Etching Solution for Uniform Trench Isolation
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Solution Overview
Problem
The conventional trench isolation structure formation process in semiconductor elements often results in uneven etching rates, leading to defects such as ridges and furrows, which can cause insulation failure and mechanical strength issues due to the difficulty in achieving the required fineness and uniformity in trench isolation.
Innovation Solution
A self-aligned shallow trench isolation process using an etching solution containing hydrofluoric acid and a specific organic solvent with a δH value between 4 to 12, which allows for even etching across trenches of varying widths, reducing the formation of ridges and enhancing insulation and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etching solutions (aqueous hydrofluoric acid or hydrofluoric acid buffer) are used for wet-etching in trench isolation structure formation, then the etching process is simple and easy to implement, but the etching rate becomes uneven across trenches of different widths, leading to ridge formation and structural defects
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by adding organic solvents (isopropyl alcohol, ethyl alcohol, or acetone) to the hydrofluoric acid buffer. This parameter modification alters the etching characteristics, enabling uniform etching rates across trenches of varying widths while preventing ridge formation, thus resolving the contradiction between process simplicity and etching uniformity.
Solution Approach 2:
The patent creates a composite etching solution by combining hydrofluoric acid buffer with organic solvents. This composite formulation leverages the properties of both components: the hydrofluoric acid buffer provides the base etching capability while the organic solvent component enhances penetration and uniformity across different trench geometries, achieving both ease of manufacture and manufacturing precision.
2Adaptability or versatility
If trenches of various widths are etched using conventional methods, then the process can handle different trench sizes, but the material removal becomes uneven, forming ridges and furrows that compromise insulation and mechanical strength
Solution Approach 1:
By modifying the etching solution composition to include organic solvents, the patent achieves uniform material removal across trenches of various widths. This parameter change ensures that both narrow and wide trenches are etched at consistent rates, eliminating ridge and furrow formation, thereby maintaining both adaptability to different trench sizes and reliability of the resulting structure.
3Productivity
If the etching rate at the periphery of narrow trenches is high, then the etching process is efficient, but the center material is left excessive, forming ridges that cause insulation failure and reduce mechanical strength
Solution Approach 1:
The addition of organic solvents to the hydrofluoric acid buffer modifies the etching kinetics, reducing the peripheral etching rate advantage while enhancing center penetration. This parameter change balances the material removal rate across the trench cross-section, maintaining high overall etching efficiency while achieving uniform material removal without ridge formation.
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 proposed process enables the formation of shallow trench isolation structures with fewer defects, achieving excellent insulation and mechanical strength by ensuring uniform etching across trenches of different widths, thereby improving the integration and density of semiconductor elements.
Implementation Method 1
The present invention uses an etching solution that makes it possible to etch equally all the trenches and evenly the material in each trench
Implementation Method 2
uses an etching solution that makes it possible to etch equally all the trenches and evenly the material in each trench
Data Source
Figure 1(a)~1(f)
Figure 2(a)~2(f)
Figure 3
AI summary
The present invention provides an etching solution less affected by trench structures and also provides an isolation structure-formation process employing the solution. The etching solution contains hydrofluoric acid and an organic solvent. The organic solvent has a δH value defined by Hansen solubility parameters in the range of 4 to 12 inclusive and the saturation solubility thereof in water is 5 wt% or more at 20°C. This solution can be adopted instead of known etching solutions used in conventional production processes of semiconductor elements.