CMP Slurry Selectivity for Silicon Oxide and Nitride
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Solution Overview
Problem
Conventional CMP slurries face challenges in achieving high selectivity for silicon oxide removal over silicon nitride, leading to excessive silicon nitride loss and defects during semiconductor manufacturing, particularly in advanced node processes where high-k metal gate and FinFET technologies are used.
Innovation Solution
Aqueous polishing compositions comprising an abrasive, a nitride removal rate reducing agent with a hydrophobic and hydrophilic portion separated by alkylene oxide groups, an acid or base, and water, with a pH range of 2 to 6.5, which selectively polish silicon oxide at high rates while minimizing silicon nitride removal and dishing, using colloidal silica as the abrasive to reduce defects and improve selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP slurries are used to remove silicon oxide, then silicon oxide removal rate is improved, but silicon nitride removal rate increases excessively causing loss and defects
Solution Approach 1:
The patent introduces a nitride removal rate reducing agent as an intermediary substance that selectively interacts with silicon nitride to reduce its removal rate. This agent acts as a mediator between the abrasive particles and the silicon nitride layer, preventing excessive nitride removal while allowing oxide removal to proceed at high rates.
Solution Approach 2:
The patent modifies the chemical parameters of the CMP slurry by adjusting pH to a specific range (2-6.5) and incorporating nitride removal rate reducing agents. These parameter changes create a chemically selective environment that differentiates between silicon oxide and silicon nitride removal rates, enabling high oxide removal while protecting nitride.
2Productivity
If conventional CMP slurries are used to remove silicon oxide, then material removal rate is improved, but defectivity increases on patterned wafers
Solution Approach 1:
The nitride removal rate reducing agent serves as a protective intermediary that prevents abrasive particles from causing defects in the silicon nitride layer. By reducing the chemical interaction between abrasives and nitride, the agent minimizes defect formation while maintaining efficient oxide removal.
Solution Approach 2:
The patent optimizes slurry parameters including pH level (2-6.5), abrasive concentration, and nitride removal rate reducing agent concentration to achieve the optimal balance between removal rate and defectivity. These parameter adjustments create a chemically controlled polishing environment that reduces defect formation.
3Loss of substance
If high selectivity for silicon oxide removal is achieved, then silicon nitride loss is minimized, but polishing time increases
Solution Approach 1:
The nitride removal rate reducing agent acts as a selective intermediary that allows the CMP process to proceed efficiently. By protecting nitride from excessive removal, the agent enables the use of effective abrasives for oxide removal without the need for extended polishing times that would cause nitride loss.
Solution Approach 2:
The patent adjusts chemical parameters (pH, abrasive type, nitride protection agent concentration) to optimize the removal mechanism. These parameter changes enable high oxide removal rates while maintaining nitride protection, achieving the right balance between selectivity and processing time.
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 compositions achieve a high selectivity ratio of silicon oxide to silicon nitride removal rates, minimizing silicon nitride erosion and dishing, resulting in improved yield and reduced defectivity on patterned wafers, suitable for both current and next-generation semiconductor substrates.
Implementation Method 1
The present disclosure relates to polishing compositions including an abrasive, a nitride removal rate reducing agent, an acid or base, and water
Implementation Method 2
a nitride removal rate reducing agent having a hydrophobic portion containing a C12 to C40 hydrocarbon group; and a hydrophilic portion containing at least one group selected from the group consisting of a sulfinite group, a sulfate group, a carboxylate group, a phosphate group, and a phosphonate group
Data Source
Figure 1(a)~1(d)
Figure 2
Figure 3
AI summary
This disclosure relates to a polishing composition that includes at least one abrasive; at least one nitride removal rate reducing agent, an acid or a base; and water. The at least one nitride removal rate reduce agent can include a hydrophobic portion and a hydrophilic portion; in which the hydrophobic portion includes a C12 to C40 hydrocarbon group and is separated by zero to ten alkylene oxide groups from the hydrophilic portion. The polishing composition has a pH of about 2 to about 6.5, and can have a ratio of a removal rate for a silicon oxide to a removal rate for a silicon nitride of at least about 3:1 when polishing a patterned wafer comprising at least silicon nitride patterns overlayed with at least silicon oxide.