Capacitively controlled fabry-perot interferometer

Abstract

This disclosure describes a capacitively controlled Fabry-Perot interferometer, comprising: a first mirror layer having a first metal thin film layer embedded in a first insulating layer; and a second mirror layer having a second metal thin film layer embedded in a second insulating layer. Control regions in the first metal thin film layer and control regions in the second metal thin film layer are at least partially aligned in an actuation direction. The interferometer also includes a first control electrode and a first dielectric layer, the first dielectric layer being located between the first control electrode and at least a portion of the control regions of the first metal thin film layer.

Description

Technical Field

[0001] This disclosure relates to Fabry-Perot optical filters, and more particularly to micromechanical Fabry-Perot interferometers. This disclosure further relates to a mechanism by which the gap between the top and bottom mirrors can be controlled. Background Technology

[0002] Micromechanical Fabry-Perot interferometers typically include a top mirror suspended above a bottom mirror over a substrate. These two mirrors are separated from each other by a mirror gap to form an optical tuning cavity between them. At least a portion of each mirror is transparent. Incident electromagnetic radiation can enter the tuning cavity from one side and exit from the other.

[0003] Light entering the optical cavity undergoes multiple reflections between the bottom and top mirrors before exiting. This constructive interference produces a transmission peak at wavelengths corresponding to the formula 2d = nλ, where d is the height of the mirror gap and n is an integer. When n is greater than 1, the first-order transmission peak corresponding to n=1 will be accompanied by higher-order transmission peaks from wavelengths that satisfy the formula. An order-ordering filter can be implemented using a Fabry-Perot filter to allow transmission only at wavelengths corresponding to a specific value of n.

[0004] Micromechanical Fabry-Perot interferometers can be arranged to filter electromagnetic radiation in a wavelength range extending from the visible to the infrared. The transmitted wavelength can be selected by adjusting the mirror gap. Some microelectromechanical Fabry-Perot filters utilize MEMS actuators to move one mirror relative to another, thereby adjusting the mirror gap. US document 2009153844 discloses a MEMS Fabry-Perot filter in which an electrostatic actuator is connected to a mirror. One problem with this actuation mechanism is that the actuator consumes a large surface area and requires many additional fabrication steps. Summary of the Invention

[0005] One object of this disclosure is to provide an apparatus for overcoming the above-mentioned problems.

[0006] The purpose of this disclosure is to achieve this through a device.

[0007] This disclosure is based on the idea of ​​actuating the relative movement between a bottom mirror and a top mirror using the direct electrostatic attraction between the two mirrors. The electromotive force of at least one of the two mirrors is set via a capacitively coupled control electrode. One advantage of this device is that the mirror gap can be adjusted with high precision over a wide range. Attached Figure Description

[0008] In the following, the present disclosure will be described in more detail with reference to the preferred embodiments shown in the accompanying drawings, wherein:

[0009] Figure 1a A capacitor-controlled Fabry-Perot interferometer is shown.

[0010] Figure 1b The annular control region on the xy plane is shown.

[0011] Figure 1c It shows Figure 1a The equivalent circuit of the device shown.

[0012] Figure 1d A device is shown in which a control electrode is in direct electrical contact with a thin metal film layer.

[0013] Figure 2 A device is shown in which a semi-insulating layer can transfer charge between mirror layers.

[0014] Figures 3a to 3g A method for manufacturing a capacitor-controlled Fabry-Perot interferometer is shown. Detailed Implementation

[0015] This disclosure describes a capacitively controlled Fabry-Perot interferometer. The interferometer includes a first mirror layer comprising a first thin metal film layer embedded in a first insulating layer. The first thin metal film layer includes a central region and a control region.

[0016] The interferometer also includes a second mirror layer comprising a second metal thin film layer embedded in a second insulating layer. The second metal thin film layer includes a central region and a control region. The central region of the first metal thin film layer and the central region of the second metal thin film layer are at least partially aligned in the actuation direction. The control region of the first metal thin film layer and the control region of the second metal thin film layer are at least partially aligned in the actuation direction.

[0017] The interferometer also includes a first control electrode and a first dielectric layer. The first dielectric layer is located between at least a portion of the control region of the first control electrode and the first metal thin film layer. The first dielectric layer is a first insulating layer embedded in a portion of the first metal thin film layer. The interferometer also includes a second control electrode electrically coupled to a control region of the second metal thin film layer.

[0018] The first mirror layer can be fixed to the substrate, and the second mirror layer can be suspended above the substrate, making the two mirror layers substantially parallel to each other. The term "actuation direction" refers to the operating direction of the interferometer. Electromagnetic radiation filtered by the interferometer enters and exits the interferometer in the actuation direction. For example, the actuation direction can be substantially perpendicular to the first and second mirror layers and the substrate surface.

[0019] If the plane of the substrate is used to define a horizontal plane, then the actuation direction may be referred to as the vertical direction, and the first mirror layer may be referred to as the bottom mirror and the second mirror layer as the top mirror. However, the terms "top / bottom" or "upper / lower" as used in this disclosure refer only to the orientation during device manufacturing. The device can be oriented in any direction during use, therefore the "actuation direction" is not necessarily vertical when using the device.

[0020] Figure 1a A capacitively controlled Fabry-Perot interferometer with a first mirror layer 11 is shown. The first mirror layer comprises a first metal thin film layer 111 embedded in a first insulating layer 112. Correspondingly, a second mirror layer 12 comprises a second metal thin film layer 121 embedded in a second insulating layer 122. In this configuration, the second mirror layer 12 is situated on a substrate 18, while the first mirror layer 11 is suspended above the substrate by two spacers 141 and 142, thereby forming a tuning cavity 17 between the first and second mirror layers. The substrate 18 may be, for example, a fused silica substrate or a sapphire substrate, or any other suitable substrate, with sufficient transparency to the radiation through which the interferometer is designed to pass.

[0021] The substrate defines the xy plane, in Figure 1a The x-axis represents the direction of actuation. The z-axis represents the direction of actuation, and the height of cavity 17 in the actuation direction is the mirror gap 171. The mirror gap can be adjusted by an actuating force that moves the first mirror layer 11 relative to the second mirror layer 12, as described below.

[0022] Spacing 141 and 142 can be made of oxide layers deposited at relatively low temperatures, such as tetraethyl orthosilicate (TEOS) layers. Alternatively, they can be made of polymer layers. The thickness of such oxide or polymer layers typically determines (and may be equal to) the initial height of the mirror gap 171 before the actuation force is applied. For example, the thickness of the layers forming spacing 141 and 142 can range from 200 nanometers to 4 micrometers. The optimal thickness depends (among other things) on the desired passband wavelength of the interferometer.

[0023] The first metal thin film layer 111 and the second metal thin film layer 121 are conductive and act as reflectors in each mirror layer. Layers 111 and 121 may be, for example, layers of silver, gold, platinum, or titanium. The thickness of the first metal thin film layer 111 and the second metal thin film layer 121 may be between 30 and 50 nanometers, or between 15 and 60 nanometers.

[0024] The insulating layers 112 and 122 embedded in the metal thin film should have sufficiently high tensile stress to flexibly accommodate the bending experienced by the first mirror layer 11 when the actuation force reduces the mirror gap by bringing the first mirror layer 11 closer to the second mirror layer 12. The insulating layers 112 and 122 may be, for example, layers of Al2O3 with a thickness ranging from 5 to 100 nanometers.

[0025] Dashed lines 191 to 196 divide the device into five regions along the x-axis. Both the first mirror layer 11 and the second mirror layer 12 have a central region in regions 191-192. The first mirror layer 11 has a first control region in regions 192-196 and a second control region in regions 191-193. The second mirror layer 12 has a first control region in regions 195-191 and a second control region in regions 192-194. The first and second metal thin film layers have central regions and control regions, which correspond to the central regions and control regions of the first and second mirror layers, respectively.

[0026] The first metal thin film layer 111 and the second metal thin film layer 121 can extend as continuous layers from 193 to 196 and from 195 to 194, respectively. However, it is generally more advantageous to separate the central regions of the metal thin film layers from their control regions. In other words, the first metal thin film layer 111 and the second metal thin film layer 121 can be discontinuous. These layers can be electrically floating in the central portions of regions 191-192, while the control portions located in control regions 193-191 and 192-194 can be configured with specific electromotive forces by control electrodes that are capacitively or ohmically coupled, these control electrodes being in capacitive or direct electrical contact with the control regions.

[0027] Figure 1a The first and second control regions of the first mirror layer 11 shown can be part of a continuous first annular control region. Similarly, the first and second control regions of the second mirror layer 12 can be part of a continuous second annular control region. The second annular control region can be aligned with the first annular control region in the actuation direction.

[0028] Figure 1b A ring-shaped control region on the xy-plane is shown. A first and second ring-shaped control region overlap within this control region. This control region can be donut-shaped. Figure 1a The cross section shown is along Figure 1b The control region is formed by the AA line. When the first mirror is actuated in the actuation direction, the geometry of this control region makes the central region of the first mirror layer 11 parallel to the central region of the second mirror layer 12. The control region may also have other geometries.

[0029] The central region of the first mirror layer 11 can be larger than, or vice versa, the central region of the second mirror layer 12. Then, the first and second annular control regions of the two mirror layers will also have different dimensions. However, the central region of the first mirror layer 11 must be at least partially aligned with the central region of the second mirror layer 12 in the actuation direction, such that they overlap in the xy-plane. The overlapping region of the central regions forms the optically active region of the interferometer. The control region of the first mirror layer is also at least partially aligned with the control region of the second mirror layer in the actuation direction, such that they overlap in the xy-plane. This overlapping region can, for example, have a donut-shaped shape as discussed above, or any other suitable shape.

[0030] The overlapping control regions form the actuation region. When a potential difference exists between the control regions of metal thin film layer 111 and metal thin film layer 121, an electrostatic attraction is generated between mirror layer 11 and mirror layer 12 in this region. The first and second metal thin film layers can be made of, for example, silver, which has good conductivity and typically good reflectivity in the wavelength region of most interest. Any other materials mentioned below can also be used in the first and second metal thin film layers.

[0031] In the illustrated device, a first mirror layer 11 is suspended above a substrate, and a second mirror layer is fixed to the substrate 18. This attractive force pulls the first mirror layer 11 toward the substrate 18. This narrows the mirror gap 171, changing the wavelength of radiation that can pass through the interferometer. The magnitude of the potential difference determines the magnitude of the electrostatic attraction, so the first mirror layer 11 can move up and down by changing the potential difference.

[0032] In different devices (not shown), both mirror layers are suspended in a manner that allows movement in the actuation direction, and the mirror gap 171 can be reduced / expanded by the mutual movement of the two mirror layers, moving towards / away from each other respectively.

[0033] The interferometer includes a first control electrode 131, which is separated from the control region of the first metal thin film layer 111 by a first dielectric layer. Therefore, a first control capacitor is formed between the first control electrode 131 and the first metal thin film layer 111. Figure 1a In the illustrated device, a first insulating layer 112 forms a first dielectric layer within the capacitor. In other words, a first control electrode 131 is positioned on top of the first insulating layer 112, located within the control region defined by 194 and 196. In other words, the first dielectric layer is formed from the first insulating layer 112 into which a first metal thin film layer is embedded. If the first dielectric layer comprises multiple sublayers deposited on each other, the first dielectric layer may be formed from one of these sublayers. The first dielectric layer still constitutes part of the first insulating layer.

[0034] If a first dielectric layer of different thickness is preferred, then an additional dielectric layer (not shown) can be added in regions 194-196 before depositing the first control electrode 131. This additional dielectric layer can be placed in... Figure 1a The first insulating layer 112 may be placed on top of the first insulating layer 112, or (if the first insulating layer does not extend to regions 194-196) directly on top of the metal thin film layer 111. Other variations are also possible. For example, the first control electrode 131 may be deposited on the substrate 18 in regions 194-196, and then the control electrode may be separated from the first metal thin film layer by a first dielectric layer and spacers 142.

[0035] In other words, the control capacitor is formed in the region where each control electrode overlaps with the corresponding metal thin film layer. The dielectric of each control capacitor is formed at least by a first insulating layer surrounding the metal thin film layer, but it may also include other stacked dielectric layers, such as spacers and a second insulating layer.

[0036] The interferometer also includes a second control electrode 132, which is electrically coupled to the control region of the second mirror layer 12. This electrical coupling can be capacitive or ohmic. Figure 1a An interferometer is shown, wherein the second control electrode 132 is capacitively coupled. The interferometer includes a second dielectric layer, which is located between at least a portion of the control region of the second control electrode and the second metal thin film layer, thus the second control electrode is capacitively coupled to the control region of the second metal thin film layer. The second dielectric layer is a portion of the second insulating layer 122 embedded in the second metal thin film layer. The options mentioned above regarding the first dielectric layer also apply to the second dielectric layer. Therefore, a second control capacitor is formed between the second control electrode 132 and the second thin film layer 121. The first control electrode 131 and the second control electrode 132 may, for example, be an aluminum layer.

[0037] exist Figure 1a In this configuration, spacing 141 is located on top of the second dielectric layer, which is part of the control region of the second mirror layer defined by lines 195 and 193. Insulating layers 112 and 122 are also located here between the second control electrode 132 and the second metal thin film layer 121. Therefore, both the first control electrode 131 and the second control electrode 132 are located... Figure 1a The top of the first insulating layer 112. The first and second insulating layers, as well as the spacer 141, are located between the second control electrode 132 and the second metal thin film layer 121. In other words, in Figure 1a In the first mirror layer 11, a top mirror is formed, and a second mirror layer 12, a bottom mirror is formed. The first control electrode 131 and the second control electrode 132 are located on top of the first mirror layer 11.

[0038] Alternatively, in a portion of the control area defined by lines 195 to 193, part or all of the spacer 141 and the first insulating layer 112 may be removed, allowing the second control electrode to be placed closer to the second metal thin film layer 121. In any case, the second control electrode 132 remains separated from the second metal thin film layer 121 at least by a dielectric layer, which is a portion of the second insulating layer 122 embedded in the second metal thin film layer 121. The optimal thicknesses of the first and second dielectric layers depend on the ideal capacitances of the first and second control capacitors. These desired capacitances do not necessarily have to be equal.

[0039] Figure 1c It shows Figure 1a The equivalent circuit of the device shown is included. This circuit includes a first control capacitor C. s1 Second control capacitor C s2 With the main control capacitor C control Series coupling, C control Formed in regions 193-191 and 192-194 and Figure 1b Between the control areas of the first and second mirror layers in all overlapping regions. Therefore, alternating current (AC) voltage can be transmitted through two fixed capacitors C connected in series with the main control capacitor. s1 and C s2 It is coupled between the first metal thin film layer 111 and the second metal thin film layer 121. The typical capacitance of the first control capacitor and the second control capacitor is in the pF range.

[0040] exist Figure 1a In the apparatus shown, C s1 Usually more than C s2 Much larger, and then C s2 Will be basically equal to or less than C control If C s2 Small enough, this fixed capacitor will limit the electric field strength generated between the control regions of the two metal thin-film layers (i.e., limit the electric field acting on the main control capacitor). As the mirror gap decreases, the electric field strength does not increase dramatically inversely to the mirror gap. Instead, the fixed capacitor facilitates a greater increase, allowing the mirror gap to be reduced from its resting position by up to two-thirds without the risk of the two mirrors getting stuck together.

[0041] If the material of the second dielectric layer 141 is, for example, silicon dioxide, with a relative permittivity of 3.8, and if... Figure 1b The overlapping area shown is 3.8 times larger than the surface area of ​​the second control capacitor in the region between 195 and 193, so a theoretical tuning range of 66% from the rest position to the mirror gap can be achieved, and the wavelength passing through the interferometer can be adjusted in the range of 300 nm to 3000 nm by constructive interference.

[0042] Figure 1d An alternative device is shown in which the second control electrode is in direct electrical contact with the control region of the second metal thin film layer, thus achieving ohmic coupling between the second control electrode and the control region of the second mirror layer. In this case, another control electrode is capacitively coupled to form a series capacitor, which optimizes the control performance of the Fabry-Perot device.

[0043] Figure 1d All reference numbers indicate the relationship with Figure 1a The same equipment parts are used, and the same materials listed above can be used in each part. The only difference is... Figure 1d The second control electrode 132 is located directly on top of the second metal thin film layer 121, in the control region of the second mirror layer between 195 and 193. This device can simplify the required drive electronics in certain situations. Figure 1d In the first mirror layer 11, a top mirror is formed, and a second mirror layer 12, a bottom mirror is formed. A first control electrode 131 is located on top of the first mirror layer 11, and a second control electrode 132 is located in an opening extending downward to the second metal thin film layer 121.

[0044] When the device is in use, the capacitive actuation control described above may cause static electricity buildup on the metal film layers. This can generate a direct current (DC) voltage between the first and second metal film layers, which may interfere with the operation of the device. To avoid problems caused by static electricity, an additional semi-insulating layer can be brought into contact with the metal film layers. The first metal film layer can be in direct electrical contact with the second metal film layer at one or more short-circuit points via one or more semi-insulating layers.

[0045] The frequency of the AC actuation voltage applied to the control electrode is usually so high that the presence of the semi-insulating layer does not affect the actuation force, but DC voltage can be avoided when static charge can be discharged through the semi-insulating layer and / or balanced between the first and second mirror layers.

[0046] The first mirror layer may include a first semi-insulating layer embedded within the first insulating layer and in direct electrical contact with the first metal thin film layer. The second mirror layer may include a second semi-insulating layer embedded within the second insulating layer and in direct electrical contact with the second metal thin film layer. The first semi-insulating layer may be in direct electrical contact with the second semi-insulating layer at one or more short-circuit points.

[0047] The first and second semi-insulating layers can be, for example, thin and at least partially transparent semi-conductive oxide layers, such as titanium dioxide or indium tin oxide. Figure 2The interferometer is shown, wherein reference numbers 211-212, 221-222, 231-232 and 241-242 correspond to respectively Figure 1a Reference numbers 111-112, 121-122, 131-132 and 141-142.

[0048] Figure 2 The interferometer also includes a first semi-insulating layer 251, which covers a first metal thin film layer 211 in its central region and control region. A second semi-insulating layer 252 correspondingly covers a second metal thin film layer 221 in its central region and control region.

[0049] The first semi-insulating layer 251 and the second semi-insulating layer 252 also extend to short-circuit points 261 and 262 outside the control region, where they are electrically contacted to each other. In this case, each short-circuit point includes a conductive via extending through the corresponding spacing 241 / 242, but the short-circuit point may also include only the point where layers 251 and 252 are in direct contact with each other. The conductivity of the first semi-insulating layer 251 and the second semi-insulating layer 252 is sufficient to prevent the generation of a DC electric field caused by electrostatic discharge on the optical cavity.

[0050] Additionally, the semi-insulating layers 251 and 252 extending into the optically active region may be absent, and the short-circuit point may include vias made of semi-insulating material. The DC electric field formed between the first metal thin film layer 211 and the second metal thin film layer 221 is subsequently blocked by the charge balance occurring on these semi-insulating vias.

[0051] exist Figure 1d In the illustrated device, the semi-insulating layer can also contact the metal thin film layer, and they can be short-circuited as described above. As an alternative or supplement to any of the above embodiments, a DC electric field can be prevented between the first and second metal thin film layers by depositing a semi-insulating material layer on the top, bottom, and sidewalls of the tuning cavity formed between the first and second mirror layers. The semi-insulating material layer then covers the top, bottom, and sidewalls of the tuning cavity, forming a Faraday cage in the tuning cavity where no DC electric field occurs. Another alternative or supplement to any of the embodiments described above is that... Figure 1a , Figure 1d or Figure 2 A semi-insulating material layer is deposited on the top of the entire device. Then, the semi-insulating material layer covers the control electrode and the first mirror layer 11.

[0052] This disclosure also describes a method for fabricating a capacitance-controlled Fabry-Perot interferometer on a substrate. This method has been... Figures 3a to 3gAs shown in the diagram. Substrate 38 includes a first capacitor region 391, a second capacitor region 395, a central region 393 between the first capacitor region 391 and the second capacitor region 395, a first control region 392 between the first capacitor region 391 and the central region 393, and a second control region 394 between the central region 393 and the second capacitor region 395. This is in Figure 3a As shown in the image.

[0053] The method includes the following steps: depositing a first bottom insulating material 3221 on a substrate 38, and then depositing a bottom metal thin film layer 3211 on the first bottom insulating material 3221. This in Figure 3a As shown in the figure. The method further includes the following steps: patterning the bottom metal thin film layer 3211 to extend it to the first capacitor region 391, the first control region 392, the central region 393, and the second control region 394, and then depositing a second bottom insulating material 3222 on the bottom metal thin film layer 3211, such as Figure 3b As shown. The second bottom insulating material 3222 may include the same insulating material as the first bottom insulating material 3211. Alternatively, it may include a different insulating material, so that the corresponding insulating layer embedded in the metal thin film layer will consist of two sublayers of different materials.

[0054] The method then includes the following steps: depositing a spacer material layer 34 on a second bottom insulating material 3222 and depositing a first top insulating material 3121 on the spacer material layer 34, and depositing a top metal film layer 3111 on the first top insulating material 3121. The method then includes the following steps: patterning the top metal film layer 3111 to extend it to a first control region 392, a central region 393, a second control region 394, and a second capacitor region 395. These steps are... Figure 3c and Figure 3d As shown in the image.

[0055] The method further includes the step of depositing a second top insulating material 3122 on the top metal thin film layer 3111, such as Figure 3d As shown in the diagram. The second top insulating material 3122 may include the same insulating material as the first top insulating material 3121. Alternatively, it may include a different insulating material, so that the insulating layer embedded with the metal thin film layer will consist of two sublayers of different materials.

[0056] The method further includes the following steps: depositing a conductive material layer 33 on a second top insulating material 3122, and patterning the conductive material layer 33 to form a first control electrode 331 in a first capacitor region and a second control electrode 332 in a second capacitor region, wherein the first control electrode 331 and the second control electrode 332 are electrically isolated. These steps are in... Figure 3eand Figure 3f As shown in the image.

[0057] Finally, the method further includes the following steps: forming an access hole 35 in at least the first and second top insulating materials 3121-3122 and the top metal film layer 3111 in the central region 393, and using an etchant that reaches the spacer material 34 through the access hole 35, etching the spacer material 34 down to the second bottom insulating material 3222, thereby forming a tuning cavity 37 beneath the first top insulating material 3121 of the central region 393, the first control region 392, and the second control region 394. These steps are... Figure 3g As shown in the figure. Therefore, a tuning cavity 37 is formed between the second bottom insulating material 3222 and the first top insulating material 3121.

[0058] This method minimizes the masking and etching steps required to fabricate a capacitor-controlled Fabry-Perot interferometer. Figures 3a to 3g In the method shown, control electrodes 331 and 332, which are connected to external circuitry, can be easily and reliably formed on the top surface of the device. Figure 1d In the device shown, this advantage can also be obtained if the electrode 131 is in direct contact with the metal thin film layer 111 (instead of 132 and 121 as shown in the figure).

[0059] Figure 3f and Figure 3g Reference numbers 31, 311-312, 32, 321-322, 331-332, 341-342, and 37 correspond to respectively Figure 1a Reference numbers 11, 111-112, 12, 121-122, 131-132, 141-142 and 17.

[0060] For example, the insulating material layer 3221 can be deposited by atomic layer deposition (ALD), and the metal thin film material layer can be deposited by sputtering, or any other suitable method. The spacer material can be deposited using a PECVD process. The materials and thicknesses of these layers can be any of the alternatives mentioned earlier in this disclosure.

[0061] In the manufacturing process described above, a metal thin film layer is embedded within an insulating layer to form a first mirror layer 31 and a second mirror layer 32. As mentioned above, patterning of the metal thin film layer is optional—the layer can alternatively be a continuous layer. If the material used in the metal thin film layer is sensitive to the patterning process, an additional protective layer can be applied to these layers before they are patterned. This option is not described.

[0062] The etchant used to form the tuning cavity 37 can be, for example, hydrogen fluoride. The size of the access holes 35 is exaggerated to improve sharpness; their actual size in the xy plane may be smaller than the size of the mirror.

[0063] Figure 2 The semi-insulating layer shown can be optionally included in the manufacturing process, for example by ALD deposition at an appropriate stage of the process.

Claims

1. A capacitor-controlled Fabry-Perot interferometer, the interferometer comprising: - A first mirror layer includes a first metal thin film layer embedded in a first insulating layer, wherein the first metal thin film layer acts as a reflector in the first mirror layer, and the first metal thin film layer includes a central region and a control region. - A second mirror layer includes a second metal thin film layer embedded in a second insulating layer, wherein the second metal thin film layer acts as a reflector in the second mirror layer, and the second metal thin film layer includes a central region and a control region, wherein the central region of the first metal thin film layer and the central region of the second metal thin film layer are at least partially aligned in the actuation direction, and the control region of the first metal thin film layer and the control region of the second metal thin film layer are at least partially aligned in the actuation direction. - A first control electrode and a first dielectric layer, wherein the first dielectric layer is located between at least a portion of the control region of the first control electrode and the first metal thin film layer, such that a first control capacitor is formed between the first control electrode and the first metal thin film layer, and wherein the first dielectric layer is a portion of the first insulating layer embedded in the first metal thin film layer, and the first control electrode is on top of the first mirror layer; and - A second control electrode, electrically coupled to the control region of the second metal thin film layer, wherein... The second mirror layer is located on the substrate, and the first mirror layer is suspended above the substrate by two gaps, such that a tuning cavity is formed between the first mirror layer and the second mirror layer. The interferometer further includes a second dielectric layer, which is located between at least a portion of the control region of the second control electrode and the second metal thin film layer, such that a second control capacitor is formed between the second control electrode and the second metal thin film layer, and one of the gaps is also located between the second control electrode and the second metal thin film layer, and the second control electrode is on top of the first mirror layer.

2. The capacitor-controlled Fabry-Perot interferometer according to claim 1, wherein, The second control electrode is in direct electrical contact with the second metal thin film layer in the control region of the second metal thin film layer.

3. The capacitor-controlled Fabry-Perot interferometer according to claim 1, wherein, The first metal thin film layer is in direct electrical contact with the second metal thin film layer at one or more short-circuit points via one or more semi-insulating layers.

4. The capacitor-controlled Fabry-Perot interferometer according to claim 3, wherein, The first mirror layer includes a first semi-insulating layer, which is embedded within the first insulating layer and in direct electrical contact with the first metal thin film layer. The second mirror layer includes a second semi-insulating layer, which is embedded within the second insulating layer and in direct electrical contact with the second metal thin film layer. The first semi-insulating layer is in direct electrical contact with the second semi-insulating layer at one or more short-circuit points.

5. The capacitor-controlled Fabry-Perot interferometer according to claim 1, wherein, A semi-insulating material layer covers the top, bottom, and sidewalls of the tuning cavity formed between the first mirror layer and the second mirror layer.

6. The capacitor-controlled Fabry-Perot interferometer according to claim 1, wherein, The first and second metal thin film layers are made of silver.

7. A method for fabricating a capacitance-controlled Fabry-Perot interferometer on a substrate, the substrate comprising a first capacitance region, a second capacitance region, a central region between the first capacitance region and the second capacitance region, a first control region between the first capacitance region and the central region, and a second control region between the central region and the second capacitance region, the method comprising: - Deposit a first bottom insulating material on the substrate; - Deposit a bottom metal thin film layer on the first bottom insulating material; - The bottom metal film layer is patterned such that the bottom metal film layer extends to the first capacitor region, the first control region, the central region and the second control region; - A second bottom insulating material is deposited on the bottom metal film layer, wherein the second bottom insulating material comprises the same insulating material as the first bottom insulating material; - Deposit a spacer material layer on the second bottom insulating material; - Deposit a first top insulating material on the spacer material layer; - Deposit a top metal thin film layer on the first top insulating material; - The top metal film layer is patterned such that the top metal film layer extends to the first control region, the central region, the second control region, and the second capacitor region; - A second top insulating material is deposited on the top metal film layer, wherein the second top insulating material comprises the same insulating material as the first top insulating material; - Deposit a conductive material layer on the second top insulating material; - The conductive material layer is patterned such that a first control electrode is formed in the first capacitor region and a second control electrode is formed in the second capacitor region, wherein the first control electrode and the second control electrode are electrically isolated; - An entry hole is formed in at least the first top layer insulating material, the second top layer insulating material, and the top metal film layer in the central region; - Using an etchant that reaches the spacer material through the access hole, a tuning cavity is formed below the first top layer insulating material in the central region, the first control region, and the second control region by etching the spacer material down to the second bottom layer insulating material.

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