Electrostatic Cleaning of Charged Abrasives in Wafer Polishing
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Solution Overview
Problem
Chemical mechanical polishing processes leave charged abrasive particles on semiconductor wafers due to electrostatic attraction, leading to defects and reduced yield.
Innovation Solution
A process tool with conductive rods within a wafer platen and a wafer brush, applying charges opposite to the polarity of the abrasive particles to create electrostatic forces that attract and remove these particles from the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical mechanical polishing is used to planarize wafer surfaces, then surface flatness is improved, but charged abrasive particles remain on the wafer surface causing defects
Solution Approach 1:
The patent applies electrostatic attraction to convert the harmful effect of charged abrasive particles adhering to the wafer into a beneficial cleaning mechanism. By applying a charge opposite to that of the abrasive particles through conductive rods in the platen and brush, the particles are electrostatically attracted to the cleaning surfaces and removed from the wafer, transforming the adhesion problem into an effective removal mechanism
Solution Approach 2:
The patent introduces conductive rods as intermediary elements between the platen/brush and the abrasive particles. These rods serve as charge carriers that transfer electrostatic charge to the cleaning surfaces, enabling the indirect removal of charged particles through electrostatic attraction without direct mechanical contact with the particles themselves
2Object-generated harmful factors
If conventional cleaning methods are used after polishing, then some particles are removed, but charged abrasive particles remain due to electrostatic attraction
Solution Approach 1:
The patent replaces purely mechanical cleaning methods with an electrostatic-based cleaning system. By substituting mechanical force with electrostatic attraction through charged conductive rods, the system overcomes the limitation of conventional mechanical cleaning that cannot effectively remove particles adhered through electrostatic forces
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
Effectively reduces the number of charged abrasive particles on the wafer, minimizing defects and improving the yield of serviceable wafers.
Implementation Method 1
A first charge having a second polarity, opposite the first polarity, is applied to a first conductive rod arranged within the wafer platen
Data Source
AI summary
A process tool including a polishing pad on a top surface of a wafer platen. A wafer carrier is configured to hold a wafer over the polishing pad. A slurry dispenser is configured to dispense an abrasive slurry including a plurality of charged abrasive particles having a first polarity onto the polishing pad. A first conductive rod is within the wafer platen and coupled to a first voltage supply. A wafer roller is configured to support the wafer. A first wafer brush is arranged beside the wafer roller. A second conductive rod is within the first wafer brush and coupled to a second voltage supply. The first voltage supply is configured to apply a first charge having a second polarity, opposite the first polarity, to the first conductive rod. The second voltage supply is configured to apply a second charge having the second polarity to the second conductive rod.