Piezoelectric Polishing Pad for Wafer Uniformity Control
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Solution Overview
Problem
Conventional chemical-mechanical planarization (CMP) systems face challenges in achieving uniformity across semiconductor wafers due to lack of control over normal force distribution, leading to non-uniform material removal and reflection issues, which can cause detection failures and yield loss.
Innovation Solution
Incorporation of an array of piezoelectric actuators in the polishing pad that senses topography and adjusts local aggressiveness to counter non-uniformities, allowing for micro- or nano-scale control of material removal, enabling improved edge tunability and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP systems use uniform normal force across the wafer, then the polishing process is simple to control, but the material removal is non-uniform across different areas of the wafer
Solution Approach 1:
The polishing pad is divided into multiple independently controllable zones with piezoelectric actuators, allowing separate control of normal force in different regions. This segmentation enables localized adjustment of polishing aggressiveness to achieve uniform material removal across the wafer surface.
Solution Approach 2:
The system transitions from static uniform normal force to dynamic, adjustable normal force distribution. Piezoelectric actuators enable real-time modification of the polishing pad's surface topology and applied pressure, allowing the system to adapt and compensate for non-uniformities during the polishing process.
2Manufacturing precision
If polishing pads of different hardnesses are used to achieve different pressure distributions, then regional pressure control is improved, but micro-scale or nano-scale surface topography anomalies cannot be addressed
Solution Approach 1:
Different regions of the polishing pad can be independently adjusted to have different local properties (hardness, surface topology, normal force) through piezoelectric actuators. This allows each zone to be optimized for its specific function, addressing micro-scale surface anomalies with locally tailored polishing characteristics.
Solution Approach 2:
The system changes physical parameters (normal force magnitude, surface topology) of the polishing pad dynamically using piezoelectric actuators. This enables continuous adjustment of polishing aggressiveness at different locations and times, allowing precise control of material removal rates to correct localized surface non-uniformities.
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 wafer surface uniformity, reduces over/under polishing, and increases yield by allowing precise control of material removal, particularly at the wafer's peripheral edge, improving processing quality and reducing defects.
Implementation Method 1
The polishing pad may include an array of piezoelectric actuators. Each piezoelectric actuator of the array may include at least one dimension being less than 100 micrometers. The array of piezoelectric actuators may define an at least substantially planar surface when not activated.
Data Source
AI summary
A chemical-mechanical polishing system includes a rotatable head for mounting a wafer thereto, a polishing pad mounted to a rotatable platen, and a fluid dispenser for dispensing a fluid onto a surface of the polishing pad. The polishing pad includes an array of piezoelectric actuators. The chemical-mechanical polishing system includes a controller operably coupled to each piezoelectric actuator. The controller measures voltages output by the piezoelectric actuators of the array, determines, qualitatively, a topography of the wafer surface based on the measured voltages, and adjusts an aggressiveness of at least one portion of the polishing pad based on the determined topography. The controller adjusts the aggressiveness by inducing the piezoelectric effect or reverse piezoelectric effect in one or more piezoelectric actuators to adjust a surface topography of the polishing pad.