Fabrication process for a self-aligned optical subassembly

Abstract

Abstract A method is disclosed for forming a self-aligned optical subassembly for supporting an optical fiber and associated optical component(s). In particular, sequential masking layer/silicon substrate etch operations are performed so as to etch, in series, the largest opening first and the narrowest opening last. A series of mask/silicon etch operations may be performed to sequentially provide openings in the silicon of the desired thicknesses. That is, the thickness of masking layer (30) is now related (inversely) to the desired final depth of each opening. In particular, the masking layer comprises the greatest thickness (t₂) over the area associated with first groove (14), followed by a thickness of t₁ <t₂ over the area associated with second groove (16), where the masking material has been completely removed from the area associated with the deepest opening (12). Advantageously, the above-described process ot tailoring the thickness of the masking layer with respect to the desired final depths of the features (i.e., opening (12) and groves (14,16)) eliminates the need to perform any further photolithography operations in the formation of the final fiber stub subassembly. A first silicon etch may now be performed to provide for opening (12) to comprise a predetermined depth of d₁, where the predetermined may be controlled by the material used to etch, as well as the time and temperature conditions. For example, the etch may be performed using ethylenediamine pyrochatecol (EDP) at a temperature of 115°C in a nitrogen atmosphere, where it is known that this particular material will etch silicon at a rate of 25µm/hour. Subsequent to this first EDP etch, a masking layer etch operation (using, for example a plasma or buffered oxide) is performed to blanket remove a predetermined thickness of masking layer (30) sufficient to expose suface (11) of substrate (10) in the area of opening (16). This etch thus also reduces the thickness of masking layer (30) covering area (14). A second EDP etch is then performed so as to provide an opening (16) with a predetermined depth of d₂. The second EDP etch will also further etch first opening (12), resulting in opening (12) having a depth of d₁+d₂. After the second EDP etch is completed, a final masking material etch is performed to remove an amount of masking layer (30) sufficient to expose surface (11) of substrate (10) in the area of opering (14). A third EDP etch is then performed so as to form opening (14) to comprise a third predetermined depth d₃.

Inventors

• 👤 Mindaugas Fernand Dautartas
• 👤 Yiu-Huen Wong

Bibliographic Details