Deformable Wafer Probe with Friction Sensing

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Solution Overview

Problem

Conventional test probes face challenges in maintaining precise positioning on wafer pads over extended periods and varying temperatures, leading to misalignment and uneven electrical contact, which affects measurement accuracy in RF and switching applications.

Innovation Solution

A wafer probe alignment system with deformable test probe needles equipped with sensors to monitor friction forces and a controller that repositions the probes in real-time to maintain contact, using strain gauge bridges to measure forces and displacements, and a signal generator to evaluate and adjust the probe position based on reflected test signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional test probes are used to contact wafer pads, then initial electrical contact can be established, but the probes tend to misalign or slip off bumps over time due to lateral friction forces and probe tip drift

Engineering Contradiction:

Improvecontact stabilityVSAvoidprobe positioning accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent employs sensors (strain gauges, capacitive sensors, or optical sensors) that continuously monitor probe position and contact forces, feeding this information back to a control system. The control system adjusts probe positions in real-time to compensate for drift and maintain accurate alignment with wafer pads throughout extended testing periods.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transitions from static probe positioning to dynamic adjustment mechanisms. Motorized stages or piezoelectric actuators enable continuous realignment of probes during testing, allowing the system to adapt to thermal expansion, mechanical drift, and other time-dependent variations in probe-wafer relative positions.

Inventive Principle:

Principle #15Dynamics

2Reliability

If conventional test probes are spaced apart and angled to contact test points, then contact can be maintained, but the larger probe pitch and cross sectional area increase path inductance which is undesirable in RF applications

Engineering Contradiction:

Improvecontact maintenanceVSAvoidpath inductance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces conventional mechanical probe structures with alternative contact mechanisms such as flexure-based compliant contacts or magnetic levitation systems. These substitutions reduce the mechanical dimensions of probe components, thereby minimizing parasitic inductance while maintaining stable electrical contact for RF measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If two test probes exert different contact forces on a test point, then contact is established, but uneven tip wear and uneven scrubbing on the test point occurs

Engineering Contradiction:

Improvecontact establishmentVSAvoiduniformity of contact

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent employs compliant probe structures with uniform spring constants or actively controlled force application mechanisms that ensure equal contact forces are exerted by multiple probes on a test point. This equipotential force distribution prevents uneven wear and scrubbing, maintaining consistent contact conditions throughout extended testing.

Inventive Principle:

Principle #12Equipotentiality

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 system ensures accurate and consistent electrical contact, maintaining precise alignment and reducing wear on the probes and pads, enabling long-term measurements with improved measurement quality and reduced need for repeated tests across varying temperatures.

Implementation Method 1

the body is deformable and includes a sensing area that undergoes a deformation in response to at least one force applied to the tip

Methodology Applied

Scientific EffectDeformation: Deformation

Implementation Method 2

using strain gauge bridges to measure forces and displacements

Methodology Applied

Scientific EffectStrain measurement:

Data Source

PatentUS12019096B2Sensor-based planar wafer probe alignment

Publication Date: 2024.06.25 INFINEON TECHNOLOGIES AG

AI summary

A wafer probe alignment system includes a test probe needle including a body having a tip that is configured to make contact with a surface of a wafer at a first tip position, wherein the body is deformable and includes a sensing area that undergoes a deformation in response to at least one force, including a lateral friction force, applied to the tip; at least one sensor configured to monitor the sensing area for deformation caused by a lateral friction force and generate at least one first sensor information representative of the lateral friction force; and a controller configured to control a position of the tip, wherein the controller is configured to receive the at least one first sensor information and reposition the tip to counteract the lateral friction force in order to maintain the tip at the first tip position.