Models for Bridging Defects Test and Diagnosis - Models in Hardware Testing - page 39

Fig. 2.5 Schematic
representation of a basic test
comb-string-comb structure.
A bridging defect has been
included between comb C 1
and the string

S 1

C 2

C 1

bridging defect

S 2

Fig. 2.6 Measurement of single bridges with the corresponding uncertainty interval ( Rodrıguez-
Monta nes et al. 1992 )

manufacturing process. The length L of the wire follows from the line/space pitch
and the test structure area, which is chosen such that the required defect density
resolution is obtained at wafer or lot level.
The test monitor permits the identification of single bridges making a connec-
tion between the string and one of the combs (Fig. 2.5 illustrates the example of a
bridging defect between the string and comb C 1 ). The resistive nature of the bridg-
ing defect is easily characterized ( Rodrıguez-Montanes et al. 1992 , 1996 ) with the
measurements of the resistance between each comb and the two end points of the
string, provided the total resistance of the string is known.
Rodrıguez-Montanes et al. ( 1996 ) analyzed 400 defective monitors made of
metal 1 from different batches and production lines and found the resistance dis-
tribution shown in Fig. 2.6 . More detailed information about the resistive values and
their uncertainty intervals is shown in Tables 2.1 and 2.2 .
From the above results, the majority of the bridging defects (64.5%) has a re-
sistance below 500 , even considering the worst case error analysis. On the other