Abstract
Background: Although the wet cleaning process has been widely used in semiconductor device manufacturing due to its convenience, it faces theoretical limits. That is, when the size of the objected particle is smaller than 100 nm, it is buried in the stagnant layer where there is substantially no fluid flow. Aim: Only small particles below the stagnant layer (<100 nm) is removed without any damage to the fine patterns or substrate: pattern collapse, critical dimension shift, and optical property shift. Approach: Utilizing unique characteristics of water: volume expansion when freezing, solid (ice) is lighter than liquid (water), and particles adhered the substrate is peeled off from the substrate and rise to the water surface along with the surrounding ice. Results: By repeating the cycle of cooling, thawing, and rinsing, polystyrene sphere particle of 80 nm in diameter can be removed with high particle removal efficiency (PRE >90 % ) and no negative influences on the pattern or substrate. Conclusions: A new cleaning method for very small (<100 nm) particles is proposed with high PRE and low damage. This method is thought to be applied to every process if water can infiltrate into the gap between the particles and the substrate.
Highlights
In recent years, the performance of semiconductor devices has improved owing to improvements such as downscaling, introduction of three-dimensional (3D) structures and new materials, and circuit improvement.[1,2,3] For the downscaling process, ArF-immersion (ArF-i) has a resolution limit of ∼40 nm, but the minimum critical dimension (CD) of semiconductor devices is already smaller than that in 2012, but the subsequent downscaling of the devices has continued
The minimum size of semiconductor device is thought to be ∼7 nm, so even if the Extreme ultraviolet (EUV) lithography technology is used, the minimum CD of the semiconductor devices is smaller than its limit
This paper presents a discussion on water infiltration into the small gaps between the substrate and the particle
Summary
The performance of semiconductor devices has improved owing to improvements such as downscaling, introduction of three-dimensional (3D) structures and new materials, and circuit improvement.[1,2,3] For the downscaling process, ArF-immersion (ArF-i) has a resolution limit of ∼40 nm, but the minimum critical dimension (CD) of semiconductor devices is already smaller than that in 2012, but the subsequent downscaling of the devices has continued. Extreme ultraviolet (EUV) lithography was recently introduced with a resolution limit of ∼13 nm for single patterning. The minimum size of semiconductor device is thought to be ∼7 nm, so even if the EUV lithography technology is used, the minimum CD of the semiconductor devices is smaller than its limit. That is, when the size of the objected particle is smaller than 100 nm, it is buried in the stagnant layer where there is substantially no fluid flow
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