effect of multi-polar magnetic field on the properties of … · 2016. 8. 17. · kim et al. effect...

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Copyright American Scientific Publishers

RESEARCH

ARTIC

LE

Copyright copy 2009 American Scientific PublishersAll rights reservedPrinted in the United States of America

Journal ofNanoscience and Nanotechnology

Vol 9 7440ndash7445 2009

Effect of Multi-Polar Magnetic Field on the Properties ofNanocrystalline Silicon Thin Film Deposited by

Internal-Type Inductively Coupled Plasma

Hong Bum Kim1 Hyoung Cheol Lee2 Kyong Nam Kim2 Se Koo Kang1 and Geun Young Yeom123lowast1Sungkyun Advanced Institute of Nano Technology (SAINT) Suwon 440-746 Korea

2Department of Advanced Materials Science and Engineering Sungkyunkwan University Suwon 440-746 Korea3The National Program for Tera-Level Nanodevice hawolgok-dong Sungbuk-ku Seoul 136-791 Korea

An internal linear-type inductively coupled plasma (ICP) source with multi-polar permanent magnetswas used to deposit nanocrystalline silicon thin films on a large-area substrate (470 mmtimes370 mm)and the effects of a magnetic field on the characteristics of the plasma and deposited film wereinvestigated By applying the magnetic field it was possible to obtain a high-density plasma of28times 1011 cmminus3 at 15 mTorr Ar and 4000 W of RF power which is about 50 higher than wasobtained for the source without the magnetic field The application of the multi-polar magnet fieldto the ICP source during the deposition of silicon film using SiH4H2 also increased the depositionrates of the silicon thin films and the ratio Hlowast

SiHlowast which transformed the structure of the silicon

films deposited on the glass substrates from amorphous to nanocrystalline Furthermore the use ofthe magnetic field increased crystalline volume fraction and dark conductivity while decreasing theabsorption coefficient The improved characteristics were related to the increase in the ionizationrate and the dissociation rate of SiH4H2 which confined the plasma to the chamber volume andavoided losses to the chamber wall The decrease in the absorption coefficient of the nanocrystallinesilicon film deposited with a higher H2 percentage and with the magnetic field present is also relatedto the increase in the crystallization volume fraction At 70 H2 with the magnetic field present thenanocrystalline silicon thin films had a high crystalline volume fraction (68) a dark conductivity of34Eminus7 minus1cmminus1 a deposition rate of 10 Arings and grain sizes of approximately 15 nm

Keywords Plasma Enhanced-Chemical Vapor Deposition Nanocrystalline Silicon Thin FilmMagnet Internal-Type Antenna OES Inductively Coupled Plasma

1 INTRODUCTION

Nanocrystalline silicon thin films have been studied inten-sively for application to large-area thin film electronicssuch as photovoltaic devices and thin film transistors(TFTs) for flat panel displays (FPDs)1ndash4 These thin filmsare usually grown with plasma enhanced chemical vapordeposition (PECVD) using silicon-containing gas mixturessuch as SiH4 and H2 To increase the photovoltaic con-version efficiency and to improve the mobility of TFTdevices it is necessary to produce nanocrystalline sil-icon films with higher crystallization percentages butan increase in the crystallization percentage is generallyaccompanied by a lower deposition rate and especially at

lowastAuthor to whom correspondence should be addressed

lower substrate temperatures lower crystallization percent-age is obtained at the same deposition rate Therefore toincrease the crystallization percentage or to obtain higherdeposition rates at lower substrate temperatures whendepositing nanocrystalline silicon thin films researchershave investigated a variety of high-density plasma sourcessuch as electron cyclotron resonance (ECR) plasma heli-con wave plasma and inductively coupled plasma (ICP)for the PECVD of silicon films5ndash7 Of these sources ICPsources in particular have been studied extensively becauseof their simple physics and the fact that they can easily bescaled to a large size One internal linear-type ICP sourcethe ldquodouble comb-type ICP sourcerdquo has been investi-gated for the production of especially large thin films upto 2750 mmtimes 2350 mm for application in large-areaFPDs8

7440 J Nanosci Nanotechnol 2009 Vol 9 No 12 1533-4880200997440006 doi101166jnn20091771


Copyright American Scientific Publishers RESEARCH

ARTIC

LE

Kim et al Effect of Multi-Polar Magnetic Field on the Properties of Nanocrystalline Silicon Thin Film

Magnetic fields have been used with various plasmasources to improve the properties of the plasma9ndash11 Eventhough an internal linear-type ICP source can generatehigh-density plasmas by itself the addition of a multi-polartype magnetic field to the internal-type ICP source can fur-ther increase the plasma density and the dissociation rateby increasing the path length of energetic electrons andby confining the plasmas in the chamber In fact when aninternal linear-type ICP was employed for silicon etchingusing reactive gases the addition of a magnetic field to theinternal linear-type ICP not only increased the etch ratebut also improved the etch uniformity on the substrate12

In this study we used a double comb-type internal ICPsource with a multi-polar magnetic field for the deposi-tion of nanocrystalline silicon and investigated the effectsof the magnetic field on the characteristics of SiH4-basedplasma Besides investigating such deposition characteris-tics as the deposition rate and uniformity we studied theeffects of the multi-polar magnetic field on the propertiesof nanocrystalline silicon thin films It is believed that amagnetic-field-enhanced ICP source can increase plasmadensity and plasma uniformity which implies that the useof our plasma source for the deposition of nanocrystallinesilicon should increase the uniformity of the depositednanocrystalline silicon as well as the crystallization per-centage of the deposited silicon at low temperatures

2 EXPERIMENTAL DETAILS

Figure 1 shows a schematic diagram of the experimentalapparatus used in the experiment To deposit the nanocrys-talline silicon thin films we designed a rectangular plasmaprocessing chamber with inner dimensions of 1020 mmtimes830 mm that held substrate with dimensions 470 mmtimes370 mm Samples were loaded onto the substrate holder invacuum through a loadlock chamber The antenna for the

Fig 1 The double comb-type internal linear ICP and the multi-polarmagnet used in the experiment

internal linear-type ICP was made of 10 mm-diameter cop-per tubing inside quartz tubing that was 15 mm in diameterand 2 mm in thickness A series of five linear antennaswas embedded in the process chamber with the antennasconnected to an RF power supply (1356 MHz) througha matching network in an alternating fashion in order toform a ldquodouble comb-type antennardquo A multi-polar mag-netic field was applied by inserting permanent magnetseach with 3000 G on the magnet surface in the quartztubing located above and parallel to the linear internalantennas as shown in Figure 1 The plasma characteristicswith and without the magnetic field were measured usinga Langmuir probe (Hiden Analytical UK ESP) for ArCorning 1737 glass was used for the substrate and to

grow nanocrystalline silicon thin films SiH4 diluted byH2 was fed into the chamber with the operating pres-sure maintained at 20 mTorr RF power to the ICP sourcewas fixed at 4000 W while the substrate temperature wasmaintained at 180 C While deposition process was pro-ceeding an OES (PCM 420 SC-Technology) was used tomeasure the dissociated species in the SiH4H2 plasmaTo evaluate the crystalline volume fraction of the films atthe deposition thickness of 4000 Aring (plusmn200 Aring) we usedRaman spectroscopy (Kaiser Optical System Inc) Theabsorption coefficient and the dark conductivity of the4000 Aring thick films deposited were investigated as a func-tion of the H2 percentage in SiH4H2 by an ultraviolet-visible (UV-Vis) spectrometer (Scinco S-1000) and bya semiconductor characterization system (Keithley 4200)respectively after the formation of Al coplanar electrodeson the deposited nanocrystalline silicon The activationenergy (Ea) of charge carriers was calculated from thetemperature-dependent dark conductivity measurementsThe nanostructure of the deposited hydrogenated siliconthin film was observed using high resolution transmissionelectron microscopy (HRTEM JEOL JEM 3000F)

3 RESULTS AND DISCUSSION

The plasma density from the internal linear-type ICP wasmeasured as a function of RF power from 1000 W to4000 W for 15 mTorr Ar either with or without theapplication of the magnetic field as shown in Figure 1The magnetic field was measured using a Langmuir probelocated 4 cm below the ICP antenna The results of themeasurements are shown in Figure 2 and as can be seenin the figure the plasma density increased almost linearlywith increasing RF power both with and without the multi-polar magnetic field However for the same RF power theICP with the magnetic field had a plasma density that wasalmost 50 higher than the density without the magneticfield At 4000 W of RF power the ICP with the mag-netic field produced a plasma density of approximately28times1011 cmminus3 The presence of a magnetic field resultsin a higher plasma density because of the increased con-finement of the plasma within the chamber as well as the

J Nanosci Nanotechnol 9 7440ndash7445 2009 7441



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Effect of Multi-Polar Magnetic Field on the Properties of Nanocrystalline Silicon Thin Film Kim et al

1000 2000 3000 400005

10

15

20

25

30

Plas

ma

dens

ity (

times 1

011 c

mndash3

)

RF source power (W)

With multi-polar magnetic fieldWithout multi-polar magnetic field

Fig 2 Ar+ ion density measured by a Langmuir probe at 4 cm belowthe antenna with and without a multi-polar magnetic field present

increased path lengths of the energetic electrons The mag-netic field at each magnetrsquos surface was about 3000 Gwhile the magnetic field measured near the antenna linewas approximately 10 G The electron cyclotron frequencynear the antenna line was calculated to be about fce =28 MHz while the ion cyclotron frequency was aboutfci = 038 KHz13 Because of the gyromotion of the ener-getic electrons formed in the plasma the ions travel alonger path length before they are collected at the cham-ber wall which results in an increase in the plasma den-sity Furthermore the magnetic field formed between thechamber wall and the antenna by the multi-polar magnetscauses the mobility of electrons moving perpendicular tothe antenna line and especially those moving toward thechamber wall located close to the antenna line to be sig-nificantly decreased which in turn causes the plasma to beconfined effectively in the chamber without losing chargedparticles to the chamber wall near the antennaUsing 4000 W of RF power which was the level that

produced the highest plasma density we investigated thedegree of dissociation of the SiH4H2 gas mixture usingOES The total flow rate of SiH4H2 was maintained at200 sccm and the working pressure was maintained at20 mTorr Figure 3 shows the OES data for Hlowast

SiHlowast mea-

sured as a function of H2 dilution from 10 to 70 Theoptical emission peaks of SiHlowast and Hlowast

were measured tobe at 413 nm and 656 nm respectively As shown in thefigure as the H2 percentage in the gas mixture increasedthe ratio Hlowast

SiHlowast increased almost linearly both with and

without the magnetic field For each fixed H2 percentagethe ratio of Hlowast

SiHlowast was higher for the ICP with the mag-

netic field at 70 H2 for example the ratio was about 37for the ICP without the magnetic field and about 44 withthe magnetic field Thus the addition of the multi-polarmagnetic field enhanced the dissociation of the gas mixturewhile increasing the percentage of hydrogen radicals in theplasma It has been reported that the amount of hydrogenradicals in the SiH4-based plasma plays an important role

0 20 40 60 80

25

30

35

40

45

H S

iH r

atio

H2 percentage ()


Fig 3 OES for the ratios of HlowastSiH

lowast as a function of H2 percentage at20 mTorr of operating pressure with and without a multi-polar magneticfield present

in determining the structure of the deposited silicon thinfilm with an increase in the percentage of hydrogen rad-icals in the plasma leading to an increased crystallizationpercentage for the silicon thin film being deposited14ndash16

To investigate the effect that the amount of hydrogenradicals in the SiH4H2 plasma has on the crystal struc-ture we investigated the material properties such as darkconductivity crystallization percentage and the absorptioncoefficient of photon energy for the silicon deposited bythe ICP with and without the magnetic field Figure 4(a)shows the dark conductivity and crystalline volume frac-tion of the silicon film as a function of H2 percentage inSiH4H2 for the ICP with and without the magnetic fieldA 4000 Aring (plusmn200 Aring) thick silicon film was deposited with4000 W of RF power 200 sccm of total flow rate and20 mTorr of working pressure at a substrate temperatureof 180 C The crystalline volume fraction (Xc) was esti-mated by deconvoluting the peak obtained from Ramanspectroscopy to the amorphous peak (480 cmminus1) and thecrystalline peak (510 cmminus1 and 520 cmminus1) As shownin the figure when the multi-polar magnetic field wasturned off the deposited film showed the characteristicsof nanocrystalline silicon when the H2 dilution percentagewas higher than 50 and increasing the H2 percentageto 70 increased Xc to about 63 On the other handwhen the magnetic field was applied the deposited filmshowed the characteristics of nanocrystalline silicon onethe H2 percentage reached 30 and when the H2 percent-age was increased to 70 the crystalline volume fractionreached 68 In short the silicon deposited by the ICPwith the magnetic field present showed a higher crystal-lization volume fraction at the same H2 percentages com-pared with the silicon deposited by the ICP without themagnetic field The role of the magnetic field in produc-ing a higher crystallization volume fraction is thought tobe related to the higher Hlowast

SiHlowast ratio observed when the

magnetic field was present (Fig 3) that is related to the

7442 J Nanosci Nanotechnol 9 7440ndash7445 2009



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20 22 24 26 28 30

50 times 104

10 times 105

15 times 105

20 times 105 With multi-polar magnetic field

Without multi-polar magnetic field

Abs

orpt

ion

coef

fici

ent (

cmndash1

)

Photon energy (eV)

7050

3010

7050

3010

10 20 30 40 50 60 7010ndash10

10ndash9

10ndash8

10ndash7

10ndash6

0

20

40

60

80

100

Xc

()


Dar

k co

nduc

tivity

(Ω

ndash1 c

mndash1

)

H2 percentage ()

(a)

(b)

00

Fig 4 (a) Crystalline volume fraction (Xc) and dark conductivity asa function of H2 percentage at 20 mTorr of SiH4H2 with and withouta multi-polar magnetic field present (b) Absorption coefficient of thephoton energy with and without a multi-polar magnetic field present

larger number of hydrogen radicals in the plasma causedby the enhanced dissociation of the gas mixtureThe dark conductivity of the deposited silicon thin films

in Figure 4(a) showed a trend similar to the one observedfor the crystalline volume fraction of the deposited sili-con film As shown in the figure higher H2 percentagesled to deposited silicon films with a higher dark con-ductivity and at a given H2 percentage the silicon filmdeposited with the magnetic field present showed higherdark conductivity than the silicon film deposited with-out the magnetic field Since the electrical properties ofnanocrystalline silicon are known to be related to thedegree of crystallization17 the increased dark conductiv-ity of the deposited film is believed to be related to thedecrease of the number of crystal defects in the depositedsiliconFigure 4(b) shows the absorption coefficient measured

as a function of photon energy for the silicon thin filmsGenerally speaking the absorption coefficient increasedwith increasing photon energy up to 30 eV however sil-icon films deposited with higher H2 percentage and withmagnetic field present displayed a lower absorption coef-ficient at a given photon energy As with dark conduc-tivity the decreased absorption coefficient in silicon films

16 20 24 28 32 3610ndash10

10ndash9

10ndash8

10ndash7

10ndash6

10ndash5

10ndash4

10ndash3

10ndash2

10ndash1

100

σ [Ω

minus1 c

mndash1

]

1000T [Kndash1]

With multi-polar magnetic field

10305070

Fig 5 Temperature dependence of dark conductivity for nanocrys-talline silicon thin film as a function of H2 percentage with a multi-polarmagnetic field present

deposited with higher H2 percentage and with the magneticfield present is related to the increase in the crystalliza-tion volume fraction Because of the indirect energy bandgap of crystalline silicon increased crystallization in thedeposited film decreases the absorption coefficient18

Figure 5 shows how the temperature dependence of darkconductivity for silicon thin film deposited with a multi-polar magnetic field varies as a function of H2 percentageduring deposition The dark conductivity was measured fortemperatures between room temperature and 573 K andthe charge carrier activation energy was calculated fromthe equation

= 0 expminusEakBT

where kB is the Boltzmann constant and T is the abso-lute temperature The activation energy can be calculatedfrom the slope of the Arrhenius plot The activation energymeasured as a function of H2 percentage decreased from057 eV to 029 eV as the H2 percentage increased Defectsin nanocrystalline silicon thin film lead to an decreasein activation energy because of the increased presenceof trapping states This behavior in the silicon thin filmsexplains the increase in the crystalline volume fractionwith increasing H2 percentage

Figure 6 shows the deposition rate of silicon measuredas a function of the percentage of H2 in SiH4H2 for theICP both with and without the magnetic field The depo-sition condition was the same as for Figure 4 As can beseen from the figure an increase in the hydrogen percent-age in the gas mixture led to a decrease in the deposi-tion rate from 22 Arings at 10 H2 to 8 Arings at 70 H2

for the ICP without the magnetic field thus the increasein the crystallization volume fraction was accompanied bya decrease in the deposition rate In the case of the ICPwith the magnetic field present the deposition rate alsodecreased in this case from 26 Arings at 10 H2 to 10 Aringsecat 70 H2 which was similar to the pattern seen for the




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10 20 30 40 50 60 705

10

15

20

25

Dep

ositi

on r

ate

(As

ec)

H2 percentage ()



Fig 6 Deposition rate of nanocrystalline silicon thin films as a functionof H2 percentage with and without a multi-polar magnetic field present

ICP without the magnetic field However at a given H2

percentage the deposition rate for the ICP with the mag-netic field present was higher than with magnetic fieldnot present The higher rate of deposition with the mag-netic field present is related to the increased dissociationof SiH4 by the gyromotion of the energetic electrons inthe plasma19ndash20

(a)

(b)

470 mm

370

mm

Fig 7 Non-uniformity of nanocrystalline silicon thin films depositedon a glass substrate with an area of 470 mmtimes 370 mm measuredat 4000 W of rf power 70 of H2 in SiH4H2 and 20 mTorr ofworking pressure (a) with a multi-polar magnetic field present and (b)without a multi-polar magnetic field ( 3500sim3800 3800sim4100

4100sim4400 units Aring)

Fig 8 TEM micrographs and diffraction patterns of the silicon thinfilm

The deposition uniformity along the substrate area of370 mmtimes470 mm was measured at 70 H2 while keepingthe other deposition parameters same as those for Figure 4and the results are shown in Figure 7(a) for the ICP withthe magnetic field present and (b) for the ICP without themagnetic field The deposition uniformity of the ICP with-out the magnetic field was approximately 11 while thatwith the magnetic field present was about 9 implyingthat a more uniform deposition can be obtained for the ICPwith the magnetic field present The improvement of thedeposition uniformity appears to be related to the plasmaconfinement effect obtained with the multi-polar field con-figuration In Figure 8 grain sizes ranging from 5 to 15 nmcan identified and the crystallization percent was around70 The multi-polar magnet configuration used in thisstudy decreases the electron mobility in the vertical direc-tion from the antenna line Thus the increase of depositionuniformity in the presence of the magnetic field is believedto be related to a decrease in charged particle loss near thechamber wall caused by a decrease in electron mobilitytowards that wall along with an increase in the plasmadensity13

4 CONCLUSIONS

We investigated the effects of applying a multi-polar mag-netic field to a particular type of internal linear ICP (theldquodouble comb-type ICPrdquo) on the devicersquos plasma charac-teristics and also on the characteristics of the nanocrys-talline silicon thin films deposited using SiH4H2 Theapplications of such thin films include FPDs and siliconphotovoltaic devices Using the multi-polar magnetic fieldwith the internal-type ICP not only increased the plasmadensity but also increased the dissociation rate Further-more the use of the magnetic field with the ICP improvedthe quality of the deposited silicon thin film by increasingthe crystallization volume fraction and the dark conduc-tivity and decreasing the absorption coefficient of photon




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energy The improvement of the plasma characteristics andthe material characteristics in the presence of the magneticfield is believed to be due to plasma confinement in thechamber volume which decreases the mobility of elec-trons moving in a vertical direction from the antenna lineand increases the path lengths of energetic electrons bycausing a gyromotion The plasma confinement created bythe magnetic field also leads to a higher deposition unifor-mity Using the double comb-type ICP with the magneticfield present we were able to deposit nanocrystalline sili-con thin films having a crystallization volume fraction of68 at a deposition rate of 10 Arings when using 4000 W ofRF power at 20 mTorr of SiH4H2 (70 H2) and a sub-strate temperature 180 C Most of the grain sizes in thefilm ranged from 5 to 15 nm

Acknowledgments Financial support for this researchwas provided by the Ministry of Knowledge Economy(MKE) and the Korea Industrial Technology Foundation(KOTEF) through the Human Resource Training Projectfor Strategic Technology

References and Notes

1 A Shah M Vanecek J Meier F Meillaud J GuilletD Fischer C Roz X Niquille S Fay E Vallat-SauvainV Terrazzoni-Daudrix and J Ailat J Non-Cryst Solids 338 639(2004)

2 J Kocka A Fejfar T Mates P Fojtiacutek K Dohnalovaacute K LuterovaacuteJ Stuchliacutek H Stuchliacutekovaacute I Pelant B Rezek A Stemmer andM Ito Phys Status Solid C 1 1097 (2004)

3 C Jeong S Boo T W Kim B H Choi H S Kim D R ChangJ H Lee and K Kamisako J Nanosci Nanotechnol 8 5521(2008)

4 S Kumar J Gope A Kumar A Parashar C M S Rauthan andP N Dixit J Nanosci Nanotechnol 8 4211 (2008)

5 M A Lieberman and A J Lichtenberg Principles of Plasma Dis-charges and Materials Processing Wiley New York (1994)

6 Y Ra S G Bradely and C H Chen J Vac Sci Technol A 121328 (1994)

7 W E Spear G Willeke P G LeComber and A G FitzgeraldJ Physique 42 C4 257 (1981)

8 J H Lim K N Kim J K Park J T Lim and G Y Yeom ApplPhys Lett 92 051504 (2008)

9 M Sekine M Narita K Horioka Y Yoshidam and H O KanoJpn J Appl Phys 34 6274 (1995)

10 A Matsutani F Koyama K Ohashi T Yokoyama andH Yamakage Jpn J Appl Phys 43 L960 (2004)

11 R W Boswell and F F Chen IEEE Trans Plasma Sci 25 1229(1997)

12 K N Kim Y J Lee S J Kyong and G Y Yeom Surf amp CoatTechnol 177 752 (2004)

13 K N Kim M S Kim and G Y Yeom Appl Phys Lett 88 161503(2006)

14 K N Kim J H Lim and G Y Yeom Thin Solid Films 515 5193(2007)

15 F Tochikubo A Suzuki S Kauta Y Terazono and T MakabeJ Appl Phys 68 5532 (1990)

16 P Torres U Kroll H Keppner J Meier E Sauvain and A ShahProc of the 5th Thermal Plasma Process St Petersburg

17 S J Jones Y Chen D L Williamson U Kroll and P Roca iCabarrocas J Non-Cryst Solids 131 164 (1993)

18 M Otobe and S Oda J Non-Cryst Solids 164 993 (1993)19 T Tabuchi M Takashiri and K Ishida Surf amp Coat Technol 202

114 (2007)20 Z Sun X Shi and E Liu Thin Solid Films 355 146 (1999)

Received 9 October 2008 Accepted 17 March 2009




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Magnetic fields have been used with various plasmasources to improve the properties of the plasma9ndash11 Eventhough an internal linear-type ICP source can generatehigh-density plasmas by itself the addition of a multi-polartype magnetic field to the internal-type ICP source can fur-ther increase the plasma density and the dissociation rateby increasing the path length of energetic electrons andby confining the plasmas in the chamber In fact when aninternal linear-type ICP was employed for silicon etchingusing reactive gases the addition of a magnetic field to theinternal linear-type ICP not only increased the etch ratebut also improved the etch uniformity on the substrate12

In this study we used a double comb-type internal ICPsource with a multi-polar magnetic field for the deposi-tion of nanocrystalline silicon and investigated the effectsof the magnetic field on the characteristics of SiH4-basedplasma Besides investigating such deposition characteris-tics as the deposition rate and uniformity we studied theeffects of the multi-polar magnetic field on the propertiesof nanocrystalline silicon thin films It is believed that amagnetic-field-enhanced ICP source can increase plasmadensity and plasma uniformity which implies that the useof our plasma source for the deposition of nanocrystallinesilicon should increase the uniformity of the depositednanocrystalline silicon as well as the crystallization per-centage of the deposited silicon at low temperatures

2 EXPERIMENTAL DETAILS

Figure 1 shows a schematic diagram of the experimentalapparatus used in the experiment To deposit the nanocrys-talline silicon thin films we designed a rectangular plasmaprocessing chamber with inner dimensions of 1020 mmtimes830 mm that held substrate with dimensions 470 mmtimes370 mm Samples were loaded onto the substrate holder invacuum through a loadlock chamber The antenna for the

Fig 1 The double comb-type internal linear ICP and the multi-polarmagnet used in the experiment

internal linear-type ICP was made of 10 mm-diameter cop-per tubing inside quartz tubing that was 15 mm in diameterand 2 mm in thickness A series of five linear antennaswas embedded in the process chamber with the antennasconnected to an RF power supply (1356 MHz) througha matching network in an alternating fashion in order toform a ldquodouble comb-type antennardquo A multi-polar mag-netic field was applied by inserting permanent magnetseach with 3000 G on the magnet surface in the quartztubing located above and parallel to the linear internalantennas as shown in Figure 1 The plasma characteristicswith and without the magnetic field were measured usinga Langmuir probe (Hiden Analytical UK ESP) for ArCorning 1737 glass was used for the substrate and to

grow nanocrystalline silicon thin films SiH4 diluted byH2 was fed into the chamber with the operating pres-sure maintained at 20 mTorr RF power to the ICP sourcewas fixed at 4000 W while the substrate temperature wasmaintained at 180 C While deposition process was pro-ceeding an OES (PCM 420 SC-Technology) was used tomeasure the dissociated species in the SiH4H2 plasmaTo evaluate the crystalline volume fraction of the films atthe deposition thickness of 4000 Aring (plusmn200 Aring) we usedRaman spectroscopy (Kaiser Optical System Inc) Theabsorption coefficient and the dark conductivity of the4000 Aring thick films deposited were investigated as a func-tion of the H2 percentage in SiH4H2 by an ultraviolet-visible (UV-Vis) spectrometer (Scinco S-1000) and bya semiconductor characterization system (Keithley 4200)respectively after the formation of Al coplanar electrodeson the deposited nanocrystalline silicon The activationenergy (Ea) of charge carriers was calculated from thetemperature-dependent dark conductivity measurementsThe nanostructure of the deposited hydrogenated siliconthin film was observed using high resolution transmissionelectron microscopy (HRTEM JEOL JEM 3000F)

3 RESULTS AND DISCUSSION

The plasma density from the internal linear-type ICP wasmeasured as a function of RF power from 1000 W to4000 W for 15 mTorr Ar either with or without theapplication of the magnetic field as shown in Figure 1The magnetic field was measured using a Langmuir probelocated 4 cm below the ICP antenna The results of themeasurements are shown in Figure 2 and as can be seenin the figure the plasma density increased almost linearlywith increasing RF power both with and without the multi-polar magnetic field However for the same RF power theICP with the magnetic field had a plasma density that wasalmost 50 higher than the density without the magneticfield At 4000 W of RF power the ICP with the mag-netic field produced a plasma density of approximately28times1011 cmminus3 The presence of a magnetic field resultsin a higher plasma density because of the increased con-finement of the plasma within the chamber as well as the




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1000 2000 3000 400005

10

15

20

25

30

Plas

ma

dens

ity (

times 1

011 c

mndash3

)

RF source power (W)





SiHlowast mea-







0 20 40 60 80

25

30

35

40

45

H S

iH r

atio

H2 percentage ()











ARTIC

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20 22 24 26 28 30

50 times 104

10 times 105

15 times 105



Abs

orpt

ion

coef

fici

ent (

cmndash1

)

Photon energy (eV)

7050

3010

7050

3010

10 20 30 40 50 60 7010ndash10

10ndash9

10ndash8

10ndash7

10ndash6

0

20

40

60

80

100

Xc

()


Dar

k co

nduc

tivity

(Ω

ndash1 c

mndash1

)

H2 percentage ()

(a)

(b)

00





16 20 24 28 32 3610ndash10

10ndash9

10ndash8

10ndash7

10ndash6

10ndash5

10ndash4

10ndash3

10ndash2

10ndash1

100

σ [Ω

minus1 c

mndash1

]

1000T [Kndash1]


10305070




= 0 expminusEakBT







RESEARCH

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10 20 30 40 50 60 705

10

15

20

25

Dep

ositi

on r

ate

(As

ec)

H2 percentage ()






(a)

(b)

470 mm

370

mm





4 CONCLUSIONS





ARTIC

LE




























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1000 2000 3000 400005

10

15

20

25

30

Plas

ma

dens

ity (

times 1

011 c

mndash3

)

RF source power (W)





SiHlowast mea-







0 20 40 60 80

25

30

35

40

45

H S

iH r

atio

H2 percentage ()











ARTIC

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20 22 24 26 28 30

50 times 104

10 times 105

15 times 105



Abs

orpt

ion

coef

fici

ent (

cmndash1

)

Photon energy (eV)

7050

3010

7050

3010

10 20 30 40 50 60 7010ndash10

10ndash9

10ndash8

10ndash7

10ndash6

0

20

40

60

80

100

Xc

()


Dar

k co

nduc

tivity

(Ω

ndash1 c

mndash1

)

H2 percentage ()

(a)

(b)

00





16 20 24 28 32 3610ndash10

10ndash9

10ndash8

10ndash7

10ndash6

10ndash5

10ndash4

10ndash3

10ndash2

10ndash1

100

σ [Ω

minus1 c

mndash1

]

1000T [Kndash1]


10305070




= 0 expminusEakBT







RESEARCH

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10 20 30 40 50 60 705

10

15

20

25

Dep

ositi

on r

ate

(As

ec)

H2 percentage ()






(a)

(b)

470 mm

370

mm





4 CONCLUSIONS





ARTIC

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ARTIC

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20 22 24 26 28 30

50 times 104

10 times 105

15 times 105



Abs

orpt

ion

coef

fici

ent (

cmndash1

)

Photon energy (eV)

7050

3010

7050

3010

10 20 30 40 50 60 7010ndash10

10ndash9

10ndash8

10ndash7

10ndash6

0

20

40

60

80

100

Xc

()


Dar

k co

nduc

tivity

(Ω

ndash1 c

mndash1

)

H2 percentage ()

(a)

(b)

00





16 20 24 28 32 3610ndash10

10ndash9

10ndash8

10ndash7

10ndash6

10ndash5

10ndash4

10ndash3

10ndash2

10ndash1

100

σ [Ω

minus1 c

mndash1

]

1000T [Kndash1]


10305070




= 0 expminusEakBT







RESEARCH

ARTIC

LE


10 20 30 40 50 60 705

10

15

20

25

Dep

ositi

on r

ate

(As

ec)

H2 percentage ()






(a)

(b)

470 mm

370

mm





4 CONCLUSIONS





ARTIC

LE




























RESEARCH

ARTIC

LE


10 20 30 40 50 60 705

10

15

20

25

Dep

ositi

on r

ate

(As

ec)

H2 percentage ()






(a)

(b)

470 mm

370

mm





4 CONCLUSIONS





ARTIC

LE




























ARTIC

LE


























effect of multi-polar magnetic field on the properties of … · 2016. 8. 17. · kim et al. effect...

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