Electromechanical transducer device and method of forming a electromechanical transducer device
View Patent ↗A micro or nano electromechanical transducer device formed on a semiconductor substrate comprises a movable structure which is arranged to be movable in response to actuation of an actuating structure. The movable structure comprises a mechanical structure having at least one mechanical layer having a first thermal response characteristic, at least one layer of the actuating structure having a second thermal response characteristic different to the first thermal response characteristic, and a thermal compensation structure having at least one thermal compensation layer. The thermal compensation layer is different to the at least one layer and is arranged to compensate a thermal effect produced by the mechanical layer and the at least one layer of the actuating structure such that the movement of the movable structure is substantially independent of variations in temperature.
1. A micro or nano electromechanical transducer device formed on a semiconductor substrate comprising:
a movable structure being arranged to be movable in response to actuation of an actuating structure and comprising:
a mechanical structure having at least one mechanical layer having a first thermal response characteristic;
at least one layer of the actuating structure, the at least one layer having a second thermal response characteristic different to the first thermal response characteristic; and
a thermal compensation structure having at least one thermal compensation layer being different to the at least one layer of the actuating structure, and wherein the thermal compensation structure is arranged to compensate a thermal effect produced by the mechanical structure and the at least one layer of the actuating structure such that movement of the movable structure is substantially independent of variations in temperature;
wherein the actuating structure includes a plurality of layers including a magnetic layer and the plurality of layers form part of the movable structure, the movable structure being movable in response to magnetic actuation plurality of layers.
2. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure comprises less layers than the actuating structure.
3. The micro or nano electromechanical transducer device of claim 1 , wherein the plurality of layers includes a magnetic layer between first and second electrode layers.
4. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure comprises one or two layers only.
5. The micro or nano electromechanical transducer device of claim 1 , wherein the at least one layer of the actuating structure is formed of a first material and the thermal compensation structure comprises a layer formed of a compensation material different to the first material.
6. The micro or nano electromechanical transducer device of claim 1 , further comprising a substrate and wherein the actuating structure further comprises a layer formed on the substrate.
7. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure is adjacent the mechanical layer.
8. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure is formed of compensation material selected according to the Coefficient of Thermal Expansion and Young's modulus of the compensation material and has a predetermined thickness in order to compensate the thermal effect.
9. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure has a third thermal response characteristic and is formed from at least a compensation material, and wherein the third thermal response characteristic depends on the Coefficient of Thermal Expansion of the compensation material.
10. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure has substantially the same Coefficient of Thermal Expansion as the at least one layer of the actuating structure.
11. The micro or nano electromechanical transducer device of claim 1 , wherein the thermal compensation structure and the at least one layer of the actuating structure forming part of the movable structure are formed on opposite sides of the mechanical structure.
12. The micro or nano electromechanical transducer device of claim 1 , wherein the at least one layer of the actuating structure forming part of the movable structure occupies a first area in a plane substantially parallel to the mechanical structure and wherein the thermal compensation structure occupies a second area in a plane substantially parallel to the mechanical structure, wherein the second area is substantially the same as the first area.
13. The micro or nano electromechanical transducer device of claim 1 , further comprising a semiconductor substrate and an anchor formed on the semiconductor substrate for supporting the movable structure, wherein the movable structure has at least one unsupported end.
14. The micro or nano electromechanical transducer device of claim 1 , further comprising a semiconductor substrate and anchors formed on the semiconductor substrate for supporting the movable structure at ends of the movable structure, wherein the at least one layer of the actuating structure and the at least one thermal compensation layer are on a portion of the movable structure.
15. The micro or nano electromechanical transducer device of claim 8 , wherein the predetermined thickness of the compensation layer is obtained by solving the following equation:
∑
i
∑
j
>
i
d
ij
·
E
i
·
E
j
·
t
i
·
t
j
(
α
i
-
α
j
)
·
z
ij
·
Δ
T
0
=
0
Where: Ei is the Young's modulus of layer i;
ti is the thickness of layer i;
ai is the CTE of layer i;
dij is the distance between layers i and j, measured from the middle of the layers; and
zij is equal to 1 when layer j is above layer i and equals to −1 when layer j is below layer i.
16. A method of forming a micro or nano electromechanical transducer device on a semiconductor substrate comprising a movable structure being arranged to be movable in response to actuation of an actuating structure, the method comprising forming the movable structure by;
providing a mechanical structure having at least one mechanical layer having a first thermal response characteristic;
providing at least one layer of the actuating structure, the at least one layer having a second thermal response characteristic different to the first thermal response characteristic; and
providing a thermal compensation structure having at least one thermal compensation layer being different to the at least one layer of the actuating structure and being arranged to compensate a thermal effect produced by the mechanical structure and the at least one layer of the actuating structure such that the movement of the movable structure is substantially independent of variations in temperature;
wherein the actuating structure includes a plurality of layers including a plurality of piezoelectric layers, and the plurality of layers form part of the movable structure, the movable structure being movable in response to piezoelectric actuation of the plurality of layers.
17. The method of claim 16 , further comprising further comprising selecting a material for the thermal compensation structure according to the Coefficient of Thermal Expansion and Young's modulus of the material, and arranging for the thermal compensation structure to have a predetermined thickness in order to compensate the thermal effect.
18. The method of claim 16 , wherein the predetermined thickness of the compensation layer is obtained by solving the following equation:
∑
i
∑
j
>
i
d
ij
·
E
i
·
E
j
·
t
i
·
t
j
(
α
i
-
α
j
)
·
z
ij
·
Δ
T
0
=
0
Where: Ei is the Young's modulus of layer i;
ti is the thickness of layer i;
ai is the CTE of layer i;
dij is the distance between layers i and j, measured from the middle of the layers; and
zij is equal to 1 when layer j is above layer i and equals to −1 when layer j is below layer i.