The subject matter disclosed herein relates generally to tunable micro-electro-mechanical systems (MEMS) components. More particularly, the subject matter disclosed herein relates to isolation of electrostatic actuators in MEMS devices to reduce or minimize dielectric charging.
In the construction of micro-electro-mechanical systems (MEMS) devices in which electrostatic actuator plates are movable with respect to one another between open and closed states, the actuator plates would become shorted if the MEMS device closed and the actuators came into contact. To prevent actuator contact and shorting, one or both of the actuator electrodes can be covered by a dielectric that has the appropriate thickness to prevent dielectric breakdown. The continuous dielectric provides the appropriate isolation so that shorting and breakdown can be prevented, but significant contact area may be created within high field regions that can charge and thus lead to reduced lifetimes caused by dielectric charging. The contact area can be minimized by breaking the continuous dielectric pattern into discontinuous or isolated dielectric features, isolation features, or isolation bumps, but even these solutions do not fully address the charging issues.
In accordance with this disclosure, devices, systems, and methods for isolation of electrostatic actuators in MEMS devices are provided to reduce or minimize dielectric charging. In one aspect, a tunable component is provided. The tunable component can include a fixed actuator electrode positioned on a substrate, a movable actuator electrode carried on a movable component that is suspended over the substrate, one or more isolation bumps positioned between the fixed actuator electrode and the movable actuator electrode, and a fixed isolation landing that is isolated within a portion of the fixed actuator electrode that is at, near, and/or substantially aligned with each of the one or more isolation bumps. In this arrangement, the movable actuator electrode can be selectively movable toward the fixed actuator electrode, but the one or more isolation bumps can prevent contact between the fixed actuator electrode and the movable actuator electrode, and the fixed isolation landing can inhibit the development of an electric field in the isolation bump.
In another aspect, a method for manufacturing a tunable component can include depositing a fixed actuator electrode on a substrate, defining one or more fixed isolation landing that is isolated within a portion of the fixed actuator electrode, depositing a sacrificial layer over the fixed actuator electrode, forming a recess into the sacrificial layer that is at, near, and/or substantially aligned with the one or more fixed isolation landing, depositing an isolation bump in each of the one or more recess, depositing a movable actuator electrode over the sacrificial layer, and removing the sacrificial layer to release the movable actuator electrode, wherein the movable actuator electrode is selectively movable toward the fixed actuator electrode.
Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.
The features and advantages of the present subject matter will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which:
The present subject matter provides improved isolation of electrostatic actuators in MEMS devices to reduce or minimize dielectric charging. In one aspect, the present subject matter provides configurations for actuator electrodes that provide isolation of electric fields in a region at, near, and/or substantially aligned with an isolation bump that maintains a desired minimum spacing between two actuator electrodes.
In particular, for example, in some configurations for a MEMS tunable device, an array of individual tunable components is provided. As shown in
In some embodiments, such a structure can be formed by a layer-by-layer deposition process in which fixed actuator electrode 110 is deposited on substrate S, a sacrificial layer is deposited over fixed actuator electrode 110, movable actuator electrode 130 and the other elements of movable component MC are deposited over the sacrificial layer, and the sacrificial layer is removed (e.g., by etching) to release movable component MC. In this arrangement, movable component MC can be moved with respect to the fixed elements and substrate S by controlling the potentials applied to fixed actuator electrode 110 and to movable actuator electrode 130. In some embodiments, for example, movable actuator electrode 130 can be connected to a ground potential and fixed actuator electrode 110 can be connected to a high voltage to cause an electrostatic attraction between the actuator electrodes to cause movable component MC to deflect towards substrate S.
In some embodiments, the fixed and moving electrodes (i.e., one or more of fixed actuator electrode 110, fixed capacitor electrode 120, movable actuator electrode 130, and/or movable capacitor electrode 140) are encapsulated by one or more dielectric material layers to remove or at least reduce the possibility of direct electrical shorting between electrodes during operation (e.g., when movable component MC is deflected to a “closed” position in which the gap between the electrodes is minimized). Even in such arrangements, however, the large area of contact between the actuator elements can lead to excessive dielectric charging and result in large forces, which can affect operation and reliability.
Accordingly, in some embodiments, one or more isolation bump 150 can be provided between respective fixed and movable electrodes (e.g., between fixed actuator electrode 110 and movable actuator electrode 130) to help minimize the contact area and reduce the electric field over much of the actuator area. Referring again to the exemplary layer-by-layer deposition process discussed above, one or more isolation bump 150 can be formed by forming a recess into the sacrificial layer deposited over substrate S and depositing an isolation bump in each of the one or more recess. Such isolation bumps can be implemented in any of a variety of particular shapes (e.g., rectangular prism, octagonal prism) or configurations to optimize mechanical operation and reliability of the device.
In some embodiments, for example, tall isolation bumps (e.g., having a height of about 0.5 μm) located further from a center of the capacitor elements can provide comparatively greater isolation over the entire length of the actuator area, provide mechanical stability, and limit actuator excursion and thus induced material stress. Alternatively or in addition, short isolation bumps (e.g., having a height of about 0.2 μm) can be provided elsewhere in the actuator area to prevent local actuator contact or collapse, particularly near the capacitor region. In some particular configurations, shorter isolation bumps can be distributed either uniformly across the actuator area or in optimal, discrete locations. The optimal number and placement of these isolation bumps for a MEMS capacitor can be determined from the minimum required to achieve stable capacitance; to achieve a flat CV response above pull-in, including minimizing the likelihood of primary/secondary actuator collapse between the actuator and the capacitor or primary actuator collapse between the major isolation bumps and the beam tip; and/or to minimize the increase in the pull-in voltage. Increasing the height of the isolation bumps also works to minimize any field generated charge, but the bump height is limited by the need to maintain sufficient forces in the down state to provide stable capacitance. These and other exemplary configurations for such isolation bumps are discussed in more detail in U.S. Pat. No. 6,876,482 and co-pending U.S. patent application Ser. No. 14/033,434, the disclosures of which are incorporated herein in their entireties.
Regardless of the particular arrangement, one or more isolation bump 150 can be designed to occupy a minimal area with respect to the nearby electrodes, to be minimal in number, and/or to have such a height to minimize electric fields with in the context of other functional requirements. To further improve the effects of the electric fields in the region around isolation bump 150, portions of the field-inducing electrodes can be removed from the region around isolation bump 150. In one particular configuration illustrated in
In the portion of movable actuator electrode 130 at or around the point at which isolation bump 150 is attached (e.g., above isolation bump 150 in the orientation shown in
In a particular exemplary configuration, for instance, isolation bump 150 can have an effective diameter of approximately 0.4 μm and a height of approximately 250 nm, and fixed isolation landing 112 can have substantially rectangular dimensions within fixed actuator electrode 110 with dimensions of about 2.1 μm×1.5 μm. In some embodiments, the spacing between fixed actuator electrode 110 and fixed isolation landing 112 is approximately 1 μm. Isolation bump 150 can be substantially centered within fixed isolation landing 112, or it can be offset with respect to a center of fixed isolation landing 112.
In another particular exemplary configuration, a larger embodiment of isolation bump 150 can have an effective diameter of approximately 0.6 μm and a height of approximately 550 nm compared to fixed isolation landing 112 having dimensions of about 7.7 μm×7 μm.
Described herein are various ranges for the dimensions of some of the components in
Alternatively, in some embodiments, the first distance A is between, and including, about 1 and 10 times the height H (described hereinbelow) of a respective isolation bump 150. For example and without limitation, the first distance A is about 2 times greater than the height H of the respective isolation bump 150. In some embodiments, all of the isolation bumps 150 can have the same or different dimensions. In any event, the dimension of the first distance A as well as the other dimensions discussed herein are chosen to minimize the electric charge build-up where the isolation bump 150 contacts the isolation landing 112. As described herein, the distance A′ will be the length B of the isolation landing 112 minus the diameter D of the isolation bump 150 and the length of the first distance A. The possible values of the length B of the isolation landing 112 minus the diameter D of the isolation bump 150 are described herein.
The GAP is defined as the distance between the movable electrode 130 (including any surface materials shown in other figures herein) and the fixed electrode 110. In some embodiments, the dimension of the GAP is equal to or greater than the height H of the isolation bump 150 as defined below. The dimension of the GAP is further limited by the maximum MEMS opening distance. In other words, the maximum dimension of the GAP is the distance between the movable electrode 130 (including any surface materials shown in other figures herein) and the fixed electrode 110 when the MEMS device is in a fully “OPEN” position. In some embodiments, the dimension of the GAP can range between, and including, about 0.5 microns and 5 microns. More particularly, in some embodiments, the dimension of the GAP can range between, and including, about 1 and 2 microns.
As described herein, in some embodiments, the isolation bump 150 can have a height H and a diameter D, the height H being defined as the length in which the isolation bump 150 extends into the GAP, and the diameter D being defined as the dimension of the isolation bump 150 measured in a direction perpendicular to the measurement of the height H of the isolation bump 150. In some embodiments, the height H of the isolation bump 150 can range between, and including, about 1% and 30% of the GAP dimension when the MEMS device is in a fully “OPEN” position. For example and without limitation, in some embodiments, the height H can be between, and including, about 0.005 and 1.5 microns. In some alternative embodiments in particular, the height H of the isolation bump 150 can be about 20% of the GAP, or about 0.2 to 0.4 microns. In some further embodiments, the diameter D can range between, and including, about 1 to 10 times the height H. In some embodiments, the diameter D can be between, and including, about 0.005 and 15 microns. More particularly, in some embodiments, the diameter D can be between, and including, about 0.2 to 4 microns.
Those having ordinary skill in the art can appreciate that the length B of the isolation landing 112 can range based on the dimensions of the first distance A, the diameter D of the bump 150, and where the isolation bump 150 lands on the isolation landing 112. For example and without limitation, if the isolation bump 150 lands in the middle of the isolation landing 112, the length B of the isolation landing 112 is equal to 2*A+D as defined above. In the instance where the isolation bump 150 does not land directly in the center of the isolation landing 112, the length B of the isolation landing 112 is equal to A+A′+D, where the first distance A is, again, the shortest distance from the edge of the isolation bump 150 and the edge of the isolation landing 112 and the distance A′ is the distance on the opposite side of the isolation bump 150 as the first distance A. In some embodiments, the length B of the fixed isolation landing 112 can be between, and including, 0.015 micron and 45 microns. To obtain this range, assume two hypotheticals: a low range hypothetical and a high range hypothetical.
Both hypotheticals assume that the isolation bump 150 lands directly in the center of the isolation landing 112, in which case the length B of the isolation landing 112 is B=2*A+D. As described above, both the diameter of the isolation bump 150 and the first distance A can be between and including 1-10 times the height H of the bump 150. The height H of the bump 150 can be between, and including, about 0.005 and 1.5 microns. Therefore, on the low-end hypothetical, B=2*(0.005)+0.005 microns which is equal to 0.015 microns. On the high-end hypothetical, the same assumptions are made, except that B=2*(15)+15 microns, which is equal to 45 microns. In particular, in some embodiments, the fixed isolation landing 112 can have a length B that is between, and including, about 2 μm and 21 μm.
In embodiments where the isolation bump 150 lands away from the center of the isolation landing 112, the length B would still range in the measurements described above, however, the first length A would be smaller and the length A′ on the opposite side of the isolation bump 150 would be greater than the first length A. In such embodiments, the length A′ would be greater than or equal to the ranges of lengths described above for the first length A.
In some embodiments, the second distance S is the spacing between fixed actuator electrode 110 and the fixed isolation landing 112. In some embodiments, the second distance S can range between, and including, about 1 and 10 times the height H of the isolation bump 150. Similarly to the first length A and A′ described above, both spacings on either side of the isolation landing 112 may have slightly different lengths, depending on the manufacturing process for the MEMs device. Therefore the second length S could be the same on both sides of the isolation landing 112, or there could be a second length S and S′ scenario where the second length S is nominally different than the length S′ on the other side of the isolation landing 112.
Moreover, in some embodiments, all of the isolation bumps 150 have the same dimensions and are identical in shape and size. In other embodiments, each of the isolation bumps 150 are different in size and shape from one another according to design requirements. In some other embodiments, different groups of the isolation bumps 150 can have the same dimensions. For example, as a hypothetical, if there were 10 isolation bumps, there could be four separate groups, 1, 2, 3, and 4. All of the bumps in group 1 could have the same size and shape all of the bumps in group 2 could have the same size and shape, and so on. However, this is a hypothetical. There could be any number of different groups or there could be just one or two.
In an alternative configuration shown in
In yet further exemplary configurations illustrated in
Still further exemplary configurations are shown in
In yet a further alternative configuration,
In another alternative configuration,
In any of these arrangements, those having skill in the art will appreciate that the configuration of the electrode portions that are at, near, or substantially in alignment with isolation bump 150 can affect the ability for a charge to develop through isolation bump 150 between the electrodes. In particular, for example, fixed isolation landing 112 can be electrically isolated (“floating”), connected to a ground potential, or connected to a selected electrical potential that is the same as or different than the potential connected to the movable actuator electrode 130. As shown in
It should be noted that the voltage contour graphs for
Similarly, the electric field that is developed at the center of isolation bump 150 can vary depending on the configuration of movable actuator electrode 130 (e.g., having a hole at or near isolation bump 150, as a conformal layer, or having a movable isolation fill 132) and the configuration of fixed actuator electrode 110 (e.g., having fixed isolation landing 112 defined therein). In the particular configurations shown, for example, the electric fields developed with a grounded fixed isolation landing 112 (See, e.g.,
The present subject matter can be embodied in other forms without departure from the spirit and essential characteristics thereof. The embodiments described therefore are to be considered in all respects as illustrative and not restrictive. Although the present subject matter has been described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of the present subject matter.
The present application is a continuation patent application of and claims priority to U.S. application Ser. No. 14/875,341, filed Oct. 5, 2015, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/059,822, filed Oct. 3, 2014, the disclosures of which are incorporated herein by reference in their entireties.
Number | Date | Country | |
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62059822 | Oct 2014 | US |
Number | Date | Country | |
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Parent | 14875341 | Oct 2015 | US |
Child | 17234108 | US |