LATERALLY-DOPED MEMS RESONATOR WITH PIEZOELECTRIC LAYER
A semiconductor device includes a first silicon layer with first and second regions of substantially different dopant concentration and a resonant MEMS member formed in the first region. A piezoelectric layer is disposed over the resonant MEMS member and conductive material is disposed over the piezoelectric layer and patterned to form first and second electrodes.
1 . (canceled)
2 . A method of fabricating an integrated circuit without exposing a piezoelectric material layer to a high temperature associated with a drive-in doping process, the integrated circuit having a microelectromechanical systems (MEMS) device, the MEMS device having a body which is free to move or deflect, under influence of the piezoelectric material layer, during operation of the integrated circuit, the method comprising:
processing a layer of crystal silicon, the layer of crystal silicon having a first surface, to define one or more slots or trenches that extend orthogonally into the layer of crystal silicon in a direction, relative to the first surface;
depositing a dopant source material to cover sidewalls within the one or more slots or trenches;
performing the drive-in doping process, including heating the layer of crystal silicon and the deposited dopant source material to the high temperature, so as to cause transfer of a dopant from the dopant source material into the layer of crystal silicon via the sidewalls;
depositing a cap-off material to block ingress into the one or more slots or trenches;
forming the piezoelectric material layer over the first surface and the cap-off material;
removing the cap-off material; and
hermetically sealing a cavity within the integrated circuit, the cavity formed at least in part by the one or more slots or trenches.
3 . The method of claim 2 wherein the method further comprises patterning the piezoelectric material layer prior to hermetically sealing the cavity.
4 . The method of claim 2 wherein the integrated circuit comprises a lid layer, the lid layer having a vent extending through the lid layer, and wherein hermetically-sealing the cavity comprises sputtering a metal material so as to pass into and occlude at least a portion of the vent.
5 . The method of claim 4 wherein the vent comprises at least one right-angle bend which obscures line of sight access between the cavity and an atmospheric environment external to the lid layer.
6 . The method of claim 4 wherein the vent is an etch-release vent, and wherein the method further comprises removing a buried oxide material, through the lid layer and via the vent, to at least partially define the cavity.
7 . The method of claim 2 wherein depositing the dopant source material is also performed so as to cover the first surface, and wherein performing the drive-in doping process is to also cause the transfer of the dopant into the layer of crystal silicon via the first surface.
8 . The method of claim 2 wherein performing the drive-in doping process is performed so as to degenerately-dope the layer of crystal silicon, and to thereby form an electrode of the body, the electrode to perform at least one of actuation of or sensing motion of the body.
9 . The method of claim 2 wherein the piezoelectric material layer comprises at least one of aluminum nitride or lead-zirconium-titanate.
10 . The method of claim 2 wherein the dopant comprises phosphorus.
11 . The method of claim 2 wherein the body is a first MEMS body and wherein the integrated circuit also has a second MEMS body, at least one of the first MEMS body or the second MEMS body being part of a resonator, wherein each of the first MEMS body and the second MEMS body comprises a respective portion of the layer of crystal silicon and wherein performing the drive-in doping process is performed simultaneously with respect to the respective portions, so as to thereby simultaneously dope a portion of each of the first MEMS body and the second MEMS body.
12 . The method of claim 2 wherein the integrated circuit comprises a vent extending through a lid layer and a through-layer via, and wherein hermetically sealing the cavity comprises depositing a material in a manner so as to simultaneously occlude the vent and form part of the through-layer via.
13 . The method of claim 2 wherein the integrated circuit comprises two layers of degenerately-doped crystal silicon and wherein performing the drive-in doping process comprises degenerately-doping at least one of the two layers of degenerately-doped crystal silicon.
14 . The method of claim 13 wherein a first one of the two layers is predominantly single-crystal silicon and a second one of the two layers is predominantly polycrystal silicon.
15 . A method of fabricating an integrated circuit without exposing a piezoelectric material layer to a high temperature associated with a drive-in doping process, the integrated circuit having two microelectromechanical systems (MEMS) devices, including a MEMS resonator having a body which is free to move or deflect, under influence of the piezoelectric material layer, during operation of the integrated circuit, the method comprising:
processing a layer of crystal silicon, the layer of crystal silicon having a first surface, to define one or more slots or trenches that extend orthogonally into the layer of crystal silicon in a direction, relative to the first surface;
depositing a dopant source material to cover sidewalls within the one or more slots or trenches;
performing the drive-in doping process, including heating the layer of crystal silicon and the deposited dopant source material to the high temperature, so as to cause transfer of phosphorus from the dopant source material into the layer of crystal silicon via the sidewalls;
depositing a cap-off material to block ingress into the one or more slots or trenches;
forming the piezoelectric material layer over the first surface and the cap-off material;
removing the cap-off material; and
hermetically sealing a cavity within the integrated circuit, the cavity formed at least in part by the one or more slots or trenches.
16 . The method of claim 15 wherein the MEMS resonator is a first MEMS resonator and wherein the two MEMS devices further include at least one of a temperature sensing device or a second MEMS resonator, the at least one of the temperature sensing device or the second MEMS resonator having a second body, wherein each of the body of the first MEMS resonator and the second body comprises a respective portion of the layer of crystal silicon and wherein performing the drive-in doping process is performed simultaneously with respect to the respective portions, so as to thereby simultaneously dope a portion of each of the body of the first MEMS resonator and the second body.
17 . The method of claim 16 wherein the method further comprises doping the respective portions so as to have different concentrations of phosphorus dopant, such that a resultant phosphorus dopant concentration of a first one of the respective portions is at least ten times greater than a resultant phosphorus dopant concentration of a second one of the respective portions.
18 . The method of claim 15 wherein depositing the dopant source material is also performed so as to cover the first surface, and wherein performing the drive-in doping process is to also cause the transfer of the dopant into the layer of crystal silicon via the first surface.
19 . The method of claim 15 wherein performing the drive-in doping process is performed so as to degenerately-dope the layer of crystal silicon, and to thereby form an electrode of the body of the MEMS resonator, the electrode to perform at least one of actuation of or sensing motion of the MEMS resonator.
20 . A method of fabricating an integrated circuit without exposing a piezoelectric material layer to a high temperature associated with a drive-in doping process, the integrated circuit having a microelectromechanical systems (MEMS) device, the MEMS device having a body which is free to move or deflect, under influence of the piezoelectric material layer, during operation of the integrated circuit, the method comprising:
processing a layer of single crystal silicon, the layer of single crystal silicon having a first surface, to define one or more slots or trenches that extend orthogonally into the layer of single crystal silicon in a direction, relative to the first surface;
depositing a dopant source material to cover sidewalls within the one or more slots or trenches;
performing the drive-in doping process, including heating the layer of single crystal silicon and the deposited dopant source material to the high temperature, so as to cause transfer of a dopant from the dopant source material into the layer of single crystal silicon via the sidewalls and thereby degenerately-dope the layer of single crystal silicon;
depositing a cap-off material to block ingress into the one or more slots or trenches;
forming the piezoelectric material layer over the first surface and the cap-off material;
removing the cap-off material; and
hermetically sealing a cavity within the integrated circuit, the cavity formed at least in part by the one or more slots or trenches.
21 . The method of claim 20 wherein the piezoelectric material layer directly abuts the layer of single crystal silicon.