Xactix XeF2
The Xactix Xetch X.3.B is a xenon difluoride etching tool that will etch silicon, molybdenum, and germanium isotropically. XeF2 is a solid at atmosphere but will sublimate at vacuum. The tool uses two expansion chambers to alternatively sublimate the XeF2 and release it into the etch chamber. The etch rate is highly dependent on the chamber's loading. A wafer with only a thin trench exposed will etch very fast where as a blanket 100 mm Si wafer may etch as slow as 800 Å/cycle. Wafers are manually loaded directly into the chamber, and the tool can accommodate pieces up to 150 mm wafers.
| Xactix XeF2 | |
|---|---|
 XeF2 etching tool | |
| Equipment Details | |
| Technology | Etching |
| Materials Restriction | Restricted |
| Material Processed | Si, Mo and Ge |
| Mask Materials | Pr |
| Sample Size | Pieces to 150 mm |
| Gases Used | XeF2 |
| Equipment Manual | |
| Overview | Overview |
| Operating Procedure | SOP |
| Supported Processes | Supported Processes |
| Maintenance | Maintenance |
 | This system is not for deep silicon etching. |
Contents
Capabilities
- Etches Silicon, Molybdenum and Germanium
- High selectivity to many materials including:
- Long undercuts are possible (> 100 µm)
- No stiction associated with wet etching
- Doesn’t quickly attack BOSCH process passivation layer
- Additional Info
System Overview
Hardware Details
- Gases
- XeF2
- N2
- Pressure
- 0 - 6 Torr XeF2
- 0 - 20 Torr N2
Substrate Requirements
- Pieces to 150 mm
- No mounting required
Material Restrictions
A full list of approved materials is included at the end of this section. The materials can be classified into four categories, detailed below. Use of any material outside of these conditions requires approval by the LNF staff via a helpdesk ticket.
- Materials etchedː These materials can be etched in the system, and a recipe is available for them. However, this doesn't mean it is the best-known or recommended method.
- Mask materialsː This includes any material that will be exposed to the plasma for the majority of the process. The most common mask materials are photoresist and silicon dioxide.
- Etch stop materialsː This includes any material that will be exposed briefly to the plasma.
- Buried materialsː These materials may be present on the sample, but may not be exposed to the plasma. They may be covered by the mask or on the back of the sample, provided that the sample is mounted to a carrier wafer.
Below is a list of approved materials for the tool. Approved means the material is allowed in the tool under the classification described above. If a material is not listed, please create a helpdesk ticket or email info@lnf.umich.edu for any material requests or questions.
Supported Processes
A table of etch rates for the standard process can be seen below, these were all run with 20 second cycle times and 3 Torr XeF2 pressure. More process information for this tool can be found on it's supported processes
| Material | Size | % Open Area | Etch Rate (Å/cycle) |
|---|---|---|---|
| Si | 100 mm | 100% | 800 |
| Si | 1 cm2 | 100% | 10,000 |
| SPR 220 | 100 mm | 100% | < 5 |
Standard Operating Procedure
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Checkout Procedure
- Read through the User Manual above.
- Complete the SOP quiz here.
- Complete the process request form.
- Schedule a time for a checkout:
- Find an available time for checkout here.
- Verify that the tool is available in the LNF Online Services at the time you are requesting.
- After confirmation that the event is scheduled in Calendly, invite the staff member assigned to your event to a Staff Support reservation at that time.
- Create a helpdesk ticket for final confirmation of your checkout appointment.
- Authorization will be provided pending successful completion of the quiz and demonstration of proper tool use in the presence of a tool engineer.
Maintenance
Every month the chamber's leak rate is checked along with the XeF2 usage.