Numerical assessment of floor and active isolation platform vibrations induced by wafer transporting carts under raised-floor irregularities in electronics factories

Abstract

This study aimed to assess the microvibrations on the production floor and explore the vibration control performance of the active isolation platform (AIP) installed on a moving front opening unified pod (FOUP)-transporting cart (FOUP-TC) carrying fragile silicon wafers. The goal is to reduce floor microvibrations and FOUP vibrations during transportation across the perforated raised-floor irregularities in electronics fabs. Furthermore, an integral tailored AIP-cart-floor model simulated by a half-vehicle model traversing on a simply supported floor system was proposed to effectively assess the FOUP vibrations in FOUP-TCs on the AIP and microvibrations of the production floor underneath the FOUP-TCs. Moreover, the active control forces of the AIP were calculated using the direct output feedback control algorithm. In addition, the vibration responses of the proposed model considering different tire stiffnesses and moving speeds under raised-floor irregularities were analyzed using the state-space procedure (SSP). The simulation results demonstrated that the FOUP-TCs considering a proper flexible tire stiffness as an isolation scheme and incorporating an AIP could reduce the floor microvibrations to meet the required vibration level and effectively suppress the bouncing and pitching vibrations of FOUPs to potentially mitigate the wafer notch misalignment during transportation, maintaining the production yield rate and reducing huge economic losses in semiconductor fabs.