Semiconductor EDM Using Photoconductive Illumination at Lower Voltage

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Solution Overview

Problem

Conventional electrical discharge machining (EDM) is unsuitable for semiconductors due to their low electrical conductivity, making it difficult to machine materials like silicon carbide effectively, especially at lower voltages and without direct illumination.

Innovation Solution

An EDM process that illuminates the semiconductor workpiece with light near its bandgap energy to increase conductivity, allowing electrical discharge at practical voltages, using an illumination system that can direct light to specific locations within the workpiece to enhance conductivity and facilitate machining, including the use of sub-bandgap energy photons for multi-photon absorption to stimulate transitions and increase local conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional EDM is used on semiconductor workpieces, then the machining process can be applied to conductive materials, but the process fails due to insufficient electrical conductivity of semiconductors

Engineering Contradiction:

ImproveEDM process reliabilityVSAvoidelectrical conductivity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent changes the electrical conductivity parameter of the semiconductor workpiece by illuminating it with light. The illumination causes photoexcitation of charge carriers, transitioning the semiconductor from a low-conductivity state to a high-conductivity state, enabling EDM to proceed reliably

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces light as an intermediary substance between the voltage source and the semiconductor workpiece. The light acts as a mediator that modifies the electrical properties of the semiconductor, enabling the EDM process without directly participating in the material removal

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If high voltage is used to achieve electrical discharge in semiconductors, then conductivity can be increased, but the complexity and cost of the voltage source increases

Engineering Contradiction:

Improveelectrical discharge capabilityVSAvoidvoltage source complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary illumination to the semiconductor workpiece before initiating the EDM process. This preliminary action of light exposure pre-increases the conductivity of the semiconductor, allowing subsequent electrical discharge to occur at lower, more practical voltages

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the need for high-voltage electrical systems with an optical system (illumination source). Instead of using complex high-voltage electronics to force conductivity, the system uses light to optically induce conductivity, substituting an optical mechanism for an electrical one

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If direct illumination is applied to the machining surface, then conductivity increases at the surface, but light cannot penetrate sufficiently into the workpiece for subsurface machining

Engineering Contradiction:

Improvesurface conductivityVSAvoidlight penetration depth

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent applies excessive illumination intensity to compensate for light absorption. By providing more than the minimum required light energy, the system ensures sufficient photons penetrate to the desired depth while also saturating the surface conductivity, achieving both surface and subsurface effects

Inventive Principle:

Principle #16Partial or excessive action

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

Enables EDM of semiconductors at lower voltages with improved machining performance and reduced surface roughness, allowing for practical generation of electrical discharges using conventional voltage sources and indirect illumination.

Implementation Method 1

The workpiece is illuminated by an illumination system. The illumination system is configured to illuminate the workpiece with light that is near a bandgap energy of the semiconductor material of the workpiece. photons incident on the semiconductor workpiece excite electrons from a first energy state in a valence band of the semiconductor to a second energy state in a conduction band of the semiconductor

Methodology Applied

Scientific EffectPhotoconductivity: Photoconductivity

Implementation Method 2

an electrical discharge between an EDM tool and a conductive workpiece is stimulated. The electrical discharge causes material to be selectively removed from the workpiece at a location depending upon positioning of the EDM tool

Methodology Applied

Scientific EffectElectrical discharge machining: Electrical Discharge Machining

Data Source

PatentUS20230395381A1Electrical discharge machining of semiconductors

Publication Date: 2023.12.07 NIELSON SCIENTIFIC LLC

AI summary

An electrical discharge machining system includes a semiconductor workpiece, a voltage source, an EDM tool, and an illumination system. The illumination system is configured to illuminate the semiconductor workpiece in order to increase the conductivity of the semiconductor workpiece. The voltage source establishes an electric potential difference between the workpiece and the EDM tool while the illumination system illuminates the semiconductor workpiece. The electric potential difference is such that an electrical discharge occurs between the workpiece and the EDM tool, thereby removing material from the workpiece.