Resonator electric layer configuration

Abstract

Herein is provided a resonator (100), comprising a resonating element (101) having an electric layer, wherein the resonating element (101) comprises a cut (201) through the electric layer to deactivate a portion of the resonating element (101). Herein is further provided an apparatus, such as a resonator array, comprising at least one resonator (100).

Description

[0001] RESONATOR ELECTRIC LAYER CONFIGURATION

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to the field of semiconductors and resonators. The disclosure relates particularly, though not exclusively, to resonator beams and the electrode layer(s) thereof.

[0004] BACKGROUND

[0005] This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

[0006] One key performance parameter in semiconductor apparatuses, such as resonators, such as silicon MEMS resonators, is the drive level dependency (DLD). At least in certain applications, the reduction of DLD is desirable.

[0007] Another key element of the performance in (MEMS) resonators is its power handling. In certain applications, a good power handling capability is especially desired. An example of such an application is 5G.

[0008] Typically, to provide resonators for applications requiring good power handling, the conventional solution has been to increase the size (the cross-section) of the resonator. The larger resonators typically come with high capacitance values, which is not desirable for certain applications. SUMMARY

[0009] The appended claims define the scope of protection. Any examples and technical descriptions of apparatuses, products and / or methods in the description and / or drawings not covered by the claims are presented not as embodiments of the invention but as background art or examples useful for understanding the invention.

[0010] It is an object of certain embodiments of the present disclosure to provide a solution having reduced drive level dependency with good power handling capacity, whilst providing low capacitance of (MEMS) resonators or at least to provide an alternative to existing technology. Accordingly, certain disclosed embodiments provide for an ingenious resonator and apparatus solving at least one of the problems related to the prior art.

[0011] According to a first example aspect of the present disclosure there is provided a resonator, comprising a resonating element having an electric layer, wherein the resonating element comprises a cut through the electric layer to deactivate a portion of the resonating element.

[0012] In certain embodiments, the resonating element comprises an electric layer (an electrically conductive layer, electrical layer) on (top of, the surface of) the resonating element. In certain embodiments, the resonating element comprises an electric layer on the topmost surface of the resonating element. In certain embodiments, the resonating element comprises a single electric layer on the resonating element. In certain embodiments, the electric layer of the resonating element covers (is configured to cover) the (entire, whole, all of, surface of) resonating element. In certain embodiments, the electric layer of the resonating element covers essentially the resonating element.

[0013] In certain embodiments, the cut comprises an area wherein the electric layer is removed. In certain embodiments, the electric layer is removed in the cut (the area of a cut). In certain embodiments, the cut is a shape (a line, a groove, a discontinuity region) wherein the electric layer is removed. In certain embodiments, the cut is a discontinuity region (discontinuity line, discontinuity area) within the electric layer.

[0014] In certain embodiments, the resonating element comprises at least a cut in the electric layer thereof. In certain embodiments, the resonating element comprises at least two cuts in the electric layer thereof. In certain embodiments, the resonating element comprises a plurality of cuts in the electric layer thereof. In certain embodiments, the resonating element comprises a plurality of cuts through the electric layer to deactivate portions of the resonating elements. What is herein disclosed for a (single) cut applies equally to a plurality of cuts, and vice versa.

[0015] In certain embodiments, the resonating element comprises a cut through the electric layer to deactivate (disconnect) a part of the resonator. In certain embodiments, the resonating element comprises cuts through the electric layer to deactivate a plurality of regions (areas, places) the resonator. In certain embodiments, the cut is configured to provide a partial deactivation of the resonator.

[0016] In certain embodiments, the electric layer of the resonating element comprises a cut to deactivate a portion of the resonating element. In certain embodiments, the electric layer of the resonating element comprises a cut to deactivate partly the resonating element. In certain embodiments, the electric layer of the resonating element comprises a cut to deactivate a region of the resonating element. In certain embodiments, the cut is configured to provide a partial deactivation of the resonating element. In certain embodiments, the electric layer of the resonating element comprises a cut to render (at least some) a part of the resonating element deactivated (deactive).

[0017] In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate a plurality of regions (areas) the resonating element. In certain embodiments, the electric layer of the resonating element comprises a plurality of cuts to deactivate portions of the resonating element. In certain embodiments, the cut of the electric layer are configured to deactivate a part of the resonating elements.

[0018] In certain embodiments, the resonating element comprises an active portion and a deactivated portion, separated from each other by the cut. In certain embodiments, the resonating element comprises active portions and deactivated portions, separated from each other by cuts.

[0019] In certain embodiments, the resonator comprises more than one (such as two) anchoring points. In certain embodiments, the resonating element is suspended to the support structure via anchoring point(s). In certain embodiments, the anchoring points provide an electrical connection to an electrical terminal for the resonating element.

[0020] In certain embodiments, the cut is configured to deactivate an anchoring point of the resonator. In certain embodiments, the electric layer of the resonator comprises a cut to deactivate a part of the resonator, wherein the cut is configured to deactivate a portion of the resonating element and an anchoring point of the resonator. In certain embodiments, the electric layer of the resonator comprises a plurality of cut to deactivate a part of the resonator, wherein the cuts are configured to deactivate portions of the resonating element and an anchoring point of the resonator.

[0021] In certain embodiments, the cut is configured to deactivate a part of a resonator (but not the entire resonator). In certain embodiments, the cut is configured to deactivate a part of a resonating element (not the entire resonating element). In certain embodiments, the cuts are configured to deactivate (a plurality of) parts of the resonating element (but not entire resonating element). In certain embodiments, the cut is configured to deactivate a portion (part, region, area) of the resonating element by preventing charge carriers from crossing (moving across, moving from one side to another) the cut. In certain embodiments, the cut prevents charge carriers from crossing the cut. In certain embodiments, the cut prevents electric current from crossing the cut.

[0022] In certain embodiments, the cut is formed of a line through the electric layer. In certain embodiments, the cut is a discontinuity region (discontinuity line, discontinuity area) within the electric layer. In certain embodiments, the cut is a discontinuity region of the electric layer, configured to prevent charge carriers from crossing it. In certain embodiments, the cut is provided by patterning and etching the electric layer.

[0023] In certain embodiments, the resonating element has a width and a length. In certain embodiments, the resonating element comprises (at least, at least one) a cut through the electric layer of a resonating element in a width direction of the resonating element (in x- direction). In certain embodiments, the resonating element comprises the cut through the electric layer in a x-direction (or deviates at most 45 degrees from the x-direction). In certain embodiments, the resonating element comprises the cut through the electric layer in a width direction across the resonating element when observed from above. In certain embodiments, the resonating element comprises the cut through the electric layer in a horizontal direction (across the resonating element when observed from above). In certain embodiments, the resonating element comprises cuts through the electric layer of the resonating element in a width direction of the resonating element (in x-direction).

[0024] In certain embodiments, the resonating element comprises (at least, at least one) a cut through the electric layer of the resonating element in a length direction of the resonating element (in y-direction). In certain embodiments, resonating element comprises the cut through the electric layer in a y-direction (or deviates at most 45 degrees from the x- direction). In certain embodiments, the resonating element comprises the cut through the electric layer in a length direction (across the resonating element when observed from above). In certain embodiments, the resonating element comprises the cut through the electric layer in a vertical direction (across the resonating element when observed from above). In certain embodiments, the resonating element comprises cuts through the electric layer of the resonating element in a length direction of the resonating element (in y- di recti on).

[0025] In certain embodiments, the cut is longitudinally non-centred along the resonating element (cut is in peripheral area of the resonating element, in either length- or width direction). In certain embodiments, the cut is longitudinally centred along the resonating element (in either length- or width direction).

[0026] In certain embodiments, the resonating element comprises the cut through the electric layer in a centre (in a central area, in centremost area) of the resonating element. In certain embodiments, the resonating element comprises the cut through the electric layer in a width direction of a resonating element in the centre (lengthwise) of the resonating element.

[0027] In certain embodiments, the cut continues (extends, reaches) through the electric layer (in x / y-direction / plane). In certain embodiments, the cut is a planar cut (or a plurality of planar cuts). In certain embodiments, the cut is formed in a horizontal plane.

[0028] In certain embodiments, the electric layer of the resonating element comprises the cut through the resonating element from one side to the other (from one side of the resonating element to the other side of the resonating element). In certain embodiments, the electric layer of the resonating element comprises the cut through the resonating element from one trench to the other (from a trench on a one side of the resonating element to the trench on the other side of the resonating element).

[0029] In certain embodiments, the cut extends (reaches, travels, is, goes, continues) from trench to trench. In certain embodiments, the cut extends from a trench to another trench. In certain embodiments, the cut extends from one trench to another trench.

[0030] In certain embodiments, the trenches comprise edges. In certain embodiments, as used herein, the edge of the trench is to be understood as the (outside) limit (or a border) of the trench. In certain embodiments, cuts extend (reach, travel, are, go) from a trench edge to another trench edge. In certain embodiments, cuts reach all the way from one trench’s edge to another trench’s edge. In certain embodiments, said cuts reach from one trench’s edge to another trench’s edge. In certain embodiment, said cuts reaching from one trench’s edge to another trench’s edge prevent charge carriers from crossing within the electric layer in that location.

[0031] In certain embodiments, the resonating element is separated from the support structure by a cavity, rendering the resonating element to be encircled by a trench (trenches). In certain embodiments, the resonating element is surrounded by trenches in all sides thereof.

[0032] In certain embodiments, the resonating element comprises the cut through the electric layer when observed from side. In certain embodiments, the resonating element comprises the cut through the electric layer in z-direction. In certain embodiments, the cut continues (extends, reaches, travels, is, goes) through the electric layer (in z-direction). In certain embodiments, the cut continues through the electric layer to the piezoelectric layer (the z- direction, ‘depth’ direction). In certain embodiments, the cut (is configured to) expose the layer(s) beneath the electric layer. In certain embodiments, the cut (is configured to) expose the piezoelectric layer beneath the electric layer. In certain embodiments, cut is of same depth as the electric layer thickness.

[0033] In certain embodiments, the cut reaches (extends) through the electric layer both in x / y- direction and in z-direction. In certain embodiments, the cut reaches through the electric layer both in horizontal direction and in vertical direction. In certain embodiments, the cut reaches through the electric layer both in planar direction and in depth direction.

[0034] In certain embodiments, the electric layer is (acts as, is implemented by) a top electrode (layer). In certain embodiments, the electric layer is the top electrode of the resonator. In certain embodiments, the electric layer is the topmost layer of the resonator (the material stack of the resonator). In certain embodiments, the electric layer is implemented by a layer of metal. In certain embodiments, the electric layer comprises (is of, is made of, is fabricated from, contains) metal, preferably gold (Au). In certain embodiments, the electric layer comprises metal, preferably gold. In certain embodiments, the electric layer is of gold, preferably doped gold. In certain embodiments, the electric layer is of gold alloy.

[0035] In certain embodiments, the electric layer is implemented by a layer of doped silicon. In certain embodiments, the silicon layer is of single-crystal silicon. In certain embodiments, the electric layer is implemented by a layer of doped polysilicon. In certain embodiments, the resonating element comprises a piezoelectric layer, wherein the electric layer is on the piezoelectric layer, and a bottom electrode (such as a silicon layer) on the opposite side of the piezoelectric layer than the electric layer.

[0036] In certain embodiments, the bottom electrode comprises (is of, is implemented by) silicon. In certain embodiments, the bottom electrode is implemented by a doped silicon layer. In certain embodiments, the bottom electrode comprises silicon, preferably doped silicon, such as ultra-heavily doped, UHD, silicon. In certain preferred embodiments, the silicon is of single-crystal silicon. In certain embodiments, the bottom electrode (layer) is implemented by an UHD silicon layer.

[0037] In certain embodiments, the doping level of the silicon is above 1019cm-3. In certain embodiments, the doping level of the silicon is above 102° cm"3. In certain embodiments, the doped silicon is of N-type or P-type doping.

[0038] In certain embodiments, the resonator comprises a material stack, the material stack comprising the silicon layer (the bottom electrode), the piezoelectric layer on top of the silicon layer, and an electric layer on top of the piezoelectric layer. In certain embodiments, the resonator is a piezoelectric resonator. In certain embodiments, the piezoelectric layer comprises aluminum nitride.

[0039] In certain embodiments, the resonator comprises at least one resonating element. In certain embodiments, the resonating element comprises a plurality of resonating elements.

[0040] In certain embodiments, the resonating element comprises a plurality of resonating beam elements (resonating beams). In certain embodiments, each beam element is a subelement of the resonator. In certain embodiments, the resonating element comprises a plurality of resonating beam elements side by side in a plane, connected to one another by connection elements and separated from one another by trenches.

[0041] In certain embodiments, the resonating element comprises a plurality of resonating beam elements, and wherein the resonating element comprises a plurality of cuts through the electric layer to deactivate (disconnect) at least a portion of the resonating beam elements. In certain embodiments, the resonating beam elements are separated from one another by trenches.

[0042] In certain embodiments, the electric layer of the resonating element covers the (surface of) resonating beam elements and the (surface of) connection elements within the resonating element. In certain embodiments, the resonator comprises a plurality of beam elements having a length and a width. In certain embodiments, the plurality of beam elements are positioned adjacent to each other. In certain embodiments, adjacent beam elements are mechanically connected to each other by connection elements. In certain embodiments, each adjacent beam element is mechanically connected to another beam element by connection elements. In certain embodiments, each adjacent beam element is mechanically connected to another beam element by (at least) two connection elements.

[0043] In certain embodiments, the resonator is a stacked beam resonator. In certain embodiments, the stacked beam resonator comprises a plurality of beam elements positioned side-by-side in a plane. In certain embodiments, the plurality of beam elements are positions adjacent to each other in a width direction thereof. In certain embodiments, the plurality of beam elements are positioned adjacent to each other in a width direction of the resonator. In certain embodiments, the beam elements are separated by trenches. In certain embodiments, the beam elements are connected to each other by connection elements.

[0044] In certain embodiments, the resonator comprises a plurality of beam elements, such as seven, nine, or eleven beam elements. In certain embodiments, said adjacent beam elements are mechanically connected to each other by connection elements. In certain embodiments, the beam elements of the resonator are arranged in a rectangular array configuration.

[0045] In certain embodiments, the resonator (the resonating element) is in the shape of a rectangle. In certain embodiments, the resonator (the resonating element) is in the shape of an elongated rectangle (beam-shaped). In certain embodiments, the resonator (the resonating element) has an aspect ratio (ratio of length to width, when observed from above) different from 1 .

[0046] In certain embodiments, the resonator has a length-to-width aspect ratio of less than 1. In certain embodiments, the resonator is attached (supported, anchored, suspended) to a support structure. In certain embodiments, the resonator is attached to a support structure from the outermost beam elements of the resonator. In certain embodiments, the resonator comprises at least one anchor (anchoring point) configured to connect the resonator to, and suspend the resonator from surrounding layers. In certain embodiments the at least one anchor (anchoring point) comprises portions of the piezoelectric layer, the electric layer and the bottom electrode. In certain embodiments, each beam element is in the shape of a (rectangular) beam. In certain embodiments, each beam element has an aspect ratio (ratio of length to width, when observed from above) different from 1. In certain embodiments, each beam element has a length-to-width aspect ratio of more than 1 .

[0047] In certain embodiments, the electric layer of the resonating element comprises cuts to render at least one of the resonating beam elements deactivated. In certain embodiments, the electric layer of the resonating element comprises cuts to render at least some (number) of the resonating beam elements deactivated. In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate at least some of (part of, partly) the resonating beam elements. In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate at least one of the resonating beam elements (entirely). In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate a plurality of the resonating beam elements (entirely). In certain embodiments, the cuts of the electric layer are configured to deactivate some of the resonating beam elements (entirely).

[0048] In certain embodiments, the cuts are configured to deactivate a part of a resonating beam element (not the entire resonating beam element). In certain embodiments, the cuts are configured to deactivate (a plurality of) parts of the resonating beam elements (not entire resonating beam elements). In certain embodiments, the cuts are configured to deactivate (disconnect) the resonating beam elements by preventing charge carriers from crossing (moving across, moving from one side to another) the cut. In certain embodiments, the cut prevents charge carriers from crossing the cut. In certain embodiments, the cut prevents electric current from crossing the cut.

[0049] In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate a portion of one resonating beam element. In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate at least a portion of the resonating beam elements. In certain embodiments, the resonating element comprises a plurality of cuts through the electric layer to deactivate portions of the resonating beam elements.

[0050] In certain embodiments, the electric layer of the resonating element comprises cuts to deactivate a group of (a subset of) the resonating beam elements. In certain embodiments, the resonating element comprises a first group of resonating beam elements and a second group of resonating beam elements. In certain embodiments, the first group of resonating beam elements is deactivated by cuts in the electric layer. In certain embodiments, the second group of resonating beam elements remains active within the resonating element. In certain embodiments, the second group of resonating beam elements is absent from cuts.

[0051] In certain embodiments, the resonating element comprises (at least, at least one) a cut through the electric layer of a resonating beam element in a width direction of the resonating beam element (in x-direction). In certain embodiments, the resonating element comprises the cut through the electric layer of the resonating beam element in a x-direction (or deviates at most 45 degrees from the x-direction). In certain embodiments, the resonating element comprises the cut through the electric layer of the resonating beam element in a width direction (across the resonating element when observed from above). In certain embodiments, the resonating element comprises the cut through the electric layer of the resonating beam element in a horizontal direction (across the resonating element when observed from above). In certain embodiments, the resonating element comprises cuts through the electric layer of the resonating beam elements in a width direction of the resonating beam element (in x-direction).

[0052] In certain embodiments, the resonating element comprises (at least, at least one) a cut through the electric layer of a connection element (in a length direction of the resonating beam element, in y-direction). In certain embodiments, the resonating element comprises cuts through the electric layer of the connection elements (in a length direction of the resonating beam element, in y-direction). In certain embodiments, the resonating beam element comprises the cut through the electric layer of the resonating beam element in a y- direction (or deviates at most 45 degrees from the x-direction). In certain embodiments, the resonating beam element comprises the cut through the electric layer of the resonating beam element in a length direction (across the resonating element when observed from above). In certain embodiments, the resonating beam element comprises the cut through the electric layer of the resonating beam element in a vertical direction (across the resonating element when observed from above). in certain embodiments, the resonator comprises more than one cut, such as two cuts. In certain embodiments, the cut(s) are arranged in the proximity of the resonating element’s edge (close to a trench). In certain embodiment, the cut(s) are arranged parallel to the x- direction of the resonating element (long edge of the resonating element). In certain embodiments, the cut(s) are arranged in the proximity of the long edge (x-directional edge) of the resonating element. In certain embodiments, the cuts are arranged in opposite sides of the resonating element. In certain embodiments, the cuts are not equally distant from the resonating element edge. In certain embodiments, one cut crosses at least one (internal) trench of the resonating element, whilst the other cut does not. In certain alternative embodiments, the cuts are equally distant from the resonating element edges.

[0053] In certain embodiments, the cut is non-straight. In certain embodiments, the cut is a meandering cut. In certain embodiments, the cut comprises a meandering cut. In certain embodiments, the cut is a non-straight cut, such as a meandering cut. In certain embodiments, the cut is bendy (curvy, wavy) cut. In certain embodiments, the meandering cuts protrude from the edge of the resonating element towards the middle of the resonating element (in each meander).

[0054] In certain embodiments, the resonating element (the electric layer thereof) comprises both a straight and a non-straight (meandering) cut (at least two cuts in total). In certain embodiments, the straight cut is arranged in the proximity of the resonating element’s edge. In certain embodiments, the straight cut is displaced from the resonating element’s edge by a length, which is 10-30% of the resonating element’s width. In certain embodiments, the straight cut is displaced from the resonating element edge by a length, which is approximately 20% of the resonating element’s width.

[0055] In certain embodiments, the non-straight cut is arranged in the proximity of the resonating element’s edge. In certain embodiments, the non-straight cut is displaced from the resonating element’s edge by a length, which is 1-10% of the resonating element’s width (measured from the part of the non-straight cut which is closest to the resonating element’s edge). In certain embodiments, the non-straight cut is displaced from the resonating element edge by a length, which is approximately 5% of the resonating element’s width. In certain embodiments, the resonator is fabricated on a substrate. In certain embodiments, the substrate is a wafer. In certain embodiments, the substrate is a silicon-on-insulator, SOI, wafer. In certain embodiments, the substrate comprises a silicon layer. In certain embodiments, the bottom electrode (layer) is referred to as a substrate or as a silicon layer.

[0056] In certain embodiments, the resonating beam element(s) are longitudinally aligned within 25 degrees of a <100> crystal direction of silicon (of the bottom electrode). Within at least some embodiments the resonating beam element(s) are longitudinally aligned with a <100 crystal direction of the silicon (of the bottom electrode) such that a longitudinal axis of each resonating beam is within 25 degrees of the <100> crystal direction of the silicon (of the bottom electrode). In certain embodiments, the resonating beam element(s) are longitudinally aligned within 45 degrees, or 50 degrees of a <100> crystal direction of silicon (of the bottom electrode). Within at least some embodiments the resonating beam element(s) are longitudinally aligned with a <100> crystal direction of the silicon (of the bottom electrode) such that a longitudinal axis of each resonating beam is within 45 degrees, or 50 degrees of the <100> crystal direction of the silicon (of the bottom electrode).

[0057] In certain embodiments, the resonating beam element(s) are longitudinally aligned within 25 degrees of a

[0100] crystal direction of silicon (of the bottom electrode). Within at least some embodiments the resonating beam element(s) are longitudinally aligned with a

[0100] crystal direction of the silicon (of the bottom electrode) such that a longitudinal axis of each resonating beam is within 25 degrees of the

[0100] crystal direction of the silicon (of the bottom electrode).

[0058] In certain embodiments, the resonating beam element(s) are longitudinally aligned within 25 degrees of a

[0110] crystal direction of silicon (of the bottom electrode). Within at least some embodiments the resonating beam element(s) are longitudinally aligned with a

[0110] crystal direction of the silicon (of the bottom electrode) such that a longitudinal axis of each resonating beam is within 25 degrees of the

[0110] crystal direction of the silicon (of the bottom electrode).

[0059] In certain embodiments, the resonating beam element(s) are longitudinally aligned within 25 degrees of a

[0111] crystal direction of silicon (of the bottom electrode). Within at least some embodiments the resonating beam element(s) are longitudinally aligned with a

[0111] crystal direction of the silicon (of the bottom electrode) such that a longitudinal axis of each resonating beam is within 25 degrees of the

[0111] crystal direction of the silicon (of the bottom electrode).

[0060] In certain embodiments, the resonator is configured to resonate (operate, oscillate, vibrate) in an in-plane resonance mode. In certain embodiments, the resonating element is configured to resonate in a length-extensional, LE, resonance mode. In certain embodiments, the resonator is configured to resonate in an in-plane length-extensional, LE, resonance mode. In certain embodiments, the length extensional resonance mode is configured to resonate parallel to the length direction of the resonator. In certain embodiments, the length extensional resonance mode is configured to resonate perpendicular to the width direction of the resonator. In certain embodiments, the resonating element is configured to resonate in a squareextensional, SE, resonance mode. In certain embodiments, the resonating element is configured to resonate in a width-extensional, WE, resonance mode.

[0061] In certain embodiments, the resonator is configured to resonate in a collective resonance mode. In certain embodiments, each resonating element of the resonator is configured to resonate in the (same) collective resonance mode. In certain embodiments, the resonator is configured to resonate in a desired (main) resonance mode. In certain embodiments, each beam element of the resonator is configured to resonate in the (same) desired resonance mode.

[0062] In certain embodiments, the resonator is a microelectromechanical systems, MEMS, resonator. In certain embodiments, the resonator is (part of) a semiconductor device. In certain embodiments, the resonator is configured to operate in a megahertz frequency area. In certain embodiments, the resonator is configured to operate at 32 MHz frequency.

[0063] According to a second example aspect of the present disclosure there is provided an apparatus, such as a resonator array (an apparatus), comprising at least one resonator according to the first aspect or any of its embodiments. In certain embodiments, the apparatus comprises (at least) two (more than one) resonators of the first aspect or any of its embodiments coupled to each other. In certain embodiments, the resonators are coupled to each other by a coupler.

[0064] In certain embodiments, the apparatus comprises extensional-mode resonators. In certain embodiments, the apparatus comprises a flexural mode resonator. In certain embodiments, the apparatus comprises a mechanical connector element which connects the flexural resonator to the extensional-mode resonators.

[0065] In certain embodiments, each resonator comprises a plurality of beam elements having a length and a width, wherein the plurality of beam elements are positioned adjacent to each other and adjacent beam elements are mechanically connected to each other by connection elements. In certain embodiments, the plurality of beam elements are separated from each other by trenches.

[0066] In certain embodiments, more than 50% of the mass of the apparatus comprise material portions of single-crystalline silicon.

[0067] In accordance with certain embodiments, embodiments of the second aspect are provided, the embodiments comprising subject matter of any single embodiment presented in connection with the first aspect, or the embodiments comprising subject matter of any of the embodiments presented in connection with the first aspect combined with subject matter presented in any other embodiment or embodiments.

[0068] Different non-binding example aspects and embodiments have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in different implementations. Some embodiments may be presented only with reference to certain example aspects. It should be appreciated that corresponding embodiments may apply to other example aspects as well. In particular, the embodiments described in the context of the first aspect are applicable to each further aspect. Any appropriate combinations of the embodiments may be formed.

[0069] BRIEF DESCRIPTION OF THE FIGURES

[0070] Some example embodiments will be described with reference to the accompanying figures, in which:

[0071] Fig. 1a schematically shows a resonator having an electric layer comprising a cut in one direction according to an example embodiment;

[0072] Fig. 1 b schematically shows a resonator having an electric layer comprising a cut in another direction according to another example embodiment;

[0073] Fig. 1c schematically shows a cut of the electric layer of the resonator in side view according to an example embodiment;

[0074] Fig. 1d schematically shows a material stack of a resonator according to an example embodiment;

[0075] Fig. 2 schematically shows a top view of an example resonator structure according to an example embodiment;

[0076] Fig. 3a schematically shows an electric layer configuration of a beam resonator having four vertical cuts according to an example embodiment;

[0077] Fig. 3b schematically shows an electric layer configuration of a beam resonator having two vertical cuts according to an example embodiment;

[0078] Fig. 3c schematically shows an electric layer configuration of a beam resonator having a plurality of horizontal cuts according to an example embodiment;

[0079] Fig. 3d schematically shows an electric layer configuration of a beam resonator having non-centered horizontal cuts according to an example embodiment Fig. 3e schematically shows an electric layer configuration having a plurality of cuts in peripherals of the beam resonator according to further another example embodiment;

[0080] Fig. 4a schematically shows an example of a resonator array having two resonators with electric layer configuration according to an example embodiment;

[0081] Fig. 4b schematically shows another example of a resonator array having non-centered horizontal electric layer configuration according to an example embodiment;

[0082] Fig. 4c schematically shows another example of a resonator array having electric layer configuration deactivating every other beam element according to another example embodiment;

[0083] Fig. 4d schematically shows another example of a resonator array having electric layer configuration having a plurality of cuts in peripherals of the resonators according to yet another example embodiment.

[0084] Fig. 5a schematically shows an example of a resonator having electric layer configuration having a plurality of cuts according to an example embodiment;

[0085] Fig. 5b schematically shows an example of a resonator array having electric layer configuration having a plurality of cuts according to an example embodiment;

[0086] Fig. 6a schematically shows an example of a resonator having electric layer configuration having a meandering cut according to an example embodiment;

[0087] Fig. 6b schematically shows an example of a resonator array having electric layer configuration having a meandering cut according to an example embodiment;

[0088] Fig. 7 schematically shows an example of a resonator having electric layer configuration having a straight and a meandering cut according to an example embodiment; and

[0089] Fig. 8 schematically shows an enlarged view of a cut showing the route of electrical current according to an example embodiment.

[0090] DETAILED DESCRIPTION

[0091] In the following description, like reference signs denote like elements or steps.

[0092] As used herein, the term horizontal refers to the direction of left to right (or right to left), when observing the resonator from above, meaning the x-direction according to the chosen coordinate system. In the example embodiments shown herein, the x-direction is equal to the width direction of the resonating element. Analogously, as used herein, the term vertical refers to the direction of up and down (or down to up, when observing the resonator from above), meaning the y-direction according to the chosen coordinate system. In the example embodiments shown herein, the y- direction is equal to the length direction of the resonating element.

[0093] Yet analogously, as used herein, herein is also used a direction of left to right (or right to left), when observing the resonator from the side, meaning the z-direction according to the chosen coordinate system. In the example embodiments shown herein, the z-direction is referred as a “height” direction of the resonator.

[0094] As used herein, the term “cut” (through the electric layer) is used to refer to as an area or a region of the electric layer, wherein the electric layer has been removed from that particular area or region. In certain embodiments, the resonating element is electrically cut (“broken”, not passing electric current across the cut). In certain embodiments, the cut is an area wherein the electric layer is removed. In certain embodiments, the “cut” is a region of the electric layer, wherein the electric layer is absent. In certain embodiments, the resonating element has an electric layer, wherein the electric layer is at least partially absent (in certain region(s)). Synonyms for the term “cut” can be for example line, groove, cutting line, patterned line, discontinuity line, discontinuity area, discontinuity region and isolating line. The cut is configured to prevent electric current, meaning any charge carriers (electrons, holes) from crossing it (from one side to another side of the cut).

[0095] As used herein, the terms “deactivate” or “deactivated” is used to refer to disconnecting an area or a portion of (the electric layer I top electrode layer of) the resonating element from the electrical terminal(s) of the resonator. When an area or a portion of the resonating element is deactivated, the area or portion will not be part of an electrical circuit. Namely, the electric current does not pass in this area or portion in between the top electrode (electric layer) and the bottom electrode layer. Thus, in certain embodiments, said “deactivated” area is disconnected from the other regions of the resonating element and its electrical terminal. Synonyms for the term “deactivate” are for example disconnect, disable, electrically disconnect, and electrically separate. In certain embodiments, the cut(s) disable electrically some part of the resonating element (the electric layer of the resonating element). In certain embodiments, the deactivated a portion of the resonating element is provided by preventing charge carriers from passing the electric layer (the top electrode) of said portion of the resonating element. Analogously, as used herein, the term “active” is used to refer to the opposite of deactivated. The “active” area or region of (the electric layer I top electrode layer of) the resonating element is connected to (coupled to) an (one) electrical terminal of the resonating element. The electric current and charge carriers are able to move within the active area or portion of the resonating element to or from the terminal. Namely, the electric current passes in this area or portion in between the top electrode (electric layer) and the bottom electrode layer, as usual. The electric layer (which is of electrically conducting material) provides electrical connection to the “active” (non-deactivated) area or portion of the resonating element.

[0096] Figs. 1a and 1 b schematically shows an example resonator having an electric layer, each Figure showing a cut in one direction according to an example embodiment. Figs. 1a and 1 b show a top view (from above, from up to down) of the example resonator. In certain embodiments, the resonator 100 comprises at least one resonating element 101 having an electric layer (shown in gray colour in Figs. 1a and 1b). In certain embodiments, the electric layer is an electrically conductive layer on the topmost surface of the resonating element 101. In certain embodiments, the electric layer forms the top electrode of the resonating element 101. In certain embodiments, the electric layer covers the entire surface of resonating element 101 (except for the cut 201 , which is elaborated in detail below).

[0097] As shown in Figs. 1a and 1b, in certain embodiments, the resonating element 101 comprises at least one cut 201 in the electric layer thereof. In certain embodiments, the resonating element 101 is separated from the support structure 110 by a cavity, rendering the resonating element 101 being encircled by a trench 104’. In certain embodiments, the cut 201 extends through the electric layer, from one trench 104’ to the trench 104’ on the other side of the resonating element 101. In certain embodiments, the cut 201 through the electric layer cuts (interrupts, disconnects) the electric layer entirely (in x / y-direction, reaching from a trench to trench, from one side of the resonating element 101 to the other side of the resonating element 101).

[0098] As shown in Fig. 1a, in certain embodiments, the resonating element 101 comprises the cut 201 through the electric layer in a y-direction (in vertical direction, across the resonating element 101 when observed from above). As shown in Fig. 1b, in certain embodiments, the resonating element 101 comprises the cut 201 through the electric layer in a x-direction (in horizontal direction, across the resonating element 101 when observed from above). In certain embodiments, the cut 201 through the electric layer of the resonating element 101 travels in a direction deviating at most 45 degrees from the x-direction (or y-direction) (not shown in Figs. 1a or 1b).

[0099] Fig. 1b shows a symmetric resonating element 101. In certain embodiments, as shown in the embodiment of Fig. 1 b, the electric layer comprises two cuts 201 symmetrically arranged (mirror symmetry). In certain embodiments, the cuts 201 run parallel with each other. In certain embodiments, the cuts 201 are equally far apart from the resonating element edge (or from the trench 104’).

[0100] In certain embodiments, the cut 201 through the electric layer cuts (interrupts, disconnects) the electric layer entirely (both in z-direction, and in x / y-direction). In certain embodiments, the cut 201 continues through the electric layer in z-direction exposing the layer(s) beneath the electric layer. In certain embodiments, cut 201 is of same depth as the electric layer thickness.

[0101] In certain embodiments, the cut 201 is fabricated via lithographic patterning of the electric layer. After lithographic patterning, the electric layer is removed in successive etching process steps. In certain embodiments, the width / size / diameter of the cut 201 in a mask prior to etching controls the depth of the etching. In certain embodiments, the electric layer is patterned and the cut 201 is formed via dry etching, such as deep reactive ion etching, DRIE. In certain embodiments, the electric layer is patterned and the cut 201 is formed via wet etching.

[0102] In certain embodiments, the resonator 100 comprises a path from an anchoring point 103a to an electrical terminal. In certain embodiments, the electric contact to the resonating element 101 is provided via the anchoring point 103a. In certain embodiments, the cut 201 is extending through the electric layer to deactivate a portion of the resonating element 101 . In certain embodiments, the cut 201 disconnects a portion of the resonating element 101 from electric contact.

[0103] In certain embodiments, the cut 201 divides the resonating element 101 to (at least one) active portion and (at least one) deactivated portion. In certain embodiments, the deactivated portion of the resonating element 101 resides on the other side of the cut 201 in comparison to the location of the anchoring point 103a. In certain embodiments, the deactivated portion of the resonating element 101 resides on the same side of the cut 201 in comparison to the location of the anchoring point 103a. In certain embodiments, the active portion of the resonating element 101 receives electric current (as usual), the electric current travelling in the electric layer. In certain embodiments, the deactivated portion of the resonating element 101 receives no electric current, due to the cut 201. In certain embodiments, there are no charge carriers in the deactivated portion of the resonating element 101 as the cut 201 prevents any charge carriers from crossing. In certain embodiments, the deactivated portion of the resonating element 101 is mechanically connected but electrically isolated from the remainder of the resonating element 101.

[0104] In certain embodiments, the cut 201 is fabricated as thin as possible. In certain embodiments, the cut 201 has a width in the range of 0.2 pm to 2 pm. In certain embodiments, the cut 201 has a width of less than 1 pm, or less than 0.8 pm. In certain embodiments, the cut 201 has a width of less than 0.5 pm, such as less than 0.3 pm.

[0105] Accordingly, herein is provided a resonator 100, comprising a resonating element 101 having an electric layer, wherein the resonating element 101 comprises a cut 201 through the electric layer to deactivate at least a portion of the resonating element 101 .

[0106] Fig. 1b further shows a marked line A, representing the location of the cross section shown in the following Fig. 1c.

[0107] Fig. 1 c schematically shows a cross-section of the resonating element 101 , showing the cut 201 in the electric layer in side view according to an example embodiment. The location of the cross section shown in Fig. 1c is marked as line A in Fig. 1 b.

[0108] As mentioned, in certain embodiments, the cut 201 interrupts the electric layer in z-direction (depth direction), exposing the layer(s) beneath the electric layer. In certain embodiments, cut 201 is of same depth as the electric layer thickness, as shown in Fig. 1c.

[0109] In certain embodiments, the resonating element 101 comprises (at least) the silicon layer L4, the piezoelectric layer L2 on top of the silicon layer, and an electric layer L1 on top of the piezoelectric layer. In this embodiment, the cut 201 is configured to expose the piezoelectric layer L2 beneath the electric layer L1 .

[0110] In certain embodiments, the electric layer is implemented by a layer of metal, preferably gold (Au), certain embodiments, the electric layer is of gold, preferably doped gold. In certain embodiments, the electric layer is of gold alloy. Fig. 1d schematically shows a material stack of a resonator 100 according to an example embodiment. Fig. 1d schematically shows an example cross section (sectional view, side view) of the resonator 100 residing on a substrate.

[0111] In certain embodiments, the resonator 100 is fabricated on a substrate. In the example embodiment of Fig. 1d, a silicon on insulator (SOI) substrate (wafer) 450 is used. The reference numerals 401 and 402 denote bottom electrode and top electrode (electric layer) contacts, respectively.

[0112] In certain embodiments, the resonator 100 comprises a material stack, the material stack comprising at least the silicon layer L4, the piezoelectric layer L2 on top of the silicon layer, and an electric layer L1 on top of the piezoelectric layer. In certain embodiments, the electric layer L1 is the top electrode of the resonator 100. In certain embodiments, the piezoelectric layer comprises doping, such as scandium doping.

[0113] In the example embodiment shown in Fig. 1 d, the electric layer is implemented in layer L1. In this example embodiment, layer L2 is a piezoelectric layer for piezoelectric actuation of the resonator residing in the area of denoted by 100. An opening in L2 is denoted by 420. In this example embodiments, layer L3 denotes a layer for the bottom electrode. In this example embodiment, layer L4 is a silicon layer for the resonator (for example resonating beam elements and their connecting elements according to certain embodiments). In this example embodiments, layer L5 is a buried oxide layer (SiO2) of the SOI wafer, and layer L6 is a silicon handle layer. In certain embodiments layer L6 comprises a cavity C1. In certain embodiments, the layer L5 follows the cavity C1 shape as shown in Fig. 1d.

[0114] In certain embodiments, when a doped silicon layer is used as L4, it is possible to leave out the separate L3 bottom electrode. In such embodiments, the conductive doped silicon layer L4 acts as the bottom electrode. In certain embodiments, the silicon layer L4 comprises degenerately doped silicon. In certain embodiments, more than 50 % of the silicon layer L4 mass consists of degenerately doped silicon. In certain embodiments, the silicon layer L4 is doped to an average impurity concentration of at least 2*1019cm-3, such as at least 102° cm-3. In certain embodiments, the doped silicon is of N-type or P-type doping. In certain embodiments, the bottom electrode comprises ultra-heavily doped, UHD, silicon.

[0115] In certain embodiments, the silicon layer L4 comprises single crystalline silicon. In certain embodiments, the silicon layer L4 consists essentially of single crystalline silicon. In certain embodiments, the silicon layer L4 comprises degenerately doped single crystalline silicon. In certain preferred embodiments, the resonator 100 comprises a material stack, the material stack comprising the silicon layer L4 (the bottom electrode), the piezoelectric layer L2 on top of the silicon layer L4, and an electric layer L1 on top of the piezoelectric layer L1. In certain embodiments, the resonator 100 is a piezoelectric resonator. In certain embodiments, the piezoelectric layer L2 comprises aluminum nitride. In certain embodiments, the electric layer L1 is the top electrode of the resonator 100.

[0116] Fig. 2 schematically shows a top view (from above, from up to down) of an example resonator demonstrating an example structure thereof according to an example embodiment. In certain embodiments, the resonator 100 comprises a plurality of resonating elements 101.

[0117] The resonator 100 according to embodiment shown in Fig. 2 comprises a plurality of resonating elements 101 having a length L and a width W. In certain embodiments, the resonating elements 101 are beam elements (beam-shaped). In the embodiment shown in Fig. 2, the resonator 100 comprises seven resonating elements 101 (the number of elements 101 may vary depending on the embodiment). In certain embodiments, the resonating elements 101 are longer L than they are wide W. In certain embodiments, the coordinate system is selected so that the x-axis resides in the width direction W of the resonating elements 101 and the y-axis in the longitudinal direction L of the resonating elements 101.

[0118] According to the example embodiment shown in Fig. 2, the plurality of resonating elements 101 are positioned adjacent to each other. In certain embodiments, the plurality of resonating beam elements 101 form a ladder-like configuration (stacked beam resonator). In certain embodiments, the plurality of resonating beam elements 101 are positioned adjacent to each other in a width direction thereof. The adjacent resonating beam elements

[0119] 100 are mechanically connected to each other.

[0120] In certain embodiments, the resonator 100 is formed of the plurality of resonating elements

[0121] 101 and a plurality of connection elements 102. In certain embodiments, said adjacent resonating elements 100 are mechanically connected to each other by connection elements

[0122] 102 (such as two connection elements 102). In certain embodiments, the adjacent resonating elements 101 are separated by trenches 104. In certain embodiments, the trenches 104 have a length TL (trench length). In certain embodiments, the length L of the beam element 101 comprises at least the length of the trench TL and the length of at least one connection element 102.

[0123] In certain preferred embodiments, the resonator 100 is a stacked beam resonator comprising a plurality of resonating beam elements 101 positioned side-by-side in a plane, separated by trenches 104 and connected by connection elements 102. In at least some stacked beam resonators, the resonating beam elements 101 are positioned in the same plane. In certain stacked beam resonators, no two resonating beam elements 101 are positioned atop each other.

[0124] In certain embodiments, the resonating elements 101 of the resonator 100 are arranged in a rectangular array configuration. In certain embodiments, the resonator has a length L (which is equal to the length of the beam element). In certain embodiments, the resonator has a width RW (resonator width).

[0125] In certain embodiments, the resonator 100 is attached to a support structure (support structure not shown in Fig. 2. In Figs. 3a and 3b, for example, the support structure is shown as numeral 110). In certain embodiments, the resonating element 101 is suspended to the support structure via an anchoring point 103a / 103b. In certain embodiments, the resonating element 101 is suspended to the support structure via more than one anchoring point 103a / 103b, such as two anchoring points 103a / 103b. In certain embodiments, the resonating element 101 is attached to the support structure 110 from the outermost resonating beam elements by anchoring point(s) 103a / 103b. In certain embodiments, the anchoring points 103a / 103b are connected to respective electrical terminal. In certain embodiments, the resonating element is separated from the support structure 110 by (an external) trench 104’.

[0126] In certain embodiments, the resonator 100 is of an elongated shape (having the length L smaller than their width RW). In certain embodiments, the resonator 100 is in the shape of a rectangle (the resonator 100 has a shape of a rectangle). In certain embodiments, the resonator 100 has an aspect ratio (ratio of length L to width RW, when observed from above) different from 1. In certain embodiments, the resonator 100 has a length-to-width, L-to-RW, aspect ratio of less than 1 .

[0127] In certain embodiments, the resonating beam elements 101 are of an elongated shape (having their length L larger than their width W). In certain embodiments, each resonating beam element 101 is in the shape of a rectangular beam (beam-shaped). In certain embodiments, each resonating beam element 101 has an aspect ratio (ratio of length L to width W, when observed from above) different from 1. In certain embodiments, each resonating beam element 101 has a length-to-width, L-to-W, aspect ratio of more than 1. In certain example embodiments, each resonating beam element 101 has a length-to-width, L-to-W, aspect ratio of more than 2, such as 5, 8, or 10.

[0128] In certain embodiments, the resonator 100 is a megahertz frequency microelectromechanical systems, MEMS, resonator. In certain embodiments, the resonator 100 is configured to resonate in an in-plane length-extensional, LE, resonance mode.

[0129] In certain embodiments, the longitudinal axis L of a resonating element (or all resonating elements) 101 is aligned with <100> crystal direction of the silicon (of the bottom electrode), such as aligned with

[0100] crystal direction of silicon (of the bottom electrode), or deviates less than 25 degrees therefrom, or less than 15 degrees therefrom in certain embodiments. In certain preferable embodiments, the longitudinal axis L of the resonating element (or all resonating elements) 101 is aligned with <100> crystal direction of the silicon (of the bottom electrode), such as aligned with

[0100] crystal direction of the silicon (of the bottom electrode), or deviates less than 5 degrees therefrom, or less than 2 degrees therefrom in certain embodiments.

[0130] Figs. 3a, 3b, 3c, 3d, and 3e schematically show an electric layer configuration of an example beam resonator according to example embodiments. What is disclosed in the context of the example beam resonator of Fig. 2, applies also herein.

[0131] As shown in Figs. 3a, 3b, 3c, 3d, and 3e, in certain embodiments, the electric layer of the resonating element 101 covers the surface of resonating beam elements and the surface of connection elements 102 within the resonating element 101. In certain embodiments, the resonating element 101 comprises a plurality of cuts 201 through the electric layer thereof to deactivate portions of the resonating element 101. In certain embodiments, the cuts 201 are located in the area of the resonating beam elements, and / or in the area of the connection elements 102. In certain embodiments, the cuts 201 reach from a trench 104 / 104’ to another trench 104 / 104’.

[0132] As shown in Fig. 3a, in certain embodiments, the cuts 201 are symmetrically (such as mirror symmetry) arranged on the resonating element 101. As shown in Fig. 3b, in certain alternative embodiments, the cuts 201 are asymmetrically arranged on the resonating element 101. In certain embodiments, the plurality of cuts 201 through the electric layer are configured to deactivate (the cuts 201 deactivate) some of the resonating beam elements (entirely), such as shown in Figs. 3a and 3b. In certain embodiments, the cuts 201 deactivate a subset of the resonating beam elements. In certain embodiments, the resonating element 101 comprises a first group of resonating beam elements and a second group of resonating beam elements, wherein the first group of resonating beam elements is deactivated by cuts 201 in the electric layer, and the second group of resonating beam elements remains active within the resonating element 101.

[0133] In certain embodiments, as shown in Figs. 3a and 3b, the cuts 201 are located at the connection element 102 (at the area of the connection elements 102). In certain embodiments, the cuts 201 are vertically oriented, reaching from the trench 104 separating the resonating beam elements from one another to the external trench 104’.

[0134] In certain embodiments, the resonator 100 comprises two anchoring points 103a / 103b. In certain embodiments, the anchoring points 103a / 103b are connected to an electrical terminal (not shown). As shown in Fig. 3a, the anchoring points 103a / 103b are electrically connected to each other by an electrical connector 105. In certain embodiments, the electrical connector 105 is configured to provide a path for charge carriers towards the electrical terminal. In certain embodiments, the electrical connector 105 comprises electrically conductive material. In certain embodiments, the electrical connector 105 electrically connects the anchoring points 103a / 103b to each other. An analogous electrical connector 105 connecting each anchoring point is present in all the embodiments of Figs. 3b, 3c, 3d, and 3e (as well as Fig. 4a), even though it is not explicitly drawn therein.

[0135] In certain embodiments, as shown for example in Fig. 3b, the cuts 201 are configured to deactivate one anchoring point 103a / 103b of the resonator 100 (in addition to resonating beam(s) being deactivated due to cuts 201). In the embodiment shown in Fig. 3b, the cuts 201 deactivate the leftmost resonating beam element and the anchoring point 103a.

[0136] In certain embodiments, no electric field (current, charge carriers) is applied between the electric layer (the top electrode) and the bottom electrode for the leftmost beam element and the anchoring point 103a. In other words, the ‘deactivation’ of the portion refers to the lack of electric current in between the top electrode layer (the electric layer) and the bottom electrode layer. In certain embodiments, the bottom electrode within the region of the anchoring point 103a is coupled to an electrical terminal (the deactivated portion). In certain embodiments, the electric layer (the top electrode layer) is not coupled to an electric terminal within the (deactivated) region of the anchoring point 103a. In accordance with certain embodiments, the electric layer is floating (within the deactivated portion / region / area). According to certain embodiments, the leftmost beam element and the anchoring point 103a are inactive due to the electric layer (the top electrode layer) being floating.

[0137] In this embodiment, the five right side resonating beam elements and the other anchoring point 103b remain active. In the active portion (region / area) of the resonating element 101 , the electric field (current, charge carriers) is applied between the electric layer (the top electrode) and the bottom electrode (as usual).

[0138] When a portion of the resonating element 101 (such as a resonating beam element, or an anchoring point) is deactivated, said portion becomes disconnected from an (one, the) electrical terminal of the resonator 100 in accordance with certain embodiments. When said disconnection occurs, the electric current (or charge carriers) is prevented from moving into (and from) said electrical terminal.

[0139] Accordingly, as used herein, the deactivation of the anchoring point(s) 103a / 103b should be understood as the electric connection of the electric layer (top electrode layer) of said anchoring point 103a / 103b is disconnected (disabled, cut, broken). Thus, in accordance with certain embodiments, the electric layer (top electrode) of the anchoring point 103a / 103b is no longer connected to (coupled to) the respective electrical terminal thereof. In certain embodiments, the bottom electrode within a deactivated portion (region, area) of the resonating element 101 is coupled to the electrical terminal. In certain embodiments, the electric layer (the top electrode layer) is not coupled to an electric terminal within the deactivate portion (region, area) of the resonating element 101. According to certain embodiments, in the deactivated portion (region / area), the electric layer (the top electrode layer) is floating (no electric current passes into the electric layer).

[0140] As shown in Figs. 3c, 3d, and 3e, in certain embodiments, the cuts deactivate parts of the resonating element 101. In certain embodiments, cuts 201 are configured to deactivate parts of the resonating beam elements (but not an entire resonating beam element).

[0141] In the embodiment shown in Fig. 3c, the cuts 201 travel horizontally (in x-direction) from one trench 104 to another trench 104. In certain embodiments, as shown in Fig. 3c, the cuts 201 deactivate the resonating beam elements that are second from the left, and second from the right. In this embodiment, both anchoring points 103a / 103b and all the connection elements 102 remain active.

[0142] In the embodiment shown in Fig. 3d, the cuts 201 deactivate a peripheral area of the resonating element 101. In certain embodiments, the cuts 201 are horizontally oriented. In certain embodiments, the cuts 201 are non-centered in view of the resonating element 101 width (middle axis of the resonating element 101 width). In this embodiment, the cuts 201 deactivate the peripheral areas of all the resonating beam elements, and the connection elements 102 in between said resonating beam elements in that area. In Fig. 3d, the deactivated area is in the lower part (in y-direction) of the resonating element 101. In this embodiment, both anchoring points 103a / 103b remain active.

[0143] In certain embodiments, as shown in Fig. 3e, the electric layer of the resonating element 101 comprises both vertically oriented and horizontally oriented cuts 201. In certain embodiments, the cuts 201 are arranged in the peripheral areas of the resonating element 101.

[0144] In certain embodiments, the resonating beam elements comprise deactivated ends (peripheral regions at the ends of the resonating beam elements). In this embodiment, the cuts 201 are configured to deactivate a peripheral region of every other resonating beam element. In certain embodiments, the cuts 201 deactivate peripheral regions of every other resonating beam element such that some of the deactivated peripheral regions are located at an opposite side of the resonating element 101 in comparison to some of the deactivated peripheral regions. As shown in Fig. 3e, in certain embodiments, the resonating element 101 has deactivated corners. In certain embodiments, the resonating element 101 (or the resonating beam element) is partially deactivated. In certain embodiments, the resonating element 101 (or the resonating beam element) comprises partial deactivation.

[0145] In the embodiment shown in Fig. 3e, both anchoring points 103a / 103b and every other resonating beam element remain active.

[0146] Figs. 4a, 4b, 4c and 4d schematically show examples of a resonator array having two resonators 100 with electric layer configuration according to example embodiments. What is above disclosed in context of Figs. 2, 3a, 3b, 3c, 3d, and 3e, apply also herein for the applicable parts. All embodiments described before in context a single resonator 100 apply herein as well for the resonators 100 of the apparatus. Herein is provided an apparatus, such as a resonator array, comprising at least one resonator 100 in accordance with certain embodiments. In certain embodiments, as shown Figs. 4a, 4b, 4c and 4d, the apparatus comprises (at least) two resonators 100. In certain embodiments, the resonators 100 are stacked beam resonators, having a plurality of adjacent resonating beam elements adjacent to each other (side by side), each being connected to another resonating beam element by (at least two) connection elements and the resonating beam elements being separated by trenches 104. In certain embodiments, the apparatus comprises a plurality of resonators 100 positioned adjacent to each other. In certain embodiments, the apparatus comprises a plurality of resonators 100 coupled to each other by a coupler 310. In certain embodiments, the electric layer covers the coupler 310. In certain embodiments, the coupler 310 comprises a layer of gold (as the topmost layer thereof).

[0147] In certain embodiments, the two resonators 100 coupled to each other by a flexural coupler 310 In certain embodiments, the two resonators 100 coupled to each other by a rigid coupler 310 (not shown in Figs. 4a, 4b, 4c and 4d). In certain embodiments, the two resonators 100 coupled to each other by a length-extensional mode coupler 310 (not shown in Figs. 4a, 4b, 4c and 4d).

[0148] Fig. 4a schematically shows a resonator array having two resonators 100, the resonators 100 having analogous characteristics with the resonator of Fig. 3c. The apparatus shown in Fig. 4a comprises two (length) extensional-mode resonators 100, and a (one or more) flexural mode resonator coupler 310, in accordance with certain embodiments. Further, the apparatus comprises a (one or more) mechanical connector element 320 which connects the flexural resonator coupler 310 to the extensional mode resonators 100. In certain embodiments, at least one of the extensional-mode resonators 100 of the apparatus comprises a piezoelectric thin-film actuator for exciting the said extensional-mode resonator to a resonance mode and thereby the whole apparatus to a collective resonance due to mechanical coupling of the extensional-mode resonators 100.

[0149] In certain embodiments, as shown in Fig. 4a, the apparatus comprises cuts 201 in the electric layer of the resonating elements. In certain embodiments, the cuts 201 deactivate portions of the resonating elements 101 , such as portions of the resonating beam elements. In the embodiment shown in Fig. 4a, the anchoring points 103a / 103b, the connection elements 102 and the coupler 310 remain active. Fig. 4b schematically shows a resonator array having two resonators 100, the resonators 100 having analogous characteristics with the resonator of Fig. 3d. As shown in Fig. 4b, in certain embodiments, the peripheral areas of the resonating elements 101 (the beam ends) are deactivated by the cuts 201. In certain embodiments, the central area of the apparatus (including the coupler 310) is deactivated by the cuts 201. In the embodiment shown in Fig. 4b, part of the connection elements 102 (the connection elements 102 on the coupler’s 310 side of each resonating element 101) and the coupler 310 are deactivated by the cuts 201. In the embodiment shown in Fig. 4b, the anchoring points 103a / 103b remain active.

[0150] In certain embodiments, the cuts 201 are symmetrically (such as mirror symmetry) arranged on the resonators 100 of the apparatus. In certain embodiments, the cuts 201 are symmetrically (such as mirror symmetry) arranged on each side of the coupler 310 (the coupling area), as shown for example in Figs. 4b, and 4c. In certain alternative embodiments, the cuts 201 are asymmetrically arranged on the resonators 100 (with respect to each other, on each side of the coupler 310).

[0151] Fig. 4c schematically shows an embodiment of the apparatus, wherein every other resonating beam element is deactivated by cuts 201. In this embodiment, the cuts 201 are horizontal cuts. In certain embodiments, the cuts 201 go from one trench 104 to another trench 104, thereby disconnecting every other resonating beam element. In certain embodiments, the resonating element 101 comprises cuts 201 in alternating ends of the resonating beam elements.

[0152] In the embodiment shown in Fig. 4c, part of the connection elements 102 (the connection elements 102 on the coupler’s 310 side of each resonating element 101) and the coupler 310 are deactivated by the cuts 201. In the embodiment shown in Fig. 4c, the anchoring points 103a / 103b remain active.

[0153] Fig. 4d schematically shows a resonator array having two resonators 100, the resonators 100 having analogous characteristics with the resonator of Fig. 3e. In the embodiment shown in Fig. 4d, the resonating elements 101 comprise a plurality of deactivated regions. In certain embodiments, the deactivated regions are located at the ends of the resonating beam elements.

[0154] In certain embodiments, the apparatus comprises cuts 201 on the coupler 310. In certain embodiments, the apparatus comprises cuts 20T at the point wherein the coupler is connected to the resonating elements 101 , such as shown in Fig. 4d. As shown in Fig. 4d, the coupler 310 is deactivated by the cuts 20T in accordance with certain embodiments. In the embodiment shown in Fig. 4c, the anchoring points 103a / 103b remain active.

[0155] In certain embodiments, (all, a plurality of, part of) the resonators 100 of an apparatus are identical with one another (each other). In certain alternative embodiments, (all, a plurality of, part of) the resonators 100 of an apparatus are different from one another.

[0156] The resonator 100 according to the embodiments of the present disclosure is not limited to number, width, shape and / or angle of the cuts 201. In certain embodiments, cuts 201 are of different number, width, shape and / or angle along the electric layer of the resonating element 101. In certain embodiments, the cuts 201 are of different number, width, shape and / or angle within the electric layer of the connection elements 102 and / or the resonating beam elements. In certain embodiments, the cuts 201 (such as the number, location, and / or orientation thereof) are a parameter for optimization in general. In certain embodiments, cuts 201 are a parameter for optimization for the resonator 100 design.

[0157] Figs. 5a and 5b schematically show examples of the electric layer configuration having a plurality of cuts according to an example embodiment. Fig. 5a shows a single-ladder embodiment, whilst the Fig. 5b shows a double-ladder embodiment.

[0158] As shown in Figs. 5a and 5b, in certain embodiments, the resonator 100 comprises two cuts 201. In certain embodiments, the cuts 201 are arranged in the proximity of the resonating element 101 edge (close to a trench 104’). In certain embodiments, the cuts 201 are arranged in opposite sides of the resonating element 101. In certain embodiments, the cuts 201 are not equally distant from the resonating element 101 edge. In certain embodiments, one cut 201 crosses the trenches 104 (in between the resonating beam elements) within the resonating element 101. In certain alternative embodiments, the cuts 201 are equally distant from the resonating element 101 edges.

[0159] In this embodiment, the cuts 201 deactivate the peripheral areas of all the resonating beam elements, and the connection elements 102 in between said resonating beam elements in that area. In the embodiment shown in Fig. 5b, the coupler 310 is additionally deactivated.

[0160] Figs. 6a and 6b schematically show examples of the electric layer configuration having a meandering cut according to an example embodiment. Fig. 6a shows a single-ladder embodiment, whilst the Fig. 6b shows a double-ladder embodiment. In certain embodiments, the resonating element 101 comprises a cut 201. In certain embodiments, the resonating element 101 comprises more than one cut 201 , such as two cuts 201 , as shown in Figs. 6a and 6b. Similarly as in Figs. 5a and 5b, the cut(s) 201 are arranged in the proximity of the long edge (x-directional edge) of the resonating element 101 in the embodiments shown in Figs. 6a and 6b.

[0161] In certain embodiments, such as shown in Figs. 6a and 6b, the cut 201 is non-straight. In certain embodiments, the cut 201 is a meandering cut. In certain embodiments, the cut is bendy (curvy, wavy) cut. As shown in Figs. 6a and 6b, the meandering cuts 201 protrude from the edge of the resonating element 101 towards the middle of the resonating element 201 (in each meander).

[0162] Fig. 7 schematically shows an example of the electric layer configuration that combines the embodiments shown in Figs. 5a / 5b and 6a / 6b. Fig. 7 shows a single-ladder embodiment, wherein the electric layer comprises a straight and a meandering cut according to an example embodiment. It should be noted that the embodiment is equally applicable to the double-ladder embodiment as well.

[0163] In certain embodiments, the resonating element 101 (the electric layer thereof) comprises both a straight and a non-straight (meandering) cut 201. In certain embodiments, the straight cut 201 may be similar as disclosed, for example, in the context of Figs. 5a and 5b.

[0164] In certain embodiments, the straight cut 201 is arranged in the proximity of the resonating element 101 edge. In certain embodiments, the straight cut 201 is displaced from the resonating element 101 edge by a length, which is 10-30% of the resonating element’s 101 width. In certain embodiments, the straight cut 201 is displaced from the resonating element 101 edge by a length, which is approximately 20% of the resonating element’s 101 width.

[0165] In certain embodiments, the non-straight cut 201 is arranged in the proximity of the resonating element 101 edge. In certain embodiments, the non-straight cut 201 is displaced from the resonating element 101 edge by a length, which is 1-10% of the resonating element’s 101 width (measured from the part of the cut 201 which is closest to the resonating element 101 edge). In certain embodiments, the non-straight cut 201 is displaced from the resonating element 101 edge by a length, which is approximately 5% of the resonating element’s 101 width. Fig. 8 schematically shows an enlarged view of a cut 201 and the path of the current (charge carriers, electricity) C according to an example embodiment. In certain embodiments, the current runs on the active portion of the resonating element 101 (and not on the deactivated portion of the resonating element). In certain embodiments, the electrical current C follows the same (similar) shape as the cut 201. This is shown in Fig. 8 as the dashed lines with arrows.

[0166] Without limiting the scope and the interpretation of the patent claims, certain technical effects of one or more of the example embodiments disclosed herein are listed in the following. A technical effect is to provide a solution having reduced drive level dependency and good power handling capacity. A technical effect of the instant solution is providing a solution with a low capacitance value, whilst maintaining the resistance of the apparatus at an acceptable level. Typically, when the aim is to reduce capacitance of the apparatus, the resistance value of the apparatus does not remain at an acceptable level.

[0167] A further technical effect of the present solution is providing a small resonator. This is at least in contrast to the conventional solution of providing a ‘bigger’ resonators when aiming to improve their power handling capacity. The more the resonator cross-section increases, the better the power handling. However, the instant solution enables providing the improved power handling without increasing the size or the cross-section of the resonator.

[0168] According to certain embodiments of the present disclosure, the improved power handling is provided, whilst simultaneously enabling maintaining low capacitance by deactivating some regions of the resonator by providing the top electrode thereof floating. The bottom electrode of the resonator remains connected. Thus, said ‘floating’ regions of the top electrode contribute mechanically but not electrically within the resonator.

[0169] Further, a technical effect is maintaining the equivalent series resistance, ESR, at an optimal level. A further technical effect is improving frequency over temperature (f-vs-T) characteristics while retaining low ESR. A further technical effect is increasing or maintaining the quality factor, Q.

[0170] A further technical effect is enabling using the otherwise typical manufacturing process of the apparatus. By way of examples, the instant solution does not require change of doping concentration, or change in crystal orientation of the substrate. A further technical effect is enabling re-purposing the design of the resonator according to the present solution for various customer specifications. Therefore, the instant solution enables providing the desired / improved capacitance vs. resistance performance, whilst simultaneously providing reduced drive level dependency and using the already existing technology / platform.

[0171] Various embodiments have been presented. It should be appreciated that in this document, words comprise, include, and contain are each used as open-ended expressions with no intended exclusivity.

[0172] The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention.

[0173] Furthermore, some of the features of the afore-disclosed example embodiments may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.

Claims

CLAIMS1 . A resonator (100), comprising a resonating element (101) having an electric layer, wherein the resonating element (101) comprises a cut (201) through the electric layer to deactivate a portion of the resonating element (101).

2. The resonator (100) of claim 1 , wherein the cut (201) extends from trench (104, 104’) to trench (104, 104’).

3. The resonator (100) of claim 1 or 2, wherein the cut (201) is a discontinuity region of the electric layer, configured to prevent charge carriers from crossing it.

4. The resonator (100) of any of the preceding claims, wherein the electric layer of the resonating element (101) comprises a plurality of cuts (201) through the electric layer to deactivate portions of the resonating elements.

5. The resonator (100) of any of the preceding claims, wherein the electric layer comprises metal, preferably gold.

6. The resonator (100) of any of the preceding claims, wherein the resonating element (101) comprises a piezoelectric layer (L2), wherein the electric layer (L1) is on the piezoelectric layer (L2), and a bottom electrode (L3 / L4) on the opposite side of the piezoelectric layer (L2) than the electric layer (L1).

7. The resonator (100) of claim 6, wherein the bottom electrode (L4) comprises silicon, preferably doped silicon, such as ultra-heavily doped, UHD, silicon.

8. The resonator (100) of any of the preceding claims, wherein the resonating element (101) comprises a plurality of resonating beam elements side by side in a plane, connected to one another by connection elements (102) and separated from one another by trenches (104).

9. The resonator (100) of claim 8, wherein the resonating beam elements are longitudinally aligned within 25 degrees of a <100> crystal direction of silicon.

10. The resonator (100) of any of the preceding claims, wherein the resonating element (101) is configured to resonate in a length-extensional, LE, resonance mode.

11. The resonator (100) of any of the preceding claims, wherein the resonator (100) is a microelectromechanical systems, MEMS, resonator.

12. The resonator (100) of any of the preceding claims, wherein the cut (201) is a nonstraight cut, such as a meandering cut.

13. The resonator (100) of any of the claims 1-11, wherein the cut (201) is a straight cut.

14. The resonator (100) of claim 13, wherein the straight cut (201) is displaced from the resonating element’s edge by a length, which is 10-30% of the resonating element’s width.

15. An apparatus, such as a resonator array, comprising at least one resonator (100) according to any of claims 1-14.

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