SiC Wafer Thinning via Electrical Discharge Machining
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Solution Overview
Problem
The high hardness of SiC semiconductor wafers makes standard processing methods for thinning and structuring more costly and time-consuming compared to Si wafers, necessitating new methods that are less affected by material hardness.
Innovation Solution
The use of electrical discharge machining (EDM) with an assisting electrode and an intrinsic conductive layer formed on the wafer backside, allowing for voltage pulse application to thin and structure semiconductor wafers independently of their hardness, enabling efficient thinning and structuring of SiC wafers without direct physical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard processing methods are used for SiC wafers, then processing can be performed, but processing cost and time increase due to high material hardness
Solution Approach 1:
The patent replaces mechanical cutting and grinding methods with electrical discharge machining (EDM). Instead of using mechanical tools that physically contact and remove material through force, the invention uses electrical discharges (sparks) to erode the SiC wafer surface. This substitution eliminates the limitations imposed by SiC's extreme hardness, enabling efficient processing without the high costs and time consumption associated with mechanical methods.
Solution Approach 2:
The patent changes the physical state and properties of the processing system by introducing a dielectric liquid medium and applying controlled voltage pulses. By transforming the processing mechanism from mechanical to electrical, and by controlling parameters such as pulse duration, voltage amplitude, and dielectric fluid flow, the system achieves effective material removal from hard SiC wafers at improved speeds and lower costs.
2Manufacturing precision
If mechanical thinning methods are used, then material removal is achieved, but processing time increases due to high hardness
Solution Approach 1:
The patent replaces mechanical thinning methods with electrical discharge machining. The EDM process uses electrical sparks to remove material layer by layer, achieving precise thickness control without the time-consuming nature of mechanical grinding. The electrical discharge mechanism allows for controlled material removal rates that maintain precision while dramatically reducing processing time for hard SiC materials.
Solution Approach 2:
The patent employs periodic voltage pulses in the EDM process, where voltage is applied in repeated cycles rather than continuously. Each pulse creates a localized discharge that removes a small amount of material, and the periodic nature of this action allows for controlled, incremental thinning. This periodic application of energy enables precise thickness control while maintaining high processing speeds.
3Productivity
If direct contact machining is used, then material removal is achieved, but processing cost increases due to tool wear
Solution Approach 1:
The patent eliminates direct mechanical contact between the tool and the SiC wafer by using electrical discharge machining. The tool electrode generates electrical sparks that erode the workpiece material without physical contact, preventing tool wear that would otherwise occur with mechanical cutting tools. This non-contact approach maintains high material removal rates while significantly reducing tool replacement costs and processing expenses.
Solution Approach 2:
The patent introduces a dielectric liquid as an intermediary medium between the tool electrode and the SiC wafer. This dielectric fluid serves multiple functions: it facilitates the electrical discharge process, removes eroded particles from the machining zone, and cools the workpiece. By using this intermediary, the system achieves efficient material removal without direct mechanical contact, thereby reducing tool wear and processing costs.
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
EDM processes effectively thin and structure semiconductor wafers with high hardness like SiC, reducing processing costs and time by maintaining a plasma between the tool electrode and the intrinsic conductive layer, achieving precise control over material removal and surface smoothness.
Implementation Method 1
thinning the semiconductor wafer by applying voltage pulses between the electrode at the backside of the semiconductor wafer and a tool electrode positioned over the backside as part of an electrical discharge machining (EDM) process
Implementation Method 2
The dielectric liquid is pumped through the electrode at a controlled flow rate to maintain a stable plasma
Data Source
AI summary
A method of structuring and/or thinning a semiconductor wafer having a plurality of functional chip sites includes forming one or more semiconductor devices in a device region of each functional chip site at a frontside of the semiconductor wafer, and forming an electrode at one of the frontside or a backside of the semiconductor wafer. The side of the semiconductor wafer at which the electrode is formed is structured by applying voltage pulses between the electrode and a tool electrode positioned above the semiconductor wafer as part of an electrical discharge machining (EDM) process before the electrode is removed by the EDM process, and between the tool electrode and an intrinsic conductive layer formed on the side of the semiconductor wafer being structured after the electrode is removed by the EDM process.