On-Wafer Load Pull Tuner Balancing for Stable Probe Contact
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Solution Overview
Problem
Existing on-wafer load pull measurement setups face challenges with mechanical tilting and vertical movement of wafer probes due to electro-mechanical microwave tuners, leading to loss of contact and potential damage, particularly when small mechanical movements occur, and the contacting process is not securely reproducible.
Innovation Solution
An independently controllable mobile counter-weight mechanism is introduced outside the tuner housing, synchronously moving opposite to the tuner carriage to maintain system balance and control wafer probe elevation, allowing for automated and repeatable electrical contacting with DUT pads, using a large disc with belt teeth and a remotely controlled stepper motor to adjust the counter-weight's position and momentum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a mechanically coupled counter-weight is used to balance the tuner carriage, then the tilting problem is reduced, but the counter-weight mass must exactly match the carriage mass and the belt linking them becomes unreliable over longer distances
Solution Approach 1:
The patent replaces the mechanical belt coupling system with an independent electronic control system. The counter-weight mechanism is no longer mechanically linked to the carriage via a belt, but instead is controlled independently through electronic commands from the control computer. This substitution eliminates the reliability issues of the belt while maintaining the balancing function.
Solution Approach 2:
The control computer acts as an intermediary between the carriage position control and the counter-weight position control. Instead of direct mechanical coupling, the computer receives position information and independently calculates and commands the counter-weight position to maintain balance, mediating the relationship between the two components.
2Stability of the object's composition
If the counter-weight mass exactly matches the carriage mass, then mechanical balance is achieved, but the system becomes sensitive to mass variations and requires precise mechanical coupling
Solution Approach 1:
The patent transforms the static mass-matching requirement into a dynamic control system. Instead of requiring the counter-weight mass to exactly match the carriage mass, the system continuously adjusts the counter-weight position based on the actual carriage position and mass variations. This dynamic adjustment compensates for mass differences and eliminates the need for precise initial mass matching.
Solution Approach 2:
The system changes the control parameter from fixed mass matching to variable position adjustment. The counter-weight position becomes the adjustable parameter that compensates for mass variations, allowing the system to maintain balance despite differences in counter-weight and carriage masses.
3Adaptability or versatility
If the tuner carriage moves horizontally to change impedance conditions, then the tuning range is extended, but mechanical tilting causes vertical wafer probe movement leading to loss of contact
Solution Approach 1:
The patent uses a counter-weight mechanism to offset the gravitational effects of carriage horizontal movement. By positioning the counter-weight appropriately, the system compensates for the tilting moment generated during carriage movement, preventing vertical probe displacement and maintaining reliable contact with the wafer.
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 solution effectively maintains the center of gravity constant, reduces tilting, and ensures precise, reproducible contact with microchip pads, enhancing the reliability and accuracy of load pull measurements by allowing the counter-weight and carriage masses to differ, and enabling precise control over wafer probe positioning.
Implementation Method 1
an independently controllable mobile compact and mechanically simple counter-weight mechanism, moving synchronous and opposite to the movements of the carriages inside the tuner, in order a) to maintain the balance of the system by keeping the center of gravity of the assembly constant
Data Source
AI summary
A balanced on-wafer load pull tuner system includes an intelligent, independent and universal mechanical balancing and contact controlling device, supporting automatic microwave single or multi-probe slide screw tuners. It allows contacting and stable on-wafer testing of sub-micrometric devices. Ultra-low loss rigid airlines (bend-lines) used to connect the tuner with the semiconductor chips, in order to improve the tuning range at the DUT reference plane, transfer mechanical movements of the wafer probes attached to the rigid bend-lines, when the tuner mobile carriages move horizontally. A precisely controlled counter-weight allows contacting the DUT and balanced load pull operation by controlling the center of gravity of the assembly.