Oven-controlled MEMS oscillator
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- KYOCERA TECH OY
- Filing Date
- 2025-11-13
- Publication Date
- 2026-05-21
Smart Images
Figure FI2025060085_21052026_PF_FP_ABST
Abstract
Description
[0001] OVEN-CONTROLLED OSCILLATOR
[0002] TECHNICAL FIELD
[0003] The present disclosure generally relates to the field of semiconductors. The disclosure relates particularly, though not exclusively, to oven-controlled semiconductor devices.
[0004] BACKGROUND
[0005] This section illustrates useful background information without admission of any technique described herein representative of the state of the art.
[0006] Oven-controlled oscillator devices are used in various timing and sensing applications. The oven-controlled oscillator devices are typically heated to a constant temperature, where the frequency-vs-temperature curve has an inclination point, i.e., a so-called turnover point. The oven-controlled oscillator devices enable controlling the temperature by heating the resonating element.
[0007] Like other resonance-based sensing devices, oven-controlled oscillator devices output resonance frequency signals, indicative of a parameter of interest. However, the resonance frequency is typically sensitive to temperature variation. Thus, the oven-controlled oscillator devices typically comprise a resonating (oscillating) element, a heater and a temperature sensor. Typically, the heater and the temperature sensor are arranged separately from the resonating element itself within the device unit.
[0008] Ageing of materials implies changes of the original state of the materials. These changes can be, for instance, changes in material properties. In case the materials experiencing ageing changes are used in the context of semiconductors, the changes of material properties due to ageing may lead to changes in the semiconductor properties. 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 scheme to solve at least one of the problems related to the prior art, or at least to provide an alternative to existing technology. Accordingly, certain disclosed embodiments provide for an ingenious oven-controlled oscillator device 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 an oven-controlled oscillator device, comprising a resonating element having a top electrode layer, a dielectric layer on top of the top electrode layer, and a trimming layer on top of the dielectric layer.
[0012] In certain embodiments, the top electrode (layer) is implemented by a layer of metal. In certain embodiments, the top electrode comprises (is of) metal. In certain embodiments, the top electrode is of gold, doped gold, or gold alloy. In certain embodiments, the top electrode (layer) is implemented by a layer of doped silicon, such as doped polysilicon or doped single-crystal silicon.
[0013] In certain embodiments, the top electrode layer is of high conductivity material. In certain embodiments, the high conductivity material is a high electrical conductivity material. In certain embodiments, the top electrode layer is of high (electrical) conductivity material having conductivity in the range of 104to 108S / m (Siemens per meter). In certain embodiments, the top electrode layer is of (highly) doped polysilicon having conductivity at least 10000 S / m. In certain embodiments, the top electrode layer is of UHD doped polysilicon having conductivity in the range of 10000 S / m to 200 000 S / m. In certain embodiments, the top electrode layer is of metal having conductivity less than 100 MS / m (wherein M is mega, 106). In certain embodiments, the top electrode layer is of metal having conductivity in the range of 5 to 70 MS / m.
[0014] In certain embodiments, the top electrode layer is of high conductivity material, such as gold, molybdenum, or highly doped polysilicon. In certain embodiments, the top electrode layer is of gold, molybdenum, or highly doped polysilicon. In certain embodiments, the dielectric layer is of insulating material. In certain embodiments, the dielectric layer is of insulating material, such as silicon dioxide. In certain embodiments, the dielectric layer is of silicon dioxide. In certain embodiments, the dielectric layer is of aluminum nitride, AIN.
[0015] In certain embodiments, the trimming layer is of a high-density material. In certain embodiments, the trimming layer is of a high-density material having density at least 10 g / cm3. In certain embodiments, the trimming layer is of a material having linear temperature coefficient of resistance, TCR. In certain embodiments, the trimming layer is of a high-density material, such as gold or platinum. In certain embodiments, the trimming layer is of gold or platinum.
[0016] In certain embodiments, the trimming layer covers (the surface of) the resonating element partially. In certain embodiments, the trimming layer is patterned to cover the resonating element partially. In certain embodiments, the trimming layer is patterned to cover the resonating element only partially.
[0017] In certain embodiments, the trimming layer runs (goes, reaches) through the resonating element. In certain embodiments, the trimming layer runs continuously through the resonating element. In certain embodiments, the trimming layer runs through the resonating element in the length direction of the resonating element. In certain embodiments, the trimming layer runs through the resonating element from one side to another side of the resonating element.
[0018] In certain embodiments, the trimming layer is patterned to run through (extend, reach, travel, go) the resonating element. In certain embodiments, the trimming layer is patterned to run through the resonating element from one anchoring point to another anchoring point of the resonating element. In certain embodiments, the trimming layer is patterned to run through the resonating element from one side to another side of the resonating element (in width and / or in length direction). In certain embodiments, the trimming layer is patterned to run through the resonating element from one edge to another edge of the resonating element (in width and / or in length direction).
[0019] In certain embodiments, the trimming layer meanders across the resonating element. In certain embodiments, the trimming layer is patterned to meander across the resonating element. In certain embodiments, the trimming layer is patterned to meander across the resonating element from one anchoring point to another anchoring point of the resonating element. In certain embodiments, the trimming layer is patterned to meander across the resonating element from one side to another side of the resonating element (in width and / or in length direction).
[0020] In certain embodiments, the trimming layer is patterned such that the trimming layer forms meanders (turns, bends, twists) through (along) the resonating element. In certain embodiments, the trimming layer is patterned such that the trimming layer forms at least three meanders along the resonating element. In certain embodiments, the trimming layer is patterned selectively to maximise (or at least to increase) resistance of the trimming layer. In certain embodiments, the trimming layer is a patterned trimming layer. In certain embodiments, the trimming layer is a meandering trimming layer. In certain embodiments, the trimming layer is a meandering trimming layer having at least three meanders. In certain embodiments, the meandering trimming layer forms a narrow pathway for the charge carriers (across / through / along the resonating element). In certain embodiments, the meanders of the meandering trimming layer cover (essentially) the resonating element (cover the entire resonating element surface). In certain embodiments, the meanders of the meandering trimming layer are arranged on the resonating element symmetrically (wherein the symmetry axis runs in either x or y direction).
[0021] In certain embodiments, the trimming layer is patterned by lithographic patterning and etching. In certain embodiments, the trimming layer is configured to enable trimming (modulating, adjusting) of the resonance frequency of the resonating element. In certain embodiments, the trimming layer is configured to enable trimming of the resonance frequency of the resonating element by physically etching away a given thickness of the trimming layer.
[0022] In certain embodiments, the oven-controlled oscillator device comprises a temperature sensor and / or a heater on the device itself. In certain embodiments, the oven-controlled oscillator device comprises a temperature sensor and a heater on the device itself. In certain embodiments, the oven-controlled oscillator device comprises a temperature sensor and a heater on the resonating element itself. In certain embodiments, the oven-controlled oscillator device does not comprise a separate temperature sensor and a separate heater. In certain embodiments, the trimming layer is configured to provide a temperature sensor and a heater for the oven-controlled oscillator. In certain embodiments, the trimming layer is configured to provide a temperature sensor and / or a heater for the oven-controlled oscillator. In certain embodiments, the oven-controlled oscillator device is a dual-function device (or a triple-function device). In certain embodiments, the oven-controlled oscillator device is configured to measure (provide) both a parameter of interest and temperature simultaneously (or alternately). In certain embodiments, the oven-controlled oscillator device provides (is configured to provide) as an output resonance frequency (signals) that are indicative of a parameter of interest. In certain embodiments, the oven-controlled oscillator device is configured to provide both a parameter of interest and temperature in one unit (one device, one apparatus, no need for separate sensors for each measured parameter). In certain embodiments, the resistance of (measured from) the trimming layer is (configured to provide) the temperature reading.
[0023] In certain embodiments, the oven-controlled oscillator device is a heated device. In certain embodiments, the trimming layer is a heater for the oven-controlled oscillator device. In certain embodiments, the trimming layer is configured to act as a heater for the oven-controlled oscillator device. In certain embodiments, electric current flowing through the trimming layer is configured to heat the oven-controlled oscillator device.
[0024] In certain embodiments, the oven-controlled oscillator device comprises contact points (in the context of a wafer level packaged device). In certain embodiments, the oven-controlled oscillator device comprises contact points, coupled to through silicon vias connected to external pads. In certain embodiments, the oven-controlled oscillator device comprises contact points, formed by through silicon vias connected via cap contact pads to external (contact) pads. In certain embodiments, the contact points are configured to provide electric (electrical) contact to outside of the oven-controlled oscillator device. In certain embodiments, the contact points are configured to provide mechanical contact to the outside of the oven-controlled oscillator device.
[0025] In certain embodiments, the oven-controlled oscillator device comprises a plurality of contact points. In certain embodiments, the oven-controlled oscillator device comprises a plurality of external contact pads. In certain embodiments, the oven-controlled oscillator device comprises a plurality of contact pads.
[0026] In certain embodiments, the oven-controlled oscillator device comprises at least four contact points. In certain embodiments, the oven-controlled oscillator device comprises at least four external contact pads. In certain embodiments, the oven-controlled oscillator device comprises at least four contact pads. In certain embodiments, the oven-controlled oscillator device comprises four contact points. In certain embodiments, the oven-controlled oscillator device comprises four external contact pads. In certain embodiments, the oven-controlled oscillator device comprises four cap contact pads.
[0027] In certain embodiments, at least two of the contact points are for sensing (determining, measuring, detecting) a parameter of interest, and at least two of the contact points are for temperature sensing. In certain embodiments, the at least two of the contact points used for sensing a parameter of interest are different contact points from the at least two of the contact points used for temperature sensing.
[0028] In certain embodiments, two of the (four) contact points are for sensing (determining, measuring, detecting) a parameter of interest, and two of the (four) contact points are for temperature sensing. In certain embodiments, three of the contact points are for sensing (determining, measuring, detecting) a parameter of interest, and three of the contact points are for temperature sensing. In certain embodiments, the two of the (four) contact points used for sensing a parameter of interest are different contact points from the two of the (four) contact points used for temperature sensing.
[0029] In certain embodiments, the oven-controlled oscillator device provides (is configured to provide) as an output resonance frequency signal(s) that are indicative of a parameter of interest. In certain embodiments, the oven-controlled oscillator device provides as an output resonance frequency signal(s) and an amplitude of the resonance frequency that are indicative of a parameter of interest.
[0030] In certain embodiments, the resonance frequency (and the amplitude) of the device is measured. In certain embodiments, the resonance frequency (and the amplitude) of the device is measured, which enables determining the parameter of interest. In certain embodiments, the sensing of the parameter of interest is provided by (is enabled by) sensing the resonance frequency of the device. In certain embodiments, the parameter of interest is (provided, enabled) based on tracking (measuring, sensing, determining) the resonance frequency. In certain embodiments, the parameter of interest is (provided, enabled) based on tracking resonance frequency and the amplitude of the resonance frequency.
[0031] In certain embodiments, the parameter (measurement, value, unit) of interest is (high precision) timing. In certain embodiments, the parameter (measurement, value, unit) of interest is mass. In certain embodiments, the parameter (measurement, value, unit) of interest is gas. In certain embodiments, the parameter (measurement, value, unit) of interest is acceleration, or deceleration.
[0032] In certain embodiments, the trimming layer is coupled to two of the (four) contact points. In certain embodiments, the trimming layer is coupled to the two of the (four) contact points used for temperature sensing. In certain embodiments, the trimming layer is a tri-functional trimming layer. In certain embodiments, the trimming layer is a tri-functional trimming layer used for trimming, temperature sensing and heating of the resonating element. In certain embodiments, the resonating element is coupled to the two of the (four) contact points used for sensing a parameter of interest. In certain embodiments, the sensing of parameter of interest is provided by sensing (tracking, measuring) of frequency (and amplitude) of the resonance (vibration). In certain embodiments, the sensing of parameter of interest is provided by sensing of the change in frequency (and the amplitude) of the resonance. In certain embodiments, the electric contact (current, flow, charge carriers) are provided to the oven-controlled oscillator via a route, the route formed by through silicon vias (through the cap wafer) connected to pads. In certain embodiments, the electric contact (current, flow, charge carriers) are provided to the oven-controlled oscillator via a route, the route formed by contact points connected to cap contact pads, the cap contact pads coupled with through silicon vias connected to external pads.
[0033] In certain embodiments, the oven-controlled oscillator device is fabricated on a substrate. In certain embodiments, the substrate is a silicon-on-insulator, SOI, wafer. In certain embodiments, the substrate is a cavity silicon-on-insulator, CSOI, wafer. In certain embodiments, the substrate is a silicon-on-insulator, SOI, substrate, or a cavity silicon-on-insulator, CSOI, substrate.
[0034] In certain embodiments, the substrate comprises a buried oxide layer, BOX. In certain embodiments, the buried oxide layer is between a handle wafer portion and a device wafer portion. In certain embodiments, the handle wafer portion and the device wafer portion comprise silicon. In certain embodiments, the substrate comprises a cavity. In certain embodiments, the substrate comprises a cavity underneath the resonating element.
[0035] In certain embodiments, the device wafer portion comprises silicon (a silicon layer). In certain embodiments, the device wafer portion 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 doping level of the silicon is above 1019 cm3. In certain embodiments, the doping level of the silicon is above 1O20cm3. In certain embodiments, the doped silicon is of N-type or P-type doping.
[0036] In certain embodiments, the device wafer portion comprises a piezoelectric layer. In certain embodiments, the device wafer portion comprises a piezoelectric layer on the silicon layer (silicon body) of the device wafer portion. In certain embodiments, the piezoelectric layer (material) is of aluminum nitride, AIN.
[0037] In certain embodiments, the device wafer portion comprises a silicon layer, and a piezoelectric layer on top of the silicon layer. In certain embodiments, the top electrode, the dielectric layer and the trimming layer are arranged onto the device wafer portion (onto the piezoelectric layer of the device wafer portion). In certain embodiments, (the resonating element of) the oven-controlled oscillator device comprises a silicon layer, a piezoelectric layer on top of the silicon layer, a top electrode layer on top of the piezoelectric layer, a dielectric layer on top of the top electrode layer, and a trimming layer on top of the dielectric layer.
[0038] In certain embodiments, (the resonating element of) the oven-controlled oscillator device comprises a material stack, the material stack comprising the silicon layer (the bottom electrode), the piezoelectric layer on top of the silicon layer, a top electrode layer on top of the piezoelectric layer, a dielectric layer on top of the top electrode layer, and a trimming layer on top of the dielectric layer. In certain embodiments, the oven-controlled oscillator device comprises a piezoelectric device.
[0039] In certain embodiments, the oven-controlled oscillator device comprises a bottom electrode. In certain embodiments, the oven-controlled oscillator device comprises a bottom electrode layer. In certain embodiments, the oven-controlled oscillator device comprises a bottom electrode layer of silicon. In certain embodiments, the oven-controlled oscillator device comprises a resonating element having two electrode layers. In certain embodiments, the oven-controlled oscillator device comprises a resonating element having a top electrode layer and a bottom electrode layer. In certain embodiments, the silicon layer is configured to implement a bottom electrode of device. In certain embodiments, the silicon layer is a bottom electrode of the oven-controlled oscillator device. 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 (of the device wafer portion). In certain embodiments, the doping level of the silicon is above 1019cm3. In certain embodiments, the doping level of the silicon is above 1O20cm3. In certain embodiments, the doped silicon is of N-type or P-type doping.
[0040] In certain embodiments, the oven-controlled oscillator is an oven-controlled microelectromechanical systems, MEMS, oscillator, OCMO. In certain embodiments, the oven-controlled oscillator is an oven-controlled quartz crystal oscillator, OCXO.
[0041] In certain embodiments, the sealing ring encircles (is configured to encircle) the oven-controlled oscillator device.
[0042] In certain embodiments, the oven-controlled oscillator device comprises a resonating (oscillating) element. In certain embodiments, the device comprises a microelectromechanical systems, MEMS, resonator. In certain embodiments, the oven-controlled oscillator device is configured to operate in a megahertz frequency area. In certain embodiments, the oven-controlled oscillator device is configured to operate at 32 MHz frequency.
[0043] In certain embodiments, the oven-controlled oscillator device comprises at least one resonating element (resonator). In certain embodiments, the oven-controlled oscillator device comprises a plurality of resonating elements. In certain embodiments, the resonating element comprises a plurality of resonating beam elements. In certain embodiments, each beam element is a sub-element of the device.
[0044] In certain embodiments, the resonating element 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.
[0045] In certain embodiments, the device comprises 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 device. In certain embodiments, the beam elements are separated by trenches. In certain embodiments, the beam elements are connected to each other by connection elements.
[0046] In certain embodiments, the device comprises a plurality of stacked beam resonators. In certain embodiments, the stacked beam resonators are positioned side-by-side in a plane. In certain embodiments, the plurality of stacked beam resonators are positions adjacent to each other and connected to one another by a coupler. In certain embodiments, the coupler is an in-plane (mode) coupler. In certain embodiments, the coupler is a flexural (mode) coupler. In certain embodiments, the coupler is a length-extensional (mode) coupler. In certain embodiments, the coupler is a rigid coupler. In certain embodiments, the stacked beam resonators are separated by trenches.
[0047] In certain embodiments, the resonating element of the device 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 device are arranged in a rectangular array configuration.
[0048] In certain embodiments, the resonating element is in a shape of a rectangle. In certain embodiments, the resonating element is in a shape of an elongated rectangle (beamshaped). In certain embodiments, the resonating element has an aspect ratio (ratio of length to width, when observed from above) different from 1. In certain embodiments, each beam element is in a 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.
[0049] In certain embodiments, the resonating element has a length-to-width aspect ratio of less than 1. In certain embodiments, the resonating element is attached (supported, anchored, suspended) to a support structure. In certain embodiments, the resonating element is attached to a support structure from the outermost beam elements of the resonating element. In certain embodiments, the resonating element comprises at least one anchoring point configured to connect the resonating element to, and suspend the device to the support structure (from surrounding layers). In certain embodiments, the resonating element comprises two anchoring points configured to connect the device to, and suspend the device to the support structure (from surrounding layers). In certain embodiments the anchoring point(s) comprise portions of the silicon layer (bottom electrode), the piezoelectric layer, the top electrode, the dielectric layer and the trimming layer.
[0050] 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).
[0051] In certain embodiments, the oven-controlled oscillator device is configured to resonate (operate, oscillate, vibrate) in an in-plane resonance mode. In certain embodiments, the oven-controlled oscillator device is configured to operate (resonate) in an in-plane lengthextensional, LE, resonance mode. In certain embodiments, the length extensional resonance mode is configured to resonate parallel to the length direction of the resonating element of the oven-controlled oscillator device. In certain embodiments, the length extensional resonance mode is configured to resonate perpendicular to the width direction of the resonating element of the oven-controlled oscillator device.
[0052] In certain embodiments, the oven-controlled oscillator device is configured to resonate in a square-extensional, SE, resonance mode. In certain embodiments, the oven-controlled oscillator device is configured to resonate in a width-extensional, WE, resonance mode. In certain embodiments, the oven-controlled oscillator device is configured to resonate in a out-of-plane resonance mode. In certain embodiments, the oven-controlled oscillator device is configured to resonate in an out-of-plane flexural resonance mode.
[0053] In certain embodiments, the oven-controlled oscillator device is configured to resonate in a collective resonance mode. In certain embodiments, each resonating beam element of the oven-controlled oscillator device is configured to resonate in the (same) collective resonance mode. In certain embodiments, the oven-controlled oscillator device is configured to resonate in a desired (main) resonance mode. In certain embodiments, each resonating beam element is configured to resonate in the (same) desired resonance mode. According to a second example aspect of the present disclosure there is provided a packaged semiconductor apparatus, comprising at least one oven-controlled oscillator device of the first aspect or any of its embodiments.
[0054] In certain embodiments, the packaged semiconductor apparatus comprises at least one oven-controlled oscillator device. In certain embodiments, the packaged semiconductor apparatus comprises a plurality of oven-controlled oscillator devices (such as two devices). In certain embodiments, the packaged semiconductor apparatus comprises a cap wafer and the device wafer bonded together. In certain embodiments, the packaged semiconductor apparatus comprises a cap wafer and the device wafer bonded together via thermocompression bonding. In certain embodiments, the packaged semiconductor apparatus is a wafer-level packaged, WLP, apparatus. In certain embodiments, the packaged semiconductor apparatus comprises an enclosure (formed by the cap wafer and the device wafer bonded together).
[0055] In certain embodiments, the device wafer comprises the handle wafer portion and the device wafer portion (optionally separated from one another by a buried oxide layer, and / or a cavity (the cavity being at least underneath the resonating element)).
[0056] In certain embodiments, the cap wafer of the packaged semiconductor apparatus comprises a (at least one) recess. In certain embodiments, the recess is arranged on the cap wafer facing the enclosure (inside the enclosure, facing the resonating element). In certain embodiments, the recess is arranged at the vertical location of the resonating element (above the resonating element, when observed from above).
[0057] In certain embodiments, the cap wafer of the packaged semiconductor apparatus comprises a redistribution layer. In certain embodiments, the redistribution layer is arranged on the cap wafer facing the enclosure (inside the enclosure, facing the resonating element). In certain embodiments, the redistribution layer is of gold.
[0058] In certain embodiments, the cap wafer comprises a sealing ring. In certain embodiments, the packaged semiconductor apparatus is sealed by a sealing ring. In certain embodiments, the cap wafer and the device wafer are sealed together by a sealing ring. In certain embodiments, the sealing ring is formed of two counterparts, one being on the device wafer and one being on the cap wafer. In certain embodiments, the two counterparts of the sealing ring are configured to merge with each other upon bonding. In certain embodiments, the sealing ring is configured to provide a hermetical seal for the packaged semiconductor apparatus.
[0059] In certain embodiments, the sealing ring (of the device wafer) encircles the oven-controlled oscillator device. In certain embodiments, the sealing ring is formed of the redistribution layer.
[0060] In certain embodiments, the cap wafer comprises cap contact pads (cap pads). In certain embodiments, the cap wafer comprises four cap contacts pads. In certain embodiments, the cap contact pads are coupled to the contact points of the oven-controlled oscillator device (upon bonding). In certain embodiments, the cap contacts pads are configured to provide electric (and mechanical) contact to the oven-controlled oscillator device. In certain embodiments, the through silicon vias are configured to through the cap wafer.
[0061] In certain embodiments, the cap wafer comprises external pads (external contact pads). In certain embodiments, the cap wafer comprises four external pads. In certain embodiments, the external pads are coupled by through silicon vias (and the cap contact pads) to the contact points of the oven-controlled oscillator device, respectively. In certain embodiments, the external pads are configured to provide electric (and mechanical) contact from outside into the oven-controlled oscillator device.
[0062] According to a further example aspect of the present disclosure there is provided a use of the oven-controlled oscillator device of the first aspect of any of its embodiments or the packaged semiconductor apparatus of the second aspect or any of its embodiments in a sensing application.
[0063] 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.
[0064] 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.
[0065] BRIEF DESCRIPTION OF THE FIGURES
[0066] Some example embodiments will be described with reference to the accompanying figures, in which:
[0067] Fig. 1 schematically shows an oven-controlled oscillator device in a side view according to an example embodiment;
[0068] Fig. 2a schematically shows an oven-controlled oscillator device having a stacked beam resonating element in a top view according to an example embodiment; Fig. 2b schematically shows an oven-controlled oscillator device having a resonating plate element in a top view according to an example embodiment;
[0069] Fig. 3 schematically shows a cap wafer of the packaged oven-controlled oscillator device on side facing the resonating element in a top view according to an example embodiment;
[0070] Fig. 4 schematically shows a cap wafer of the packaged oven-controlled oscillator device on side facing outside in a top view according to an example embodiment;
[0071] Fig. 5 schematically shows an oven-controlled oscillator device in a top view with temperature sensing and heating decoupled according to an example embodiment;
[0072] Fig. 6 schematically shows a cap wafer of the packaged oven-controlled oscillator device with temperature sensing and heating decoupled on side facing the resonating element in a top view according to an example embodiment; and Fig. 7 schematically shows a cap wafer of the packaged oven-controlled oscillator device with temperature sensing and heating decoupled on side facing outside in a top view according to an example embodiment.
[0073] DETAILED DESCRIPTION
[0074] In the following description, like reference signs denote like elements or steps.
[0075] As used herein, the term a semiconductor apparatus refers to any kind of apparatus or device that may appear in a semiconductor industry, such as a chip, circuitry, microchip, microprocessor, filter, silicon chip, computer chip, resonator, sensor, accelerometer, gyroscope, actuator and process-control unit, vacuum tube or alike. In certain embodiments, the semiconductor apparatus has been packaged. In certain embodiments, the semiconductor apparatus comprises a MEMS device.
[0076] As used herein, the term resonating element is used to refer to a (silicon-based) element suspended to a supporting structure so as to be capable of resonating in a resonance mode. In certain embodiments, the resonating element comprises a piezoelectric actuation.
[0077] As used herein, the term packaged apparatus or chip means a single package, i.e. one physical entity that comprises a device (oscillator, resonator, a resonating element) having structure(s), such as resonating beam(s). According to certain embodiments, the packaged apparatus is a packaged semiconductor apparatus. According to certain embodiments, the packaged apparatus comprises a device wafer and a cap wafer bonded together to form the package. As used herein, the term die means the part that is diced from a ready fabricated silicon wafer in the dicing operation. In dicing, the dies are separated from each other using a special equipment. In the context of the instant disclosure, the term die forms a synonym to the term chip. Other synonyms to the terms chip and die is the term component.
[0078] The axes x, y and z are denoted to each Figure to illustrate the direction of observing. The axes are interrelated, meaning that each of the notations x, y or z are to be understood as the same x, y or z direction in all the Figures.
[0079] Fig. 1 schematically shows an oven-controlled oscillator device 100 in a side view according to an example embodiment. The oven-controlled oscillator device 100 comprises a resonating element 110 having a top electrode (layer) 103, a dielectric layer 102 on top of (on, on the surface of, deposited onto) the top electrode layer 103, and a trimming layer 101 on top of the dielectric layer 102. In other words, the oven-controlled oscillator device 100 comprises a resonating element 110 comprising a trimming layer 101, a dielectric layer 102 beneath the trimming layer 101, and a top electrode layer 103 beneath the dielectric layer 102.
[0080] In certain embodiments, the top electrode layer 103 is of high conductivity material having conductivity the range of 104to 108S / m. In certain embodiments, the top electrode layer 103 is of gold, molybdenum, or highly doped polysilicon. In certain embodiments, the highly doped polysilicon has a doping concentration of at least 102° cm-3. In certain embodiments, the top electrode layer 103 has a thickness of less than 200nm, preferably less than 100nm.
[0081] In certain embodiments, the dielectric layer 102 is of insulating material, such as silicon dioxide. In certain embodiments, the dielectric layer 102 is configured to passivate the top electrode layer 103.
[0082] In certain embodiments, the trimming layer 101 is of a high-density material having density of at least 10 g / cm3. In certain embodiments, the trimming layer 101 is of material having linear temperature coefficient of resistance, TCR. In certain embodiments, the trimming layer 101 is of gold or platinum. In certain embodiments, the trimming layer 101 is configured to enable trimming (modulating, adjusting) of the resonance frequency of the resonating element 110.
[0083] In certain embodiments, the oven-controlled oscillator device 100 is fabricated on a substrate. In the embodiment shown in Fig. 1, the substrate is a cavity silicon-on-insulator, CSOI, silicon wafer. In the embodiment shown in Fig. 1, the substrate comprises a cavity 108 underneath the resonating element 110. In certain embodiments, the resonating element 110 is configured to resonate (vibrate, oscillate) within the cavity 108.
[0084] In the embodiment shown in Fig. 1, the substrate comprises a buried oxide layer, BOX, 106 in between a handle wafer portion 107 and a device wafer portion 101, 102, 103, 104, 105. In certain embodiments, the device wafer portion comprises a silicon layer 105. In certain embodiments, the device 100 comprises a bottom electrode layer. In certain embodiments, the silicon layer 105 is configured to implement a bottom electrode of the oven-controlled oscillator device 100. In certain embodiments, the silicon layer 105 is preferably doped silicon, such as ultra-heavily doped, UHD, silicon. In certain embodiments, the bottom electrode (layer) is implemented by an UHD silicon layer (of the device wafer portion). In certain preferred embodiments, the silicon layer 105 is of single-crystal silicon. In certain embodiments, the doping level of the silicon layer 105 is above 1019cm-3, such as above 102° cm-3. In certain embodiments, the doped silicon is of N-type or P-type doping. The UHD doping of the silicon layer enables bringing the turnover temperature of the oven-controlled oscillator device over the desired temperature operating range.
[0085] In certain embodiments, the device wafer portion comprises a piezoelectric layer 104 on the silicon layer 105. In certain embodiments, the piezoelectric layer 104 is arranged in between the silicon layer 105 and the top electrode layer 103. In certain embodiments, the piezoelectric layer 104 is of aluminum nitride, AIN.
[0086] In certain embodiments, the said top electrode layer 103, dielectric layer 102 and trimming layer 101 are arranged onto the piezoelectric layer 104. In certain embodiments, the resonating element 110 comprises a material stack comprising a silicon layer 105, a piezoelectric layer 104 on top of the silicon layer 105, a top electrode layer 103 on top of the piezoelectric layer 104, a dielectric layer 102 on top of the top electrode layer 103, and a trimming layer 101 on top of the dielectric layer 102. In other words, the resonating element 110 comprises a material stack comprising a trimming layer 101, a dielectric layer 102 beneath the trimming layer 101, a top electrode layer 103 beneath the dielectric layer 102, a piezoelectric layer 104 beneath the top electrode layer 103, and a silicon layer 105 beneath the piezoelectric layer 104.
[0087] As shown in Fig. 1, in certain embodiments, the resonating element 110 is separated from the support structure by trenches 109.
[0088] In certain embodiments, the oven-controlled oscillator device 100 comprises contact points XIN, XOUT, TIN, TOUT. In certain embodiments, the contact points XOUT is arranged ata location having a top electrode layer 103 and a trimming layer 101 on top of the top electrode layer 103 (the dielectric layer is omitted). Thereby XOUT allows electric current (charge carriers) to exit from the oven-controlled oscillator device. In certain embodiments, the contact point XOUT is coupled (connected) to the silicon layer 105 by a contact hole 111. As shown in Fig.
[0089] 1 , in certain embodiments, the contact hole 111 is filled with both top electrode material and trimming layer material. In certain alternative embodiments, the contact hole 111 is filled with trimming layer material (not shown). The conductive material layer(s) allow the electric current (charge carriers) to move from the silicon layer 105 to the contact point XOUT.
[0090] In certain embodiments, the contact points XIN is arranged at a location having a top electrode layer 103 and a trimming layer 101 on top of the top electrode layer 103 (the dielectric layer is omitted). Thereby XIN allows electric current (charge carriers) to travel (enter) into the (layer(s) of) oven-controlled oscillator device.
[0091] In certain embodiments, the contact points TIN and TOUT are each arranged at a location having a top electrode layer 103, a dielectric layer 1023 on top of the top electrode layer 103, and a trimming layer 101 on top of the dielectric layer 103. Thereby TIN and TOUT allow electric current (charge carriers) to travel (enter and exit) only within the trimming layer 101. The dielectric layer 102 prevents the electric current from entering the layer(s) beneath. Accordingly, in these embodiments, the top electrode layer 103 does not connect to trimming layer 101.
[0092] Fig. 2a schematically shows an oven-controlled oscillator device 100 in a top view according to an example embodiment.
[0093] In certain embodiments, the trimming layer 101 covers the surface of the resonating element 110 partially. In certain embodiments, the trimming layer 101 is a patterned trimming layer 101. In certain embodiments, the trimming layer 101 is patterned by lithographic patterning and etching. In certain embodiments, the dielectric layer 102 is exposed on the areas in which the trimming layer 101 has been removed via patterning.
[0094] In certain embodiments, the trimming layer 101 runs (goes, reaches) through the resonating element 110 with a (meandering) path. In certain embodiments, the trimming layer 101 runs continuously through the resonating element 110, from one side of the resonating element 110 to another side of the resonating element 110. As shown in Fig. 2a, in certain embodiments, the trimming layer 101 is patterned to run through the resonating element 110 from one anchoring point 202 to another anchoring point 202 of the resonating element 110. As shown in Fig. 2a, in certain embodiments, the trimming layer 101 meanders across the resonating element 110. As shown in Fig. 2a, in certain embodiments, the trimming layer 101 forms a (narrow) path having meanders 204 along the resonating element 110. In certain embodiments, the trimming layer 101 is patterned selectively to maximise resistance of the trimming layer 110.
[0095] As mentioned, in certain embodiments, the trimming layer 101 forms a narrow pathway for the charge carriers across the resonating element 110. In certain embodiments, the charge carriers (electric current) is configured to enter the trimming layer 101 (pathway) via contact point TIN and exit the trimming layer via contact point TOUT. Thus, the oven-controlled oscillator device comprises two ‘extra’ contact points TIN and TOUT (in addition to the contact points XIN, XOUT)
[0096] In certain embodiments, the trimming layer 101 is configured to provide (both) a temperature sensor and a heater for the oven-controlled oscillator device 100. As the electric current travels across the resonating element 110 via the patterned trimming layer 101, there is resistance. The resistance of the trimming layer 101 between TIN and TOUT is used to read (sense, detect, determine) the device temperature. In certain embodiments, the reading of the resistance of trimming layer 101 enables providing in situ temperature sensing. The resistance of the trimming layer 101 changes linearly with temperature in accordance with certain embodiments. The trimming layer 101 is of a material having linear TCR in accordance with certain embodiments. This enables reliable temperature sensing using the trimming layer 101 resistance.
[0097] In certain embodiments, the oven-controlled oscillator device 100 is heated. In certain embodiments, the oven-controlled oscillator device 100 is heated by the electric current (charge carriers) flowing through trimming layer 101. In certain embodiments, the current applied to TIN is modulated to heat the device 100. In certain embodiments, the current applied to TIN is modulated to tune (trim, adjust) the resonance frequency of the device 100.
[0098] Accordingly, in certain embodiments, the oven-controlled oscillator device 100 comprises a temperature sensor and a heater on the device itself, implemented by the trimming layer 101. Accordingly, the need for a separate temperature sensor and a separate heater is omitted. Further accordingly, in certain embodiments, the trimming layer 101 is a triplefunction trimming layer 101, as it is used for frequency trimming, temperature sensing and heating for the oven-controlled oscillator circuit.
[0099] In certain embodiments, the oven-controlled oscillator device 100 is configured to measure (sense, detect, determine) both a parameter of interest and temperature in one device. There is no need for separate sensors for each measured parameter. In certain embodiments, the oven-controlled oscillator device 100 is configured to measure both a parameter of interest and temperature simultaneously, or by alternating (predetermined) sequences.
[0100] As used herein, the parameter of interest is used to refer to a parameter for which the oven-controlled oscillator device 100 is designed (configured) to provide. The oven-controlled oscillator device provides as an output resonance frequency signal(s) that are indicative of a parameter of interest. In certain embodiments, the parameter of interest is a parameter different from temperature. In certain embodiments, the parameter of interest is (high precision) timing, sensing of mass sensing of gas, sensing of acceleration, or deceleration.
[0101] As shown in Fig. 2a, in certain embodiments, the oven-controlled oscillator device 100 comprises contact points XIN, XOUT, TIN, TOUT. In certain embodiments, the contact points XIN, XOUT, TIN, TOUT are coupled to through silicon vias, the through silicon vias being connected pads (through silicon vias and pads shown in Figs. 3 and 4). In certain embodiments, the contact points XIN, XOUT, TIN, TOUT are configured to provide electric and mechanical contact from / to the oven-controlled oscillator device 100. In certain embodiments, two of the four contact points XIN, XOUT are for sensing a parameter of interest, and two of the four contact points TIN, TOUT are for temperature sensing. In certain embodiments, the two of the four contact points XIN, XOUT are used for sensing the frequency (and amplitude) of the resonance. In certain embodiments, the trimming layer 101 is coupled to the contact points TIN and TOUT via a TIN trace 203 and TOUT trace 203, respectively. In certain embodiments, the TIN trace 203 and the TOUT trace 203 are of the same material as the trimming layer 101. In certain embodiments, the oven-controlled oscillator device 100 is coupled to a contact point XIN via a XIN trace 205. In certain embodiments, the XIN trace 205 is of same material as the top electrode layer 103.
[0102] In certain embodiments, the oven-controlled oscillator device 100 is an oven-controlled microelectromechanical systems, MEMS, oscillator, OCMO. In certain embodiments, the turnover temperature of the OCMO is higher than the operating temperature of the OCMO.
[0103] In certain embodiments, the sealing ring 201 encircles the oven-controlled oscillator device 100. In certain embodiments, the sealing ring 201 is of gold.
[0104] As shown in Fig. 2a, in certain embodiments, the resonating element 110 comprises a plurality of resonating beam elements 206. In certain embodiments, the resonating element 110 comprises a plurality of beam elements 206 positioned adjacent to each other, mechanically connected to each other by connection elements and separated by trenches 207. In certain embodiments, the device 100 comprises a stacked beam resonator (ladderlike configuration), comprising a plurality of beam elements 206 positioned side-by-side in a plane. In certain embodiments, the resonating element 110 is attached to a support structure from the outermost beam elements of the resonating element via at least one anchoring point 202. The embodiment shown in Fig. 2a comprises two anchoring points 202. In certain embodiments, the device comprises electric terminals at the anchoring point(s) 202. In certain embodiments, the anchoring points 202 are configured to connect the device 100 to, and suspend the device 100 to the support structure. In certain embodiments, the resonating element 110 is separated from the support structure by an external trench 207’.
[0105] In certain embodiments, the oven-controlled oscillator device 100 is configured to resonate in an in-plane length-extensional, LE, resonance mode, configured to resonate parallel to the length direction (shown in Fig. 2a as x-direction) of the resonating element 110 of the oven-controlled oscillator device 100. In certain embodiments, each resonating beam element 206 of the resonating element 110 of the oven-controlled oscillator device 100 is configured to resonate in the (same) collective resonance mode. Fig. 2b schematically shows an oven-controlled oscillator device having a resonating plate element in a top view according to an example embodiment. Fig. 2b shows otherwise an analogous device in comparison to Fig. 2a, except for the type of the resonating element 110.
[0106] In certain embodiments, the resonating element 110 comprises one resonating element. In certain embodiments, the resonating element 110 comprises a resonating plate element 206’. In certain embodiments, the resonating plate element 206’ is separated from the support structure by an external trench 207’. In certain embodiments, the resonating plate element is attached to the support structure via (at least) one anchoring point 202.
[0107] Fig. 3 schematically shows a cap wafer of the packaged oven-controlled oscillator device on a side facing the resonating element (facing the enclosure) in a top view according to an example embodiment. Fig. 4 schematically shows a cap wafer of the packaged oven-controlled oscillator device on a side facing outside of the packaged apparatus in a top view according to an example embodiment. Fig. 4 depicts the packaged apparatus from above.
[0108] Accordingly, there is provided a packaged semiconductor apparatus, comprising at least one oven-controlled oscillator device 100 of the first aspect or any of its embodiments. In certain embodiments, the packaged semiconductor apparatus is a wafer-level packaged, WLP, apparatus, wherein a cap wafer and the device wafer are bonded together via thermocompression bonding. In certain embodiments, the packaged semiconductor apparatus comprises an enclosure, formed by the cap wafer and the device wafer bonded together. Referring also to Fig. 1, in certain embodiments, the device wafer comprises the handle wafer portion 107 and the device wafer portion 101, 102, 103, 104, 105. In certain embodiments, the handle wafer portion 107 and the device wafer portion 101, 102, 103, 104, 105 are separated from one another by a buried oxide layer 106. In certain embodiments, a cavity 108 is arranged in between the handle wafer portion 107 and the device wafer portion 101, 102, 103, 104, 105 (the cavity being at least underneath the resonating element 110).
[0109] In certain embodiments, the packaged semiconductor apparatus comprises at least one oven-controlled oscillator device 100. In certain embodiments, the packaged semiconductor apparatus comprises a plurality of oven-controlled oscillator devices 100. In certain embodiments, the oven-controlled oscillator device(s) 100 recite in the enclosure. In certain embodiments, the enclosure is in vacuum. As shown in Fig. 3, in certain embodiments, the cap wafer of the packaged semiconductor apparatus comprises a recess 302. In certain embodiments, the recess 302 is arranged on the cap wafer inside the enclosure, and facing the resonating element 110 (on the inner surface of the cap wafer). In certain embodiments, the recess 302 is arranged vertically above the resonating element 110 (the resonating element 110 being arranged on the device wafer). In certain embodiments, the recess 302 is a thinner material portion (etched cavity-type) than the rest of the cap wafer. In certain embodiments, the recess allows space for the resonating element 110 within the enclosure.
[0110] In certain embodiments, the cap wafer comprises a sealing ring 201’ for bonding the cap wafer and the device wafer (the device wafer comprising also a sealing ring 201). In certain embodiments, the sealing ring 20T is arranged on the cap wafer inside the enclosure, and facing the resonating element 110 (on the inner surface of the cap wafer). In certain embodiments, the sealing ring is formed of two counterparts 201 and 20T, one being on the device wafer (sealing ring 201) and one being on the cap wafer (sealing ring 20T). In certain embodiments, the two counterparts 201, 201’ of the sealing ring are configured to merge with each other upon bonding. In certain embodiments, the sealing rings 201, 20T is of gold. In these embodiments, the bonding is Au-Au thermocompression bonding. In certain embodiments, the sealing ring 201, 201’ is configured to provide a hermetical seal for the packaged semiconductor apparatus.
[0111] In certain embodiments, the cap wafer comprises cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP (on the inner surface of the cap wafer). In certain embodiments, the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP are arranged on the cap wafer inside the enclosure (facing the resonating element 110), as shown in Fig. 3.
[0112] In certain embodiments, the cap wafer comprises external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT (on the outer surface of the cap wafer). In certain embodiments, the external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT are arranged on the external surface of the packaged semiconductor apparatus, as shown in Fig. 4.
[0113] In certain embodiments, the external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT are coupled by through silicon vias 301 (through the cap wafer) to the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP of the oven-controlled oscillator device. In certain embodiments, the external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT are configured to provide electric and mechanical contact from outside into the oven-controlled oscillator device (through the cap wafer). In certain embodiments, the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP are configured to provide electric and mechanical contact from the cap wafer to the oven-controlled oscillator device.
[0114] In certain embodiments, the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP are coupled to the contact points XIN, XOUT, TIN, TOUT (within the enclosure). In certain embodiments, the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP are configured to contact the contact points XIN, XOUT, TIN, TOUT upon bonding. In certain embodiments, the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP and the contact points XIN, XOUT, TIN, TOUT are arranged vertically atop each other (corresponding locations on the device wafer and the cap wafer such that each of them touches the respective counterpart once the package is formed by bonding).
[0115] In certain embodiments, the contact points XIN, XOUT, TIN, TOUT are coupled to through silicon vias 301, the through silicon vias 301 being formed between the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP and the external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT. In certain embodiments, the electrical contact to the oven-controlled oscillator device 100 is provided from external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT via though silicon vias 301 to the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP and thereafter to the contact points XIN, XOUT, TIN, TOUT.
[0116] In certain embodiments, the external contact pads XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT enable wirebonding of the packaged semiconductor device. In certain embodiments, the external contact pads XIN-EXT, XOUT-EXT, are wirebonded to measure (detect, sense, determine) the resonance frequency for providing the parameter of interest. In certain embodiments, the external contact pads TIN-EXT, TOUT-EXT are wirebonded to use the trimming layer 101 of the oven-controlled oscillator device 100 as a temperature sensor and / or a heater.
[0117] In certain embodiments, the cap wafer of the packaged semiconductor apparatus comprises a redistribution layer, wherein the redistribution layer is arranged on the cap wafer inside the enclosure and facing the resonating element (inner surface of the cap wafer). In certain embodiments, the redistribution layer is of gold. In certain embodiments, the redistribution layer is patterned to form the sealing ring 20T and the cap contact pads XIN-CAP, XOUT-CAP, TIN-CAP, TOUT-CAP on the cap wafer (on the inner surface of the cap wafer). Fig. 5 schematically shows an oven-controlled oscillator device 100 in a top view with temperature sensing and heating decoupled according to an example embodiment. Fig. 5 shows otherwise an analogous device in comparison to Figs. 2a and 2b, except for the heating and temperature sensing of the device being decoupled. In this embodiment, the heating of the device and the temperature sensing are separated.
[0118] In certain embodiments, the resonating element 110 comprises a first trimming layer (material, meander) 101a and the second trimming layer (material, meander) 101b. In certain embodiments, the first trimming layer 101a is used for heating the device. In certain embodiments, the second trimming layer 101b is used for temperature sensing. In certain embodiments, the first trimming layer 101a and the second trimming layer 101b are of same material as disclosed earlier in context of the trimming layer 101. In certain embodiments, the first trimming layer 101a and the second trimming layer 101b are of same material with one another. In certain embodiments, the first trimming layer 101a and the second trimming layer 101b are of different materials of one another.
[0119] In certain embodiments, the trimming layer is ‘divided’ into two separate pathways 101a and 101b for the charge carriers to move across the resonating element 110. In certain embodiments, the charge carriers are configured to enter the first trimming layer 101a (pathway) via contact point TDRI E and exit the first trimming layer 101a via contact point TGND. In certain embodiments, the charge carriers are configured to enter the second trimming layer 101b (pathway) via contact point TSENSE and exit the first trimming layer 101b via contact point TGND. Thus, the first trimming layer 101a and the second trimming layer 101b share a ground contact point TGND. Also, in comparison to Figs. 2a and 2b, the oven-controlled oscillator device comprises yet another ‘extra’ contact point TDRI E I TSENSE. In certain embodiments, the device comprises more than four contact points, such as five contact points.
[0120] As the electric current travels across the resonating element 110 via the second trimming layer 101b, there is resistance. The resistance of the second trimming layer 101b between TSENSE and TGND is used to read the device temperature. In certain embodiments, the reading of the resistance enables providing in situ temperature sensing.
[0121] In certain embodiments, the oven-controlled oscillator device 100 is heated by the electric current flowing through the first trimming layer 101a. In certain embodiments, the current applied to TDRI E (and exiting via TGND) is modulated to heat the device 100. Accordingly, in certain embodiments, the oven-controlled oscillator device 100 comprises a temperature sensor and a heater on the device itself. In certain embodiments, these functionalities are coupled to one another (using the same trimming layer 101, as shown in Figs. 2a and 2b). In certain embodiments, these functionalities are decoupled from one another (using two trimming layers 101a and 101b as shown in Fig. 5). Either way, the need for a separate temperature sensor and a separate heater is omitted.
[0122] In certain embodiments, the first trimming layer 101a is coupled to the contact point TDRI E via a TDRI E trace 203a. In certain embodiments, the second trimming layer 101a is coupled to the contact point TSENSE via a TSENSE trace 203b. In certain embodiments, the traces 203a and 203b are of the same material as the trimming layers 101a and 101b, respectively.
[0123] Fig. 6 and Fig, 7 schematically show a cap wafer of the packaged oven-controlled oscillator device with temperature sensing and heating decoupled on side facing the resonating element, and on side facing outside, respectively, in a top view according to an example embodiment. Fig. 6 shows otherwise an analogous solution in comparison to Figs. 3, except for the heating and temperature sensing of the device being decoupled. Fig. 7 shows otherwise an analogous solution in comparison to Figs. 4, except for the heating and temperature sensing of the device being decoupled. In this embodiment, the heating of the device and the temperature sensing are separated.
[0124] As shown in Fig. 6, in certain embodiments, the cap wafer comprises cap contact pads TSENSE-CAP, TDRI E-CAP, TGND-CAP (on the inner surface of the cap wafer, facing the resonating element 110). As shown in Fig. 7, in certain embodiments, the cap wafer comprises external contact pads TSENSE-EXT, TDRI E-EXT, TGND-EXT (on the outer surface of the cap wafer, on the external surface of the packaged semiconductor apparatus).
[0125] Analogously as what has been described in context of Figs. 3 and 4, in the embodiments of Figs. 5, 6 and 7: in certain embodiments, the contact points TSENSE, TDRI E, TGND are coupled to through silicon vias 301, the through silicon vias 301 being formed between the cap contact pads TSENSE-CAP, TDRI E-CAP, TGND-CAP and the external contact pads TSENSE-EXT, TDRI E-EXT, TGND-EXT. In certain embodiments, the electrical contact to the oven-controlled oscillator device 100 is provided from external contact pads TSENSE-EXT, TDRI E-EXT, TGND-EXT via though silicon vias 301 to the cap contact pads TSENSE-CAP, TDRI E-CAP, TGND-CAP and thereafter to the contact points TSENSE, TDRI E, TGND. The contact points XIN, XOUT, the cap contact pads XIN-CAP, XOUT-CAP, and the external contact pads XIN-EXT, XOUT-EXT function analogously as what has described in the context of Figs. 2a, 2b, 3 and 4. In certain embodiments, the device comprises more than four cap (and external) contact pads, such as five contact points.
[0126] 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 avoiding ageing-related frequency drift issues (that are typically proportional to top electrode volume). Therefore, a thin top electrode layer, having a thickness of less than 100nm, is preferred.
[0127] A further technical effect is reducing the complexity of an oven-controlled oscillator, such as oven-controlled MEMS oscillator (OCMO), structure by arranging the heater element and the temperature sensor at the resonating element of the device itself. In a conventional OCMO, the heater element and temperature sensor are typically separated from the device itself, which typically leads to larger time constant between the measured parameters and complex structures. A further technical effect is enabling reading in-situ device temperature by the oven-controlled oscillator itself (by reading the resistance between TIN and TOUT).
[0128] A further technical effect is enabling trimming of the oscillator device post wafer level packaging (WLP), and thereby causing little to no impact on the characteristics of the oscillator device. Typically, when oscillator devices are trimmed prior to packaging, the characteristics, such as electrical characteristics, of the device may be negatively impacted.
[0129] A further technical effect is avoiding or reducing top electrode material reflowing issues due to passivating the top electrode material by the dielectric layer. Similarly, a further technical effect is avoiding or reducing top electrode material ageing due to passivating the top electrode material by the dielectric layer.
[0130] A further technical effect is reducing the top electrode material needed. Namely, the top electrode metal thickness is preferably kept to minimal thickness. This alleviates possible ageing and / or reflow problems of the top electrode material layer. The top electrode material layer does not need to be high density (to the contrary, when top electrode material layer is also trimming material layer, the top electrode material layer should be high density and significant thickness for trimming purposes). This enables more flexibility in the design of the oscillator device. A further technical effect is allowing decoupling of trimming layer and top electrode layer functions. Conventionally, if same material layer is used both for top electrode and for trimming, this particular material must meet the requirements of both simultaneously. Namely, in accordance with certain embodiments of the present disclosure, the trimming layer does not need to be highly conductive, thick or cover most of the resonating element area. This enables more flexibility in the design of the device.
[0131] 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.
[0132] 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.
[0133] 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. An oven-controlled oscillator device (100), comprisinga resonating element (110) having a top electrode layer (103),a dielectric layer (102) on top of the top electrode layer (103), anda trimming layer (101) on top of the dielectric layer (102).
2. The oven-controlled oscillator device (100) of claim 1 , wherein the top electrode layer (103) is of high electrical conductivity material having conductivity the range of 104to 108S / m.
3. The oven-controlled oscillator device (100) of claim 1 or 2, wherein the trimming layer (101) is of a high-density material having density at least 10 g / cm3.
4. The oven-controlled oscillator device (100) of any preceding claim, wherein the trimming layer (101) is of a material having linear temperature coefficient of resistance, TCR.
5. The oven-controlled oscillator device (100) of any preceding claim, wherein the oven-controlled oscillator (100) is an oven-controlled microelectromechanical systems, MEMS, oscillator, OCMO.
6. The oven-controlled oscillator device (100) of any preceding claim, wherein the trimming layer (101) is patterned to cover the resonating element (110) only partially.
7. The oven-controlled oscillator device (100) of claim 6, wherein the trimming layer (101) is patterned to run through the resonating element (110) from one anchoring point to another anchoring point of the resonating element (110).
8. The oven-controlled oscillator device (100) of claim 6 or 7, wherein the trimming layer is patterned to meander across the resonating element (110) from one anchoring point to another anchoring point of the resonating element (110).
9. The oven-controlled oscillator device (100) of claim 6, 7, or 8, wherein the trimming layer (101) is patterned selectively to maximise resistance of the trimming layer (101).
10. The oven-controlled oscillator device (100) of any preceding claim, comprising a temperature sensor and a heater on the device itself.
11. The oven-controlled oscillator device (100) of claim 10, wherein the trimming layer (101) is configured to provide a temperature sensor and a heater for the oven-controlled oscillator.
12. The oven-controlled oscillator device (100) of any preceding claims, comprising contact points (XIN, XOUT, TIN, TOUT), coupled to through silicon vias (301) connected to external pads (XIN-EXT, XOUT-EXT, TIN-EXT, TOUT-EXT).
13. The oven-controlled oscillator device (100) of claim 12, wherein two of the contact points are for sensing a parameter of interest (XIN, XOUT), and at least two of the contact points are for temperature sensing (TIN, TOUT).
14. The oven-controlled oscillator device (100) of claim 13, wherein the sensing of the parameter of interest comprises sensing the frequency of the device.
15. A packaged semiconductor apparatus, comprising at least one oven-controlled oscillator device (100) of any claim 1-14.