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As semiconductor chip technology advances towards nanometre and sub-nanometre scales, the demands placed on metrology tools, such as scanning electron microscopes (SEMs), become exponentially more stringent. These instruments are widely used in semiconductor wafer inspection and defect detection for analysing small features, identifying defects, verifying the integrity of structures, and performing critical dimension (CD) measurements. The critical role of high voltage power supplies in semiconductor and analytical instrumentation By Hafiz Khalid, Product Marketing Director, XP Power
W hile the optics and electron of its high voltage power supply is equally, if not more, critical. The power supply provides the stable, precise voltages required to generate and control the electron beam that scans the sample. Any instability, noise, or drift in this voltage can directly compromise the SEM’s performance, leading column of an SEM are central to its function, the performance to inaccurate measurements, distorted images, and potentially faulty conclusions about the manufacturing process. The power supply challenge High resolution SEM applications, particularly in yield-sensitive semiconductor process control and defect inspection, demand extremely stable electron beams. This translates directly to stringent requirements for the high voltage power supply. Key power supply characteristics that significantly impact SEM performance include: • Low ripple and noise: voltage ripple or spike noise can distort the beam focus or scanning path, leading to blurred or inaccurate images. This distortion over the signal directly affects image quality. Achieving very low ripple and noise is crucial for detector, analytical, and medical applications
in accelerating or focusing voltages can affect dimensional accuracy and repeatability, which is critical for consistent results in semiconductor inspection. Inconsistent image quality or distortion can change over an operational shift if the stability is poor. For instance, a power supply with 70 ppm stability that drifts to 200 ppm over an eight-hour shift can provide vastly different results, potentially leading to false indicators about the manufacturing process or masking issues that were previously detectable. Precision converters are needed to maintain voltage stability over time to minimise drift and enable consistent performance over eight-hour shift patterns
• Stability over temperature:
environmental influences, specifically temperature changes, can impact voltage stability. A low temperature coefficient is necessary to ensure stable long-term operation and consistent results, regardless of temperature fluctuations • Load and line regulation: variations in the input voltage (line regulation) or changes in the load (load regulation) should not significantly alter the output voltage. Precise load and line regulation are vital for maintaining stable voltage output under varying operating
• Stability over time: long-term drift
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