Self-aligned ridge waveguide laser structure, method for fabrication, and method for use with interposer-based pics
View Patent ↗A structure and method for providing alignment aids that are co-fabricated with the optical emission output from a laser pedestal are described. In embodiments, the alignment aids are formed using processes and masking layers that produce a ridge waveguide laser structure. The use of same masking processes for the laser and the alignment aids provides lithographic level precision in the positioning of the alignment aids in relation to the optical output from the laser device. Optoelectrical die formed with the alignment aids may be used with complementary interposer structures to enable alignment of optical output from lasers formed on the optoelectrical die with optical devices on the interposer.
1 . A method for forming a die comprising a ridge laser structure, the method comprising
concurrently forming a ridge laser emitting component of the ridge laser structure and two alignment features on a substrate,
wherein the ridge laser emitting component comprises a quantum well layer for generating an optical signal,
wherein a first alignment feature of the two alignment features comprises one or more first side surfaces for restricting movements of the die in a direction parallel to a lateral surface of the substrate and perpendicular to a propagation direction of the optical signal with the one or more first side surfaces disposed in a close proximity of one or more second side surfaces of an interposer when the die is mounted on the interposer,
wherein a second alignment feature of the two alignment features comprises one or more exposed portions of the substrate, with the one or more exposed portions of the substrate configured to contact one or more top surfaces of the interposer, and with a first distance between at least an exposed portion of the one or more exposed portions and the optical signal being substantially the same as a second distance between at least a top surface of the one or more top surfaces and an optical pathway on the interposer,
wherein the concurrently forming comprises depositing a ridge layer on a stack of layers,
wherein the concurrently forming further comprises patterning the ridge layer to form a ridge element of the ridge laser emitting component and a top portion of the first alignment feature,
wherein the concurrently forming further comprises patterning the stack of layers to form a bottom portion of the ridge laser emitting component comprising a quantum well and a bottom portion of the first alignment feature,
wherein the concurrently forming further comprises patterning the stack of layers to expose the one or more exposed portions of the substrate.
2 . A method as in claim 1 ,
wherein the first alignment feature is formed as a recess in the die with the one or more first side surfaces being one or more sidewalls of the recess.
3 . A method as in claim 1 ,
wherein the first alignment feature is formed as a protrusion from the die with the one or more first side surfaces being one or more sidewalls of the protrusion.
4 . A method as in claim 1 ,
wherein at least a first side surface of the one or more first side surfaces comprises a curved surface.
5 . A method as in claim 1 ,
wherein the first alignment feature is configured so that during a subsequent process of moving the die in a direction comprising the propagation direction, the first alignment feature guides the die movement to obtain a desired offset of the optical signal in the direction perpendicular to the propagation direction of the optical signal,
wherein the movement of the die is due to a misalignment of contact pads in the die and in the interposer.
6 . A method as in claim 1 ,
wherein the one or more first side surfaces comprise two first side surfaces with each first side surface configured to face a second side surface of the one or more second side surfaces, wherein the two first side surfaces are configured for preventing the die from moving in either of two opposite directions perpendicular to the propagation direction.
7 . A method as in claim 1 ,
wherein the one or more first side surfaces comprise two parallel first side surfaces facing away from each other, with the one or more second side surfaces disposed outside the two parallel first side surfaces.
8 . A method as in claim 1 ,
wherein the one or more first side surfaces comprise two parallel first side surfaces facing toward each other, with the one or more second side surfaces disposed inside the two parallel first side surfaces.
9 . A method as in claim 1 ,
wherein the first alignment feature comprises a wedge or a recess having a wedge shape comprising two first side surfaces, with a first first side surface of the two first side surfaces forming a first angle with the propagation direction and a second first side surface of the two first side surfaces being parallel to or forming a second angle on an opposite side of the first angle with the propagation direction.
10 . A method as in claim 1 ,
wherein the patterning the ridge layer comprises depositing a ridge mask comprising a first ridge mask portion for patterning the ridge element and a second ridge mask portion for patterning the top portion of the first alignment feature.
11 . A method as in claim 1 ,
wherein the patterning the ridge layer comprises depositing a first etch stop layer under the ridge layer, wherein the first etch stop comprises a lower etch rate than that of the ridge layer.
12 . A method as in claim 10 ,
wherein the patterning the stack of layers comprises depositing a stack mask comprising a first stack mask portion for patterning the stack of layers and a second stack mask portion for patterning the bottom portion of the first alignment feature,
wherein the first stack mask portion is larger than the first ridge mask portion,
wherein the second stack mask portion is similar to the second ridge mask portion.
13 . A method as in claim 1 ,
wherein the patterning the stack of layers comprises depositing a first etch stop layer on the stack of layers and under the ridge layer, followed by patterning the first etch stop layer and the stack of layers to form the bottom portion of the ridge laser emitting component and the bottom portion of the first alignment feature, wherein the first etch stop comprises a lower etch rate than that of the ridge layer.
14 . A method as in claim 1 ,
wherein the first alignment feature is formed as a recess in the die with the one or more first sides being one or more sidewalls of the recess, or
wherein the first alignment feature is formed as a protrusion from the die with the one or more first sides being one or more sidewalls of the protrusion.
15 . A method as in claim 1 ,
wherein at least a first side surface of the one or more first side surfaces comprises a curved surface.
16 . A method as in claim 1 ,
wherein the first alignment feature is configured so that during a subsequent process of moving the die in a direction comprising the propagation direction, the first alignment feature guides the die movement to obtain a desired offset of the optical signal in the direction perpendicular to the propagation direction of the optical signal.
17 . A method as in claim 1 ,
wherein the one or more first side surfaces comprise two parallel first side surfaces facing away from each other, with the one or more second side surfaces disposed outside or inside the two parallel first side surfaces.
18 . A method as in claim 1 ,
wherein the first alignment feature comprises a wedge or a recess having a wedge shape.
19 . A method for forming a die comprising a ridge laser structure, the method comprising
concurrently forming a ridge laser emitting component of the ridge laser structure and two alignment features on a substrate,
wherein the ridge laser emitting component comprises a quantum well layer for generating an optical signal,
wherein a first alignment feature of the two alignment features comprises one or more first side surfaces for restricting movements of the die by the one or more first side surfaces disposed in a close proximity of one or more second side surfaces of an interposer when the die is mounted on the interposer,
wherein a second alignment feature of the two alignment features comprises one or more exposed portions of the substrate, with the one or more exposed portions of the substrate configured to contact one or more top surfaces of the interposer, and with a first distance between at least an exposed portion of the one or more exposed portions and the optical signal being substantially the same as a second distance between at least a top surface of the one or more top surfaces and an optical pathway on the interposer,
wherein the concurrently forming comprises depositing a ridge layer on a stack of layers on an etch stop layer,
wherein the concurrently forming further comprises patterning the ridge layer to form a ridge element of the ridge laser emitting component and a top portion of the first alignment feature,
wherein the concurrently forming further comprises patterning the stack of layers to form a bottom portion of the ridge laser emitting component comprising a quantum well and a bottom portion of the first alignment feature,
wherein the concurrently forming further comprises patterning the stack of layers and the etch stop layer to expose the one or more exposed portions of the substrate,
wherein the etch stop comprises a lower etch rate than that of the stack of layers,
wherein the patterning the stack of layers comprises a different etch chemistry for the stack of layers as compared to the etch stop layer.
20 . A method for forming a die comprising a ridge laser structure, the method comprising
depositing a ridge layer on a stack of layers on an etch stop layer on a substrate, wherein the etch stop comprises a lower etch rate than that of the stack of layers,
concurrently forming a ridge laser emitting component of the ridge laser structure and two alignment features on the substrate,
wherein the ridge laser emitting component comprises a quantum well layer for generating an optical signal,
wherein a first alignment feature of the two alignment features comprises one or more first side surfaces for restricting movements of the die by the one or more first side surfaces disposed in a close proximity of one or more second side surfaces of an interposer when the die is mounted on the interposer,
wherein a second alignment feature of the two alignment features comprises one or more exposed portions of the substrate, with the one or more exposed portions of the substrate configured to contact one or more top surfaces of the interposer, and with a first distance between at least an exposed portion of the one or more exposed portions and the optical signal being substantially the same as a second distance between at least a top surface of the one or more top surfaces and an optical pathway on the interposer,
wherein the concurrently forming comprises patterning the ridge layer to form a ridge element of the ridge laser emitting component and a top portion of the first alignment feature,
wherein the concurrently forming further comprises patterning the stack of layers to form a bottom portion of the ridge laser emitting component comprising a quantum well and a bottom portion of the first alignment feature,
wherein the concurrently forming further comprises patterning the stack of layers and the etch stop layer to expose the one or more exposed portions of the substrate,
wherein the patterning the stack of layers comprises a different etch chemistry for the stack of layers as compared to the etch stop layer.