MIMCap Fabrication via Nitride Hard Mask Planarization
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Solution Overview
Problem
The existing MIMCap process flow faces challenges with defect formation due to non-planar wafer surfaces and micromasking, which complicates the patterning of lower metal layers and increases the risk of defects in the fabrication of metal-insulator-metal capacitors.
Innovation Solution
A method is introduced where a first metal layer is patterned with a nitride layer as a hard mask, followed by filling gaps with plasma oxide and polishing, allowing for planarization, and then removing the nitride layer to deposit and pattern a dielectric and second metal layer, resulting in a planarized MIMCap structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the entire metal stack is deposited at once and upper levels are patterned first, then the MIMCap structure can be formed, but the wafer surface becomes non-planar and defects form due to micromasking
Solution Approach 1:
The patent divides the metal stack fabrication into separate segments: lower metal layers are formed first, followed by dielectric layer deposition, then upper metal layers are added. This segmentation allows each layer to be planarized independently, maintaining wafer flatness and preventing micromasking defects during subsequent patterning operations.
Solution Approach 2:
The patent performs preliminary planarization actions by depositing dielectric layers and performing CMP (chemical mechanical polishing) before completing the metal stack formation. This preliminary action ensures the wafer surface is flat before subsequent patterning steps, preventing defects while maintaining productivity.
2Productivity
If upper metal layers are patterned and etched first, then the MIMCap structure can be formed, but the wafer becomes non-planar making lower metal layer patterning much more difficult
Solution Approach 1:
The patent inverts the conventional fabrication sequence by forming lower metal layers first, then adding dielectric and upper metal layers afterward. This reversal ensures that when upper layers are patterned, the lower layers remain protected and the wafer surface remains planar, greatly simplifying the patterning process for all metal layers.
Solution Approach 2:
The patent introduces an additional dielectric layer dimension between metal layers, transforming the structure from a simple stacked metal configuration to a multi-dimensional metal-dielectric-metal architecture. This dimensional change enables independent planarization and patterning of each metal layer without interference.
3Productivity
If defects form during upper metal layer patterning, then defects are transferred to lower metal layer due to micromasking
Solution Approach 1:
The patent extracts the problematic micromasking mechanism by separating the patterning operations for upper and lower metal layers into different time sequences. By completing lower metal layer patterning before upper metal layer deposition, the harmful micromasking effect is eliminated, preventing defect transfer and improving fabrication reliability.
Solution Approach 2:
The patent applies beforehand cushioning by depositing dielectric layers and performing planarization before completing metal stack formation. This protective measure cushions against potential micromasking defects, ensuring that even if upper layer patterning creates issues, they cannot transfer to lower layers, thus maintaining high reliability.
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 enables the fabrication of MIMCap structures with reduced defects and improved planarity, enhancing the patterning precision and reducing the risk of micromasking, thereby increasing the reliability of the capacitor fabrication process.
Implementation Method 1
A nitride layer is then deposited on the first metal layer. The nitride layer and the first metal layer are etched to form a first metal-insulator-metal capacitor (MIMCap) metal layer.
Implementation Method 2
The gaps among the first MIMCap metal layer are filled with a plasma oxide
Implementation Method 3
the excess plasma oxide is polished using the nitride layer a polish stop
Implementation Method 4
a dielectric layer and a second metal layer are deposited on the first MIMCap metal layer
Data Source
AI summary
A method for fabricating a metal-insulator-metal capacitor (MIMCap) is disclosed. A first metal layer is provided on top of an oxide layer. A nitride layer is then deposited on the first metal layer. The nitride layer and the first metal layer are etched to form a MIMCap metal layer. The gaps among the MIMCap metal layer are filled with a plasma oxide, and the excess plasma oxide is polished using the nitride layer a polish stop. After removing the nitride layer, a dielectric layer and a second metal layer are deposited on the MIMCap metal layer. Finally, the dielectric layer and the second metal layer are etched to form a set of MIMCap structures.