Metal Oxide Etch Stop Layer With Hydroxyl-Free Si Capping
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Solution Overview
Problem
Current etch stop layers in semiconductor fabrication, particularly those containing metal oxides, suffer from high hydroxyl group concentrations that can oxidize underlying conductive features, necessitating thick layers to mitigate oxidation, which increases parasitic capacitance and decreases device speed as technology scales down.
Innovation Solution
A method to significantly reduce or eliminate hydroxyl groups from the etch stop layer using specialized treatments such as atomic layer deposition (ALD) and silicon-based monomers to form M-O—Si groups, allowing for an etch stop layer thickness less than 50 Å while preventing oxidation of underlying conductive features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal oxide is used to form etch stop layer, then etch selectivity is improved, but hydroxyl groups cause oxidation of underlying conductive features
Solution Approach 1:
A capping layer comprising silicon-containing material is deposited over the metal oxide etch stop layer. This capping layer acts as an intermediary barrier that prevents hydroxyl groups from the metal oxide from reaching and oxidizing the underlying conductive features, while allowing the metal oxide to maintain its etch selectivity function.
Solution Approach 2:
The solution employs a composite structure combining metal oxide (for etch selectivity) with silicon-containing capping material (for oxidation protection). This composite approach allows both materials to contribute their respective advantages: the metal oxide provides high etch selectivity while the silicon capping layer prevents oxidation without interfering with the etching process.
2Object-affected harmful factors
If etch stop layer thickness is increased to prevent oxidation, then oxidation protection is improved, but parasitic capacitance increases and device speed decreases
Solution Approach 1:
The oxidation protection function is segmented from the etch stop layer. Instead of relying on a single thick metal oxide layer for both etch stopping and oxidation protection, the solution divides the functionality: a thin metal oxide layer provides etch selectivity while a separate silicon-containing capping layer provides oxidation protection. This segmentation allows the etch stop layer to be kept thin, reducing parasitic capacitance and maintaining high device speed.
3Speed
If etch stop layer thickness is reduced to decrease parasitic capacitance, then device speed is improved, but oxidation protection capability is reduced
Solution Approach 1:
The silicon-containing capping layer serves as an intermediary protective barrier that enables the etch stop layer to be thin while still providing adequate oxidation protection. The capping layer intercepts and blocks the oxidizing action of hydroxyl groups, allowing the underlying metal oxide etch stop layer to maintain a thickness that minimizes parasitic capacitance and maximizes device speed.
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 approach results in an etch stop layer that is substantially free of hydroxyl groups, reducing parasitic capacitance and increasing the operational speed of integrated circuits, while being compatible with existing semiconductor fabrication processes.
Implementation Method 1
deposit a silicon-containing dopant to the etch stop layer, wherein the silicon-containing dopant reacts with the metal oxide and creates a M-O—Si group
Implementation Method 2
specialized treatments such as atomic layer deposition (ALD) and silicon-based monomers to form M-O—Si groups
Data Source
AI summary
A semiconductor device includes a substrate, a first conductive feature disposed in a top portion of the substrate, a metal containing layer disposed on the first conductive feature, and a second conductive feature disposed on and through the metal containing layer and in physical contact with the first conductive feature. The metal containing layer includes an M-O—X group, M representing a metal atom, O representing an oxygen atom, and X representing an element other than hydrogen.