CMP Scratch Resistance for Non Planar Bond Pads
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Solution Overview
Problem
The chemical mechanical polish (CMP) process used in microelectronic device fabrication causes corrosion of bond pads due to abrasive and corrosive slurry, leading to reliability issues and increased complexity and cost with thicker metal liners or additional pattern steps.
Innovation Solution
A protective layer is formed over the metal liner in recesses containing bond pads, which is then removed using a CMP process, leaving the metal liner protected from the slurry, thereby reducing corrosion and simplifying the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metal liner thickness is increased to protect against CMP slurry corrosion, then the protection against corrosion improves, but the deposition process cost and complexity increase
Solution Approach 1:
A protective layer is introduced as an intermediary material between the CMP slurry and the metal liner. This protective layer serves as a mediator that absorbs the harmful effects of the slurry, preventing direct contact with and corrosion of the bond pads, while allowing the metal liner to remain at its original, simpler thickness
Solution Approach 2:
The protective layer is applied in advance before the CMP process to preemptively shield the metal liner and bond pads from slurry exposure. This preliminary protective action eliminates the need for thicker metal liners, thereby avoiding increased deposition complexity while ensuring corrosion protection during the subsequent CMP operation
2Reliability
If additional pattern steps are added to protect the metal liner, then the protection against corrosion improves, but the fabrication cost and complexity increase
Solution Approach 1:
The protective layer serves multiple functions simultaneously: it protects the metal liner during CMP, provides a planarization surface, and can be selectively removed to expose protected bond pads. This multi-functionality eliminates the need for separate protective pattern steps, reducing fabrication complexity while maintaining corrosion protection
3Reliability
If thicker top metal is used to protect the metal liner, then the protection against corrosion improves, but the patterning difficulty increases and minimum features are limited
Solution Approach 1:
The protective layer provides localized protection precisely where needed - over the bond pads and metal liner regions susceptible to slurry corrosion. This localized approach maintains the original metal liner thickness and patterning dimensions, avoiding the need for thicker top metal that would compromise minimum feature sizes and line separation requirements
4Reliability
If a protective layer is added over the metal liner, then the protection against corrosion improves, but the fabrication process complexity increases
Solution Approach 1:
The protective layer is designed as a temporary, disposable element that is applied for the specific purpose of protecting against CMP slurry, then selectively removed after serving its protective function. This disposable approach adds minimal complexity compared to permanent structural modifications, as the protective layer can be a simple spin-coated polymer that requires only basic deposition and removal processes
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 minimizes corrosion and fabrication complexity by protecting the metal liner during the CMP process, allowing for more aggressive CMP operations with reduced costs and maintaining the integrity of the bond pads.
Implementation Method 1
The CMP process uses a slurry with abrasive particles and corrosive chemicals to remove the protective layer and the metal liner
Implementation Method 2
the abrasive particles and corrosive chemicals attack the metal liner on the bond pads, causing corrosion of the bond pads
Data Source
AI summary
A microelectronic device is formed by providing a substrate having a recess at a top surface, and a liner layer formed over the top surface of the substrate, extending into the recess. A protective layer is formed over the liner layer, extending into the recess. A CMP process removes the protective layer and the liner layer from over the top surface of the substrate, leaving the protective layer and the liner layer in the recess. The protective layer is subsequently removed from the recess, leaving the liner layer in the recess. The substrate may include an interconnect region with a bond pad and a PO layer having an opening which forms the recess; the bond pad is exposed in the recess. The liner layer in the recess may be a metal liner suitable for a subsequently-formed wire bond or bump bond.