mems processing the preferred photoresist is a positive novalak photoresist the specific type of photoresist is selected for among other characteristics the desired depth of the photoresist layer the photoresist layer can be from 1 u03bcm to 40 u03bcm in thickness other suitable materials may be substituted and the discussion herein should not be interpreted to limit the invention the substrate material is preferably silicon however the substrate may be selected from any number of materials for example silicon ge gaas gasb plastic glass quartz or metals such cu al insb inas inp cdte and pbte other suitable materials may be substituted and the discussion herein should not be interpreted to limit the invention wet etching uses chemicals to etch particular exposed substrate materials and dry etching uses plasmas generally dry etching will etch any exposed surface whereas wet etching only etches surfaces with which the chemicals react dry etching tends to be anisotropic or have unidirectional etching properties whereas wet etching tends to be isotropic or etch any exposed material with some difference in etch rate depending on crystal structure the wet etchant used depends upon the second substrate material if sio 2 is used for the second substrate material then hf h 2 o is a preferred wet etchant to use if the second substrate is si then a preferred wet etchant is u201c hna u201d a mixture of hydrofluric acid hf nitric acid hno 3 and acetic acid ch 3 cooh additional etch materials for various substrates that may be used in the present invention are.