Flash Memory Dummy Structures Mitigate Etch Loading
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Solution Overview
Problem
The semiconductor manufacturing process for flash memory faces challenges in achieving a wider process window and reducing manufacturing costs as feature sizes decrease, particularly in forming structures like word lines, select gates, and pick-up neck pairs without encountering etch loading effects, bowling, or short circuitry.
Innovation Solution
A method involving the formation of a patterned dielectric layer with specific regions and spacers, followed by etching processes using mask patterns to create word lines, select gates, and pick-up neck pairs, with a dummy structure placed between them to mitigate etch loading and prevent short circuitry, utilizing a spacer cut-off technique to ensure independent operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If feature sizes are continuously reduced to increase storage capacity, then device integration density is improved, but etch loading effects and manufacturing reliability deteriorate
Solution Approach 1:
The patent introduces a dummy structure in advance before the etching process to compensate for etch loading effects. This preliminary structure is positioned between the word lines and pick-up neck pairs to balance the etch load distribution, preventing bowling and fracture issues that would otherwise occur due to reduced feature sizes.
Solution Approach 2:
The dummy structure is selectively placed only in specific regions where etch loading effects are most problematic - between the word lines and pick-up neck pairs. This localized approach addresses the specific reliability issues in high-density regions without affecting other areas of the device.
2Area of moving object
If feature sizes are continuously reduced to increase storage capacity, then device integration density is improved, but process window deteriorates
Solution Approach 1:
The dummy structure is formed as a preliminary feature before etching to pre-compensate for process variations. By having this compensatory structure in place beforehand, the etching process becomes more predictable and less sensitive to parameter variations, effectively widening the process window.
3Device complexity
If conventional etching processes are used without dummy structures, then manufacturing process is simple, but etch loading effects cause bowling and fracture
Solution Approach 1:
The dummy structure is introduced as an additional preliminary step in the manufacturing process. While this increases process complexity slightly, it dramatically improves etching precision by preventing bowling and fracture, ensuring uniform word line formation across the substrate.
4Device complexity
If spacers are not cut off between word line regions, then manufacturing process is simpler, but short circuitry occurs between adjacent structures
Solution Approach 1:
The spacer material is segmented into separate regions by cutting it between the word line regions. This segmentation creates electrical isolation between adjacent structures, preventing short circuitry while maintaining the structural benefits of spacers during the etching process.
Solution Approach 2:
The spacer cut-off is performed as a preliminary isolation step before final device assembly. By establishing electrical isolation early in the process, subsequent manufacturing steps can proceed without risk of short circuits between adjacent word lines or pick-up neck pairs.
Data Source
AI summary
A method includes: forming a patterned dielectric layer, including a predetermined word line region and a predetermined pick-up neck region being separated by a first distance, and the patterned dielectric layer within the predetermined pick-up neck region has a second distance, wherein the first distance is smaller than or equal to the second distance; forming a spacer on sidewalls of the patterned dielectric layer; cutting off the spacer of a connecting portion of the predetermined word line region from the spacer of a remaining portion of the predetermined word line region; forming a mask pattern, including a first portion across the connecting portion and the predetermined pick-up neck region, wherein the spacer at the remaining portion is spaced apart from the first portion; and forming a dummy structure, word lines, and pick-up necks, wherein the dummy structure is located between the word lines and the pick-up necks.