Silicon Nitride Polishing Liquid Selectivity
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Solution Overview
Problem
Conventional silicon nitride polishing liquids used in CMP processes for semiconductor manufacturing often result in excessive polishing of polysilicon or modified polysilicon gate materials, leading to deterioration in the performance of semiconductor integrated circuits, and fail to achieve sufficient polishing rates for silicon nitride.
Innovation Solution
A silicon nitride polishing liquid with a pH of 2.5 to 5.0, containing colloidal silica and an organic acid with sulfonic or phosphonic acid groups, which acts as a polishing accelerator, effectively differentiating the polishing rates of silicon nitride and other silicon-including materials to prevent excessive polishing of gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing liquids are used to increase the polishing rate of silicon nitride, then the polishing rate of silicon nitride is improved, but the polishing rate of polysilicon or modified polysilicon is excessively increased, leading to deterioration in performance of semiconductor integrated circuits
Solution Approach 1:
The invention changes the chemical composition parameters of the polishing liquid by incorporating specific organic acids (sulfonic acid or phosphonic acid groups) and controlling pH within 2.5-5.0 range. This parameter modification enables the polishing liquid to selectively accelerate silicon nitride removal while maintaining controlled polishing rates for polysilicon and modified polysilicon, thereby resolving the contradiction between polishing rate and selectivity
Solution Approach 2:
The invention uses a composite polishing liquid formulation combining colloidal silica particles with specific organic acids (sulfonic acid or phosphonic acid groups). This composite approach creates synergistic effects where the organic acid component provides selective chemical enhancement for silicon nitride while the colloidal silica provides mechanical polishing action, achieving both high productivity and manufacturing precision
2Productivity
If the polishing rate of silicon nitride is increased, then the planarization efficiency is improved, but the integrity of gate electrodes is compromised due to excessive polishing
Solution Approach 1:
By adjusting the pH to 2.5-5.0 and incorporating specific organic acids, the chemical reactivity of the polishing liquid is tuned to preferentially attack silicon nitride. This parameter control ensures that silicon nitride layers are efficiently removed for planarization while polysilicon gate electrodes are protected from excessive material loss, maintaining their structural integrity and device reliability
Solution Approach 2:
The organic acid components act as chemical intermediaries that facilitate selective removal of silicon nitride. These intermediaries form temporary chemical complexes or modify surface properties of silicon nitride to enhance its reactivity toward polishing, while having minimal effect on polysilicon gate electrodes, thus enabling efficient planarization without compromising gate electrode integrity
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 polishing liquid achieves a high-speed polishing of silicon nitride while selectively suppressing the polishing of polysilicon or modified polysilicon, ensuring the integrity of gate electrodes and improving the performance of semiconductor integrated circuits by maintaining a polishing rate ratio within the desired range.
Implementation Method 1
an organic acid that has at least one sulfonic acid group or phosphonic acid group in the molecular structure thereof and functions as a polishing accelerator for silicon nitride
Implementation Method 2
comprising (a) colloidal silica
Implementation Method 3
pressing the surface (surface to be polished) of a substrate (wafer) against the pad, and rotating both the polishing platen and the substrate while a given pressure (polishing pressure) is applied thereto from the rear face to planarize the surface of the substrate by the mechanical friction generated
Data Source
AI summary
A silicon nitride polishing liquid for chemical mechanical polishing of a body to be polished in a planarization process for manufacturing of a semiconductor integrated circuit, the body to be polished including at least a first layer containing silicon nitride and a second layer containing at least one silicon-including material selected from the group consisting of polysilicon, modified polysilicon, silicon oxide, silicon carbide, and silicon oxycarbide, the silicon nitride polishing liquid having a pH of 2.5 to 5.0, and including (a) colloidal silica, (b) an organic acid that has at least one sulfonic acid group or phosphonic acid group in the molecular structure thereof and functions as a polishing accelerator for silicon nitride, and (c) water.