Etch-Selective Layer Footing Reduction in SDDP
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Solution Overview
Problem
In semiconductor integrated circuit manufacturing, particularly in space-defined double patterning (SDDP), the formation of side spacers with conventional methods results in widened footings, leading to critical dimension changes and difficulties in controlling the footing shape, which affects the resolution of patterns smaller than the submicron level.
Innovation Solution
A method involving the use of an etch-selective layer with a lower etch rate than the photoresist, subjected to anisotropic etching with oxygen-containing plasma, followed by atomic layer deposition of a spacer film, to form side spacers that reduce the widened footing and maintain precise dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photoresist pattern is formed by conventional lithography and etching, then the pattern can be created on the substrate, but the footing portion at the bottom of the photoresist protrusion becomes widened, causing critical dimension changes
Solution Approach 1:
The patent applies preliminary trimming action to the photoresist footing portion before the spacer deposition step. By performing the trimming operation in advance, the footing is removed before it can interfere with the subsequent spacer formation process, ensuring that the spacer thickness is determined only by the sidewall profile rather than being influenced by the widened footing.
Solution Approach 2:
The patent extracts or removes the problematic footing portion from the photoresist structure through selective trimming. By separating the footing removal step from the main etching process and applying it specifically to the footing region, the harmful widened footing is eliminated while preserving the intended pattern geometry for spacer formation.
2Shape
If plasma trimming is applied to reduce the footing of the photoresist, then the footing size is reduced, but the footing shape is difficult to control and may be transferred to the underlying layer
Solution Approach 1:
The patent applies local quality by using a trimming mask that selectively covers only the footing portion of the photoresist while leaving the sidewalls exposed. This localized masking approach ensures that trimming occurs only where needed (at the footing) without affecting the critical sidewall regions, thereby controlling the footing shape independently from the overall pattern geometry.
Solution Approach 2:
The patent introduces a trimming mask as an intermediary element between the photoresist and the trimming plasma. This mask serves as a mediator that controls the spatial distribution of the trimming action, allowing precise control over which regions are trimmed while protecting other regions from plasma exposure.
3Shape
If an underlying layer with increased etch rate is used to trim the photoresist, then the footing is reduced, but a mask pattern is formed in the underlying layer which transfers the footing problem
Solution Approach 1:
The patent extracts or removes the footing portion of the photoresist through selective trimming before the spacer formation process. By removing the footing in advance, the source of the transfer problem is eliminated, so even if the underlying layer has different etch characteristics, there is no footing geometry to transfer to it.
Solution Approach 2:
The patent applies preliminary anti-action by removing the problematic footing portion before it can cause harm through transfer to the underlying layer. By performing the trimming operation in advance and selectively targeting only the footing region, the patent prevents the formation of unwanted mask patterns in the underlying layer that would otherwise replicate the footing geometry.
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 effectively reduces the widened footing of the photoresist, allowing for more precise control of critical dimensions and improved patterning resolution below the submicron level by forming side spacers with consistent thickness, thereby enhancing the accuracy of the SDDP process.
Implementation Method 1
anisotropically etching the template in a thickness direction with an oxygen-containing plasma to remove the footing of the photoresist
Implementation Method 2
depositing a spacer film on the template by atomic layer deposition (ALD)
Data Source
AI summary
A method of forming side spacers upwardly extending from a substrate, includes: providing a template constituted by a photoresist formed on and in contact with an etch-selective layer laminated on a substrate; anisotropically etching the template in a thickness direction with an oxygen-containing plasma to remove a footing of the photoresist and an exposed portion of the underlying layer; depositing a spacer film on the template by atomic layer deposition (ALD); and forming side spacers using the spacer film by etching. The etch-selective layer has a substantially lower etch rate than that of the photoresist.