Buffered Slurry Formulation for Cobalt CMP pH Stability
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Solution Overview
Problem
Existing polishing compositions for cobalt chemical-mechanical polishing (CMP) exhibit unstable pH and cobalt removal rates, leading to inconsistent performance and reduced shelf life.
Innovation Solution
The development of polishing compositions comprising an abrasive, a buffering material with a Lewis acid or Bronsted-Lowry acid, and a compound devoid of a carboxylic acid moiety, along with a polishing accelerator and oxidizer, which maintains a pH of 6 to 9 and stabilizes the cobalt removal rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing polishing compositions are used for cobalt CMP, then polishing function is provided, but pH and cobalt removal rates are unstable leading to poor shelf life
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by introducing a specific buffering system comprising a compound with pKa 6-9 and controlling the pH to be within 1 unit of the pKa. This parameter optimization stabilizes the cobalt removal rate and pH throughout the shelf life, directly resolving the contradiction between reliability and compositional stability.
Solution Approach 2:
The buffering compound acts as an intermediary substance that mediates between the acidic and basic components of the slurry, maintaining stable pH conditions. This intermediary buffering system prevents pH drift and ensures consistent cobalt removal rates, thereby improving both reliability and shelf life simultaneously.
2Productivity
If polishing compositions with unstable pH are used, then cobalt removal can occur, but removal rates are inconsistent
Solution Approach 1:
By optimizing the pH parameter to be within 1 unit of the buffering compound's pKa (pKa 6-9), the patent ensures that the cobalt removal rate remains consistent throughout the product shelf life. This parameter control transforms the inconsistent removal rate into a reliable, predictable process.
Solution Approach 2:
The buffering system provides a self-regulating feedback mechanism where the buffer resists pH changes when acid or base is added during the polishing process or over time. This automatic pH stabilization ensures consistent cobalt removal rates without requiring external control, improving both productivity and reliability.
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 proposed compositions provide stabilized pH and cobalt removal rates, improving the shelf life and performance of CMP processes by maintaining consistent cobalt removal rates and pH levels over time.
Implementation Method 1
the buffering material comprises a first component and a second component; the first component comprises a Lewis acid or a Bronsted-Lowry acid; and the second component comprises a compound devoid of a carboxylic acid moiety, with a pKa of about 6 to about 9 and wherein the difference between the pKa and the pH of the polishing composition at point of use is less than 1
Implementation Method 2
the polishing composition further comprises an oxidizer. In some embodiments, the oxidizer is present in an amount of about 0.1 wt. % to about 4 wt. %. In some embodiments, the oxidizer is hydrogen peroxide
Implementation Method 3
polishing compositions comprising an abrasive and a buffering material
Data Source
AI summary
Described herein are polishing compositions containing an abrasive and a buffering material, wherein the pH of the polishing composition is about 6 to about 9, and methods of preparing and using the same.