Siloxane Photoresist Upper Layer for Thin-Resist Pattern Stability
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Solution Overview
Problem
As semiconductor devices shrink in size, photolithographic processing faces challenges with tight process windows, resist line collapse, and limited etch budget due to low aspect ratios and increased viscosity of developers, leading to issues like bottom scum and weak contrast.
Innovation Solution
A photoresist composition is used that includes a floating additive polymer forming an upper layer over the photoresist layer, which is selectively exposed to actinic radiation, followed by development and de-scum operations to create precise patterns, enhancing chemical differences and solubility between exposed and unexposed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoresist thickness is reduced to less than 50 nm to prevent line collapse, then pattern stability is improved, but etch budget is insufficient
Solution Approach 1:
The patent introduces a separate hard mask layer distinct from the photoresist layer. The photoresist layer (thickness < 50 nm) provides pattern stability and prevents line collapse, while the hard mask layer provides the necessary etch budget for pattern transfer. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
The patent adds a vertical dimension by introducing a multi-layer structure (photoresist layer + hard mask layer) instead of relying on a single thick photoresist layer. This dimensional approach enables the system to maintain low aspect ratio in the photoresist while providing sufficient etch protection through the combined structure.
2Manufacturing precision
If photoresist thickness is reduced to less than 50 nm to maintain aspect ratio, then aspect ratio control is improved, but bottom scum increases
Solution Approach 1:
The hard mask layer acts as an intermediary between the photoresist layer and the substrate. It provides a protective barrier that prevents bottom scum formation during etching, while allowing the photoresist layer to maintain its thin profile for proper aspect ratio control.
Solution Approach 2:
The hard mask layer is applied beforehand to cushion and protect the substrate from the harmful effects of bottom scum during the etching process. This protective layer prevents the development of bottom scum issues that would otherwise occur with thin photoresist layers.
3Reliability
If photoresist thickness is reduced to less than 50 nm to prevent line collapse, then resist pattern integrity is improved, but contrast and developer viscosity issues worsen
Solution Approach 1:
The patent separates the functions of pattern formation and pattern protection into distinct layers. The thin photoresist layer (< 50 nm) ensures pattern integrity and prevents line collapse, while the hard mask layer compensates for contrast and viscosity issues by providing a stable base for pattern transfer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach maintains pattern integrity and etch budget, reducing line edge roughness and defects, enabling precise pattern transfer into the substrate, even at low thicknesses.
Implementation Method 1
The photoresist layer is selectively exposed to actinic radiation
Implementation Method 2
the floating additive polymer separates from the photoresist, rising to an upper portion of the mixture forming an upper layer comprising the floating additive polymer
Data Source
AI summary
A method of forming a photoresist pattern includes forming an upper layer including a floating additive polymer over a photoresist layer formed on a substrate. The photoresist layer is selectively exposed to actinic radiation. The photoresist layer is developed to form a pattern in the photoresist layer, and the upper layer is removed. The floating additive polymer is a siloxane polymer.