Alignment Mark Trench Depth for Thick-Layer Position Detection

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Solution Overview

Problem

In the manufacturing of high voltage or high power electronic devices, the alignment marks on thick process layers often get obscured, requiring additional process steps to transfer the original mark to the top layer, complicating the lithographic process.

Innovation Solution

A method is developed to design alignment marks with trenches on the substrate, where a relation between the height variation of a probationary layer and its thickness is determined, allowing for the configuration of the mark's depth to ensure visibility by an alignment system, thereby reducing the number of process steps needed to transfer the mark to a thick layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the process layer thickness is increased to achieve desired device performance, then the device performance is improved, but the alignment mark becomes obscured and disappears

Engineering Contradiction:

Improvedevice performanceVSAvoidalignment mark visibility

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The invention transitions from detecting alignment marks in the planar (2D) domain to detecting them in the vertical (3D) domain. By measuring height variation of the process layer surface relative to the substrate, the alignment system can detect marks even when they are covered by thick process layers, thus resolving the contradiction between thick layer requirements and mark visibility.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The invention replaces the traditional optical reflection-based detection mechanism with a height measurement mechanism. Instead of relying on optical contrast from the alignment mark itself, the system measures the physical height difference of the process layer surface caused by the underlying alignment mark structure, enabling detection through thick layers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Difficulty of detecting and measuring

If additional process steps are added to transfer the alignment mark to the top of the thick process layer, then the alignment mark visibility is improved, but the process complexity increases

Engineering Contradiction:

Improvealignment mark visibilityVSAvoidprocess steps

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The invention extracts the alignment mark detection function from the planar optical domain and relocates it to the vertical height domain. By measuring the height variation of the process layer surface, the system can detect alignment marks without requiring additional mark transfer process steps, thus reducing process complexity while maintaining visibility.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention creates a height-based copy or representation of the alignment mark information at the process layer surface. The height variation pattern on the process layer surface mirrors the underlying alignment mark structure, allowing the alignment system to detect the mark position through this height-based copy without needing to physically transfer the mark itself.

Inventive Principle:

Principle #26Copying

3Difficulty of detecting and measuring

If the alignment mark trench depth is increased to maintain mark visibility through thick layers, then the mark visibility is improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvealignment mark visibilityVSAvoidtrench depth control

Core Design Contradiction:

Difficulty of detecting and measuringVSManufacturing precision

Solution Approach 1:

The invention uses a moderate trench depth that is sufficient to create detectable height variation but not excessively deep. By measuring the height variation of the process layer surface rather than directly detecting the trench bottom, the system achieves adequate visibility through thick layers without requiring extreme trench depths that would demand ultra-high manufacturing precision.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The invention changes the detection parameter from direct optical reflection (which requires deep trenches for visibility through thick layers) to height variation measurement. This parameter change allows the use of moderate trench depths while maintaining visibility through thick process layers, thereby reducing manufacturing precision requirements.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12259664B2Method of designing an alignment mark

Publication Date: 2025.03.25 ASML NETHERLANDS BV

AI summary

A method of configuring a mark having a trench to be etched into a substrate, the method including: obtaining a relation between an extent of height variation across a surface of a probationary layer deposited on a probationary trench of a probationary depth and a thickness of the probationary layer; determining an extent of height variation across the surface of a layer deposited on the mark allowing a metrology system to determine a position of the mark; and configuring the mark by determining a depth of the trench based on the relation, the extent of height variation and the thickness of a process layer to be deposited on the mark.