Chemically assisted ion beam etching (CAIBE) is widely practiced in the semiconductor industry. In the electron microscopy field, the CAIBE technique offers a new method for preparing specimens that are difficult to make by conventional inert gas milling techniques, e.g. indium containing type III-V compound semiconductors. CAIBE employs a collimated, molecular beam of a reactive species, e.g. iodine in combination with a conventional inert gas fast atom beam for thinning TEM specimens. CAIBE should not be confused with reactive ion beam etching (RIBE) which takes a chemically active species (e.g. iodine) and converts it into a beam of fast ions directed at the sample. CAIBE has three major advantages over (RIBE): i) corrosion of the ion gun components does not occur, ii) much smaller quantities of reactive gas are required and hence pump maintenance and pollution problems are minimized, iii) a wider range of chemicals may be used. Superior results are obtained if CAIBE is done on only one side of the specimen at a time. This is achieved using a new type of specimen holder post which enables very low angle milling and minimizes specimen contamination by sputtering from the holder. This new technique is described and results from iodine CAIBE milling, iodine RIBE milling and argon ion milling are compared for InP, InSb and GaAs as well as metals like tungsten. Also, the beneficial effects of very low angle (∼1°) argon ion milling in preparing specimens of silicide containing Si based IC wafers is reported.

Bend and splay elastic constants and the rotational viscosity of nematic decylammonium chloride and ammonium chloride water mixturesThe adiabatic elastic constants of single-crystal ammonium chloride have been measured as functions of sound frequency from 5 to 55 Me/sec, and as functions of temperature from ~150° to 300 0 K by an ultrasonic pulse technique. The values of the constants at 300 0 K are cn=3. 70, C44=0.86,)/2=1.41 in units of 1011 dyn cm-2 • Special emphasis was given to the region around 243°K, the critical temperature for the order-disorder transition. The results are discussed in terms of the phenomenological thermodynamic theory of Pippard.

The attenuation coefficient α of longitudinal ultrasonic waves propagating along the [100] direction in single-crystal ammonium chloride has been measured as a function of frequency from 5 to 55 Mc/sec and as a function of temperature from 200° to 270°K. A sharp maximum is observed in α at the order—disorder critical temperature. The results are analyzed in terms of a relaxation model with a highly temperature-dependent relaxation time.

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The construction and performance of an updated gas source precision ion milling system are described. The system is based on an existing focused ion beam machine which is able to image and mill selected areas of specimens that are too thick for TEM studies. The specimen image is formed using either secondary electrons or secondary ions, captured by a dual detector. The work chamber consists of three major components: the ion gun, the ion column and the specimen chamber. The ion gun is an electron impact ionization type with an optimized source size and allows the use of variety of gases. The updated system employs an objective lens with shorter focal length to enhance the resolution. The specimen chamber with an improved specimen eucentric stage, accepts side entry TEM specimen holders. This enables the specimen to move between the TEM and the instrument for further precision thinning as required without removal of the specimen from the holder and consequent risk of damage. The upgraded system resolves features <1μm in thickness. Its point milling rate for Ni is 1.4μm/min. The ability of the instrument for imaging and localized milling is demonstrated by a number of TEM images of semiconductors, metals, ceramics and composites.