Page 357 - Sami Franssila Introduction to Microfabrication

336 Introduction to Microfabrication

2. Polysilicon LPCVD activation energy E a is 1.7 eV. Table 7.2, assuming a single-wafer reactor volume
What happens to the deposition rate if, instead of of 5 liters?
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standard 630 C deposition, 570 C is used? 8. What is the total gas flow in the process shown in
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3. If the gas-phase transfer coefficient h is 3 cm/s, Figure 33.7?
7
and the surface reaction coefficient k = 5 × 10 exp
(−1.7 eV/kT) (in cm/s), at what temperature does
the reaction turn from transport-controlled to surface- REFERENCES AND RELATED READINGS
controlled? Cote, D.R. et al: Low-temperature chemical vapour deposition
4. What is the cost of a 150 mm diameter epiwafer if processes and dielectrics for microelectronic circuit manu-
the single-wafer epireactor described in Figure 33.7 facturing at IBM, IBM J. Res. Dev., 39 (1995), 437.
costs $2 million, running costs are $800 000/year (gas Crippa, D., D.R. Rode & M. Masi: Silicon epitaxy, in Semi-
and graphite costs are dominating) and starting wafer conductors and Semimetals, Vol. 72, Academic Press,
cost is $20? 2001.
5. What is the utilization of silane in oxide CVD if the Everstyen, F. C.: Chemical-reaction engineering in the
flow is 15 sccm silane with overabundance of N 2 O in semiconductor industry, Philips Tech. Rep., 29 (1967),
a single-wafer reactor, with 150 mm wafer size and 45.
deposition rate of 50 nm/min. Leskel¨ a, M. & M. Ritala: Atomic layer deposition (ALD): from
6. Nitride LPCVD is done nominally at 750 . What precursors to thin film structures, Thin Solid Films, 409
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(2002), 138.
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thickness difference does 6 C temperature difference
Ohring, M.: The Materials Science of Thin Films, Academic
indicate if E a = 1.9 eV? Press, 1992.
7. What is the thinnest layer that could reason- Vossen, J. & W. Kern: Thin Film Processes, II, Academic
ably be deposited using PECVD parameters of Press, 1991.