Wafer Probe Alignment Control via Seal Ring Current

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Solution Overview

Problem

The challenge in semiconductor wafer testing is ensuring the correct alignment and positioning of test probes on pads made of hard metals, which is difficult due to the lack of visible signs after contact, leading to production inefficiencies and increased costs.

Innovation Solution

An automatic electric testing method using control probes to check the alignment by applying a current through a pair of control pads, providing a preliminary test to estimate the correct positioning of other probes, and utilizing additional control pads placed outside the seal ring for enhanced sensitivity and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If visual inspection methods are used to check probe alignment, then the checking process can be performed, but it occurs after testing and is not preventive, leading to production losses

Engineering Contradiction:

Improvealignment checking reliabilityVSAvoidproduction time loss

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements preliminary alignment checking using control pads before the actual testing process. The method performs a preliminary electric test on control pads to verify probe positioning correctness in advance, preventing misaligned probes from contacting sensitive pads during production testing. This eliminates the need for post-testing visual inspection and prevents production losses by catching alignment issues beforehand.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If traditional visual inspection is used to detect probe alignment, then alignment can be checked, but it is difficult when pads are made of hard metals as no visible signs appear after contact

Engineering Contradiction:

Improvealignment detection precisionVSAvoidalignment detection difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent replaces the mechanical/visual inspection system with an electrical detection system. Instead of visually examining physical marks left by probe contact on hard metal pads, the method uses electrical tests on control pads to detect alignment issues. The electrical measurement system overcomes the limitation of hard metal surfaces that do not show visible contact signs, providing reliable alignment detection through electrical properties rather than mechanical marks.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces control pads as intermediary elements for alignment detection. These dedicated control pads serve as mediators between the probe positioning system and the detection system. By routing alignment verification through these intermediary control pads with appropriate electrical characteristics, the system can detect probe positioning accuracy without directly examining the hard metal pads that lack visible contact signs.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the number of probes is reduced to match or equal the number of pads, then resource usage is optimized, but ensuring correct positioning becomes more critical and difficult

Engineering Contradiction:

Improvetesting efficiencyVSAvoidprobe positioning precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent segments the pad structure into two distinct types: functional pads for actual device testing and control pads for alignment verification. This segmentation allows the system to maintain a reduced probe count for productivity while dedicating specific control pads to monitoring and verifying probe positioning precision. The separated control functions ensure that even with fewer probes, positioning accuracy is maintained through continuous electrical monitoring on control pads.

Inventive Principle:

Principle #1Segmentation

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 method allows for a completely automatic and reliable checking of probe alignment, reducing production losses and economic damage by preventing passivation breakages and ensuring accurate electric connections.

Implementation Method 1

applying a current through a pair of control pads, providing a preliminary test to estimate the correct positioning of other probes

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9823300B2Process for controlling the correct positioning of test probes on terminations of electronic devices integrated on a semiconductor and corresponding electronic device

Publication Date: 2017.11.21 STMICROELECTRONICS SRL

AI summary

An electrical check executed on wafer tests for the correct positioning or alignment of the probes of a probe card on the pads or bumps of the electronic devices integrated on the wafer. A signal is applied to cause a current to circulate in at least part of a seal ring of at least one of the electronic devices. In a case where the current flows between and through multiple electronic devices, the seal rings of those electronic devices are suitably interconnected to each other by electronic structures that extend through the scribe line between electronic devices.