Crosshatch Patterning for Sub-Lithographic Semiconductor Features
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Solution Overview
Problem
Current lithographic techniques have limitations in achieving smaller feature sizes and higher integration densities in semiconductor processing, as they are constrained by minimum capable feature sizes, hindering the formation of highly-integrated circuitry such as DRAM and NAND memory arrays.
Innovation Solution
The method involves forming a grid pattern by overlaying a second series of lines across a first series of lines to create a crosshatch pattern, using selectively etchable materials and processes like photolithography and plasma etching to achieve sub-lithographic feature sizes, which are then used to fabricate highly-integrated circuitry by extending the pattern into underlying materials and forming openings that expose regions for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic techniques are used, then manufacturing simplicity is maintained, but feature size reduction and integration density are limited by minimum capable feature sizes
Solution Approach 1:
The patterning process is divided into multiple sequential steps: forming first lines at a first pitch, forming second lines at a different orientation to create a crosshatch pattern, and using these as masks for subsequent etching. This segmentation allows achieving sub-lithographic pitch multiplication (e.g., 2x or 4x density) while managing complexity through structured process stages
Solution Approach 2:
The patent transitions from two-dimensional planar patterning to three-dimensional vertical structures by forming lines extending into the substrate and creating overlapping patterns at different orientations. This dimensional approach enables pitch multiplication by utilizing vertical depth and angular relationships rather than relying solely on lateral resolution
2Productivity
If pitch multiplication is implemented to achieve sub-lithographic features, then integration density increases, but process complexity and manufacturing difficulty increase
Solution Approach 1:
The method performs preliminary patterning actions by first forming lines of material at controlled pitches and orientations before the final etching step. These pre-formed lines serve as self-aligned masks that define the subsequent pattern, ensuring precise sub-lithographic feature formation without requiring direct lithographic patterning at the final pitch
Solution Approach 2:
The patent utilizes parameter changes in material properties (selective etchability between different materials) and process conditions (anisotropic vs. isotropic etching) to achieve pattern transfer. By changing etch selectivity parameters and directional etching parameters, the process achieves high precision pattern formation through material property differentiation rather than relying solely on lithographic resolution
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 creation of higher density integrated circuit patterns beyond conventional lithographic limits, allowing for the fabrication of more compact and densely integrated semiconductor structures, such as DRAM and NAND memory arrays, by reducing the pitch and achieving sub-lithographic feature sizes.
Implementation Method 1
The material may be anisotropically etched to form the sub-lithographic features
Implementation Method 2
Lithographic processes, such as photolithography, are commonly utilized during semiconductor processing
Data Source
AI summary
Some embodiments include methods of forming a pattern. First lines are formed over a first material, and second lines are formed over the first lines. The first and second lines form a crosshatch pattern. The first openings are extended through the first material. Portions of the first lines that are not covered by the second lines are removed to pattern the first lines into segments. The second lines are removed to uncover the segments. Masking material is formed between the segments. The segments are removed to form second openings that extend through the masking material to the first material. The second openings are extended through the first material. The masking material is removed to leave a patterned mask comprising the first material having the first and second openings therein. In some embodiments, spacers may be formed along the first and second lines to narrow the openings in the crosshatch pattern.