Wafer level method of forming side fiber insertion optoelectronic packages

Abstract

Optoelectronic packages and wafer level techniques for forming optoelectronic packages are described. In accordance with one apparatus aspect of the invention, a pair of substrates are bonded together to form an optical coupler. A first one of the substrates has a recess that faces the second substrate to at least in part define a channel suitable for receiving an optical transmission medium. A photonic device is mounted on a mounting surface of the second substrate that is opposite its bonded surface. The photonic device faces the reflective surface and an optical path is formed between the channel and the photonic element that both reflects off of the reflective surface and passes through the second substrate. In some embodiments an integrated circuit device and/or solder bumps are also attached to the mounting surface and the second substrate has conductive traces thereon that electrically couple the various electrical components as appropriate (e.g., the photonic device, the integrated circuit device, the solder bumps and/or other components). The substrates may be formed from a wide variety of materials including, glass, plastic and silicon. In some embodiments, at least the second substrate is formed from an optically transparent material and the optical path passes directly though the optically transparent material. In a method aspect of the invention, a variety of wafer level methods for forming such devices are described.

1 . A method of forming optoelectronic devices, the method comprising:
 providing a first substrate having a multiplicity of device areas defined therein, each device area of the first substrate including a recessed region and a reflective surface formed on a wall of the recessed region wherein the recessed region further includes a lowered portion that forms a step that serves as an alignment stop for an optical fiber arranged in the recessed region;   providing a second substrate having a multiplicity of device areas that generally correspond to the device areas of the first substrate;   bonding the second substrate to the first substrate such that the recessed regions on the first substrate face a first surface of the second substrate, whereby the bonded substrates have a multiplicity of device areas corresponding to the device areas of the first and second substrates;   attaching a multiplicity of photonic devices to a second surface of the second substrate located generally opposite the first surface of the second substrate such that each device area of the second substrate includes a photonic device, each device area in the second substrate further including an optical path through the second substrate arranged such that after the substrate bonding and photonic device attachment have been completed, the photonic devices are arranged to optically communicate with the minors in their associated device areas through the second substrate; and   singulating the bonded first and second substrates to form a multiplicity of singulated optoelectronic devices, each optoelectronic device corresponding to an associated device area on the bonded substrates, each singulated optoelectronic device having a channel suitable for receiving at least one optical fiber that extends between the first and second substrates and is defined at least in part by the corresponding recessed region in the first substrate wherein the alignment stop of the channel is further arranged to enable a terminal end of the received optical fiber to come into contact with the step thereby setting a desired offset with the mirror of the associated device area.   
   
   
       2 . A method as recited in  claim 1 , wherein the second substrate further includes a plurality of recessed regions and the channels formed in the singulated optoelectronic devices are also defined in part by the corresponding recessed regions in the second substrate. 
   
   
       3 . A method of forming optoelectronic devices, the method comprising:
 providing a first substrate having a multiplicity of device areas defined therein, each device area of the first substrate including a recessed region and a reflective surface formed on a wall of the recessed region;   providing a second substrate having a multiplicity of device areas that generally correspond to the device areas of the first substrate wherein the second substrate further includes a plurality of recessed regions;   bonding the second substrate to the first substrate such that the recessed regions on the first substrate face a first surface of the second substrate, whereby the bonded substrates have a multiplicity of device areas corresponding to the device areas of the first and second substrates;   attaching a multiplicity of photonic devices to a second surface of the second substrate located generally opposite the first surface of the second substrate such that each device area of the second substrate includes a photonic device, each device area in the second substrate further including an optical path through the second substrate arranged such that after the substrate bonding and photonic device attachment have been completed, the photonic devices are arranged to optically communicate with the mirrors in their associated device areas through the second substrate; and   singulating the bonded first and second substrates to form a multiplicity of singulated optoelectronic devices, each optoelectronic device corresponding to an associated device area on the bonded substrates, each singulated optoelectronic device having a channel defined in part by the corresponding recessed regions in the second substrate and suitable for receiving at least one optical fiber that extends between the first and second substrates and is defined at least in part by the corresponding recessed region in the first substrate; and   wherein each recess in the first substrate includes a step such that each recess in the first substrate includes a deeper portion and a shallower portion and wherein the shallower portion includes the reflective surface;   each recess in the second substrate includes a side wall that is aligned with the step when the first and second substrates are bonded; and   the step and side wall cooperate to serve as an alignment stop for an optical fiber received by the channel after singulation.   
   
   
       4 . A method as recited in  claim 1 , wherein each recess in the first substrate includes a step such that each recess in the first substrate includes a deeper portion and a shallower portion, wherein the shallower portion includes the reflective surface, and wherein the step is suitable for serving as an alignment stop for an optical fiber received by the channel after singulation. 
   
   
       5 . A method as recited in  claim 1 , wherein the second surface of the second substrate has a plurality of conductive traces formed on each device area of the second substrate, the method further comprising attaching a plurality of dice to the second surface of the second substrate prior to singulation such that each device area of the second substrate includes a die capable of electrical communication with the photonic device associated with the device area over at least one of the conductive traces associated with the device area. 
   
   
       6 . A method as recited in  claim 5 , further comprising attaching a plurality of solder bumps to the second surface of the second substrate prior to singulation, wherein at least some of the conductive traces associated with each device area electrically couple the die associated with the device area to solder bumps associated with the device area to facilitate attachment of the associated optoelectronic device to an external device after singulation. 
   
   
       7 . A method as recited in  claim 1 , wherein the first and second substrates are each wafers formed from the group consisting of glass, plastic and silicon. 
   
   
       8 . A method as recited in  claim 1 , wherein the first and second substrates are substantially formed from a glass or plastic material that is transparent or semi-transparent to wavelengths of light in an intended operational range of the optoelectronic devices. 
   
   
       9 . A method as recited in  claim 1 , wherein:
 the first and second substrates are each wafers are formed substantially from silicon;   the wafers bonding is accomplished by ionic bonding; and   the second wafer has a plurality of vias formed therein, each via being formed in an associated device area to provide the optical path between the photonic device and the mirror associated with the device area.   
   
   
       10 . A method as recited in  claim 1 , wherein the substrates are bonded together by soldering. 
   
   
       11 . A method as recited in  claim 1 , further comprising a plurality of lenses formed on the second substrate, each lens being associated with an associated device area and positioned such that after bonding and singulation, light passing between a photonic element on the associated photonic device and the associated reflective surface pass through the lens. 
   
   
       12 . A method as recited in  claim 1 , wherein each device area includes a plurality of photonic devices. 
   
   
       13 . A method as recited in  claim 1 , further comprising, for each of a plurality of the singulated optoelectronic devices:
 inserting an optical fiber having a planar facing surface at its terminal end into the channel of such that the planar facing surface of the optical fiber registers against an alignment stop associated with the channel such that an optical beam passing through the fiber does not pass through the alignment stop; and   wherein the photonic device is arranged to optically communicate with the optical fiber via an optical path in which light passes through the second substrate and reflects off of the reflective surface as the light passes between the photonic device and the optical fiber.   
   
   
       14 . A wafer level method of forming optoelectronic devices, the method comprising:
 bonding a first surface of a first wafer having a multiplicity of device areas defined therein, to a first surface of a second wafer having a corresponding multiplicity of device areas, wherein each device area of the first substrate includes a recessed region and a reflective surface formed on a wall of the recessed region and each device area wherein the wall of the recessed region includes a deeper portion and a shallower portion defining a stepped feature and wherein each shallower portion includes an associated mirror, the stepped feature arranged such that when a front optical face of an optical fiber is in contact with the stepped feature the fiber lies at a desired distance from the reflective surface;   attaching a multiplicity of photonic devices to a second surface of the second substrate located generally opposite the first surface of the second substrate such that each device area of the second substrate includes a photonic device, each device area in the second substrate further including an optical path through the second substrate arranged such that after the substrate bonding and photonic device attachment have been completed, the photonic devices are arranged to optically communicate with the minors in their associated device areas through the second substrate; and   singulating the bonded first and second substrates to form a multiplicity of singulated optoelectronic devices, each optoelectronic device corresponding to an associated device area on the bonded substrates, each singulated optoelectronic device having a channel suitable for receiving at least one optical fiber that extends between the first and second substrates and is defined at least in part by the corresponding recessed region in the first substrate.   
   
   
       15 . A method as recited in  claim 14 , wherein:
 the second wafer further includes a plurality of recessed regions and the channels formed in the singulated optoelectronic devices are also defined in part by the corresponding recessed regions in the second substrate,   each recess in the first substrate includes said stepped feature such that each recess in the first substrate includes a deeper portion and a shallower portion and wherein the shallower portion includes the reflective surface;   the stepped feature is suitable for serving as an alignment stop for an optical fiber received by the channel after singulation; and   the second surface of the second substrate has a plurality of conductive traces formed on each device area of the second substrate, the method further comprising attaching a plurality of dice to the second surface of the second substrate prior to singulation such that each device area of the second substrate includes a die capable of electrical communication with the photonic device associated with the device area over at least one of the conductive traces associated with the device area.   
   
   
       16 . A method of assembling an optoelectronic device, the method comprising:
 providing an optoelectronic device having a photonic device and a pair of substrates, wherein the pair of substrates are bonded together and a channel is defined between the substrates, the channel including a reflective surface formed on a first one of the substrates and an alignment stop, and wherein the photonic device is mounted on a surface of the second substrate that faces away from the channel, there being an optical path between the photonic device and reflective surface that passes through the second substrate; and   inserting an optical fiber into the channel such that the front optical face of the optical fiber registers against the alignment stop; and   wherein the photonic device is arranged to optically communicate with the optical fiber via an optical path in which light passes through the second substrate and reflects off of the reflective surface as the light passes between the photonic device and the optical fiber.