Shallow Trench Isolation Etch Stop Layer for Wordline Depth Control
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Solution Overview
Problem
In shallow trench isolation (STI) processes, the differing depths of wordline trenches between active areas and STI structures lead to parasitic capacitance and increased wire resistance due to varying metal gate depths, causing current leakage and longer wire lengths.
Innovation Solution
A method involving the formation of an oxygen-containing layer, a first isolation layer of set height, and an etch stop layer in the shallow trench, allowing for the etching of wordline trenches with consistent depths across both active areas and STI structures, thereby aligning metal gate heights and reducing parasitic capacitance and wire resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If shallow trench isolation is used to electrically isolate MOSFETs, then area utilization is improved, but wordline trench depth inconsistency occurs between active areas and STI structures
Solution Approach 1:
An etch stop layer is formed on the isolation layer before etching the wordline trenches. This preliminary action ensures that the etching process stops at a predetermined depth, preventing the wordline trenches in the STI structure from being etched deeper than those in the active areas, thus resolving the depth inconsistency problem while maintaining area utilization benefits of STI
Solution Approach 2:
The etch stop layer acts as an intermediary between the isolation layer and the wordline trench etching process. It mediates the etching depth by providing a controlled stopping point, ensuring that the metal gates in both active areas and STI structures are at consistent depths, thereby eliminating parasitic capacitance issues
2Ease of manufacture
If wordline trenches are etched to different depths in active areas and STI structures, then parasitic capacitance increases, but etch selectivity ratio requirements are simplified
Solution Approach 1:
The etch stop layer is formed in advance on the isolation layer to establish a predetermined etching depth limit. This preliminary structure prevents the etching process from creating overly deep wordline trenches in the STI structure, thereby controlling parasitic capacitance while maintaining reasonable etch selectivity ratio requirements
3Manufacturing precision
If metal gates are at different depths in STI and active areas, then current leakage increases, but trench depth control is relaxed
Solution Approach 1:
The etch stop layer serves as a mediator that controls the etching depth to ensure metal gates in both STI and active areas are at the same depth. This intermediary structure prevents current leakage caused by depth differences while maintaining flexible trench depth control through the predetermined etch stop layer position
4Ease of manufacture
If wordline trenches are etched deeper in STI structures, then wire resistance increases, but etch depth control is simplified
Solution Approach 1:
The etch stop layer is formed preliminarily on the isolation layer to establish a maximum etching depth. This preliminary structure prevents excessive etching in the STI structure, thereby controlling wire resistance while maintaining simplified etch depth control through the predetermined stop layer position
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 ensures nearly identical depths of wordline trenches in both active areas and STI structures, improving parasitic capacitance and reducing current leakage while shortening wire lengths to decrease conductive resistance.
Implementation Method 1
forming an oxygen-containing layer on exposed outer surfaces of the shallow trench and the active areas
Implementation Method 2
forming an etch stop layer on an upper surface of the first isolation layer... during the subsequent formation of the WL trenches by etching, the further etching of the WL trenches in the STI structure can be stopped by the etch stop layer
Data Source
AI summary
The present disclosure discloses a semiconductor device manufacturing method and a semiconductor device, relating to the technical field of semiconductors. The method includes: providing a semiconductor substrate, the semiconductor substrate comprising a shallow trench and active areas; forming an oxygen-containing layer on exposed outer surfaces of the shallow trench and the active areas; filling a first isolation layer of a set height in the shallow trench comprising the oxygen-containing layer on its surface, the set height being lower than heights of the active areas; forming an etch stop layer on an upper surface of the first isolation layer; filling a second isolation layer on the etch stop layer in the shallow trench to form a shallow trench isolation (STI) structure; and etching the active areas and the STI structure to form wordline trenches, the bottoms of the wordline trenches in the STI structure are higher than the set height.