Wafer Back Surface Polishing via Inverted Tool Positioning
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Solution Overview
Problem
Conventional wafer polishing methods require reversing wafers to access the back surface, leading to increased processing time and potential contamination from air impurities, while also leaving the outermost area of the back surface unpolished, necessitating additional edge polishing steps.
Innovation Solution
A method and apparatus that rotate the substrate using rollers to hold the periphery with the back surface facing downward, allowing a polishing tool to move circularly or reciprocally across the entire back surface, including the outermost area, while supplying a liquid and maintaining contact, eliminating the need for reversing the wafer and reducing processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wafer is reversed to polish the back surface, then the back surface can be accessed for polishing, but processing time increases and air impurities may adhere to the wafer
Solution Approach 1:
Instead of reversing the wafer to access the back surface for polishing, the invention inverts the approach by positioning the polishing tool below the wafer while keeping the wafer in its original orientation. The polishing head moves upward to contact and polish the back surface, eliminating the need for wafer reversal and associated contamination risks.
2Reliability
If the polishing head is positioned inwardly of the periphery to avoid contact with rotating chucks, then the polishing process can proceed, but the outermost area of the wafer surface remains unpolished
Solution Approach 1:
The invention changes the spatial arrangement by positioning the polishing head in the vertical dimension below the wafer, rather than in the horizontal plane inward of the periphery. This allows the polishing tool to access the outermost areas of the back surface without interfering with the rotational chuck mechanism.
3Manufacturing precision
If multiple reversal operations are performed on wafers, then back surface polishing can be achieved, but the overall processing time is increased
Solution Approach 1:
The invention performs the back surface polishing action in advance within the same processing sequence as the front surface, by positioning the polishing head to access the back surface before the wafer is returned to the cassette. This eliminates the need for separate reversal and polishing operations that would extend the processing cycle.
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 enables efficient polishing of the entire back surface without reversing the wafer, preventing air impurity adhesion and reducing overall processing time by integrating the outermost area polishing within the main process, thus enhancing processing efficiency and reducing contamination risks.
Implementation Method 1
polishing an entirety of the back surface of the substrate by moving a polishing tool relative to the substrate while supplying a liquid onto the back surface of the substrate
Implementation Method 2
rotating a substrate by rotating a plurality of rollers about their respective own axes while the rollers contact a periphery of the substrate
Data Source
AI summary
A method and an apparatus which can efficiently polish an entirety of a back surface, including an outermost area thereof, of a substrate while the back surface of the substrate faces downward are disclosed. The method includes rotating a substrate by rotating a plurality of rollers about their respective own axes while the rollers contact a periphery of the substrate with a back surface of the substrate facing downward; and polishing an entirety of the back surface of the substrate by moving a polishing tool relative to the substrate while supplying a liquid onto the back surface of the substrate and while placing the polishing tool in contact with the back surface of the substrate, the polishing tool being located at a lower side of the substrate.