Patent ID: 7635555

Claim:
A method for fabricating polymer ridged waveguides by using tilted immersion lithography comprising steps of: [1] preparing step: preparing a silicon base plate, coating a SiO 2 layer on said silicon base plate, then coating a photoresist layer on said SiO 2 layer; heating said silicon base plate, SiO 2 layer and photoresist, covering a mask thereon, said mask having a plurality of light-penetrating portions; preparing a container with a liquid filled in said container; [2] calculating step: by using the Fresnel equations: n 1 ⁢ sin ⁢ ⁢ θ 1 = n 2 ⁢ sin ⁢ ⁢ θ 2 n 2 ⁢ sin ⁢ ⁢ θ 2 = n 3 ⁢ sin ⁢ ⁢ θ 3 so ⁢ ⁢ that n 1 ⁢ sin ⁢ ⁢ θ 1 = n 3 ⁢ sin ⁢ ⁢ θ 3 sin ⁢ ⁢ θ 3 = ( n 1 n 3 ) ⁢ sin ⁢ ⁢ θ 1 θ 3 = sin - 1 ⁢ { ( n 1 n 3 ) ⁢ sin ⁢ ⁢ θ 1 } wherein θ 1 is defined as a first tilting angle between an entering UV light and a referential vertical line normal to said silicon base plate, SiO 2 layer, photoresist, and mask; θ 2 is defined as a second tilting angle between a refracted light and said referential vertical line; θ 3 is defined as a third tilting angle which is the tilting angle of the tilting surface of ridged waveguides; n 1 is a refracted index of said liquid; n 2 is a refracted index of said mask; n 3 is a refracted index of said photoresist; [3] first tilted immersion lithography step: placing said heated silicon base plate, SiO 2 layer, photoresist, and mask in said liquid at a position having said first tilting angle; starting said entering UV light into said liquid at said first tilting angle; said entering UV light passing through said light-penetrating portions and then refracting at said second tilting angle inside said mask and the refracting at said third tilting angle inside said photoresist so as to conduct a first tilting exposure and then to form at least a first forming portion; [4] rotating 180-degree step: rotating said silicon base plate, SiO 2 layer, photoresist, and mask 180 degrees; [5] second tilted immersion lithography step: placing said rotated silicon base plate, SiO 2 layer, photoresist, and mask in said liquid at the same position having said first tilting angle; starting the entering UV light again into said liquid at said first tilting angle; said entering UV light passing through said light-penetrating portions and the refracting at said second tilting angle inside said mask and then refracting at said third tilting angle inside said photoresist so as to conduct a second tilting exposure and then to form at least a second forming portion; and said first forming portion and said second portion being partially overlapping so as to form a substantially trapezoid zone; and [6] finishing step: removing non-exposure potion of said photoresist; forming a polymer ridged waveguides that is the substantially trapezoid zone consisting of said partially overlapped first forming portion and second portion; said polymer ridged waveguides having two end surface with said third tilting angle.