Contact Plug Height Uniformity via Two-Stage CMP
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Solution Overview
Problem
The micro-loading effect caused by pattern density differences in semiconductor manufacturing leads to uneven etch stop layer removal, affecting manufacturing yield and integrity of contact plugs in integrated circuit devices.
Innovation Solution
A method involving the use of a sacrificial layer and a two-stage chemical mechanical polish (CMP) process with different slurries to balance polishing rates across pattern-dense and pattern-scarce regions, ensuring even removal of metallic material and minimizing damage to the etch stop layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single CMP process is used to polish metallic material, then the polishing process is simple and fast, but the micro-loading effect causes uneven polishing across pattern-dense and pattern-scarce regions, leading to height differences and excessive etch stop layer removal
Solution Approach 1:
The single CMP process is divided into two separate CMP processes. The first CMP process uses a first slurry to polish the metallic material, and the second CMP process uses a second slurry to further polish the metallic material. This segmentation allows each process to be optimized for different regions (pattern-dense and pattern-scarce), thereby reducing the micro-loading effect and achieving more uniform contact plug heights while maintaining overall process efficiency
Solution Approach 2:
Different slurries are used in the two CMP processes to provide locally optimized polishing characteristics. The first slurry is formulated to address the specific needs of pattern-dense regions, while the second slurry is formulated for pattern-scarce regions. This local quality approach ensures that each region receives the appropriate polishing conditions, reducing height differences and preventing excessive etch stop layer removal
2Productivity
If the CMP process removes excess metallic material efficiently, then productivity is high, but the etch stop layer is excessively removed, affecting device integrity
Solution Approach 1:
The first CMP process is designed to remove the majority of excess metallic material before the second CMP process. This preliminary action allows the bulk of material removal to occur under controlled conditions, and the second CMP process then performs a more gentle, precise removal that protects the etch stop layer from excessive removal, thereby maintaining device integrity while still achieving high overall productivity
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 effectively reduces height differences between contact plugs in dense and scarce regions, enhancing manufacturing yield and reducing leakage, with experiment results showing a significant reduction in height difference from 337 Å to 16 Å across a wafer.
Implementation Method 1
a first chemical mechanical polish (CMP) process is performed to polish the metallic material and the sacrificial layer
Data Source
AI summary
A method includes forming an etch stop layer over and contacting a gate electrode of a transistor, forming a sacrificial layer over the etch stop layer, and etching the sacrificial layer, the etch stop layer, and an inter-layer dielectric layer to form an opening. The opening is then filled with a metallic material. The sacrificial layer and excess portions of the metallic material over a top surface of the etch stop layer are removed using a removal step including a CMP process. The remaining portion of the metallic material forms a contact plug.