Wafer Polishing Head with Rotatable Rollers for Edge Coverage
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Solution Overview
Problem
Conventional wafer polishing apparatuses fail to effectively clean the entire surface, including the outermost area, leading to incomplete or excessive polishing due to constant-time operation and inability to adapt to varying amounts of foreign matter on different wafers, resulting in inefficiencies and potential yield loss.
Innovation Solution
A system comprising a substrate holder with rotatable rollers contacting the wafer periphery and a polishing head with a polishing tool that can reach the outermost area, along with a rinsing liquid supply and particle counter to determine the polishing endpoint based on particle count, allowing for adaptive polishing and complete surface cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polishing head is positioned inwardly of the wafer periphery to avoid contact with rotating chucks, then the polishing tool can operate safely, but the outermost area of the wafer surface cannot be polished
Solution Approach 1:
The invention changes the substrate holder configuration from conventional chucks to rollers that rotate about their own axes. This dynamic change allows the polishing head to be positioned such that its axis is offset from the wafer center, enabling the polishing tool to reach the outermost area while avoiding contact with the rotating rollers.
Solution Approach 2:
The invention positions the polishing head axis at a distance from the wafer center such that the sum of the distance from the polishing head axis to the outermost edge of the polishing tool and the distance from the substrate holder axis to the polishing head axis exceeds the wafer radius. This dimensional arrangement allows the polishing tool to cover the entire wafer surface including the outermost area.
2Ease of operation
If constant-time polishing is used for all wafers, then the polishing process is simple to control, but excessive polishing and/or insufficient polishing occurs due to varying foreign matter amounts
Solution Approach 1:
The invention introduces a particle counter that detects particles in the rinsing liquid during polishing. The polishing process is automatically terminated when the particle count falls below a predetermined threshold, providing real-time feedback control. This ensures that polishing is performed for the appropriate duration based on the actual foreign matter amount on each wafer, preventing both excessive and insufficient polishing.
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
Enables complete polishing of the wafer surface, reducing the need for edge polishing, preventing excessive consumption of polishing tools, and ensuring uniform surface quality across wafers with varying initial foreign matter levels, thereby enhancing throughput and yield.
Implementation Method 1
a polishing head configured to rub a polishing tool against a first surface of the substrate to polish the first surface
Implementation Method 2
a substrate holder configured to hold a substrate and rotate the substrate, the substrate holder including a plurality of rollers which can contact a periphery of the substrate and are rotatable about their respective own axes
Data Source
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AI summary
An apparatus which can polish an entirety of a surface of a substrate, such as a wafer, is disclosed. The apparatus according to the present invention includes a substrate holder configured to hold a substrate and rotate the substrate; and a polishing head configured to rub a polishing tool against a first surface of the substrate to polish the first surface. The substrate holder includes a plurality of rollers which can contact a periphery of the substrate. The plurality of rollers are rotatable about their respective own axes.