概要（Overview）

The Candela 7120 is a system that is part of the Candela 7100 and 7120 series. These systems have the unique ability to distinguish submicron pits from particles on hard disk drive (HDD) metal substrates. This is achieved through the introduction of two new scatter channels, which enhance defect detection and classification capability. The new stealth scatter channel improves the capture of submicron-height defects by reducing background noise. By comparing signals from the new normal scatter, new stealth scatter, and existing oblique scatter channels, the system can differentiate between submicron pits and particles. This is an important innovation because while particles may be cleanable, pits are not. In high sensitivity mode, the system can detect defects as small as 40nm on metal substrates.