Shallow Trench Isolation Corner Thinning via Developable Material
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Solution Overview
Problem
Shallow trench isolation structures face issues of dislocations and current leakage due to inconsistent compressive stress from liner oxide layers and corner thinning, which are exacerbated by misalignment during photolithography and etching processes.
Innovation Solution
A method involving the formation of a developable material layer to cover the silicon nitride layer, allowing for self-aligned removal of excess material and subsequent corner rounding through thermal processing, thereby alleviating dislocation and leakage issues while avoiding misalignment problems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography and etching are performed to remove silicon nitride layer at top corners, then corner thinning can be addressed, but misalignment occurs causing incomplete or excessive removal
Solution Approach 1:
A developable material layer is introduced as an intermediary between the silicon nitride layer and the etching process. This layer can be selectively removed by chemical development to expose precise corner regions for silicon nitride removal, eliminating the need for photolithographic alignment and achieving accurate corner thinning without misalignment issues
Solution Approach 2:
The mechanical/photographic alignment system (photolithography) is replaced with a chemical development system. The developable material layer responds to chemical development to self-align and define the exact corner regions that need silicon nitride removal, substituting optical alignment with chemical selectivity
2Reliability
If high temperature densification is performed on insulating oxide layer, then isolation quality is improved, but compressive stress causes dislocations at substrate corners
Solution Approach 1:
The silicon nitride layer is deposited conformally over the liner oxide layer before densification. This silicon nitride layer provides preliminary tensile stress that counteracts the compressive stress generated during high-temperature densification of the insulating oxide layer, preventing dislocation formation at substrate corners while maintaining isolation quality
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
The method ensures a thicker oxide layer at the trench corners, reducing dislocations and current leakage, and streamlines the fabrication process by eliminating the need for additional photolithography steps.
Implementation Method 1
Etching back or wet etching is performed to remove a portion of the developable material layer
Implementation Method 2
a thermal process is performed to round the corners for forming a sufficiently thick oxide layer
Data Source
AI summary
A method of fabricating a shallow trench isolation structure is provided. A substrate is provided with a pad layer, a mask layer and a shallow trench formed therein. A liner oxide layer is formed on the sidewall of the shallow trench and then a silicon nitride layer is formed conformably over the substrate. A developable material layer is formed to fill up the shallow trench. After the baking process, a part of the developable material layer is removed until the top surface of the developable material layer is lower than that of the substrate. The silicon nitride layer that is exposed by the developable material layer is removed and the remained developable material layer is removed. Following a thermal oxidation process, an insulating layer is formed over the substrate and fills up the shallow trench. After planarization and removing the mask layer, a shallow trench isolation structure is formed.