Laser Marking Uniformity in Semiconductor Wafers

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Solution Overview

Problem

Existing laser marking methods for semiconductor wafers face challenges due to thickness variability of the device layer, leading to unpredictable and unreadable marks, as the interaction of the laser with the semiconductor structure results in inconsistent spot size and appearance, making it difficult for automated readers to identify the markings.

Innovation Solution

The method involves selecting a buried structure thickness equal to k×λlaser/(2×n), where λlaser is the wavelength of peak emission, k is an integer greater than zero, and n is the index of refraction for the buried structure, to optimize laser marking by reducing interference and ensuring uniformity of marks regardless of device layer thickness variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If laser marking is performed on semiconductor wafers with variable device layer thickness, then marking can be applied to existing wafers, but the markings become unpredictable and unreadable due to interference effects

Engineering Contradiction:

Improvemarking applicabilityVSAvoidmarking legibility

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent changes the optical parameter (laser wavelength) to match the physical parameter (buried layer thickness) through the relationship λlaser = 2×n×d/k. By selecting a laser wavelength that satisfies this equation for the given buried layer thickness, the interference effects are eliminated and consistent markings are achieved regardless of device layer thickness variations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical approach of physically adjusting or selecting wafers based on thickness with an optical approach. Instead of mechanically controlling wafer thickness to achieve readable markings, the method uses optical wavelength selection to achieve the same goal, substituting mechanical precision requirements with optical parameter matching.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If device layer thickness is controlled to ensure readable markings, then marking legibility improves, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvemarking legibilityVSAvoidthickness control

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of controlling device layer thickness to ensure readable markings, the patent changes the approach by controlling the buried layer thickness and selecting the laser wavelength accordingly. This parameter substitution eliminates the need for tight device layer thickness control while maintaining marking legibility.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces the buried layer as an intermediary element that mediates between the device layer and the laser marking process. By making the buried layer thickness the controlling parameter and matching it with the laser wavelength, the system achieves readable markings without requiring precise control of the device layer thickness.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If laser wavelength is selected based on buried layer thickness, then marking uniformity improves, but additional measurement and selection steps are required

Engineering Contradiction:

Improvemarking uniformityVSAvoidwavelength selection process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent establishes a universal relationship (λlaser = 2×n×d/k) that can be applied to any buried layer thickness. Once this relationship is established, the same principle can be used across different wafer batches and production runs, reducing the need for complex case-by-case wavelength selection and enabling standardized marking procedures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 results in improved legibility, machine-readability, and uniformity of laser markings, reducing the impact of device layer thickness variations and facilitating the use of semiconductor wafers in automated fabrication processes.

Implementation Method 1

A laser beam can be used to locally melt the material and thereby a visible 'spot' was produced

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

A laser beam can be used to locally melt the material

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 3

the interaction of the laser with the semiconductor structure results in inconsistent spot size and appearance

Methodology Applied

Scientific EffectOptical interference: Interference

Implementation Method 4

n is the index of refraction for the buried structure

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS9355965B2Semiconductor devices and methods of making the same

Publication Date: 2016.05.31 SEMICON COMPONENTS IND LLC

AI summary

In one embodiment, methods for making semiconductor devices are disclosed.