Fluorine-Deficient Gas Etch for Multi-Depth TDVs
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Solution Overview
Problem
Conventional etching processes for through dielectric via (TDV) structures in 3D integrated circuits fail to achieve sufficient etching rates and selectivity to form TDVs of different depths in a single process without damaging interconnect structures, requiring multiple design masks and photoresist layers.
Innovation Solution
A single anisotropic etch process using fluorine-deficient fluorocarbon species, such as CxFyM, where M is chlorine, bromine, sulfur, oxygen, or nitrogen, to concurrently form TDV openings of varying depths without adverse effects on interconnect structures, utilizing a single etching gas composition like C5F10O, which provides rapid etching rates and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fluorocarbon gas plasma etching is used, then etching process is simple, but etching rate is insufficient and selectivity is poor for forming TDVs of different depths
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from conventional saturated fluorocarbon gases (CF4, CHF3) to fluorine-deficient fluorocarbon gases (C5F10O, C4F8). This parameter change in gas composition provides both high etching rates and excellent etching selectivity, enabling formation of TDVs at different depths (first TDV opening at first depth, second TDV opening at second depth greater than first depth) in a single etching process while protecting interconnect structures from erosion.
Solution Approach 2:
The patent uses a composite etching gas system comprising fluorine-deficient fluorocarbon gas (C5F10O or C4F8) combined with specific process conditions. This composite approach creates a plasma environment that simultaneously achieves rapid dielectric etching through fluorine radical reactions while maintaining selectivity through polymer deposition on sidewalls, resolving the contradiction between etching rate and selectivity.
2Manufacturing precision
If multiple design masks and photoresist layers are applied to form TDVs of different depths, then etching precision is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The patent makes the single fluorine-deficient fluorocarbon gas etching process universal for forming TDVs at multiple different depths. The process can simultaneously create first TDV openings at a first depth and second TDV openings at a second depth greater than the first depth using the same gas composition and process parameters, eliminating the need for multiple specialized masks and photoresist layers that would otherwise be required for each depth level.
Solution Approach 2:
The patent merges multiple etching operations into a single etching process. Instead of performing separate etching steps for each TDV depth level with different masks and photoresists, the fluorine-deficient fluorocarbon gas enables concurrent etching of multiple TDV openings at different depths in one continuous process, significantly reducing fabrication complexity.
3Productivity
If aggressive etching is used to achieve high etching rates, then productivity is improved, but interconnect structure integrity is compromised
Solution Approach 1:
The patent converts the typically harmful effect of polymer deposition during plasma etching into a beneficial protective mechanism. The fluorine-deficient fluorocarbon gas (C5F10O, C4F8) generates carbon-containing polymers that deposit on the sidewalls of etching features, forming a protective layer that prevents excessive lateral etching and protects underlying interconnect structures from damage, while still allowing rapid vertical etching progress.
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
Enables the formation of TDV structures of different depths in a single fabrication step with minimal impact on interconnect integrity, reducing fabrication costs and complexity by avoiding multiple masks and photoresist layers, and maintaining rapid etching rates.
Implementation Method 1
a single anisotropic etch process using fluorine-deficient fluorocarbon species
Implementation Method 2
conventional etching processes, the BEOL dielectrics are etched using a plasma of fluorocarbon gases
Implementation Method 3
fluorine-deficient fluorocarbon species, such as CxFyM, where M is chlorine, bromine, sulfur, oxygen, or nitrogen, to concurrently form TDV openings of varying depths
Data Source
AI summary
After bonding a second substrate to a first substrate through a bonded material layer to provide a bonded structure, through dielectric via (TDV) openings of different depths are concurrently formed in the bonded structure by performing a single anisotropic etch using fluorine-deficient species that are obtained by dissociation of fluorocarbon-containing molecules.