Probe Assembly Thermal Compensation for Wafer Test Alignment
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Solution Overview
Problem
Conventional probe assemblies in wafer probe stations experience misalignment errors due to temperature fluctuations, leading to inaccurate measurements, and existing solutions require complex structures and large volumes to compensate for length variations.
Innovation Solution
A probe assembly composed of components with opposing thermal expansion characteristics, such as a probe with positive expansion and a holder or adaptor with negative expansion, compensating for length changes to maintain alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional probe assemblies are used with standard materials, then the structure is simple and volume is small, but misalignment errors occur due to thermal expansion causing length changes
Solution Approach 1:
The patent applies thermal expansion principles by selecting materials with specific coefficients of thermal expansion (CTE) for different components. The probe holder uses a material with CTE of 6-12 ppm/°C while the adaptor uses a material with CTE of 18-24 ppm/°C, creating a differential expansion system that compensates for length changes and maintains alignment accuracy during temperature variations.
Solution Approach 2:
The patent employs composite material selection strategy by combining materials with different thermal expansion characteristics in the probe assembly. The probe holder and adaptor use different materials (such as Invar for the holder and stainless steel for the adaptor) to create a composite structure that compensates for thermal expansion effects, resolving the contradiction between precision and simplicity.
2Reliability
If probe assemblies are heated or cooled for temperature control, then testing quality improves, but length changes occur due to thermal expansion causing misalignment
Solution Approach 1:
The patent changes the thermal expansion parameters of different components to achieve compensation. By selecting materials with specific CTE values (probe holder: 6-12 ppm/°C, adaptor: 18-24 ppm/°C), the system allows controlled differential expansion that maintains the relative position of the probe tip to the device under test during temperature control operations.
Solution Approach 2:
The patent converts the harmful effect of thermal expansion into a beneficial compensation mechanism. The differential thermal expansion between the probe holder and adaptor materials is designed to counterbalance each other, so that the net effect maintains alignment accuracy even as temperature changes during testing.
3Stability of the object's composition
If parallel mechanical structure is used to compensate for length variation, then alignment stability improves, but device volume and structural complexity increase
Solution Approach 1:
Instead of using complex parallel mechanical structures for compensation, the patent employs a simplified approach based on differential thermal expansion of materials. The probe holder and adaptor use materials with different CTE values to automatically compensate for length variations, achieving alignment stability without increasing volume or structural complexity.
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
Ensures precise alignment of the probe tip relative to the device under test by stabilizing thermal expansion, using a simpler structure and reducing volume.
Implementation Method 1
the probe assembly, the probe system, and the method prevents misalignment errors between the probe tips of the probe assembly and the device under test caused by temperature variations
Implementation Method 2
one of the second coefficient of thermal expansion or the third coefficient of thermal expansion corresponds to either: a material having a negative coefficient of thermal expansion
Data Source
AI summary
A probe assembly includes at least one probe, a probe holder, and an adaptor. The probe is configured to include a probe tip and has a first a first length and a first coefficient of thermal expansion. The probe holder is configured to hold the probe, and has a second length and a second coefficient of thermal expansion. The adaptor is configured to attach to the probe holder, and has a third length and a third coefficient of thermal expansion. Furthermore, the first coefficient of thermal expansion is a positive coefficient of thermal expansion, and one of the second coefficient of thermal expansion and the third coefficient of thermal expansion corresponds to either: a material having a negative coefficient of thermal expansion; or a composite structure comprising a positive thermal expansion material and a negative thermal expansion material, arranged such that the overall thermal expansion characteristic is stable.