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Leak Location Identification Using Conductive AFM

[As of April, 2011]

Purpose
With the introduction of low dielectric constant film (hereafter "low-k film") into ULSI, leakage between metallization due to poor organic and inorganic film adhesion and Cu and barrier metal dispersion in the low-k film has become problematic. Prompt failure analysis and identification of leakage locations are now required. To this end, leakage locations were identified using a conductive AFM.
Analysis
A Cu/Low-K film sample was prepared in the form of a 30 µm² chip using FIB and fixed onto a conductive substrate. Bias voltage was applied to the sample stage, the current between the stage and probe was measured, and the leak location was identified from the current and shape images obtained.
Result
Fig 1 shows the atmospheric conductive AFM measurement results of the Cu/Low-k film. The black areas are locations of high leakage current flow and low resistance. The organic film was found to readily produce current due its low resistance value in comparison to the SiO₂ and inorganic films. In addition, leakage was confirmed to occur from the entire organic film region. From the above, it was speculated that because organic film has higher permeability and absorbability than other films, the water in the organic film reduces the film's resistance value.

This is [Figure 1 Cu/Low-k Film Conductive AFM Measurement Results].

Figure 1 Cu/Low-k Film Conductive AFM Measurement Results

Note: Bibliography. Moriyama, 51^st Japan Society of Applied Physics Meeting (2004 Spring)