This paper presents a fast method for descrambling verification of a flash array using an IR laser. The basic effect of how the flash cell reacts to the irradiation is studied first; and then, it is shown how to take advantage of this reversible effect to quickly verify the descrambling of the flash array of a modern microcontroller. The goal of this study is to find a way to deliberately affect the programming state of a specific flash memory cell, so the altered state can be read out by standard test equipment and be correlated to the physical position of the cell. Information on the mechanism of Fowler Nordheim tunneling, ONO-tunneling, hot electrons, and laser-induced hot electron injection is provided. The application for fast descrambling of a NVM array is shown.

There are two known failure mechanisms that cause Gate Disturb failures in flash devices. One main electrically classified failure is the Gate Disturb failure. A second mechanism is the Floating Gate charging caused by high energetic electrons, so-called channel hot electrons, jumping above the energetic barrier of tunnel oxide. This paper describes the characterization of a single transistor Flash cell with the nano-probing approach and introduces a test algorithm to distinguish between these mechanisms at a Gate Disturb affected Flash cell. A Keithley parameter analyzer in combination with Atomic Force Probing (AFP) has been used for the Flash cell device characterization. A Gate Disturb defect can be induced by different defect mechanisms. Two of them, TRAP's in tunnel oxide and channel hot electrons as a result of leaky PN-junctions, were identified as the main root causes. These mechanisms can be distinguished by AFP-analysis with the tests presented in the paper.