Radio Frequency Integrated Circuit Design - Webs

The Use and Design of Passive Circuit Elements in IC Technologies
C oxide = �o �r A
h
8.85 × 10
=
−12 C 2
2 � 3.9 � 2.3 mm � 20 �m
N � m
5 �m
= 317.6 fF
The underpass must be taken into account here as well:
C underpass = � o � r A
h
8.85 × 10
=
−12 C 2
2 � 3.9 � 76 �m � 20 �m
N � m
3 �m
= 17.4 fF
Now we must consider the interwinding capacitance:
C IW = �o �r A
d
8.85 × 10
=
−12 C 2
2 � 11.9 � 2.3 mm � 3 �m
N � m
= 241 fF
3 �m
The dc resistance of the line can be calculated from
R dc = �L
Wt
= 3 �� �cm � 2.3 mm
20 �m � 3 �m
= 1.15�
The skin effect will begin to become important when the thickness of the
metal is two skin depths. This will happen at a frequency of
f =
�
���
2 =
3 �� �cm
� � 4� × 10 −7 2 = 3.38 GHz
� (1.5 �m)
Let us ignore the resistance in the underpass. Thus, above 3.38 GHz the
resistance of the line will be a function of frequency:
�L
R ac( f ) =
Wt −� W − 2√ �
�f���H − 2√ �
�f��
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