Low-Profile Slide Screw Tuner for Millimeter-Wave On-Wafer Testing
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Solution Overview
Problem
High insertion loss and mechanical conflicts in existing passive slide screw tuners limit the tuning range and proximity to the DUT, especially in millimeter-wave on-wafer configurations, necessitating a low-profile tuner design with rotating probes and compact stepper motors to minimize these issues.
Innovation Solution
A low-profile tuner structure with a rotating tuning probe and compact stepper motors, featuring a disc-formed probe that rotates eccentrically around a vertical axis, minimizing height and insertion loss, and allowing direct in-line connection with wafer probes without additional lossy components, and a three-axis positioner assembly for precise angle adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional high-profile tuner with vertical axis and RF probe is used, then the tuner structure is stable and reliable, but the height creates mechanical conflict with the microscope and limits proximity to the wafer probe
Solution Approach 1:
The patent transitions from a vertical movement configuration to a rotational movement configuration. The tuning probe rotates horizontally around a vertical axis rather than moving vertically, changing the dimension of motion from vertical (Z-axis) to horizontal rotation (XY-plane). This dimensional change eliminates the height conflict with the microscope while maintaining tuning functionality.
Solution Approach 2:
The patent replaces the traditional mechanical vertical slide-screw system with a rotational positioning system driven by a stepper motor. This substitution eliminates the need for a long vertical travel path and complex vertical guidance mechanisms, achieving a low-profile structure while maintaining precise positioning capability.
2Ease of operation
If additional RF cables or adapters are used to connect the tuner to the wafer probe, then the connection is flexible and easy to implement, but insertion loss increases and tuning range is reduced
Solution Approach 1:
The patent merges the tuner structure directly with the wafer probe connection, eliminating intermediate RF cables and adapters. The tuning probe rotates into direct proximity with the wafer probe, creating a unified measurement path that minimizes the number of components and reduces cumulative insertion loss.
Solution Approach 2:
The patent removes the unnecessary intermediate components (RF cables and adapters) from the signal path between the tuner and the wafer probe. By extracting these lossy elements and replacing them with a direct rotational positioning system, the design reduces insertion loss while maintaining connection functionality.
3Length of moving object
If a low-profile tuner structure is used, then mechanical conflicts are reduced and proximity to wafer probe is improved, but the tuner height must be minimized which challenges traditional vertical axis design
Solution Approach 1:
The patent inverts the traditional design approach by placing the rotation axis vertically instead of having horizontal movement. The stepper motor drives horizontal rotation around a vertical axis, which is the opposite of the traditional vertical slide-screw mechanism. This inversion achieves low profile height while simplifying the mechanical design.
Data Source
AI summary
A low-profile passive slide screw load pull tuner is used on-wafer, especially in millimeter-wave frequencies from 25 to 110 GHz and above. It uses special rotating tuning probes insertable in a short slabline mounted inside the tuner housing, which holds the control gear. The tuner is mounted at an angle matching the angle of the wafer-probe, is connected directly of the wafer-probe and ensures optimum reflection factor tuning range.