Memory Device Word Line Patterning via Spacer Self-Aligned Double Patterning
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Solution Overview
Problem
The critical dimension uniformity (CDU) of word lines in memory devices is degraded due to the influence of peripheral areas, leading to reduced device performance, as current techniques struggle to accurately control the line-width of word lines adjacent to peripheral areas during the lithography process.
Innovation Solution
A patterning method involving a substrate with distinct areas, where a first mask layer forms sacrificial patterns, followed by spacer formation and removal, and subsequent use of a second mask layer with remaining spacers to define target patterns, ensuring accurate line-width and pitch control without altering the number of photomasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography process is used to define word lines, then the manufacturing process is simple, but the critical dimension uniformity (CDU) of word lines is degraded due to peripheral area influence
Solution Approach 1:
The substrate is divided into a first area (cell area) and a second area (peripheral area), with different mask patterns applied to each area. This segmentation allows the cell area to use spacer self-aligned double patterning for high precision while the peripheral area uses conventional single patterning, thus improving CDU without unnecessarily complicating the entire device structure.
Solution Approach 2:
Different mask patterns are applied to different areas: the first mask layer has first mask patterns in the cell area and second mask patterns in the peripheral area. This local differentiation enables the cell area to achieve better CDU through spacer formation while keeping the peripheral area processing simpler.
2Manufacturing precision
If spacer self-aligned double patterning (SADP) method is used to increase integration level, then the critical dimension control improves, but the line-width of word lines adjacent to peripheral area is still affected and cannot be accurately controlled to target value
Solution Approach 1:
The harmful influence of the peripheral area is extracted and isolated by applying a different mask pattern (second mask patterns) specifically to the peripheral area. This allows the cell area to achieve accurate line-width control through SADP while the peripheral area patterns are designed to minimize their adverse influence on adjacent cell area word lines.
Solution Approach 2:
The mask layer is given different local properties: first mask patterns in the cell area for high-precision spacer self-aligned double patterning, and second mask patterns in the peripheral area designed to reduce dimensional influence on adjacent word lines. This local differentiation resolves the contradiction between achieving high line-width control accuracy and eliminating peripheral area harmful effects.
Data Source
AI summary
A method of forming memory device is provided. A substrate having at least two cell areas and at least one peripheral area between the cell areas is provided. A target layer, a sacrificed layer and a first mask layer having first mask patterns in the cell areas and second mask patterns in the peripheral area are sequentially formed on the substrate. Sacrificed layer is partially removed to form sacrificed patterns by using the first mask layer as a mask. Spacers are formed on sidewalls of the sacrificed patterns. The sacrificed patterns and at least the spacers in the peripheral area are removed. A second mask layer is formed in the cell areas. Target layer is partially removed, using the second mask layer and remaining spacers as a mask, to form word lines in the cell areas and select gates in a portion of cell areas adjacent to the peripheral area.