EDP etchant

FIGURE 7.25. The effect of potential on etch rate of silicon in EDP etchant. After Gealer et al." (Reproduced by permission of The Electrochemical Society, Inc.)... 

Ethanolamine. Ethanolamine (NH2CH2CH20H)-based anisotropic etchants have been developed so as to replace the toxic EDP etchant. ° Linde and Austin reported a functional formula of 100 g gallic acid -1- 305 ml ethanolamine -1- 140ml water... 

Combining DRIE and anisotropic wet etching can produce unique structures. For example, (111) silicon cannot be etched by the standard KOH, TMAH, and EDP etchants, but if an initial trench has been etched by DRIE, fast-etching crystal planes are exposed, and wet etching can proceed. If this is combined with spacer structures to protect sidewalls and another DRIE step, (111) free-standing silicon structures can be made. 

Bulk and surface micro machining constitute the main 3D-semiconductor processes. Wet etchants such as KOH, EDP or TMAH or alternatively, a dry etching... 

Alkaline solutions are another major group of etchants widely used for etching of silicon materials. The most commonly used alkaline solutions have been KOH and EDP (or EPW) which is a mixture of ethylenediamine (ED or E), pyrocatechol (P), and water Other solutions such as NH4OH, hydrazine, ethanolamine, and tetram-... 

The anisotropic behavior of some etchants, such as EDP, KOH, NaOH and TMAH, means that etching in the different crystallographic directions proceeds at different rates [7, 13, 14]. The most slowly etched directions are those in the (111)... 

Table 3.5 Principal characteristics of three different anisotropic etchants [9]. (EDP = ethylenediamine pyrocathechol.)... 

Silicon Micromachining, Fig. 2 Schematic of cross-sectional view of anisotropically etched microchannels (a) in (100) silicon and (b) in (110) and (c) of 3-D aerial view of anisotropically etched microchannels in (100) silicon using wet chemical etchants of KOH, EDP, or TMAH... 

If silicon is highly doped, particularly with boron, then silicon will be etched very slowly by the previously mentioned wet chemical etchants such as KOH, EDP, and TMAH. One can use ion implanting or diffusing boron into silicon to form a thin etch-stop layer. Since non-highly doped silicon will be etched very fast, this thin etch-stop layer will stay as a free-standing... 

HNA (HF + HNO3 + Acetic Acid) Alkali-OH Comparison of Example Bulk Silicon Etchants EDP TMAH XeFj (ethylene (tetramethyl-diamine ammonium pyrochate- hydroxide) chol) Sp0 Plasma DRIE (Deep Reactive Ion Etch)... 

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