Dielectric Alignment Marks for Laser Liftoff Wafer Packaging

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Solution Overview

Problem

Existing semiconductor packaging technologies face issues with alignment mark interference during the laser liftoff process, leading to uniformity problems and failure of the chemical mechanical polishing process due to the use of metal alignment marks.

Innovation Solution

Employing dielectric alignment marks embedded in a silicon substrate, which are optically transparent to the laser energy, allowing for the laser liftoff process to proceed without interference and enabling easy removal of sacrificial dielectric layers through polishing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If metal alignment marks are used on the carrier substrate, then alignment precision for bonding semiconductor dies is improved, but the laser liftoff process is blocked and CMP uniformity deteriorates

Engineering Contradiction:

Improvealignment precisionVSAvoidlaser blocking and CMP uniformity issues

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces permanent metal alignment marks with temporary dielectric alignment marks that are removed after serving their alignment purpose. The dielectric marks are formed on the carrier substrate to enable precise die bonding, then removed via HF dip before the laser liftoff process, allowing the carrier to be cleanly removed without interference.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the material parameter of alignment marks from metal to dielectric material. This material parameter change allows the alignment marks to be transparent to the laser wavelength used in the liftoff process, eliminating laser blocking issues while maintaining alignment functionality during bonding.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If alignment marks are placed below the liftoff layer to avoid laser interference, then laser liftoff process uniformity is improved, but alignment mark visibility for bonding alignment deteriorates

Engineering Contradiction:

Improvelaser liftoff process uniformityVSAvoidalignment mark visibility

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent positions alignment marks in a different spatial dimension - on the top surface of the carrier substrate rather than embedded below the liftoff layer. This dimensional change allows alignment marks to be accessible for optical alignment during bonding while the laser liftoff process acts on the bottom surface of the carrier, eliminating interference between the two functions.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent introduces a dielectric layer as an intermediary between the carrier substrate and the liftoff layer. This dielectric layer contains the alignment marks and serves as a temporary structure that enables both alignment functionality and clean laser liftoff, mediating between the conflicting requirements of alignment visibility and laser process uniformity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If CMP process is used to remove remaining films after laser liftoff, then complete carrier substrate removal is improved, but CMP uniformity deteriorates due to metal alignment marks

Engineering Contradiction:

Improvecarrier substrate removalVSAvoidCMP uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent uses temporary dielectric alignment marks instead of permanent metal marks. These dielectric marks are removed by a brief HF dip process before laser liftoff, eliminating the need for uniform CMP across the entire surface. The carrier substrate is then removed by laser liftoff without CMP interference, and any remaining dielectric residues are easily removed by the HF dip.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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

The dielectric alignment marks facilitate successful laser liftoff and subsequent polishing, ensuring the integrity of the semiconductor dies and enabling the formation of reconstituted wafers compatible with further bonding processes.

Implementation Method 1

decoupling the reconstituted wafer from the carrier substrate at an interface using a laser source

Methodology Applied

Scientific EffectLaser liftoff: Laser Ablation

Implementation Method 2

Each of the plurality of alignment marks may comprise a material optically transparent to a wavelength of an optical energy of the laser source

Methodology Applied

Scientific EffectOptical transparency: Refraction

Data Source

PatentUS12610845B2Method for forming semiconductor packages using dielectric alignment marks and laser liftoff process

Publication Date: 2026.04.21 TOKYO ELECTRON LTD

AI summary

A method for making forming a semiconductor package comprises forming a plurality of alignment marks in or on a carrier substrate; positioning and bonding a plurality of semiconductor dies to the carrier substrate based on the plurality of alignment marks; further processing the plurality of semiconductor dies into a reconstituted wafer; and decoupling the reconstituted wafer from the carrier substrate at an interface using a laser source. The alignment marks are interposed between the interface and the laser source.