STS APS DGRIE

STS APS DGRIE
Equipment Details
Technology	DRIE
Materials Restriction	Semi-Clean
Material Processed	SiO2 Fused silica Pyrex Quartz
Mask Materials	SPR 220 KMPR Polysilicon
Sample Size	150 mm
Gases Used	Ar, He, C4F8, O2, SF6, CF4, H2
Equipment Manual
Overview	System Overview
Operating Procedure	SOP
Supported Processes	Supported Processes
User Processes	User Processes
Maintenance	Maintenance

The SPTS APS Dielectric Etch tool is an ICP RIE tool used to etch 6" (150 mm) silicon dioxide, glass, and quartz wafers. It has a high power RF bias supply for generating ion bombardment to enhance etch rate. A high capacity turbo pump and advanced ICP source allow for very low pressure (1-10 mTorr) plasma processing, improving sidewall verticality. Very deep (100 μm) etches have been performed on fused silica and quartz substrates. It can also etch thin film oxide up to 8 μm thick with 90° ± 0.5° sidewall angles. Sub-micron feature etching has also been demonstrated (down to 100 nm linewidth). The tool will only accept 6” wafers - all smaller samples must be mounted to a carrier wafer.

Announcements

• [2018-07-25] The chuck has been replaced with an older chuck that we resurfaced while the new chuck is being repaired.

Capabilities

The STS APS system is designed for deep glass RIE but is also capable of high aspect ratio thin film etching at submicron resolution.

• SiO₂ films
  • Up to 8 μm
  • 0.26 μm/min
  • 2.5:1 selectivity to PR
  • Feature sizes down to 100 nm
• Fused silica, quartz, glass substrates
  • 100 μm depth
  • ~0.5 μm/min
  • Up to 5:1 selectivity to KMPR/SU-8
  • Feature sizes > 20 μm

System overview

Hardware details

• Gases
  • Active species: C₄F₈ (200 sccm), SF₆ (200 sccm), CF₄ (100 sccm)
  • Additives: O₂ (100 sccm), H₂ (50 sccm)
  • Diluants: He (500 sccm), Ar (200 sccm)
• Pressure
  • 1550 L/sec Mag 2000 CTS Turbo Pump
  • 2-250 mTorr
  • Fast acting VAT pendulum valve
• Chuck
  • 150 mm Wafer
  • 0-20 Torr Backside He Cooling
  • -20°C to 20°C
• Chamber
  • 120°C Walls
  • Aluminum Walls
• RF
  • 2500 W, 13.56 Mhz Coil
  • 1000 W, 13.56 Mhz Platen

Substrate Requirements

• 150 mm (6") wafers
  • Pieces and smaller wafers can be mounted to a carrier wafer at the Sample Mounting Station
• 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 APS DGRIE 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 info@lnf.umich.edu for any material requests or questions.

Approved materials

Supported processes

Main article: STS APS DGRIE/Processes

The primary recipes for the STS Glass Etcher are used for deep oxide/quartz/silica etching. The uk submicron etch is designed for thin-film (up to 8 μm) etching of oxide. Feature sizes can range from 100 nm to a full wafer. The Fused silica etch is designed for deep etching of fused silica, quartz, and glass. More details on the supported processes can be found on the Processes page.

In addition to the supported recipes, there are recipes available (largely uncharacterized) for a wide variety of materials, including non-reactive metals, PZT, and Silicon carbide. Some of these recipes are documented on STS APS DGRIE user processes. If you have a requirement outside those covered by, or are not getting satisfactory results from the standard recipes we strongly advise you to make helpdesk ticket to consult a tool engineer on what steps to take to improve your etch results.

Standard operating procedure

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Checkout procedure

1. Read through this page and the Standard Operating Procedure above.
2. Create a helpdesk ticket requesting training and attend an introductory training session with a tool engineer.
3. Practice with your mentor or another authorized user until you are comfortable running the tool on your own.
4. 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.

Maintenance

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 6:

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

After any chamber maintenance, the etch rate of the uk submicron etch is checked to verify the condition of the tool.To verify the condition of the tool The etch is run for 2 minutes on a 6" oxide coated wafer and the etch rate is measured in 25 locations. The average of this is shown below.