Selective Oxide Trench Etching Without Damaging Self-Aligned Contacts
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Solution Overview
Problem
The challenge in semiconductor manufacturing is forming trenches in inter-layer dielectric layers with high aspect ratios while minimizing damage to self-aligned contacts and spacer layers, which are crucial for preventing contact-to-gate shorts and maintaining structural integrity.
Innovation Solution
A plasma-less etching process using an etchant composition with high selectivity, comprising a hydrogen halide and a nitrogen-containing compound, is employed to etch silicon oxide dielectric layers, ensuring minimal loss or damage to silicon nitride-based features like self-aligned contacts and spacer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plasma etching process is used to form trenches in the ILD layer, then the trench formation efficiency is improved, but the self-aligned contacts and cap layers may be damaged
Solution Approach 1:
The patent changes the etching process parameters by switching from plasma etching to a chemical etching process using a specific etchant composition. This composition contains hydrofluoric acid at a controlled concentration (0.1-10%) combined with other chemicals that provide high selectivity, allowing the etching rate and selectivity parameters to be optimized independently to protect sensitive structures while maintaining productivity
Solution Approach 2:
The patent introduces a bottom contact etch stop layer (BCESL) as an intermediary protective layer between the self-aligned contacts and the etching process. This BCESL layer is specifically designed to be etched at a different rate than the ILD layer, acting as a mediator that stops the etching process before damaging the underlying contacts and cap layers
2Reliability
If the etching selectivity of the self-aligned contact material with respect to the ILD layer is reduced, then contact-to-gate shorts are prevented, but the trench formation becomes less precise
Solution Approach 1:
The patent changes the material composition parameters of the self-aligned contacts by using fluorinated materials or materials with specific chemical compositions that exhibit low etching selectivity with respect to the ILD layer. This material parameter change ensures that the contacts are protected during etching while maintaining trench formation precision through the high selectivity of the etchant composition for the ILD layer
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 allows for the formation of trenches with high aspect ratios without damaging the underlying structures, thereby reducing the risk of circuit shorts and enhancing the integrity of semiconductor devices.
Implementation Method 1
A plasma-less etching process using an etchant composition with high selectivity, comprising a hydrogen halide and a nitrogen-containing compound, is employed to etch silicon oxide dielectric layers
Data Source
AI summary
A method for manufacturing a semiconductor device includes: forming a feature in a dielectric layer disposed on a semiconductor substrate, the dielectric layer including silicon oxide, the feature extending downwardly from a top surface of the dielectric layer and including silicon, a nitride compound, a low-k dielectric material other than silicon oxide, or combinations thereof; and selectively etching the dielectric layer using an etchant composition to form a trench extending downwardly from the top surface of the dielectric layer, the etchant composition including a hydrogen halide and a nitrogen-containing compound represented by Formula (A) ofwherein R1, R2, R3 are each independently hydrogen, methyl, or ethyl.