The sidewall residue seen after Al etching and via-hole etching on an Al pattern was investigated. X-ray photo-electron spectroscopy (XPS) after O2 plasma ashing revealed that this sidewall residue contained a large number of Al atoms sputtered from the Al film surface. A downstream ashing technique employing F atoms and water vapor has already been developed to remove the persistent resist after plasma processing or ion implantation, but even this downstream ashing could not remove the sidewall residue containing Al. It has been found that the downstream process changed Al and Al oxide in the residue to Al fluoride, a water-soluble compound. Thus, rinsing with DI water successfully removed the sidewall residue after downstream ashing.

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The international comparison of frequency standards made with the luminous quartz resonator shows the different laboratories,-Physikalischtechnische Reichsanstalt, National Physical Laboratory, Bureau of Standards, and Electrotechnical Laboratory,-to be in agreement to one part in 105 when used to calibrate the resonator at its flexuralfundamental of about 10 kc, due allowance being madefor the temperature coefficient of the resonator in this mode, namely, about 1 part in 105 and negative. The observed agreement seems limited by the luminous glow resonator used rather than by any difference between the laboratory standards compared.AST year the writer had an opportunity of making an international comparison of frequency by means of a luminous quartz resonator. The quartz resonator (No. 108/77.9) was made by the Loewe Radio Company of Germany. The quartz bar, as illustrated in Fig. 1, is enclosed in a partially evacuated bulb, and is a bar of Curie cut (X-cut).The thickness of the quartz bar along the X axis (electrical axis) is 0.15 cm, its length along the Y axis is 8 cm, and its breadth along the Z axis (optical axis) is 0.4 cm. The bar is held in position by silk threads at a distance of 1 cm from each end and has four electrodes, the lengths of which are approximately 2.4 cm each. Terminals (1) and (4) of the resonator are connected to one of the terminals of the coupling coil provided, and terminals (2) and (3) to the other terminal of the coil. The coupling coil has an inductance of 158 mh and a resistance of 88 ohms.The frequency fb of flexural vibration of the bar in the direction of the Z axis is theoretically k2xiV Z fb = -' 4rV/3 y2 in cycles per second where k is (m+j)-r; y and z are the lengths of the bar in cm along the Y and Z axes respectively; v denotes the propagation velocity of elastic waves in quartz in cm per sec. Putting v = 5.4