Double Spacer Method for Small Pitch Pattern Formation
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Solution Overview
Problem
Conventional lithography equipment with longer wavelengths, such as the KrF excimer laser (248 nm), struggles to form small pitch patterns required in modern semiconductor device fabrication due to limitations in resolution accuracy.
Innovation Solution
The method involves depositing double spacer layers on a small line pattern, performing a spacer etch process to form sidewall spacers, and using these spacers as masks for an etch-back process to create three-line patterns, effectively reducing the pitch to one-third of the initial pattern, allowing for the formation of small pitch patterns like 45 nm using conventional lithography equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional lithography equipment with longer wavelength (e.g., KrF excimer laser at 248 nm) is used, then production cost and device complexity are reduced, but manufacturing precision deteriorates due to inability to form small pitch patterns
Solution Approach 1:
The patent applies segmentation by dividing the pattern formation process into multiple stages: first forming initial patterns with conventional lithography, then using double spacer deposition and etching to further subdivide and refine the pitch. This multi-step self-aligned process enables pitch reduction to one-third of the original without requiring higher-resolution lithography equipment, thus maintaining cost advantages while achieving fine pitch patterns.
Solution Approach 2:
The patent transitions from two-dimensional planar patterning to three-dimensional spacer-based patterning. By depositing spacers on the sidewalls of initial patterns and using vertical dimension for pitch control, the method achieves precise pitch definition that is independent of lithography resolution, effectively bypassing the wavelength limitation of conventional lithography equipment.
2Manufacturing precision
If lithography equipment with shorter wavelength (e.g., F2 excimer laser at 153 nm) is used, then manufacturing precision improves for small pitch patterns, but device complexity and production cost increase
Solution Approach 1:
The patent segments the pitch reduction function from the lithography step itself, placing it instead in subsequent spacer deposition and etching steps. This allows conventional lithography equipment to be used for the initial pattern, with the fine pitch definition achieved through self-aligned spacer processes, thereby avoiding the need for complex shorter-wavelength lithography systems.
Solution Approach 2:
The patent introduces spacer layers as intermediary structures that mediate between the initial lithography pattern and the final fine pitch pattern. These spacers serve as self-aligned masks and pattern definition elements, enabling precise pitch control without directly relying on the resolution limits of the lithography equipment.
3Ease of manufacture
If conventional lithography equipment with longer wavelength is used, then ease of manufacture improves, but manufacturing precision deteriorates due to resolution limitations
Solution Approach 1:
The patent performs preliminary patterning with conventional lithography equipment to create initial patterns that serve as templates. These preliminary structures then guide the subsequent spacer deposition and self-aligned etching processes, which achieve the final fine pitch definition. This preliminary action enables the use of readily available equipment while still achieving high-precision results.
Solution Approach 2:
The spacer structures perform multiple functions automatically: they serve as sidewall protection, pattern definition masks, and pitch control elements all in one self-aligned process. This self-service capability eliminates the need for additional alignment steps and complex equipment, allowing conventional lithography tools to achieve advanced patterning results.
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 fabrication of small pitch patterns with a resolution comparable to higher-cost, higher-resolution lithography processes like ArF immersion lithography, using only conventional KrF excimer laser technology, thereby reducing production costs and complexity.
Implementation Method 1
performing a spacer etch process to form sidewall spacers
Implementation Method 2
using these spacers as masks for an etch-back process to create three-line patterns
Data Source
AI summary
A method of forming a small pitch pattern using double spacers is provided. A material layer and first hard masks are used and characterized by a line pattern having a smaller line width than a separation distance between adjacent mask elements. A first spacer layer covering sidewall portions of the first hard mask and a second spacer layer are formed, and spacer-etched, thereby forming a spacer pattern-shaped second hard mask on sidewall portions of the first hard mask. A portion of the first spacer layer between the first hard mask and the second hard mask is selectively removed. The material layer is selectively etched using the first and second hard masks as etch masks, thereby forming the small pitch pattern.