Sub-Lithographic Pitch Formation via Spacer Densification
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Solution Overview
Problem
Photolithographic techniques face a limitation in feature size reduction due to minimum pitch constraints, which restrict further miniaturization of integrated circuits.
Innovation Solution
The method involves forming spacer-forming layers with a total lateral thickness less than the minimum photolithographic feature size, followed by anisotropic etching and densification of materials to create void spaces, allowing for pitch multiplication and sub-lithographic feature formation without etching the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithographic techniques are used to form patterns, then manufacturing process is well-established and reliable, but minimum pitch constraints prevent further feature size reduction
Solution Approach 1:
The pattern formation process is divided into multiple stages: first forming mandrels at relaxed pitch, then depositing spacer material, selectively removing mandrels, and repeating the process. This segmentation allows each stage to operate at optimal conditions, achieving sub-lithographic pitch while maintaining reliability.
Solution Approach 2:
Spacer material is deposited and prepared in advance before final pattern transfer. The spacer material is pre-formed with controlled thickness and properties, allowing precise pitch control in subsequent steps without requiring direct lithographic patterning at the final pitch.
2Manufacturing precision
If pitch doubling or multiplication techniques are used, then feature size reduction is achieved, but process complexity increases
Solution Approach 1:
The spacer material serves multiple functions: it defines the final pattern pitch, acts as a protective layer during mandrel removal, and can be selectively etched or retained based on process requirements. This multi-functionality reduces the need for separate dedicated layers and steps.
Solution Approach 2:
The spacer material self-aligns to the mandrel features through conformal deposition, automatically establishing the correct pitch relationship without requiring additional alignment steps. The material's own deposition properties enable precise positioning.
3Ease of manufacture
If conventional photolithography is used, then process is simple and well-established, but it cannot form features below minimum pitch
Solution Approach 1:
Mandrel structures serve as intermediary elements that are easier to form with conventional lithography. These mandrels mediate the pattern transfer process, allowing the final sub-lithographic features to be defined by spacer deposition rather than direct lithographic exposure.
Solution Approach 2:
The process transitions from direct lithographic parameter control (wavelength, numerical aperture) to material parameter control (spacer thickness, deposition conformality). This parameter change enables pitch control below the lithographic diffraction limit.
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 features with reduced pitch, overcoming the limitations of conventional photolithography and enabling smaller, denser integrated circuitry by creating void spaces through material densification and volume change without substrate etching.
Implementation Method 1
heat treating a coating layer to effect shrinkage of the layer and simultaneously shrinking an underlying patterned resist layer
Implementation Method 2
chemical shrinking in '0.1 μm level contact hole pattern formation with KrF lithography by resolution enhancement lithography assisted by chemical shrink (RELACS)'
Data Source
Figure 1~2
Figure 3
Figure 4~7
AI summary
A method of forming a pattern on a substrate includes forming spaced first features over a substrate. The spaced first features have opposing lateral sidewalls. Material is formed onto the opposing lateral sidewalls of the spaced first features. That portion of such material which is received against each of the opposing lateral sidewalls is of different composition from composition of each of the opposing lateral sidewalls. At least one of such portion of the material and the spaced first features is densified to move the at least one laterally away from the other of the at least one to form a void space between each of the opposing lateral sidewalls and such portion of the material.