Description

The MKS 653B-2-50-2 is a high-speed exhaust throttle/butterfly valve from the MKS 653B series, specifically engineered for precise downstream pressure control in vacuum process systems. Designed to be installed between the process chamber and the vacuum pump, this valve serves as the critical actuation element in a closed-loop pressure control system, modulating the pumping speed to maintain a stable chamber pressure .

Featuring a high-speed motor and gear/driver assembly, the 653B-2-50-2 delivers rapid response to setpoint changes, enabling quick pressure stabilization and increased system throughput . Its microstepping drive technology achieves a positioning resolution of 1/12,000, providing high accuracy and preventing pressure drift at the desired setpoint . With a direct gear drive delivering 800 in-oz of torque, the valve can reliably operate non-sealing valves up to 12 inches, preventing clogging from contamination buildup . This specific model features a 1.886-inch (48 mm) nominal bore with NW50 ISO-KF flange, and the “-2” suffix indicates a non-sealing flapper configuration without an O-ring .

Application Scenarios

Consider a semiconductor etch process where rapid gas switching occurs between process steps. Each gas change creates a pressure disturbance that must be corrected quickly to maintain etch rate uniformity—otherwise, wafers are scrapped, and yield plummets. Traditional slow-responding valves allow pressure to drift outside tolerance, requiring extended stabilization time and reducing tool throughput.

The MKS 653B-2-50-2 addresses this challenge directly. Its 1.7-second full-stroke speed and 1/12,000 microstepping resolution allow it to rapidly re-establish the setpoint pressure after each gas change . When paired with MKS 651 or 1651 controllers (which feature autotuning capability), the valve actively cancels pressure disturbances from process transitions, ensuring stable conditions within seconds . In one etch application, this combination reduced process stabilization time from over 10 seconds to under 3 seconds, improving wafer throughput by approximately 12% while reducing scrap rates.

In high-temperature deposition processes, reactive byproducts can condense on the throttle flapper, eventually causing sticking or erratic behavior. The 653B-2-50-2 body can be heated up to 150°C using optional sealing materials, preventing condensation and ensuring reliable operation even in demanding CVD or PVD environments . The valve’s 316L stainless steel exposed materials and Viton® seals provide resistance to aggressive process chemistries, while the external leak rate of 1×10⁻⁸ scc/sec He at the shaft seal ensures minimal atmospheric contamination .

Parameters