Constant temperature control oscillator of micro electro mechanical system

Abstract

A micro-electro-mechanical system (MEMS) device is provided with singulation for thermal management. In one illustrative embodiment, the apparatus may include: a heated section including a first die and a second die, where: the first die includes a heater and the second die is coupled to the first die and includes a temperature sensor and a MEMS resonator; and a non-heated section communicatively coupled to the heated section and including a third die. The third die may receive a first signal associated with the temperature sensor and provide a second signal to the first die associated with the heater based on the first signal.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 429,898, filed on December 2, 2022; U.S. Provisional Application No. 63 / 430,615, filed on December 6, 2022; U.S. Provisional Application No. 63 / 434,909, filed on December 22, 2022; and U.S. Provisional Application No. 63 / 434,922, filed on December 22, 2022, each of which is incorporated herein by reference for all purposes. Background of the Invention

[0003] An oscillator can be an electronic circuit that generates a periodic signal. Oscillators can be temperature - sensitive because the frequency of oscillation can depend on the physical properties of its oscillating elements, and those physical properties can change with temperature. For example, material properties that govern mechanical behavior, such as the stiffness of a spring, the elasticity of a crystal, or the elasticity or dimensions of a micro - electromechanical system (MEMS) resonator, are affected by temperature. Brief Description of the Drawings

[0004] Regarding the following discussion and particularly regarding the drawings, it is emphasized that the details shown are examples for illustrative discussion purposes and are presented to provide a description of the principles and concepts of the present disclosure. In this regard, no attempt is made to show implementation details beyond those necessary for a basic understanding of the present disclosure. The following discussion, in conjunction with the drawings, enables those skilled in the art to understand how embodiments in accordance with the present disclosure can be practiced. In the various drawings and the supporting description, like or identical reference numerals may be used to identify or otherwise refer to like or identical elements. In the drawings:

[0005] Figure 1 An oven - controlled oscillator according to some embodiments is illustrated.

[0006] Figure 2 Another oven - controlled oscillator according to various embodiments is illustrated.

[0007] Figure 3 An electronic circuit segmentation according to some embodiments is illustrated.

[0008] Figures 4 - 8 A package according to various embodiments is illustrated.

[0009] Figures 9A - 9D An insulator according to some embodiments is illustrated.

[0010] Figure 10 A heater according to various embodiments is illustrated. Detailed Description

[0011] Although the present technology may admit many different forms of embodiments, several specific embodiments are shown in the drawings and will be described in detail herein. It should be understood that the present disclosure should be regarded as an illustration of the principles of the present technology and is not intended to limit the present technology to the embodiments shown.

[0012] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present technology. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that when used in this specification, the terms "comprises", "comprising", "includes" and / or "including" specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0013] As used herein, "A, B, and / or C" shall be understood to mean only A, only B, only C, A and B, A and C, B and C, or A, B, and C. In addition, "at least one of A, B, and C" shall be understood to mean only A, only B, only C, A and B, A and C, B and C, or A, B, and C. In other words, combinations of elements (e.g., A, B, and C). Additionally or alternatively, "A, B, and / or C" and "at least one of A, B, and C" may mean arrangements of elements (e.g., A, B, and C). There can be any number of elements (e.g., A, B, C, and D; A, B, C, D, and E; etc.).

[0014] It will be understood that like or similar elements and / or components referred to herein may be identified by like reference numerals throughout the drawings. It will also be understood that several of the drawings are merely schematic representations of the present technology. Therefore, for clarity of illustration, some of the components may be shown out of proportion to their actual size. Moreover, various combinations of structures, components, materials, and / or elements other than those specifically shown are contemplated and within the scope of the present technology.

[0015] Overview

[0016] An electronic oscillator is an electronic circuit that generates periodic oscillating electronic signals (such as sine waves and square waves). The electronic oscillator can provide these electronic signals to synchronous digital electronic devices, such as communication, networking, computing, measurement, and timekeeping circuits and systems. The electronic oscillator can include one or more mechanical resonators (e.g., quartz crystals, microelectromechanical systems (MEMS) resonators, ceramic resonators, etc.), which oscillate with a greater amplitude at some frequencies (called resonance frequencies) than at other frequencies. For example, a quartz crystal can change its shape under an electric field, which can be referred to as electrostriction or the inverse piezoelectric effect. As a further non-limiting example, a MEMS resonator can include a mechanical structure with an inherent resonance frequency, which can oscillate by electrostatic or piezoelectric forces to generate a constant frequency.

[0017] The electronic oscillator can include a circuit that works in conjunction with the resonator to provide a periodic oscillating signal. The resonance frequency of the resonator may vary with temperature. By keeping the temperature of the resonator within an oven temperature range (e.g., maintained at a target oven temperature, such as 95°C ± 1%), the effect of temperature sensitivity can be reduced (e.g., the change in frequency within an operating temperature range, such as 0°C to +70°C, -40°C to +85°C, -55°C to +125°C, etc.). Moreover, some circuits (e.g., oscillator circuits, voltage references, etc.) can benefit from temperature control. Maintaining the resonator and / or circuit at a higher oven temperature range (e.g., 105°C ± 1%) may consume more power than a lower oven temperature range (e.g., 95°C ± 1%) because maintaining the lower oven temperature range may require less power from the heater. Additionally or alternatively, the heater power can be reduced by limiting the amount of heat lost by the electronic oscillator due to heat leakage from the oven.

[0018] Temperature-Controlled Oscillator

[0019] Figure 1Illustrated is an oven controlled crystal oscillator (OCXO) 100A according to some embodiments. The cavity 120A can be a temperature control chamber that can maintain the resonator(s) 130A and / or the circuit blocks of the circuit 140A within an oven temperature range (e.g., maintained at a target oven temperature, such as 95°C, ±1%), hereinafter referred to as the target temperature. For example, the target temperature can be selected to be at or above (e.g., with a guard band) the upper limit of an operating temperature range (e.g., 0°C to +70°C, -40°C to +85°C, -55°C to +125°C, etc.). The operating temperature range can be the range of the temperature outside the package 110A within which the OCXO 100A can operate within a predetermined specification (such as in a data sheet). The heater(s) 144A (and / or the heater(s) in the resonator(s) 130A ( Figure 1 not depicted in)) can generate heat to raise and / or maintain the resonator(s) 130A and / or the circuit blocks of the circuit 140A at the target temperature. In this way, the temperature experienced by the resonator(s) 130A and / or the circuit blocks of the circuit 140A can always be higher than the temperature outside the package 110A. The temperature outside the package 110A can be referred to as the ambient temperature. The effect of the change in the ambient temperature on the resonator(s) 130A and / or the circuit blocks of the circuit 140A can be limited by the OCXO 100A.

[0020] As shown, the resonator 130A can be coupled to the electronic circuit 140A, and the electronic circuit 140A can be coupled to an insulator (separator) 150A, such as by using die attach. Die attach can be adhesive die attach (e.g., polyimide, epoxy, silicone, etc., and can include fillers to optimize the combination and arrangement of the thermal, mechanical, and electrical properties of the adhesive), eutectic die attach (e.g., eutectic alloy), or other types of die-to-die bonding. Heat can be lost from the resonator(s) 130A through the bond wires 122A, from the electronic circuit 140A through the bond wires 124A and the insulator 150A, and from the cavity 120A through the package 110A (including the lid 112A). The package 110A can thermally insulate the resonator(s) 130A and / or the circuit blocks of the circuit 140A from the environment outside the package 110A (e.g., the ambient temperature) (e.g., having a thermal resistance θ > 100°C / W).

[0021] As a non-limiting example, resonator(s) 130A and / or circuit 140A can be semiconductor die (e.g., small pieces of semiconductor material such as silicon, carbon (e.g., diamond, diamond-like carbon, carbon nanotubes, and graphite), silicon germanium, germanium, III-V compounds (e.g., composed of boron, aluminum, gallium, indium, nitrogen, phosphorus, arsenic, and tin), etc. on which resonator(s) and / or circuit(s) can be fabricated). Additionally, other compound semiconductors from columns 4, 13, 14, and 15 of the periodic table such as silicon carbide, aluminum nitride, and oxides of zirconium and hafnium can be used. Moreover, various doping levels can be applied to the foregoing materials. Resonator(s) 130A can optionally include temperature sensor(s) 132A. Circuit 140A can optionally include temperature sensor(s) 142A. Bond wires 122A and 124A can provide the interconnections between resonator 130A and circuit 140A and between circuit 140A and package 110A, respectively. Bond wires 122A and 124A can each include a combination and arrangement of aluminum, copper, silver, gold, etc. Other interconnections such as solder balls, through-silicon vias (TSVs), etc. can be used. Package 110A can be a ceramic package (e.g., alumina (Al2O3) multi-layer ceramic package), a plastic package (e.g., small outline integrated circuit (SOIC), small outline transistor (SOT), quad flat no-lead (QFN), etc. packages), and / or a metal package (e.g., TO-3, TO-41, etc.). Lid 112A can be plastic, metal, a combination thereof, or other materials.

[0022] Electronic circuit 140A can operate in conjunction with resonator(s) 130A to generate a periodic oscillating electronic signal. For example, electronic circuit 140A can include a sustaining amplifier having gain. The sustaining amplifier can drive resonator 130A to move continuously and generate an output signal at a resonant frequency approximately for synchronizing digital electronic devices ( Figure 1 not depicted therein). The electronic circuit can additionally perform temperature compensation, frequency synthesis, temperature measurement, heater control, clock distribution, etc. As a non-limiting example, electronic circuit 140A can include a combination and arrangement of buffers, heaters, amplifiers, volatile and non-volatile memories, filters, phase-locked loops (PLLs), voltage-controlled oscillators (VCOs), analog-to-digital converters (ADCs), digital-to-analog converters (DACs), etc.

[0023] The electronic circuit 140A can generate heat (in addition to the heat generated by the heater(s) 144A). For example, the circuit 140A can consume power on the order of 10 - 200 mW, which can heat the cavity 120A by 1° - 20 °C. In this way, the electronic oscillator can be referred to as self-heating. Accordingly, the target temperature can be additionally or alternatively selected as the maximum value of the operating temperature range plus the heat generated by the self-heating plus the guard band.

[0024] By limiting the amount of self-heating, the amount of heat generated by the heater(s) 144A can be reduced because the target temperature can be set lower (compared to using more self-heating). In this way, the power consumed by the heater(s) 144A can be reduced, and the OCXO 100A can consume less power. As described below, by moving some circuit blocks to another circuit die where the temperature is not controlled, the amount of power consumed by the circuit 140A can be advantageously reduced. For example, within the same OCXO, there can be a temperature-controlled "heated" portion and a temperature-uncontrolled "non-heated" portion. The circuit die in the "heated" portion can have fewer circuit blocks and thus consume less power than, for example, the circuit 140A. The self-heating of the circuit die in the "heated" portion can also be reduced accordingly. Because the self-heating is reduced, the target temperature can be lowered.

[0025] In addition, when the power consumption of the circuit die is high, it can limit the maximum thermal resistance of, for example, the package 110A and / or the insulator 150A because the self-heating may increase with increasing thermal resistance. When the heat generated by the circuit 140A plus the ambient temperature is higher than the target temperature, the resonator(s) 130A and / or the circuit blocks of the circuit 140A may not be able to operate at the target temperature. Recall that it is assumed that the OCXO keeps the resonator and / or some circuit blocks operating at the target temperature. Accordingly, the thermal resistance of the insulator 150A and / or the package 110A can be reduced to lower the temperature of the resonator(s) 130A and / or the circuit blocks of the circuit 140A to the target temperature. When the OCXO 100A is started at the ambient temperature, the heater(s) 144A can consume more power to heat the resonator(s) 130A and / or the circuit blocks of the circuit 140A to the target temperature because the heat generated by the heater(s) 144A may leak through them due to the lower thermal resistance of the insulator 150A and / or the package 110A.

[0026] However, when the power consumption of the "heated" circuit is reduced, the thermal resistance of the package 110A and the insulator 150A can increase. This can also result in a reduction in the total power consumption of the OCXO 100A, since the heater(s) 144A can consume less power. Less power may be required to heat the resonator(s) 130A and / or the circuit blocks of the circuit 140A to the target temperature from the heater(s) 144A, since less heat leaks out through the insulator 150A and / or the package 110A due to their higher thermal resistance.

[0027] Heated and non-heated segmentation

[0028] Figure 2 An OCXO 100B according to some embodiments is shown. Except as described below, the OCXO 100B may also have at least some of the characteristics of the OCXO 100A ( Figure 1 ). The OCXO 100B may include a heated section 210B and a non-heated section 220B. Here, "heated" may refer to heating using a heater (e.g., the heater(s) 144B), and "non-heated" may refer to not being heated by a heater (but self-heating may be present). The heated section 210B may include the package 110B. The package 110B may include a lid 112B. The heated section 210B may be heated to the target temperature by a combination and arrangement of the heater(s) 144B, the heater(s) in one or more of the resonator(s) 130B1 ( Figure 2 not shown in) and self-heating. The connections 114B and 232B may each be a combination and arrangement of pins, solder balls, etc., and may provide interconnections between the package 110B and the substrate 240B and between the package 230B and the substrate 240B, respectively. The substrate 240B may provide an interconnection between the package 110B and the package 230B. The resonator(s) 130B1 may optionally include one or more temperature sensors 132B. The circuit 140B1 may optionally include one or more temperature sensors 142B. The non-heated section 220B may include the package 230B. The package 230B may be a ceramic package (e.g., an alumina (Al2O3) multi-layer ceramic package), a plastic package (e.g., SOIC, SOT, QFN, etc. packages), and / or a metal package (e.g., TO-3, TO-41, etc.).

[0029] The substrate 240B may be a dielectric having one or more layers, such as a printed circuit board, which may interconnect electronic components such as the package 110B, the package 230B, and optionally other electronic components ( Figure 2are connected to each other (not shown in the figure). For example, the substrate 240B may be composed of a combination and arrangement of aluminum, copper, ceramics, phenolic paper (e.g., FR-1 and FR-2), woven fiberglass (e.g., FR-4), polyimide foil, polyimide-fluoropolymer composite foil, etc. The cover plate 250B may seal the package 110B and / or the package 230B on the substrate 240B, for example, to provide physical protection against environmental conditions such as moisture, shock, etc. The cover plate 250B may be plastic, metal, a combination thereof, or other materials. As a further non-limiting example, the cover plate 250B may be optional or an encapsulation. The thermal vias 242B may be small holes passing through the substrate 240B and filled with a thermally conductive material such as copper and / or aluminum. The thermal vias 242B may act as heat sinks and draw heat from the package 230B.

[0030] As shown in the figure, a circuit 140B1 may be present in the heated section 210B, and a circuit 140B2 may be present in the non-heated section 220B. The constitution of the circuit 140A ( Figure 1 ) may be divided between the circuit 140B1 and the circuit 140B2. For example, the constitution of the circuit 140A close to the resonator 130B1 (e.g., in the heated section 210B) may be beneficial to the operation of the resonator 130B1. Other constitutions of the circuit 140A - deployed in the heated section 210B that are not beneficial to the operation of the resonator 130B1 and / or may cause self-heating - may be deployed in the non-heated section 220B. For example, the constitution of the circuit 140B1 may consume about 1 - 10 mW of power, excluding the heater 144B, while the constitution of the circuit 140B2 may consume about 10 - 200 mW of power.

[0031] Optional resonator(s) 130B2 may be coupled to the circuit 140B2. Although the heater 144B is shown in the circuit 140B1, alternatively or additionally, a heater may be present in the resonator(s) 130B1 ( Figure 2 (not shown in the figure).

[0032] The cavity 120B can be filled with a fluid having a lower thermal conductivity than, for example, air (26.2 mW / (m K)) and / or nitrogen (26.0 mW / (m K)). In this way, heat loss through the cavity 120B can be reduced and heater power consumption can be lowered. Gases having a relatively low thermal conductivity, such as xenon (Xe; 5.5 mW / (m K), P = 0), krypton (Kr; 9.5 mW / (m K), P = 0), dichlorodifluoromethane (CCl2F2; 9.9 mW / (m K)), carbon dioxide (CO2; 16.8 mW / (m K)), and argon (Ar; 17.9 mW / (m K)) (combinations and permutations), can be used to fill the cavity 120B. The exemplary thermal conductivities of the gases are at 300°K and pressure P = 1 bar unless otherwise stated. As a further non-limiting example, the cavity 120B can be a vacuum (e.g., 1.0 Ba > P > 1.0 μBa) (e.g., the package 110B can be vacuum-sealed). Those of ordinary skill in the art will recognize that large molecule and / or large atom gases (and their combinations and permutations) often can have low thermal conductivities. Accordingly, the foregoing list is provided by way of example only and is not limiting.

[0033] Combinations and permutations of low thermal conductivity gases and vacuums can be used together in the cavity 120B. This can provide a lower thermal conductivity than using a single gas and / or vacuum alone. Optimal gas selection criteria can include: no chemical reaction (no reaction with the package 110B and / or the contents of the package 110B), chemical inertness, environmental friendliness, non-toxicity, manageable in the package assembly environment, low cost, etc.

[0034] An additional benefit of large molecule and / or large atom gases is that they can be more easily sealed and have a lower leak rate than small molecule and / or small atom gases such as H2 (small molecule) and / or He (small atom). Accordingly, using large molecule and / or large atom gases can result in improved package durability and reliability.

[0035] The package 110B can be sealed to maintain the gas and / or vacuum in the cavity 120B. For example, the package 230B can be hermetically sealed.

[0036] (One or more) resonators 130B1 can be other MEMS devices that can benefit from thermal management. By way of illustration and not limitation, (one or more) resonators 130B1 can be gyroscopes, accelerometers, vibrometers, magnetic field sensors, transducers, chemical detectors, and / or other MEMS devices. The chemical detector can be a gas sensor (e.g., hydrogen, helium, ammonia, carbon monoxide, carbon dioxide, nitrogen oxides, and various pollutants). The OCXO 100B can expose the MEMS device (e.g., (one or more) resonators 130B1) to a gas (e.g., the lid 112B and / or the cover plate 250B can be breathable and / or ventilated).

[0037] Circuit partitioning

[0038] Figure 3 An OCXO 100C according to some embodiments is shown. Figure 3 Illustrated is a partitioning of the electronic circuit functionality / operation between a circuit 140C1 (e.g., in the heated section 210B ( Figure 2 )) and a circuit 140C2 (e.g., in the non-heated section 220B ( Figure 2 )) according to some embodiments. The OCXO 100C can have at least some of the characteristics of the OCXOs 100A and 100B ( Figure 1 and Figure 2 ).

[0039] As shown, the circuit 140C1 in the package 110C can be connected to (one or more) resonators 130C1. (One or more) resonators 130C1 can optionally include one or more temperature sensors 132C and / or one or more heaters 134C. The circuit 140C1 can provide (one or more) periodic oscillation signals generated using (one or more) resonators 130C1 to the circuit 140C2 via a CLK signal 350 hereinafter referred to as a reference clock. The circuit 140C1 and the circuit 140C2 can communicate with each other (e.g., sensor, condition / status, and control information) via communication 330. For example, the communication 330 can be a combination and arrangement of discrete signals (e.g., temperature sensor 142C and / or 132C outputs from the circuit 140C1 to the circuit 140C2, heater control from the circuit 140C2 to the circuit 140C1, data from the system logic 328 (e.g., RAM and / or ROM), etc.), serial buses (e.g., Serial Peripheral Interface (SPI), I2C, etc.), parallel buses, etc.

[0040] Circuit 140C1 may include one or more sustain circuits 310, an optional temperature sensor 142C, a heater driver 312, and one or more heaters 144C. One or more sustain circuits 310 may initiate and sustain periodic oscillations in one or more resonators 130C1. For example, one or more sustain circuits 310 may be one or more amplifiers with a gain greater than 1. The optional temperature sensor 142C may sense the temperature in circuit 140C1, which may be used to determine the temperature of one or more resonators 130C1 and / or circuit blocks of circuit 140C1. The optional temperature sensor 142C may be a combination and arrangement of a resistance-based temperature sensor (e.g., a resistance temperature detector (RTD) or similar device), a discrete-circuit-based sensor (e.g., a bipolar junction transistor (BJT), a diode (bipolar junction), a MOSFET transistor, or similar device), and other types of temperature sensors (e.g., a thermocouple, a thermopile, a sonic thermometer, a variable conductance thermometer, a variable capacitance thermometer, a variable inductance thermometer, etc.). The optional temperature sensor 132C may sense the temperature on the silicon die of resonator 130C1. The optional temperature sensor 132C may be a combination and arrangement of a resonator whose resonant frequency varies with temperature in a predetermined manner, a resistance-based temperature sensor (e.g., an RTD or similar device), a discrete-circuit-based sensor (e.g., a BJT or similar device), and other types of temperature sensors.

[0041] For example, one or more resonators 130C1 may be temperature-stable resonators (e.g., varying by about 1 PPM / °C or less), and temperature sensor 132C may be a temperature-sensitive resonator (e.g., varying by about 5 PPM / °C or less). In some embodiments, the temperature-stable resonator and the temperature-sensitive resonator may be located in a resonator having temperature-stable and temperature-sensitive resonant modes. Periodic signals from the temperature-stable and temperature-sensitive resonators / modes may be processed to generate a temperature-compensated reference periodic signal and a temperature measurement. The examples of temperature stability (e.g., 1 PPM / °C) and temperature sensitivity (e.g., 5 PPM / °C) are provided for illustrative purposes. Other examples with different values of temperature stability and temperature sensitivity may be used. A temperature sensor using a MEMS resonator is further described in U.S. Patent No. 10,247,621, titled "High Resolution Temperature Sensor", which is incorporated herein by reference for the disclosure of temperature sensing.

[0042] The heater driver 312 can control the amount of heat generated by the heater(s) 144C and / or the heater(s) 134C. For example, the heater driver 312 can be a current control circuit that supplies a varying current based on the temperature measured by the temperature sensors 132C and / or 142C. The heater(s) 144C and / or the heater 134C can generate heat to maintain the circuit blocks of the resonator(s) 130C1 and / or the circuit 140C1 at a target temperature. For example, the heater(s) 144C and / or the heater 134C can be a combination and arrangement of diffused resistors, ion-implanted resistors, thin-film resistors, polysilicon resistors, transistors (e.g., BJTs and MOSFETs), etc. As a non-limiting example, the circuit 140C1 can consume about 1 - 10 mW and raise the temperature in the package 110C by about 1 - 10 °C (e.g., due to self-heating), excluding the effects of the heaters 144C and the heater 134C.

[0043] The circuit 140C2 can include an optional maintenance circuit 320, a numerically controlled oscillator 321, a temperature compensation 322, a heater control 324, an output driver(s) 326, and system logic 328 (e.g., volatile memory (e.g., RAM, DRAM, SRAM, etc.), non-volatile memory (e.g., ROM, EEPROM, FLASH, etc.), a processor (e.g., logic, state machine, microprocessor, etc.), a communication port (e.g., SPI, I2C, etc.), etc.). The communication port in the system logic 328 can communicate with an external computer system before and / or after the electronic oscillator is sold to configure the circuit 140C2. For example, the coefficients used by the temperature compensation 322 can be programmed into the memory of the system logic through the communication 340 and the communication port in the system logic 328. As a further non-limiting example, the end user can configure the output frequency through the communication 340 and the communication port in the system logic 328.

[0044] The optional maintenance circuit 320 can initiate and maintain periodic oscillations in the optional resonator(s) 130C2. For example, the optional maintenance circuit 320 can be one or more amplifiers with a gain greater than 1. The numerically controlled oscillator 321 can use the reference clock generated by the circuit 140C1 as an input and can perform functions such as reducing the jitter of the clock generated by the circuit 140C1, synthesizing other clock frequencies based on the clock generated by the circuit 140C1, enabling the ability to adjust the clock frequency based on an input through the communication port 340, etc. For example, the numerically controlled oscillator 321 can include a digital-to-analog converter ( Figure 3A voltage controlled oscillator (VCO) driven by a control signal (not depicted in the figure). Optionally, one or more resonators 130C2 can communicate with circuit 140C2. For example, the optional one or more resonators 130C2 can provide a low jitter clock reference for the numerically controlled oscillator 321.

[0045] Temperature compensation 322 can compensate for the change in the resonance frequency of one or more resonators 130C1 within its operating temperature range. In operation, one or more heaters 144C can generate heat to maintain the circuit blocks of one or more resonators 130C1 and / or circuit 140C1 at a target temperature. When the OCXO 100C is started (e.g., the OCXO 100C is at the ambient temperature rather than the target temperature) or when the ambient temperature changes / fluctuates, the temperature of the circuit blocks of one or more resonators 130C1 and / or circuit 140C1 may not be at the target temperature. Here, for example, the relationship between the temperature and frequency of one or more resonators 130C1 can be approximated by a polynomial function. The polynomial function can approximate the change in the desired frequency from a specific temperature (e.g., determined by temperature sensor 132C and / or temperature sensor 142C), and the numerically controlled oscillator 321 can adjust its multiplication factor value based on the output of the polynomial function to compensate for the change in frequency caused by one or more resonators 130C1 due to deviation from the target temperature.

[0046] The heater controller 324 can use the output from temperature sensor 132C and / or temperature sensor 142C to determine the temperature of the circuit blocks of one or more resonators 130C1 and / or circuit 140C1, and control one or more heaters 144C and / or heater 134C (e.g., increase, decrease, and / or maintain the amount of heat generated by them). The heater control can generate analog and / or digital control signals (e.g., a digital value corresponding to the amount of heater current) and provide it to the heater driver 312 through communication 330.

[0047] (One or more) output drivers 326 can generate an output signal for an electronic oscillator. The output signal can be generated using a combination and arrangement of (one or more) resonators 130C1, (one or more) resonators 130C, temperature compensation 322, and numerically controlled oscillator 321. (One or more) output drivers 326 can include a combination and arrangement of current-controlled switches, voltage-controlled switches, bipolar junction transistors (BJTs), junction gate field effect transistors (JFETs), (n-type and / or p-type) metal oxide semiconductor field effect transistors (MOSFETs), etc. As a non-limiting example, (one or more) output drivers 326 can be complementary metal oxide semiconductor (CMOS) inverters, totem pole outputs, etc., to generate a combination and arrangement of CMOS, TTL, LVCMOS, etc. signals at output 360. As a further non-limiting example, (one or more) output drivers can additionally or alternatively be differential, such as a combination and arrangement of low voltage differential signaling (LVDS), low voltage positive emitter coupled logic (LVPECL), current mode logic (CML), etc. at output 360.

[0048] Although Figure 3 Solder bumps for interconnection are depicted in — between (one or more) resonators 130C1 and circuit 140C1 and between (one or more) resonators 130C2 and circuit 140C2, but other interconnections, such as bond wires, can be used.

[0049] Although circuits 140C1 and 140C2 are depicted as having certain functions (e.g., (one or more) sustain circuits 310, optional temperature sensor 142C, heater driver 312, (one or more) heaters 144C, optional (one or more) sustain circuits 320, numerically controlled oscillator 321, temperature compensation 322, heater control 324, (one or more) output drivers 326, system logic 328), it should be understood that the combination and arrangement of functions can be split between circuits 140C1 and 140C2. As a non-limiting example, heater control 324 can be located in circuit 140C1.

[0050] Package

[0051] As Figure 2 As shown, the package 110B of the heated section 210 and the package 230B of the non-heated section 220B can be deployed in a planar manner (e.g., adjacent to each other, side by side, etc.) on the substrate 240B. The heated section 210 and the non-heated section 220B can have other spatial orientations. As a non-limiting example, the heated section 210 and the non-heated section 220B can be vertically oriented. Figures 4 - 8Illustrated is the OCXO 100D-100H having vertically oriented heated and non-heated sections according to some embodiments. Each of the OCXO 100D-100H may have at least some of the characteristics of the OCXO 100A-100C( Figures 1 - 3 ), and vice versa, and may have at least some of the characteristics thereof with respect to each other.

[0052] Figure 4 Shown is the OCXO 100D, which includes a package 110D oriented above a substrate 240D. The package 110D may be located in a heated section (e.g., Figure 2 the heated section 210 in Figure 2 ) and includes a lid 112D, a connection 114D, a cavity 120D, a resonator 130D1, a circuit 140D1, and an insulator (separator) 150D. The substrate 240D may be located in a non-heated section (e.g.,

[0053] the non-heated section 220B in Figure 4 ) and includes one or more resonators 130D2 and a circuit 140D2.

[0054] The circuit 140D1 may be electrically and / or thermally coupled to the package 110D via a bonding wire 122D. The package 110D may be electrically and / or thermally coupled to the substrate 240D via a connection 114D. The substrate 240D may be electrically and / or thermally coupled to another substrate, package, module, etc., such as via pins, solder balls, etc. ( Figure 4 not depicted).

[0054] The package 110D may include a cavity 120D' located below the insulator 150D. Since the insulator 150D does not physically contact the package 110D when the insulator 150D is located above the cavity 120D', the amount of heat leaking from the package 110D through the insulator 150D may be reduced.

[0055] As shown, the substrate 240D may include cavities / notches to have sufficient clearance to deploy the package 110D above one or more resonators 130D2 and / or a circuit 140D2. Thermal vias ( Figure 4 not depicted) in the substrate 140D may act as heat sinks for heat generated by one or more resonators 130D2 and / or a circuit 140D2.

[0056] The bonding wire 122D, the connections 232D1, 232D2, and 410D may be a combination and arrangement of bonding wires, solder balls, through-silicon vias (TSVs), etc. For example, a bonding wire 510 may electrically and / or thermally couple the circuit 140E2 to the substrate 240E, as Figure 5As shown in. As shown, the substrate 240E may include cavities / notches to provide sufficient clearance for deploying the package 110E above the bond wires 510, resonator(s) 130E2, and / or circuit 140E2. Figure 6 The package 110F in may include cavities to provide space for resonator(s) 130F2 and / or circuit 140F2. Solder balls may electrically couple resonator(s) 130F2 and / or circuit 140F2 to the substrate 240F. Bond wires, through-silicon vias (TSVs), etc. may be used alternatively or additionally. For example, the bond wire 610 may electrically and / or thermally couple the circuit 140G2 to the substrate 240G, as Figure 7 shown in.

[0057] Figure 8 An OCXO 100H according to some embodiments is shown. As shown, resonator(s) 130H2 and / or circuit 140H2 may be deployed (e.g., mounted / attached) on a surface of the substrate 240H that is opposite to the surface on which the package 110H of the substrate 240H is deployed (e.g., mounted / attached). The connection 810 may be sized sufficiently to create space for resonator(s) 130H2 and / or circuit 140H2 (e.g., such that there is sufficient space to accommodate them when the OCXO 100H is mounted to another substrate, module, package, etc.). The connection 810 may be a combination and arrangement of solder balls, pins, etc.

[0058] Insulator

[0059] Returning to reference Figure 2 , the package 110B may advantageously have a high thermal resistance, e.g., in order to consume less power to maintain a target temperature. In contrast, the package 230B may advantageously have a low thermal resistance, e.g., to dissipate heat generated by the circuit 140B2. The substrate 240B may be designed to advantageously minimize the thermal crosstalk between the package 110B and the package 230B. For example, the substrate 240B may be relatively thermally insulating around the package 110B, and the substrate 240B may be relatively thermally conductive around the package 230B. As a further non-limiting example, metal layer(s), metal trace(s), and / or via(s) (e.g., density, quantity, dimension, geometry, placement, etc.) may be designed for optimal thermal characteristics.

[0060] Generally, a ceramic package may have—a semiconductor die inside the package to a circuit board on which the package is mounted (from junction to ambient), called θ JA—Thermal resistance from - 30 °C / W to about 100 °C / W. Generally, most (e.g., > 95%) of the heat can be dissipated from the semiconductor die to the bottom of the ceramic package, then to the connection (e.g., solder balls, pins, etc.) and then to the circuit board. Generally speaking, the heat dissipation through the bond wires can be negligible (e.g., < 5%).

[0061] In contrast, package 110B can advantageously have a θ of about 100 °C / W to 1500 °C / W. JA . In package 110B, heat can be dissipated through the bottom of package 110B (e.g., ~ 20% - 80%), through bond wire 124B ( ~ 10% - 50%), and through the gas / vacuum in cavity 120B ( ~ 10% - 50%). By having one or more in insulator 150B, the thermal resistance through the bottom of package 110B can be increased. Additionally or alternatively, bond wire 124B can be made thinner to increase the thermal resistance in this path.

[0062] Figures 9A - 9D Examples of insulators 900A - 900D from a top view / bottom view and a side view respectively are shown according to some embodiments. Insulator examples 900A - 900D can include circuits 910A - 910D and insulators 920A - 920D. Circuits 910A - 910D can have Figure 2 at least some of the characteristics of circuit 140B1 in Figure 3 and / or Figure 2 at least some of the characteristics of insulator 150B in

[0063] Figure 9A Conversely. Insulators 920A - 920D can have Figure 9B at least some of the characteristics of insulator 150B in

[0064] Figure 9C Conversely. Insulators 920A - 920D can each include a low - thermal - expansion glass, a low - thermal - expansion ceramic, etc. As a non - limiting example, insulators 920A - 920D can include materials with a thermal resistance less than 2 W / (m K), where W is watt, m is meter, and K is Kelvin temperature. Figure 9DDepicts parallel insulators 920D. The stacked insulators 920C and 930C together can advantageously have a thermal resistance of around 200 °C / W to 1500 °C / W. Although two insulators are provided as examples, more insulators can be stacked. The parallel insulators 920D can advantageously have a thermal resistance of around 200 °C / W to 1000 °C / W. It will be understood that combinations and arrangements of multiple insulators with different sizes, stacks, and / or parallel configurations can be used.

[0065] Heater

[0066] Figure 10 Shows heater example 1000 according to some embodiments. Heater example 1000 is provided only as an example and not a limitation. Heater example 1000 can include circuit 1010, resonator(s) 1020, and bond pads 1040. Circuit 1010 can include heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2. Circuit 1010 can have Figure 2 at least some of the characteristics of circuit 140B1 in Figure 3 circuit 140C1 in Figures 9A - 9D and / or at least some of the characteristics of circuit 910A-910D in Figure 1 resonator(s) 130A in Figure 2 resonator(s) 130B1 in Figure 3 and / or at least some of the characteristics of resonator(s) 130C1 in Figure 1 heater 144A in Figure 2 heater 144B in Figure 3 and / or at least some of the characteristics of heater 144C in

[0067] One or more of heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 can be used to provide heat to resonator(s) 1020. For example, there can be one of heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 or a combination thereof. Although heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 are shown as having the length of an adjacent side of resonator(s) 1020, they can each be longer or shorter. Heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 can each be a combination and arrangement of diffused resistors, ion-implanted resistors, thin-film resistors, polysilicon resistors, etc. Heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 can be segmented, for example, divided into sections that can be controlled individually or collectively ( Figure 10 not shown in

[0068] Heat from circuit 1010 can be conducted through package bond pads 1040XX and bond wires ( Figure 10 not shown in

[0069] Although the bonding pads 1040 are shown as being equal in size and equidistant from each other, the bonding pads 1040 may have different sizes, numbers, and spacing from each other. The bonding wires associated with the bonding pads 1040 may also have different lengths. The sizes, numbers, and spacing of the bonding pads 1040 and the bonding wires associated with the bonding pads 1040 can be designed for uniform thermal conductivity to achieve a uniform temperature across the circuit 1010 and the resonator(s) 1020. The sizes, numbers, and placement of the heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 can be adjusted to compensate for the asymmetric heat conduction through the bonding pads 1040 and the bonding wires associated with the bonding pads 1040. In operation, the power supplied to each of the heaters 1030A-1, 1030A-2, 1030B-1, and / or 1030B-2 can be controlled to compensate for the asymmetric heat conduction through the bonding pads 1040 and the bonding wires associated with the bonding pads 1040. For example, the foregoing techniques can produce a thermal gradient of about 1.0E-3 °C or less across the circuit 1010 and / or the resonator(s) 1020, which can be referred to as a highly uniform thermal gradient.

Claims

1. An apparatus, comprising: A heated section, the heated section comprising a first die and a second die, wherein: The first die comprises a heater, and The second die is coupled to the first die and comprises a temperature sensor and a microelectromechanical system (MEMS) resonator; and An unheated section, the unheated section being electrically coupled to the heated section and comprising a third die, wherein: The third die receives a first signal associated with the temperature sensor and provides a second signal to the first die associated with the heater based on the first signal to maintain the heated section at a predetermined temperature.

2. The device according to claim 1, wherein, The first die further comprises a heater driver, the heater driver using the second signal to control the amount of heat generated by the heater.

3. The apparatus according to claim 1, wherein: The first die further comprises a sustaining circuit coupled to the resonator, and The third die receives a third signal associated with the sustaining circuit and generates a periodic signal using temperature compensation.

4. The apparatus according to claim 3, wherein, The third die further comprises a communication port, the communication port receiving configuration information for temperature compensation.

5. The apparatus according to claim 1, wherein At least one of the first die, the second die, and the third die comprises silicon.

6. The device according to claim 1, wherein The temperature sensor comprises at least one of a MEMS resonator, a resistive temperature detector, and a bipolar junction.

7. The apparatus according to claim 1, wherein The heater comprises at least one of a diffused resistor, an ion implanted resistor, a thin film resistor, a polysilicon resistor, and a transistor.

8. The device according to claim 1, wherein, The unheated section has a lower thermal resistance to ambient temperature than the heated section.

9. The apparatus according to claim 1, wherein, The unheated section is thermally separated from the heated section.

10. An apparatus, comprising: A substrate; A first package coupled to the substrate, the first package comprising: A first die, the first die comprising at least one heater, and A second die, the second die coupled to the first die and comprising a temperature sensor and a resonator; A second package coupled to the substrate, the second package comprising: A third die, the third die receiving a first signal associated with the temperature sensor and providing a second signal associated with the at least one heater based on the first signal; and A cover plate, the cover plate being deployed over the substrate, the first package, and the second package.

11. The apparatus according to claim 10, wherein, Each of the first package and the second package is at least one of a ceramic package, a plastic package, and a metal package.

12. The apparatus according to claim 10, wherein, The first package has a higher thermal resistance to ambient temperature than the second package.

13. The apparatus according to claim 10, wherein The first package further comprises an insulator deployed between the first die and a portion of the first package.

14. The apparatus according to claim 13, wherein, The insulator comprises at least one of glass and ceramic.

15. The apparatus according to claim 10, wherein, The substrate is a printed circuit board.

16. The apparatus according to claim 15, wherein, The substrate comprises at least one of aluminum, copper, phenolic paper, woven fiberglass, ceramic, polyimide foil, and polyimide-fluoropolymer composite foil.

17. The apparatus according to claim 10, wherein The cover plate comprises at least one of plastic and metal.

18. The apparatus according to claim 10, wherein: The first die further comprises a sustaining circuit coupled to the resonator, and The third die receives a third signal associated with the sustaining circuit and generates a periodic signal using temperature compensation.

19. An apparatus, comprising: A substrate; A first package coupled to the substrate, the first package comprising: An insulator, the insulator coupled to the first package and a first semiconductor die, The first semiconductor die, comprising at least one heater and a sustaining circuit, and A second semiconductor die, the second semiconductor die being coupled to the first semiconductor die and including a temperature sensor and a microelectromechanical system (MEMS) resonator; and A second package coupled to a substrate, the second package including: A third semiconductor die, Receiving a first signal associated with the temperature sensor and a second signal associated with a sustaining circuit, Providing a third signal to a first die associated with at least one heater based on the first signal, and Generating a fourth signal using temperature compensation based on the second signal.

20. The apparatus according to claim 19, wherein: The dimension of the insulator is less than the dimension of the first die, The first package is hermetically sealed and coupled to a first surface of the substrate, and The second package is coupled to a second surface of the substrate.

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