influence of argon gas concentration in n -ar plasma for the … · 2017-05-05 · as their infus...

Abstract—Nitriding of p-type Si samples by pulsed DC glow

discharge is carried out for different Ar concentrations (30% to 90%) in nitrogen-argon plasma whereas the other parameters like pressure (2 mbar), treatment time (4 hr) and power (175 W) are kept constant. The phase identification, crystal structure, crystallinity, chemical composition, surface morphology and topography of the nitrided layer are studied using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. The XRD patterns reveal the development of different diffraction planes of Si3N4 confirming the formation of polycrystalline layer. FTIR spectrum confirms the formation of bond between Si and N. Results reveal that addition of Ar into N2 plasma plays an important role to enhance the production of active species which facilitate the nitrogen diffusion.

Keywords—Crystallinity, glow discharge, nitriding, sputtering.

I. INTRODUCTION

HE Si3N4 thin films show remarkable properties which make them suitable in various applications due to their

diverse properties such as high mechanical strength; dielectric constant; excellent chemical stability; good resistance to wear and corrosion; thermal shock and creep. Hence, the Si3N4 films are used as passivation layers, alkali–ion diffusion barrier, gate dielectrics, oxidation mask, hard coating materials and in high-temperature applications [1]-[3]. The Si3N4 films are synthesized through different routes like direct nitridation of silicon [4], activated reactive evaporation (ARE) [5], chemical vapor deposition (CVD) [6], plasma-enhanced chemical vapor deposition (PECVD) [7], laser-assisted CVD [8], DC reactive magnetron sputtering [3] and plasma focus device [9].

Plasma nitriding has attracted much attention because it is environmentally-friendly technique. A pulsed DC discharge is preferable over conventional DC discharge due to its operation at relatively high peak voltages and currents for the same average power as compared to conventional DC glow discharge which leads to increase the ionization, excitation and sputtering processes [10]. Plasma generated by only N2

K. Abbas is PhD scholar at Department of Physics, GC University, Lahore,

54000, Pakistan (corresponding author, phone: 0046764227525; email: [email protected]).

R. Ahmad (Chairman of Department of Physics and Director of Centre for Advanced Studies in Physics), S. Saleem (PhD scholar), and U. Ikhlaq (PhD scholar) are with the Department of Physics, GC University, Lahore, 54000, Pakistan.

I. A. Khan (Assistant Professor) is with the Department of Physics, GC University, Faisalabad, 38000, Pakistan.

gas is not suitable because its dissociation efficiencies are about 2% which is due to highly stable bonding between N2 species. One promising way to enhance the dissociation of N2 in plasma is to introduce the inert gases like Ar, neon and helium [11]. It is well known that addition of Ar in N2 plasma enhances the electron temperature, electron number density, concentration of active species through Penning excitation and ionization [12], [13]. Moreover, it is noticeable that the addition of Ar in N2 plasma serves as a catalyst enhancing the concentration of active species of N2 and increasing the reactivity of silicon with N2 plasma species to form nitrides [14], [15].

The present work highlights the importance of sputtering gas (Ar) concentrations on the kinetics of layer growth. Structural, morphological and compositional properties of the nitrided layer are examined in terms of their crystal structure, chemical bonding, and surface morphology. The role of sputtering gas on crystallite size and residual stress of silicon nitrided thin films is also investigated.

II. EXPERIMENTAL SETUP

In order to study the influence of Ar concentration in N2-Ar plasma on the nitrided layer properties, the Si samples are nitrided in a stainless steel chamber by using pulsed DC glow discharge technique. Fig. 1 shows the schematic arrangement of pulsed DC glow discharge system. The chamber consists of two movable parallel electrodes having a diameter of 9.5 cm and thickness of 1.9 cm. The upper electrode serves as anode, whereas the lower electrode serves as cathode (sample holder). The chamber is evacuated down to 10-2 mbar pressure by using rotary vane pump prior to filling the N2-Ar gases. The inter-electrode distance (3 cm), pressure (2 mbar) & power (175 W) are kept constant throughout the experiment.

By applying pulsed-DC power to the upper electrode (anode), glow discharge is produced. The pulsed DC power is obtained by using 50 Hz AC power source, step-up transformer and bridge rectifier. The plasma is excited in an abnormal glow regime using various ratios of Ar & N2.

To control the input current and voltage within the discharge, voltmeter and ammeter are used. There is no need of auxiliary heater as the sample is being heated up by the bombardment of cathodic energetic atoms, molecules, ions and radicals of N2 which may be controlled by increasing the Ar concentration in N2-Ar plasma.

Silicon substrates having dimension 1cm × 1cm and thickness 0.3 mm are placed on the cathode (substrate holder)

Influence of Argon Gas Concentration in N2-Ar

Plasma for the Nitridation of Si in Abnormal Glow Discharge

K. Abbas, R. Ahmad, I. A. Khan, S. Saleem, U. Ikhlaq

T

World Academy of Science, Engineering and TechnologyInternational Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering Vol:10, No:7, 2016

858International Scholarly and Scientific Research & Innovation 10(7) 2016 scholar.waset.org/1999.2/10004869

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http://waset.org/publication/Influence-of-Argon-Gas-Concentration-in-N2-Ar-Plasma-for-the-Nitridation-of-Si-in-Abnormal-Glow-Discharge/10004869

http://scholar.waset.org/1999.2/10004869

foArchinro

niplThdish

shaloinhuthbrofboSi

(3whinthnisualoob

thloth

or 4 hrs procesr plasma. Th

haracterized byvestigate the

oughness of the

Fig. 1 A schem

A. XRD Analy

Figs. 2-4 shtrided Si samasma by keephe XRD pattffraction pea

hown in Fig. 2 Fig. 2 (b) sh

howing weak iong with a brtensity of Si (

ump, which inat crystallite

roadening. Thuf nano-crystaombardment oi lattice. The peak int01), (204) & hich starts to dicates that Ae growth of Strided layer.

ubstrate tempeong other oriebserved thereb

It has been re addition of wer electron cat provides ad

ssing time usihe untreated y XRD, FTIRe structural,e silicon nitrid

matic diagram of

III. RESULTS

ysis

how the XRDmples for diffeping the othetern of untreaak correspond

(a). ows the develintensities relaroad diffractio(100) is drastindicates the ame size is inus, the broadeallites of Sof N active sp

tensity of Si3N(103) orientadecrease for

Ar contents greSi3N4 but re-spMoreover, lo

erature hindersentations. For by confirming reported that ef argon gas [1collision crossdequate time

ing various coSi and nitrid

R, OM, SEM a, morphologde layers.

f pulsed DC glo

S AND DISCUSS

D patterns offerent Ar concr discharge pated Si show

ding to Si (1

lopment of twated to Si3N4 (3on peak of (10ically decreasmorphization nversely propened peaks exi3N4 which

pecies as well

N4 phase growtions increase

r 70% to 90%eater than 60%puttered the power nitrogens the nucleatio90% argon, nothe formation

electron tempe16], [17]. This-section of Arfor electrons t

oncentrations ded Si sampleand AFM in orgical and s

ow discharge sy

SION

f untreated Scentration in

parameters conws a single i100) orientati

wo diffraction 301) & (204) 03) plane. Theed showing a of Si. It is reportional to xhibit the form

are due toas their infus

wing along difes up to 60% % Ar contents% is not favorabpreviously depn content or on of silicon no diffraction p

n of amorphouerature increas may be owr as comparedto be accelera

of N2-es are rder to surface

stem

Si and N2-Ar nstant. ntense ion as

peaks planes e peak broad

ported peak

mation o the sion in

fferent argon,

s. This ble for

posited higher nitride peak is s film. ses by

wing to d to N2 ated in

the enermolmaythemactiionsnitro

TcurrThenitropartimpfavoincrdiffunitri(higmaxindiprodto mtherconreas

diff

electric field rgetic electronlecules or briny collide withm. Hence, Penve species cons cause more sogen ions, wh

The argon conrent which is e argon gas aogen through ticles-moleculpact [20] whiorable for nitreases, the spfusion of nitride films. On

gher reaction ximum but theicating that thduce significamore collisiorefore hinderscentration of son.

Fig. 2 The XRDferent N2-Ar con

and results inns may direcng Ar to its mh nitrogen monning excitationcentration insputtering of t

hich increases ntents and enresponsible f

also contributeelectron-mole

les impact anich also incrtriding procesputtering rate rogen resultinthe other hanrate), the n

e formation ohe high sputteant reaction beons, plasma ss the growthavailable nitr

D patterns of unncentrations (a)

n high energyctly ionize anmetastable statolecules and on and ionizatn the dischargetarget materiathe discharge

nergies influenfor the growthes in moleculecule impact dnd heavy partreases the dess. As the argincreases wh

ng in the formnd, during highnucleation of of amorphous ering yield isetween the plaspecies have h of crystallirogen (10%)

ntreated and nitr) Untreated Si (b

y electrons. Tnd excite nitrotes. As a resuionize and ex

tion event enhe. Energetic al in comparisocurrent [18], [nce the dischh of nitride lalar dissociatiodissociation, hticle-solid surensity of radgon concentra

hich facilitatesmation of silher sputteringSi3N4 shouldfilm (for 90%

s not favorablasma species.

low energy ine films or may be the o

rided Si layer fob) 70%N2 + 30%

These ogen

ult, it xcite

hance argon on to [19]. harge ayer.

on of heavy rface

dicals ation s the licon

g rate d be %Ar) le to Due and low

other

or %Ar



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coFig. 3 The XR

oncentrations (aRD patterns of na) 60%N2 + 40%

+ 60%Ar (d)

itrided Si layer %Ar (b) 50%N2

30%N2 + 70%A

for different N2

2 + 50%Ar (c) 4Ar

2-Ar 40%N2

F

T

growinflu

B

FordelayeoveGau

Fnitriup apressuffsurfionssurftheiatomsubsvalucrys

Fig. 4 The XRDconcentration

The XRD resuwth and the duenced by the

B. Residual Str

Figs. 7-9 repreer to calculater and crysrlapped diffr

ussian distribuFig. 5 demonsided layers byand down shifsence of resificient amounface by s/electrons/radface temperatuir growth. ms/molecules/strate lattice wues will changstal structure a

D patterns of nitrns (a) 20%N2 +

ults indicate thdevelopment oe variation of N

ress Analysis

esent the de-cte the residuatallite size.

raction peaksution function. strates the resy using XRD dfting from theidual stressesnt of energy

the bomdicals results ure which cau

The in/radical interswhich changesge the lattice pand surface mo

rided Si layer fo 80%Ar (b) 10%

hat the nucleatof residual strN2-Ar concent

convolution ofal stress induc

The de-cons has been

sidual stressesdata. The diffreir stress free ds. During nitis transferred

mbardment in the incre

uses to nucleatncorporation stitially causes the d-values.parameters reorphology of t

or different N2-A%N2 + 90%Ar

tion of Si3N4, resses are dirtrations.

f XRD patternced in the ninvolution of

performed u

s developed inraction peaks sdata indicatingtriding procesd to the subs

of energease of subste new phases

of impes to distort This change

esults in changthe nitrided lay

Ar

their ectly

ns in itride

the using

n the show g the ss, a strate getic strate s and urity

the in d-ge of yers.



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Fi

temboexdostracin

whsp(S

[2

layfrofrococosilofof(1traobtraArva(2

plco

ig. 5 Variation i It is well k

mperature anombardment cxpansion coeffown-shifting ress results ductual residual the nitride lay

here do and dpacing. The mSi3N4) gives th

The elastic c25].

Fig. 5 exhibyers show theom 30% to 80om -7.80 GPoncentration inoncentration wlicon substratef silicon tempef new phases. 03), (301) ansformed to bserved in thansformed to r. However, dalues (Fig. 6). 204) and (301)

It is concludanes of Si3N

oncentrations i

in residual stres

known that thnd lattice dischange the inficients [21]. Tof diffraction

ue to up-shiftinstress can be yer, given by [

ɛ =

d are the obsmultiplication he value of resi

Residual str

constant (E) o

bits the residue cyclic behav0%. It is founPa to 3.85 n N2-Ar plasmwhich increase surface. Thierature whichFor 30% Ar,

planes are tensile for

he above mencompressive s

different diffraFor 80% Ar, planes are ag

ded that the sN4 phases stroin N2-Ar plasm

ss using differen

he increase instortion deventer-atomic diThe tensile strn planes whng of diffractiestimated by [23]:

served and stof strain wi

idual stress [2

ress = ɛ * E

of Si3N4 is fou

ual stresses dvior for Ar co

nd that the resiGPa with th

ma. This is duses total eneis, in turn, res

h will increase, the stresses compressive 40% Ar. Th

ntioned diffrastress which iaction planes hthe compressi

gain transformestress transforongly dependma.

nt argon concen

n substrate seloped duringistance and thress develops hereas comprion planes [22the strain pro

tandard value ith elastic co4].

und to be 400

developed in oncentration ridual stress chhe increase ue to increaseergy deliveransults in the ine the nucleatiodeveloped in in nature

he tensile straction planes increases up tohave differentive stresses ined to tensile. rmation in difd on increasin

ntration

surface g ions hermal due to

ressive 2]. The oduced

(1)

of d-onstant

(2)

0 GPa

Si3N4 ranged hanges of Ar in Ar nce to ncrease on rate

Si3N4 which

ress is again

o 70% t stress n Si3N4

fferent ng Ar

C

Tbe c

whe1, dradithe Bra

Fi

Fconthe stro(204maxchanobsebroatren

Itdiffuatomcondiffubroaplan

C. Crystallite S

The average crcalculated from

C

ere k is a consdepending on iation (1.5406

correspondinagg's angle.

ig. 6 The variati

Fig. 6 illustratcentration in Naverage crys

ongly depends4) plane is mximum for 60nge in the crerved with inadening of d

nd with variatit is well knfusion and spms of Ar andcentration, hig

fusion of N2

adening. It wne with increa

Size Analysis

rystallite size m XRD data u

Crystallite size

stant having a the cell geoºA), FWHM

ng diffraction

ion of crystallitepla

tes the variatN2-Ar plasmastallite size o on Ar conceminimum for% Ar concentrystallite size

ncreasing Ar cdifferent diffron in Ar conc

nown that theuttering proced N2. Moreogher will be tspecies and r

will decrease tsing Ar conce

of the siliconusing Scherer's

=

value in the rometry. λ is tis the full wid

n peak, and

e size with Ar casma

tion of crystaa. It can be cleof different

entration. The r 50% Ar, wtration. Intere

e of (103) diconcentration. raction planesentration. ere is a comesses by the ver, higher t

the nucleationresults in the the crystallite

entration [26]-

n nitride layers formula

ranged from 0the wavelengtdth half maximθ (radian) is

concentration in

allite size withearly observeddiffraction plcrystallite siz

whereas it isestingly, a littliffraction plan

It means thas shows diffe

mpetition betwenergetic ion

the energetic n which affects

increase of e size of diffe[28].

r can

(3)

0.9 to th of ma of s the

n N2

h Ar d that lanes ze of s the le bit ne is at the ferent

ween ns or

ions s the peak

ferent



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FFig. 7 De-convoolution of the ovverlapped diffraaction peaks usi

ing Gaussian disstribution functtion for (a) 70%%N2 + 30%Ar (b

b) 60%N2 + 40%%Ar



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FFig. 8 De-convoolution of the ovverlapped diffraaction peaks usi

ing Gaussian disstribution functtion for (a) 50%%N2 + 50%Ar (b

b) 40%N2 + 60%%Ar



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F

coFi

Fig. 9 De-convo

D. FTIR Analy

The FTIR aompositional aig. 10 elabora

olution of the ov

lysis

analysis provand vibrationaates the FTIR

verlapped diffra

vides informaal properties of

spectrum of

action peaks usi

ation regardinf the nitrided lSi3N4 film ni

ing Gaussian di

ng the layers. itrided

for 4It

concom

istribution funct

40% N2 and 6t is also reportent; even s

mposition resul

tion for (a) 30%

60% Ar concerted that the Sismall oxygenlting in the for

%N2 +70%Ar (b)

ntration. i–N bond is sen content crmation of SiO

) 20%N2 + 80%

ensitive to oxyhanges the ON film instea

%Ar

ygen film

ad of



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Sipo

reElthefinovatolen

Fi

gris mSicmthobvibspthby

mdiunarobdibu12nodiwi

i3N4 film whicosition toward

The vibrationlated to the lectron cloudse more elect

ffect is knowcorporated in

ver Si-N bonoms, which angth.

g. 10 The FTIR

The vibratio

roup shows a battributed to t

mode [29], [32i–N peak in Sm−1. The Si–Ne reported v

bserved at abobrational bon

pectrum of Si3Neir energy rep

y the Ar conce

E. OM Analys

Figs. 11 anmagnifications)

fferent N2-Antreated Si anre significantlybserved in thfferent in diffe

ubbles of irreg2 (a), a crackodules [33] is ffusion rates with Si. The r

ch is responsibds higher waven frequency electronegati

s in a bond tetronegative atwn as inductn the nitrided nds. Nitrogen are more elec

R spectrum of si60% A

onal frequencbroad Si–N bothe asymmetri]. Vila et al. Si3N4 films li

N peak appearvalue [5]. Mout 771, 820 and. It is examiN4 film that th

presented by bentration in N2

sis

nd 12 show of untreated

Ar plasma. d nitrided filmy different. Thhe film. Howferent nitrided gular diameterk free film cobserved. Thwhich increas

results show t

ble for the she number [5]. of a chemicaivity of the end to orient tom involved tion effect. layer producatoms are re

ctronegative d

licon sample niAr plasma

y associated ond at about 7ic Si–N bond-[30], [31] havies in the ranrs at 873 cm−1

Moreover, smand 840 cm-1 arined from thehe number of ond strength a

2-Ar plasma.

the optical md and nitridedThe surface ms for differehe pores of di

wever, the nufilms along w

rs. For 60% Acovered with

his is due to hise the reactionthat one can

ifting of Si–N

al bond is dnearest neig

themselves toin the bond

So, oxygen ces induction eplaced by o

decreasing the

itrided for 40%

with the bo771–985 cm−1

-stretching vibve reported thnge from 7001 matches welall overtones/re attributed toe FTIR transm

emission bandare strongly af

micrographs d sample of

morphologient Ar concentfferent diamet

umbers of porwith the formatAr illustrated ih large numbigher sputterinn possibilities obtain a par

N bond

directly ghbors. owards . This atoms effect

oxygen e bond

N2 and

onding which

bration hat the 0–1200 ll with /peaks

o Si–N mission ds and ffected

(×500 Si for es of tration ter are re are tion of in Fig. ers of ng and

of N2 rticular

surfcon

F

Fand nitridiffthe 40%nanin Flayethe the obseit iAddAr cthe appdiffuWe plasincrand

Tinfousedconimacan

whetrea

FIt icon

WspecincrsuffFor the maxpartspec

G

Tdiffoutlsurf

face morpholocentration in N

F. SEM Analys

Figs. 13 and 14d nitrided layeided layer in

ferent shapes aformation of

% Ar, netwoparticles spaFig. 13 (c). Her is comparatsurface morphAr concentr

erved for 60%is smooth coditionally, totaconcentration deposited filmearance and

fusivity of N2

hypothesize tsma enhances reases the ioni

d results in the The SEM crossormation aboud to calculatecentration. Us

age and by usinbe obtained [3

ere d is the tatment time. Fig. 15 shows ts found that centration.

With increasincies and electreases the suficient to nuclthe samples tactive speci

ximum but duticles decreasecies in Si lattic

G. AFM Analys

The AFM imferent Ar conlook appearanface morpholo

ogy of the nitrN2-Ar plasma.

sis

4 show the surers. For 30% ndicates the fand size and rough surfac

work microsarsely spread inHowever, the tively low. A chologies of nitration. Moreo

% Ar as clearlyomparatively ally surface ashowing the f

m is compact inroughness

along the graithat the increa

the diffusionization and conchange in sur

s sectional vieut the film thice the diffusionsing the thickng the relation34].

Diffusion r

thickness of t

the relation bethe diffusion

ng Ar concentron number dubstrate templeate the Si3Nthat are nitridies and elecue to collisiones which in tuce.

sis

mages of untrncentration arnce of the Aogy depends on

rided film dep.

rface morpholAr, the surfacformation of the up and doe as shown instructure is n the backgrou

surface rougcareful investitrided layers sover, highly y shown in Fi

for 70% Aappearance is formation of lon nature. Thisis due to tin boundary sasing Ar concn rate of N2 inncentration of

rface microstruew of the nitridckness. The filn rate of N2 wkness data fron given below

rate = d2/t

the nitrided la

etween the difn rate strongl

ntration, the density increaperature. Thi

N4 around the ed at 70-90%

ctron numberns, energy (te

urn decreases t

reated Si andre shown in

AFM images n Ar concentr

pending on th

logies of untrece morpholognano-particle

own regions sn Fig. 13 (b).

observed und as represeghness of nitrigation revealsstrongly depenrough surfac

ig. 14 (a), wheAr concentrat

changed for ong nano-rodss change in surthe differencesites and Si latentration in Nn Si lattice wf the active speucture. ded layer givelm thickness (with increasingom cross-secti

w, the diffusion

ayer, and t is

ffusion rates oy depends on

number of ases, which in is temperatur

grain boundaAr concentra

r density reaemperature) ofthe diffusion o

d Si3N4 filmsFigs. 17-20. confirms thatation.

he Ar

eated gy of es of show . For with

ented rided s that nd on ce is ereas ions. 90%

s and rface e in ttice.

N2-Ar which ecies

es the (d) is g Ar ional n rate

(4)

s the

f N2. n Ar

ctive turn

re is aries. ation, aches f the of N2

s for The

t the



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Fiig. 11 The opticand nitrided Si

60

cal micrographsi samples (a) Un0%N2 + 40%Ar

s (Magnificationntreated Si (b) 7r (d) 50%N2 + 5

n×500) of untrea70%N2 + 30%A50%Ar

ated Si Ar (c)

Figsg. 12 The opticasamples (a) 40%

al micrographs (%N2 + 60%Ar (b

80%Ar (d) 10

(Magnification×b) 30%N2 + 70%0%N2 + 90%Ar

×500) of nitride%Ar (c) 20%N2

ed Si 2 +



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FFig. 13 The SEMand nitrided Si

M micrographs (a) Untreated S

40%Ar (d) 5

(×5000 MagnifSi (b) 70%N2 + 350%N2 + 50%A

fication) of untr30%Ar (c) 60%

Ar

reated %N2 +

Fig(a)

g.14 The SEM m) 40%N2 + 60%

micrographs (×5%Ar (b) 30%N2 +

10%N2 +

5000 Magnifica+ 70%Ar (c) 20+ 90%Ar

ation) of nitride0%N2 + 80%Ar

d Si r (d)



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Fi

didragdiin

conimco

ig. 15 Diffusion

For 30% to 7fferent height

roplet heights.greed well wstribution of t N2-Ar plasmaThe size of s

oncentration wtrided layers.

morphology anoncentration. M

Fig. 17

n rate of nitrogentreatme

70% Ar concets are observ Therefore, thwith the SEthese dropletsa. solid droplet which increaThe present

nd surface rouMoreover, the

7 The AFM ima

n as a function ent time 4 h

entration, the ved. There is he nitrided filmEM analysis. s depend on th

increases withases surface work highligughness are researchers h

ages of untreated

of Ar concentra

vertical dropa small chan

m which is ro The heighhe Ar concent

h increasing troughness o

hts that the sassociated wi

have pointed o

d Si and Si3N4 f

ation at

lets of nge in

ough is ht and tration

the Ar of the surface ith Ar ut that

the dep

InagaiwhiAddgrowredusurf

Tcon

Fig.

films for differe

nucleation aend on Ar conn the presentin confirm theich are attribuditionally, forwth rate and uced which is face, which prThe variation centration in N

. 16 The surface

ent Ar-N2 plasm

and growth rncentration [35t work, the Xe nucleation auted with ther 90% Ar surface roughdue to higher

rovides the smin surface r

N2-Ar plasma

e roughness of tAr conc

ma. (a) Untreated

rate of nitride5]. XRD, SEM aand growth rate increase of concentrationhness of the r sputtering ra

mooth growth oroughness wiis shown in F

the nitrided Si ficentration

d Si (b) 70%N2

ed layer stro

and AFM anate of nitrided fAr concentra, the nucleanitrided layer

ate of the subsof nitrided layeith increasingig. 16.

films as a functio

+ 30%Ar

ongly

alysis films ation. ation, r are strate er. g Ar

on of



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F

F

Fig. 18 The AFM

Fig. 19 The AFM

Fig. 20 The AF

M images of Si

M images of Si

FM images of Si

i3N4 films for di

i3N4 films for di

i3N4 films for di

ifferent Ar-N2 p

ifferent Ar-N2 p

ifferent Ar-N2 p

plasma. (a) 60%

plasma. (a) 40%

plasma (a) 20%N

N2 + 40%Ar (b

N2 + 60%Ar (b

N2 + 80%Ar (b)

b) 50%N2 + 50%

b) 30%N2 + 70%

) 10%N2 + 90%

%Ar

%Ar

%Ar



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IV. CONCLUSIONS

The present work highlights that the active species generations (argon as sputtering gas) play an important role in the nitriding of silicon using 100 Hz pulsed DC glow discharge. The XRD results confirm the formation of Si3N4 films. The intense polycrystalline Si3N4 film is formed at 40% N2 and 60% Ar plasma. The FTIR result highlights the formation of asymmetric Si3N4 film and the bond strength between Si and N species strongly depends on argon concentration in N2-Ar plasma. The OM microstructure reveals the formation of nodules which are associated with the nucleation and growth of the nitrided layer. The SEM microstructure results show the formation of hills of nano-clusters of Si3N4 films. The AFM images relate the surface roughness of the nitrided layers formed for different Ar concentrations in N2-Ar plasma. The peak–to-valley height (166.21 nm) is maximum for 60% Ar concentration. It is concluded that the crystallinity, crystallite size, residual stresses, bond strength, surface morphology, particle shape and size, particle distributions, formation of hills of clusters and cluster of nanoparticles are associated with Ar concentration in N2-Ar plasma. Up to 60% Ar concentration in N2-Ar plasma is most suitable for the nitriding of silicon due to the production of large number of active species and higher temperatures are achieved.

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