Multilayer Etch Stop Structure to Prevent VIMIC in IC Interconnects
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Solution Overview
Problem
The formation of hillocks and pinholes in etch stop layers during plasma etching leads to galvanic corrosion and diffusion of conductive material in integrated circuits (ICs), resulting in defects like via-induced metal island corrosion (VIMIC), which reduces the reliability and performance of electrical connections between capacitors and interconnect structures.
Innovation Solution
An etch stop structure comprising a first etch stop layer, a first insulator layer, and a second etch stop layer is disposed along conductive wires, with specific thicknesses and materials to mitigate hillock formation and pinhole creation, thereby reducing damage during plasma and wet etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single etch stop layer is used during plasma etching, then the etching process can be completed, but hillocks and pinholes form in the etch stop layer causing galvanic corrosion and metal diffusion
Solution Approach 1:
The single etch stop layer is divided into multiple etch stop layers (first etch stop layer, second etch stop layer, and third etch stop layer) separated by an insulator layer. This segmentation prevents hillock formation and pinhole defects that occur in single-layer structures, thereby eliminating galvanic corrosion and metal diffusion while maintaining etching process completion.
Solution Approach 2:
An insulator layer is introduced between the etch stop layers to act as an intermediary barrier. This insulator layer prevents direct electrical contact between conductive elements, blocking galvanic corrosion and metal diffusion pathways while allowing the etching process to proceed through the stacked structure.
2Manufacturing precision
If etch stop layer thickness is increased to prevent pinholes, then pinhole formation is reduced, but hillock formation increases causing VIMIC defects
Solution Approach 1:
The total thickness required to prevent pinholes is distributed across multiple thinner etch stop layers separated by an insulator layer. This segmentation allows each individual etch stop layer to maintain appropriate thickness (avoiding excessive thickness that causes hillocks) while the stacked structure collectively prevents pinhole formation through the insulator barrier.
Solution Approach 2:
The insulator layer, which adds structural complexity, converts the harmful effect of required thickness into a benefit: it prevents both pinholes (by providing additional barrier layers) and hillocks (by distributing thickness across multiple layers with insulation between them), thereby eliminating VIMIC defects.
3Reliability
If multiple etch stop layers with insulator layer are used, then hillock and pinhole formation is reduced improving reliability, but device structure complexity increases
Solution Approach 1:
The etch stop structure is segmented into multiple layers with an insulator layer in between, which systematically addresses reliability issues (hillocks and pinholes) through physical separation and insulation. While this increases structural complexity, it provides a proven method to eliminate galvanic corrosion and metal diffusion, ensuring electrical connection stability.
Solution Approach 2:
The etch stop structure uses composite construction with alternating conductive etch stop layers and insulator layers. This composite structure leverages the properties of different materials (conductive for etch stopping, insulating for corrosion prevention) to achieve superior reliability compared to single-material structures, accepting increased complexity as necessary for performance.
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 structure enhances the reliability and performance of electrical connections by minimizing defects in the interconnect structure, increasing the yield and stability of the ICs.
Implementation Method 1
The formation of hillocks and pinholes in etch stop layers during plasma etching leads to galvanic corrosion and diffusion of conductive material
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an integrated circuit (IC) including a plurality of conductive contacts overlying a semiconductor substrate. A plurality of first conductive wires is disposed on the plurality of conductive contacts. A plurality of conductive vias overlies the first conductive wires. An etch stop structure is disposed on the first conductive wires. The plurality of conductive vias extend through the etch stop structure. The etch stop structure includes a first etch stop layer, a first insulator layer, and a second etch stop layer. The first insulator layer is disposed between the first etch stop layer and the second etch stop layer.