Stress present in thermal SiO2 at temperatures during growth in wet O2 has been measured as a function of growth temperature. During growth at 950 °C and below, compressive stress on the order of 7×109 dyn/cm2 is generated in the SiO2. During growth at 975 and 1000 °C, the SiO2 grows in a stress-free state. The results, which are consistent with a viscous flow point somewhere between 950 and 975 °C, are of value in avoiding mechanical failure effects in integrated-circuit processing.

Wafer curvature measurements from 25 to 1075 °C are used to demonstrate viscous flow of thermally grown SiO2 at temperatures as low as 960 °C. Both O2- and steam-grown oxides are examined and found to have viscosities similar to synthetic fused silica. It is recommended that high-temperature Si device processing involving SiO2 be held to below 960 or even 925 °C, after oxide growth to avoid viscous flow and the accompanying structural damage in the oxide. This recommendation holds particularly for device technologies where resistance to ionizing radiation is important. The measurements also demonstrate that gross structural damage resides in the Si beneath steam-grown oxide.

The term ;bulk resonator' is used to include a variety of vibrational modes. The survey is broken down by type of resonant mode, namely thickness shear, single-ended flexural, double-ended flexural, and torsional. Where appropriate, the discussion of each type of resonant mode includes items related to the frequency-control applications of the particular mode to emphasize the cross fertilization occurring between frequency control and sensor work.

It is shown theoretically and experimentally that stresses in a thin film on a quartz resonator surface can set up sufficient static mechanical bias in the resonator to cause measurable shifts in the resonant frequency through finite strain effects. In particular, it is found that if a 5-MHz AT-cut fundamental mode and a 6.19-MHz BT-cut fundamental mode are subjected to the same combination of thin-film stress and mass/cm2 changes on their surfaces, the sum of the observed frequency shifts is proportional to the mass/cm2 change alone, and the difference of the frequency shifts is proportional to the integral through the film thickness of the change in the thin-film stress alone. This ``double-resonator'' technique is demonstrated with implantation studies of 220-keV 84Kr implants into Si films deposited on the flat electrodes of planoconvex 5-MHz AT-cut and 6.19-MHz BT-cut resonators. The double-resonator technique stress results were verified quantitatively by implanting ions into a Si film on one surface of a quartz cantilever beam and monitoring the movement of the free end of the cantilever beam by the changes in capacitance between the free end and a fixed electrode. The sensitivity of the double-resonator technique is 125 dyn/cm and 6 × 1014 amu/cm2 for a 0.1-Hz frequency shift. The technique is suited best to thin-film stress studies with small mass changes.

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