Silicon Wafer Preparation 2ti54

FROM SILICA TO SILICON WAFER The Silicon Single Crystal and Wafers Manufacturing Version 2.1 En

Silicon V2.1 En

VPS

This presentation was prepared for the needs of the company ON Semiconductor with the aim to approximate the production principles of single crystal silicon ingots and silicon wafers. The manufacturing process details, pictures and video clips come from the company TEROSIL, a.s. based in Roznov pod Radhostem, Czech Republic, we appreciate their friendly help in compiling the presentation.

In our effort to continuously improve our products we thank you in advance for your comments, which will help us in the preparing of further versions.

Piestany, August 2001

VPS s.r.o., P.O. Box B-11, Partizanska 31, 921 01 Piestany 1, Slovak Republic tel., fax.: +421 33 7730151, email: [email protected] Silicon V2.1 En

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Contents Introduction What is Inside an Electronic Device? Silicon Silicon - the Structure Silicon - Inside the Single Crystal Crystalline Defects Doping Silicon Wafer Silicon Obtaining Polycrystalline Silicon Czochralski Crystal Growth Czochralski Puller Crystal-Melt Interface Oxygen and Carbon in Silicon Crystal Segregation Coefficient Single Crystal Ingot Ingot Shaping and Testing Cropped Ingot

Clicking on this box will navigate you to the Controlling the Presentation slide

Silicon V2.1 En

Wafer Manufacturing Wafer Edge Grinding Double-Sided Lapping Stress Relief Etching Etching Machine Backside Treatment CVD Equipment Polishing Polishing Machine Chemical Cleaning Inspection Scrubbing Final Inspection Epitaxy Epitaxial Reactor Epitaxial Layer Characteristics Appendix Clean Rooms Some Special Units

4

Introduction

The company TEROSIL, a.s., located in Roznov pod Radhostem, Czech Republic, is producer of silicon single crystals, wafers and epitaxial layers for microelectronic device fabrication. TEROSIL, a.s. is a non wholly owned subsidiary of ON Semiconductor, global supplier of high-performance broadband and power management integrated circuits and standard semiconductors. Silicon V2.1 En

What is Inside an Electronic Device? The If This webasic small remove material piece the of black of matter a material chip is is called a from semiconductor chip. the After package, anwe can see the enlargement silicon. weleads can see leading its structure. up to a small piece of matter inside which the whole function of an electronic device proceeds.

Silicon V2.1 En

Silicon Silicon does is available not occur in great naturally abundance in its elemental on the Earth. state.The It occurs Earth in is made up offorms, compound approximately the principal 40%ones iron (Fe), being28% silicates oxygen and(O quartz. 2) and Quartz (SiO2) isInthe of silicon in thethe semiconductor 14,5% silicon. theprimary Earth´s source crust, silicon is even second most abundant element - the crust contains 28% of silicon. industry.

Melting point

1 413°C

Boiling point

2 355°C

Density

2 332 kg/m3

Hardness

7 on Mohs´s scale

Energy bandgap

Eg = 1,12 eV

Atomic density

5 . 1022 atom/cm3

Silicon V2.1 En

Elements of the Earth Si

Fe

Other O2

Silicon - the Structure ItEach Silicon If wenecessary is move silicon is a chemical crystallographic aatom copy to add has of element this that four structure structure silicon neighbors, from is has the by diamond 1/4 which group of the itIV

3 nm a = 0,54

appropriate in type main forms thelattice. diagonal, Periodic a bond It properties with. istable. both based thefor on original semiconductor a faceand centered the shifted chips cubic structure atoms only when form - the aacube diamond atoms withinatoms type the whole lattice. in itsvolume verticesofand the in theare chip wall arranged centers.exactly according to this structure. Such and arrangement is called single crystal. A view of a fictitious observer inside the silicon single crystal looks like the following picture.

28,0885

Si

14

2,33 g/cm3

Silicon Silicon V2.1 En

Silicon - Inside the Single Crystal

Silicon V2.1 En

Crystalline Defects In screw Any An A fact, atom additional edge imperfection variety dislocation dislocation missing atom of defects from in occupying the can appears the crystalline be does regular described as aexist. site if an crystal structure inbetween Defect extra as atomic site plane is visualization gives considered regular layers has rise been partly sites tocan aainserted defect. vacancy. iscut be called with A defect an into scissors achieved intersticial. thecan crystal. and byinfluence selective shifted each the etching electrical other. of silicon and mechanical surface. The properties crystalline of a crystal. To defects could demonstrate then appear various like demonstrated kinds of crystalline on thedefects a simplified crystalline structure is used (not silicon). microphotograph.

Silicon V2.1 En

Vacancy

Edge dislocation

Interstitial

Screw dislocation

The range Presence Physically, Only a very of of boron small some dopant presence amount chemical concentration ofcauses elements a dopant used a different is - dopants sufficient in themechanism semiconductor infor silicon, doping of can silicon. electric 14 20 3 substantially current The industry unittransfer is of 10 a influence dopant to in 10 silicon concentration of thedopant than silicon phosphorus atoms/cm electric is the number conductivity. or . Silicon arsenic. of lattice dopant Silicon Boron, itself atoms doped 22 3 3 phosphorus, with per contains unit boron volume 5.10 is arsenic called atoms/cm of silicon, the and P-type antimony .usually silicon given arewhile especially in #atoms/cm siliconused doped . forwith this purpose. phosphorus, arsenic or antimony is called the N-type one.

Boron

IV.A

30.97376

V.A

15

28.0855

Phosphorus

74,9216

Si

14

Silicon

P

As

33

Arsenic 121.75

Sb

51

Antimony Silicon V2.1 En

(Negative)

B

5

III.A

Conductivity type N

10,81

(Positive)

Conductivity type P

Doping

Silicon Wafer Secondary Flat

P <100> Primary Flat

<111>

Silicon V2.1 En

A chip For The that silicon crystallographic conductivity wafers next isreason, very slides wafer aresmall, fabricated will many (P is provide or round-shaped. just orientation, N) chips atype by few deeper are cutting and square processed in aThe respect details from silicon millimeters. diameters aof to wafer athe It would together of crystallographic monocrystalline silicon 100,be wafer 125, indifficult, one 150 surface, manufacturing slice orientation silicon mm if not of or iscylinder semiconductor even important more are process. impossible, are encoded pulled commonly for the from - silicon in to wafer amolten used. produce wafer. A properties. relative silicon 100 mm At inposition each the special wafer Inend practice, chip of is equipment. ofprimary individually. about thethe process half orientations andofsecondary the millimeter wafer according is flat thick. cut onupto into pictures Already the each individual wafer. the wafer The are chips. used top material side andofthey issilicon doped are wafer classified and itisishighly Pasor Ntype then. <111> polished. or <100>.

<100>

Silicon Obtaining

Quartz

Although At Metallurgical the very highly first grade step pure, silicon the thisquartz silicon is notsand pure doesisenough not transformed formfor the into thecrystal semiconductor single silicon. lattice. technology. This silicon, It is known Thus known as it is as a converted polycrystalline metallurgical to grade silicon, trichlorsilane silicon or polysilicon. (SiHCl is obtained by chemical can be cleaned reaction byof 3), which quartz The polycrystalline with and carbon electronic grade silicon, the distillation, then(C). this trichlorsilane is reacted next slide will show how it looks like, is the raw with hydrogen (H2) to produce highly purified material single crystal production. electronicforgrade silicon.

SiO2 + 2C

Si + 2CO

Metallurgical grade silicon

Si + 3HCl

SiHCl3 + H2

Trichlorosilane

Trichlorosilane cleaning

SiHCl3 + H2 Silicon V2.1 En

Si + 3HCl

Electronic grade silicon

Polycristalline Silicon

Silicon V2.1 En

14

Chapter 1 Overview Introduction What is Inside an Electronic Device? Silicon Silicon - the Structure Silicon - Inside the Single Crystal Crystalline Defects Doping Silicon Wafer Silicon Obtaining Polycrystalline Silicon Czochralski Crystal Growth Czochralski Puller Crystal-Melt Interface Oxygen and Carbon in Silicon Crystal Segregation Coefficient Single Crystal Ingot Ingot Shaping and Testing Cropped Ingot

Silicon V2.1 En

Wafer Manufacturing Wafer Edge Grinding Double-Sided Lapping Stress Relief Etching Etching Machine Backside Treatment CVD Equipment Polishing Polishing Machine Chemical Cleaning Inspection Scrubbing Final Inspection Epitaxy Epitaxial Reactor Epitaxial Layer Characteristics Appendix Clean Rooms Some Special Units

15

Czochralski Crystal Growth Onthe Reachnig The Both In 1918, this the goal crystallographic polysilicon pull crystal the final initial enclosed rate Czochralski growing isthe phase, is tophase, isprogressively desired transform then charge video, crystal the the decreased orientation described diameter pull ispull there raw and melted speed rate grown materials the are aand of is in crucible is "shoulder" the process the high and the increased the particular seed into quartz pulled to diameter rotate in maintain awill is which silicon out tobe asofa single adapted crucible. a formed the indicated reduce phases small crystal melt. crystal crystal. the on diameter ofby The The by athe is crystal growing single arrows. increased crystal is critical The growing pulled for diameter. quartz crystal crystal. the The seed process from crystal to growing melt crucible ingot the isaItWhen then parameters melt. desired has is shape. growth consumed, crystal. dipped is to the Since loaded be size. crystal process. chosen This into that then This with the body must this inthe method polysilicon accordance silicon procedure second be therefore is removed controlled melt. part has the is (see from to of been The called crucible are the photo) the seed the significally final initial necking melt temperatures, lifts isand silicon growth rotated atoquick the and keep refined wafer dopant. isand its temperature melt called purpose the orientation and simultaneously level A pull crowning. remain seed rate, is at to the the the most popular crystal required. pulled-up eliminate rotation same change height. isis rates also dislocations from induced. method and loaded thelow melt. A thin in to from pressure the A produce "tail" crystal the puller. on crystal. argon high grows the crystal ambient. quality at theend single crystals. the interface reduces following impactthe of thermal crystallographic shock onstructure the rest of the crystal. seed. Quartz crucible

Seed chuck rotation Seed Shoulder chuck Seed Neck Crown

Graphite crucible (susceptor)

Body Tail Melt

Graphite heater

Crucible shaft Crucible rotation

Silicon V2.1 En

Czochralski Puller

Argon inlet

A graphite Finally, The An isolation quartz lift whole Czochralski (seed theheating system last crucible valve chuck part puller allows is element is of and placed the ed the schematical cable) access component heat isinplaced vacuum zone holds by to upper drawing ais around the graphite containing achamber thermal seed chamber can the crucible and be the with shield siliconkeeping which graphite eliminating growing water-cooled while compared serves melt. crystal crucible with the The jacket. simultaneously the heat real during crucible - controled susceptor. equipment losses. Monitoring thematerial process ambient aspicture system the must enabling heat innext. lower be (pyrometer susceptor. chosen the vacuum such and that itcrucibles Both controlled camera) chamber. reacts and pullvery computer rate areslowly placed and control rotation. with on a the the graphite melt. growth The shaft process. only enabling material the rotation thatand canlifting. be used is quartz.

Quartz crucible

Isolation valve

Seed chuck rotation Cable Seed chuck Camera (diameter control)

Graphite crucible Graphite heater Thermal shield

Visor

Optical pyrometer

Crucible shaft

Water cooled jacket

To vacuum pump

Electric current lead-in

Silicon V2.1 En

Crucible rotation

Crystal-Melt Interface Melt A The During good fundamental area crystallization flows crystal control between are growth, also of the process takes the generated temperature the melt place behind melt and by at flow crystal the the atpattern the rotation crystal-melt growth has interface to inof ofthe beathe between maintained interface. crucible crystal involves and plays the The the atcrystal the an shape crucible the important silicon transformation and of the and the freezing interface role by melt pulling ofis point. crystal-melt of crucial. directly aofliquid This theAis good into thea solid. Toof control coldest influences interface crystal. During region grow shape the theheat acrystalline in crystal and crystal, the flow dopant melt, growth, throughout the perfection otherwise atoms variation. a combination of the and solidification the The interface the liquid of is must the will impurity spontaneous crystal occur critical organize and distribution incondition crucible other melt themselves parts flow rotation throughout fororiginates as that. well. as is they used the Heat from become section. toinputs generate temperature part The and the of the solid.melt outputs concave differences desired must shape This inflow be the underlines helps monitored -melt right to- bottom left remove the and bottom importance picture. be dislocations regulated picture. of good to and is controlproper insure maintained of the during process crystal thegrowth. at crystal the interface body growth. between the melt and the crystal.

Crystal cross section (black)

Crystal - melt interface

Heat flow

Crystal rotation

Melt flow

Convex crystal-melt interface Heat input Heat output no rotation Silicon V2.1 En

Melt flow

Concave crystal-melt interface Crucible rotation

Melt

Oxygen and Carbon in Silicon Crystal Traces of Oxygen Carbon impurities isother the most impurities originate common are from impurity also the present polysilicon in silicon in the crystal. charge crystal. Its and main the from Their source concentration reaction is thebetween crucible is lowerthe material than graphite that- quartz ofheating carbon (SiO element and they 2). This and accumulate silicon in the melt evaporated residue leftfrom inmelt. the thecrucible. melt. Carbon surface is inmonoxide with the silicon The reaction has muchthe lower concentration than oxygen in the crystal. between silicon melt and the crucible produces silicon monoxide (SiO). Most of the silicon monoxide evaporates from the melt surface but a small quantity stays in the melt.

SiO + 2C CO, CO2 SiO

SiC + CO

CO, CO2

SiO

SiO

SiO

SiO Quartz crucible

Graphite heater Graphite crucible Silicon V2.1 En

Segregation Coefficient

Element

Dopant Concentration/Resistivity vs. Ingot Length (example)

10

dopants

metals

The One In For Most the example, dopant of ofcrystal the elements key concentration growth phosphorus operations have process, segregation in has the crystal there a crystal segregation are coefficient pulling will twois be phases coefficient less the introduction lowest thanatunity. the of at 0,35. the interface Due oftop aThat to specific end this, -is, the and near only solid amount thethe ahighest crystal part interface, ofof dopant and at the into liquid the dopant bottom the is concentration end crystal. melt. integrated of the Between The ingot. dopant into in the the An is crystal example two crystal. added phases, will The to ofbe the arest 0,35 is polysilicon redistribution times rejected dopant the concentration back concentration charge of into thethe ordopant melt profile melt. of in phosphorus takes Italong the results crucible. place. crystal in in dopant This the is is measured melt. accumulation illustrated Therefore, on in term the in the in graph oforder melt a segregation below. as to achieve crystal Heavy coefficient growth ametals given as a ratio dopant proceeds. have very level of low Inconcentrations in turn, segregation thebecause crystal, the coefficients the of the dopant concentration dopant which in the two phases. concentration increases results in further in the in melt, the material melt the has purification. dopant to be concentration appropriately increases in the higher. crystal as well.

8

Segregation Coefficient 0,000008 0,000025 0,00003 0,0004 0,0007 0,023 0,07 0,3 0,35 0,8 1,25

Fe Au Ni Cu N Sb C As P B O

Segregation Coefficient: k =

CLIQUID

8

7

6

6 800

0

200

C(p) = C0(1-p)k-1 p - normalized length (p = 1 for Lmax) k - segregation coefficient Silicon V2.1 En

400 L [mm]

600

Resistivity [mcm]

Concentration [1019cm-3]

concentration

resistivity

CSOLID

CSOLID = 3,5 x 1018 cm-3

CLIQUID = 1,0 x 1019 cm-3

Single Crystal Ingot

Silicon V2.1 En

21

Chapter 2 Overview Introduction What is Inside an Electronic Device? Silicon Silicon - the Structure Silicon - Inside the Single Crystal Crystalline Defects Doping Silicon Wafer Silicon Obtaining Polycrystalline Silicon Czochralski Crystal Growth Czochralski Puller Crystal-Melt Interface Oxygen and Carbon in Silicon Crystal Segregation Coefficient Single Crystal Ingot Ingot Shaping and Testing Cropped Ingot

Silicon V2.1 En

Wafer Manufacturing Wafer Edge Grinding Double-Sided Lapping Stress Relief Etching Etching Machine Backside Treatment CVD Equipment Polishing Polishing Machine Chemical Cleaning Inspection Scrubbing Final Inspection Epitaxy Epitaxial Reactor Epitaxial Layer Characteristics Appendix Clean Rooms Some Special Units

22

Ingot Shaping and Testing During The Crystallographic pulled crystal photograph the cropping ingot section of is orientation cut finished isofplaced into the crystal, individual silicon ofinthe thecylinder a single grinding few sections. thin crystal axis machine slices This iscylinder given are operation and removed by with the theflat isseed for is called testing. machine orientation. on the cropping. next Usually grinds slide. To identify resistivity down Each the section a radial crystal profiles, iscrystallographic examided until oxygen the target and for defects. carbon orientation diameter Also, ofofthe the the ends ofathe concentration cylinder crystal isflat reached. ingot isand ground are crystallographic removed. into it. Knowing defects the orientation, are tested. the Theposition set of slices of the flat allows is accurately to the determined variation of bymeasured X-ray diffraction. parameters.

X-ray source

Detector

Silicon V2.1 En

Cropped Ingot

Silicon V2.1 En

24

Chapter 3 Overview Introduction What is Inside an Electronic Device? Silicon Silicon - the Structure Silicon - Inside the Single Crystal Crystalline Defects Doping Silicon Wafer Silicon Obtaining Polycrystalline Silicon Czochralski Crystal Growth Czochralski Puller Crystal-Melt Interface Oxygen and Carbon in Silicon Crystal Segregation Coefficient Single Crystal Ingot Ingot Shaping and Testing Cropped Ingot

Silicon V2.1 En

Wafer Manufacturing Wafer Edge Grinding Double-Sided Lapping Stress Relief Etching Etching Machine Backside Treatment CVD Equipment Polishing Polishing Machine Chemical Cleaning Inspection Scrubbing Final Inspection Epitaxy Epitaxial Reactor Epitaxial Layer Characteristics Appendix Clean Rooms Some Special Units

25

Wafer Manufacturing The damage When first saw cutting step is made comes in wafers the of production afrom from thinthe astainless crystal, fact of silicon that itsteel issawing desired wafers withprocess afrom tohole a crystal in make is really the center. a flat aingot form cut Aisof at nickel sawing. grinding. a specific matrix A graphite The angle withdamage imbedded with beam respect exists is diamond attached to the to the crystal particles crystal wherever orientation isthe plated with blade an around and comes adhesive to waste the in inner toashold little edge with the material ofwafer the thecrystal. blade. as after the saw This possible Therefore, diamond-nickel blade with theahas damaged minimum cutmatrix through material of provides damage thehas ingot. of atosurface the bewafers. removed which is used For in the that subsequent to the cut blade the silicon is steps. cooled ingot. Onand the rinsed enclosed by water video,with surfactant. there is a shot of sawing process.

VIDEO 352 x 288

Water

Stainless steel core Silicon

Nickel matrix with imbedded diamond Damage particles Silicon V2.1 En

Wafer Edge Grinding Aftergrinding The wafer sawing, is placed wheel the wafers isona vacuum disc havewith anchuck groove edgeand with of sharp corners. slowly desired turned "bulletas nose" The theedge grinding shape is ground ofwheel, wafertowhich edge. form is a There bullet rotating are embedded shaped at highedge. diamond speed, This isparticles increases forced against in edge the groove. the strength wafer edge. and make the edges less prone to chipping in later processing.

High speed

Low speed Silicon V2.1 En

Double-Sided Lapping Theabrasive During An next silicon lapping, step wafers slurry inwafers wafer (aluminium in carriers production are placed and oxide the is in called Al abottom O3 and 2carrier lapping. are lapping driven plate Purpose between visible of two this step on the iron is double tomade make sided lapping wafer suspended inare water withcast surfactant) is fed to the surface plates. planetary The smooth, lapper carrier video. isand thinner To parallel. see than thethe wafers wafersthe wafers surface asflat they are moved between allowingplates. movement both thesides upper lapping the wafer plate be is lifted lapped for lapping This of removes thetosilicon and simultaneously. demonstration. the end of the video there is leaves behind aAtmore uniform surface. Wafers the machinethe during the plates lappingare are complete very flat because lapping process. extremely flat.

Lapping plate

Slurry

Carrier

VIDEO 352 x 288

Wafer Gearing

Lapping plate

Silicon V2.1 En

Stress Relief Etching In both Since One Another The figure method lapping forms form below of of allows etching etching etching, shows only the used aalkaline to relative wafers remove on silicon and is the the acid, bulk use of an wafers comparison there thealkaline are saw is acid advantages damage ofhydroxide, etching. the etch and and Arates always common such disadvantages ofas leaves a potassium typical mixture a thin to uniform hydroxide used acid choosing and forlayer acid aa(KOH). typical specific etching of damage, In alkaline form. this is HNO method, The some etch. and other It the can HF. onwafers be the 3 table method are seen bottom dipped that left must the side inadditional KOH acid beshows used etch andto acontinues water comparison. remove mixture the to etch for Sometimes, chemicals are added damage about silicon The picture 2wafer minutes. from ofatlapping. aachemical The high mixture rate This for damage is asusually long equipment needs asatthe to the mixture to make theetching reaction more to elevated two and beare chemical removed kept temperature inbath while . causing on ofTherefore the about as 100°C. little slide. the acid Then controllable. In anyiscase, thenext acid etching additional the etch wafers must be controlled dipped as process possible. into very a DI closely water Typically, to bath end the to process is damage aare vigorous which needs chemical stop up with anyan remaining etching acceptable is reaction. used. wafer. tight control as it has no self limiting properties.

Alkaline Etching Si + H2O + 2KOH

K2SiO3 + 2H2

Acid Etching 3Si + 4HNO3 + 18HF

3H2SiF6 + 4NO + 8H2O

Si + 4HNO3 + 6HF

H2SiF6 + 4NO2 + 4H2O

Relative etching rates vs. time Acid

Gives a surface that contains etch pits

Gives a smooth surface

Constant etch rates over life of bath

Etch rate varies

Self limiting, easy to control

No self limiting, hard to control accurately

Does not release EHS hazard

Releases gases that must be scrubbed

Acid Etch rate

Alkaline

fe see W a

cturing r Manufa

Alkaline Time (Stock Removal)

Silicon V2.1 En

Etching Machine

Silicon V2.1 En

Backside Treatment A batch For Silicon Polysilicon wafers dioxide of silicon that on the can are wafers backside be highly used indoped carrier prevents as a backseal. and prepared out are going The diffusing for deposition layer to go as is through well deposited is on as getters the a high on bottom the temperature heavy wafer picture. metals by You process, chemical from can see the abulk avapor chemical layer of deposition. the is deposited wafer. vapor deposition Normally The on oxide the a back acts silane side 4of strictly (SiH equipment ) source as theawafer on sealant. is the used tonext prevent for slide. polysilicon the dopant from out diffusing. deposition.

Oxide Deposition SiH4 + O2

420°C

Polysilicon Deposition SiH4 620°C

Silicon V2.1 En

SiO2 + 2H2

Si + 2H2

CVD Equipment

Silicon V2.1 En

Polishing The One A polishing purpose video of theshows polishing pad of wafer isthe mounted techniques wafers polishing on unloading the isistobottom the produce template right plate. after a very The smooth, mounting soft polishing. insertflat, method. A ispolishing necessary damage Theequipment free wafers to hold silicon are the is surface. situated wafers shown The in on inplace a the round polishing template when next slide. the attached step wafers is, are unlike onmounted a carrier lapping, to and atheset polishing on a soft chemical/mechanical polyurethane equipment with insert the surface in process. the template. facing Thisdown. difference The insert The bottom is has thea reason porous plate and structure. polishing carriersproduces When are rotating theawafer much around issmoother pressed their own against final axis. surface the water than soaked lapping. insert, it is held against it. Slurry for Silicon Polishing The polishing slurry consists of silica (silicon dioxide, SiO2) particles in aqueous suspension with an organic alkali and a surfactant.

Wafer

Carrier

Slurry

Insert Template Polishing pad Bottom plate

Silicon V2.1 En

Polishing Machine

Silicon V2.1 En

Chemical Cleaning At the After The most chemical the previous this time wafers cleaning, common commonly of chemical cleaning steps have the method some used been wafer operation cleaning, method metals of polished, surface cleaning is the may tocomplemented wafers is remove they still the free have remain wafers of have aa large after thin particles on by contaminants, megasonic the native polishing number wafer is oxide the surface. of cleaning. is however SC1 contaminants layer a wet (Standard The on cleaning small Megasonic top cleaning and amount on Clean consisting the agent waves 1) surface. contaminants ofsolution. particles for of are the In general, several are This metal acoustic may mostly be mixture contaminants chemical still these waves on present. istop contaminants the ofsteps. of very hot is theaNH high The oxide mixture frequency first are or and of embedded one particles, HCl H2is O(about ainhot organic water. H within O2 in 4OH 2and 21 residuals mixture it. MHz). The The video The role ofand sulfuric on waves of right the metallic subsequent exert acid shows ions. and forces a hydrogen cleaning The step, onSC2 chemical particles diluted line peroxide and cleaning onawafer shot Ammonium water. This mixture hydroxide is known under-etches as particles (Standard is called hydrofluoric surface into designed the2). Piranha. megasonic and to acid, help remove It to decomposes is cleaning detach to oxidizes etch them. out bath. virtually the native any oxide organics and attached Clean to The the mixture surface andthem. eliminates and reacts attractive with on polishing the wafer slurry residuals. into carbon dioxide and water. forces. metals on Hydrogen thesurface silicon peroxide surface is and oxidizing removes agent them. to grow thin clean oxide layer on the wafer surface, which makes it hydrophilic and prevents particles re-deposition.

H2SO4 + H2O2 (130°C)

H2O + HF

H2O + NH4OH + H2O2 (70°C)

H2O + HCl + H2O2 (70°C) Silicon V2.1 En

Particle Metallic ion

Organic residual Native SiO2

VIDEO 352 x 288

Inspection After A The measure measurement total video the wafers indicator shows of thehave ofashape reading the non- been consistency deformation (TIR) polished automatic is aofmeasurement and of a wafer a cleaned, wafer is they is warp. thickness that inspection are Warp only ready isline. concerned is total the to thickness be measure inspected. with the variation of maximum front During side (TTV). the difference of a It is inspection between the wafer. difference The the process, way highest between this measurement the and the resistivity lowest maximum location and is made and geometrical of is the by parameters centerline minimum reference thickness to ofare aa plane wafer measured ofthat with a wafer. is respect by parallel non- totoreference the vacuum methods. plane chuck defined that the by wafer three is pedestals mounted on. near The theTIR wafer is the edge. difference between the height of the highest peak and the deepest valley on the front of the wafer.

VIDEO 352 x 288

Wafer centerline

Tmax

hmax

Wafer Wafer

Tminh

min

Dmax

Dmin

Warp TTV TIR===(D T hmax T hmin max max -- D min) / 2

Silicon V2.1 En

Reference plane

Vacuum chuck

Scrubbing Wafer The During wafers scrubbing the scrubbing are cleaned with aqueous thetoPVA remove brush ammonium particles is very and metal contamination hydroxide effective for (NH particle removal. but after across After inspection the DIwafer water may surface rinse have 4OH) flows anremove and increased drying the wafers number are of prepared particlesfor onfinal the inspection surface to particles. Simultaneously the again. and packaging. The has to be used for finalfibers brushing is scrubbing made by polyvinil alcohol (PVA) mechanical/chemical Both cleaning. the subsequent final into whichthe do scrubbing not scratchand the wafer when brought inspection arewith realized in clean rooms of class 10. direct the wafer surface. The video on right shows a scrubbing operation.

Silicon V2.1 En

VIDEO 352 x 288

Final Inspection

Wafer Diameter: TTV: TIR: WARP:

100, 125, 150 mm < 5 µm < 4 µm < 30 µm

(typical for 100 mm wafers)

Particles >0,5 µm Metal Contamination:

<5  3x1010 atoms/cm2

for more specification: www.terosil.com Silicon V2.1 En

38

Chapter 4 Overview Introduction What is Inside an Electronic Device? Silicon Silicon - the Structure Silicon - Inside the Single Crystal Crystalline Defects Doping Silicon Wafer Silicon Obtaining Polycrystalline Silicon Czochralski Crystal Growth Czochralski Puller Crystal-Melt Interface Oxygen and Carbon in Silicon Crystal Segregation Coefficient Single Crystal Ingot Ingot Shaping and Testing Cropped Ingot

Silicon V2.1 En

Wafer Manufacturing Wafer Edge Grinding Double-Sided Lapping Stress Relief Etching Etching Machine Backside Treatment CVD Equipment Polishing Polishing Machine Chemical Cleaning Inspection Scrubbing Final Inspection Epitaxy Epitaxial Reactor Epitaxial Layer Characteristics Appendix Clean Rooms Some Special Units

39

Epitaxy For Epitaxy The After If there particular process result theare issurface the ofany proceeds the applications growth phosphine process etching ofatthe is high is there (PH finished, silicon from temperature molecules aa layer few need thetoon silicon tens toabout the present, form silicon 1200 a 3)is layer wafer °C. chloride micrometers Hydrogen of surface. high (SiHCl resistivity thick flows The vapors epitaxial layer past material are has thelayer. introduced. incandescent theon same top of crystallographic SiHCl lower silicon the phosphorus dope the growing epitaxial 3)atoms 3 reacts resistivity properties wafers. On enclosed When material. ascompounds the hydrogen video, substrate, Theatepitaxial there chloride but areittemperature. growth is the can added, shots have used itof astarts different thefor withthe layer. present Boron hydrogen can a high be used forisdoping The as this purpose. dopant reacting wafers concentration with reaction silicon on a susceptor and or even itfree etches different andthe their wafer dopant. unloading. surface result well. ofloading this are silicon atoms that settle away. You can Itsilicon is also important see thesurface tocontrol remove board all the of its an contaminants epitaxial or on the wafer following crystal lattice surface reactor. defects of the silicon structure. structure.

H

H

Cl Cl Si H H H Cl

H Cl

H Cl H P H H

Silicon V2.1 En

H Cl H

H

Cl Cl Si H Cl

Si Si

Si P

Si Si

H

VIDEO 320 x 240

H Cl H Cl Si H H Cl H Cl

Epitaxial Reactor

N2

H2

HCl

SiHCl3

PH3

At this extremely Epitaxial During the reactor process, is high an the temperature, equipment chamber with forthe the the process growth wafersofis the epitaxial flushed proceeds with in the nitrogen layer. way Silicon described and hydrogen. wafers onare theIn loaded slide the Epitaxy. on a graphite hydrogen The susceptor block environment -with susceptor. wafers the is susceptor The cooled susceptor down with wafers is then placed and is insidenitrogen warmed after a quartz up byflushing the glass induction bell-shaped it is taken heating out chamber. at from thethe Around the chamber,ofthere temperature chamber. about is 1200°C. an induction heating coil.

B2H6

gas exhaust Silicon V2.1 En

Epitaxial Layer Characteristics

Wafer Diameter: Epi Layer Thickness: Epi Layer Resistivity:

100, 150 mm 3 - 50 µm 3 - 50 cm

for more specification: www.terosil.com Silicon V2.1 En

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Chapter 5 Overview Introduction What is Inside an Electronic Device? Silicon Silicon - the Structure Silicon - Inside the Single Crystal Crystalline Defects Doping Silicon Wafer Silicon Obtaining Polycrystalline Silicon Czochralski Crystal Growth Czochralski Puller Crystal-Melt Interface Oxygen and Carbon in Silicon Crystal Segregation Coefficient Single Crystal Ingot Ingot Shaping and Testing Cropped Ingot

Silicon V2.1 En

Wafer Manufacturing Wafer Edge Grinding Double-Sided Lapping Stress Relief Etching Etching Machine Backside Treatment CVD Equipment Polishing Polishing Machine Chemical Cleaning Inspection Scrubbing Final Inspection Epitaxy Epitaxial Reactor Epitaxial Layer Characteristics Appendix Clean Rooms Some Special Units

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