Dielectric Layer CMP with Auto-Stop Slurry for 3D Memory Planarization
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) processes for semiconductor fabrication face challenges in planarizing topographic dielectric layers in 3D memory devices, leading to residual step heights and dishing issues, which cause defects and increase production costs due to the reliance on high selectivity slurries and stop layers.
Innovation Solution
The introduction of an auto-stop slurry without a CMP stop layer, which uses pressure sensitivity to determine the endpoint of the polishing process, allowing for the removal of protrusions and step heights, thereby preventing residual issues and improving throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP process with high selectivity slurry and stop layer is used, then planarization of dielectric layer is achieved, but residual step heights and dishing issues remain
Solution Approach 1:
The patent changes the chemical composition parameters of the CMP slurry by incorporating specific additives (such as surfactants, chelating agents, or polymers) that modify the slurry's interaction with the dielectric layer and metal surfaces. This parameter change enables the slurry to achieve uniform removal rates across different materials without requiring a stop layer, thereby eliminating residual step heights and dishing while maintaining planarization quality.
Solution Approach 2:
The patent introduces an intermediary substance (the specially formulated slurry additive) that mediates between the abrasive particles and the substrate surface. This intermediary modifies the chemical-mechanical interaction to achieve selective removal of protrusions while protecting recessed areas, preventing both residual steps and dishing without needing a separate stop layer.
2Measurement precision
If conventional CMP process with stop layer is used, then endpoint detection is possible, but process complexity and production cost increase
Solution Approach 1:
The patent makes the CMP slurry self-regulating by incorporating pressure-sensitive or topology-sensitive additives that automatically adjust the removal rate based on local surface conditions. The slurry inherently detects the endpoint through its chemical response to surface topology changes, eliminating the need for external stop layers or complex endpoint detection systems while maintaining measurement precision.
Solution Approach 2:
The patent extracts and eliminates the stop layer component from the CMP process by integrating endpoint detection functionality directly into the slurry formulation. This removal of the stop layer simplifies the overall process structure while preserving the ability to accurately detect when planarization is complete.
3Productivity
If mechanical grinding alone is used, then planarization speed is high, but surface damage increases
Solution Approach 1:
The patent uses a composite slurry system combining abrasive particles with chemically active additives that work synergistically. The mechanical abrasion provides high planarization speed while the chemical additives reduce surface damage by modifying the interaction between abrasives and the dielectric layer, creating a composite effect that achieves both productivity and surface quality.
Solution Approach 2:
The patent changes the physical-chemical parameters of the slurry by incorporating additives that modify the abrasiveness and chemical reactivity. This parameter adjustment allows the CMP process to maintain high removal rates through mechanical action while the chemical components reduce surface damage by controlling the intensity of mechanical-grinding effects.
4Object-affected harmful factors
If wet etching alone is used, then surface damage is reduced, but planarization quality is insufficient
Solution Approach 1:
The patent employs a composite slurry formulation that integrates chemical etching agents with mechanical abrasives. The chemical components provide gentle, selective removal that minimizes surface damage, while the abrasive particles contribute mechanical planarization power to achieve high planarization quality, combining both benefits in a single unified process.
Solution Approach 2:
The patent merges wet etching and mechanical polishing functions into a single CMP process by combining chemical additives with abrasive particles in the slurry. This merging allows the process to simultaneously achieve the surface damage reduction characteristic of wet etching and the planarization quality characteristic of mechanical polishing, eliminating the need to choose between the two approaches.
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 effectively eliminates residual step heights and dishing, reduces defects, and enhances the removal rate of protrusions, leading to improved manufacturing efficiency and cost reduction in CMP processes for 3D memory devices.
Implementation Method 1
uses pressure sensitivity to determine the endpoint of the polishing process
Implementation Method 2
Chemical mechanical polishing (CMP, a.k.a. chemical mechanical planarization) is a process of smoothing wafer surface with the combination of chemical etching and free abrasive mechanical polishing
Implementation Method 3
Chemical mechanical polishing (CMP, a.k.a. chemical mechanical planarization) is a process of smoothing wafer surface with the combination of chemical etching and free abrasive mechanical polishing
Data Source
AI summary
Methods for polishing dielectric layers using an auto-stop slurry in forming semiconductor devices, such as three-dimensional (3D) memory devices, are provided. The methods include forming a stack structure in a staircase region and a core array region, the stack structure including a staircase structure in the staircase region; forming a dielectric layer over the staircase region and a peripheral region outside the stack structure; and polishing the dielectric layer using an auto-stop slurry containing a ceria-based abrasive.