Compan - pdfs.semanticscholar.org y Conden tial T ec hnical Note Title P o wder formation in silane plasmas Authors WHM Lo dders P art of pro ject Philips Solid State Course Customer

Nat�Lab� Technical Note ��

Date of issue� ��

Powder formation in silane

plasma�s�

W�H�M� Lodders

Company Con�dential ��c�Philips Electronics ��

�� Company Con�dential ��

Authors� address data� W�H�M� Lodders WB�� lodders�natlab�research�philips�com

c�Philips Electronics N�V� ��

All rights are reserved� Reproduction in whole or in part isprohibited without the written consent of the copyright owner�

ii c�Philips Electronics NV ��

Company Con�dential ��

Technical Note� ��

Title� Powder formation in silane plasma�s�

Author�s�� W�H�M� Lodders

Part of project� Philips Solid State Course

Customer� Company con�dential

Keywords� Plasma Enhanced Chemical Vapour Deposition silane plasmaamorphous silicon powder formation �� transition

Abstract� This literature survey is performed as a part of the Philips Solidstate course� It deals with powder formation in silane containing plasma�s� In recent studies substantial progress has beenmade� A detailed powder formation mechanism has evolvedwhich also accounts for the occurence of a so called �� transition� Based on the understanding of the particle formationmechanism and the dynamics of particles in a gas�ow� e�ectivemeans to minimise powder formation e�ects have been developed�

Conclusions� The formation of powder in a silane plasma takes place in threesteps� In the �rst step particles of � nm diameter are formed byclustergrowth via ionmolecular interactions like SiH�

� � SiH�

� Si�H�� H�� Si�H�

� � SiH� � Si�H�� H� etc� In the next

step the particles of � nm coagulate to a diameter of � nm andin the last step the particles grow to �� nm� Powder formation induces a plasma transition from collisional �wave riding�at the sheath boudaries ��regime� to �Joule heating� in theplasma bulk �referred to here as the �regime�� This transitionis associated with powder accumulation in the plasma enhancing by a factor of � �� the electron atachment rate� Powderformation is e�ectively suppressed in modulated plasma�s athigher gas temperature�

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Contents

� Introduction �

� Particle formation mechanism �

� Particle characteristics �� The particle precursors� initial cluster growth � � � � � � � � � � � � � � �� Particle composition and size � � � � � � � � � � � � � � � � � � � � � � � �� Where in the plasma does the particle formation take place� � � � � � � �

� Minimisation of particle density �� Removal of particles from the plasma by using grooves in the electrode �� The eect of gas temperature � � � � � � � � � � � � � � � � � � � � � � � �� The eect of reactor design � � � � � � � � � � � � � � � � � � � � � � � � � �� The eect of plasma�modulation � � � � � � � � � � � � � � � � � � � � � � �

References �

Distribution

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� Introduction

Plasma deposition of amorphous silicon ��Si�H� is particularly suited to large areaelectronics for optical imaging devices� matrix�addressed arrays� and solar cells� toname just a few commercial applications� However� it has become clear that particu�late contamination presents a major problem by limiting manufactoring productivityand device reliability� Modern trends� toward larger circuit dimension together withsmaller feature size and higher component densities� will aggravate the risk of particlerelated yield losses� for example� a single defect on a matrix array could mean theloss of the entire display whereas a defect on a silicon wafer may damage only oneof many separate devices� Since particulates in processing plasmas are serious obsta�cles to microelectronics fabrication� great attention has been placed on clarifying theirformation kinetics and suppressing their growth� In this note the recent literature onparticle formation in silane plasma�s is reviewed� This work is performed as a part ofthe Philips Solid state course�

� Particle formation mechanism

Inspection of a Plasma Enhanced Chemical Vapour Deposition PECVD� reactor showsthat after a few depositions of amorphous silicon dust formation has taken place�

If we look closely� the cold reactorparts in the machine are covered with dust�The dust formation in the plasma can be devided into three steps� Firstly� growth ofparticles up to � nm in size takes place� then in the second step agglomeration takesplace and in the thirth step particle growth saturates�Perrin et al �� and Fridman et al �� have given a detailed discussion of the mechanisminvolved� Fig� �� shows typical silane plasma characteristics� In the �rst microsecondthe plasma ignites and reaches a steady state� The Rf voltage Vrf � and the Rf currentJrf reach steady values almost immediately� The plasma now operates in the so called��regime�In this regime the Vrf and the Jrf stay the same and the reactions that take place areions with molecules� In this regime the particle diameter can grow up to a few nm�There is no dust measured in the plasma because the dust particles up to a few nmare to small for the most sensitive detectionmethods�Fridman assumes that the reaction mechanism starts with SiH�

� negative�ion forma�tion by dissociative attachment� Then the negatively charged clustergrowth takes placeby ion�molecular reactions like� SiH�

� � SiH� � Si�H�� H�� Si�H�

� � SiH� � Si�H��

� H�� see �g� �� As the negative cluster size increases the probability of the reactionwith the vibrationaly excited molecules decreases because of the strong eect of vibra�tional temperature relaxation on the cluster surface� When the particles size reaches acritical value the chain reaction of cluster growth becomes much slower and is �nallystopped by the ion�ion recombination process� The typical time of � nm particle for�mation by this mechanism is shown to about � ms at room temperature� The nextthing we want to know is� why do these particles stay in the plasma� The trappingof negatively charged particles in any discharge is connected with the repelling forces

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exerted on such particles in the electrostatic sheaths when they reach the edge of theplasma� But for the supersmall particles under consideration here� � � nm� the elec�tron attachment time is as long as �� ms and almost two orders of magnitude longerthen the fast ion�ion recombination time� so most of the particles are neutral in thisperiod� However the trapping of neutral particles becomes clear taking into account�that for � nm particles the electron attachment time is not longer than the residencetime� and each neutral particle was charged at least once during the residence time�It�s very important to note here� that the rate coe�cient of twobody electron non�dissociative attachment increases strongly with the particle size� For this reason� theattachment time of particles much less than � nm is much longer than the recidencetime� and there is no posibilitie to get charged even once� Hence small particles arenot trapped in plasma� Only big particles� � � nm� survive� this is the size selectivetrapping eect�After this step � appears� In this step the particles of a few nm coagulate to par�ticles with a radius of �� nm� The fast coagulation phenomenon occurs whenthe growing concentration of survived monodispersed � nm particles reaches a criticalvalue about �� cm�� For such concentrations the attachment of small negativeions like SiH�

�� to � nm particles becomes faster than the chain reaction to grow newparticles� New chains of dust formation are almost suppressed and the total particlemass and respectively the production of particle concentration and cube of their ra�dius� remains almost constant� In this fast coagulation process the mass increase by asurface deposition process is negligible� The particle density after coagulation is �� cm��The temperature doesn�t aect the critical value of �� cm�� However� thetypical induction time before coagulation is shown to be about �� ms for room tem�perature� and much longer for �� K� This can be explained� taking into account theselective trapping eect discussed above� The trapped production rate for �� K ismuch slower than for room temperature� but the critical particle concentration valueremains the same�A possible mechanism that causes coagulation is secondairy emission� which producespositive ion attachment� which results in negative ion and neutral chain reaction whichresults in neutrals � These charged particles and neutral ones start to react with ea�chother to form a larger particle coagulate �g� �� After the coagulation� the enhanced attachment to multiply charged particles makesthe plasma more resistive� A strong decrease of the free electron concentration and asmall increase of gastemperature takes place� Consequently the Vrf decreases and Jrfincreases see �g� �� The point where the particles start to coagulate� and the plasmabecomes resistive is called the �� transition�Finally saturation takes place� In the third step large particles continue to grow byradical condensation� The Vrf and the Jrf stay stable� see �g� �� This regime is calledthe ��regime� If very large particles are formed the plasma starts to cough because aninstable plasma is created� The particles that have reached a critical value weight� are�ushed out of the plasma� The corresponding electron density �uctuations are shownin �g� �� If we look at the magnitude of the self�bias voltage� the DC�bias� during the whole



process described above we see that its value drops upon coagulation� In the ��regime�the DC�bias slightly increases at �rst and than stays at a constant low value �g� � ��

� Particle characteristics

�� The particle precursors� initial cluster growth

Howling �� used a mass spectrometer to study the occurrence of negative and posi�tive molecular ion groups in a power�modelated plasma� The plasma contains silanecontaining particles� Fig� �� shows the negative and positive ion�mass spectra� ob�tained with low mass resolution� Each peak represents the combined intensities ofthose polymeric silicon ion groups irrespective of their hydrogen content� Negativepolysiliconhydride ionic clusters where observed right up to �� amu mass limit of themass spectrometer� corresponding to hexadecasilicon hydride anions �Si�Hx�

�� Clearly�heavy negative ions do exist in this silane plasma and could conceivably be the poly�merisation pathway to larger clusters� and ultimately to powder particles� These nega�tive molecular ions are singly charged by incorporation of an electron into a molecularorbital� The positive ion masses in �g� �� are limited to only �� amu� correspondingto pentasiliconium ions �Si�H�� possibly because the activation energy barriers inhibitfurther cluster growth� The positive ion size might also be limited because of ion�ionrecombination losses� or because they are e�ciently evacuated from the plasma� Theweak intermediate peaks in the positive ion spectrum are due to ions of type �SiHO��where the oxygen comes from residual water outgassing from the reactor walls� Therelative ion currents� measured for negative and positive ions and for ions formed fromneutral radicals in the mass spectrometer ionizer by �� eV electrons are shown in�g �� The density of negative relative to positive ions is di�cult to quantify becauseof the dierent plasma conditions afterglow and power�on period respectively� dur�ing extraction of each type from the plasma �� Nevertheless� it is unlikely that anycharge�dependent correction factor would increase faster than exponentially with mass�see �g� �� Therefore we can conclude from �g� �� and �� that the negative ionsattain much higher masses than the positive ions�

�� Particle composition and size

Dutta �� analysed powder in the reactorchamber after the deposition of some layers�He found dierently coloured powders in the chamber� namely a reddish brown colouredpowder on the Rf�electrode and yellow colourred powder on the walls� He looks withIR�spectroscopy if there are dierences between dierently coloured dust particles�Fig� �a� represents the spectra of ��Si�H powders prepared by a plasma CVD processat �� C under the conditions for the deposition of device quality thin �lms� while�g� �b� and �c� represent the IR spectra of the reddish�brown powder and the yellowpowder� respectively� Strong bands at �� and �� cm�� can be assigned tothe silicon�hydrogen �SiH and SiH�� wagging and bending mode vibrations� while theband between �� cm�� arises from the silicon�hydrogen �Si�H� SiH�� and



SiH��n� stretching vibration� The Si�H� SiH�� and SiH��n stretching modes are usualyobserved in highly porous ��Si�H �lms with large void fractions� The Si�H stretchingbond is predominant in the amorphous silicon powders� For the red powders� theSiH� stretching at �� cm�� and for the yellow powders� the SiH��n stretching at�� cm�� are relatively more dominant modes as compared to the amorphous siliconpowders� The compositional dierences between the powders are small� Exposure toatmosphere oxidizes the powders as can be noticed from the prominent silicon�oxygenabsorption band centred around �� cm�� oxygen�hydrogen bending at �� cm��

and the O�Si�O wagging mode vibrations at �� cm�� In addition there is also thepresence of the Si�O� mode at �� cm�� Due to the larger surface area of the smallerparticles yellow powder� we notice a much pronounced oxidation of these powders�We ourselves also investigated PECVD powder with IR�spectrometry� A typical IR�spectrum measured just after deposition is given in �g� �� This spectrum does notindicate the presence of oxygen in the powder� Fig� �� shows a spectrum obtainedafter air exposure of the powder� This clearly indicates oxidation after exposure�Shiratani et al �� studied the time evolution of size and density of the PECVD�powderparticles using polarization�sensitive laser�light scattering PSLLS�� Fig� �� shows thatlittle particles are always present � � nm�� After a while coagulation occurs� in�g� �� after � sec� The particle diameter is then � �� nm� So we have at a giventime particles of � � nm and particles of �� nm� SEM and TEM pictures are givenin �g �� The displayed morphology indicates that the powder particles of�� nm consist of little particles of � � nm�

�� Where in the plasma does the particle formation takeplace�

Watanabe et al �� studied the distribution of dust particles in the dicharge space ina modulated plasma� Fig� �� and �� show the spatial distribution of the powderparticles as a function of the time elapsed after the plasma initiation� Fig� �� showsa typical spatial pro�le of particulate size and density obtained� Particulates begin tobe observed around the sheat edge near the Rf electrode� particulate size and densityamount to �� nm and �� cm�� during a short time of � � � s after the Rfpower being turned on� Smaller particles in an early nucleation phase can be observedusing a Langmuir probe technique� The ratio M

��M� between negatively charged

small particles M�� and positive ions M�� can be determined� Fig� �� shows this

ratio as a function of plasma on�time� It can be seen that the ratio M��M� increases

with Ton and becomes large in the sheath edge region � � �� mm away from theRf electrode� This trend of localization becomes weak with increasing �ow rate and�at a high �ow rate over about �� sccm � the region of large M

��M� tends to shift

downstream not shown�� Thus� particulate amounts are predominantly rich aroundthe sheath edge near the electrode� especially the Rf electrode� and can be somewhatmodi�ed by the gas�ow�

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� Minimisation of particle density

�� Removal of particles from the plasma by using grooves inthe electrode

Selwyn �� investigated the places where powder is trapped in the discharge space as afunction of electrode shape� Probe measurements have shown that particle traps havea higher plasma potential then the surrounding plasma regions� possibly explaining thedrift of particles to these localized regions� Particle traps are local plasma disturbances�Accordingly� the intensity of optical emission spectroscopy EOS� will vary spatiallydue to the presence of traps� This approach may be used to map quantitatively thepresence and intensity of particle traps and to correlate these formations with featureson the tool electrode� For instance the �� nm Ar neutral emission line is monitored�The time�dependent OES signal is converted to a map of intensity of the �� nmneutral Ar emissionline versus horizontal and height coordinates above the electrode�This� we call an isophotal map because the counters denote lines of equal emissionintensity in this phase space� Fig� �� and �� show such isophotal maps for a �atand a grooved electrode respectively� Particles are subtracted to well de�nd localizedregions in the grooves and tend to collect preferentially in or above grooves� therebyreducing the density of the particles elsewhere in the discharge space� By connectingthe grooves and channeling them to the pump port� particles may be purged from theplasma�

�� The e�ect of gas temperature

The eect of the gas temperature on particle formation is demonstrated in �g� ��showing the Laser Induced Particle Explosive Evaporation LIPEE� emission intensityIb as a function of Ton� on a logarithmic time scale� for �ve dierent gas temperatures�varying from ambient temperature to �� C� The silane and argon �ows are� respec�tively� �� and �� sccm� We note that the appearance of initial emission intensity andalso the start of the coagulation steep increase� are delayed at higher gastemperatures�More exactly� the initial emission intensity appears quasi�instantaneously after somemilliseconds� at ambient temperature� while the appearance starts �� ms later at ��C� sec later at �� C and approximately at ��s Rf discharge duration for �� C�We also see from �g� �� that the delay between the appearance of the �rst emissionintensity and the start of the coagulation is roughly constant� of the order of somehunderds of miliseconds� Why does the delay for coagulation increase so strongly� if weincrease the gas temperature� Boufendi �� discussed� that the growth of supersmallparticle precursors proceeds via a chain of negative�ion molecular reactions� stimulatedby vibrational excitation� A small increase of the gas temperature accelerates vibra�tional relaxation� diminishes the level of vibrational excitation� thereby deminishes thechain reaction rate� and so it makes the process of particle growth much longer�



�� The e�ect of reactor design

Seebock �� investigated the dependence on temperature and gas�ow conditions of thedynamics of submicrometer particles in discharges in silane� Fig� �� shows the reactordesign� Powder formation is detected via laser light scattering� Fig� �� shows thebands of particles that are formed when both electrodes are kept at �� C and gas inletoccurs through the ring shower� Fig� �� shows the remaining particle clouds whenthe gas is fed through the upper electrode and this electrode is heated� In this caseparticles are removed from the plasma by drag forces� Fig� �� shows the reactor spacewith gas inlet through the upper electrode and heated lower electrode� In this case theparticle density is very low� The combined action of upward�directed thermophoresisand outward�directed drag force leads to the transport of the particles away from thesubstrate and out of the interelectrode space� Notice� however� that the increase oftemperature not only induces thermal forces but also reduces particle creation� seesection �� Clearly� electrode heating together with a proper gas �ow can avoid thetrapping of particles in the interelectrode space�

�� The e�ect of plasmamodulation

So far we dicussed a continuous plasma� It is shown in the literature that a modulationof the plasma can also have a signi�cant eect on the powder formation�In �g� �� the negative ion intensity is plotted versus power modulation frequency� Inthis �gure it is shown that the negative ion intensity is signi�cant only for modulationfrequencies from about �� to � kHz� The positive ion signal� the global SiH� emission�and the volume�integrated scattering white light from the powder in the plasma arealso shown in �g� �� for comparison� Signi�cantly� the positive ion signal and the SiHemission do not vary strongly with the modulation frequency� whereas the negativeion intensities show a clear anticorrelation with the powder signal as the modulationfrequency approaches �� kHz� In a continuous power plasma with otherwise identicalconditions� copious powder production was observed several seconds after the plasmaignition� the scattered white light signal was then two orders of magnitude larger thanthe maximum of �g� �� Howling �� interpreted these �ndings as follows� �� At low modulation frequency below �� kHz� molecular clusters form within aplasma half�cycle and have su�ciently small inertia to be ejected during the afterglowperiod� They do not have su�cient time to grow large enough to be detected by visiblelight scattering� �� At high modelation frequency above � kHz�� the inertia of the cluster precursorsreduces the probability of ejection between cycles� and cluster growth continuous insuccessive plasma periods thereby further increasing their inertia and their retentionpropability� until the powder becomes visible as shown in �g� �� For an intermediate range of modulation frequency� only the cluster precursorsthemselves have su�ciently small mass to be ejected between cycles� and no clusterformation occurs �Hollenstein �� modelled the formation of powder precusors anions in the plasma asa function of modulation frequency� Fig� �� shows the time averaged anion density



versus modulation frequency� Here the data obtained for ions containing up to � siliconatoms were used to derive equations for extrapolation to higher�mass negative ions� Ex�trapolation to higher�mass negative ions in �g� �� indicates that the macro�molecularanion densities would fall to zero for a wide range of modulation frequencies below �kHz� This is because the plasma periods are then too short for the polymerization chainto propagate from monosilicon hydride anions to highly polymerized species before al�most all of the low�mass species are lost in the subsequent �o� period� Equilibriumbetween the diminished supply from preceding negative ions and the polymerizationof the polysilicon hydride anion itself results in a strongly diminished density of thehighly polymerized anions� Above � kHz� the sheaths do not fully collapse and highmass negative ions reach signi�cant densities� At very low modulation frequencies�the polymerisation in a single plasma period propagates su�ciently far to clusterscontaining perhaps �� or � silicon atoms � to initialise particle growth�Thus� plasma modulation in the frequency range �� kHz can eectively suppresspowder formation�



References

�� J� Perrin� C� Bohm� R� Etemadi� and A� Lloret� Plasma Sources Sci� Technol��

�� A� A� Fridman� L� Boufendi� T� Hbid� B�V� Potapkin� and A� Bouchoule� J�Appl� Phys� ��

�� M� Shiratani� H� Kawasaki� T� Fukuzawa�T� Yoshioka� Y� Ueda� S� Singh� andY� Watanabe� J� Appl� Phys� ��

�� W� W� Stoels� E� Stoels� G� M� W� Kroesen� and F� J� de Hoog� J� Appl�Phys� ��

�� Y� Watanabe� M� Shiratani�T� Fukuzawa� and H� Kawasaki� Plasma SourcesSci� Technol� ��

�� A� A� Howling� J� L� Sansonnens J� L� Dorier� and Ch� Hollestein J� Appl�Phys� ��

�� L� J� Overzet J� H� Beberman� and J� T� Verdeyen� J� Appl� Phys� ��

�� J� Dutta� W� Basca� Ch� Hollenstein� J� Appl� Phys� ��

�� M� Shiratani� H� Kawasaki� T� Fukuzawa� H� Tsuruoka� T� Yoshioka� and Y�Watanabe� Appl� Phys� Lett� ��

�� L� Boufendi� and A� Bouchoule� Plasma Sources Sci� Technol� ��

�� Y� Watanabe� and M� Shiratani� Plasma Sources Sci� Technol� ��

�� G� S� Selwyn� Plasma Sources Sci� Technol� ��

�� L�Boufendi� J� Hermann� A� Bouchoule� B� Debreuil� E� Stoels� W� W� Stof�fels� and M� L� de Giorgi� J� Appl� Phys� ��

�� R� J� Seebock� W� Bohme� W� E� Kohler� M� Romheld� and S� Veprek� PlasmaSources Sci� Technol� ��

�� A� A� Howling� J� L� Dorier and Ch� Hollestein� Appl� Phys� Lett� ��

�� Ch� Hollenstein� J� L� Dorier� J� Dutta� L� Sansonnens� and A� A� Howling�Plasma Sources Sci� Technol� ��



Figure �� Development of the transition towards powder formation after plasma igni�tion in a SiH� �� MHz radiofrequency discharge at �� mbar and �� C charac�terized by the evolution of SiH� at �� nm and of the electrical properties ��

Figure �� Physical scheme of �rst generation of supersmall particle growth ��



Figure �� Coagulation model in rapid growth phase� a� Negatively charged� positivelycharged and neutral particles of nearly the same size coexist at start of rapid growth�Particulate density nd is much higher than electron density ne� b� Positively chargedsmall particulates are coagulated selectively with negatively charged larger particulates� c� Coagulation rate decreases considerably in growth saturation phase� because mostparticles are charged negatively ��

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Figure �� The time dependent He�Ne scattering signal forward scattering at � fromparticles that �ushed out of the discharge through the vertical slits in the cavity� dashedcurve� and the electron density solid curve�� The gas mixture contains � SiH� inargon� the pressure is �� mTorr� the gas�ow is � sccm and the Rf power is ��W ��

Figure � Time evolution of laser light scattering LLS� intensity intregrated overdischarge space Vdc and powerfactor cos� as a parameter of Rf power� D��Ton��s� He�SiH� �� sccm� ��Pa ��



Figure �� Mass spectra of negative and positive molecular ion groups for a � kHz mod�ulation frequency� time averaged over �� modulation cycles� This raw data� acquiredwith low mass resolution� is uncorrected for any mass dependent fall�o in sensitivity�The vertical broken lines at intervals of �� amu mark the masses of bare silicon clusters��

Figure �� Relative ion currents measured for negative and positive ions and for ionsformed from neutral radicals in the mass spectrometer ionizer by �� eV electrons�Modulationfrequency � kHz� The straight lines are exponential �ts to the data whichare normalized to unity for the mono�silicon groups ��



Figure �� Infrared spectra of a� typical hydrogenated amorphous silicon powder b�reddish brown powder and c� yellow powder ��

Figure �� Typical infrared spectrum of powder made in the Balzers VIS �� PECVDreactor Nat� Lab��



Figure �� Typical infrared spectrum of powder particles fabricated in VIS �� reactorafter exposure to oxigen�

Figure �� Time evolution of size a� and density b� of particulates at mm belowupper powered electrode measured using PSLLS solid lines�� Circles and trianglesshow CMD�s and corresponding densities of particulates deduced from SEM observationin small�size and large�size groups� respectively ��



Figure �� SEM photograph of a particle� He�SiH� �� sccm� ��Pa� ��W� Ton��s ��

Figure �� Transmission electron micrograph of a particle formed after a plasma of ��s duration� Its diameter is about �� nm ��



Figure �� Spatial distribution of particle size and density between electrodes on dis�charge column axis at t�� and � s after discharge initiation� Ton�� s� �� W� �SiH��He� �� scccm� �� Pa� ��

Figure �� Spatial distribution of M��M� for Ton�� ms a�� ms b�� ms c��

�� ms d� and �� ms e�� W� �� SiH��He� �� sccm� �� Pa� ��



Figure �� Optical emission spectroscopy isophotal map of Ar neutral emission signal �� nm line� over a �at� uniform electrode cover ��

Figure �� Optical emission spectroscopy isophotal map of Ar neutral emission signal �� nm line� over a grooved electrode type �� The dimensions of the groove are �mm deep x �� mm wide� The groove extends the entire length of the �� mm squareelectrode ��



Figure �� LIPEE emission intensity as a function of Rf plasma discharge duration fordierent gas temperatures ��

Figure �� Schematic view of the parallel�plate plasma reactor used for the investiga�tions� The gas inlet was either through the ring shower surrounding the lower electrodeor through �ve holes in the centre of the upper electrode� Both electrodes were elec�trically heatable and temperature controlled ��



Figure �� Two bands of trapped particles between the electrode of the reactor� Bothelectrodes are kept at �� C� The forward power was �� W ��

Figure �� Particle traps above the substrate with gas inlet through ring shower�forward power �� Watt� Tel�� C Tue�� C ��



Figure �� View of the reactor space with gas inlet through the upper electrode andheated lower electrode Tle�� C� Tue�� C�� The particle contamination is belowthe detection limit ��



Figure �� Dependance of the negative ion intensities and the total scattered lightfrom powder on the power modulation frequency� The positive ion signal and theglobal SiH� emission are shown for comparison� Closed symbols are referred to theleft�hand axis� open symbols are referred to the to the right�hand axis� SiH�

�� Si�H��

and Si�H�� represent the mono� di� and trisilicon negative ion groups� respectively�

The positive ion intensity is taken from the integrated positive ion mass spectrum�Substrate temperature �� C� time�averaged plasma power ��W ��



Figure �� Estimation of time�averaged anion densities� as a function of modulationfrequency� extrapolated to anions containing � silicon atoms polymerization ratesassumed independent of size for anions of six or more silicon atoms�� Insets show thetime�varying density during a modulation cycle for three frequencies� at �� Hz� thepolymerisation chain has insu�cient time to propagate to the highest masses� � kHz�the elementary anions are lost before signi�cant polymerisation can occur� and at ��kHz� all anions are trapped and high densities are reached ��



author�s� W�H�M� Lodders

title Powder formation in silane plasma�s�

Distribution

Nat�Lab��PI WB�PRL Redhill� UKPL�NAP Briarcli Manor� USALEP Limeil�Br evannes� FrancePFL Aachen� BRDCP!T WAH

Director� Dr� G�E� Thomas WY Department Heads� Dr� M�H� van Maaren WB �

Dr� A�H� van Ommen WAY �Abstract

W�A�M� Brankaert Nat�Lab� WB �Dr� J� Bruinink Nat�Lab� WB �Dr� G� Cnossen Nat�Lab� WB �Ing� J�P� Damen Nat�Lab� WB �Dr� R� van Asselt Nat�Lab� WB �Dr� J�A�M�M� v� Haaren Nat�Lab� WB �A�G�H� Verhulst Nat�Lab� WB �Dr� U van Slooten Nat�Lab� WB �G�G�H� van de Spijker Nat�Lab� WB �Dr�Ir� H� Cornelissen Nat�Lab� WB �Dr�Ir� L�J�M� Schlangen Nat�Lab� WB �Ing� F�A�M� Paulissen Nat�Lab� WB �Ing�J� van den Eerenbeemd Nat�Lab� WB �Ing� T�h� van den Donk Nat�Lab� WB �Dr� S� Stallinga Nat�Lab� WB �Dr�Ir� K�E� Kuijk Nat�Lab� WB �

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Lic� A� Geelen�Snijkers Nat�Lab� WB �T�C�T� Geuns Nat�Lab� WB �Dr� M�T� Johnson Nat�Lab� WB �Ing� W� Lodders Nat�Lab� WB �Dr� G� Oversluizen Nat�Lab� WB �Ing� A�A� van der Put Nat�Lab� WB �Dr� T�J� Vink Nat�Lab� WB �Ing� R� Verbeek Nat�Lab� WB �



Dr� S� Battersby PRL RedhillDr� J�A� Chapman PRL RedhillDr� S� Deane PRL RedhillI�D� French PRL RedhillDr� I�G� Gale PRL RedhillDr� D�T� Murley PRL RedhillDr� J� Sandoe PRL RedhillDr� P� Saraga PRL RedhillDr� J�M� Shannon PRL RedhillDr� A� Knapp PRL RedhillDr� J� Chapman PRL Redhill

Dr� N�A�J�M� van Aerle FPD Techn� Centre WAY �Dr� S�J� Bijlsma FPD Techn� Centre WAY �Dr� J�W� Lenderink FPD Techn� Centre WAY �Ing� H� Kuntzel FPD Techn� Centre WAY �Dr� K�J�B�M� Nieuwesteeg FPD Techn� Centre WAY �Dr� M� Pitt FPD Techn� Centre WAY �T� Sakai FPD Techn� Centre WAY �

Dr�Ir�C�L�M�van der KlauwFPD WAY �T� Jacobs FPD WAY �Ir� A�G�M� Jonkers FPD WAY �

J�C� Stuve FPD General Management WAYp

Drs� A�J� Raap Octrooien WAHIng� A�H�M� Raaymakers FPD Pilot SFHpDr� P�H�A� Spijkers FPD Pilot SFHp


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Compan - pdfs.semanticscholar.org y Conden tial T ec hnical Note Title P o wder formation in silane plasmas Authors WHM Lo dders P art of pro ject Philips Solid State Course Customer