Specific Process Knowledge/Etch/ASE (Advanced Silicon Etch)

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The ASE

STS ASE - positioned in cleanroom B-1. Photo: DTU Nanolab internal

Name: M/PLEX ICP - ASE (Advanced Silicon Etcher)
Vendor: STS (now SPTS)
The ASE was the first ICP (Inductively coupled plasma) tool at DTU Nanolab. It was manufactured by STS and is called the ASE (Advanced Silicon Etcher). Originally the main purpose of the ASE was etching of silicon using the Bosch process. However, after the acquisition of the DRIE-Pegasus and the retirement of our old RIE's the ASE will only serve as a "dirty" plasma etcher, etching silicon, Silicon oxide and silicon nitride on wafers with small amount of metals exposed and as a polymer etcher. The rule is that samples with up to 4 cm2 of metal on the surface will be allowed to process. Extra gasses was been added to the machine to allow SiO2 and SiN etching. Using these gasses may affect the conditioning of the chamber and thereby the stability of processes. Any clean processes and sensitive processes should take place in to the DRIEs or elsewhere.

In the case of the silicon etching on the ASE, an etch phase with SF₆ and O₂ alternates with a passivation phase with C₄F₈.

The user manual, quality control procedure and results, user APV(s), technical information and contact information can be found in LabManager:

Equipment info in LabManager

Process information

• Etch of Silicon using ASE
• Etch of polymers using ASE
• Etch of SiO2 using ASE

An overview of the performance of the ASE and some process related parameters

Purpose	Dry etch of	Silicon Thin layers of Silicon oxide and silicon nitride Polymers such as polyimide, PDMS, PMMA, BCB and resists
Performance	Etch rates	Silicon: ~0-15 µm/min (depending on features size and etch load) Silicon oxide: <0.1 µm/min Silicon nitride: <0.1 µm/min
	Anisotropy	Good
Process parameter range	Process pressure	~0.1-95 mTorr
	Gas flows	SF6: 0-600 sccm O2: 0-99 sccm C4F8: 0-300 sccm Ar: 0-142 sccm CF4: 0-99.9 sccm CHF3: 0-99.9 sccm H2: 0-40 sccm He: 0-500 sccm
Substrates	Batch size	1 4" wafer per run 1 2" wafer per run (requires carrier) Or several smaller pieces on a carrier wafer
	Substrate material allowed	Silicon wafers with layers of silicon oxide or silicon (oxy)nitride Quartz wafers
	Possible masking material	Photoresist/e-beam resist PolySilicon Silicon oxide or silicon (oxy)nitride Aluminium