Equipment used in the semiconductor manufacturing process generally have a flow rate control system for each nozzle to regulate the flow rate of chemical solution fed to the wafer. In existing flow rate control systems, flow rate overshoots occur because of excess pressure and the control rates of the overshoots are less because additional operation time is required for the electric valves. In this study, to address the shortcomings of existing flow rate control systems, we proposed a method to improve the speed of flow rate control by introducing a constant pressure valve. The constant pressure valve controls the flow path via gas pressure, thereby facilitating prompt control and efficiently improving the flow rate overshoot caused by the pressure overshoot. To improve the control speed and control stability of the constant pressure valve, a three-step automatic control speed application function was developed, and the measured valve, control amount mapping function, and pre-open function were defined to reduce the initial control speed. The experimental results showed a measurement precision within 1% of the target flow rate and stable control performance as well as control speed reduction from 3 seconds in existing systems to 2 seconds or less for the proposed system.

Bedridden patients develop pressure sores, as a result of poor blood circulation and excessive humidity. Conventional bedsore mattresses are designed to vary interface pressure zones, between the body and mattress for improved blood flow. Another approach is to control interface humidity, by forced air circulation. An ideal solution may be interface humidity control, in addition to pressure zone control. In this paper, a thin and flexible structure is suggested for forced air ventilation, that can be placed atop pressure zone controlled mattresses. With fabric covers, drying performances are evaluated for a range of air flow rates.