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Micropositioning and Fiber-Alignment

The probing of optical semiconductor devices often has to be done with an optical fiber positioned at the point of highest optical emissivity or sensitivity. For this purpose we have developed our micropositioning systems MIPO - consisting out of fast piezo translators, electronics and a real timer controller. Depending on the application, the systems achieve alignment times of a few hundred milliseconds with a position accuracy of up to 1µm.

The supply of the device under test (DUT) and the measurement at the position of optimal light coupling is normally done with precise standard test equipment as laser diode controllers and SMUs. However, during the alignment process the outputs of the DUT are bypassed to our own electronics in order to gain short measurement times.

The mechanical parts are adapted to the specific application of our customers, depending on the available dimensions and the size of the search window. Below we describe some field tested sample applications. Moreover, we have built further solutions, that are used by our customer, including systems with light coupling from the bottom side of the wafer or integration of optical lens systems.

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Description

System for the fully automated alignment of an optical fiber. Field of application is the probing of laser diodes. Therefore the unit is integrated into a wafer probe station. The single mode fiber is aligned , so that an optimal coupling of the emitted laser beam into the single mode fiber is achieved. The search algorithm is implemented on a intelligent, real time PC board. A high frequency contacting system is completing the system.

Specifications Manual adjustment of the fiber bracket in X, Y and Z-direction Fiber bracket can be completely displaced and swung in again without any position offset. Computer controlled fine alignment of the optical fiber in XY-direction in a range of ±180µm. Accuracy of position: ±1µm Duration of complete search ca. 400ms Optical lens system for coupling the laser beam into a single mode fiber Contacting of the DUT by a HF-Probe mounted onto a probe card, customizable Measurement electronics for fast reading of the optical power during search, adaptable to the application requirements. Intelligent PC board for real-time measurements and controlling DLL-Interface for 32bit-Windows for integration into tester application Software for execution and visualization of surface scans, also useful for configuration and diagnostics.

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Description

System for the fully automated positioning of an optical fiber during wafer probing. Mechanics are optimized for applications with very small distances between contact pins and optical active area of the DUT. Therefore, fiber holder and HF contacting system are mounted onto two separate, parallel mounted brackets. The position of the fiber is aligned to the optimal position for coupling the laser beam of a vcsel into the fiber. The search algorithm is implemented at a intelligent real time PC card.

Specifications Manual adjustment of the fiber bracket in X, Y and Z-direction Fiber and probe head bracket can be completely displaced and swang in again without any position offset. Computer controlled fine alignment of the optical fiber in XY-direction in a range of ±100µm. Accuracy of position: ±1µm Duration of complete search ca. 400ms Optical lens system for coupling the laser beam into a single mode fiber Contacting of the DUT by a HF-Probe including adjusted edge detectors, customizable Measurement electronics for fast reading of the optical power during search, adaptable to the application requirements. Intelligent PC board for real-time measurements and controlling DLL-Interface for 32bit-Windows for integration into tester application Software for execution and visualization of surface scans, also useful for configuration and diagnostics.

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