A novel method for determining whether substrates are correctly positioned on a substrate support in a semiconductor substrate processing or measuring tool for optimum processing or measuring of the substrates. The method includes providing a control substrate; providing alignment marks on the substrate; determining a homing position for the alignment marks on the control substrate wherein the position of the control substrate corresponds to a homing position for optimum processing or measuring of actual substrates; periodically testing the position of the control substrate on the substrate support as facilitated by the substrate transfer and/or substrate positioning equipment of the tool; and determining whether the position of the alignment marks on the control substrate, with respect to the substrate support, stray outside an accepted deviation range.