The Department of Electrical and Electronic Engineering
Final Year Project
Final Report
Project I.D. number: SJK2-02
Project Title:
Packaged and Wafer Level Semiconductor Failure Analysis
Supervisor: Prof. Johnny K.O. Sin
Project Team Member:
Tso Kwok Piu, Jason
(01148108)
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Li Hou Hang, Leo
(01148005)
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Failure analysis (FA) plays a very important role in the IC production cycle
and its goal is t o det er mine t he r oot cause of f ailur e so t hat corrective
action can be taken.
I n or der t o f ind out t he f ailur e of an I C, many pr ocesses need t o be
performed and these processes form the FA flow. In this project, the last
process of the FA flow
physical analysis consisting of the cross-section
and f ace lapping t echniques, see Figur e 1, is our f ocus because it st ill had
plent y of r ooms f or impr ovement while ot her s had alr eady been well
developed.
The aim of t his pr oj ect was t o develop a highly ef f ect ive and highly
efficient procedure for the cross-section stage and the face lapping stage
r espect ively and our obj ect ive was t o use t hese t wo t echniques t o obt ain
the cross-section view of the device and the top view of the circuit of the
f ailur e par t of t he I C in or der t o do pr ocess development and r ever se
engineering of the semiconductor products.
Cross-section
Procedure
Face lapping
Procedure
Figure 1: Die before and after cross-section and face lapping procedures
Firstly, the cross- section and face lapping procedures were analyzed in order
to find out the factors that affected their efficiency and effectiveness. Next,
the effects of these factors were explained using some theories in Phyiscs. The
explanations were then verified by conducting different experiments.
II nn ccrroossss-- sseeccttiioonn,, tthhee ff aaccttoorrss w
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Die alignment
Correction of alignment errors during grinding
Choice of polishing methods
Choice of etchants in stain etching
Direction of the die placement relative to the rotational direction of the
grinding wheel
Placement of the die on the grinding wheel
Maximum rotational speed of the grinding disc for each diamond film that
can withstand
Choice of combinations of diamond lapping films
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Distribution of the additional force
Alignment of the polishing plane of the die
Grinding orientation of the die relative to the rotational direction of the
grinding wheel
The removal of the layer of passivation of the die
Choice of the rotational speed of the polishing wheel
Choice of the polishing cloths
By conducting different experiments, the explanations of the effect of these
factors were verif ied and t he best value or choice of t hese f act ors were
determined using the suggested explanations and the cross sectional view and
the top view of a die can be obtained.
After performing the cross-section and face lapping procedures, the cross
sectional view and the top view of a die were obtained and they were shown
in Figure 2 and 3.
Via connecting
metal 3 and metal 2
Passivation
Metal 3
Contact connecting
metal 1 and polysilicon
Metal 1
Bare silicon
Metal 2
Silicon oxide between
metal 3 and metal 2
Polysilicon
Figure 2: Image of the cross sectional view of a die after cross-section
Same
position
B
B
A
B
A
A
Metal 2
Metal 3
D
C
D
Via
C
Silicon Oxide
Metal 3
C
Metal 2 under Silicon Oxide
Via connecting Metal 3 and Metal 2
D
Metal 1 under Silicon Oxide
Met al 2
Figure 3: Images of the top view of a die and the Via connection between
Metal 3 and Metal 2
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