characterized by regions with t-topped or bridged resist profiles having a generally larger critical dimension (CD) (see Figure ) . The probability of a defect being formed is related to the size and drying time of the droplet, the permeability of the topcoat, and the resist sensitivity to water. ,,, Intense research has endeavored to explain why water droplets on the resist surface cause defects whereas uniform extended soaking of the resist surface does not . Watermark formation has been attributed to an inhibited region at the surface of the chemically amplified resist with little to no base dissolution rate due to a lower degree of deprotection (see Figure ).…”