Dynamic Wire Tension Control for Semiconductor Slice Cutting
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Solution Overview
Problem
Existing wire cut-off lapping methods face limitations in achieving uniformly high flatness and minimizing the cut-in wedge of semiconductor slices, particularly for large and very large cylindrical rods, due to issues with wire tension variability and slurry distribution, leading to tapering and roughness in the cut surfaces.
Innovation Solution
A multiwire cut-off lapping method using a wire saw with a structured wire and controlled longitudinal tension, where the wire tension is increased at the instant of cut-in and reduced as the engagement length increases, combined with strategies to manage slurry film thickness and particle size distribution, and viscosity adjustments during the cutting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wire tension is increased at cut-in to reduce kerf width and improve flatness, then manufacturing precision improves, but wire rupture risk increases
Solution Approach 1:
The wire tension is made dynamic rather than static. The tension is automatically adjusted during the cutting process: high tension is applied at cut-in to minimize kerf width and maximize flatness, then gradually reduced as the wire penetrates deeper into the workpiece to prevent rupture. This dynamic tension control resolves the contradiction between needing high tension for precision and low tension for reliability.
Solution Approach 2:
The wire tension parameter is changed continuously during the cutting operation. The system transitions from a constant tension regime to a variable tension regime where tension decreases as a function of penetration depth or time, allowing optimization of both flatness (requiring high tension) and rupture prevention (requiring low tension).
2Productivity
If wire speed is increased to improve productivity, then productivity improves, but wire tension variability and slurry distribution worsen
Solution Approach 1:
The system incorporates feedback control where wire tension is continuously monitored and adjusted based on cutting depth and load conditions. This feedback mechanism allows the system to maintain optimal tension levels even at higher wire speeds, compensating for the increased variability that would otherwise occur and preserving manufacturing precision while enabling higher productivity.
Solution Approach 2:
The wire tension control system dynamically adapts to changing cutting conditions at higher speeds. Rather than using fixed tension settings, the system continuously modulates tension to account for variations in engagement length, material hardness, and slurry distribution, allowing high-speed cutting without sacrificing uniformity.
3Manufacturing precision
If engagement length is increased to improve flatness, then manufacturing precision improves, but wire tension requirements increase leading to higher rupture risk
Solution Approach 1:
The wire tension is dynamically reduced as engagement length increases during penetration. Early in the cut when engagement length is short, high tension is maintained to ensure flatness. As engagement length grows and the wire becomes more deeply engaged, tension is progressively reduced to compensate for the increased load, preventing rupture while maintaining the flatness benefits of longer engagement.
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 results in semiconductor slices with uniformly high flatness and reduced cut-in wedge, achieving consistent thickness and quality across the entire cutting operation.
Implementation Method 1
hard substances enter between the surface of the wire and that of the workpiece, are moved under pressure relative to the latter by means of a sliding or rolling motion, and remove chips from the workpiece by means of material overloading or fatigue, by brittle erosion
Implementation Method 2
In the case of cut-off lapping, the tools for removing material are in the form of sharp-edged particles of a hard substance, for example silicon carbide, as a suspension in a viscous carrier liquid
Data Source
AI summary
A method for simultaneously cutting a multiplicity of slices from a cylindrical workpiece, along strictly convex cutting faces, by supplying a suspension of hard substances in a carrier liquid, as cutting medium, to wire portions, while the wire portions, having a longitudinal tension, define a relative motion to the workpiece as a result of wire guide roller rotation with continual alternation between a first direction of rotation and a second direction of rotation, which is opposite to the first direction of rotation, wherein, during the rotation in the first direction, the wire is moved a first length, and during the rotation in the second direction, the wire is moved a second length, and the second length is shorter than the first, and at the cutting operation start a first longitudinal wire tension is greater than a second longitudinal tension at the end.