Multi-Layer Resist Pattern Formation Without Overlay Exposure
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Solution Overview
Problem
Conventional pattern forming methods for semiconductor devices require overlay exposure in the lithography process to achieve fine patterns beyond the resolution limit of the exposure apparatus, which is accuracy-dependent on the alignment of the exposure apparatus.
Innovation Solution
A method involving the use of multiple photosensitive layers with different characteristics, where a first and second photosensitive layer, or an intermediate layer, are exposed and developed to form a pattern without the need for overlay exposure, allowing for the formation of patterns finer than the exposure apparatus' resolution limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If overlay exposure is performed in the second lithography process to form fine patterns beyond the resolution limit, then the pattern fineness is improved, but the alignment accuracy dependency increases
Solution Approach 1:
The patent divides the photosensitive material into multiple layers (first photosensitive layer and second photosensitive layer) with different photosensitive characteristics. Each layer responds differently to the exposure light, allowing independent pattern formation without requiring precise overlay alignment. The first layer forms a preliminary pattern while the second layer forms the final fine pattern, segmenting the pattern formation process across layers rather than requiring sequential alignment.
Solution Approach 2:
The patent transitions from a single-layer two-dimensional pattern formation to a multi-layer three-dimensional structure. By stacking photosensitive layers with different characteristics and exposing them simultaneously through a single mask pattern, the system utilizes the vertical dimension (layer stacking) to achieve fine pattern formation without relying on horizontal alignment precision between multiple exposure steps.
2Manufacturing precision
If the lithography process is repeated twice to form fine circuit patterns exceeding the resolution limit, then the pattern resolution is improved, but the process complexity increases
Solution Approach 1:
The patent merges two separate lithography processes into a single exposure step by stacking multiple photosensitive layers with different characteristics. Instead of performing sequential exposures and alignments, both layers are exposed simultaneously through one mask pattern, combining the pattern formation functions into a single operation that reduces process complexity while achieving fine pattern resolution.
Solution Approach 2:
The stacked photosensitive layers serve multiple functions simultaneously: the first layer acts as a preliminary pattern formation layer while the second layer serves as the fine pattern formation layer. This multi-functionality allows a single exposure process to accomplish what would traditionally require two separate lithography steps, reducing both process complexity and the number of equipment operations needed.
3Manufacturing precision
If overlay exposure is performed to achieve fine patterns, then the pattern fineness is improved, but the production time increases
Solution Approach 1:
The first photosensitive layer performs a preliminary pattern formation action during the same exposure step that forms the final fine pattern in the second layer. This preliminary action is embedded within the single exposure process rather than requiring a separate preparatory exposure step, allowing the system to achieve fine pattern fineness without extending the overall production time.
Solution Approach 2:
The patent maintains continuous useful action by performing simultaneous exposure of both photosensitive layers in a single uninterrupted process. Instead of pausing between two separate lithography steps for alignment and re-exposure, the system continuously exposes both layers through one mask pattern, eliminating idle time and maintaining productive action throughout the process.
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
Enables the formation of fine patterns exceeding the resolution limit of the exposure apparatus without the need for overlay exposure, improving pattern accuracy and reducing dependency on alignment accuracy.
Implementation Method 1
forming, on the object, first and second photosensitive layers having different photosensitive characteristics; exposing the first and second photosensitive layers via a pattern
Data Source
AI summary
A pattern forming method includes coating, on a wafer, a negative resist and a positive resist which has a higher sensitivity; exposing the positive resist and the negative resist on the wafer with an image of a line-and-space pattern; and developing the positive resist and the negative resist in a direction parallel to a normal line of a surface of the wafer. A fine pattern, which exceeds the resolution limit of an exposure apparatus, can be formed by using the lithography process without performing the overlay exposure.