As microchips become smaller, the threat of damage to the device elements of Si semiconductors by charging during plasma etching will become significant. It will be of first importance to establish a plasma-etching technique that does not involve charging, i.e., “charging-free plasma processing.” Here, we utilize the effect of negative charge acceleration under a double layer in order to neutralize the charge inside a microstructure exposed to plasma etching. We have constructed a dual measurement system consisting of an emission in an interface and a contact hole charging on a SiO2 wafer during etching in two-frequency capacitively coupled plasma (2f-CCP) in CF4/Ar and pure Ar. A reduction in charging voltage is measured in the pulsed operation both of the plasma power source and of the wafer bias in the 2f-CCP in electronegative gases, CF4/Ar.
Background:Gastrointestinal stromal tumors (GISTs) are potentially malignant and are indicated for resection. The standard treatment for resectable GISTs is surgery, although endoscopic resection has been reported outside Japan. This study retrospectively analyzed the results of endoscopic resection of GISTs in Japan.Method:We identified patients with GISTs treated only by endoscopic resection in our institute between January 2016 and December 2018, and analyzed their clinical and pathological characteristics.Results:During the study period, 8 GISTs were resected only by endoscopy: 7 were located in the upper third of the stomach and 1 in the middle. All were intraluminal growth type. Median (range) tumor diameter was 20 (10-35) mm. All tumors were resected en bloc with a median (range) operation time of 67.5 (50-166) min. Complete perforation occurred in 5 cases, but the serosa remained in 2 and the outer layer of the muscularis propria remained in 1. The defect was endoscopically closed with clip-and-endoloop purse-string suturing (n=3), simple endoclipping (n=2), or over-the-scope clipping (n=2), and 1 did not require closure because the outer longitudinal muscle was preserved. Oral feeding was commenced on postoperative day (POD) 3 (median; range 2-4), and the patient was discharged on POD 6 (median; range 4-11). No serious adverse event developed after the procedures.Conclusion:Endoscopic resection for selected cases of small intraluminal GISTs is feasible, making it a viable alternative treatment option to laparoscopic surgery.
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