STS Pegasus 4

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STS Pegasus 4
Equipment Details
Manufacturer SPTS Technologies Ltd.
Model Pegasus
Technology DRIE
Materials Restriction Semi-Clean
Material Processed Si
Mask Materials PR, SiO2
Sample Size 100 mm
Gases Used Ar, C4F8, O2, SF6
Equipment Manual
Overview System Overview
Operating Procedure SOP
Supported Processes Supported Processes
User Processes User Processes
Maintenance Maintenance

The SPTS Pegasus 4 is a Deep Reactive Ion Etch (DRIE) tool used to etch 4" (100 mm) silicon wafers using the Bosch process. It has a high power ICP source and is capable of fast (over 20 μm/min), high aspect ratio (up to 100:1) anisotropic etching of silicon. Fast-acting, high precision MFCs and VAT pendulum valve and a high capacity turbo pump provide fast switching times (down to 1s), enabling reduced undercut and sidewall roughness. Sub-micron feature etching has been demonstrated (down to 100 nm linewidth). Etch rate varies with feature size and density, so a characterization run is strongly recommended with any new mask.


  • [2015-11-18] - Semi-annual maintenance increased etch rates slightly. Please double-check your process. Current etch rates (for 100 µm trench) as follows:
    • LNF Recipe 1: 6.19 um/min
    • LNF Recipe 2: 16.14 um/min
    • LNF Recipe 3: 16.55 um/min
  • [2015-01-09] - Added tool-wide 15% increase in bias


  • High etch rates ~15 µm/min
  • Nearly vertical sidewalls ~89°
  • High selectivity to photoresist and SiO2

System Overview

Hardware Details

  • Gases
    • High Precision Fast Acting Chamber Mounted MFC's
      • C4F8 - 400 sccm
      • SF6 - 1200 sccm
      • O2 - 200 sccm
    • Standard Gasbox Mounted MFC
      • Ar - 283 sccm
  • Pressure
    • 1550 L/sec Mag 2000 CTS Turbo Pump
    • 2-250 mTorr
    • Fast acting VAT pendulum valve
      • Allows fast switching of BOSCH recipes (~1.5 seconds minimum)
  • Chuck
    • 100 mm Wafer
    • 0-20 Torr Backside He Cooling
    • -20°C to 20°C
  • Chamber
    • 120°C Walls
    • Aluminum Walls
  • RF
    • 5 kW, 13.56 Mhz Coil
    • 300 W, 13.56 Mhz Platen
    • 500 W, 380 kHz Platen with Pulsed Power Supply
    • 10 A Chamber Outer Electromagnet
    • 30 A Chamber Outer Electromagnet

Substrate Requirements

  • 100 mm (4") wafers
  • If the etch will leave less than 100 µm remaining, a carrier wafer must be used
  • Sample/carrier must be conductive, or a semiconductor for wafer to clamp on electrostatic chuck
    • Pyrex glass with an Si layer on top has worked

Material Restrictions

The STS Pegasus 4 is designated as a Semi-Clean class tool. Below is a list of approved materials for the tool. Approved means the material is allowed in the tool under normal circumstances. If a material is not listed, please create a helpdesk ticket or email for any material requests or questions.

Supported Processes

The primary recipes for the STS Pegasus 4 are used for deep silicon etching. There are four main Bosch process recipes with varying properties. The tool also has an oxynitride etch that may be used to etch a mask layer prior to the Si etch, but this may be performed by other tools more effectively. There is also a thinning recipe designed to quickly etch a wafer without a mask. More details on supported processes can be found on the Processes page.

In addition to these, this tool has a number of user-created recipes for specific processes. Some of these recipes are documented on STS Pegasus 4 User Processes. For more information, please contact the tool engineers via the helpdesk ticket system.

Standard Operating Procedure

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Checkout Procedure

  1. Read through the Standard Operating Procedure above.
  2. Complete the training request form.
  3. Create a Helpdesk Ticket requesting training.
  4. A tool engineer will schedule a time for initial training.
  5. Practice with your mentor or another authorized user until you are comfortable with tool operation.
  6. Schedule a checkout session with a tool engineer via the helpdesk ticket system. If this checkout is successful, the engineer will authorize you on the tool.


In order to provide reliable operating conditions, maintenance is performed weekly on the tool including inspecting and cleaning the chamber. The following regular maintenance is performed on the STS Pegasus 4:

  • Weekly
    • Wipe down chamber walls
    • Clean process kit
    • Plasma clean and condition
  • Monthly
    • Check wafer centering
    • Clean clamping ring
  • Bi-annually
    • Change and clean source ceramics
  • Annually
    • Refurbish turbo pump
    • Clean APC valve, foreline valve, baratron valve

After any chamber maintenance, the etch rate of the standard recipes is checked, as described below.

LNF Recipe 1, 2, 3

To verify the condition of the tool an etch is performed on recipe 1, 2 and 3, rotating each week. The etch rate is measured on a 100 um wide trench in 5 locations. The average of this is shown below.