Process for making light waveguide element
A light waveguide element is made by forming only an upper clad layer ( 40 ) and a core layer ( 32 ) without etching an optical axis height-adjusting sections. By using plasma chemical vapor deposition (CVD) which is good at controlling the film thickness, it is possible to provide without difficulty a light waveguide element with a height-adjusting section that has a precise film thickness, making it possible to provide precise optical axis vertical alignment upon mounting. By forming alignment markers in the same photolithography as that of the core formation, it is possible to provide precise horizontal optical axis alignment.
1. A process for making a light waveguide element mounted on a mount board along with an optical fiber and photoelectric components, comprises the steps of:
forming a core as a light path on a substrate serving as a lower clad layer; and
forming a T-shaped upper clad layer having a central section elevated from opposite-side optical axis height-adjusting sections to cover said core, said T-shaped clad layer-forming step comprises the steps of:
forming both said core and a first height-adjusting layer on said substrate;
patterning an etching stopper film on said first height-adjusting layer;
forming a first upper clad layer over an entire surface including said core and said etching stopper film;
forming an etching mask on said first clad layer to cover an area above said core;
etching off a portion of said first upper clad layer that is other than said area covered by said etching mask until said etching stopper film is exposed;
removing only said etching mask; and
forming a second upper clad layer over an entire surface including said etching stopper film, said first upper clad layer.