Page 335 - Sami Franssila Introduction to Microfabrication

314 Introduction to Microfabrication

Ex situ measurements include physical, chemical kinetic energy of sputtered particles, ion and electron
and structural measurements. Transmission electron bombardment and ion neutralization each contribute
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microscopy (TEM), secondary ion mass spectrometry ca. 2–5 mW/cm ). How much do wafers heat up
(SIMS) and Rutherford backscattering spectrometry during sputtering?
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(RBS) are also slow methods, and can be bought as 3. If the oxidation furnace is ramped up at 10 C/min
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services from outside contractors. from a stand-by temperature of 800 C, and ramped
Surface analytical methods are problematic because down from the process temperature at 5 C/min, what
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sample transfer from the process chamber to the ana- is the process time for (a) 15 nm dry oxide at 900 C;
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lytical chamber takes some time and gases and vapours (b) for 300 nm wet oxide at 1000 C?
adsorb on the sample surface and disguise the original 4. Calculate the minimum deposition rate that can be
surface signal. In-line tools do exist for integrated sur- monitored by a QCMB sensor if the wafers are heated
face analysis, for example, RIE etch chamber connected by the deposition process at 3 K/min.
to an X-ray photoelectron spectrometer (XPS), but such
systems are for basic research only.
REFERENCES AND RELATED READINGS
Loewenstein, L. et al: First-wafer effect in remote plasma
30.7 EXERCISES
processing: the stripping of photoresist, silicon nitride and
polysilicon, J. Vac. Sci. Technol., B12 (1994), 2810.
1. By how much will the wafer temperature rise during
Moslehi, M.M. et al: Single-wafer integrated semiconductor
implantation of arsenic ions of energy 100 keV device processing, IEEE TED, 39 (1992), 4–32.
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and dose 10 cm −2 with a current of 1 mA on a
Rubloff, G.W. & Boronaro, D.T.: Integrated processing for
200 mm wafer? Make simplifying assumptions as microelectronics science and technology, IBM J. Res. Dev.,
needed. 36 (1992), 233.
2. In sputtering, ca. 10 to 20 mW/cm 2 of energy Schuegraf, K.: Single-wafer process technology: enabling rapid
is supplied to the surface (heat of condensation, SiGe BiCMOS development, IEEE TSM, 16 (2003), 121.