EUV Lithography Reduced Exposure Dose Negative Tone Development
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Solution Overview
Problem
Current extreme ultraviolet (EUV) lithography methods face limitations in production capacity due to insufficient radiation power and increased line edge roughness (LER) and line width roughness (LWR) with enhanced resist sensitivity, leading to decreased critical dimension uniformity (CDU) and degraded circuit performance.
Innovation Solution
A two-step approach is employed, using a reduced EUV exposure dose followed by negative-tone development (NTD) and a shrinking process to achieve target critical dimensions while reducing LER and LWR, without increasing radiation power or resist sensitivity, utilizing existing EUV equipment and resists.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If resist sensitivity is increased to overcome insufficient EUV radiation power, then productivity is improved, but line edge roughness (LER) and line width roughness (LWR) increase leading to decreased critical dimension uniformity (CDU)
Solution Approach 1:
The patent segments the patterning process into multiple lithography exposures (e.g., main exposure and overlay exposure) with different exposure doses. The main exposure uses a lower dose to reduce LER/LWR, while the overlay exposure compensates to achieve the target pattern dimensions, thereby resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent changes the exposure dose parameter by using a reduced EUV exposure dose (e.g., 5-20 mJ/cm²) compared to conventional doses, and compensates through multiple exposures and negative-tone development. This parameter change reduces LER/LWR while maintaining pattern fidelity, improving both productivity and critical dimension uniformity.
2Manufacturing precision
If conventional EUV lithography methods are used with limited radiation power, then manufacturing precision can be maintained, but productivity is limited due to insufficient radiation power
Solution Approach 1:
The patent employs multiple sequential lithography exposures to accumulate the necessary pattern definition without requiring high single-dose radiation power. This continuous action approach maintains manufacturing precision while improving productivity by utilizing existing lower-power EUV sources more effectively.
Solution Approach 2:
The patent performs a preliminary main exposure at reduced dose to establish the primary pattern with low LER/LWR, followed by additional overlay exposures to complete the pattern definition. This preliminary action allows the use of lower radiation power while achieving the required manufacturing precision through cumulative exposure effects.
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 method effectively enhances EUV lithography productivity by reducing LER and LWR, achieving target critical dimensions with lower radiation power requirements and maintaining circuit performance, while avoiding the need for increased radiation sources or resist sensitivity.
Implementation Method 1
A two-step approach using a reduced EUV exposure dose followed by negative-tone development (NTD)
Data Source
AI summary
A method of lithography patterning includes forming a resist layer over a substrate and providing a radiation with a first exposure dose to define an opening to be formed in the resist layer. The opening is to have a target critical dimension CD1 after developed by a negativ-tone development (NTD) process. The method further includes exposing the resist layer to the radiation with a second exposure dose less than the first exposure dose and developing the resist layer in a negative-tone development process to remove unexposed portions of the resist layer, resulting in an opening between resist patterns. A critical dimension CD2 of the opening is greater than CD1 by a delta. The method further includes forming an interfacial layer on sidewalls of the resist patterns. The interfacial layer has a thickness that is substantially equal to half of the delta.