Controlled diffusion partial etching

A single step partial etching process for etching a substrate to produce at least two areas having substantially different post-etching depths, said process comprising the steps of:

• applying a resist mask to selected portions of the substrate;
• patterning a first mask area over a first portion of said substrate to provide an etch pattern establishing a critical etch space for etching said first area to a first average depth where said first mask area is of predetermined planar size and shape and said mask is comprised of a plurality of alternating first mask land features each of which has a maximum width which is less than the first average depth and a plurality of first mask openings interposed between such first mask land features, said first average depth being determined for a predetermined etching time by the width of the first mask land features and the width of the first mask openings which are selected to have dimensions so that the first mask area is a critical etch space wherein the width of the exposed substrate between mask edges is selected so that the etch factor is reduced over the etch factor otherwise applicable to the substrate;
• patterning a second mask area on a second portion of said substrate, where said second mask area has at least one opening of predetermined size and shape;
• and
• isotropically etching the entire substrate for a predetermined time wherein the critical etch space of said first mask area is etched to a lesser depth than the depth of the second mask area due to the reduced etch factor of the first mask area.

A single stage expose/etch partial etching process for fabricating at least two areas of differing remaining thicknesses in a substrate having an original thickness, said process comprising:

• applying a resist mask to the substrate;
• patterning in said mask a first area of a first predetermined planar size and planar shape having at least one opening, dimensioned to provide a first area etch factor;
• patterning in said mask a second area of a second predetermined planar size and planar shape to form a plurality of second mask openings and second mask land features, wherein the width of the second mask land features and the width of the spacings between the second mask land features are selected to provide at least one opening characterized by a critical etch spacing such that the second area has a second area etch factor and wherein the second area etch factor is reduced relative to the first area etch factor;
• and
• etching the substrate for a predetermined time through the first and second mask areas, thereby etching the substrate corresponding to the second mask area to a lesser depth than substrate corresponding to the first mask area.