Micro-electro-mechanical system (MEMS) variable capacitor apparatuses and related methods
Systems, devices, and methods for micro-electro-mechanical system (MEMS) tunable capacitors can include a fixed actuation electrode attached to a substrate, a fixed capacitive electrode attached to the substrate, and a movable component positioned above the substrate and movable with respect to the fixed actuation electrode and the fixed capacitive electrode. The movable component can include a movable actuation electrode positioned above the fixed actuation electrode and a movable capacitive electrode positioned above the fixed capacitive electrode. At least a portion of the movable capacitive electrode can be spaced apart from the fixed capacitive electrode by a first gap, and the movable actuation electrode can be spaced apart from the fixed actuation electrode by a second gap that is larger than the first gap.
1. A method for manufacturing a micro-electro-mechanical system (MEMS) variable capacitor, the method comprising:
depositing a fixed actuation electrode on a substrate;
depositing a fixed capacitive electrode on the substrate;
depositing a sacrificial layer over the fixed actuation electrode and the fixed capacitive electrode;
etching the sacrificial layer to form a recess in a region of the sacrificial layer above the fixed capacitive electrode;
depositing a movable actuation electrode on the sacrificial layer above the fixed actuation electrode;
depositing a movable capacitive electrode in the recess of the sacrificial layer above the fixed capacitive electrode;
depositing a structural material layer on the movable actuation electrode and the movable capacitive electrode; and
removing the sacrificial layer such that the movable actuation electrode, the movable capacitive electrode, and the structural material layer define a movable component suspended above the substrate and movable with respect to the fixed actuation electrode and the fixed capacitive electrode;
wherein at least a portion of the movable capacitive electrode is spaced apart from the fixed capacitive electrode by a first gap;
wherein the movable actuation electrode is spaced apart from the fixed actuation electrode by a second gap that is larger than the first gap; and
wherein a difference between a dimension of the first gap and a dimension of the second gap is less than or equal to one quarter of the dimension of the second gap.
2. The method of claim 1 , wherein the difference between the dimension of the first gap and the dimension of the second gap is between 10 nm and 500 nm.
3. The method of claim 1 , comprising depositing a layer of dielectric material on the substrate prior to depositing a fixed capacitive electrode such that the fixed capacitive electrode is elevated relative to the fixed actuation electrode.
4. The method of claim 1 , comprising:
further etching the sacrificial layer further to form one or more recesses above the fixed actuation electrode; and
depositing one or more standoff bump in the one or more recesses above the fixed actuation electrode;
wherein the at least one standoff bump extends between the fixed actuation electrode and the movable actuation electrode a distance that is substantially equal to the difference between the dimension of the first gap and the dimension of the second gap.
5. The method of claim 4 , wherein depositing one or more standoff bump comprises depositing a layer of dielectric material over the sacrificial layer, including in the one or more recesses above the fixed actuation electrode.