Missing Metal Pillars

Missing Metal Pillars

Material Name: Silicon
Record No.: 117
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: Smaller technologies and increasing chip functionality has resulted in tightly packed devices and more stacked metal layers. For technologies between 0.25 µm and 0.14 µm, stacking packed metal layers required the combination of Tungsten plugs as interconnection and the utilization of Chemical Mechanical Polishing (CMP). “Pillar”, however, is a small metal line, which allows interlevel connections between Tungsten plugs. The size and shape of the pillar can be a yield limiting issue. The process of identification and resolution of the missing metal pillar included yield analysis, electrical and physical failure analysis, root cause analysis and the engineering coordination of photo engineering, etch process engineering, CMP engineering, integration engineering, and inline inspection. Resolving the missing pillar issue has proven to have significant contribution to yield.
Reference: Dat Nguyen, et al., Missing Metal Pillar Failure Analysis-A Plug Technology Issue, ISTFA 2002, Proceedings of the 28th International Symposium for Testing and Failure Analysis, 3-7 November 2002, Phoenix Civic Center, Phoenix, Arizona, pp. 267-272.

Figure 1: Fault isolation found missing metal pillars.

Figure 2: Pillar patterning and metallization.