CVD Process introdution

1、CVD Process IntroductionContentWhat is CVDDCVD Application in IC ProcessCVD Process Low K materialsWhat is DCVD Dielectric-CVD is a synthesis process in which the atomic constituents react in the vapor phase near or on a heated substrate to form a nonvolatile Solid Dielectric Film. It should combine

2、 several scientific and engineering philosophy composed of thermodynamics, kinetics, plasma physics and chemistry. Thermodynamics:A+B = C+DG (Gibbs free energy) = G product G reactantIf G The reaction is feasibleT=1000K, R1 is not feasible but R2 is feasibleReaction 1, It not feasible at 800K, but f

3、easible at 1400KWhy DCVD 1. High purity deposition can be achieved.2. A great variety of chemical compositions can be deposited.3. Some films can not be deposited with adequate film properties by any other method.4. Good economy and process control are possible for many films.DCVD Application Oxide(

4、un-doped & doped) ; Nitride are the typical dielectric film. Oxynit film property is normally between Oxide and Nitride.DCVD ApplicationPre-metal Dielectric(PMD)Low k, trap mobile iron and low thermal thermal budget are required. Inter Metal Dielectric(IMD)Low K, void free gapfill, somth surface and

5、 low process temp. are required Final passivationLow dep. Temp, high strength and moisture isolation ability are required ARC and Hardmask STIShallow Trench Isolation (STI) Application: Isolation region between active area, used beyond 0.25um. Required properties: Excellent gap filling abilityNo ind

6、uced leakage current Process tools: APCVD O3-TEOS (WJ) SACVD O3-TEOS (AMAT)Since O3-TEOS has the ability to achieve excellent step coverage and conformality, led to good gap filling ability. HDP SiH4 / O2 DCVD ApplicationInter Layer Dielectric(ILD or PMD) Application: Insulator layer between gate an

7、d metal-1 Required properties: USGPrevent B, P of BPSG film from diffusing into active areaWont degrade hot carrier integrationBPTEOS Planarization (0.5um, non CMP technology)Good gap filling ability, no void between poly lines Process tools:USG: PEOX (SiH4) or PEOX (TEOS)BPSG: APCVD BPSG, PECVD BPS

8、G, APCVD BPTEOS, SACVD BPTEOSDCVD ApplicationThe characteristics of BPSG film Why doped oxide for ILD applicationPlanarizationGettering Why add P into glass film?Mobile ion getteringCrack resistance from thermal cycleLower down the melting temperature of oxide film.Too high P concentration will caus

9、e metal corrosion. Why add B into glass film?Lower down the melting temperature of oxide film.On a weight percent basis, boron is 1.5 times more effective than in the reflow process than phosphorus. How to measure chemical composition of doped oxideXRF good for P% measurementFTIR good for B% measure

10、mentDCVD ApplicationInter Metal Dielectric (IMD) Required properties: 1. low dielectric constant for frequencies up to 20 MHz, in order to keep capacitance between metal lines low.2. High breakdown field strength (5MV/cm).3. Low leakage,even under electric fields close to the breakdown field strengt

11、h, Bulk resistivity should exceed 1015-cm.4. Low surface conductance. Surface resistivity should be 10155. No moisture absorption or permeability to moisture should occur.6. The films should exhibit low stress, and the preferred stress is compressive (-5x108 dynes/cm2), since dielectric film s under

12、 tensile stress exhibit more of a tendency to crack.DCVD Application7. Good adhesion to aluminum, and of aluminum to the dielectric.8. Good adhesion to dielectric layer above or below. Such dielectric layers could be thermal oxides.doped-CVD oxides,nitrides, oxynitrides, polyimides, or spin-on Glass

13、es.9. Permeable to hydrogen.this is important for IC processing. In which an anneal in a hydrogen containing ambient must be used to reduce the concentration of interface states between Si and the gate oxides of MOS devices10.No incorporated electrical charge or dipoles. 11.Contains no metallic impu

14、rities.12.In the case of doped oxides,good dopant uniformity across the wafer, and from wafer to wafer.13.Contains no residual constituents that outgas during later processing to the degree that they degrade the properties of other layers of the interconnect systemInter Metal Dielectric (IMD)DCVD Ap

15、plicationIMD scheme roadmap: PEOX+SOG+PEOX (B) (0.8um technology) PEOX+(SOG+SOG partial E/B)l+PEOX (C) (0.6um technology) PEOX+(O3-TEOS)+PEOX+ (SOG+SOG E/B)l +PEOX (D) (0.5um technology) PEOX+(O3-TEOS)+PEOX+CMP (E) (0.25um or 0.35um technology) HDP+PEOX+CMP (E) (0.25um or0.35um technology) PEOX+HDPF

16、SG+PEFSG+CMP +PEOX (E) (0.18um technology)The definition of degree of planarization DCVD ApplicationPassivation layer Desired properties of a passivation-layer material1. Provides good scratch protection to underlying circuit structures.2. Impermeable to moisture, as moisture is one of the main cata

17、lysts for corrosion.3. Exhibits low stress, preferably compressive 4. Conformal step coverage.5. Good thickness uniformity.6. Impermeable to sodium atoms and other highly mobile impurities.7. Easily patterned.8. Good adhesion to conductors, as well as to the inter-level dielectric beneath the last l

18、evel of metal.DCVD ApplicationPassivation scheme evolution PE-OX(SiH4)/PE-SiN UV-NiT/SOG/UV-NiT for the purpose of UV transparent Oxynitride/SOG/PE-SiN HDP oxide/PE-SiNPassivation PE-SiN:SiH4+NH3+N2 -SixNyHz+by products 400CSince the introduction of NH3, hydrogen bonding exists during reaction. Ther

19、efore, its kind of physisorption and has better step coverage.DCVD ApplicationDielectric ARC(Antireflective coating)The demand for smaller CD has necessitated the move to lower exposure wavelengths in microlithography. But this gives rise to one problem - control of reflection from the substrate.DCV

20、D ApplicationDielectric ARC vs. Organic ARCDCVD ApplicationDielectric ARC vs. Organic ARCDCVD ApplicationAs illustrated for same ARC thickness, the effect of inorganic ARC film to suppress reflectivity is much better than that of organic film. 1. CVD deposition process introduce 2. APCVD&LPCVD Proce

21、ss 3. PE CVD Process 4. HDP Process CVD PROCESS CVD Deposition ProcessTRANSPORTREACTIONThe deposition rate is depended on the step with lowest rate.Depend on the activation energy of the reaction and the gas flow condition in the reactor.CVD Deposition ProcessSurface Reaction Limited Region:Lower te

22、mperatureDepend on the rate at which the reactant are consumed by the surface reaction processGas phase diffusion rate is not so importantStrongly influenced by the wafer temperature.Weakly influenced by the flux of reactant to a wafer surfaceThe deposition rate also influenced by the surface concen

23、tration for the Mass Transport limited regimeHigher temperatureDepend on the rate at which gas cross the boundary layer Transport: gas phase diffusion.Weakly influenced by the temperature.Strongly influenced by the flux of reactant to a wafer surface The transport rate is influenced by the concentra

24、te gradient in the bulk gasCVD Deposition ProcessAPCVD & LPCVD SiO2 SiH4(g)+ O2(g) - SiO2(s) + 2H2(g)4PH3(g)+5O2(g) - 2P2O5(s) +6H2 (g)PEOX (TEOS) PEOX (SiH4)Arrive angleArrive angleCVD Deposition ProcessCVD Deposition MethodsSTEP COVERAGE:Migrate ability: As the reactants adsorb on the surface and

25、then rapidly migrate along the surface before reaction, the resulting films will have a uniform surface concentration on the substrate and a constant thicknessArrival Angle: the deposition rate is proportional to the arrival angle of the gas molecules if the absorbed reactants predominantly do not m

26、igrate.Mean Free Path: longer MFP will decrease the effect of Arrival Angel on step coverage.Uniform coverage resulting from rapid surface migrationNonconfirmal step coverage for long mean free path adn no surface migrationNonconfirmal step coverage for short mean free path adn no surface migrationT

27、wo methods making the reaction occur on the wafer surface possible:A. Heating:Increase wafer temperature:Si3N4 deposition (740C 780C)NH3 + SiH2Cl2 - Si3N4 + By products Get energy from a glow discharge(plasma)Plasma Enhanced CVD (PECVD)1. e- - e-* RF electric field2. e-* + A + B -A* + B* + e-*3. A*

28、+ B* -A*(ad) +B* (ad) - migrate along surface - to form new bonds and film The introduction of plasma can reduce the reaction temperature significantly.B. Change the reaction species from A to A*:PECVD and High Density Plasma(HDP)PE CVD ReactionHDP CVD ReactionPlasma transfer the energy from electri

29、c field into the reactant gases, allowing the deposition on the substrate at a lower temperature.Low Density Source (CCP)High Density Source (ICP)Plasma Density (n/ml)1E8 1E101E11 1E12Ionization (%)0.01 0.10.1 10Dissociation (%) 50%Electron Temp. (eV)1 52 7MFP (cm) (2eV Temp)0.001 0.10.25 25Low Dens

30、ity source vs. High Density SourceHDP ConceptInsitu Dep. And Sputter1. Dep. 2. Sputter 3. Dep.Sequential Dep. And SputterAr+D/S Ratio and E/D ratio D/S ratio(Deposition to sputter) or E/D ratio (Etch to deposition) is the key Parameter to identify chamber condition or recipe gap fill capabilityCVD P

31、roblems, Process Control 1. Chamber matching, chamber to chamber variation. 2. Film property control. Particle; metal contamination; pin hole; first wafer effect control. 3. Throughput(dep. Rate; clean rate and frequency; handling time 4. Gap fill capability; especially for HDP&BPSG process. 5. Plas

32、ma and stress&thermal induced metal damage Low-k dielectricInterconnect RC delay degrades with technology scaling.0.13 um: Cu metallization to reduce R. 90 nm: Low k ILD to reduce C.Low k - Poor mechanical strength:adhesion, hardness, modulus and cohesive strengththermal conductivity/stabilitypatterning selectivityBusiness not as usual: Big integration challenges for yield, reliability and packaging. Low k Development C