Double Patterning Resist Process for Lithography Overlay Accuracy
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Solution Overview
Problem
Current double patterning processes in lithography require multiple etchings, leading to reduced throughput and misregistration issues due to pattern deformation and low overlay accuracy, especially when using negative resist materials and thermal flow methods.
Innovation Solution
A pattern forming process involving a first positive resist composition with lactone, acid labile, and carbamate units, followed by heating to generate a base for acid inactivation, and a second resist composition with a C3-C8 alcohol and optional C6-C12 ether solvent, allowing for single dry etching and precise pattern formation without intermixing or deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple etchings are used in double patterning process, then pattern features can be formed with reduced pitch, but throughput is reduced and misregistration issues occur due to pattern deformation
Solution Approach 1:
The patent divides the patterning process into two separate resist coating and exposure steps (first positive resist and second positive resist) that can be performed sequentially without intermediate etching steps. This segmentation allows each resist pattern to be formed independently with high precision, eliminating the cumulative deformation errors that occur with multiple etchings while maintaining the reduced pitch capability through the second resist exposure in the spaces of the first pattern.
Solution Approach 2:
The first positive resist pattern is formed in advance as a stable base layer before applying the second resist. This preliminary pattern formation establishes fixed reference features that guide the subsequent second exposure, ensuring precise overlay and registration without requiring the substrate to undergo deformation-prone etching processes between the two patterning operations.
2Manufacturing precision
If negative resist materials and thermal flow methods are used, then pattern features can be formed, but overlay accuracy is low due to pattern deformation
Solution Approach 1:
The patent inverts the conventional approach by using two positive resist materials instead of negative resist combined with thermal flow methods. This inversion eliminates the need for thermal processing that causes pattern deformation and instability. The second positive resist is exposed in the spaces of the first positive resist pattern, creating complementary features without subjecting the patterns to thermal stress that would degrade overlay accuracy and pattern stability.
Solution Approach 2:
The patent changes the material parameter from negative resist to positive resist for both patterning steps. This parameter change fundamentally alters the chemical and physical behavior of the resist system, eliminating the thermal flow process that causes pattern deformation. The positive resist system maintains stable pattern dimensions throughout the process, ensuring high overlay accuracy between the first and second patterns.
3Stability of the object's composition
If first resist pattern is heated to generate base for acid inactivation, then intermixing between resist films is prevented, but additional process steps are required
Solution Approach 1:
The patent changes the chemical parameter of the first resist by incorporating base-generating units (carbamate or carbonylhydrazone groups) that decompose upon heating to release base and neutralize acid. This chemical parameter change prevents intermixing between the first and second resist films by inactivating the acid that would otherwise cause dissolution of the first pattern during second resist development, thereby preventing the need for additional protective process steps.
Solution Approach 2:
The base-generating units in the first resist act as an intermediary mechanism that chemically neutralizes the acid produced during second resist exposure and development. This intermediary base generation prevents direct interaction (intermixing) between the second resist solvent/developer and the first resist pattern, stabilizing both layers without requiring complex additional process steps such as barrier coatings or extended processing sequences.
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 process enables the formation of precise second resist patterns between features without deforming the first resist pattern, reducing pitch by half and improving throughput by eliminating the need for multiple etchings and enhancing overlay accuracy.
Implementation Method 1
heating the first resist pattern to generate a base for inactivation to acid
Implementation Method 2
recurring units having a carbamate structure... heating the first resist pattern to generate a base for inactivation to acid
Data Source
AI summary
A pattern is formed by coating a first positive resist composition comprising a copolymer comprising lactone-containing recurring units, acid labile group-containing recurring units and carbamate-containing recurring units, and a photoacid generator onto a substrate to form a first resist film, patternwise exposure, PEB, and development to form a first resist pattern, heating the first resist pattern for inactivation to acid, coating a second positive resist composition comprising a C3-C8 alcohol and an optional C6-C12 ether onto the first resist pattern-bearing substrate to form a second resist film, patternwise exposure, PEB, and development to form a second resist pattern.