We herein report a rare case of an atherosclerotic superficial temporal artery (STA) aneurysm. The patient was a 34-year-old Japanese man. He noticed a throbbing swelling just in front of his right ear, which had slowly increased in size. There was no history of trauma. Digital subtraction angiography and ultrasound revealed an aneurysm measuring 2cm in diameter fed by STA. A ligation and resection were performed under local anesthesia. The recovery period was uneventful. A microscopic examination revealed a moderate degree of atherosclerosis. We found 48 cases of STA aneurysm in the Japanese literature from 1969 to 1997, including our case. Thirty-six of these cases (75.0%) were considered to be traumatic in origin. Three cases (6.2%) occurred after a craniotomy. To date, only nine reported cases (18.8%) have been attributed to a spontaneous or congenital etiology.
A new analysis method for deflection of the mask membrane during the wafer stepping motion in x-ray steppers has been developed. The deflection is caused by the wedge action of the gas film between the mask and the wafer if the mask tilts slightly relative to the plane on which the wafer is traveling. The deflection is not only detrimental to the throughput of x-ray steppers, it may also damage the mask membrane. Lees’ difference approximation method is applied to Reynolds’ equation for the gas film and the equation of motion for the membrane. The results calculated show good agreement with the experimental results (Ref. 1) obtained by Canon Inc. (1) The larger the tilt angle of the mask and the narrower the mask-to-wafer gap, the larger the deflection of the mask membrane. (2) In order to maintain the deflection of the membrane within 1 μm in the calculated mask, the tilt angle of the mask must be within 20 μrad under conditions of a 15 μm mask-to-wafer gap, a 30 mm stepping distance, and a wafer velocity of 100 mm/s. If the stepping distance becomes longer, the tilt angle must be more strictly controlled.
This article presents a new analysis method and experimental results for the deflection and vibration of x-ray masks, which are caused by the squeeze effect of the gas film between a mask and a wafer in x-ray steppers. The deflection and vibration occur when a mask-to-wafer gap setting is executed or if the wafer vibrates in the mask direction during stepping motion with a narrow gap. They are not only detrimental to the throughput, but may also damage the mask membrane. Lees’ difference approximation method is applied to a compressible Reynolds’ equation and the equation of motion for the mask membrane. The main results of calculations and experiments, which showed good agreement with each other, are outlined below. (1) When the wafer approaches the mask at a constant velocity, the mask deflection increases in proportion to the velocity, and the mask deflection is larger for a smaller mask tensile stress. (2) When the wafer vibrates in the mask direction, the amplitude of the mask vibration increases with increasing the wafer frequency, and reaches a maximum value at a frequency that depends on the gap size. The maximum amplitude of a tested mask becomes 4 times as large as the wafer amplitude. (3) For a high frequency and narrow gap, the mask vibrates while deflecting convexly in the direction opposite to that of the wafer.
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