Single-Wafer Polishing Method for Semiconductor Flatness
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Solution Overview
Problem
Current single-side polishing methods for semiconductor wafers result in insufficient flatness and variations, particularly at the periphery, which hinders the miniaturization of devices and reduces yield.
Innovation Solution
A single-wafer processing method involving a polishing step followed by a shifting step, where the relative position of the polishing head and wafer is adjusted in the rotation direction to mitigate the influence of slight irregularities on the backing plate, thereby enhancing flatness and reducing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-side polishing is performed without interruption, then polishing efficiency is maintained, but surface flatness deteriorates due to surface sag
Solution Approach 1:
The polishing process is divided into multiple stages with intermediate interruptions. The wafer is polished for a first period, then removed and repositioned on the backing plate, and polished again for a second period. This segmentation allows the wafer to be repositioned relative to the polishing cloth, preventing surface sag while maintaining overall polishing efficiency.
Solution Approach 2:
The polishing process incorporates dynamic repositioning of the wafer on the backing plate between polishing stages. By changing the relative position of the wafer to the polishing cloth through removal and reattachment, the system dynamically adjusts to prevent surface sag, improving surface flatness without completely halting production.
2Manufacturing precision
If polishing time is extended to improve flatness, then surface quality improves, but surface sag increases due to prolonged polishing
Solution Approach 1:
The total polishing time is divided into multiple shorter polishing periods separated by interruption steps. During each interruption, the wafer is removed from the polishing cloth and repositioned on the backing plate. This segmentation prevents continuous prolonged contact that causes surface sag, while the cumulative polishing time remains sufficient to achieve high surface flatness.
Solution Approach 2:
The process skips the harmful effect of continuous polishing by introducing brief interruption periods where the wafer is removed from the polishing cloth. These interruptions prevent surface sag from developing during extended polishing, allowing the process to rush through the problematic continuous contact phase while maintaining overall polishing effectiveness.
3Manufacturing precision
If multi-step polishing with interruptions is implemented, then surface sag is reduced, but process complexity increases
Solution Approach 1:
The polishing process is segmented into discrete polishing steps and interruption steps. Each polishing step involves holding the wafer on the backing plate and contacting it with the polishing cloth. Each interruption step involves removing the wafer and repositioning it on the backing plate. This clear segmentation makes the complex process manageable and repeatable, achieving high surface flatness through standardized cycles.
Solution Approach 2:
The backing plate serves multiple functions: it holds the wafer during polishing, facilitates removal and repositioning during interruptions, and maintains wafer alignment. This self-service capability of the backing plate reduces the need for additional complex positioning mechanisms, managing process complexity while achieving improved surface flatness.
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 method significantly improves the flatness and reduces variations in the polished semiconductor wafers, achieving better surface quality and increased yield.
Implementation Method 1
a semiconductor wafer is held by suction on a polishing head with a backing plate therebetween
Data Source
AI summary
An object is to provide a single-wafer processing single-side polishing method and a single-wafer processing single-side polishing apparatus, which increase the flatness of a semiconductor wafer and reduce variations in flatness. The single-wafer processing single-side polishing method includes a polishing step of polishing a semiconductor wafer; and a shifting step of transferring the semiconductor wafer from a polishing plate to a tray outside the polishing plate, moving the relative position of the semiconductor wafer and the polishing head in the rotation direction of the polishing head, and then holding the semiconductor wafer with the polishing head. The polishing step is performed a plurality of times, and the shifting step is performed at least once between the plurality of polishing steps.