Polishing Slurry for Barrier Layer CMP
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Solution Overview
Problem
The existing polishing methods for semiconductor devices, particularly in the Damascene process, face challenges in achieving high polishing rates for barrier layers while minimizing dishing and thinning, especially when dealing with copper and copper alloys, due to the hardness of barrier materials like tantalum and their resistance to etching.
Innovation Solution
A polishing slurry with a pH range of 3 to 4, containing a metal-oxidizing agent concentration of 0.01 to 3 percent by weight, an oxidized metal dissolving agent with a pKa of 3.5 or more, and a metal anticorrosive agent, along with polishing particles like colloidal silica, is used to enhance the polishing rate of barrier layers while reducing etching and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an oxidized metal dissolving agent is added to increase polishing rate, then the polishing rate is improved, but excessive etching occurs causing dishing
Solution Approach 1:
The patent adjusts the pH of the polishing slurry to a specific range (2.0-4.0) and controls the concentration of the oxidized metal dissolving agent to balance etching rate and polishing rate, preventing excessive etching that causes dishing while maintaining high polishing efficiency
Solution Approach 2:
The polishing slurry contains a composite formulation including oxidized metal dissolving agent, metal anticorrosive agent, oxidizing agent, and polishing particles working together - the dissolving agent removes oxides to enable polishing while the anticorrosive agent prevents excessive etching, creating a balanced system that achieves high polishing rate without dishing
2Reliability
If a metal anticorrosive agent is added to protect metal surface, then corrosion resistance is improved, but polishing rate decreases
Solution Approach 1:
The patent optimizes the concentration of metal anticorrosive agent and controls pH to ensure adequate corrosion protection while maintaining sufficient polishing rate through the synergistic action of multiple components in the slurry formulation
3Productivity
If polishing particles concentration is increased to improve polishing rate, then productivity is improved, but dishing and thinning increase
Solution Approach 1:
The patent controls the concentration of polishing particles and adjusts pH to optimize the balance between mechanical removal and chemical etching, preventing excessive removal that causes dishing and thinning while maintaining high polishing rate
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 allows for a high polishing rate of barrier layers with reduced dishing and thinning, ensuring the formation of reliable metal wiring patterns and improving the electrical characteristics of semiconductor devices.
Implementation Method 1
the surface of the metal film is oxidized by an oxidizing agent
Implementation Method 2
the oxidized layer is scraped off by the solid polishing particles
Implementation Method 3
the scraping effect by the solid polishing particles is enhanced by dissolving (hereinafter, referred to as "etching") the particles of metal oxides, which have been scraped off by the solid polishing particles, in the polishing liquid
Implementation Method 4
The metal anticorrosive agent forms a protective film on the oxidized layer of the metal film surface, and prevents the oxidized layer from solving in the polishing slurry
Data Source
AI summary
A polishing slurry comprises a metal-oxidizing agent, a metal anticorrosive agent, an oxidized metal dissolving agent and water. The oxidized metal dissolving agent is at least one kind selected from the group consisting of an acid in which the negative value of the logarithm of the dissociation constant Ka (pKa) of a first dissociable acid group is 3.5 or more, an ammonium salt of the acid and an organic acid ester of the acid. The pH of the polishing slurry is within the range of 3 to 4. The concentration of the metal-oxidizing agent is within the range of 0.01 to 3 percent by weight. In the wiring-formation process of the semiconductor device, the conductor used for the barrier layer can be polished at a high polishing rate by using the polishing slurry having the low polishing particle concentration and the low metal anticorrosive agent concentration.