BCA developed Electronics and FPGA firmware for a subsystem for stages used in steering and focusing the beam of a Scanning Electron Microscope (SEM) used to detect defects in silicon wafers.

Context

The customer’s SEM design involved several stages which were used to steer and focus the electron beam. Each stage could be at a different potential, up to kilovolts apart. Each stage required a driver to produce voltage signals to control the stage. Additionally stage drivers needed to be near perfectly synchronized with each other. The electronics also had to have extremely low electrical noise, because slight variations could ruin the image results.

Solution

BCA worked with the customer to develop exact requirements and architect a system to meet them. The final design required BCA to develop two boards, a driver board which would serve each stage, and a common controller board. The controller board was connected to each driver board via a fiber optic link, which allowed high speed communication and electrical isolation, allowing the driver boards to be at any potential. The processing and communication required by each board was handled using an Altera Arria II GX FPGA, for which BCA developed the all the firmware. This included interfacing with internal high speed transceivers on the FPGA for the fiber optic link, developing a board to board communication protocol, and developing a debug interface for testing and manufacture. The FPGA firmware was able to achieve synchronization between boards in the tens of nanoseconds. Additionally special care was taken to minimize electrical noise in the system particularly in parts selection and layout. The resulting system far surpassed the noise requirements for the system. BCA Successfully designed, built, tested, and delivered a system which met or exceeded all the customer’s requirements.