Specific Process Knowledge/Etch

Wet etch or dry etch

Etching at Danchip can be done either with wet chemistry or in dry etch equipment. In general wet chemistry etches isotropically in most materials were as dry etch techniques can be optimized to transfer a given mask pattern with vertical sidewalls (anisotropically) to a given substrate.

Advantages of wet chemistry over dry etch techniques are:

• An often high etch rate difference of different materials giving raise to a high selectivity of the material to be etched compared to underlaying layers or mask materials.
• Time saving: You can often etch 25 wafers at a time in wet chemistry where as dry etch equipment can only handle one wafer at a time.
• Easy to start op new etch solutions.

Advantages of dry etch over wet chemistry:

• Anisotropic etch can be done.
• The etch do not attach the backside of the sample.

Choose material to be etched

• Aluminium
• Chromium
• Titanium
• Gold
• Platin
• Polymer
• Silicon
• Silicon Nitride
• Silicon Oxide
• Bulk Glass - Borofloat (pyrex) and fused silica (quartz)

Choose a dry etch equipment

• RIE (Reactive Ion Etch)
• ASE (Advanced Silicon Etch)
• AOE (Advanced Oxide Etch)

Choose a wet etch

• Wet Silicon Nitride Etch
• Wet Silicon Oxide Etch (BHF)
• KOH Etch - Anisotropic silicon etch
• Wet Polysilicon Etch - Isotropic silicon etch
• Wet Aluminium Etch

Work in progress - dry etch meeting

• Deep silicon etch on the DRIE Pegasus