Tungsten CMP Composition with Charged Silica Abrasives
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Solution Overview
Problem
Conventional chemical-mechanical polishing (CMP) processes for tungsten layers face challenges in achieving local and global planarity, leading to issues like array erosion, plug and line recessing, and tungsten etching defects, which compromise device integrity and electrical performance.
Innovation Solution
A water-based chemical mechanical polishing composition containing colloidal silica abrasive particles with a permanent positive charge of at least 6 mV, aggregated primary particles, and optional additives like an iron-containing accelerator and oxidizer, designed to enhance the polishing rate and selectivity of tungsten and silicon dioxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple polishing steps are employed to meet local and global planarity requirements, then device planarity is improved, but process complexity and time increase
Solution Approach 1:
The invention changes the chemical parameters of the polishing composition by incorporating specific oxidizers (potassium permanganate, sodium percarbonate, hydrogen peroxide) and pH adjusters to optimize the removal rates of tungsten and silicon dioxide. This allows a single polishing step to achieve the planarity that previously required multiple steps, thereby improving device planarity while reducing process complexity
Solution Approach 2:
The polishing composition uses a composite formulation combining colloidal silica abrasive particles with multiple chemical components including oxidizers, chelating agents, and pH buffers. This composite chemical-mechanical system enables selective removal of both tungsten and silicon dioxide layers in one process, achieving high device planarity without requiring multiple separate polishing steps
2Productivity
If conventional CMP compositions are used for tungsten polishing, then tungsten removal is achieved, but array erosion, plug and line recessing, and tungsten etching defects occur
Solution Approach 1:
The invention carefully controls the pH parameter within a specific range (2-6, preferably 3-4) and adjusts the concentration of oxidizers to optimize the chemical reaction rates. This parameter optimization enables effective tungsten removal while minimizing harmful side effects like array erosion and plug recessing, thereby maintaining device integrity
Solution Approach 2:
The polishing composition introduces chelating agents (EDTA, DTPA) as intermediaries that complex with metal ions during the polishing process. These intermediaries help control the chemical reactions between the oxidizers and tungsten, preventing excessive etching and corrosion while maintaining effective tungsten removal, thus protecting device integrity
3Loss of time
If a single polishing step is used for tungsten removal, then process time is reduced, but planarity requirements are not met
Solution Approach 1:
The invention optimizes multiple parameters simultaneously including pH (2-6), oxidizer concentration, and abrasive particle size to achieve a polishing composition that can remove both tungsten and silicon dioxide at controlled rates. This multi-parameter optimization enables a single polishing step to achieve the planarity that previously required multiple steps, reducing process time while maintaining manufacturing precision
Solution Approach 2:
The polishing composition is designed to perform multiple functions simultaneously: mechanical abrasion by colloidal silica particles, chemical oxidation of tungsten by oxidizers, and selective removal of silicon dioxide. This multi-functional composition enables a single polishing step to accomplish what previously required multiple specialized steps, reducing loss of time while achieving required planarity
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 composition achieves improved polishing rates and selectivity, particularly in the second polishing step, reducing tungsten etching and enhancing planarity, thereby improving the overall integrity and performance of semiconductor devices.
Implementation Method 1
The relative motion of the substrate and pad abrades and removes a portion of the material from the surface of the substrate, thereby polishing the substrate
Implementation Method 2
The polishing of the substrate by the relative movement of the pad and the substrate may be further aided by the chemical activity of the polishing composition (e.g., by an oxidizing agent and other chemical compounds present in the CMP composition)
Implementation Method 3
The colloidal silica abrasive particles further have a permanent positive charge of at least 6 mV
Data Source
Figure 1
AI summary
A chemical mechanical polishing composition for polishing a substrate having a tungsten layer includes a water based liquid carrier and colloidal silica abrasive particles dispersed in the liquid carrier. The colloidal silica abrasive particles have a permanent positive charge of at least 6 mV. 30 percent or more of the colloidal silica abrasive particles include three or more aggregated primary particles.