Molten Polysilicon Filaments

Molten Polysilicon Filaments

Material Name: Silicon
Record No.: 176
Primary Chemical Element in Material: Si
Sample Type: Wafer
Uses: No data
Etchant Name: None
Etching Method: No data
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: For all the ESD stressed ICs, the defect is always localized on the drain side of the GGNMOS gate contact. A SEM image obtained after removing the silicon oxide by plasma etching shows two holes at the gate and silicon substrate level (Figure 1). The presence of these holes is explained by the preferential etching of ESD induced polysilicon filaments. These filaments originate from the gate. They extend into the silicon substrate thus partially short-circuiting the gate to drain p-n junction. This “weak point” in the protection structure was also confirmed on several protection test structures.
Reference: Félix Beaudoin, et al., Laser Beam Based ESD Defect Localization in ICs, ISTFA 2002, Proceedings of the 28th International Symposium for Testing and Failure Analysis, 3-7 November 2002, Phoenix Civic Center, Phoenix, Arizona, pp. 543-551.

Figure 1: SEM image of the GGNMOS gate contact after plasma etching revealing two molten polysilicon filaments.