STI Air-Gap Structure for Uniform Wordline Trench Depth
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Solution Overview
Problem
In shallow trench isolation (STI) processes, the etch selectivity ratio leads to different depths of wordline trenches in active areas and STI structures, causing parasitic capacitance and current leakage due to varying metal gate depths, and increasing wire resistance.
Innovation Solution
A method involving the formation of an oxygen-containing layer, a sacrificial layer of set height, and an etch stop layer in semiconductor substrates to create an air gap within the STI structure, ensuring wordline trenches are etched to a uniform depth, matching those in active areas, and forming a shallow trench isolation structure with an air gap to reduce parasitic capacitance and wire resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional STI process is used without etch stop layer, then manufacturing process is simple, but metal gate depths differ between STI and active areas causing parasitic capacitance and current leakage
Solution Approach 1:
An etch stop layer is formed at a predetermined depth within the STI structure before wordline trench formation. This preliminary layer stops the etching process at the correct depth, ensuring uniform metal gate depths across both STI and active areas, thereby reducing parasitic capacitance and current leakage.
Solution Approach 2:
The etch stop layer acts as an intermediary element between the STI isolation structure and the wordline trenches. It mediates the etching process to achieve precise depth control, enabling uniform metal gate formation without requiring complex process adjustments.
2Manufacturing precision
If deeper etching is used to reach uniform depth, then metal gate depths are uniform, but wire length increases and conductive resistance increases
Solution Approach 1:
The etch stop layer is pre-formed at the optimal depth position before wordline trench etching. This allows the etching process to stop automatically at the correct depth, achieving uniform metal gate depths while preventing excessive etching that would increase wire length and conductive resistance.
3Reliability
If conventional STI without air gap is used, then manufacturing process is simpler, but isolation effect is weaker and parasitic capacitance is higher
Solution Approach 1:
The STI structure is segmented into multiple functional layers: the lower sacrificial layer forms an air gap for enhanced isolation, the etch stop layer controls etching depth, and the upper isolation layer provides electrical insulation. This segmentation achieves superior isolation effect and reduced parasitic capacitance.
Solution Approach 2:
Different regions of the STI structure are given different properties: the lower portion contains an air gap for maximum isolation effect, while the upper portion contains the etch stop layer for precise depth control. This local differentiation optimizes both isolation performance and manufacturing precision.
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 uniform metal gate heights, reduces parasitic capacitance, minimizes current leakage, and shortens wire lengths, thereby enhancing the isolation effect and reducing 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
removing the first sacrificial layer below the etch stop layer to form an air gap
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 isolated from the shallow trench; forming an oxygen-containing layer on exposed outer surfaces of the shallow trench and the active areas; filling a first sacrificial layer of a set height in the shallow trench comprising the oxygen-containing layer on its surface; forming an etch stop layer on an upper surface of the first sacrificial layer; removing the first sacrificial layer below the etch stop layer to form an air gap; filling an isolation layer on the etch stop layer in the shallow trench to form a shallow trench isolation(STI) structure containing the air gap; and etching the active areas and the (STI) structure to form wordline trenches.