Mixed Abrasive Tungsten CMP Composition for Planarity Control
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) processes for tungsten layers face challenges in achieving high throughput and cost-effectiveness while maintaining substrate planarity, with issues like array erosion and tungsten etching defects compromising device integrity and electrical performance.
Innovation Solution
A CMP composition comprising a water-based liquid carrier with first and second silica abrasives, where the first silica has a permanent positive charge and the second silica has a neutral or non-permanent positive charge, along with an iron-containing accelerator, hydrogen peroxide oxidizer, and a pH in the range of 1.5 to 5.0, is used to polish tungsten layers, enhancing planarity and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high tungsten removal rate is pursued to maintain high throughput, then productivity is improved, but array erosion and tungsten etching defects increase compromising planarity and device integrity
Solution Approach 1:
The patent modifies the chemical composition parameters of the CMP slurry by incorporating specific oxidizers (potassium permanganate, sodium persulfate, hydrogen peroxide), chelating agents (EDTA, DTPA, HEDTA), and catalysts (ferrous sulfate, ferric nitrate) to optimize the chemical reaction rate with tungsten. This enables high removal rates while maintaining controlled chemical mechanical polishing that preserves planarity and reduces defects
Solution Approach 2:
The invention uses a composite abrasive system combining colloidal silica particles (10-500 nm) with ceramic abrasives (alumina, silica beads, or cubic boron nitride). This composite approach provides both high removal rate capability and controlled polishing action to maintain planarity, resolving the contradiction between productivity and manufacturing precision
2Productivity
If conventional CMP composition is used to achieve high throughput, then productivity is improved, but costs increase due to reduced slurry performance and increased defect rates
Solution Approach 1:
The patent optimizes the concentration ranges of key components: colloidal silica (0.01-5 wt%), ceramic abrasives (0.01-5 wt%), oxidizers (0.1-10 wt%), and chelating agents (0.1-5 wt%). These parameter optimizations enable effective polishing at lower material costs while maintaining high throughput and reducing defect-related rework costs
Solution Approach 2:
The invention employs readily available, cost-effective materials such as colloidal silica, common ceramic abrasives (alumina, silica beads), and standard chemical agents (EDTA, hydrogen peroxide, ferric nitrate). These inexpensive but effective components enable high throughput polishing without the high costs associated with specialized or proprietary slurry formulations
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 described CMP composition achieves improved tungsten removal rates and planarity, reducing costs and addressing defects such as array erosion and tungsten etching, thereby enhancing semiconductor device performance and manufacturing efficiency.
Implementation Method 1
The first silica abrasive is a colloidal silica abrasive having a permanent positive charge of at least 10 mV
Implementation Method 2
The polishing composition may further optionally include an iron containing accelerator, such as an iron containing catalyst
Implementation Method 3
hydrogen peroxide oxidizer
Implementation Method 4
The relative motion of the substrate and pad abrades and removes a portion of the material from the surface of the substrate
Data Source
Figure 1
AI summary
A chemical mechanical polishing composition includes a water based liquid carrier and first and second silica abrasives dispersed in the liquid carrier. The first silica abrasive is a colloidal silica abrasive having a permanent positive charge of at least 10 mV. The second silica abrasive has a neutral charge or a non-permanent positive charge. A method for chemical mechanical polishing a substrate including a tungsten layer includes contacting the substrate with the above described polishing composition, moving the polishing composition relative to the substrate, and abrading the substrate to remove a portion of the tungsten from the substrate and thereby polish the substrate.