STS (now SPTS) Multiplex ICP ASE deep reactive ion etch system

Where the STS ASE fits

The STS Multiplex ICP ASE (Advanced Silicon Etch) is a deep reactive ion etcher built around the Bosch process: short etch steps in SF6 alternate with C4F8 passivation steps, producing deep, near-vertical trenches and through-wafer holes in silicon. A used STS ASE is still one of the most practical ways for a university or MEMS pilot line to etch cavities, comb drives, through-silicon vias and microfluidic channels. If the process is new to your group, our post on the Bosch process explains how the cycles shape the sidewall.

STS later became part of SPTS, whose current DRIE tools descend from this platform. Older ASE units are simpler than modern systems: fewer gas-switching tricks, slower rates on some recipes, but well understood and widely documented by university facilities. Bosch etching leaves scalloped sidewalls whose ripple depends on the cycle times. If smooth walls or a tight profile matter to your devices, budget time to develop the process rather than expecting a recipe that works on the first run.

What we inspect on a used ASE

DRIE chambers run hard: high RF power and heavy fluorocarbon deposition. On inspection we check:

• Chamber and ceramic parts: fluorocarbon build-up, cracking and erosion of the ceramic parts inside the coil and the chamber liners.
• Coil and platen RF: generator output, match tuning, and the 380 kHz unit if fitted.
• Platen and clamp: helium backside cooling, clamp condition and leak rate, platen temperature control.
• Gas switching: valve speed and reliability during the alternating cycles, mass flow controller response.
• Load lock and robot: wafer pickup and placement repeatability.
• Pumping: turbo hours, backing pump condition and throttle valve control.

The report includes base pressure, leak-up rate and, where the tool can run, a test etch with depth and profile photos.

Refurbishment

Refurbishing an ASE starts with a full chamber refurbishment: removal of fluorocarbon deposits, replacement of worn ceramics, seals and consumables, then reassembly and leak testing. We service the turbo, verify the RF chain and calibrate the mass flow controllers. A certified unit runs a reference Bosch recipe with the rate, selectivity and profile in the report.

Upgrades and spare parts

The upgrades we see most are a low-frequency platen generator for SOI work, dry backing pumps that tolerate fluorocarbon by-products better than oil-sealed pumps, and a new control PC. Spare parts come from used and third-party sources, and we tell you before purchase which items are scarce for that build, so you can hold critical spares. Our spare parts service covers sourcing for tools already in your lab.

Facilities

• Three-phase power, depending on configuration
• Process cooling water for RF generators, turbo and platen chiller
• SF6, C4F8, O2 and Ar supply
• Nitrogen for venting and pump purge
• Clean dry air for pneumatic valves
• Exhaust with abatement suited to fluorinated gases, where your site requires it

Buying advice

Confirm the wafer size, clamp type and whether the 380 kHz option is fitted. Ask for chamber cleaning history; units that ran long without cleaning may need new ceramics. Plan your exhaust and fluorinated gas handling early. The etch category lists ICP and RIE tools if DRIE is more than you need.