Method of fabricating a micro-electromechanical device with a thermal actuator
View Patent ↗A method of fabricating a micro-electromechanical device includes the step of forming electrical connections to drive circuitry on a wafer substrate. A first sacrificial structure is formed on the wafer substrate. The first sacrificial structure corresponds at least to a mechanical arm to be formed on the sacrificial structure, spaced from the wafer substrate. At least the mechanical arm is formed on the sacrificial structure. A second sacrificial structure is formed on the wafer substrate such that the second sacrificial structure corresponds at least to a heater element to be connected to the electrical connections, isolated from and overlying the mechanical arm. The heater element is formed on the second sacrificial structure. A third sacrificial structure is formed on the wafer substrate such that the third sacrificial structure corresponds at least to a structural formation that serves to fasten the heater element to the mechanical arm at a position spaced from the electrical connections such that resistive heating and subsequent cooling of the heater element as a result of an electrical current passing through the heater element results in displacement of the structural formation relative to the substrate. The structural formation is formed on the wafer substrate.
1. A method of fabricating a micro-electromechanical device, the method comprising the steps of:
forming electrical connections to drive circuitry on a wafer substrate;
forming a first sacrificial structure on the wafer substrate that corresponds at least to a mechanical arm to be formed on the sacrificial structure, spaced from the wafer substrate;
forming at least the mechanical arm on the sacrificial structure;
forming a second sacrificial structure on the wafer substrate such that the second sacrificial structure corresponds at least to a heater element to be connected to the electrical connections, isolated from and overlying the mechanical arm;
forming the heater element on the second sacrificial structure;
forming a third sacrificial structure on the wafer substrate such that the third sacrificial structure corresponds at least to a structural formation that serves to fasten the heater element to the mechanical arm at a position spaced from the electrical connections such that resistive heating and subsequent cooling of the heater element as a result of an electrical current passing through the heater element results in displacement of the structural formation relative to the substrate; and
forming the structural formation on the wafer substrate.
2. A method as claimed in claim 1 , in which the step of forming the electrical connections to the drive circuitry includes the step of forming bond pads on the wafer substrate.
3. A method as claimed in claim 1 , in which the step of forming the first sacrificial structure includes the step of forming first and second layers of sacrificial material on the wafer substrate.
4. A method as claimed in claim 1 , in which the steps of forming the heater element and the mechanical arm include the steps of depositing and etching a multi-layer ceramic material.
5. A method as claimed in claim 4 , in which the steps of forming the heater element and the mechanical arm include the steps of depositing and etching a material selected from the group comprising: Titanium Nitride, Titanium Boride, Molybdenum Disilicide and Titanium-Aluminum-Nitride.
6. A method as claimed in claim 5 , in which the steps of forming the heater element and the mechanical arm include the steps of depositing a first layer of a material selected from said group, a second layer of a further ceramic, a third layer of the material selected from said group, a fourth layer of said further ceramic and a fifth layer of the material selected from said group.
7. A method as claimed in claim 6 , in which the steps of depositing the second and fourth layers include the steps of depositing tantalum nitride.