Hexagonal Crystal Wafer Traceability Using Internal Laser History Marks
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Solution Overview
Problem
The existing methods for producing wafers from hexagonal single crystal ingots lack clear tracing of production history, making it difficult to investigate defects in devices manufactured from these wafers.
Innovation Solution
A wafer producing method that involves applying a laser beam with a focal point inside the wafer to form a production history, using a peel-off layer and a production history forming step, allowing for tracing of the ingot's production history even after device formation and division into chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wafer production methods (slicing with wire saw or laser processing) are used, then wafers can be produced from hexagonal single crystal ingots, but the production history cannot be traced and defect investigation is difficult
Solution Approach 1:
The invention applies laser beams to form production history information inside the ingot before the wafer slicing process. This preliminary action ensures that the production history is recorded in the bulk material, so it remains intact and traceable even after the ingot is sliced into multiple wafers and subsequently into device chips.
Solution Approach 2:
The invention creates a copy of production history information by using laser beams to write data directly into the ingot material. This laser-marked information serves as a permanent record that travels with the material through all subsequent processing steps, enabling traceability without adding external tags or markers that might be lost.
2Loss of information
If laser processing is used to form production history, then traceability is improved, but the laser beam must pass through the wafer requiring precise focal point control inside the wafer
Solution Approach 1:
The invention replaces mechanical marking methods with laser beam processing. Instead of physically contacting or tagging the wafer, the laser beam optically modifies the material to create permanent production history records. This substitution enables non-contact, precise, and programmable information storage within the wafer bulk.
Solution Approach 2:
The invention utilizes the wavelength parameter of laser beams that can pass through the wafer material. By selecting appropriate laser wavelengths and controlling the focal point depth, the system can write information at specific positions inside the wafer without damaging the surface or requiring complex positioning mechanisms.
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 reliable tracing of the production history of devices formed from hexagonal single crystal ingots, facilitating defect investigation and improving manufacturing reliability.
Implementation Method 1
applying a laser beam of a wavelength passing through the wafer with a focal point of the laser beam positioned inside the wafer
Implementation Method 2
applying a laser beam of a wavelength passing through the hexagonal single crystal ingot with a focal point of the laser beam positioned at a depth corresponding to a thickness of a wafer to be produced from an end face of the hexagonal single crystal ingot to form a peel-off layer
Data Source
AI summary
A wafer producing method includes a peel-off layer forming step of applying a laser beam of a wavelength passing through a hexagonal single crystal ingot with a focal point of the laser beam positioned at a depth corresponding to a thickness of a wafer to be produced from an end face of the hexagonal single crystal ingot to form a peel-off layer, a production history forming step of applying a laser beam of a wavelength passing through the wafer with a focal point of the laser beam positioned inside the wafer at a position corresponding to each of a plurality of devices to be formed on a front surface of the wafer to form a production history, and a wafer peeling step of peeling off the wafer from the hexagonal single crystal ingot.