Page 111 - Sami Franssila Introduction to Microfabrication

90 Introduction to Microfabrication

7.10 EXERCISES Cote, D.R. et al: Low-temperature CVD processes and
dielectrics, IBM J. Res. Dev., 39 (1995), 437.
1. The speed of sound in ZnO is 5700 m/s. What is the Fang, W. & C.-Y. Lo: On the thermal expansion coefficients
intended operating frequency for the TFBAR shown of thin films, Sensors Actuators, 84 (2000), 310.
in Figure 7.9? Guckel, H. et al: Fine-grained polysilicon films with build-in
2. Calculate the wafer bow that a thin film of 100 nm tensile strain, IEEE TED, 35 (1988), 800.
thickness and 100 MPa stress induces on a 675 µm- Hansen, M. & K. Anderko: Constitution of Binary Alloys, 2 nd
ed., McGraw-Hill, 1958.
thick, 150 mm diameter silicon wafer. Also calculate
the same for a 100 nm-thick film of 500 MPa stress Hilleringmann, U. & K. Goser: Optoelectronic system inte-
gration on silicon: waveguides, photodetectors, and VLSI
on a 380 µm-thick, 100 mm-diameter wafer? CMOS circuits on one chip, IEEE TED, 42 (1995), 841.
3. A periodic lattice of W and C is used as a λ/4 X-ray Kang, U. et al: Pt/Ti thin film adhesion on SiN x /Si substrates,
mirror. What are the layer thicknesses that should be Jpn. J. Appl. Phys., 38 (1999), 4147.
used for 100 eV X-rays? Laurila, T. et al: Failure mechanism of Ta diffusion barrier
4. Oxygen is soluble into titanium up to 34 atomic%. between Cu and Si, J. Appl. Phys., 88 (2000), 3377.
What will be the thickness of a silicon dioxide film Murarka, S.P.: Metallization, Theory and Practice for VLSI and
that can be dissolved by a 50 nm-thick titanium film? ULSI, Butterworth-Heinemann, 1993.
3
Titanium density is 4.5 g/cm , silicon dioxide density Ohring, M.: The Materials Science of Thin Films, Academic
3
is 2.3 g/cm . Press, 1992.
5. What is the step coverage in Figures 7.15(b), 7.16(c), Raaijmakers, I.J. et al: Microstructure and barrier properties
of reactively sputtered Ti-W nitride, J. Electron. Mater., 19
and 7.19(a)? (1990), 1221.
6. Draw the deposited film profile over a given topog- Ritala, M. et al: Perfectly conformal TiN and Al 2 O 3 film
raphy for the six different cases listed below: deposited by atomic layer deposition, Chem. Vapor Deposit.,
(a) Sputtered aluminium, 300 nm thick 5 (1999), 7.
(b) CVD TEOS 0.3 µm thick Rossnagel, S.M. et al: Thin, high atomic weight refractory film
(c) Electroplating 0.5 µm copper deposition for diffusion barrier, adhesion layer and seed layer
(d) PECVD oxide 0.2 µm thick applications, J. Vac. Sci. Technol., B 14 (1996), 1819.
(e) Evaporated aluminium, 100 nm thick Smith, D.L.: Thin-film Deposition, McGraw-Hill, 1995.
Thornton, J.A.: The microstructure of sputter-deposited coat-
(f) SOG application, 300 nm thick.
ings, J. Vac. Sci. Technol., A4(6) (1986), 3059.
Vallat-Sauvain, E. et al: Evolution of microstructure in micro-
0.5 µm crystalline silicon prepared by very high frequency glow-
discharge using hydrogen dilution, J. Appl. Phys., 87 (2000),
3137.
0.5 µm Vehkam¨ aki, M. et al: Atomic layer deposition of SrTiO 3 ,
Chem. Vapor Deposit., 7 (2001), 75.
7. TiAl 3 is formed in the reaction between aluminium Wang, S.-Q. & J. Schlueter: Film property comparison of
and titanium films. What will happen to the volume Ti/TiN deposited by collimated and uncollimated physical
3 3
of the metal line? Al: 2.7 g/cm ; Ti 4.5 g/cm ; TiAl 3 vapor deposition techniques, J. Vac. Sci. Technol., B14(3)
3
3.35 g/cm . (1996), 1837.
Wang, S.-Q. et al: Step coverage comparison of Ti/TiN
deposited by collimated and uncollimated physical vapor
REFERENCES AND RELATED READINGS
deposition techniques, J. Vac. Sci. Technol., B14(3) (1996),
Baumann, H.F. & G.H. Gilmer: 3D modelling of sputter 1846.
and reflow processes for interconnect metals, IEDM 1995, Wang, Y.Y. et al: Synthesis and characterization of highly
p. 89. textured polycrystalline AlN/TiN superlattice coatings, J.
Chou, B.C.S. et al: Fabrication of low-stress dielectric Vac. Sci. Technol., A16 (1998), 3341.
thin-film for microsensor applications, IEEE EDL, 18 Xu, Y.P. et al: A study of sputter deposited silicon films, J.
(1997), 599. Electron. Mater., 21 (1992), 373.