iii

NICKEL PHOSPHORUS COATED SUBSTRATE MICRO-DEFECT

REDUCTION THROUGH CHEMICAL MECHANICAL PLANARIZATION

PROCESS OPTIMIZATION

NAZIM MOHD. SALEH

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Engineering (Industrial Engineering)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

JUNE 2014

v

Kepada Ayahbonda (Hj Mohd. Saleh bin Urip dan Hjh Tuminah bte Hj. Nor), terima

kasih atas segala doa, dorongan dan nasihat yang tak pernah putus.

Kepada Isteri tersayang Zainon Tugiran, terima kasih atas segala pengorbanan dan

kasih sayang yang dicurahkan dalam mengemudi bahtera kehidupan sebagai

persediaan kita ke kehidupan yang kekal abadi.

Kepada anak-anak ayah, Muhammad Fathi Hakimi, Nur Farhana Hani dan

Muhammad Fatih Irfan semoga menjadi anak-anak yang soleh dan solehah sebagai

asset berharga penyumbang bakti bagi ummah ini..

vi

ACKNOWLEDGEMENT

In preparing this project report, I was liaised with many people around me.

They contributed a lot in order to fulfill this project requirement from the beginning

of understanding problems until implementation of results. I would like to express

my sincere appreciation to my Supervisor, Dr. Jafri bin Mohd. Rohani for his

guidance and advice. I’m also very thankful to my colleagues for their support and

co-operation in order to run experiments and tests for this project. I’m very grateful

for all my family members.ur text begin here.

.

.

vii

ABSTRACT

Chemical mechanical planarization (CMP) was known as a process to gain

superfine surface finish with high precision mechanical parameters. It widely used

within semiconductors wafer manufacturing and hard disk (HDD) industries.

There’re very few research done in HDD compared with silicon wafer. Micro defect

formation caused by first step polishing in multistep polishing reducing the “good

sector” and areal density in HDD substrate platter. In this study, micro defect

reduction became the main objectives and as main response with others parameters

including material removal rate and micro waviness. A 2 level 4 factor fractional

factorial with center points Resolution IV, Design of Experiment (DOE) with total of

12 experimental runs was chosen for main effect and interaction screening purposes.

All key factors such as platen rotation speed (rpm), applied pressure (g/cm2), slurry

distribution points and slurry flow rate (ml/min) were then being optimized using

Response Surface Method (RSM) setup of a set of full factorial 4 factors with center

point, single replicate, 8 axial point and 2 alpha significance value with total 31

random runs. Results shows that all the input factors were affecting MRR and MD

count except micro waviness which not respond to all input factors applied.

Optimum input parameter setup were then established with setup of applied pressure

(103.1 g/cm2), slurry distribution points (4/5 points), slurry flow rate (381.6 ml/min)

and platen rotation speed (15.7 rpm). Predicted composite desirability gained to be

0.998, which can be satisfactory accepted. Verification runs from the parameter

setup shows and concluded that the desired MD and MRR successfully achieved

with 1.688% variation.

viii

ABSTRAK

Pensatahan Kimia dan Mekanik merupakan satu proses untuk mendapatkan

permukaan super-licin dan berketepatan ukuran mekanikal yang tinggi. Ia digunakan

dengan sangat meluas dikalangan industry semi-konduktor dan pembuat cakera keras

komputer. Bagaimanapun, terdapat kajian yang sangat sedikit dilakukan untuk dalam

bidang cakera keras berbanding semi-konduktor. Kecacatan mikro yang disebabkan

oleh penggilapan pertama didalam penggilapan berbilang tingkat telah

mengurangkan “sektor baik” dan kepadatan areal didalam piring perakam cakera

keras. Dalam kajian ini, pengurangan kecacatan mikro menjadi objektif utama dan

tindak balas output utama bersama parameter yang lainnya termasuk kadar

pembuangan bahan dan keberombakan mikro. Satu set 2 level 4 faktor faktorial

pecahan dengan titik tengah Resolusi IV, Design of Experiment (DOE) dengan

jumlah 12 eksperimen telah dipilih untuk menentukan faktor utama dan faktor

interaksi dalam proses penyaringan. Semua faktor-faktor input utama seperti

kelajuan putaran plat (rpm), tekanan permukaan (g/cm2), mata pengedaran buburan

dan kadar aliran buburan (ml/min) kemudiannya dioptimumkan menggunakan

Response Kaedah Permukaan (RSM) dengan setting 31 eksperimen, eksperimen

penuh melalui 4 faktor dengan titik tengah, 8 titik paksi dan nilai signifikan 2 alfa.

Keputusan menunjukkan bahawa semua faktor-faktor input memberikan kesan

terhadap MRR dan jumlah MD kecuali keberombakan mikro yang tidak bertindak

balas kepada semua faktor-faktor input digunakan. Parameter input yang telah

dioptimumkan kemudiannya telah dapat dibina dengan setup of tekanan permukaan

(103.1 g/cm2), mata pengedaran buburan (4/5 poin), kadar aliran buburan (381.6

ml/min) and kelajuan putaran plat (15.7 rpm). Jangkaan komposit yang dikehendaki

adalah 0.998. Parameter yang telah dioptimumkan itu kemudian telah ditentusahkan

dan satu kesimpulan dapat dibuat bahawa objektif MD dan MRR yang dikehendaki

berjaya dicapai dengan ralat 1.688%.

ix

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION iv

DEDICATION v

ACKNOWLEDGEMENTS vi

ABSTRACT vii

ABSTRAK viii

TABLE OF CONTENTS ix

LIST OF TABLES xii

LIST OF FIGURES xiii

1 INTRODUCTION 1

1.1 Background of Study

1.2 Problem Statement

1.3 Objective of Study

1.4 Scope of Study

1.5 Study Question

1.6 Significance of Study

1

1

2

3

4

4

2

LITERATURE REVIEW

2.1 Introduction

2.2 History of CMP

2.2.1. History of HDD

2.3. CMP Equipment

2.4 How CMP works

2.5 Polishing parameters

5

5

6

7

8

10

11

x

2.5.1 Pressure

2.5.2 Speed

2.5.3 Slurry Flow Rate

11

13

13

3

2.6 CMP Performance Measures

2.6.1 MRR

2.6.2 Micro-waviness

2.6.3 Micro Defect

2.7 Polyurethane pad

2.7.1 Pad Microstructure

2.7.2 Types of Pad Design

2.8 Slurry

2.9 Previous Research Findings

2.10 Research Gap Analysis

METHODOLOGY

3.1. Introduction

3.2. Theory of Experimental Design

3.2.1. Machining Parameters

3.2.1.1 Selection of Machining

Parameters

3.2.1.2 Constant Parameter &

Condition

3.2.2. Two Level Factorial Design

3.2.3. Response Variable

3.2.3.1 MRR

3.2.3.2. Micro Waviness

3.2.3.3 Micro Defect

3.3. Experiment Setup & Procedure

3.4. Research Instrument

3.4.1. Machining Equipment

3.4.2. Measuring Equipment

3.4.2.1 X-Strata XRF Machine

14

14

14

15

19

19

20

20

22

28

29

29

30

31

31

33

33

35

35

35

35

36

37

38

38

38

xi

3.4.2.2 OSA (KLA Tencor) Candela

38

4

5

ANALYSIS AND DISCUSSION

4.1. Introduction

4.2. DOE Design Experimental Result

4.2.1. MRR

4.2.2. MD

4.2.3. Micro waviness

4.3. Optimization result (RSM analysis)

4.3.1. MRR

4.3.2. MD

4.4. Optimal parameter setup

CONCLUSION AND FUTURE STUDY

40

40

41

41

45

48

52

52

56

59

62

REFERENCES 64

Appendices A-E 69-72

xii

LIST OF TABLES

TABLE NO. TITLE PAGE

1 Summary of previous research. 23

2 List of parameters selected in the experiment. 31

3 Fixed polishing parameter 33

4 Fractional factorial Res IV with center points 34

5 DOE Experiment results 40

6 Full factorial RSM CCD and results 52

7 Verification run results 60

xiii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.0 Microdefect AFM analysis fallout 2

2.0 Areal density demand over years of production 6

2.1

Head flying height decrease trend (Tomonobu

Ogasawara, Kenji Ozawa, 2008)

7

2.2

Illustration of double sided polishing (Toshi Kasai,

2008)

8

2.3

Schematic of Substrate CMP (S.Sideq, S.Izman,

2013)

9

2.4 Three body abrasion on CMP process 9

2.5

Wear rates of ferrite and copper as a function of

nominal contact pressure when using 0.5 p.m

AI2O3 particles and soft polishing pads.

(Yongsong Xie, 1996)

11

2.6

Trajectory analysis to simulate a single point on a

carrier travel during polishing (Toshi Kasai, 2008)

12

2.7

MRR vs Table rotation speed (Chu, Bai & Chen ,

2011)

12

2.8 MRR vs slurry flowrate (Chu, Bai & Chen , 2011) 13

2.9

Primary profile (top), waviness (middle),

roughness (bottom)

14

2.10

Correlation of substrate Waviness and take-off

height

15

2.11

Defects formation by impacted surface of slurry

particle

16

2.12 AFM Image of embedded particle 17

2.13 AFM image of Irregular pit defect 18

xiv

2.14 AFM image of Worm pit defect 18

2.15

Polishing pad microstructure with existence of

pores

19

2.16 Several pad groove design 20

2.17 Irregular shape alumina in slurry 21

2.18 Aluminum coated with silica 21

2.19 SiO2 Silica based slurry 22

3.0 Design of experimental flow 30

3.1

Initial setup of slurry distribution discharge point

system

32

3.2

Experiment setup of the slurry distribution

discharge point system

32

3.3 Overall experiment flow setup 37

3.4 Taiyo 11.8B CMP Polishing machine 37

3.5 XRF machine 38

3.6 KLA Tencor (Candela) 39

4.0 MRR DOE normal plot 41

4.1 Pareto chart of MRR 43

4.2 Main effect plot of MRR 46

4.3 Interaction plot of MRR 44

4.4 Normal plot for MD count 45

4.5 Pareto chart for MD count 47

4.6 Main effect plot for MD count 47

4.7 Interaction plot fr MD count 48

4.8 Pareto chart for micro waviness 48

4.9 Normal plot for micro waviness 49

4.10 Contour plot of MRR 55

xv

4.11 Surface plot of MRR 55

4.12 Contour plot of MD 58

4.13 Surface plot of MD 58

4.14 Optimization plot model 60

4.15

Excel spreadsheet thoretical calculation for

improved setting 61

1

CHAPTER 1

INTRODUCTION

1.1 Background of study

In Hard disk industries, the recording media which called substrates contains

Al-Mg disk as based and plated with thin layer of nickel phosphorus to improve

smoothness and hardness. With extreme demand of higher memory space in hard

disk, manufacturers are pushing to the higher density of substrate platter. It can be

achieved by reducing the height of the recording head to fly to strengthen the weak

and smaller signals (Lei and Luo, 2004, Lei et.al, 2009). Reduction of flying head

media needs super-smooth recording media platter to prevent head crash resulting

data loss

1.2 Problem Statement

Most of the studies in reducing Chemical Mechanical Planarization (CMP)

defects focusing on the slurry parameter such as abrasive particle size (Lei and Luo,

2004, Xie and Bushan, 1996), abrasive particle type and shape (Hong Lei et.al, 2009,

2010), oxidizing agent contents, additives to improve material removal rate and

surface quality. Recent study starts to focus on friction modifier additives in slurry

for improving surface topography and reducing surface defects (S.Sideq, S.Izman,

2013). Yong-Jin Seo, Sang-Yong Kim , Woo-Sun Lee (Yong-Jin Seo et.al, 2003)

studied about the advantage of using POU slurry filters for reducing sub-micron

2

defect of silicon wafer substrate. Heike Lauber, Sven Miinzberger (Heike Lauber,

Sven Miinzberger, 2007) focused on post-polishing parameter and DIW rinsing

optimization for CMP defect reduction for semiconductor substrate wafer. Most of

the studies focusing on semiconductor wafer. At present, very less of the approach

focusing on polishing parameter optimization for CMP defects reduction for hard

disk substrate even there are a lot of study focusing on silicon wafer substrate.

From the data collected from one of the world leading hard disk

manufacturer, from total of 32,224 defect points analyzed from 1611 substrate

surfaces it showed that highest contributor of substrate micro defect was from CMP

defect which were irregular pit and embedded particle as illustrated in Figure 1.0.

Details of irregular pit and embedded particle defect formation will be discussed in

Chapter 2 in literature review. It is mission critical to improve the micro defect count

and optimize the CMP process.

Figure 1.0: Microdefect AFM analysis fallout.

1.3 Objective of study

Objective of the study are:

1. To characterize the CMP process factors that influence to the process output

response.

3

2. To identify the main factor and interaction factor that contribute to the CMP

process response.

3. To optimize the CMP process from the experiment analysis result.

1.4 Scope of study

The scope of the study are:-

i. Polishing 2nd step of Al-Mg Nickel Phosphorus coated substrate disk, 1.27

mm thickness as work material by effect of Chemical Mechanical

Planarization.

ii. The study will be carried out using double sided Precision Polishing Machine

with polyurethane polishing pad and colloidal silica based slurry.

iii. The process input parameter to be tested are Pressure, Speed, Slurry

discharge point and Slurry flow rate.

iv. The response performance to be analyzed are material removal (MRR), micro

waviness, surface micro defect count.

v. Design of Experiment (DOE) design and analysis will be using Minitab

Release 16.

vi. Surface quality analysis will be using Atomic Force Microscopy (AFM) for

micro-defect detection scanning and count and surface topography.

This project is to study the 2nd step polishing parameters effect towards

upstream (1st step) defects removal. Assuming all slurry related parameter already

optimized including hybrid Al2SO3 slurry particle at 1st step polishing with lower

slurry particle size 0.35~0.5m, constant oxidizing agent which uses H2O2 0.5% -

1% concentration at of 1.3~1.7pH after mix and no interference from the polishing

pads parameters characteristics. This study only includes the defect formation of the

effect of 1st step polishing process and embedded particle as results of uneven

thickness removal due to imbalance between mechanical and chemical removal and

4

determination of the optimal 2nd step polishing parameter setup. This study will not

covers the post-CMP cleaning and mechanical brushing to condition or pad

conditioning.

1.5 Research Question

1. What are the optimum parameter setting for achieving the optimum substrate

CMP characteristic?

2. What are the main influence factor or interaction of the influence factor that

affecting output response of the process?

3. What is the predicted model can be generated for the output response?

4. What is the maximum variation percentage of error between experimental

and predicted for output response?

1.5 Significance of study

Since the rapid technology changing which require higher substrate areal

density which require the reduction of sub-micron defect and improvement of

surface roughness and waviness, the outcome of the study will help to increase to

improve the standards of the recording substrate to high-end product. It will also

help to assist industries to select the optimum parameter setting for the

manufacturing process.

64

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