Sub-lithographic Pattern Formation via Sidewall Spacer Removal
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Solution Overview
Problem
Current photolithography techniques face limitations in reducing feature sizes due to minimum pitch constraints, and precise alignment requirements in multi-step lithographic processes can lead to errors in forming integrated circuit patterns, resulting in inoperable circuitry.
Innovation Solution
A method involving two lithographic patterning steps with the formation of sidewall spacers and subsequent removal, allowing for less than 100% precise alignment while maintaining pattern accuracy, enabling the creation of smaller features by using spacer-forming layers and etching techniques to form sub-lithographic features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If photolithography is used to form pattern features, then features can be formed with current technology, but minimum pitch constraints prevent further feature size reduction
Solution Approach 1:
The patent divides the pattern formation process into multiple lithographic steps (first and second lithographic patterning steps) rather than attempting to form all features in a single step. This segmentation allows each step to work within achievable pitch limits while the cumulative effect produces sub-lithographic feature sizes that would be impossible in a single step.
Solution Approach 2:
The patent performs preliminary actions by forming features from the first lithographic patterning step, then forming sidewall spacers on those features before performing the second lithographic patterning step. This preliminary structure creation enables subsequent steps to achieve finer resolution than any single lithographic step could accomplish alone.
2Length of moving object
If two lithographic patterning steps are used to form a single pattern, then sub-lithographic features can be created, but precise alignment is required which increases process complexity and risk of errors
Solution Approach 1:
The patent introduces sidewall spacers as intermediary structures between the first and second lithographic patterning steps. These spacers serve as a physical reference and buffer that facilitates alignment between steps, reducing the stringent alignment precision requirements that would otherwise be necessary for direct multi-step patterning.
Solution Approach 2:
The patent changes the physical and chemical parameters of the spacer-forming layers through selective removal processes. By controlling the composition, thickness, and etch selectivity of spacer layers, the process accommodates alignment variations while maintaining the integrity of the final pattern, thereby reducing sensitivity to alignment errors.
3Length of moving object
If sidewall spacers are formed and then removed to create sub-lithographic features, then smaller features can be achieved, but additional processing steps are required
Solution Approach 1:
The patent merges multiple functions into the sidewall spacer formation process. The spacers simultaneously serve as alignment references for the second lithographic step, as etch masks for defining final features, and as structural templates. This consolidation of functions reduces the number of separate processing steps needed compared to traditional multi-step approaches.
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 enables the formation of smaller features and more dense integrated circuitry by overcoming pitch limitations and alignment challenges, ensuring reliable production of patterned substrates with reduced operational risks.
Implementation Method 1
The spacer-forming layers are commonly anisotropically etched to form sub-lithographic features
Implementation Method 2
photoresist used in photolithography being one example
Data Source
AI summary
A method of forming a pattern on a substrate includes forming spaced first features derived from a first lithographic patterning step. Sidewall spacers are formed on opposing sides of the first features. After forming the sidewall spacers, spaced second features derived from a second lithographic patterning step are formed. At least some of individual of the second features are laterally between and laterally spaced from immediately adjacent of the first features in at least one straight-line vertical cross-section that passes through the first and second features. After the second lithographic patterning step, all of only some of the sidewall spacers in said at least one cross-section is removed.