Techniques for adding compensating material(s) in semiconductor devices
A resonant member of a MEMS resonator oscillates in a mechanical resonance mode that produces non-uniform regional stresses such that a first level of mechanical stress in a first region of the resonant member is higher than a second level of mechanical stress in a second region of the resonant member. A plurality of openings within a surface of the resonant member are disposed more densely within the first region than the second region and at least partly filled with a compensating material that reduces temperature dependence of the resonant frequency corresponding to the mechanical resonance mode.
1. A semiconductor device comprising:
a body;
the body having one or more layers of semiconductor material collectively presenting a first value of a temperature-dependent parameter;
a trench or a slot defined within an opening in a planar surface presented by at least one layer of the one or more layers of the semiconductor material;
one or more compensating materials substantially filling the trench or slot, the one or more compensating materials collectively presenting a second value of the temperature-dependent parameter;
the body having a temperature-dependent characteristic dependent on each of the first value and the second value;
the semiconductor device being manufactured according to a fabrication process that produces an outer surface of the one or more compensating materials within the trench or slot wherein the outer surface is substantially coplanar with the planar surface; and
a continuous layer of conductive material deposited over the one or more layers and the one or more compensating materials within the trench, so as to cap the one or more compensating materials within the trench or slot;
wherein:
the body defines a beam having a swinging end which is operable to deflect or move during operation of the semiconductor device; and
the swinging end is substantially encased in the conductive material.
2. The semiconductor device of claim 1 wherein:
the one or more compensating materials comprise an oxide and the continuous layer comprises silicon nitride.
3. The semiconductor device of claim 1 wherein:
the temperature-dependent parameter is a function of a temperature coefficient of Young's modulus (TCE) and the temperature dependent-characteristic is dependent on an overall stiffness of the body.
4. The semiconductor device of claim 1 wherein:
the one or more compensating materials comprise an oxide; and
the fabrication process is a self-limiting oxide-growth process, in which oxide growth is pinched off as oxide in the trench or slot becomes substantially coplanar with the planar surface during the growth process.
5. The semiconductor device of claim 1 wherein:
the first value and the second value have opposite signs for at least one temperature.
6. The semiconductor device of claim 1 wherein the one or more compensating materials are hermetically sealed within the body.
7. A semiconductor device comprising:
a body;
the body having one or more layers of semiconductor material collectively presenting a first value of a temperature-dependent parameter;
a trench or a slot defined within an opening in a planar surface presented by at least one layer of the one or more layers of the semiconductor material;
one or more compensating materials substantially filling the trench or slot, the one or more compensating materials collectively presenting a second value of the temperature-dependent parameter;
the body having a temperature-dependent characteristic dependent on each of the first value and the second value;
the semiconductor device being manufactured according to a fabrication process that produces an outer surface of the one or more compensating materials within the trench or slot wherein the outer surface is substantially coplanar with the planar surface; and
a continuous layer of conductive material deposited over the one or more layers and the one or more compensating materials within the trench, so as to cap the one or more compensating materials within the trench or slot;
wherein:
the semiconductor device comprises a resonator;
the body comprises a first beam and a second being that are configured to vibrate, during operation of the resonator;
the trench or slot is a first trench or slot, and is defined in the first beam;
the second beam comprises a second trench or a slot, defined within at least one layer of the one or more layers of the semiconductor material of the second body, the second beam also having the one or more compensating materials in a manner which substantially fill the second trench or slot; and
the temperature-dependent characteristic is also dependent on a value of the temperature-dependent parameter for the one or more compensating materials which substantially fill the second trench or slot.
8. The semiconductor device of claim 7 wherein:
the first beam and the second beam each have a first end and a swinging end, and extend along a respective length dimension, each of the first beam and the second beam also having a second dimension that is perpendicular to the respective length dimension, the swinging end of each beam to vibrate in the second dimension during operation of the MEMS resonator and
the body comprises a base portion mechanically coupling the anchor and the first end of each of the first beam and the second beam; and
the one or more layers of semiconductor materials comprises a layer of crystal silicon.
9. The MEMS device of claim 8 wherein the one or more compensating materials comprise a continuous material region in each of the first beam and the second beam, the continuous material region extending along the length dimension in a manner spanning no more than thirty percent of the length of the respective beam along the respective length dimension.
10. The semiconductor device of claim 7 wherein:
the body defines a beam having a swinging end which is operable to deflect or move during operation of the semiconductor device; and
the swinging end is substantially encased in the conductive material.
11. A semiconductor device comprising:
a microelectromechanical systems (MEMS) structure having a body that is to vibrate or deflect during operation of the semiconductor device;
the body having one or more layers of semiconductor material collectively presenting a first value of parameter dependent on a temperature coefficient of Young's Modulus (TCE);
a trench or a slot defined within an opening in a planar surface presented by at least one layer of the one or more layers of the semiconductor material;
one or more compensating materials substantially filling the trench or slot, the one or more compensating materials collectively presenting a second value of the TCE-dependent parameter;
the body having an overall temperature coefficient of frequency (TCF) that is dependent on each of the first value and the second value;
the semiconductor device being manufactured according to a fabrication process that produces an outer surface of the one or more compensating materials within the trench or slot wherein the outer surface is substantially coplanar with the planar surface; and
a continuous layer of conductive material deposited over the one or more layers and the one or more compensating materials within the trench, so as to cap the one or more compensating materials within the trench or slot;
wherein:
the body defines a beam having a swinging end which is operable to deflect or move during operation of the semiconductor device; and
the swinging end is substantially encased in the conductive material.
12. The semiconductor device of claim 11 wherein:
the one or more compensating materials comprise an oxide and the continuous layer comprises silicon nitride.
13. The semiconductor device of claim 11 wherein:
the one or more compensating materials comprise an oxide; and
the fabrication process is a self-limiting oxide-growth process, in which oxide growth is pinched off as oxide in the trench or slot becomes substantially coplanar with the planar surface during the growth process.
14. The semiconductor device of claim 11 wherein:
the first value and the second value have opposite signs for at least one temperature.
15. The semiconductor device of claim 11 wherein the one or more compensating materials are hermetically sealed within the body.
16. A semiconductor device comprising:
a microelectromechanical systems (MEMS) structure having a body that is to vibrate or deflect during operation of the semiconductor device;
the body having one or more layers of semiconductor material collectively presenting a first value of parameter dependent on a temperature coefficient of Young's Modulus (TCE);
a trench or a slot defined within an opening in a planar surface presented by at least one layer of the one or more layers of the semiconductor material;
one or more compensating materials substantially filling the trench or slot, the one or more compensating materials collectively presenting a second value of the TCE-dependent parameter;
the body having an overall temperature coefficient of frequency (TCF) that is dependent on each of the first value and the second value;
the semiconductor device being manufactured according to a fabrication process that produces an outer surface of the one or more compensating materials within the trench or slot wherein the outer surface is substantially coplanar with the planar surface; and
a continuous layer of conductive material deposited over the one or more layers and the one or more compensating materials within the trench, so as to cap the one or more compensating materials within the trench or slot
wherein:
the semiconductor device comprises a resonator;
the body comprises a first beam and a second being that are configured to vibrate, during operation of the resonator;
the trench or slot is a first trench or slot, and is defined in the first beam;
the second beam comprises a second trench or a slot, defined within at least one layer of the one or more layers of the semiconductor material of the second body, the second beam also having the one or more compensating materials which substantially fill the second trench or slot; and
the temperature-dependent characteristic is also dependent on a value of the temperature-dependent parameter for the one or more compensating materials which substantially fill the second trench or slot.
17. The semiconductor device of claim 15 wherein:
the first beam and the second beam each have a first end and a swinging end, and extend along a respective length dimension, each of the first beam and the second beam also having a second dimension that is perpendicular to the respective length dimension, the swinging end of each beam to vibrate in the second dimension during operation of the MEMS resonator and
the body comprises a base portion mechanically coupling the anchor and the first end of each of the first beam and the second beam; and
the one or more layers of semiconductor materials comprises a layer of crystal silicon.
18. The MEMS device of claim 17 wherein the one or more compensating materials comprises a continuous material region in each of the first beam and the second beam, the continuous material region extending along the respective length dimension in a manner spanning no more than thirty percent of the length of the respective beam along the respective length dimension.
19. An integrated circuit comprising:
a timing signal generator having a microelectromechanical systems (MEMS) resonator, the MEMS resonator having a body that is to vibrate at a resonant frequency during operation of the integrated circuit;
the body comprising at least two beams and an anchor;
each of the beams having one or more layers of semiconductor material collectively presenting a first value of a coefficient of Young's Modulus (TCE);
for each of the beams:
a trench or a slot defined within an opening in a planar surface presented by at least one layer of the one or more layers of the semiconductor material; and
one or more compensating materials deposited to fill the trench or slot, the one or more compensating materials collectively presenting a second value of the TCE;
the body having a temperature-dependent characteristic dependent on each of the first value and the second value of each of the beams; and
circuitry to output a timing signal dependent on a sensed resonant frequency of vibration of the MEMS resonator;
an outer surface of the one or more compensating materials within each trench or slot that is substantially coplanar with the planar surface of the respective trench or slot; and
a continuous layer of conductive material deposited over the one or more layers and the one or more compensating materials within the trench, so as to cap the one or more compensating materials within the trench or slot.
20. The integrated circuit of claim 19 wherein:
the first value and the second value have opposite signs for at least one temperature.
21. The integrated circuit of claim 19 wherein:
the integrated circuit comprises a resonator;
the body comprises a first beam and a second being that are configured to vibrate, during operation of the resonator;
the trench or slot is a first trench or slot, and is defined in the first beam;
the second beam comprises a second trench or a slot, defined within at least one layer of the one or more layers of the semiconductor material of the second body, the second beam also having the one or more compensating materials which substantially fill the second trench or slot; and
the temperature-dependent characteristic is also dependent on a value of the temperature-dependent parameter for the one or more compensating materials which substantially fill the second trench or slot.