DRIE: Bosch & Cryo ICP-RIE for Silicon

DRIE Instrument Type Etching Techniques Bosch & Cryogenic Etch of Silicon Staff Manager Nathan S. Lee Staff Email nathslee@caltech.edu Staff Phone 626-395-1319 Reserve time on FBS Request training via FBS User Dashboard Lab Location B235 Steele Lab Phone 626-395-1532 Manufacturer Oxford Instruments Model Plasmalab System 100

Description

The MEMS / Bosch / Cryo inductively-coupled plasma reactive-ion etch (ICP-RIE) is an Oxford Instruments Plasma Technology Plasmalab System 100 ICP-RIE 380 system that is optimized for silicon etching. This system is configured for deep reactive-ion etching (DRIE) via the Bosch process, allowing silicon etching with C₄F₈ and SF₆ gases. Close-coupled gas pods are included in this system for fast Bosch switching; this allows the etching of bulk silicon for MEMS applications with etch rates of approximately 10-25 μm/min. The silicon ICP-RIE has a variable temperature stage (-150 to 400 °C) to permit cryogenic etching of silicon with SF₆ and O₂ if needed. This system supports wafer sizes up to 6 inches and provides accurate deep etching capabilities for silicon only.

Applications

• Deep silicon etch using Bosch process
• Cryogenic etch of silicon
• pseudo-Bosch etch of silicon

Allowed material in DRIE

• Si, Si_xN_y, SiO₂, Ge
• PMMA/ZEP/SPR/AZ/maN resists, SiO_x/Al₂O₃ hard masks
• Buried/backside metal ok if never exposed (not an etch stop)

DRIE Gas List

• SF₆
• C₄F₈
• O₂
• Ar
• N₂

Resources

SOPs & Troubleshooting

• General Use SOP
• Etcher toxic gas handling SOP
• Power Up Oxford ICP-RIE SOP
• Gas Status Board SOP

Process Documents

• Process Standards
• Silicon Waveguide Etch
• Bosch Si Etch
• High-Rate Bosch Si Etch
• Cryo-Si Etch
• Isotropic Si Etch
• Etch chamber cleaning recipes

Manufacturer Manuals

• Oxford Plasmalab System 100 DRIE Manual
• Edwards QDP 80 dry vacuum pump Manual

Specifications

Manufacturer Specifications

• Manufacturer System Configuration

System Features

• Universal base console that houses the electronic sub systems, control units, pneumatics, and turbomolecular pump
• PC 2000 Operating system
• ICP process chamber with 200 mm pumping port, view port and end-point-detection ports for optical emission spectrometer and laser interferometer
• Variable height 240 mm Cryo RIE electrode
• Parameter ramping software
• 100 mTorr, temperature-stabilized capacitance manometer for process control with an active penning gauge for base pressure measurement
• 200 mm pumping port is fitted with a 200 mm variable gate valve for chamber isolation and process pressure control
• Close-coupled gas pod to ICP for two digital non-toxic mass-flow-controlled gas lines (SF₆, and C₄F₈)
• Six line gas pod with three non-toxic digital mass-flow-controlled gas lines
• Alcatel 1300 l/s MAGLEV turbo pump
• Single-wafer automatic insertion load lock with soft pump option
• Single user license for Anisotropic Silicon Etch Process (Bosch)

System Specifications

• Chamber wall heating: 80 °C
• Cryo table range: -150 to 400 °C
• ICP 380 mm remote high-density plasma source with 8 kW RF generator and automatic matching unit close-coupled to the source
• Substrate bias control by 30 / 300W RIE source
• Helium back-side wafer cooling