Ceria Slurry CMP for Transition Metal Oxide Stop-Layer Selectivity
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Solution Overview
Problem
In semiconductor manufacturing, chemical mechanical polishing (CMP) processes face challenges in achieving high selectivity between target layers and stop layers, especially when dealing with transition metal oxides, which result in unwanted thickness loss and difficulty in controlling the polishing process due to the mechanical dominance of traditional SiO2 abrasives.
Innovation Solution
The introduction of ceria oxide (CeOx) as a new abrasive in CMP slurries, which offers lower Mohs hardness and higher weight density, reducing mechanical force and enhancing chemical force, allowing for more material-specific planarization and effective suppression of transition metal oxide removal rates while maintaining removal rates for other materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional SiO2 abrasives are used in CMP processes, then mechanical polishing force is sufficient for general planarization, but selectivity between target layers and stop layers deteriorates and unwanted thickness loss of transition metal oxides occurs
Solution Approach 1:
The patent changes the chemical composition parameter of the abrasive from traditional SiO2 to ceria oxide (CeO2), which has different mechanical and chemical properties. This parameter change enables the abrasive to provide sufficient mechanical polishing force while simultaneously achieving high selectivity for transition metal oxide stop layers, thereby resolving the contradiction between mechanical force and manufacturing precision.
Solution Approach 2:
The patent employs ceria oxide as a composite abrasive material that combines appropriate hardness for mechanical polishing with specific chemical reactivity toward transition metal oxides. This composite material approach allows the slurry to achieve both adequate mechanical force and enhanced selectivity, preventing unwanted thickness loss of stop layers while maintaining effective planarization.
2Ease of manufacture
If traditional SiO2 abrasives are used, then the polishing process is simple and cost-effective, but control over polishing rate and selectivity becomes difficult
Solution Approach 1:
By changing the abrasive material parameter from SiO2 to ceria oxide, the patent enables better control over polishing rate and selectivity while maintaining process simplicity. The ceria oxide abrasive provides tunable chemical reactivity that allows operators to achieve precise control over which layers are removed and at what rate, without significantly complicating the manufacturing process.
3Productivity
If higher mechanical force is applied to achieve faster polishing, then productivity increases, but selectivity deteriorates and stop layer thickness loss increases
Solution Approach 1:
The patent changes the abrasive material to ceria oxide, which provides an optimal balance between mechanical force and chemical selectivity. This parameter change allows the process to achieve high polishing speeds through enhanced chemical reactivity with target layers while maintaining excellent control over stop layer thickness, preventing unwanted removal even at high productivity rates.
Solution Approach 2:
The patent partially replaces purely mechanical polishing action with chemical mechanical action by using ceria oxide abrasive that exhibits specific chemical reactivity toward transition metal oxides. This substitution enables the polishing process to achieve high productivity through chemical assistance while maintaining precise control over stop layer thickness, as the chemical mechanism provides inherent selectivity that prevents excessive mechanical removal.
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
Ceria oxide abrasives in CMP slurries provide improved selectivity and control over the polishing process, reducing unwanted thickness loss and enhancing the ability to stop at specific layers, thereby improving the precision and efficiency of metal CMP operations.
Implementation Method 1
polishing of the wafer surface is achieved as a result of the mechanical friction caused by the polishing particles in the slurry
Implementation Method 2
In the process of chemical mechanical polishing, the wafer is mounted to a rotating plate, and a surface of the wafer is brought into contact with a pad of a polishing machine
Data Source
AI summary
The present disclosure provides a method for manufacturing a semiconductor. The method includes: forming a metal oxide layer over a gate structure over a substrate; forming a dielectric layer over the metal oxide layer; forming a metal layer over the metal oxide layer; and performing a chemical mechanical polish (CMP) operation to remove a portion of the dielectric layer and a portion of the metal layer, the CMP operation stopping at the metal oxide layer, wherein a slurry used in the CMP operation includes a ceria compound. The present disclosure also provides a method for planarizing a metal-dielectric surface.