Zt-quartz resonator and manufacturing method thereof

Abstract

One aspect of the invention relates to a resonator, comprising: - a resonator plate having a thickness and a surface having a maximum length and width, wherein the resonator plate is ZT-cut quartz; and - a frame including a C-shaped portion, the C-shaped portion including a first arm and a second arm extending at least partially around the lateral edge of the resonator plate, and wherein each of the first arm and the second arm is cantilevered to the resonator plate.

Description

[Technical Field]

[0001] This invention relates to a miniature quartz resonator made of ZT-cut quartz, which is configured to oscillate along the edge of a plate in a length-extension profile mode. [Previous Technology]

[0002] The ZT quartz resonator has been described in known technical documents such as FR2435855, FR2521782, and FR2634067.

[0003] The cut angle of the ZT resonator is selected to achieve a zero first-order frequency-temperature coefficient and negligible coupling with the surface shear mode and the stretching mode along the other edge of the plate. Different ZT cuts with similar characteristics can be obtained through the following steps: first, rotate by an angle ψ around the Z-axis, then rotate by an angle ɸ around the X'-axis, and, if necessary, rotate by an angle θ around the Z'-axis perpendicular to the plate plane. A common cut is to set ψ = 90˚, in which case the second rotation will be an ɸ = 26.5˚ rotation around the X'=Y axis, and then a θ = 20˚ rotation around the Z'-axis. This cut is called ZTY. The simplest cut in the ZT series may be a single rotation of ɸ = 24˚ around the X-axis; this cut is called ZTX.

[0004] By correctly selecting the aspect ratio of the board, the second-order temperature coefficient also becomes zero due to the residual coupling between the (stretched) modes. Therefore, a third-order frequency-temperature characteristic is obtained. The third-order temperature coefficient is approximately twice as small as that of an AT-cut resonator. Furthermore, for a given frequency, ZT can be significantly smaller than AT.

[0005] For the typical size of ZT, its resonance falls between 1 and 20 MHz.

[0006] Because the contour pattern is highly sensitive to its surroundings, the manufacturing process must ensure precise control over the shape. Furthermore, the anchoring method must be handled with extreme care. Anchors hold the resonator in place while ensuring good decoupling from the package to maintain the high quality factor and excellent thermal performance of the ZT resonator.

[0007] In previous implementations, the fixing method was achieved by means of a resonant arm, which minimizes mode interference (Figure 1). However, the geometry of the fixing structure is also very critical.

[0008] Figure 1 shows an example of a conventional ZT-cut quartz resonator 100, which includes a first resonator plate 101 and a second resonator plate 102 connected together by a resonant arm 103. The resonant arm 103 is connected to a mounting portion 104 via a suspension arm 105. Each of the first resonator plate 101, the second resonator plate 102, the resonant arm 103, the mounting portion 104, and the suspension arm 105 is coplanar. A first electrode (not shown) is provided on one side of each resonator plate, while a second electrode (not shown) is provided on the opposite side of each resonator plate, wherein both electrodes are electrically coupled to an AC electric field generator (not shown). The first and second electrodes are designed and arranged to generate oscillations of the two resonator plates in their width direction, as indicated by the dashed arrows. The two resonator plates are balanced on both sides of the resonant arm and the mounting portion. The mounting portion is disposed between the two resonator plates to minimize the width of the resonator. Because there are two resonator plates connected by a resonant arm, the resonator length 106 can be relatively long, for example, 3850 μm, while the width 107 of the resonator plate is also relatively long, for example, 2024 μm.

[0009] There is a need to miniaturize ZT-cut quartz resonators, but miniaturization is limited by the complex design of these resonators, which is difficult to fabricate in smaller sizes. Furthermore, the resonant arms and support arms must be sufficiently wide to withstand the mechanical constraints imposed by the bulky resonator plate. The symmetry of the resonant structure must be well controlled to minimize energy loss, thereby reducing damping in the mounting section. [Summary of the Invention]

[0010] The present invention aims to provide an alternative design for ZT-cut quartz resonators that overcomes the challenging limitations associated with miniaturization of such resonators.

[0011] According to the first state, the resonator includes: - a resonator plate having a thickness and a surface having a maximum length and width, wherein the resonator plate is ZT-cut quartz; and - a frame including a C-shaped portion, the C-shaped portion including a first arm and a second arm extending at least partially around the lateral edge of the resonator plate, and wherein each of the first arm and the second arm is cantilevered to the resonator plate.

[0012] It is defined as a node plane orthogonal to the surface of the resonator plate and passing through the central longitudinal axis of the resonator plate, wherein the cantilever passes through the node plane.

[0013] Preferably, the resonator plate is configured to oscillate on both sides of the node plane in its width direction, and the C-shaped portion of the frame is spaced apart from the resonator plate to prevent the resonator plate from contacting the frame when the resonator plate oscillates, and to ensure that the plate is decoupled from the frame.

[0014] Preferably, the resonator board includes at least two electrodes that are separated from each other and electrically coupled to mounting pads disposed on a frame, the electrodes being positioned between at least two surfaces of the resonator board on both sides of the node plane to generate an electric field.

[0015] Preferably, the first electrode and the second electrode are disposed on the resonator plate so that when the first electrode and the second electrode are coupled to an AC voltage, an alternating electric field is generated between the two electrodes, thereby causing the resonator plate to provide alternating deformation along its width direction.

[0016] Preferably, the first cantilever extends from the first side of the resonator plate to the first arm of the C-shaped portion of the frame, and the second cantilever extends from the second side of the resonator plate to the second arm of the C-shaped portion of the frame.

[0017] Preferably, the cantilever, resonator plate and frame are integrally formed.

[0018] Preferably, the resonator plate has a maximum length, a lateral edge and a longitudinal edge, and the maximum length is at the farthest distance from the node plane on both sides of the node plane, or at a distance close to the longitudinal edge.

[0019] Preferably, the resonator plate includes a shortest length extending to a position between: - a first corner portion formed between a first cantilever and a first lateral edge of the resonator plate; and - a second corner portion formed between a second cantilever and a second lateral edge of the resonator plate.

[0020] Preferably, the shortest length is at least 90% of the maximum length, more preferably at least 95% of the maximum length, and even more preferably at least 99% of the maximum length.

[0021] Preferably, the shortest length is on both sides of the node plane.

[0022] In some embodiments, the transverse edge located between the first end near the cantilever and the second end near the longitudinal edge forms an angle of inclination of 10˚ or less, preferably 5˚ or less, relative to an axis orthogonal to the node plane.

[0023] Preferably, the resonator plate is substantially symmetrical with respect to its central longitudinal axis (i.e., via the node plane) and with respect to its intermediate width axis (i.e., orthogonal to the node plane).

[0024] Preferably, the frame has a frame thickness such that the resonator thickness is between 25% and 100% of the frame thickness, more preferably between 25% and 75%, and even more preferably between 25% and 50%.

[0025] Preferably, the maximum length of the resonator plate is less than or equal to 3000µm, more preferably 2000µm or less, more preferably less than or equal to 1000µm, and even more preferably less than or equal to 600µm.

[0026] Preferably, the length of the cantilever is from 10µm to 300µm, more preferably from 20µm to 150µm, and even more preferably from 50µm to 100µm.

[0027] The width of the cantilever is preferably 20% or less of the width of the resonator plate.

[0028] The thickness of the cantilever is between 50% and 150% of the thickness of the resonator plate.

[0029] Preferably, the resonator plate has a maximum width such that the (width) / (maximum length) ratio is between 0.4 and 0.8, more preferably between 0.5 and 0.7.

[0030] Preferably, the frame includes a mounting portion, which includes a first mounting pad and a second mounting pad respectively coupled to the first electrode and the second electrode.

[0031] Preferably, the maximum length of the frame is less than or equal to 4000 µm, more preferably less than or equal to 2500 µm, and even more preferably less than or equal to 1500 µm.

[0032] Preferably, the maximum thickness of the frame TF is less than or equal to 200µm, more preferably less than or equal to 150µm, and even more preferably less than or equal to 120µm.

[0033] According to the second embodiment, the present invention relates to a method for manufacturing a resonator as described above, wherein the method includes the following steps: - providing a ZT-cut wafer; - defining a resonator shape arrangement location on the wafer, wherein the resonator shape arrangement location includes a resonator frame shape arrangement location, a resonator plate shape arrangement location, and a cantilever shape arrangement location, wherein the cantilever shape arrangement location is located on a central longitudinal axis along the resonator plate shape arrangement location, and connecting the lateral side of the resonator plate shape arrangement location to the resonator frame shape arrangement location; - etching a portion of the wafer to obtain the outline of a resonator plate, the resonator plate having cantilevers on its lateral sides, and such that the cantilever remains integrally formed with the resonator frame; - depositing: ○ at least two separate electrodes on the resonator plate, such that the first electrode has a main portion disposed on one side of a plane passing through the cantilever, and the second electrode has a main portion disposed on the other side of a plane passing through the cantilever; ○ two mounting pads on the resonator frame arrangement location, and; ○ connecting rails that connect each electrode to a corresponding mounting pad, and; - The outline of the resonator frame placement location is etched to obtain the resonator.

[0034] In one embodiment of the manufacturing method, the method includes the following steps: - applying a first mask to the surface of the wafer to cover a first surface intended to form a frame having a C-shaped portion, leaving a portion of the surface of the wafer uncovered to form a thinner planar portion of the wafer; - chemically wet etching the uncovered surface of the wafer to obtain the thinner planar portion; - applying a second mask to the planar portion, wherein the second mask has the shape of a resonator plate having cantilever extending from the resonator plate shape to the C-shaped portion of the frame; - chemically wet etching the remaining uncovered surface of the wafer to form the outline of the resonator plate and the cantilever.

[0035] In an alternative embodiment, the method of manufacturing the resonator further includes the following steps: - applying a first mask to the surface of the wafer to cover a first surface of a frame to be formed having a C-shaped portion, leaving a portion of the surface of the wafer uncovered to be formed a thinner planar portion of the wafer; - chemically wet etching the uncovered surface of the wafer to obtain the thinner planar portion; - cutting the contour of the resonator plate with a femtosecond laser or deep reactive ion etching (DRIE) such that cantilevers extend from the resonator plate to the C-shaped portion of the frame.

[0036] In an alternative embodiment, the step of etching a portion of a wafer to obtain the outline of a resonator board having cantilevered sides on two lateral sides and such that the cantilevered sides remain integrally formed with the resonator frame is performed by cutting with a femtosecond laser or with deep reactive ion etching (DRIE).

Implementation Method

[0039] The invention will now be described in more detail with the support of Figures 2 and 3, which show an embodiment of the resonator 200, comprising: - a resonator plate 201 having a thickness TR and a surface SR having a lateral edge and a longitudinal edge, a maximum length LR1 and a width WR, wherein the resonator plate 201 is ZT-cut quartz; - a frame 202 including a C-shaped portion 203 including a first arm 204 and a second arm 205 extending at least partially around the lateral edge of the resonator plate, wherein each arm 204, 205 is connected to the resonator plate by cantilevers 206a, 206b.

[0040] Advantageously, the frame is made of quartz. Preferably, the cantilever is also made of quartz. For ease of manufacture, the entire resonator 200 is integrally formed from a single ZT-cut quartz wafer. A certain number of resonators can be placed on each wafer. The shape of the resonator 200 can be obtained, for example, by chemical wet etching or by deep reactive ion etching, or by the method described in document WO 2013 / 092920, or by femtosecond laser-induced chemical etching as described by Linden et al. *Microsystems & Nanoengineering* (2023), Vol. 9: Paper 38.

[0041] Unless otherwise stated, the term "surface" in relation to a resonator plate refers to the largest surface on both sides of the resonator plate.

[0042] The term "C-shaped portion" refers to a part of a frame forming a C, wherein the portion preferably includes a sub-portion having a first end and a second end, the first end and the second end being connected to a first arm 204 and a second arm 205 pointing in the same direction, respectively. The sub-portion, the first arm, and the second arm are preferably straight. Preferably, the sub-portion forms a 90˚ angle with the first arm and the second arm.

[0043] A node plane 207 is defined, which is orthogonal to the surface SR of the resonator plate 201 and passes through the central longitudinal axis of the resonator plate 201, wherein cantilevers 206a and 206b pass through the node plane 207. The node plane 207 is a virtual plane orthogonal to the resonator plate, wherein the amplitude is at its minimum or zero when the resonator plate oscillates under the influence of an alternating electric field.

[0044] The resonator plate 201 is configured to oscillate on both sides of the node plane 207 in the direction of its width WR. In the context of this invention, the terms "oscillating," "oscillate," or "oscillation" refer to the change in shape of a plate made of quartz crystal with piezoelectric properties under an applied alternating electric field, such that the plate periodically extends and contracts along its width on both sides of the node plane.

[0045] The C-shaped portion 203 of the frame 202 is spaced apart from the resonator plate 201 to prevent the resonator plate 201 from contacting the frame 202 when the resonator plate 201 oscillates. Preferably, the C-shaped portion 203 of the frame is spaced at least 1µm from the plate, more preferably 10µm, 20µm, more preferably at least 50µm, and more preferably at least 75µm.

[0046] The resonator plate 201 includes at least a first electrode 208 and a second electrode 209, which are separated from each other and electrically coupled to a first mounting pad 210 and a second mounting pad 211 disposed on the frame 202, respectively. The electrodes are disposed between at least two surfaces of the resonator plate and on both sides of the node plane to generate an electric field.

[0047] The first electrode 208 and the second electrode 209 are disposed on the resonator plate so that when the first electrode and the second electrode are coupled to an AC voltage, an alternating electric field is generated between the two electrodes, thereby deforming the resonator plate along its width direction. The electrode configuration can be optimized to maximize piezoelectric coupling with the resonant mode while suppressing unwanted modes.

[0048] Figures 4a to 4f illustrate various possible configurations of the electrodes on the resonator plate 201. In Figure 4a, the first electrode 208 is located on a first side of the resonator plate 201 and partially covers the surface of the resonator plate on the first side of the node plane 207, while the second electrode 209 is located on the opposite side of the resonator plate 201 and partially covers the surface of the resonator plate on the second side of the node plane 207. The first electrode 208 and the second electrode 209 have opposite polarities.

[0049] In Figure 4b, the first electrode 208 is located on the first side of the resonator plate 201 and completely covers the surface of the resonator plate on the first side of the node plane 207, while the second electrode 209 is located on the opposite side of the resonator plate 201 and completely covers the surface on the second side of the node plane 207. The first electrode 208 and the second electrode 209 have opposite polarities.

[0050] In Figure 4c, a pair of first electrodes 208, 208' are located on both sides of the resonator plate 201 and partially cover the surface of the resonator plate on the first side of the node plane 207, while a pair of second electrodes 209, 209' are located on both sides of the resonator plate 201 and partially cover the surface of the resonator plate on the second side of the node plane 207. The pair of first electrodes 208, 208' have the same polarity and must be separated from the pair of second electrodes 209, 209' by a gap, and the two have opposite polarities relative to the pair of first electrodes 208, 208'.

[0051] In Figure 4d, the first electrode 208 is located on the first side of the resonator plate 201, completely covering the surface of the resonator plate on the first side of the node plane 207, and partially covering the surface of the resonator plate on the second side of the node plane 207. The second electrode 209 is located on the opposite side of the resonator plate 201, completely covering the surface on the second side of the node plane 207, and partially covering the surface on the first side of the node plane 207. The first electrode 208 and the second electrode 209 have opposite polarities.

[0052] In Figure 4e, the first electrode 208 extends from one side of the resonator plate to the other side of the resonator plate via a groove in the first side of the node plane 207, while the second electrode 209 extends from the first side of the resonator plate to the other side of the resonator plate via a corresponding groove in the other side of the node plane 207. The first electrode 208 and the second electrode 209 are separated from each other by a gap and have opposite polarities.

[0053] In Figure 4f, the first electrode 208 is located on the first side of the resonator plate 201 and partially covers the surface of the resonator plate on the first side of the node plane 207, while the second electrode 209' is located on the same side of the resonator plate 201 and partially covers the surface of the resonator plate on the second side of the node plane 207. The first electrode 208 and the second electrode 209' have opposite polarities. A similar configuration is obtained by placing the electrodes on the second side of the resonator plate 201.

[0054] The first mounting pad 210 and the second mounting pad 211 are configured to be coupled to the alternating electric field generator, i.e., the oscillator circuit.

[0055] In an alternative embodiment shown in FIG. 5, the piezoelectric assembly is mounted on at least one surface of the resonator plate 201 and extends on both sides of the node plane 207. The first piezoelectric assembly includes a first electrode 208" located on the surface of the resonator plate, a piezoelectric layer 214 located on the first electrode 208" and a second electrode 209" located on the piezoelectric layer 214. The first electrode 208" is coupled to a first mounting pad 210, while the second electrode 209" is coupled to a second mounting pad 211 with opposite polarity.

[0056] As shown in Figure 3, cantilever arms 206a and 206b are disposed on both sides of the resonator plate 201. The first cantilever arm 206a extends from the first arm 204 to the resonator plate 201, while the second cantilever arm 206b extends from the second arm 205 of the C-shaped portion 203 of the frame 202 to the resonator plate 201. The cantilever arms 206a and 206b are preferably integrally formed with the frame 202 and the resonator plate 201. The cantilever arms 206a and 206b and the resonator plate 201 may have a thickness TR equal to or less than the thickness TF of the frame 202. Preferably, the length of the cantilever arm is from 10µm to 300µm, more preferably from 20µm to 150µm, and even more preferably from 40µm to 100µm. The width of the cantilever arm is preferably 25% or less of the width of the resonator plate. The thickness of the cantilever arm is between 50% and 150% of the thickness of the resonator plate. In a preferred embodiment, the cantilever has a length of 40 μm to 100 μm, a width less than 20% of the width of the resonator plate, and a thickness of 80% to 120% of the thickness of the resonator plate, preferably about 100% of the thickness of the resonator plate.

[0057] The first electrode 208 or a pair of first electrodes 208, 208' is connected to the first mounting pad 210 via wiring or signal tracks passing through the first cantilever 206a and through the frame 202. The second electrode 209 or a pair of second electrodes 209, 209' is connected to the second mounting pad 211 via wiring or signal tracks passing through the second cantilever 206b and through the frame 202. The term "passing through" also includes passing through the surface of the cantilever or frame, and the wiring or signal tracks may optionally be insulated by a suitable insulating layer known to those skilled in the art.

[0058] The first electrode 208 or a pair of first electrodes 208, 208', and the second electrode 209 or a pair of second electrodes 209, 209' are disposed on the resonator plate 201 by partial metallization of the resonator plate, for example by chemical vapor deposition, physical vapor deposition, vacuum deposition, sputtering, or any other suitable method known to those skilled in the art. The electrodes may be made of any metal or alloy, such as, but not limited to, copper, zinc, chromium / gold, or platinum.

[0059] In order to minimize the coupling between the resonator and its external environment (frame, package), the thickness of the resonator plate 201 and the cantilever 206a, 206b is reduced relative to the frame.

[0060] The thickness TR of the resonator plate 201 may be between 25µm and 100µm, advantageously less than or equal to 75µm or less than or equal to 50µm.

[0061] The cantilever 206a and 206b may have the same thickness as the resonator plate 201.

[0062] The reduction in the thickness of the resonator plate 202 and the thickness of the cantilever 206a, 206b has the following advantages: - The thickness / width ratio of the plate 201 is reduced, which improves the modal shape and allows for a smaller footprint; - The moving mass is reduced relative to the frame 202, which reduces residual movement (touch effect) transmitted from the plate 201 to the frame 202; - Decoupling is improved due to the smaller cross-section of the cantilever 206a, 206b.

[0063] Although the cantilever arms 206a and 206b engage the resonator plate 201 at the node plane 207, they alter the effective shape of the resonator plate 201 and thus change its frequency-temperature characteristics. This can be compensated for by modifying the shape of the resonator plate 201 such that the resonator plate 201 includes a second length LR2 shorter than the maximum length LR1 of the resonator plate 201, the second length LR2 extending to a location near the location therebetween: - a first corner formed between the first cantilever and the first lateral edge of the resonator plate; and - a second corner formed between the second cantilever and the second lateral edge of the resonator plate.

[0064] In the context of this document, the term "proximate" refers to a distance of up to 25% of the shortest distance separating the cantilever from the lateral edge of the resonator plate.

[0065] The second length LR2 is preferably the shortest length of the resonator plate and is at least 90% of the maximum length LR1 of the resonator plate 201, preferably at least 95% of the maximum length LR1, and more preferably at least 99% of the maximum length LR1.

[0066] The resonator plate 201 is substantially symmetrical with respect to its intermediate width axis MW and with respect to its intermediate longitudinal axis (or node plane 207). "Substantially symmetrical" means that it may be necessary to make slight deviations from perfect geometric symmetry to compensate for minor asymmetric residues formed due to etching residues generated during anisotropic etching and chemical wet etching processes.

[0067] The maximum length LR1 of the resonator plate is advantageously located at or near the longitudinal edge of the resonator plate, for example, at a distance less than 10% of the width of the plate. In this context, the term "distance near the longitudinal edge" preferably refers to a distance of 50% or less of the distance separating the longitudinal edge from the node plane.

[0068] Examples of embodiments of a resonator plate with a cantilever are shown in Figures 6a to 6c. In Figure 6a, each corner of the plate and the corner between the lateral edge and the cantilever are sharp corners. In Figure 6b, the corners between the longitudinal edge and the lateral edge are chamfered. In Figure 6c, the corners between the cantilever and the lateral edge may include etching residues such that the shortest length LR2 of the resonator plate is some distance from the cantilever, but still close to the cantilever.

[0069] Figure 6d shows an alternative embodiment of a resonator plate with cantilever, wherein the lateral edge of the resonator plate forms a notch between the portion of the resonator plate having the maximum length LR1 and the cantilever 206a, 206b to form a second portion having the minimum length LR2.

[0070] The frame 202 has a frame thickness TF, and the resonator thickness TR is between 25% and 100% of the frame thickness TF, preferably between 25% and 75%, more preferably between 25% and 60%, and even more preferably between 30% and 50%.

[0071] Advantageously, the maximum thickness of the frame TF is less than or equal to 200 µm, more preferably less than or equal to 150 µm, and even more preferably less than or equal to 120 µm.

[0072] The maximum length of the resonator plate 201 is less than or equal to 300 µm, preferably 2000 µm or less, preferably less than or equal to 1000 µm, more preferably less than or equal to 600 µm, and has a width to length ratio of 0.4 to 0.8, preferably 0.5 to 0.7.

[0073] The frame 202 includes a mounting portion 212, which includes a first mounting pad 210 and a second mounting pad 211. The mounting portion 212 extends substantially parallel to the first arm 204 and the second arm 205 of the C-shaped portion 203. The mounting portion 212 is connected to the C-shaped portion 203 and forms a notch 213 with the C-shaped portion 203, as shown in FIG2. Alternatively, the mounting portion is on the C-shaped portion. For example, the first mounting pad may be mounted on the first arm opposite the first cantilever, and the second mounting pad may be mounted on the second arm opposite the second cantilever. In another embodiment, the first mounting pad and the second mounting pad may be mounted on the portion of the frame where the first arm and the second arm engage.

[0074] The maximum length of the frame 202 is less than or equal to 4000µm, preferably less than or equal to 2500µm, more preferably less than or equal to 1500µm, and even more preferably less than or equal to 1500µm.

[0075] The frame 202 is rectangular in shape, and the corners of the frame 202 may be chamfered to minimize potential damage due to sharp corners during resonator manipulation. For the same reason, the resonator plate 201 may also have chamfered corners.

[0076] The resonator plate 201, frame 202 and cantilever 206a, 206b can be obtained by photolithography manufacturing techniques known in the art, such as chemical wet etching or deep ion reactive etching, or a combination thereof or in combination with laser cutting.

[0077] In a second embodiment of the present invention, the method for manufacturing a resonator according to the first embodiment includes the following steps: - providing a ZT-cut quartz wafer and applying a first mask on the wafer surface to cover a first surface of a frame 202 with a C-shaped portion, leaving a portion of the wafer surface uncovered to form a thinner planar portion 199 of the wafer; - chemically wet etching the uncovered surface of the wafer to obtain the thinner planar portion 199; - applying a second mask on the planar portion 199, wherein the second mask has the shape of a resonator plate having cantilever extending from the resonator plate shape to the C-shaped portion of the frame 202; and - chemically wet etching the remaining uncovered surface of the wafer to form the outline of the resonator plate and the cantilever.

[0078] Figure 8a shows a pre-formed resonator obtained by chemical wet etching. The pre-formed resonator includes a frame 202 and a wet-etched planar portion 199 having a substantially constant thickness lower than the thickness of the frame 202. Due to the wet etching of the chemical wet etching, the pre-formed resonator may further include an intermediate portion 216 having a thickness that gradually varies between the frame 202 and the planar portion 199.

[0079] FIG8b illustrates an embodiment of a resonator obtained by the manufacturing method according to the first embodiment, wherein the method includes the step of chemically wet etching the planar portion 199 of the pre-formed resonator described above with respect to FIG8a to form a resonator plate 201 and cantilevers 206a, 206b. To obtain a well-defined shape, a minimum gap 215 width needs to be formed between the resonator plate 201 and the intermediate portion 216. For example, the minimum gap has a width greater than 20µm, preferably at least 50µm, and more preferably at least 75µm. Advantageously, the resulting resonator plate 201 has a smaller area compared to the initial area of ​​the planar portion 199, ensuring a constant thickness of the resonator plate 201 and minimizing its defects.

[0080] In a second embodiment, the method of manufacturing the resonator includes the following steps: - providing a ZT-cut quartz wafer and applying a first mask to the surface of the wafer to cover a first surface of a frame 202 with a C-shaped portion, leaving a portion of the wafer surface uncovered to form a thinner planar portion 199 of the wafer; - cutting the outline of a resonator plate 201 with cantilever arms 206a, 206b extending from the resonator plate to the C-shaped portion of the frame 202 using a femtosecond laser or deep reactive ion etching (DRIE).

[0081] Figure 8c illustrates an embodiment of a resonator obtained by a manufacturing method according to the second embodiment, wherein the method includes cutting the planar portion 199 of the pre-formed resonator of Figure 8a by deep reactive ion etching (DRIE) or by femtosecond laser to form a resonator plate 201 and cantilevers 206a, 206b. To form the resonator plate 201 and cantilevers 206a, 206b, the cutting of the planar portion 199 may be limited to outlining the resonator plate and cantilevers without removing residual planar portions 199b attached to the intermediate portion 216. DRIE or femtosecond laser allows for the cutting of well-defined shapes, and for proper oscillation of the plate, leaving a gap 215 of at least about 1 µm, preferably at least about 5 µm, around the resonator plate 201 and cantilevers 206a, 206b is sufficient. Advantageously, the resulting resonator plate 201 has a smaller area compared to the initial area of ​​the planar portion 199, ensuring a constant thickness of the resonator plate 201 and minimizing its defects.

[0082] In one embodiment of the present invention, the method for manufacturing a resonator according to the third embodiment includes the following steps: - providing a ZT-cut quartz wafer, and; - cutting the outline of a resonator plate 201 with femtosecond laser or deep reactive ion etching (DRIE), the resonator plate 201 having cantilever arms 206a, 206b extending from the resonator plate to a C-shaped portion of a frame 202.

[0083] Figure 9a illustrates a pre-formed resonator according to another embodiment, wherein the pre-formed resonator includes a frame 202 and a planar portion 199a, which may have the same thickness as the frame 202, or wherein the planar portion 199a may be made thinner relative to the thickness of the frame 202 by means of a physical etching method (such as by DRIE or femtosecond laser processing), resulting in the sidewalls of the frame forming substantially right angles with the planar portion 199. With this technique, no etching residue is formed, and the contour cutting of the resonator plate 201 and the cantilever 206a, 206b can be completed by DRIE or femtosecond laser, leaving a small gap between the frame 202 and the resonator plate 201 and the group of cantilever 206a, 206b, except for the ends of the cantilever attached to the frame 202. For proper oscillation of the plate, it is sufficient to leave a gap 215 of at least about 1 µm, preferably at least about 5 µm, around the resonator plate 201 and the cantilever 206a, 206b.

[0084] Any of the above manufacturing methods may include the following steps: forming a notch in the frame to obtain the mounting portion and the C-shaped portion.

[0085] In any of the above manufacturing methods, a plurality of resonators can be fabricated on the same wafer. Advantageously, when a plurality of resonators are located on the same wafer, electrodes can be deposited on the resonator board, and wiring and mounting pads can be deposited on the frame. Then, each resonator on the same wafer can be separated from each other, preferably by femtosecond laser or DRIE.

[0086] Frequency tuning can be achieved by depositing or removing mass, for example by evaporation, sputtering, or laser beam or ion beam etching. Since the mass distribution on the resonator plate affects its thermal characteristics, the frequency-temperature characteristics can be fine-tuned by local ablation or mass deposition. This can be considered as higher-order frequency tuning. Tuning typically acts on the mass of the metal layer on the resonator, but in principle it can be performed directly on the quartz.

[0087] In a non-limiting example according to the invention, the resonator includes a resonator plate 201 and a frame 202. The frame 202 is a rectangle with dimensions of 1400 μm × 580 μm and a thickness of 127 μm. The resonator plate has a thickness of 50 μm, a width of 330 μm, a maximum length LR1 of 570 μm at the edge of the resonator plate, and a second length LR2 of 560 μm at the central longitudinal axis. The frame includes a C-shaped portion 203, which includes a first arm 204 and a second arm 205, and the resonator plate 201 is connected to the frame 202 by a first cantilever 206a and a second cantilever 206b. The cantilever 206a, 206b and the resonator plate 201 have a thickness of 50 μm. The cantilever 206a and 206b each have a width of 50 μm and a length of 90 μm. The resonator board 201 includes a pair of first electrodes 208, 208' connected to a first mounting pad 210, and a second pair of electrodes 209, 209' connected to a second mounting pad 211, as described above with respect to the embodiment of FIG4a.

[0088] Mounting pads are provided on the mounting portion of the frame, which is connected to the C-shaped portion by a rod that is coplanar with the mounting portion and the C-shaped portion, and a notch is formed therebetween.

[0089] Figure 7 shows a simulated image of a resonator according to an embodiment of the present invention, wherein the geometry is optimized to minimize residual coupling with the cantilever and frame. In the simulated image, darker areas represent regions of the resonator plates, where the tensile deformation of the resonator plates 201 on both sides of the node plane 207 is most significant. Brighter areas represent regions of minimal deformation. It can be seen that the amplitude is at its minimum or zero in the regions of the resonator plates 201 near the node plane and the cantilever 206a, 206b. Therefore, when the resonator is in use, i.e., when the resonator plates are supplied with an alternating electric field, the cantilever 206a, 206b and the regions of the resonator plates 201 near the node plane 207 are immovable relative to the frame 202.

[0090] According to the present invention, by providing a resonator plate with a simple shape that is easy to process and has a more stable and fixed shape, the size of ZT-cut quartz resonators can be reduced. [Simplified Explanation of the Diagram]

[0037] The objectives, advantages, and features of the present invention will become apparent upon reading the following description, which is given by way of non-limiting example only, and with reference to the accompanying drawings, in which: - [Figure 1] shows an embodiment of a resonator according to the prior art; - [Figure 2] shows a top view of an embodiment of a resonator according to the present invention; - [Figure 3] shows a side view of an embodiment of a resonator according to the present invention; - [Figures 4a to 4f] show various schematic cross-sectional views of the width of resonator plates with different electrode configurations; - [Figure 5] shows a schematic cross-sectional view of the width of a resonator plate having piezoelectric components; - [Figures 6a to 6d] show schematic top views of resonator plates according to various embodiments of the present invention; - [Figure 7] shows a simulated image of deformation in a resonator when the resonator is subjected to an alternating electric field according to an embodiment of the present invention; - [Figure 8a] shows a top view of an embodiment of a pre-formed resonator, [Figure 8b] shows a top view of an embodiment of a resonator obtained from a manufacturing method according to a first embodiment of the manufacturing method, and [Figure 8c] shows a top view of another embodiment of a resonator obtained from a manufacturing method according to a second embodiment of the manufacturing method; - [Figure 9a] shows a top view of another embodiment of the preformed resonator, and [Figure 9b] shows a top view of a resonator obtained from a manufacturing method according to a third embodiment of the manufacturing method.

[0038] It should be noted that, unless otherwise stated, the drawings are not drawn to scale, and other variations of the resonator design may exist without departing from the spirit of the invention.

Claims

1. A resonator (200), comprising: - A resonator plate (201) having a thickness (TR) and a surface (SR) having a maximum length (LR1) and a width (WR), wherein the resonator plate (201) is ZT-cut quartz; - A frame (202) including a C-shaped portion (203) including a first arm (204) and a second arm (205) extending at least partially around the edge of the width of the resonator plate, wherein each of the first arm (204) and the second arm (205) is connected to the resonator plate by means of cantilever (206a, 206b).

2. The resonator as claimed in claim 1, wherein a node plane (207) is defined, which is orthogonal to the surface (SR) of the resonator plate (201) and passes through the central longitudinal axis of the resonator plate (201), and wherein the cantilever (206a, 206b) passes through the node plane (207).

3. The resonator as claimed in claim 1 or 2, wherein the resonator plate (201) is configured to oscillate on both sides of the node plane (207) in the direction of its width (WR), and the C-shaped portion (203) of the frame (202) is spaced apart from the resonator plate (201) to prevent the resonator plate (201) from contacting the frame (202) when the resonator plate (201) oscillates.

4. The resonator according to claim 1, wherein the resonator plate (201) includes at least a first electrode (208) and a second electrode (209) that are separated from each other and electrically coupled to a first mounting pad (210) and a second mounting pad (211) disposed on the frame (202), the electrode (208) and the electrode (209) being disposed on the resonator plate (201) to generate an electric field between two opposing surfaces of the resonator plate on both sides of the node plane (207).

5. The resonator according to claim 1, wherein a first electrode (208) and a second electrode (209) are disposed on the resonator plate (201) such that when the first electrode and the second electrode are coupled to an AC voltage, an alternating electric field is generated between the two electrodes, thereby deforming the resonator plate along its width direction.

6. The resonator as claimed in claim 1, wherein the cantilever (206a) and cantilever (206b) are integrally formed with the resonator plate (201) and the frame (202), the first cantilever (206a) extending between the resonator plate (201) and the first arm (204) of the C-shaped portion (203); and the second cantilever (206b) extending between the resonator plate (201) and the second arm (205) of the C-shaped portion (203) of the frame (201).

7. The resonator as claimed in claim 1, wherein the resonator plate (201) includes a shortest length (LR2) extending to a location near thereunder: - a first corner formed between a first cantilever and a first lateral edge of the resonator plate; and - a second corner formed between a second cantilever and a second lateral edge of the resonator plate.

8. The resonator as claimed in claim 7, wherein the shortest length (LR2) is at least 90% of the maximum length (LR1), preferably at least 95% of the maximum length (LR1), and more preferably at least 98% of the maximum length (LR1).

9. The resonator as claimed in claim 1, wherein the resonator plate (201) is substantially symmetrical with respect to its intermediate width axis (MW) and with respect to its central longitudinal axis which coincides with the node plane (207).

10. The resonator as claimed in claim 1, wherein the frame (202) has a frame thickness (TF), the resonator has a resonator thickness (TR), the resonator thickness (TR) being between 25% and 100% of the frame thickness (TF), preferably between 25% and 75%, more preferably between 25% and 50%, preferably wherein the maximum thickness (TF) of the frame is less than or equal to 200µm, more preferably less than or equal to 150µm, more preferably less than or equal to 120µm.

11. The resonator as claimed in claim 1, wherein the resonator plate (201) has a maximum length of less than or equal to 2500µm, preferably less than or equal to 1000µm, and more preferably less than or equal to 600µm.

12. The resonator as claimed in claim 1, wherein the resonator plate (201) has a maximum width (WR) such that the ratio of (maximum width (WR)) / (maximum length (LR1)) is between 0.4 and 0.8, preferably between 0.5 and 0.

7.

13. The resonator as claimed in claim 1, wherein the frame (202) includes a mounting portion (212) including the first mounting pad (210) and the second mounting pad (211), the mounting portion (212) extending substantially parallel to the arms (204) and (205) of the C-shaped portion (203), the mounting portion (212) being connected to the C-shaped portion (203) and forming a notch (213) with the C-shaped portion (203).

14. The resonator as claimed in claim 1, wherein the cantilever has: - a length of 10µm to 300µm, preferably 20µm to 150µm, more preferably 40µm to 100µm, and / or; - a width of 25% or less of the width of the resonator plate, and / or; - a thickness between 50% and 150% of the thickness of the resonator plate.

15. A method for manufacturing a ZT-diced resonator, the method comprising the steps of: - providing a ZT-diced wafer; - defining a resonator shape arrangement location on the wafer, wherein the resonator shape arrangement location includes a resonator frame shape arrangement location, a resonator plate shape arrangement location, and a cantilever shape arrangement location, wherein the cantilever shape arrangement location is located on a central longitudinal axis along the resonator plate shape arrangement location, and connecting the lateral sides of the resonator plate shape arrangement location to the resonator frame shape arrangement location; - etching a portion of the wafer to obtain a contour of a resonator plate having cantilevers on its lateral sides, and such that the cantilevers remain integrally formed with the resonator frame; - depositing: ○ at least two separate electrodes on the resonator plate, such that a first electrode has a main portion disposed on one side of a plane passing through the cantilever, and a second electrode has a main portion disposed on the other side of a plane passing through the cantilever; ○ two mounting pads on the resonator frame arrangement location; and ○ connecting rails that connect each electrode to a corresponding mounting pad; and - etching the contour of the resonator frame arrangement location to obtain the resonator.

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