Wire Guide Roll Thermal Control for Wafer Slicing
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Solution Overview
Problem
Existing wafer slicing methods using wire saws face challenges in maintaining flat, plane-parallel side surfaces of semiconductor wafers due to axial relative movement caused by thermal expansion and contraction of workpieces and wire guide rolls, leading to warping of wafers.
Innovation Solution
The method involves measuring changes in the length of the wire guide roll coatings using sensors and rings fixed to the coatings, and cooling the wire guide rolls and their bearings independently to compensate for thermal changes, thereby minimizing axial displacement and maintaining precise cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire guide rolls are used during sawing operation, then the sawing process can be performed, but thermal expansion and contraction cause axial relative movement leading to wafer warping
Solution Approach 1:
The patent applies parameter changes by actively controlling the temperature of wire guide rolls to compensate for thermal expansion and contraction. Sensors measure the position of wire sections, and based on these measurements, the temperature parameters of the wire guide rolls are adjusted to maintain constant axial position, thereby preventing wafer warping while enabling continuous sawing operation.
Solution Approach 2:
The patent implements a feedback control system where sensors continuously measure the axial position of wire sections relative to the workpiece. These measurements are fed back to a control system that adjusts the cooling/heating of wire guide rolls in real-time, creating a closed-loop control that compensates for thermal effects and maintains manufacturing precision.
2Manufacturing precision
If the wire guide rolls are cooled to compensate for thermal expansion, then axial displacement is reduced, but the cooling system complexity increases
Solution Approach 1:
The patent applies self-service by using the wire sections themselves as measurement references. The existing wire sections, which are already part of the sawing system, are used as markers for position measurement. This eliminates the need for separate complex measurement infrastructure, as the system uses its own components to monitor and control thermal effects.
Solution Approach 2:
The patent replaces complex mechanical position measurement and adjustment mechanisms with a thermal control system. Instead of using mechanical feedback devices to physically adjust wire guide roll positions, the system uses temperature control to achieve the same positional stability, simplifying the overall mechanical 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
This approach effectively reduces axial movement between the workpiece and wire sections, ensuring flat and plane-parallel wafers by reversing or compensating for thermal-induced length changes, thereby minimizing warp and achieving precise cutting.
Implementation Method 1
changes in the length of the workpiece and of the wire guide rolls are mentioned in US 2010/0089377 A1, said changes being attributed to changes in temperature and an associated thermal expansion or thermal contraction
Implementation Method 2
changes in the length of the workpiece and of the wire guide rolls are mentioned in US 2010/0089377 A1, said changes being attributed to changes in temperature and an associated thermal expansion or thermal contraction
Implementation Method 3
frictional heat is generated particularly during the movement of the sawing wire around the wire guide rolls and when the sawing wire engages into the workpiece
Data Source
AI summary
A method for slicing wafers from a workpiece includes providing wire guide rolls each having a grooved coating with a specific thickness and providing rings at opposing ends of a first of the coatings of a respective wire guide roll. The rings are fixed exclusively to the first coating. A sawing wire including wire sections disposed in a parallel fashion is tensioned between the wire guide rolls. The wire sections of the sawing wire are moved relative to the workpiece so as to perform a sawing operation. A change in length of the first coating, brought about by a temperature change, is measured by measuring distances between sensors and the rings. The wire guide rolls are cooled in a manner dependent on the measured distances.