CMP Polishing Liquid pH Control for Cobalt Galvanic Corrosion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMP polishing liquids fail to effectively suppress galvanic corrosion of cobalt-containing portions during the polishing process, leading to excessive etching and potential shorts in semiconductor devices, while additives to prevent corrosion often reduce the polishing rate.
Innovation Solution
A CMP polishing liquid with a pH of 4.0 or less, containing polishing particles, a metal corrosion inhibitor such as pyridines, tetrazoles, triazoles, benzotriazoles, and phthalic acids, and a quaternary phosphonium salt, which maintains a favorable polishing rate by controlling the corrosion potential difference between cobalt and other metals to within 0-300 mV, thereby reducing galvanic corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CMP polishing liquids are used to polish cobalt-containing portions, then the polishing process can proceed, but galvanic corrosion occurs leading to excessive etching and potential shorts
Solution Approach 1:
The patent changes the chemical parameters of the polishing liquid by controlling pH to 4.0 or less and selecting specific corrosion inhibitors (pyridines, tetrazoles, triazoles, benzotriazoles, or phthalic acids) to adjust the corrosion potential difference between cobalt and other metals to 0-300 mV, thereby suppressing galvanic corrosion while maintaining polishing precision
Solution Approach 2:
The patent introduces metal corrosion inhibitors as intermediary substances that mediate between the polishing liquid and the cobalt-containing portions, preventing direct galvanic corrosion while allowing the polishing process to continue. These inhibitors form protective films on metal surfaces, reducing the harmful electrochemical reactions
2Reliability
If metal corrosion inhibitors are added to prevent galvanic corrosion, then corrosion is suppressed, but the polishing rate decreases
Solution Approach 1:
The patent optimizes the concentration and type of corrosion inhibitors along with pH control to achieve a balance where sufficient corrosion protection is provided while maintaining adequate polishing rate. The specific selection of inhibitors and pH range of 4.0 or less creates optimal conditions for both protection and material removal
Solution Approach 2:
The patent applies partial action by using corrosion inhibitors at controlled concentrations that provide sufficient protection against galvanic corrosion without completely passivating the metal surface, thereby maintaining the necessary polishing rate. The corrosion potential difference is controlled to a specific range (0-300 mV) rather than eliminating it entirely
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 effectively suppresses galvanic corrosion of cobalt-containing portions while maintaining a favorable polishing rate, preventing shorts and ensuring the integrity of semiconductor devices.
Implementation Method 1
removing the conductive substance from the protrusions by the mechanical friction generated between the CMP polishing liquid and the conductive substance portion
Implementation Method 2
The surface of the substrate on which the conductive substance portion has been formed is then pressed against the polishing pad, and a prescribed pressure (hereafter referred to as the 'polishing pressure') is applied from the back side of the substrate
Implementation Method 3
conventional CMP polishing liquids fail to effectively suppress galvanic corrosion of cobalt-containing portions during the polishing process, leading to excessive etching
Implementation Method 4
maintains a favorable polishing rate by controlling the corrosion potential difference between cobalt and other metals to within 0-300 mV, thereby reducing galvanic corrosion
Data Source
AI summary
An embodiment of the present invention relates to a CMP polishing liquid used for polishing a polishing target surface having at least a cobalt-containing portion and a metal-containing portion that contains a metal other than cobalt, wherein the CMP polishing liquid contains polishing particles, a metal corrosion inhibitor and water, and has a pH of 4.0 or less, and when the corrosion potential EA of cobalt and the corrosion potential EB of the metal are measured in the CMP polishing liquid, the absolute value of the corrosion potential difference EA−EB between the corrosion potential EA and the corrosion potential EB is 0˜300 mV.