TiN-Rich Metal Flake Between BL and VSS-Line

TiN-Rich Metal Flake Between BL and VSS-Line

Material Name: Silicon
Record No.: 115
Primary Chemical Element in Material: Si
Sample Type: Wafer
Uses: Etching
Etchant Name: None
Etching Method: Dry etching
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: This case shows that not all metallic short type of defects induce high IDD leakage. The device is 0.25 µm process technology, 3-level metal design 1Mb synchronous SRAM with a single column failure. The device presents low IDD leakage of 40~50 µA under 2.5V constant voltage.
For this case, we used a system where a photo emission microscope was connected with a engineering memory tester -Mosaid 3490. High repetition rates with active bias condition can be more effective to locate the failure site. The result is TiN-rich metal flake between BL node and VSS-line (Fig. 1, 2). The composition of metal flake also can explain why its resistance is higher than other cases.
Reference: Cheng-Piao Lin, Cheng-Chun Ting, Chin-Hsin Tang, Cheng-Hsu Wu, Chih-Ming Kuo, Yung-Sheng Huang, Application of Various Fault Localization Techniques to Different Types of 6T-SRAM column Failures, ISTFA 2002, Proceedings of the 28th International Symposium for Testing and Failure Analysis, 3-7 November 2002, Phoenix Civic Center, Phoenix, Arizona, pp. 259-265.

Figure 1: Photoemission image occurs by active bias stress.

Figure 2: SEM image of photoemission located TiN-rich metal flake between BL node and VSS-line.