CMP Slurry with Boric Acid for Hard Mask Preservation
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Solution Overview
Problem
Chemical-mechanical planarization (CMP) processes face challenges in efficiently planarizing semiconductor devices at submicron dimensions, particularly in minimizing the loss of hard masks during the CMP process, which affects the performance and integrity of subsequent layers.
Innovation Solution
Incorporating a slurry with a metal oxide removal rate (RR) suppressor, such as boric acid, in the CMP process, which selectively absorbs on the hard mask surface, reducing the removal rate and preserving the hard mask thickness by providing electrostatic repulsion against abrasive particles, thus maintaining the hard mask as a CMP stop layer and reducing gate height loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a CMP process is applied to planarize the semiconductor device, then the planarization of the workpiece is improved, but the hard mask thickness is reduced due to excessive removal rate
Solution Approach 1:
The patent introduces a slurry composition as an intermediary medium between the abrasive particles and the hard mask. The slurry contains chelating agents and pH controllers that chemically interact with the hard mask material (e.g., tungsten oxide, molybdenum oxide) to form protective complexes, reducing the removal rate while maintaining planarization effectiveness.
Solution Approach 2:
The patent modifies the chemical parameters of the slurry by controlling pH levels and adding chelating agents. These parameter changes alter the chemical reactivity between the slurry and hard mask, reducing the removal rate to an optimal range that preserves hard mask thickness while achieving sufficient planarization.
2Productivity
If the CMP process uses high removal rate slurry, then the planarization efficiency is improved, but the gate height loss increases
Solution Approach 1:
The patent optimizes slurry parameters including pH control (using buffers) and chelating agent concentration to achieve a balanced removal rate. This allows efficient planarization while controlling gate height loss by preventing excessive chemical attack on the hard mask during the CMP process.
Solution Approach 2:
The patent employs feedback control by monitoring the removal rate and adjusting slurry composition accordingly. The chelating agents and pH controllers create a self-regulating system where the chemical environment adapts to prevent excessive hard mask removal while maintaining planarization progress.
3Productivity
If the hard mask removal rate is high, then the CMP process speed is improved, but the subsequent layer formation is affected due to insufficient hard mask thickness
Solution Approach 1:
The slurry composition acts as a protective intermediary that selectively reduces the removal rate of the hard mask through chelating agents. This allows the CMP process to proceed at adequate speed while preserving sufficient hard mask thickness to serve as an effective stop layer and etch mask for subsequent fabrication steps.
Solution Approach 2:
The patent creates local chemical differentiation in the slurry environment, where chelating agents preferentially interact with hard mask materials (tungsten oxide, molybdenum oxide) rather than other layers. This selective chemical action preserves hard mask thickness locally while allowing removal of unwanted materials.
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 CMP process effectively minimizes the loss of hard masks, ensuring their sufficient thickness for subsequent processes while maintaining high removal rates for other layers, thereby enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
selectively absorbs on the hard mask surface
Implementation Method 2
reducing the removal rate and preserving the hard mask thickness by providing electrostatic repulsion against abrasive particles
Data Source
AI summary
A method includes: forming source/drain epitaxy structures over a semiconductor fin; forming a first ILD layer covering the source/drain epitaxy structures; forming a gate structure over the semiconductor fin and between the source/drain epitaxy structures; forming a capping layer over the gate structure; thinning the capping layer; forming a hard mask layer over the capping layer; forming a second ILD layer spanning the hard mask layer and the first ILD layer; forming, by using an etching operation, a contact hole passing through the first and second ILD layers to one of the source/drain epitaxy structures, the etching operation being performed such that the hard mask layer has a notched corner in the contact hole; filling the contact hole with a conductive material; and performing a CMP process on the conductive material until that the notched corner of the hard mask layer is removed.