Composite Wafer Alignment Marks for Precise Die Orientation

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Solution Overview

Problem

Existing semiconductor wafers face challenges in precise alignment during manufacturing, particularly in process control monitoring and die singulation, due to insufficient optical contrast and inaccuracy in aligning probe needles with existing alignment marks.

Innovation Solution

A composite alignment mark is introduced on the semiconductor wafer, comprising two portions of differing materials, one conductive and one insulating, which provide sufficient optical contrast to facilitate accurate alignment and orientation in three-dimensional space, enabling precise positioning and preventing incorrect die selection during processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single-material alignment mark is used on the semiconductor wafer, then the alignment mark can be formed with simple structure and manufacturing process, but the optical contrast is insufficient leading to inaccurate alignment and orientation during manufacturing processes

Engineering Contradiction:

Improvealignment accuracyVSAvoidalignment mark structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The alignment mark is constructed using composite materials with different optical properties (conductive and insulating materials). This composite structure provides sufficient optical contrast for accurate alignment while maintaining a relatively simple geometric configuration. The different materials absorb and reflect light differently, creating distinct visual signatures that enable precise optical detection and measurement during manufacturing processes.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different portions of the alignment mark are made from different materials with specific local properties. The conductive material portion and insulating material portion each have tailored optical characteristics that contribute to the overall optical contrast. This local differentiation of material properties within the alignment mark structure enables accurate optical detection without requiring complex overall geometry.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If existing alignment marks are used for process control monitoring, then the manufacturing process can proceed with standard tools, but the probe needles cannot be accurately placed on the auxiliary structures due to insufficient alignment precision

Engineering Contradiction:

Improveprobe needle placement accuracyVSAvoidprocess control monitoring accuracy

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The alignment system transitions from mechanical alignment methods to optical alignment methods. The composite alignment mark provides distinct optical signatures that can be detected by optical measurement tools, enabling non-contact, high-precision alignment. This optical substitution allows for accurate probe needle placement and reliable process control monitoring without the limitations of mechanical alignment systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The different materials in the composite alignment mark exhibit different optical properties including variations in light absorption, reflection, and contrast. These optical differences create distinct visual signatures that can be easily detected by optical measurement tools, enabling accurate alignment and orientation detection during process control monitoring and probe needle placement operations.

Inventive Principle:

Principle #32Color changes

3Measurement precision

If a composite alignment mark with multiple materials is used, then sufficient optical contrast is achieved for accurate alignment, but the manufacturing process becomes more complex with additional material deposition and structuring steps

Engineering Contradiction:

Improveoptical detection accuracyVSAvoidalignment mark fabrication process

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The fabrication of the composite alignment mark is merged with the existing metallization structure formation process. The conductive and insulating materials used in the alignment mark are the same materials already being deposited for device interconnects. By combining the alignment mark formation with standard metallization steps, the patent achieves accurate optical detection without significantly increasing manufacturing complexity, as the same deposition and structuring tools and processes are utilized.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20230282596A1Semiconductor wafer and method for fabricating a semiconductor wafer

Publication Date: 2023.09.07 INFINEON TECH AUSTRIA AG

AI summary

In an embodiment, a semiconductor wafer includes a front surface, a plurality of active component positions, and at least one composite alignment mark arranged on the front surface and indicating a unique orientation of the semiconductor wafer. The composite alignment mark includes a first portion that has at least one raised section formed of a first material and a second portion that is positioned laterally adjacent the first portion. The second portion has at least one raised section formed of a second material that is different form the first material.