Semiconductor Gate Structure with Mandrel for Alignment Shift Tolerance
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Solution Overview
Problem
In semiconductor memory structures, alignment shifting during manufacturing leads to variable distances between large gate patterns and fine gate lines, affecting memory performance and potentially degrading it due to hot carrier breakdown when distances become too short.
Innovation Solution
A semiconductor structure with a gate layer featuring a second portion having appendages along its longitudinal direction, and a first portion with fine gate lines arranged in an array manner, where the appendages and fine gate lines have specific widths and spacings to maintain consistent distance and tolerate alignment shifts, achieved through a method involving cap layers, spacers, and selective etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alignment accuracy is improved, then the distance between large pattern and fine gate lines becomes more consistent, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces a mandrel structure as an intermediary element between the large pattern and fine gate lines. This mandrel serves as a reference structure that defines the spacing, allowing the fine gate lines to be formed at a predetermined distance without requiring high alignment accuracy between separate patterning steps. The mandrel acts as a mediator that transfers the positioning information from the large pattern to the fine gate line formation process.
Solution Approach 2:
The mandrel structure is formed in advance before the fine gate lines are patterned. By pre-forming the mandrel with the desired spacing relationship to the large pattern, the subsequent fine gate line formation can proceed without requiring precise alignment. The preliminary mandrel structure establishes the geometric constraints that ensure consistent spacing regardless of alignment variations in later steps.
2Productivity
If the distance between large pattern and fine gate lines is reduced to increase density, then manufacturing precision requirements increase and alignment shifts cause performance degradation
Solution Approach 1:
The mandrel structure serves as a physical intermediary that enforces a minimum spacing between the large pattern and fine gate lines. By forming the mandrel with controlled dimensions and positioning, the design can achieve higher density while ensuring that the distance between large pattern and fine gate lines never falls below a safe threshold, even with alignment variations.
Solution Approach 2:
The mandrel structure provides a built-in safety margin or 'cushion' against alignment shifts. The mandrel's dimensions and positioning are designed to accommodate expected alignment variations, ensuring that the fine gate lines maintain adequate spacing from the large pattern under normal manufacturing conditions. This beforehand cushioning prevents hot carrier breakdown without requiring ultra-precise alignment.
3Reliability
If the distance between large pattern and fine gate lines varies due to alignment shift, then memory performance degrades due to hot carrier breakdown, but maintaining fixed distance increases process complexity
Solution Approach 1:
The mandrel structure acts as a reference intermediary that defines the spacing geometry. By using the mandrel as the primary reference rather than relying on alignment between separate patterns, the process achieves consistent spacing and reliable memory performance without requiring complex alignment control procedures. The mandrel transfers the spacing definition from the design stage through to the final structure.
Solution Approach 2:
The mandrel structure is self-aligning in the sense that it automatically establishes the correct spacing relationship through its geometric definition in the pattern layout. The mandrel's position and dimensions are designed to automatically ensure proper spacing between large patterns and fine gate lines, without requiring additional alignment measurements or adjustments during manufacturing.
Data Source
AI summary
A semiconductor structure has a second portion with an appendage on one side of the second portion and extruding along the longitudinal direction of the second portion. Moreover the semiconductor structure also has a gate line longitudinally parallel to the second portion, wherein the length of the gate line equals to the longitudinal length of the second portion.