FinFET CMP Slurry and Hard Mask Removal for CD Uniformity
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Solution Overview
Problem
In semiconductor manufacturing, the chemical-mechanical polishing (CMP) process for FinFETs faces challenges such as uneven topography and increased surface scratches due to the hard mask layer, leading to variations in critical dimension (CD) and potential peeling defects from unremoved slurry residues.
Innovation Solution
The removal of the hard mask layer prior to CMP, combined with a specialized CMP slurry composition that facilitates easier slurry removal and adjusts the polish rate, results in a more balanced loading effect and reduced surface scratches, achieving uniform topography and reduced CD variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the hard mask layer is retained during CMP, then the polishing process can proceed with standard loading, but surface scratches increase and uniformity deteriorates
Solution Approach 1:
The hard mask layer is selectively removed from the wafer surface prior to the CMP process. This extraction of the problematic layer eliminates the source of surface scratches and allows the CMP process to achieve uniform polishing without the harmful effects of the hard mask material interfering with the polishing mechanics.
Solution Approach 2:
The hard mask layer removal is performed as a preliminary step before CMP. By removing the hard mask layer in advance, the wafer surface is prepared in an optimal state for subsequent CMP processing, preventing surface scratches and ensuring uniform polishing results.
2Reliability
If standard CMP slurry is used, then the process is simple, but slurry residues remain and cause peeling defects
Solution Approach 1:
The CMP slurry composition is modified by adjusting key parameters such as pH level, abrasive particle size distribution, and chemical additives. These parameter changes enhance the slurry's ability to be completely removed from the wafer surface after polishing, preventing peeling defects while maintaining process feasibility.
Solution Approach 2:
The CMP slurry is formulated as a composite material containing multiple components including specific abrasives, chemical agents, and binders in optimized ratios. This composite formulation provides both effective polishing action and easy removability, eliminating residues that cause peeling defects.
3Manufacturing precision
If the hard mask layer is present during CMP, then the process flow is shorter, but loading effect becomes unbalanced and CD variations increase
Solution Approach 1:
The hard mask layer is extracted before CMP to eliminate its interfering effect on the polishing loading distribution. This removal ensures that the polishing pressure and material removal rate are uniformly distributed across the wafer surface, achieving consistent critical dimensions without the distortion caused by the hard mask layer's presence.
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 enhances the uniformity of the wafer surface and reduces peeling defects, ensuring a more consistent critical dimension (CD) across the wafer, thereby improving the precision and reliability of subsequent patterning processes.
Implementation Method 1
chemical-mechanical polishing (CMP) process
Data Source
AI summary
A method of forming a semiconductor device includes forming a first epitaxial layer over a substrate to form a wafer, depositing a dielectric layer over the first epitaxial layer, patterning the dielectric layer to form an opening, etching the first epitaxial layer through the opening to form a recess, forming a second epitaxial layer in the recess, etching the dielectric layer to expose a top surface of the first epitaxial layer, and planarizing the exposed top surface of the first epitaxial layer and a top surface of the second epitaxial layer.