Introduction to the BSGS Specialty Gas Cabinet

BSGS Specialty Gas Cabinet

In high-end manufacturing facilities for semiconductors, TFT-LCDs, photovoltaics, lithium-ion batteries, and other industries, specialty gases such as silane (SiH₄), ammonia (NH₃), hydrogen (H₂), chlorine (Cl₂), tungsten hexafluoride (WF₆), and other specialty gases are delivered to the site in high-pressure cylinders and transported via piping into process chambers to facilitate critical processes such as film deposition, etching, and doping. Most of these gases are flammable, explosive, highly toxic, or highly corrosive. Between the cylinders and the process equipment, there must be a central hub that integrates storage, pressure regulation, switching, monitoring, interlocking, and exhaust gas treatment—the BSGS (Bulk Specialty Gas System).

FUNCTION INTRODUCTION

Overview of the BSGS Specialty Gas Cabinet

Wofly Technology BSGS Specialty Gas Cabinet Showcase

01 Overall Structure

The BSGS Specialty Gas Cabinet is a vertical steel cabinet that integrates six units: a sealed cylinder storage area, a stainless steel gas distribution manifold and valve assembly, a pressure regulation unit, a PLC-based human-machine interface control unit, a gas detection and safety interlock unit, and an exhaust gas treatment unit. The gas lines utilize 316L EP/BA stainless steel tubing and high-purity diaphragm valves to meet SEMI high-purity gas requirements. The cabinet top is equipped with red, yellow, and green alarm lights, and the cabinet door features a viewing window and a mechanical lock. Cylinders are secured to dedicated brackets, and cylinder replacement may only be performed after the isolation and purging process has been successfully completed.

                       Inside the BSGS Specialty Gas Cabinet

02 Automatic Dual-Tank Switching

The BSGS is configured with two mirrored gas lines: one for the primary cylinder and one for the standby cylinder. The PLC monitors the outlet pressure of the primary cylinder in real time. When the pressure drops to the lower process limit setpoint, it automatically closes the primary cylinder valve assembly and opens the standby cylinder valve assembly, enabling a switchover without interrupting operation while triggering an alarm to indicate the need for a cylinder change. This prevents process gas interruption caused by a single cylinder running out. During the switchover process, the system automatically performs pipeline purging and pressure retention (leak check) to prevent gas cross-contamination between the two lines and the backflow of air into the high-purity piping.

03 Multi-Stage Pressure Regulation and Stable Pressure Output

Cylinder pressures range from several megapascals to over ten megapascals (the vapor pressure of NH3 is approximately 0.9 MPa, while high-pressure SiH4 cylinders can reach over ten MPa), whereas the process end requires only 0.2 to 0.5 MPa. The BSGS specialty gas cabinet stabilizes outlet pressure through a two-stage pressure reduction process—primary pressure reduction (on the high-pressure side) and secondary pressure reduction (fine adjustment on the low-pressure side)—in conjunction with pressure gauges, pressure transmitters, and orifice plates. Pneumatic diaphragm valves and check valves are installed on the manifold, with the valves featuring 316L VCR face-seal connections.

                      Special Gas Cabinet Panel Piping Display

04 Leak Detection and Safety Interlock Alarms

Detectors are installed inside the cabinet according to the properties of the gases: catalytic combustion or infrared detectors are used for combustible gases (H₂, SiH₄, NH₃); electrochemical detectors are used for highly toxic and corrosive gases (Cl₂, PH₃, AsH₃), and are positioned at the bottom or top of the cabinet based on the density of the gases. When the concentration reaches the low-alarm threshold, an audible and visual alarm is triggered and a signal is transmitted; when it reaches the high-alarm threshold, the cylinder end valve is automatically closed, emergency ventilation is activated, non-explosion-proof electrical circuits are shut off, and an interlock signal is sent to the plant’s GDS.

                                   Smoke Detector Showcase

05 Explosion-Proof Positive Pressure and Electrical Safety

For applications involving flammable and explosive gases such as SiH₄, H₂, and NH₃, the BSGS specialty gas cabinet is equipped with a PXK-type explosion-proof positive-pressure control cabinet. Clean compressed air or nitrogen (N₂) is supplied to the cabinet to maintain a slight positive pressure, preventing explosive mixtures from entering from the outside; the HMI touchscreen, emergency stop button, and audible and visual alarms are all located within the positive-pressure chamber, and electrical components are selected in accordance with the Ex explosion-proof rating.

          Exhibition of Explosion-Proof Positive-Pressure Cabinets

06 Exhaust Gas Scrubbing and Compliance with Emissions Standards

The BSGS specialty gas cabinet releases a small amount of process exhaust gas during purging, replacement, and cylinder change operations. After being adsorbed and neutralized, the exhaust gas is discharged outdoors through a dedicated exhaust duct in compliance with emission standards, thereby preventing the accumulation of toxic and flammable gases in the workshop.

FUNCTION INTRODUCTION

The Role of BSGS Specialty Gas Cabinets in Bulk Specialty Gas Supply Systems

               Wofly Technology Workshop Equipment Showcase

01 System Link Troubleshooting

The complete specialty gas supply chain consists of four sections: ① The gas source area (cylinder room/specialty gas station) stores cylinder racks; ② The BSGS specialty gas cabinet handles switching, pressure regulation, monitoring, interlocking, and exhaust gas treatment; ③ Distribution piping and valve boxes (VMB/VMP) deliver high-purity gases to various process zones; ④ At the process equipment end (Tool), gases are routed through the end-point gas control panel (GCP) to etching, deposition, and ion implantation chambers. The BSGS specialty gas cabinet is located in Segment ② and serves as the physical and safety boundary between the high-pressure cylinder storage area and the cleanroom.

  A Selection of BSGS Specialty Gas Systems (For Reference Only)

02 Security Isolation

The core system value of the BSGS specialty gas cabinet is isolation. High-pressure, highly toxic, and flammable cylinders are always enclosed within a cabinet equipped with a viewing window; during normal operation, personnel do not come into contact with the high-pressure gas lines. In the event of a leak, emergency ventilation is immediately activated, and the high-alarm interlock shuts off the valve. The leaked gas is contained within the cabinet, scrubbed, and then discharged, preventing it from spreading into the cleanroom, hallways, or personnel operating areas, thereby ensuring that gas concentrations in the main workshop area remain below the Occupational Exposure Limit (OEL) at all times.

03 Continuous Gas Supply

Semiconductor production lines operate 24 hours a day, and a single interruption in gas supply to a single piece of equipment can result in the entire batch of wafers being scrapped. The BSGS specialty gas cabinet’s dual-cylinder automatic switching system transforms cylinder replacement from an offline operation into an online process: when the primary cylinder is depleted, the backup cylinder automatically comes online, allowing operations and maintenance personnel to replace the empty cylinder without interrupting the process. After the replacement, the system automatically performs pressure maintenance and purging before switching back to the primary supply path, directly ensuring the production line’s overall utilization rate.

                                Bulk Gas Pipeline Exhibition

04 Secondary Stabilization of Pressure and Air Supply Quality

BSGS specialty gas cabinets typically supply process equipment via BA/EP pipelines spanning distances ranging from tens to hundreds of meters. Along the route, pressure fluctuations occur due to frictional resistance, gas distribution at the VMB, and simultaneous gas consumption by multiple pieces of equipment. The BSGS specialty gas cabinet precisely adjusts the outlet pressure to the process requirement at the secondary pressure regulation stage. Working in conjunction with a downstream pressure transmitter for closed-loop compensation, it maintains a stable inlet pressure at the VMB, thereby preventing multiple devices from competing for gas and avoiding flow rate fluctuations that could affect film uniformity and etch selectivity.

                              Presentation on a Bulk Gas Project

05 Data Upload Integrated with GDS/GMS Systems

The modern BSGS serves as a field node for the plant-wide gas detection system (GDS) and the gas monitoring system (GMS). Via hardwiring or Modbus/Profinet communication, the BSGS transmits real-time data—including cylinder status (in use/standby/empty), inlet and outlet pressure, cumulative flow, detector concentration, cabinet door status, and alarm codes—to the central monitoring room. This enables operations and maintenance personnel to remotely determine which cabinets require cylinder replacement and which sections of piping have minor leaks, thereby facilitating predictive maintenance.

06 Emission-Side Closed-Loop Compliance

The BSGS specialty gas cabinet pre-treats exhaust gases from purging, replacement, and leak detection within the cabinet before routing them to the plant’s scrubber for centralized discharge. Together with the plant’s exhaust ventilation system, this forms a complete, compliant closed-loop system spanning the gas source, point of use, and discharge. This closed-loop system is a mandatory requirement for new and retrofitted semiconductor facilities under standards such as SEMI S2 (Semiconductor Equipment Safety Assessment Guide), GB 50177 (Design Code for Hydrogen Stations), and GB/T 50493 (Design Standard for Flammable/Toxic Gas Detection and Alarm Systems).

                             Presentation on a Bulk Gas Project