阅读说明：本技术 一种可调随机振荡器及其应用 (Adjustable random oscillator and application thereof ) 是由 王宗巍 鲍霖 蔡一茂 凌尧天 黄如 于 2021-09-28 设计创作，主要内容包括：本发明公布了一种可调随机振荡器及其应用,该可调随机振荡器由可调电阻与叠层器件串联形成,叠层器件包括金属顶电极,阈值开关材料层,阻变材料层和金属底电极,通过改变可调电阻的阻值以及阻变材料的电阻实现随机性和采样帧间隔的调节。本发明可调随机振荡器适用于压缩感知采样系统,可调随机振荡器输出的周期性电压信号作为传输门和数模转换器的使能信号,当可调随机振荡器的输出电压超过传输门和模数转换器的使能电压后,模数转换器开始采集外界信号；当可调随机振荡器的输出电压低于传输门和模数转换器的使能电压后,采集停止,压缩感知采样系统完成采样帧。本发明实现了低成本、高效率的信息采集,对搭建万物互联的信息网络有着重要意义。(The invention discloses an adjustable random oscillator and application thereof, the adjustable random oscillator is formed by connecting an adjustable resistor and a laminated device in series, the laminated device comprises a metal top electrode, a threshold switch material layer, a resistance change material layer and a metal bottom electrode, and the adjustment of randomness and sampling frame interval is realized by changing the resistance value of the adjustable resistor and the resistance of the resistance change material. The adjustable random oscillator is suitable for a compressive sensing sampling system, a periodic voltage signal output by the adjustable random oscillator is used as an enabling signal of a transmission gate and an analog-to-digital converter, and when the output voltage of the adjustable random oscillator exceeds the enabling voltage of the transmission gate and the analog-to-digital converter, the analog-to-digital converter starts to acquire an external signal; and when the output voltage of the adjustable random oscillator is lower than the enabling voltage of the transmission gate and the analog-to-digital converter, stopping acquisition, and completing a sampling frame by the compressed sensing sampling system. The invention realizes low-cost and high-efficiency information acquisition and has important significance for building information networks of interconnection of everything.)

1. An adjustable random oscillator is characterized by being formed by connecting an adjustable resistor and a laminated device in series, wherein the laminated device comprises a metal top electrode, a threshold switch material layer, a resistance change material layer and a metal bottom electrode, when constant voltage is applied to two ends of a series structure, a voltage source can charge a parasitic capacitor of the laminated device through the adjustable resistor, the voltage of a series node is raised, after the voltage of the node exceeds the threshold voltage of the laminated device, the laminated device is started to discharge a series node, the voltage of the series node is lowered, and the charge-discharge cycle of the series node is completed to form voltage oscillation.

2. The tunable random oscillator of claim 1 wherein the metal top and bottom electrodes are of Ti, TiN, TaN, Ta, Al, AlN, W or Cu conductor material.

3. The tunable random oscillator of claim 1 wherein the resistive switching material layer is composed of a single or multi-layered composite thin film, the composite thin film is a composite of metal tantalum and metal oxide, or the composite thin film is a composite of metal tantalum, metal material and metal oxide, the metal material is Cu, Ti, Ta, W, Pt, TiN or TaN, the metal oxide is TiO_x、TaO_x、WO_x、HfO_x、AlO_xOr ZrO_x。

4. A tunable random oscillator according to claim 3 wherein the composite film is tantalum and tantalum oxides, tantalum and hafnium oxides; or oxides of tantalum and titanium and tantalum, oxides of tantalum and titanium and hafnium, oxides of tantalum and iridium and tantalum, oxides of tantalum and tungsten and tantalum, and oxides of tantalum and iridium and titanium.

5. The tunable random oscillator of claim 1 wherein the layer of threshold switching material is a single layer or multiple layers of VO_x、NbO_xA material.

6. The tunable random oscillator of claim 1 wherein the resistive or threshold switching material layer has a thickness of 5nm to 1000 nm.

7. A compressive sensing sampling system is characterized by comprising an adjustable random oscillator, an analog-to-digital converter and a transmission gate circuit, wherein the adjustable random oscillator is formed by connecting an adjustable resistor and a laminated device in series, the laminated device comprises a metal top electrode, a threshold switch material layer, a resistance change material layer and a metal bottom electrode, a periodic voltage signal output by the adjustable random oscillator is used as an enabling signal of the transmission gate and the analog-to-digital converter, and when the output voltage of the adjustable random oscillator exceeds the enabling voltage of the transmission gate and the analog-to-digital converter, the analog-to-digital converter starts to acquire an external signal; and when the output voltage of the adjustable random oscillator is lower than the enabling voltages of the transmission gate and the analog-to-digital converter, the acquisition of the analog-to-digital converter is stopped, and the compressed sensing sampling system completes a single sampling frame.

8. The compressed sensing sampling system of claim 7, wherein adjusting the resistance of the adjustable resistor changes the length of the sampling frame, thereby changing the number of sampling points.

9. The compressive sensing sampling system of claim 7, wherein adjusting the resistance of the resistive-switching material layer changes a threshold voltage of the stacked device, thereby changing a sampling frame length.

Technical Field

The invention belongs to the technical field of semiconductor (semiconductor), compressed sensing (compressed sensing) and Complementary Metal Oxide Semiconductor (CMOS) hybrid integrated circuits, and particularly relates to an adjustable random oscillator suitable for compressed sensing sampling.

Background

With the development of digital information processing technology, the world has entered the big data era today. The digital life makes new requirements on the resolution and accuracy of information perceived by an information processing system. Early work has demonstrated that continuous-time limited bandwidth signals can be obtained via discrete sampling under the nyquist theorem. However, the large amount of data generated by the development of emerging applications still easily depletes the computing power of the sampling system, which is a problem that is even more pronounced when the sampling system is deployed on edge devices.

As a novel information sensing technology, the compressed sensing technology can reduce the sampling rate of sparse signals, and the sampling and compression of the signals are completed simultaneously. One important difference between the compressive sensing technique and the conventional sampling technique is its requirement for randomly spaced sampling points. Typically, the compressive sensing system uses CMOS circuit blocks to generate random sparse sampling clocks to accomplish the non-equidistant sampling. Much research is currently focused on implementing high performance sensors and computing units with new devices, but there is less interest in sampling control modules. The control module capable of generating the adjustable random trigger signal often has a complex structure, so that not only is the miniaturization of the sampling device limited, but also an additional power consumption problem is brought. The non-ideal effect of the novel device is utilized to generate random and sparse sampling clock signals, so that the integration density and the energy use efficiency of the compressive sensing system can be obviously improved.

The threshold switching and resistive switching characteristics of transition metal oxides have found application in many areas. For example, the application of memristors leads the development of brain-like computation, and threshold switching devices based on insulator-metal transition can be used as gate tubes to be applied to resistive random access memory arrays. As processing technology has advanced, the non-ideal effects of the devices have been greatly mitigated. However, due to the inherent randomness of the material (e.g., random variation of the grain boundaries and the location of the conductive vias), the random fluctuations in device characteristics are not completely eliminated. Typically, random fluctuations in these switching parameters degrade device performance and even destroy system functionality. However, effectively controlling these randomness makes it possible to implement a structurally simple random number generator to generate a randomly sampled signal, thereby achieving an energy-efficient, miniaturized compressive sensing sampling system.

Disclosure of Invention

In order to solve the problems of overlarge area and overlarge power consumption of a random clock generator in the conventional compressive sensing sampling circuit, the invention provides an adjustable random oscillator based on a threshold switch material/resistive material laminated device and a compressive sensing sampling system based on the adjustable random oscillator. The voltage oscillation signal of the adjustable random oscillator is used as an enabling signal of the sampling circuit, and randomness and sampling frame interval adjustment are achieved by changing the resistance value of the adjustable resistor and the resistance of the resistance change material, so that the unequal interval sampling compression sensing system is achieved. The data sampled by the compressed sensing system can be restored to the original signal by an Orthogonal Matching Pursuit (OMP) algorithm.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

an adjustable random oscillator is characterized by being formed by connecting an adjustable resistor in series with a laminated device, wherein the laminated device comprises a metal top electrode, a threshold switch material layer, a resistance change material layer and a metal bottom electrode, as shown in figure 1. The randomness and the sampling frame interval are adjusted by changing the resistance value of the adjustable resistor and the resistance of the resistance change material. When constant voltage is applied to two ends of the series structure, a voltage source charges a parasitic capacitor of the laminated device through the adjustable resistor, the voltage of the series node rises, after the node voltage exceeds the threshold voltage of the laminated device, the laminated device is started to discharge to the series node, the voltage of the series node falls, the charge-discharge cycle of the series node forms voltage oscillation, and the RC relaxation time of charging and discharging the capacitor can be changed by adjusting the resistance value of the adjustable resistor, so that the voltage oscillation period of the series node is changed. Changing the resistance of the resistive layer of the stacked device changes the threshold voltage of the device and thus changes the charge-discharge time, thus changing the voltage oscillation period of the series node in this way.

Preferably, the metal top and bottom electrode materials are conductor materials, including Ti, TiN, TaN, Ta, Al, AlN, W, Cu, etc.;

preferably, the resistive switching material layer is composed of a single-layer or multi-layer composite material film, comprises a composite material of metal tantalum and metal oxide, and comprises tantalum and tantalum oxide (Ta/TaO)_x) Tantalum and hafnium oxides (Ta/HfO)_x) Or a composite of metallic tantalum, other metals and metal oxides, including tantalum and oxides of titanium and tantalum (Ta/Ti/TaO)_x) Tantalum and titanium and hafnium oxides (Ta/Ti/HfO)_x) Tantalum and oxides of iridium and tantalum (Ta/Ir/TaOx), tantalum and oxides of tungsten and tantalum (Ta/W/TaO)_x) Oxides of tantalum and iridium and titanium (Ta/Ir/TiO)_x) The metal oxide terminal of the above composite material of metal tantalum and metal oxide may be a variety of metal materials including Cu, Ti, Ta, W, Pt, TiN, TaN, TiO_x、TaO_x、WO_x、HfO_x、AlO_x、ZrO_xAnd forming a metal/N layer transition metal oxide/metal structure, wherein N is more than or equal to 1.

Preferably, the threshold switch material layer is composed of a single-layer or multi-layer composite material film and comprises VO_x、NbO_xAnd the like.

Preferably, the resistive switching material layer and the threshold switching material layer have thicknesses of 5nm to 1000nm respectively.

A compressed sensing sampling system based on an adjustable random oscillator comprises the adjustable random oscillator, an analog-to-digital converter (A/Dconverter) and a transmission gate circuit, wherein a periodic voltage signal output by the adjustable random oscillator is used as an enabling signal of the transmission gate and the digital-to-analog converter, and when the output voltage of the adjustable random oscillator exceeds the enabling voltage of the transmission gate and the analog-to-digital converter, the analog-to-digital converter starts to acquire an external signal; and when the output voltage of the adjustable random oscillator is lower than the enabling voltage of the transmission gate and the analog-to-digital converter, stopping acquisition, and thus completing a sampling frame by the compressed sensing sampling system.

The randomness of the oscillation period of the adjustable random oscillator comes from the change of the conductive path in the resistance change material layer in different periods, and factors such as the electronic filling state of defects around the conductive path can affect the resistance of the resistance change material layer, further affect the RC relaxation time of capacitor charging, and finally cause the randomness of the oscillation period. The compressed sensing sampling system based on the adjustable random oscillator controls the length of a sampling frame to realize non-equidistant sampling by the adjustable random oscillator, and the acquired data can be recovered by an orthogonal matching tracking method to be subjected to subsequent analysis and processing. Compared with other pseudo-random clock generators based on CMOS circuits, the adjustable random oscillator has great advantages in power consumption and area, is favorable for being integrated in edge-end sampling equipment, realizes low-cost and high-efficiency information acquisition, and has important significance for building information networks of interconnection of everything.

Drawings

FIG. 1 is a schematic diagram of a stacked device structure according to the present invention;

FIG. 2 is a schematic diagram of a stacked device in an embodiment of the present invention, wherein (a) is a schematic structural diagram; (b) is a schematic diagram of direct current electrical characteristics;

FIG. 3 is a schematic structural diagram of a compressive sensing sampling system based on a tunable random oscillator according to an embodiment of the present invention;

FIG. 4 is a diagram illustrating the load resistance control of the tunable random oscillator according to an embodiment of the present invention, wherein (a) is the load resistance R₁A voltage waveform diagram of (a); (b) is a load resistance R₁A voltage waveform schematic of +10K Ω; (c) the diagram is a diagram for regulating the number of output pulses by utilizing the load conductance;

FIG. 5 is a diagram illustrating the definition of sampling frames and sampling times for an adjustable random oscillator according to an embodiment of the present invention;

fig. 6 is a schematic diagram of the effect of the conductance of the resistive switching material layer on the threshold voltage of the device in an embodiment of the present invention;

FIG. 7 is a graph showing the variation of threshold voltage of a stacked device in an embodiment of the present invention, wherein (a) is a graph showing the effect of the threshold voltage of the device on the number of pulses output from an oscillator; (b) the effect of the resistance of the resistive material layer on the number of output pulses of the oscillator is shown schematically.

Detailed Description

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below.

The invention adopts a resistance change material/threshold value transition material laminated device to form an adjustable random oscillator control sampling circuit to realize non-equal interval sampling, which comprises the following specific steps:

the threshold switch material/resistive material laminated device comprises a metal top electrode, a threshold switch material dielectric layer, a resistive material dielectric layer and a metal bottom electrode. The preparation method comprises the following steps:

1) forming a metal bottom electrode material by using a Physical Vapor Deposition (PVD) method;

2) patterning the metal bottom electrode by photoetching and etching;

3) forming a threshold switching material layer using an Atomic Layer Deposition (ALD) method;

4) forming a resistance change material layer by using a Physical Vapor Deposition (PVD) method;

5) annealing to crystallize the threshold switching material;

6) the metal top electrode material is formed using a Physical Vapor Deposition (PVD) process.

Wherein the top electrode is TiN, the bottom electrode is Pt, and the resistive material layer and the threshold transition material layer are respectively TaO_xAnd VO₂The structure and the direct current electrical characteristics of the stacked device of (1) are shown in fig. 2; the adjustable resistor is connected with the laminated device in series to form an adjustable random oscillator.

The compressed sensing sampling system based on the adjustable random oscillator mainly comprises the adjustable random oscillator, a transmission gate and an analog-to-digital converter, and is shown in figure 3. The output end of the adjustable random oscillator is A, and the voltage V of the output end A_AExhibits periodic oscillation as an enable signal for the transmission gate and the analog-to-digital converter. When V is_AMore than two causeWhen the voltage is available, the transmission gate is opened, and the analog-to-digital converter performs sampling. When V is_AWhen the voltage is less than the enabling voltage of the transmission gate and the transmission gate, the analog-to-digital converter stops sampling, and a sampling frame is ended. The number of voltage pulses at the output node of the adjustable random oscillator is controlled by the load resistance, and the voltage waveform and the output pulse statistics are shown in fig. 4; the sampling frame is defined as a period of voltage oscillation of the output end of the adjustable random oscillator, wherein the sampling time delta T is the time when the transmission gate is opened and the analog-to-digital converter collects an external signal. By adjusting the resistance value of the adjustable resistor, the length of the sampling frame (the length of the sampling time) can be adjusted, thereby changing the number of sampling points. The definition of the sampling frame and the sampling time is shown in fig. 5; the resistance of the resistive material layer can be adjusted electrically, so that the threshold voltage of the laminated device can be adjusted, and the change relationship is shown in fig. 6; the variation of the threshold voltage of the stacked device will affect the oscillation state of the tunable random oscillator, so as to change the length of the sampling frame and implement the reconfiguration of the sampling mode, as shown in fig. 7. Within a single sampling frame, the time interval between sampling points is determined by the analog-to-digital converter and is a fixed value. The length of the sampling frame is random (the sampling time within each sampling frame is also random) due to the randomness of the period of the output signal of the tunable random oscillator. The compressed sensing sampling system based on the adjustable random oscillator realizes non-equidistant sampling by introducing sampling frames with random lengths; the number of sampling points is controlled by controlling the time of sampling frames.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.