A gold deplating tool used in wide bandgap compound semiconductor manufacturing typically serves a specific and important purpose: selective removal of gold (Au) layers during device fabrication or rework. Wide bandgap semiconductors like silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga₂O₃) and aluminum nitride (AlN). These materials are used in power electronics, RF devices, and high-temperature applications due to their superior electrical and thermal properties.
Why Deplete Gold?
Gold deplating may be required for:
- Rework/repair: If there’s an error in patterning or a defect in the gold layer.
- Process corrections: Adjusting metallization without scrapping the entire wafer.
- Selective layer removal during a multi-step etching or patterning sequence.
Why Use Gold in These Devices?
Gold is commonly used in semiconductor processes for:
- Ohmic contacts
- Interconnects
- Bond pads
- Metal stacks
It provides excellent conductivity, chemical stability, and reliability, especially under harsh conditions.
Gold Depleting Tool Function
A gold deplating tool is designed to selectively remove gold layers from the wafer without damaging:
- The underlying semiconductor (e.g., GaN, SiC)
- Other metal layers
- Sensitive dielectric/passivation layers
Techniques may include:
- Wet chemical etching using solutions like potassium iodide (KI)/iodine or aqua regia
- Electrochemical deplating, which is more controlled and selective
- Plasma-based dry etching, though rare for gold
Tool Requirements in WBG Manufacturing
Because wide bandgap materials are expensive and fragile, gold deplating tools must offer:
- High selectivity
- Minimal substrate damage
- Precision control
- Cleanroom compatibility
- Low contamination risk