Bond PAd mit Abheber

XPS-analysis of a defective bond­ pad

On a patterned wafer, a microscopically readily recognizable light reflection was observed in the area of a bond pad. Small spot XPS measurements on the defect bond pad (edge length 100 µm) and at a reference position were performed to clarify the cause of this issue.

In the Small spot XPS analysis overview spectra were recorded on measurement areas with a diameter of 20 µm. The exact location of the analysis positions is illustrated in figure 1. Based on the overview spectra, the element concentrations of the reference point and the defect region were quantified. The results are shown in Table 1.

 

 

Position

Si

Al

O

N

Reference

28.6

3.6

66.3

1.5

Defect

27.4

7.5

63.4

1.7

    Table 1: Concentration [at-%]

Figure 1: Bond pad with a noticeable light reflection (red circle); green circle: reference position
 

 

Results

Comparison of the XPS data listed in table 1 shows a local accumulation of aluminum as the cause of the optical anomaly. 

The fact that XPS could quantitatively determine the chemical composition on small areas was crucial ib resolving this issue. The used procedure is, of course, also applicable to other sample systems.