Concave Sawing Strip for Wafer Waviness Reduction
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Solution Overview
Problem
Existing sawing methods for semiconductor wafers produce significant waviness, particularly at the end regions of cuts, due to axial back pressure gradients from sawing suspensions, which are not adequately addressed by reducing suspension application.
Innovation Solution
A sawing strip with a concave recess that cradles the workpiece, where the width of the recess at the point of contact is greater than the strip's surface width on the mounting plate, reducing the uneven application of sawing suspension and lateral deflection of the wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional sawing strip with rectangular cross section is used, then the manufacturing process is simple, but significant waviness occurs in the end region of the cut
Solution Approach 1:
The sawing strip is given a concave curvature on its upper surface that matches the cylindrical shape of the workpiece. This curvature allows the strip to cradle the workpiece properly, distributing the sawing suspension more evenly and preventing the wire from lateral deflection, thereby reducing waviness in the end region of the cut without significantly complicating the manufacturing process
2Manufacturing precision
If the amount of sawing suspension is reduced, then waviness in the end region is reduced, but the measure is not adequate to satisfy increasing requirements for local geometry
Solution Approach 1:
The sawing strip is designed with different properties in different regions: the upper surface has a concave curvature to match the workpiece, while the lower surface maintains a flat mounting surface. This local differentiation allows the strip to provide proper support and suspension distribution where needed, achieving adequate local geometry control without requiring complete reduction of suspension application
3Manufacturing precision
If a sawing strip with concave curvature is used, then waviness is reduced, but the strip structure becomes more complex
Solution Approach 1:
The concave curvature of the sawing strip upper surface is designed to match the cylindrical geometry of the workpiece. This simple curvature modification, rather than a complex multi-component structure, enables the strip to cradle the workpiece effectively, distribute suspension evenly, and prevent wire deflection, achieving waviness reduction with minimal structural complexity
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
Significantly reduces waviness in the sawing-out region, with 80% of wafers produced using the new strip having waviness of 10 μm or less compared to 35% with traditional strips, demonstrating improved planarity and local geometry.
Implementation Method 1
The portions of wire, to which a sawing suspension is applied, work their way through the workpiece, forming parallel sawing gaps. The sawing suspension, which is also referred to as slurry, contains particles of hard material, for example of silicon carbide
Implementation Method 2
add a liquid cooling lubricant, which protects the wire and the workpiece from overheating and at the same time transports slivers of workpiece out from the cutting gaps and away
Data Source
AI summary
A sawing strip for fixing a substantially cylindrical workpiece when cutting off slices from this workpiece with a wire saw has a first face, which is concavely curved perpendicular to its longitudinal direction for connecting to the workpiece, a second face opposite the first face for connecting to a mounting plate, and two side faces which connect the first face and the second face, two edges of the sawing strip at which the side faces meet the first face at a distance a from each other, an imaginary line on the first face marking its minimum distance d from the second face, the side faces being at a distance b, measured at the height of the line and perpendicular to the distance d, wherein the distance b is less than the distance a. The sawing strip is useful for decreasing waviness of wafers cut from a cylindrical workpiece using the sawing strip.