Analog memory and computing device based on phase change material micro-electro-mechanical system
By using PCM variable MEMS capacitors in computing devices, the capacitor gap is adjusted by using temperature changes, the problems of calculation delay, high energy consumption and low bit resolution in the prior art are solved, and high performance and low energy consumption are realized. .
Patent Information
- Application Number
- CN202410860193.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-08-02
- Filing Date
- 2024-06-28
- Publication Date
- 2025-02-14
AI Technical Summary
Existing computing devices have problems such as computational delay, high energy consumption and low bit resolution in brain-like computing and large machine learning applications.
Using a phase change material (PCM) variable microelectromechanical system (MEMS) capacitor, the temperature of the PCM is changed in the PCM chamber through a heater, thereby adjusting the capacitor gap and achieving a single multiplication operation.
Reduces computational delay, improves bit resolution, and reduces energy consumption, enabling high-performance computing devices.
Smart Images
Figure CN119451133A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates generally to memory and computing devices, and more particularly to analog memory and computing devices based on phase change material (PCM) microelectromechanical systems (MEMS) devices. Background Art
[0002] Current processor architectures include memory that is separate from the processor core. This architecture is traditionally known as the von Neumann computing architecture. In this architecture, the data rate of information transfer from memory to the computing core creates a bottleneck in processing speed. This in turn makes this architecture unsuitable for brain-like computing (e.g., artificial intelligence (AI)) and large machine learning (ML) applications that rely on accurate, predictive, and high-performance computing solutions. Examples of these applications include advanced materials discovery, chemical synthesis, radiation electrodynamics, fluid dynamics, energy or mass transport through heterogeneous media, semiconductor device design and manufacturing, and earth system models.
[0003] There are two main challenges with existing techniques. The first challenge is related to computational latency. Specifically, the cost of multiply-and-accumulate (MAC) operations, which are the building blocks of large-scale modeling and computation, increases with the number of parameters and the size of the problem (e.g., O(N)). 2 The second challenge is related to energy and bit resolution. Specifically, current memory and computing methods use electronic circuit elements that consume relatively high power due to standby leakage current and have inherently large electronic noise, which can reduce bit resolution.
[0004] Therefore, there is a need for a computing device that does not exhibit the computational latency or energy and bit resolution issues of currently known devices. The present disclosure addresses at least this need. Summary of the invention
[0005] This Summary is provided to describe selected concepts in a simplified form that are further described in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0006] In one embodiment, a computing device includes a phase change material (PCM) variable microelectromechanical system (MEMS) capacitor and a power supply. The PCM variable MEMS capacitor includes a substrate, a first electrode, a second electrode, a PCM, and a heater. The first electrode is coupled to the substrate and has a first electrode inner surface and a first electrode outer surface. The first electrode inner surface is spaced apart from the substrate to define a PCM chamber between the first electrode inner surface and the substrate. The second electrode is coupled to the substrate and has a second electrode inner surface and a second electrode outer surface. The second electrode inner surface is spaced apart from the first electrode outer surface to define a capacitive gap between the inner electrode and the outer electrode. The PCM is disposed in the PCM chamber. The heater element is disposed in the PCM chamber and is coupled to receive a voltage pulse, whereby the temperature of the PCM changes, thereby changing the capacitive gap. The power supply is coupled to the PCM variable MEMS capacitor and is operable to (i) supply a voltage pulse to the heater, and (ii) supply a time-dependent voltage between the first electrode and the second electrode, thereby achieving a single multiplication operation.
[0007] In another embodiment, a computing device includes a plurality of phase change material (PCM) variable microelectromechanical system (MEMS) capacitors, a power supply, and a circuit. The PCM variable MEMS capacitors are electrically connected in a crossbar array configuration and each include a substrate, a first electrode, a second electrode, a PCM, and a heater. Each first electrode is coupled to the substrate and has a first electrode inner surface and a first electrode outer surface. The first electrode inner surface is spaced apart from the substrate to define a PCM chamber between the first electrode inner surface and the substrate. Each second electrode is coupled to the substrate and has a second electrode inner surface and a second electrode outer surface. The second electrode inner surface is spaced apart from the first electrode outer surface to define a capacitive gap between the inner electrode and the outer electrode. The PCM is disposed in the PCM chamber. Each heater element is disposed in the PCM chamber and is coupled to receive a voltage pulse, whereby the temperature of the PCM changes, thereby changing the capacitive gap. The power supply is coupled to each PCM variable MEMS capacitor and is operable to (i) supply a voltage pulse to each heater, and (ii) supply a time-dependent voltage between each of the first electrodes and each of the second electrodes, thereby implementing a single multiplication operation through each PCM variable MEMS capacitor. The circuit is coupled to each PCM variable MEMS capacitor and is configured to add together each single multiplication operation performed by each PCM variable MEMS capacitor.
[0008] In yet another embodiment, an analog memory device includes a phase change material (PCM) variable microelectromechanical system (MEMS) capacitor and a voltage source. The PCM variable MEMS capacitor includes a substrate, a first electrode, a second electrode, a PCM, and a heater. The first electrode is coupled to the substrate and has a first electrode inner surface and a first electrode outer surface. The first electrode inner surface is spaced apart from the substrate to define a PCM chamber between the first electrode inner surface and the substrate. The second electrode is coupled to the substrate and has a second electrode inner surface and a second electrode outer surface. The second electrode inner surface is spaced apart from the first electrode outer surface to define a capacitive gap between the inner electrode and the outer electrode. The PCM is disposed in the PCM chamber. The heater element is disposed in the PCM chamber and is coupled to receive a voltage pulse, whereby the temperature of the PCM changes, thereby changing the capacitive gap. The voltage source is coupled to the heater element and is configured to supply a voltage pulse having an amplitude and duration that ensures that the second electrode inner surface remains spaced apart from the first electrode outer surface.
[0009] Furthermore, other desirable features and characteristics of the computing device and the analog memory device will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing background. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present disclosure will now be described in conjunction with the following drawings, wherein like numerals represent like elements, and wherein:
[0011] Figure 1 and Figure 2 depicts a simplified cross-sectional view of one embodiment of a single analog memory device;
[0012] Figure 3 Depicted include Figure 1 A functional block diagram of one embodiment of a computing device emulating a memory device as depicted in;
[0013] Figure 4 Describes multiple Figure 1 A functional block diagram of one embodiment of a computing device emulating a memory device as depicted in FIG. 1 ; and
[0014] Figure 5 Depicted is a simplified representation of multiple analog memory devices connected in a crossbar array configuration. DETAILED DESCRIPTION
[0015] The following specific embodiments are merely exemplary in nature and are not intended to limit the invention or the application and use of the invention. As used herein, the word "exemplary" means "used as an example, instance or illustration". Therefore, any embodiment described herein as "exemplary" is not necessarily to be understood as being preferred or advantageous over other embodiments. All embodiments described herein are exemplary embodiments provided to enable those skilled in the art to make or use the invention, without limiting the scope of the invention as defined by the claims. In addition, it is not intended to be bound by any express or implied theory presented in the aforementioned technical field, background technology, summary of the invention or the following specific embodiments.
[0016] First reference Figure 1 , depicts a simplified cross-sectional view of one embodiment of an analog memory device. The analog memory device 100 includes a phase change material (PCM) variable micro-electromechanical system (MEMS) capacitor 102 and a voltage source 104. The PCM variable MEMS capacitor 102 includes a substrate 106, a first electrode 108, a second electrode 112, a PCM 114, and a heater element 116. It will be appreciated that the substrate 106 can be formed of any of a variety of known electrical insulators or semiconductor materials. In an exemplary embodiment, the substrate 106 is formed of silicon.
[0017] The first electrode 108 and the second electrode 112 are both coupled to the substrate 106. The first electrode has a first electrode inner surface 118 and a first electrode outer surface 122, and the second electrode 112 has a second electrode inner surface 124 and a second electrode outer surface 126. The first electrode inner surface 118 is spaced apart from the substrate 106 to define a PCM chamber 128 between the first electrode inner surface 118 and the substrate 106. The second electrode inner surface 124 is spaced apart from the first electrode outer surface 122 to define a capacitive gap 132 between the inner electrode 108 and the outer electrode 112. It will be appreciated that the first electrode 108 and the second electrode 112 can be formed using any of a variety of known conductive materials. In an exemplary embodiment, the first electrode and the second electrode each include platinum and platinum.
[0018] The PCM 114 is disposed within the PCM chamber 128. As is well known, the PCM 114 is a material that can be reversibly and rapidly switched between a crystalline phase and an amorphous phase. It is also well known that various physical properties of the PCM change when the PCM switches between the crystalline phase and the amorphous phase. One of these physical properties is density, and as will be described later, is a property change that is used to change the capacitive gap 132. It will be appreciated that the PCM 114 can be implemented using any of a variety of known PCMs. In one exemplary embodiment, the PCM 114 is implemented using germanium telluride.
[0019] By controllably changing its temperature, the PCM 114 can be controllably switched between its crystalline and amorphous phases. In fact, this is the purpose of the heater element 116. The heater element 116 is disposed within the PCM chamber 128 and is coupled to receive a voltage pulse. The voltage pulse causes a change in the temperature of the heater element 116, which in turn changes the temperature of the PCM 114. This change in the temperature of the PCM 114 changes the density of the PCM 114. Figure 1 and Figure 2 As depicted, varying the density of PCM 114 varies the capacitive gap 132. It will be appreciated that the heater element 116 may comprise any of a variety of known materials. In one exemplary embodiment, the heater element 116 comprises tungsten.
[0020] Before we go any further, it can be seen that at least Figure 1 and Figure 2 In the depicted embodiment, the PCM variable MEMS 102 also includes an isolation layer 134. When the isolation layer 134 is included, the isolation layer is formed on a surface 136 of the substrate 106 and is disposed between the substrate 106 and each of the first electrode 108, the second electrode 112, the PCM 114, and the heater element 116. It will be appreciated that the isolation layer 134 may include any of a variety of known materials. In an exemplary embodiment, the isolation layer 134 includes silicon nitride.
[0021] Voltage pulses are supplied from the voltage source 104 to the heater element 116. Thus, Figure 1 and Figure 2 As depicted, a voltage source 104, which may be implemented on the same substrate 102 as the PCM variable MEMS 102, is coupled to a heater element 116. It will be appreciated that the amplitude and duration of the voltage pulse supplied to the heater element 116 may (and typically will) vary. In fact, as will now be explained, the capacitive gap 132 between the first electrode 108 and the second electrode 112 may be modulated using a particular voltage pulse profile. However, it should be noted that the voltage pulse supplied to the heater element 116 will always have an amplitude and duration that ensures that the capacitive gap 132 always exists; that is, the second electrode inner surface 124 remains spaced apart from the first electrode outer surface 122.
[0022] As described above, the capacitive gap 132 is set using a voltage pulse according to the following relationship:
[0023]
[0024] Wherein, ∈ is the dielectric constant, A is the capacitor area, g is the initial gap in the crystalline phase, and y is the effective change in the capacitive gap 132 due to the volume expansion of the PCM 114 in response to the input voltage profile pulse.
[0025] The effective variation of the capacitance gap 132(y) is set as follows:
[0026] y=SF*V PCM
[0027] Among them, V PCM is the pulse applied to the PCM 114, and SF is the scaling factor relating the voltage and input Joule heating to the PCM displacement. As can be appreciated, the scaling factor varies with the choice of PCM 114.
[0028] Figure 1 and Figure 2 The PCM variable MEMS capacitor 102 depicted in FIG. 1 may also be used to implement a computing device such as Figure 3 . As depicted therein, in addition to the PCM variable MEMS capacitor 102, the computing device 300 also includes a power supply 302. As described above, the power supply 302 is coupled to the PCM variable MEMS capacitor 102 and is operable to supply voltage pulses to the heater element 116. In addition, the power supply 302 is also configured to supply a time-dependent voltage between the first electrode 108 and the second electrode 112, thereby achieving a single multiplication operation. As can be appreciated, the time-dependent voltage supplied by the power supply 302 can vary, but it is preferably a sinusoidal voltage (i.e., Vsin(ωt)) or a ramp voltage (i.e., V*ramp).
[0029] More specifically, when the power supply 302 supplies a time-dependent voltage between the first electrode 108 and the second electrode 112, the depicted computing device 300 computes the capacitive current (I) for the set capacitive gap 132 (i.e., gy) as follows:
[0030]
[0031] Therefore, when the time-dependent voltage is a ramp:
[0032]
[0033] The output current (I) has a DC offset, which can be filtered out, and a multiplication term, which is a single multiplication operation.
[0034] Now go to Figure 4, it can be seen that the computing device 400 can also be implemented using multiple PCM variable MEMS capacitors 102. It will be appreciated that for clarity and ease of depiction, only nine PCM variable MEMS capacitors 102 are shown. In other embodiments, the computing device 400 may include more or less than this number. The computing device 400 also includes the power supply 302 described previously, and also includes a circuit 402. The circuit 402 can also be implemented on the same substrate 102 as the PCM variable MEMS 102, and its purpose will be described later, the circuit is preferably implemented as a summing circuit, such as an operational amplifier with high resistance feedback.
[0035] Preferably, the PCM variable MEMS capacitors 102 are electrically connected in a crossbar array configuration. Figure 5 As depicted, the crossbar array configuration includes a plurality of parallel word lines 504 and a plurality of parallel bit lines 506, which are arranged perpendicular to each other. In the depicted embodiment, each word line 504 is electrically coupled to the second electrode 112 of a predetermined number of PCM variable MEMS capacitors 102, and each bit line 506 is electrically coupled to the first electrode 108 of a predetermined number of PCM variable MEMS capacitors 102.
[0036] With this configuration, the output current (i.e., a single multiplication operation) from each PCM variable MEMS capacitor 102 is supplied to a circuit 402 that is configured to add together each single multiplication operation implemented by each PCM variable MEMS capacitor 102 as follows:
[0037]
[0038] The device described in this article can be used to implement high performance, large bit resolution, in-memory computing cores and MAC operators. pcm and V in The multiplication of the array of PCM variable MEMS capacitors 102 as input can produce a multiply and accumulate (MAC) operation in constant time, where C1 is a constant. In other words, it is O(N) compared to known devices. 2 ), the MAC operation can be performed with a scaling factor of O(1). The PCM variable MEMS capacitor 102 employs capacitive current based readout with an air gap, which eliminates leakage current and makes the architecture highly immune to noise, thereby improving bit resolution.
[0039] It will be understood by those skilled in the art that the various exemplary logic blocks, modules, circuits and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software or a combination of the two. Some embodiments and specific implementations are described above according to functions and / or logic block components (or modules) and various processing steps. However, it should be understood that such block components (or modules) can be implemented by any number of hardware, software and / or firmware components configured to perform a specified function. In order to clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits and steps have been described above in general according to their functions. Whether such functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the entire system. The technician can implement the described functions in different ways for each specific application, but such specific implementation decisions should not be interpreted as causing deviations from the scope of the present invention. For example, the embodiments of the system or components can use various integrated circuit components, such as memory elements, digital signal processing elements, logic elements, lookup tables, etc., which can perform multiple functions under the control of one or more microprocessors or other control devices. In addition, it will be understood by those skilled in the art that the embodiments described herein are only exemplary specific implementations.
[0040] In this document, relational terms such as first and second, etc., may be used only to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Unless explicitly defined by the claim language, numerical ordinals such as "first", "second", "third", etc., only represent different individuals in a plurality, and do not imply any order or sequence. Unless explicitly defined by the claim language, the sequence of text in any claim does not imply that the processing steps must be performed in a temporal or logical order according to such sequence. Without departing from the scope of the present invention, the method steps may be interchanged in any order, as long as such interchange does not contradict the claim language and is not logically absurd.
[0041] In addition, depending on the context, words such as "connected" or "coupled to" used when describing the relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other way through one or more additional elements.
[0042] Although at least one exemplary embodiment has been presented in the aforementioned specific embodiments of the present invention, it should be understood that there are a large number of variations. It should also be understood that an exemplary embodiment or multiple exemplary embodiments are only examples and are not intended to limit the scope, applicability or construction of the present invention in any way. On the contrary, the aforementioned specific embodiments will provide a convenient roadmap for implementing the exemplary embodiments of the present invention for those skilled in the art. It should be understood that, without departing from the scope of the present invention as set forth in the appended claims, various changes may be made to the functions and arrangements of the elements described in the exemplary embodiments.
Claims
1. A computing device, comprising: A phase change material (PCM) variable micro-electromechanical system (MEMS) capacitor, the PCM variable MEMS capacitor comprising: (i) substrate; (ii) a first electrode coupled to the substrate and having a first electrode inner surface and a first electrode outer surface, the first electrode inner surface being spaced apart from the substrate to define a PCM chamber between the first electrode inner surface and the substrate; (iii) a second electrode coupled to the substrate and having a second electrode inner surface and a second electrode outer surface, the second electrode inner surface being spaced apart from the first electrode outer surface to define a capacitive gap between the inner electrode and the outer electrode; (iv) a PCM disposed within the PCM chamber; and (v) a heater element disposed within the PCM chamber and coupled to receive a voltage pulse whereby a temperature of the PCM is varied, thereby changing the capacitive gap; and A power supply is coupled to the PCM variable MEMS capacitor and is operable to (i) supply the voltage pulse to the heater and (ii) supply a time-dependent voltage between the first electrode and the second electrode to implement a single multiplication operation. 2 . The computing device of claim 1 , wherein the time-dependent voltage is a sinusoidal voltage. The computing device of claim 1 , wherein the time-dependent voltage is a ramped voltage.
4. The computing device of claim 1 , wherein the PCM variable MEMS further comprises an isolation layer formed on a surface of the substrate and disposed between the substrate and each of the first electrode, the second electrode, the PCM, and the heater element. The computing device of claim 4 , wherein the isolation layer comprises silicon nitride or aluminum nitride.
6. The computing device of claim 1, wherein the substrate comprises silicon or silicon carbide. The computing device of claim 1 , wherein the heater comprises tungsten.
8. The computing device of claim 1, wherein the PCM comprises germanium telluride.
9. The computing device of claim 1, wherein the first electrode and the second electrode each comprise platinum and platinum.
10. An emulated memory device, the emulated memory device comprising: A phase change material (PCM) variable micro-electromechanical system (MEMS) capacitor, the PCM variable MEMS capacitor comprising: (i) substrate; (ii) a first electrode coupled to the substrate and having a first electrode inner surface and a first electrode outer surface, the first electrode inner surface being spaced apart from the substrate to define a PCM chamber between the first electrode inner surface and the substrate; (iii) a second electrode coupled to the substrate and having a second electrode inner surface and a second electrode outer surface, the second electrode inner surface being spaced apart from the first electrode outer surface to define a capacitive gap between the inner electrode and the outer electrode; (iv) a PCM disposed within the PCM chamber; and (v) a heater element disposed within the PCM chamber and coupled to receive a voltage pulse whereby a temperature of the PCM is varied, thereby changing the capacitive gap; and A voltage source is coupled to the heater element and is configured to supply the voltage pulse having a magnitude and duration to ensure that the second electrode inner surface remains spaced apart from the first electrode outer surface.