Aqueous Silica Slurry CMP Composition for STI Planarization
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Solution Overview
Problem
Current aqueous chemical mechanical planarization (CMP) polishing compositions face challenges in achieving acceptable oxide dishing control and oxide:nitride selectivity, particularly in shallow trench isolation (STI) applications, with existing silica slurries suffering from unsatisfactory control and inadequate selectivity, and ceria-based compositions being costly and prone to defects.
Innovation Solution
The development of aqueous CMP polishing compositions comprising a dispersion of elongated, bent, or nodular colloidal silica particles with a cationic nitrogen atom, combined with a cationic copolymer of diallylamine or diallylalkylamine salt and sulfur dioxide, which provides improved selectivity and control over oxide and nitride removal, optimizing the pH range from 1 to 4.5 and particle size distribution for effective planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silica slurry formulations are used for CMP polishing in STI applications, then cost is reduced and defects are avoided, but oxide dishing control and oxide:nitride selectivity are insufficient
Solution Approach 1:
The patent modifies the chemical parameters of the silica slurry by incorporating cationic polymers (polyamines or polymers with amine functional groups) and adjusting the pH to acidic ranges (pH 2-4). These parameter changes transform conventional silica slurry into a composition that achieves both cost-effectiveness and improved oxide dishing control with adequate oxide:nitride selectivity for STI applications
Solution Approach 2:
The invention creates a composite polishing composition by combining silica abrasive particles with cationic polymer additives. This composite formulation integrates the abrasive function of silica with the surface-modifying properties of cationic polymers, achieving both economical manufacturing and satisfactory polishing performance including dishing control and selectivity
2Manufacturing precision
If ceria containing CMP polishing compositions are used, then oxide:nitride selectivity is high and oxide removal in trench areas is avoided, but cost increases and process stability deteriorates
Solution Approach 1:
The patent replaces expensive ceria-based polishing compositions with cost-effective silica-based formulations. By using abundant silica materials combined with cationic polymer additives, the invention achieves comparable or adequate selectivity performance at significantly lower cost, making silica a sustainable alternative to ceria for STI CMP applications
3Ease of manufacture
If conventional silica slurries are used, then cost is low, but oxide:nitride selectivity is inadequate for STI applications
Solution Approach 1:
The patent enhances conventional silica slurry by adjusting chemical parameters including adding cationic polymers (polyamines or amine-containing polymers) and lowering pH to acidic ranges. These modifications maintain the cost advantage of silica while achieving adequate oxide:nitride selectivity required for STI processing
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
These compositions enable satisfactory removal rates and selectivity for silicon oxides over silicon nitrides, reducing trench oxide loss and dishing, thereby improving the planarization process in STI applications while avoiding the drawbacks of ceria-based slurries.
Implementation Method 1
a copolymer of a diallylamine salt having a cationic amine group, such as diallylammonium chloride and sulfur dioxide or a copolymer of a diallylalkylamine salt having a cationic amine group, such as diallylmonomethylammonium chloride and sulfur dioxide
Implementation Method 2
aqueous chemical mechanical planarization (CMP polishing) compositions comprising a dispersion of a plurality of elongated, bent or nodular colloidal silica particles
Implementation Method 3
chemical mechanical planarization (CMP polishing) compositions... for polishing a substrate
Data Source
AI summary
The present invention provides aqueous CMP polishing compositions comprising a from 0.5 to 30 wt. %, based on the total weight of the composition of a dispersion of a plurality of elongated, bent or nodular silica particles which contain a cationic nitrogen atom, and from 0.001 to 0.5 wt. %, preferably from 10 to 500 ppm, of a cationic copolymer of a diallylamine salt having a cationic amine group, such as a diallylammonium halide, or a diallylalkylamine salt having a cationic amine group, such as a diallylalkylammonium salt, or mixtures of the copolymers, wherein the compositions have a pH of from 1 to 4.5. Preferably, the cationic copolymer of a diallylamine salt having a cationic amine group comprises a copolymer of diallylammonium chloride and sulfur dioxide and the copolymer of the diallylalkylamine salt having a cationic amine group comprises a copolymer of diallylmonomethylammonium halide, e.g. chloride, and sulfur dioxide. The slurry compositions demonstrate good oxide selectivity in the CMP polishing of pattern wafers having nitride and silicon patterns.