Tri-Layer Etch Stop Structure for Punch-Through and Corrosion Control
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Solution Overview
Problem
The challenge in integrated circuit fabrication lies in achieving high dry-etch selectivity and preventing punch-through and corrosion during the fabrication of multi-gate transistors at the 10 nanometer node and beyond, where variability in conventional processes limits the scalability and results in issues like Cu voids and unreasonably tight depth uniformity across the wafer.
Innovation Solution
The implementation of a tri-layer etch stop layer using wet-strip removable aluminum oxide layers provides enhanced dry etch selectivity, mitigating punch-through and corrosion by allowing via and breakthrough etch operations to land selectively on aluminum-oxide layers, rather than copper or other metals, thereby preventing underlying metal attack and improving yield and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-layer etch stop layers are used, then the fabrication process is simpler, but dry-etch selectivity is insufficient leading to punch-through and corrosion
Solution Approach 1:
The patent divides the etch stop layer into multiple distinct layers (first etch stop layer, second etch stop layer, and third etch stop layer) with different materials and etch selectivities. This segmentation allows each layer to perform a specific function: the first layer prevents punch-through, the second layer provides a hard stop, and the third layer prevents corrosion, thereby resolving the contradiction between reliability and complexity by using structured complexity to solve reliability issues.
Solution Approach 2:
The patent employs a composite multi-layer structure where each etch stop layer is made of different materials optimized for specific etching conditions. The first etch stop layer has high selectivity to the underlying metal, the second layer provides a hard stop, and the third layer offers corrosion resistance. This composite approach enables tailored etch selectivity for different process stages, improving reliability while managing complexity through functional differentiation.
2Productivity
If via etch operations proceed without multi-layer etch stop protection, then the etching process is faster, but Cu voids and metal corrosion occur
Solution Approach 1:
The multi-layer etch stop structure is prepared in advance before via etching begins. The first etch stop layer is specifically designed with high etch selectivity to the underlying copper or cobalt metal, allowing the via etch to proceed rapidly while the etch stop layer prevents over-etching that would cause Cu voids and corrosion. This preliminary protective structure enables fast etching without compromising metal interconnect reliability.
3Reliability
If etch stop layers are not optimized for dry etch selectivity, then the fabrication process is simpler, but punch-through and corrosion occur during etching
Solution Approach 1:
Each etch stop layer is designed with specific local properties: the first etch stop layer has high dry etch selectivity to the underlying metal to prevent punch-through, the second layer provides a hard stop with appropriate etch resistance, and the third layer offers corrosion resistance. This local quality differentiation within the etch stop structure enables optimized performance for each specific etching challenge without requiring overly complex configurations.
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 ensures minimal erosion of conductive lines and dielectric materials, enhances etch process control, and improves the reliability of integrated circuit structures by preventing Cu voids and shorting, thereby increasing the yield and reliability of the fabrication process.
Implementation Method 1
enhanced dry etch selectivity
Implementation Method 2
allowing via and breakthrough etch operations to land selectively on aluminum-oxide layers
Implementation Method 3
mitigating punch-through and corrosion
Implementation Method 4
preventing underlying metal attack
Implementation Method 5
wet-strip removable aluminum oxide layers
Data Source
AI summary
Multi-layer etch stop layers are described. In an example, an integrated circuit structure includes a conductive line in a first interlayer dielectric material above a substrate. A first dielectric etch stop layer, a second dielectric layer and a third dielectric layer are on the conductive line and the first interlayer dielectric material. A second interlayer dielectric material is on the third dielectric etch stop layer. An opening is in the second interlayer dielectric material, in the third dielectric etch stop layer, and in the second dielectric etch stop layer, in the first dielectric etch stop layer. A conductive structure is in the opening, the conductive structure in direct contact with the conductive line.