Wet Chemical Etching

In order to transfer patterns into semiconductor material or into applied coatings a wide variety of etching methods is used. Wet and dry etching complement one another corresponding to material and object of pattern transfer.

A wide experience is available in exploiting the specific characteristics of wet chemical etching:

• Preferential etching based on crystallographic orientation and preparation of desired edge geometry
• Specific under-etching of structures
• Material-selective etching including etch stop
• Etching procedure with end-point detection specific to the material

To achieve desired uniformity and reproducibility of etching and rinsing automatic processing tools are used:

• Etch processing system Hamatech HME 900
• Etch processing system SSEC M 3300

In addition, uncritical etching techniques as well as etching for special purposes can be carried out manually on wet chemical benches under laminar flow.

In detail, the following machines (manufacturer SENTECH Instruments) are available:

• 4 RIE reactors, type SI591 (process gases O₂, SF₆, CF₄, BCl₃, Cl₂, Ar)
• 3 RIE reactors, type SI100 (process gases O₂, SF₆, CF₄)
• 2 ICP reactors, type SI500 (process gases O₂, SF₆, BCl₃, Cl₂, Ar, He)
• 1 RIE reactor, type SI500 RIE (process gases O₂, BCl₃, Cl₂, Ar, He)

Using this equipment the following materials can be structured:

• Polymers (photo and electron beam resists, polyimides, BCB, SU8, ...)
• Insolators (SiNx, SiO₂, ...)
• Metals (Pt, Au, W, WSix, WSiNx, Al, Ti, Ge, ...)
• III-V semiconductors (GaAs, AlGaAs, InGaAs, InGaP, InGaAsP, InP, GaN, AlGaN ...)

For in-situ process control 7 laser interferometers are routinely applied (GF-Measuring Technique, type NANOMES)

Selection of sophisticated process building blocks based on dry etching:

• Emitter structuring for GaAs HBTs
• Ridge and lattice structuring for laser devices
• GaAs and InP VCSEL etching
• GaAs via etching in the back-side process
• SiC via etching in the back-side process
• GaN / AlGaN structuring for HEMT and laser applications
• AlN/Saphir structuring