Reflective layer buried in silicon and method of fabrication
AssigneeTrustees of Boston University
InventorsM. Selim Unlu, Matthew K. Emsley
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Abstract
A silicon wafer having a distributed Bragg reflector buried within it. The buried reflector provides a high efficiency, readily and accurately manufactured reflector with a body of silicon. A photodetector using the buried layer to form a resonant cavity enhancement of the silicon's basic quantum efficiencies and selectivity is provided. The DBR is created by bonding of two or more substrates together at a silicon oxide interface or an oxide-oxide interface. In the former, an hydrogen implant is used to cleave silicon just above the bond line. In the latter, the bonding is at the oxide layers.
Claims31
A silicon photodetector assembly adapted for at least one frequency of light comprising:
- a silicon body having a light admitting surface;
- a buried Distributed Bragg Reflector (DBR) located beneath said silicon body and facing said light admitting surface, at least one pair of adjacent layers of said DBR being bonded together;
- doped semiconducting layers adjacent said light admitting surface and said DBR respectively, one of said semiconducting layers being doped p type and the other of said semiconducting layers being doped n type;
- said light admitting surface and said DBR forming a resonant cavity to said at least one frequency of light.
The photodetector of claim 8 wherein said bonded layers are bonded at silicon and silicon dioxide surfaces.
A method for fabricating a silicon photodetector assembly adapted for at least one frequency of light comprising the steps of:
- providing a first body of silicon having a layer of silicon dioxide on a surface thereof;
- providing a second body of silicon;
- implanting hydrogen atoms at a predetermined depth in said silicon surface forming a boundary between hydrogen implanted silicon and unimplanted silicon;
- bonding a silicon surface of said second body to the silicon dioxide layer of the first body;
- separating the hydrogen implanted silicon from silicon not hydrogen implanted at said boundary thereby exposing a separated surface;
- providing a further body of silicon having a layer of silicon dioxide thereon;
- Implanting hydrogen atoms at a predetermined depth in said further body forming a boundary between hydrogen implanted silicon and unimplanted silicon;
- bonding the silicon dioxide layer of said further body to said exposed silicon surface;
- separating the hydrogen implanted silicon from silicon not hydrogen implanted at said boundary of said further body thereby exposing a separated surface thereof;
- doping said further body near the separated surface to create a first semiconducting region of one of p and n types;
- providing a silicon layer on the separated surface of said further body to form a cavity for light coupled into the silicon layer from a light admitting surface thereof;
- and
- doping said silicon layer near the light admitting surface to create a second semiconducting region of type opposite to the type of said first semiconducting region.
A method for fabricating a buried reflective layer in silicon adapted for at least one frequency of light, comprising the steps of:
- providing a first body of silicon having a layer of silicon dioxide on a surface thereof;
- providing a second body of silicon;
- implanting hydrogen atoms to a predetermined depth in said silicon surface forming a boundary between hydrogen implanted silicon and unimplanted silicon on either side thereof;
- bonding a silicon surface of said second body to the silicon dioxide layer of the first body by heating the hydrogen implanted body to promote cleaving or fracturing of regions containing hydrogen from regions not containing hydrogen, said heating step including heating to a cleaving temperature followed by heating to a bond strengthening temperature;
- separating the silicon at the hydrogen boundary thereby exposing a separated surface;
- providing a further body of silicon having a layer of silicon dioxide thereon;
- implanting hydrogen atoms to a predetermined depth in said further body forming a boundary between hydrogen implanted silicon and unimplanted silicon on either side thereof;
- bonding the silicon dioxide layer of said further body to said exposed silicon surface;
- and
- separating the silicon at the hydrogen boundary thereby exposing a separated surface.
Dependencies are inferred from the claim text.