CMP Slurry Adjuvant for Selective Silicon Nitride Polishing
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Solution Overview
Problem
Conventional CMP slurries exhibit low polishing selectivity between insulating silicon oxide and silicon nitride layers, leading to non-uniform removal and thickness variations during the CMP process, which affects the quality and manufacturing of semiconductor devices.
Innovation Solution
A polyelectrolyte salt with a graft type polyelectrolyte having a weight average molecular weight of 1,000–20,000 is used to form an adsorption layer on cationically charged materials, minimizing agglomeration of abrasive particles and enhancing the polishing selectivity of anionically charged materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP slurry is used, then the polishing process can proceed, but the polishing selectivity between insulating silicon oxide and silicon nitride layers is low, causing non-uniform removal and thickness variations
Solution Approach 1:
The patent introduces a polyelectrolyte salt as an intermediary substance that selectively adsorbs onto the silicon nitride layer surface. This intermediary layer modifies the interaction between the CMP slurry and the silicon nitride, reducing its removal rate while maintaining the removal rate of silicon oxide layers, thereby improving polishing selectivity and achieving more uniform thickness control
Solution Approach 2:
The patent changes the chemical composition parameters of the CMP slurry by incorporating polyelectrolyte salt with specific molecular weights and charge characteristics. This parameter change alters the chemical interaction mechanisms during polishing, enabling selective suppression of silicon nitride removal while preserving silicon oxide removal, thus resolving the selectivity and uniformity issues
2Manufacturing precision
If the polishing selectivity is increased to protect silicon nitride layers, then thickness uniformity improves, but the removal rate of anionically charged materials may be reduced
Solution Approach 1:
The polyelectrolyte salt acts as a selective intermediary that forms an adsorption layer only on cationically charged surfaces (silicon nitride), leaving anionically charged surfaces (silicon oxide) unaffected. This selective mediation protects silicon nitride from over-polishing while maintaining efficient removal of silicon oxide, thus improving selectivity without sacrificing productivity
Solution Approach 2:
The patent applies local quality modification by having the polyelectrolyte salt adsorb selectively onto specific regions (silicon nitride layers) based on their surface charge characteristics. This creates locally differentiated polishing behavior: protected regions (silicon nitride) and active removal regions (silicon oxide), achieving high selectivity while maintaining overall process efficiency
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
The solution achieves improved polishing selectivity and uniformity in the CMP process, reducing thickness variations and maintaining the quality of semiconductor devices by effectively inhibiting the polishing of cationically charged materials while allowing for efficient removal of anionically charged materials.
Implementation Method 1
which forms a adsorption layer on the cationically charged material in order to increase the polishing selectivity
Implementation Method 2
The present invention adopts a polyelectrolyte salt comprising a graft type polyelectrolyte having a weight average molecular weight controlled to 1,000～20,000, so as to minimize agglomeration of abrasive particles
Data Source
AI summary
Disclosed is an adjuvant for use in simultaneous polishing of a cationically charged material and an anionically charged material, which forms a adsorption layer on the cationically charged material in order to increase the polishing selectivity of the anionically charged material to cationically charged material, wherein the adjuvant comprises a polyelectrolyte salt containing: (a) a graft type polyelectrolyte that has a weight average molecular weight of 1,000˜20,000 and comprises a backbone and a side chain; and (b) a basic material. CMP (chemical mechanical polishing) slurry comprising the above adjuvant and abrasive particles is also disclosed.