Scribe Line Alignment Marks Using Spacer Etching
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Solution Overview
Problem
The reduction in feature sizes of circuit components poses challenges for photolithography techniques, as they reach a minimum pitch beyond which they cannot reliably form features, making it difficult to use direct alignment methods for scribe line alignment marks due to the narrow width and large spacing of sub-lithographic pitch multiplied features.
Innovation Solution
The method involves depositing spacer-forming layers with a lateral thickness less than the minimum photolithographic feature size, anisotropically etching them to form sub-lithographic width features, and using these features as alignment marks, which can be viewed and used for direct alignment techniques with dedicated masking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pitch multiplication is used to form sub-lithographic features, then feature size reduction is achieved, but the features become too narrow and spaced too far apart for scanners to view
Solution Approach 1:
The alignment mark is segmented into multiple components: a first feature formed by photolithography and a second feature formed by spacer deposition and anisotropic etching. This segmentation allows the first feature to serve as a visible reference for scanners while the second feature provides the sub-lithographic dimension needed for continued feature size reduction
Solution Approach 2:
The first feature acts as an intermediary between the scanner's optical detection capabilities and the sub-lithographic second feature. The scanner views the first feature to establish alignment, which then indirectly defines the position of the second feature, bridging the gap between detection capabilities and feature size requirements
2Measurement precision
If direct alignment is used for scribe line alignment marks, then alignment accuracy is improved, but it becomes impossible to use when features are sub-lithographic width
Solution Approach 1:
The first feature is formed preliminarily before the second feature using conventional photolithography. This preliminary feature serves as a reference that enables subsequent direct alignment operations, allowing the second sub-lithographic feature to be precisely positioned relative to it through spacer-based self-alignment
Solution Approach 2:
The method changes the parameter of feature width by forming the second feature with a width less than the minimum photolithographic feature dimension. This is achieved by using spacer deposition and anisotropic etching instead of direct photolithography, enabling sub-lithographic dimensions while maintaining alignment capability through the first feature
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 allows for more precise and accurate alignment marks with improved quality and size uniformity, enabling continued feature size reduction and alignment accuracy beyond the limitations of conventional photolithography.
Implementation Method 1
The spacer-forming layers are then anisotropically etched to form sub-lithographic width features
Data Source
AI summary
A method of processing a semiconductor substrate in forming scribe line alignment marks includes forming pitch multiplied non-circuitry features within scribe line area of a semiconductor substrate. Individual of the features, in cross-section, have a maximum width which is less than a minimum photolithographic feature dimension used in lithographically patterning the substrate. Photoresist is deposited over the features. Such is patterned to form photoresist blocks that are individually received between a respective pair of the features in the cross-section. Individual of the features of the respective pairs have a laterally innermost sidewall in the cross-section. Individual of the photoresist blocks have an opposing pair of first pattern edges in the cross-section that are spaced laterally inward of the laterally innermost sidewalls of the respective pair of the features. Individual of the photoresist blocks have an opposing pair of second pattern edges in the cross-section that self-align laterally outward of the first pattern edges to the laterally innermost sidewalls of the features during the patterning.