Arthur Sherman - Chemical Vapor Deposition for Microelectronics (779637), страница 36
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For plasmaenhanced CVD dielectric films, at least, there can be as much as 25 atomic %hydrogen in the film, and its concentration is definitely of interest.One technique that has been able to measure hydrogen concentrationin a thin film and do a depth profile, without reliance on standards, uses aresonant nuclear reaction technique. 16 In this procedure, the nuclear reactionbetween a hydrogen atom (IH) and an energetic nitrogen-15 atom eSN) isused.
That is(13)and the 'Y-ray comes off at 4.43 MeV. To probe for 1H, the sample is bombarded by 15 N ions and the yield of 4.43-MeV 'Y-rays is measured. Th is reaction has a strong resonance when the 15N impacts the proton at 6.385 MeV,and this fact can be used to obtain the depth profile, as shown in Figure 32.If the 15 N beam energy is set exactly at 6.385 MeV, we will observe thehydrogen at the surface. By increasing the 15 N beam energy above 6.385 MeV,it will penetrate the film and begin to lose energy. When its energy drops backto 6.385 MeV, another burst of 'Y-rays will be observed, and their frequencywill indicate the hydrogen concentration within the layer.
The position withinthe layer at which the 15 N beam energy will drop back to 6.385 MeV can becalculated from available energy loss data.Using this technique, the hydrogen content of two PECVD silicon nitridefilms was measured, and the results are shown in Figure 33. The depth resolution obtainable was 50 to 100 A and is sensitive to better than one part perthousand.The principal drawback with this procedure is the difficulty in findingthe expensive and sophisticated accelerator necessary to achieve the >6 MeV15N ion energies. Clearly, it is not a production procedure.210Chemical Vapor Deposition for MicroelectronicsHYDROGENDETECTION /RESONANCE"WINDOW"BEAMFigure 32: Technique for profiling hydrogen in thin films. 16It)2.5E~•J:NN2.0o....~0~ 1.5--~Q:~zLaJ.-../',"37-1V~429-91.0UZolUz 0.5\ ~-LaJC!)o0::~:r:0....
.-00.5DEPTH1.01.5(MICRONS)Figure 33: Hydrogen concentration versus depth measured by nuclear resonance. I7Film Evaluation Techniques211In order to provide a more convenient method for the evaluation of hydrogen concentration that could be useful for routine process control, thenuclear reaction procedure has been used to provide a standard for an infrared spectrometric technique. I7Here the infrared spectra of a thin film on a silicon wafer is obtained first.Then the absorbance at the Si-H and N-H bond regions is measured by estimating the area within each absorption band. As shown in Figure 34, theabsorbance seen by the infrared spectrometer correlates well with the hydrogen concentration.:r:--enI20+:r:Iz 16V....-4'-'<t 12wn::<lCl:2<t8CDa::.....4-.J<{~0~0021310 18 H/cm 2Figure 34: Cal ibration curve for infrared band area versus hydrogen concentration.
I7Another technique which can be used to measure hydrogen concentrationuses a 2.5-MeV 4He beam. I8 Although this is a more attainable energy range(comparable to accelerators used for RBS) than the nuclear method requires,it is still nowhere near as simple as obtaining an infrared spectra. However,it does offer the capability of depth profiling which the evaluation of infraredspectra does not.212Chemical Vapor Deposition for MicroelectronicsREFERENCES1. Pliskin, W.A. and Conrad, E.E., Nondestructive determination of thickness and refractive index of transparent films. IBM J. Res. Dev. 8:43(1964).2.
Spanier, R. F., Ell ipsometry-A century old new technique. IndustrialResearch (September 1975).3. Giang, R., Holmwood, R. and Rosenfeld, R., Determination of stressin films on single crystalline silicon substrates. Rev. Sci. Instr. 36:7(1965).4. Kern, W., Schnable, G.l. and Fisher, A.W., CVD glass films for passivation of silicon devices: Preparation, composition and stress properties. RCA Review 37:3 (1976).5. Sm its, F.M., Measurement of sheet resistivities with the four point probe.Bell Syst. Techn. J. 37 :711 (1958).6.
Zrudsky, D.R., Bush, H.D., and Fassett, J.R., Four point sheet resistivitytechniques. Rev. Sci. Instr. 37 :885 (1966).7. Jenkins, M.W., A new preferential etch for defects in silicon crystals. J.Electrochem. Soc. 124:757 (1977).8. linder, R., Bryson, C. and Bakale, D. Surface analysis in semiconductorfabrication. Microelectronics Manufacturing and Testing (February1985).9. Hilibrand, J. and Gold, R.D., Determination of the impurity distributionin junction diodes from capacitance-voltage measurements. RCA Review 21 :245 (1960).10.
Gordon, B.J., On-line capacitance-voltage doping profile measurementof low-dose ion implants. IEEE Trans. on Elec. Dev. ED-27:2268 (1980).11. Matsuo, S., and Kiuchi, M., low tenlperature deposition apparatus using an electron cyclotron resonance plasma. Proc. Symp. on VeryLarge-Scale Integration Science & Techn., Electrochemical Society,N.J. 7 :79 (1982).12. Miller, R.G.J. and Stace, B.C. (eds.), Laboratory Methods in InfraredSpectroscopy.
Heyden & Son, NY (1972).13. Adamson, A.W. Physical Chemistry of Surfaces, John Wiley & Sons, NY,Fourth Edition (1982).14. Ward, I.D. and Strathman, M., Analysis methods complement each otherin surface studies. Ind. Rev. Dev. (September 1983).15.
Nicolet, M-A and Chu, W. K., Backscattering spectrometry. AmericanLaboratory (March 1985).16. lanford, W.A., Tracetvetter, H.P., Ziegler, J.F. and Killer, J., New precision technique for measuring the concentration versus depth of hydrogen in solids. Appl. Phys. Lett. 28 :566 (1976).17. lanford, W.A. and Rand, M.J., The hydrogen content of plasma-depositedsilicon nitride. J.
Appl. Phys. 49:2473 (1978).18. Bordin, T.T., Pronko, J.G. and Joshi, A., Quantification of hydrogenin surfaces and thin films using a non-destructive forward scatteringtechnique. Thin Solid Films 119:429 (1984).IndexActive mass - 3Adhesion of thin films - 104AES (Auger electron spectroscopy) - 201Aluminum CVD - 114plasma enhanced - 148Ambipolar diffusion - 48Amorphous silicon - 119Amorphous thin films - 29Anicon bell jar LPCVD reactor - 170Autodoping - 85,139Automated wafer handling - 163Barrel reactor - 35Batch systems - 150Blanket deposition of tungsten 103Blocking capacitor - 50Borophosphosilicate glass (BPSG) 67,74plasma enhanced - 134Borosilicate glass (BSG) - 67Boundary conditions - 21Bou ndary layer - 15Breakdown electric fields - 46Cata lysis - 1Characterization of reactors - 131Chemical kinetics - 1, 13Chemical vapor deposition systems 2Cold-wall plasma CVD productionreacto r - 166Cold-wall reactors - 31Columnar crystal growth - 29Conformal coverage - 93, 98Continuous belt reactors - 36Continuous reactor systems - 150Cost per wafer - 150C-V measurements - 192DC bias in RF discharges - 52Debye length - 44Dichlorosilane - 71, 82Diffusion coefficients - 19Diffusion-controlled deposition 14,80,82,83Discharge frequency - 124, 125Dissociation reaction - 6Dry etching - 41,49EDX (energy dispersive X-rayanalysis) - 190Electrical resistivity of thin films 80Electromigration - 92Electron cyclotron resonance - 46,61213214Chemical Vapor Deposition for MicroelectronicsElectron temperature - 42Ellipsometer - 177Encroachment with selectiveW-CVD - 107Energy conservation - 19Epitaxial silicon, plasma enhanced 137Epitaxial silicon reactors - 158Epitaxial silicon thin films - 81Equilibrium constant - 4,6,20ESCA analysis of thin films - 197Etching - 10Evaporator - 100F ick I s La w - 15Film morphology - 3,189Film stoichiometry - 94, 97, 120Film stress - 68,72Final passivation films - 40, 66Finite difference methods - 23Flow modeling - 13Gas phase kinetics - 17Gas phase nucleatio n - 29, 68Gettering alkali ions - 66, 72Gibbs' Free Energy - 10Glow discharges - 40, 48, 119Gra in boundaries - 81Grain growth due to annealing96HCI etch - 83Heating by optical radiation - 137Hot tube LPCVD reactors - 156Hot-wall plasma CVD productionreactor - 168Hot-wa II reactor - 37Hydrogen concentrationfrom infrared absorption - 211profiling - 209Infrared spectroscopy - 193Ion bombardment - 53,61Larmor rad ius - 43Law of Mass Action - 3, 4Line-of-sight deposition techniques 93Low-pressure CVD - 68Mathematically stiff equations - 25Mean-free path - 43Metal silicide films - 92Microwave generator - 61Mole fraction - 5Molybdenum hexafluoride - 100,142Molybdenum pentachloride - 100,143Molybdenum silicide - 100plasma enha nced - 143Molybdenum thin films, plasmaenhanced - 142Momentum conservation - 19Morphology - 28Multilevel metallization - 93Native oxide - 138Nitrous oxide - 71Nucleation sites - 83Oxidation of refractory metalsilicides - 99Oxynitrides, plasma enhanced - 131Pancake epi silicon reactor - 161Partia I pressure - 4Pattern sh ift - 88Phosphorus-doped polysiliconfilms - 79Phosphorus as a getter - 129Phosphosilicate glass - 67Planarization - 72Plasma CVD production reactors 165Plasma oxide - 133Poisseulle flow - 18Polycides - 92, 95Polycrystalline thin films - 29, 77Polysilicon, plasma enhanced - 136Polysilicon thin films - 77Production CVD reactors - 150Radiant heating - 160RBS (Rutherford backscattering) 207IndexReaction rate coefficients - 20Rectangular electrodes - 60Reflow - 72Refractive index measurement 190Reinberg plasma-assisted CVDreactor - 57Resist ashing - 56Resonant nuclear reaction - 209Reynolds number - 15R F glow discharges - 41Secondary electron emission - 48Selective tungsten thin films - 106SEM/TEM - 189Sheath - 44,48,51Sheet resistance - 184Si-CI-H system - 7Silane - 82Silane pyrolysis - 1, 20Silicon nitride, LPCVD thermal 77plasma enhanced - 120Silicon tetrachloride - 82SIMS (Secondary Ion MassSpectrometry) - 202Single crystal thin films - 29Single wafer production CVDreactor - 172Slip lines - 84, 137Solar celts - 40Species mass conservation - 19Species production rate - 20Spectrophotometer for thicknessmeasurement - 177Spiking - 92Spreading resistance - 191Stacking faults - 84Sta nda rd free energy - 6Stoichiometric coefFicient - 4Stoichiometry - 134, 136215Sublimator - 100Surface-controlled deposition - 14Surface profi 10 meter - 176Tantalum disilicide - 100plasma enhanced - 144Tantalum pentachloride - 100Tetraethylorthosilicate (TEOS) - 74Thermal CVD reactors - 31Thickness measurements - 175Thin film adhesion - 144Thin film stress measurement - 182TIBAL (tri-isobutyl-aluminum) - 114Tilted susceptor tube reactor - 34Titanium disilicide - 103plasma enha nced - 146Titanium nitride thin films - 119Titanium tetrachloride - 103Transport phenomena - 1Trench filling - 76Trichlorosilane - 82Tungsten carbonyl - 105Tungsten hexachloride - 104Tungsten hexafluoride - 94, 103, 104Tungsten silicide - 94plasma enhanced - 139Tungsten thin films, plasma enhanced - 139Tunneling with selective W-CVD 110Visible defects - 188Wafer heating - 33WDX (Wavelength dispersive x-rayana lysis) - 190XR F (X-ray fluorescenceanalysis) - 190.
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