| High precision motion is critical in the semiconductor industry and as feature size continues to decrease, the need for higher precision increases. This dissertation presents the control system design and integration of a novel multiple degree-of-freedom (DoE) precision stage for nano-manufacturing. It is composed of a 6 DoE wafer holder and a 3 DoE module holder. The modules can be chosen for a desired task, such as a nano-imprint lithography module. Capacitance gauges, interferometers, and photo detectors provide position feedback of the stage. Piezo-electric actuators and linear motors, that produce two orthogonal forces each, produce the desired output. Modeling of the coordinate transformation among the spaces of sensors, stage position, and actuators along with dynamic modeling of the stage is presented. Controller design, hardware, and software is described and results comparing simulation and implementation show a closed-loop root-mean-square (rms) positioning of .57 nm error in the in-plane axial direct ions with a sensor noise level of less than 0.1 nm rms.;This dissertation also addresses commutation laws of linear motors for multiple-motor systems. By exploiting the redundancy of motor coils and motor force generation, that exist in over-actuated motion platforms, we propose a commutation law which generates the required forces while minimizing the effect of coil heat generation on thermal distortion at the motion platform work space. To realize the commutation laws in real-time, an iterative solution, using an interior-point method, is described and shown to solve this problem in under 35 microseconds, within the cycle of our system running at over 9 kHz sampling rate. |
