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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) ee_tkpab

Li Hou Hang, Leo (01148005) ee_lhh

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Failure analysis (FA) plays a very important role in the IC production cycle

and its goal is t o det ermine 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 ailure of an I C, many processes 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 Figure 1, is our f ocus because it st il l had

plent y of r ooms f or improvement while ot hers had already been well

developed.

The aim of t his proj 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 to 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 order t o do process development and reverse

engineering of the semiconductor products.

Figure 1: Die before and after cross-section and face lapping procedures

C r o s s -s e c t i o nP r o c e d u r e

F a c e l a p p i n g

P r o c e d u r e

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Firstly, the cross- section and face lapping procedures wereanalyzed in order

to find out the factors that affected their efficiency andeffectiveness. Next,

the effects of these factors were explainedusing some theories in Phyiscs. The

explanations were then verified by conducting different experiments.

III nnncccrrr ooossssss--- ssseeecccttt iiiooonnn,,, ttt hhheee fff aaacccttt ooorrr sss wwweeerrr eee:::

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

III nnn fff aaaccceee lllaaappppppiiinnnggg,,, ttt hhheee fff aaacccttt ooorrr sss wwweeerrr eee:::

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 the best value or choice of t hese f actors were

determined using the suggested explanations and the cross sectional view and

the top view of a die can be obtained.

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Afterperforming 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.

Figure 2: Image of the cross sectional view of a die after cross-section

Metal 3 Via connecting Metal 3 and Metal 2 Met al 2

Figure 3: Images of the top view of a die and the Via connection between

Metal 3 and Metal 2

P a s s i v a t i o n

M e t a l 2

M e t a l 3

P o l y s i l i c o n

M e t a l 1

S i l i c o n o x i d e b e t w e e n

m e t a l 3 a n d m e t a l 2 B a r e s i li c o n

V i a c o n n e c t in g

m e t a l 3 a n d m e t a l 2

C o n t a c t c o n n e c t in g

m e t a l 1 a n d p o l y s i li c o n

D

AA

BB

C

C

D D

A

B

C

Metal 3

Via

Metal 2

Silicon OxideMetal 2 under Silicon Oxide Metal 1 under Silicon Oxide

Same

position

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