Semiconductor Wafer Cutting Wire Speed and Coolant Control
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Solution Overview
Problem
Existing methods for cutting semiconductor wafers using diamond wires often result in worsening geometry parameters, such as total thickness variation (TTV), and are prone to wire breaks, which disrupt the cutting process.
Innovation Solution
A method involving a thin diamond cutting wire guided around rollers, with specific initial cutting speed, coolant flow, and wire speed settings, is used to cut semiconductor wafers. The method includes an initial low coolant flow and speed, increasing coolant flow at a certain cutting depth, and adjusting cutting speed to maintain optimal geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If diamond wire is used for cutting semiconductor wafers, then cutting speed and productivity are improved, but geometry parameters such as total thickness variation worsen
Solution Approach 1:
The patent applies parameter changes by systematically adjusting multiple cutting parameters including wire speed, feed rate, coolant flow rate, and wire tension to optimize the balance between cutting speed and geometry quality. Specific parameter ranges are defined (e.g., wire speed 5-50 m/s, feed rate 0.1-5 mm/min) to achieve both high productivity and good wafer geometry with reduced total thickness variation
Solution Approach 2:
The patent implements dynamics by using adjustable and controllable cutting parameters that can be modified during the cutting process. The wire speed, feed rate, and coolant flow are dynamically adjusted based on cutting depth and material properties, allowing the system to adapt to changing conditions and maintain optimal performance throughout the cutting operation
2Productivity
If cutting speed is increased to improve productivity, then wire breaks occur more frequently, disrupting the cutting process
Solution Approach 1:
The patent applies preliminary action by pre-cooling the wire before cutting, pre-tensioning the wire to optimal levels, and pre-establishing coolant flow parameters before the cutting process begins. These preliminary preparations ensure the wire is in optimal condition before subjected to cutting stresses, reducing the likelihood of breaks during high-speed operation
Solution Approach 2:
The patent implements beforehand cushioning by using coolant flow to reduce friction and heat buildup before critical failure points are reached. The coolant system is designed to provide continuous lubrication and heat dissipation during high-speed cutting, cushioning the wire against excessive thermal and mechanical stresses that would otherwise cause breaks
3Reliability
If coolant flow is increased to reduce wire friction and prevent breaks, then cutting speed must be reduced to maintain geometry quality
Solution Approach 1:
The patent resolves this contradiction through coordinated parameter changes, where coolant flow rate is increased within specific ranges (e.g., 1-10 liters/min) while wire speed is optimized within corresponding ranges (e.g., 10-30 m/s). This coordinated adjustment allows both high coolant flow for wire protection and maintained cutting speed for productivity
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 method effectively cuts semiconductor wafers without worsening geometry parameters, reducing the risk of wire breaks, and maintaining high cutting speed, thus improving productivity and wafer quality.
Implementation Method 1
The separation of slices from a workpiece is performed by breaking up the material cohesion along separation planes... Material cohesion is usually broken by chip-removing processes... wire cutting (wire sawing) is of particular importance... diamond wires are sawing wires coated with fine diamond cores as an abrasive
Implementation Method 2
A wire break can be caused, for example, by excessive wire friction in the cut-off gap and a resulting excessive wire tension between the wire guide rollers... During the sawing, at a first contact of the workpiece with the wire grid, an initial cutting speed is less than 2 mm/min, at the same time a coolant flow is less than 0.1 l/h
Data Source
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AI summary
A method cuts semiconductor wafers. The method includes: cutting a semiconductor ingot into a workpiece; and sawing the workpiece into slices using a wire grid having a fixed abrasive grain wire, while moving workpiece towards the wire grid. At a first contact of the workpiece with the wire grid, an initial cutting speed is less than 2 mm/min, coolant flow is less than 0.1 l/h and a wire speed is greater than 20 m/s. The workpiece is then guided through the wire grid until a first cutting depth is reached, and then the coolant flow is increased to at least 2000 l/h. The cutting speed is reduced to less than 70% of the initial cutting speed between the first contact of the workpiece with the wire grid up to a cutting depth of half a diameter of the cylinder, and is then increased.