WO2021256197A1

WO2021256197A1 - Information processing device and method for driving information processing device

Info

Publication number: WO2021256197A1
Application number: PCT/JP2021/019882
Authority: WO
Inventors: 広幸秋永; 久島; 泰久内藤
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2020-06-19
Filing date: 2021-05-25
Publication date: 2021-12-23
Also published as: JPWO2021256197A1; TWI775496B; JP7398841B2; TW202201288A

Abstract

This brain-type information processing device has an analog resistance changing element composed of a pair of electrodes and an oxide layer provided between the pair of electrodes, and a drive circuit that superimposes and supplies voltage fluctuations that have fluctuation components on/to drive signals of the analog resistance changing element. By superimposing voltage fluctuations that cause current fluctuations in the drive signals, it is possible to minimize irregular resistance changes in a resistance-lowering (SET) process and in a resistance-raising (RESET) process during the driving of the analog resistance changing element. Due to the minimizing of the irregular resistance change characteristic, noise of the resistance change component can be removed, the resistance change becomes smooth, the power consumption of the brain-type information processing device can be reduced, and the speed of the device can be increased.

Description

Information processing device and driving method of information processing device

The present invention relates to an information processing apparatus and a method for driving the information processing apparatus. In particular, the present invention relates to a brain-type information processing apparatus using an analog resistance changing element and a method for driving the brain-type information processing apparatus.

IoT (Internet of Things) technology has been applied to various fields, and the amount of data flowing into the Internet is increasing at an accelerating rate. This significantly increases the power consumed in all processes such as information collection and storage, analysis, and communication.

When the CPU (Central Processing Unit) accesses the memory and performs arithmetic processing each time as in a conventional computer, the data transfer becomes rate-determining and the increase in power consumption cannot be suppressed. In recent neurocomputers (brain-type information processing devices, brain-type circuits), for example, in-memory computing in which a processor and memory are integrated is used to imitate information processing in the brain, resulting in high calculation efficiency. Power consumption can be reduced.

In brain-type information processing, for example, a nerve cell is modeled as a multi-input 1-output element, and an input pattern is learned or inferred by a perceptron. In the brain-type information processing apparatus, for example, an analog resistance changing element is used for the perceptron, and an array structure in which crossbars are connected by word lines and bit lines is used for the product-sum operation. The analog resistance changing element is also called a memristor or RAND (Resistive Analog Neuro Device).

The analog resistance changing element has a resistance switch effect in which the current value changes non-linearly when a voltage is applied to the insulating oxide film, and the resistance value changes in an analog manner due to the redox reaction induced by the current. The process of lowering the resistance (SET) and the process of increasing the resistance (RESET) of the analog resistance changing element can be brought about by applying a drive pulse of a predetermined voltage.

In order to reduce the power consumption of the brain-type information processing system, it is required to reduce the power required for pulse application and to reduce the number of corrections in the process of reflecting the learning result by flattening the analog resistance change. Here, flattening means that an event that high resistance occurs when a pulse is applied in the low resistance process or low resistance occurs when a pulse is applied in the high resistance process does not occur. In general, it may be included in a technique for reducing noise or increasing resistance to noise.

Currently, no effective technique for flattening, that is, smoothing the resistance change of the analog resistance changing element is disclosed. Therefore, although not directly related to the present invention, a technique for ensuring data reliability by strengthening resistance to fluctuations in input signals and power output in electronic devices and information processing devices or noise will be mentioned.

For example, by writing the same data to different memory cells assigned to two pages with consecutive addresses for non-volatile memory, the coupling noise generated between adjacent memory cells and this coupling noise are used. A technique for suppressing fluctuations in the threshold voltage is disclosed (see, for example, Patent Document 1 below).

In addition, a technology that improves the reliability of data without increasing the cell area by writing the same data to non-volatile memory cells and volatile memory cells with different immunity to external noise and judging the integrity of the data. Is disclosed (see, for example, Patent Document 2 below).

Further, in a memory cell array provided with memory cells at the intersection of wiring, when the memory cells include two cell units connected in columns and both cell units of the column cells are not in the second state, the first value is set. The stored state, the state in which the second value is stored when only one cell unit of the column cell is in the second state, and the third value when both cell units of the column cell are in the second state. Disclosed is a technique having non-volatility with good retention characteristics by setting a voltage that does not cause a disturbance that causes a state transition in a column cell so as to be in a memorized state (see, for example, Patent Document 3 below).

Japanese Unexamined Patent Publication No. 2008-234714 Japanese Unexamined Patent Publication No. 2009-217875 Japanese Unexamined Patent Publication No. 1113-161486

As disclosed in Patent Documents 1 to 3, etc., the prior art only suppresses the generation of external noise and disturbance. Even if these conventional techniques for external noise countermeasures are simply applied to a brain-type information processing system, it is not possible to reduce the power required for pulse application and flatten the change in analog resistance.

In an analog resistance changing element used in a brain-type information processing apparatus, a means for performing a low resistance (SET) process and a high resistance (RESET) process with higher power saving and further smoothing the resistance change is desired. There is. If these can be realized, for example, low power consumption and high speed of the product-sum circuit, which is a basic component of brain-type information processing, can be expected.

In order to solve the above problems, it is an object of the present invention to obtain an information processing apparatus and a driving method of an information processing apparatus capable of suppressing power consumption reduction and resistance change flattening of an analog resistance changing element with a simple configuration. do.

In order to solve the above problems, the information processing apparatus of the present invention comprises an analog resistance changing element composed of a pair of electrodes and an oxide layer provided between the pair of electrodes, and driving the analog resistance changing element. It is characterized by being provided with a drive circuit that superimposes and supplies voltage fluctuations having a fluctuation component on a signal.

Further, the drive circuit is characterized in that it generates a voltage fluctuation that causes a sufficiently small current fluctuation as compared with the current change of the element caused by the drive pulse of a predetermined voltage required for the analog resistance change.

Further, the drive pulse is a constant voltage of about several V, and the fluctuation is a voltage of about 1/10 of the drive pulse.

Further, the drive pulse is more preferably characterized in that the voltage fluctuation is about 1/10 of the drive pulse of about 0.3 V to 5 V used in the electronic device for IoT.

Further, the drive pulse has a voltage of about several V, and the voltage is variable from the initial voltage to the end voltage at a predetermined step voltage, and the voltage fluctuation is about 1/1000 of the drive pulse. do.

Further, the voltage fluctuation is characterized by being any of white noise, Gaussian noise, which is easily generated by an electronic circuit, a sine wave, a triangular wave, and a square wave. Further, this does not apply as long as it gives fluctuations to the drive pulse of the voltage that drives the resistance change. Further, it is desirable that the frequency of the voltage fluctuation has a time determined as the reciprocal thereof equal to or less than the drive pulse width.

Further, the analog resistance changing element is connected to a selection transistor in memory cell units, and the drive circuit supplies the selection transistor with the drive signal superimposed with the voltage fluctuation.

Further, the analog resistance changing element is arranged at a plurality of cross points where the word line and the bit line intersect, and the analog resistance changing element is driven and selected by the word line decoder and the bit line decoder, and the drive circuit is the drive circuit. It is characterized in that the drive signal in which the voltage fluctuation is superimposed is supplied to either the word line decoder or the bit line decoder.

Further, in the driving method of the information processing apparatus of the present invention, a voltage having a fluctuation component is applied to a driving signal for driving an analog resistance changing element composed of a pair of electrodes and an oxide layer provided between the pair of electrodes. It is characterized by overlapping.

Further, the drive signal is characterized in that it is a voltage fluctuation that causes a sufficiently small current fluctuation as compared with the current change of the element caused by the drive pulse of the voltage required for the analog resistance change.

Further, the drive pulse is a constant voltage of about several V, and the voltage fluctuation is a voltage of about 1/10 of the drive pulse.

Further, the drive pulse has a voltage of about several V, and the voltage is variable from the initial voltage to the end voltage at a predetermined step voltage, and the voltage fluctuation is characterized by a voltage of about 1/1000 of the drive pulse. And.

As described above, a larger resistance change is realized by superimposing a voltage having a fluctuation component on the drive signal that drives the analog resistance change element. That is, the resistance can be changed by the drive pulse of a lower voltage, so that the power consumption can be reduced. In addition, the flattening of the low resistance (SET) process and the high resistance (RESET) process is realized. Smooth resistance changes improve controllability, improve the efficiency of correction processing in the brain-type information processing process, for example, correction of various errors for elements and circuits, and as a result, reduce the power consumption of the brain-type information processing circuit. And high speed can be realized. As the drive signal, in addition to the method of continuously applying a drive pulse of a constant voltage, the voltage of the drive pulse can be variably applied for each step voltage.

According to the present invention, it is possible to reduce the power consumption of the analog resistance changing element and to flatten the resistance change with a simple structure.

FIG. 1 is a diagram showing a structural example of a resistance changing element according to an embodiment. FIG. 2 is a plan view showing a structural example of an analog resistance changing element included in the information processing apparatus according to the embodiment. FIG. 3 is a cross-sectional view of a contact hole portion located at the C point portion of FIG. FIG. 4 is a diagram showing an enlarged cross-sectional TEM image of the oxide layer portion shown in FIG. FIG. 5 is a chart showing a characteristic measurement result when voltage fluctuation is superimposed on the drive signal of the analog resistance changing element according to the embodiment. FIG. 6 is a chart illustrating the reproducibility of the superimposition effect of the voltage fluctuation applied to the embodiment. (Part 1) FIG. 7 is a chart illustrating the reproducibility of the superimposition effect of the voltage fluctuation applied to the embodiment. (Part 2) FIG. 8 is a diagram showing a mounting example of the analog resistance changing element of the embodiment. (Part 1) FIG. 9 is a diagram showing a mounting example of the analog resistance changing element of the embodiment. (Part 2) FIG. 10 is a chart showing characteristic measurement results when the analog resistance changing element according to another embodiment is driven by another driving method.

FIG. 1 is a diagram showing an example of the structure of RAND according to the embodiment. RAND101 has a structure in which an insulating oxide layer is sandwiched between electrodes. For example, the upper electrode (TE) 111 and the lower electrode (BE) 112 are titanium nitride TiN, respectively, and the oxide layer (MO) 113 is TaOx (tantalum pentoxide).

The oxide layer (MO) 113 has one layer or a plurality of layers of two or more. In the example of FIG. 2, the MO 113 is composed of two layers, MO1 (TaOx-L) 113-1 and MO2 (TaOx-H) 113-2. TaOx-L and TaOx-H are Ta oxide films having different resistivityes, and the resistivity is TaOx-L <TaOx-H.

By forming the oxide layer (MO) 113 as a layer having a plurality of resistivity, more desired resistance change characteristics can be obtained.

The resistance change in RAND101 is based on the redox reaction induced by the current. In RAND, the conductance increases in the process of lowering the resistance (Set), and the conductance decreases in the process of increasing the resistance (Reset).

For example, when a positive voltage is applied to the lower electrode (BE) 112 of the RAND 101 having a low resistance, oxygen ions move in the oxide layer MO 113, and oxidation progresses to increase the resistance of the MO2 layer, resulting in increased conductance in the entire RAND 101. Decrease.

FIG. 2 is a plan view showing a structural example of an analog resistance changing element included in the information processing apparatus according to the embodiment. In the analog resistance changing element 100, the RAND 101 is arranged on the Si substrate 200. A Drive voltage is applied to TE111 of RAND101.

An oxide layer (MO) 113 is provided between TE111 and BE112 of RAND101. MO113 is located between points B and C in FIG. BE112 of RAND101 is connected to ground (GND).

FIG. 3 is a cross-sectional view of a contact hole portion located at point C in FIG. 2.

In the cross-sectional view of FIG. 3, a 100 nm thermal oxide film (SiO ₂ ) 300 is formed on the Si substrate 200. For example, a Si substrate 200 with a thermal oxide film of 100 nm can be used. BE112 of RAND101 is provided on the Si substrate 200 with a thermal oxide film. Two layers of MO1 (TaOx-L) 113-1 and MO2 (TaOx-H) 113-2 having different resistivity as shown in FIG. 1 are provided on the BE 112 as the oxide layer (MO) 113. _{An insulating film 305 such as silicon oxide (SiO 2} ) is provided on the Si substrate 200, and the insulating film 305 is provided between the BE 112 and the MO 113 and covers the TE 111. Although not shown, a part of TE111 and a part of BE112 are derived to the front surface of the insulating film 305, respectively.

MO113 shown in FIG. 3 is composed of two layers of MO113-1 and 113-2, has a recess (contact hole) at point C, and is joined to BE112. RAND101 forms one circuit system from point A to point E in FIG.

FIG. 4 is a diagram showing an enlarged cross-sectional TEM image of the oxide layer portion shown in FIG. An image taken by a transmission electron microscope TEM (Transmission Electron Microscope) is shown, and the oxide layer 113 at the point C portion in FIG. 3 is enlarged. Two layers of MO1 (TaOx-L) 113-1 and MO2 (TaOx-H) 113-2 are laminated as an oxide layer (MO) 113 on a TiN layer corresponding to BE1 and BE2 (112). ..

The oxide layer (MO) 113 can be appropriately selected so as to obtain a desired resistance value. A TiN layer corresponding to TE111 is laminated on the MO 113, and an insulating film 405 (SiO ₂ ) and a protective carbon film (C film) are formed on the TiN layer.

For example, the layer thickness of TE111 is 60 nm, the layer thickness of two layers MO1 (TaOx-L) 113-1 and MO2 (TaOx-H) 113-2 is 30 nm, respectively, and the layer thickness of BE112 is 20 nm. Further, for example, the concave portion (point C in FIG. 2, contact hole) is 100 nm × 100 nm when viewed in a plane.

When the analog resistivity changing element 100 is bonded to the lower electrode BE (112) with the hole structure (contact hole) C described above, for example, the oxide layer (MO) 113 is a Ta oxide film on the lower electrode (BE) 112 side. Set a large resistivity.

On the other hand, in the structure of the oxide layer (MO) 113 having no hole structure C, for example, in the structure shown in FIG. 2, the oxide layer (MO) 113 has an upper electrode TE (111) and a lower electrode (BE). It has the same structure as the area of the interface with 112.

In the structure of the oxide layer (MO) 113 having no hole structure C described in FIG. 1, for example, one of the oxide layer MO1 (113-1) and the oxide layer MO2 (113-2) is 1000 mOhm ( Set mΩ) cm or more and the other to less than 1000 mOhm (mΩ) cm. Further, the oxide layer MO1 (113-1) and the oxide layer MO2 (113-2) may be arranged on either the upper or lower layer.

The resistivity of the oxide layer (MO) 113 has a positive correlation with x of TaOx, and the film thickness can be reduced. For example, among MO1 (113-1) and MO2 (113-2), the oxide layer (TaOx-H) having a high resistivity has a film thickness of 20 to 20 when the x of TaOx is 2 or more and 2.2 or less. When x of 40 nm and TaOx exceeds 2.2, it can be set to 3 to 10 nm. On the other hand, in the oxide layer (TaOx-L) having a low resistivity, x of TaOx is less than 2.

The oxide layer (MO) 113 has two layers of MO1 (113-1) and MO2 under different conditions for the amount of oxygen in the reactive sputtering gas between MO1 (113-1) and MO2 (113-2). (113-2) and (113-2) are continuously formed into a film. In addition, an annealing treatment may be performed in which the substrate is heated to 100 to 300 ° C. in a state of being assisted by radicals generated by applying RF power to argon gas containing oxygen. Further, in the oxide layer (MO) 113, x may be set to be larger than 2 on the side of MO1 (113-1) and MO2 (113-2) having a large amount of oxygen.

In the above configuration example, the pair of electrodes TE (111) and BE (112) are TiN, and the oxide layer (MO) 113 is TaOx, but the present invention is not limited to this. For example, the electrodes TE and BE can be appropriately selected from the metals of Pt, Au, Cu, TiAlN, TaN, W, Ir, and Ru, and the oxide layer MO can be HfOx, AlOx, SiOx, WOx, ZrOx in addition to TiOx. These dielectrics and their compounds, or oxides and oxynitrides of electrodes can be selected.

Next, the manufacturing method of the analog resistance changing element 100 (RAND101) will be briefly described. The analog resistance changing element 100 forms a RAND 101 on a Si substrate 200. A Drive voltage is applied to TE111 of RAND101, and BE112 is grounded.

The TiN film as the lower electrode (BE) 112 can be formed, for example, by reactive sputtering with _{Ar / N 2 gas using a Ti target.} In addition, it can be formed by sputtering using a TiN ceramic target, chemical vapor deposition (CVD), and atomic layer deposition (ALD). The lower electrode (BE) 112 is not limited to TiN, and TaN, W, Pt, and Ir may be used.

Next, the lower electrode (BE) 112 is patterned by photolithography and reactive ion etching. Next, for example, the entire front surface including the pattern of the lower electrode (BE) 112 is coated with the insulating film 305 of _{SiO 2 by CVD.}

Next, a hole structure (contact hole) C to be an element is formed on the insulating film (SiO _{2) 305 on the lower electrode (BE) 112.} This hole structure C can be formed by lithography and etching on the insulating film 305.

Next, two layers of MO1 (113-1) and MO2 (113-2) having different resistivity as an oxide layer (MO) 113 are formed on the insulating film 305 in which the hole structure (contact hole) C is formed. An upper electrode layer 111 that is formed and becomes a part of the upper electrode (TE) 111 is formed on the upper electrode layer 111.

Next, the oxide layer (MO) 113 and the upper electrode 111 are patterned by lithography and reactive ion etching. Next, the entire front surface including the oxide layer (MO) 113 and the upper electrode 111 is coated with the insulating film 305 of _{SiO 2.}

Next, after etching the insulating film 305, contact electrodes that are part of the upper electrode (TE) and the lower electrode (BE) are formed on the front surface, respectively. The contact electrode has a Ti adhesion layer on the substrate side and an Au / Ti laminated structure in which Au is laminated on the Ti adhesion layer. In addition, it can also be formed by a mixture of Au and Ti, Al or the like.

In the above manufacturing method, an example using photolithography was described. Not limited to this, pattern drawing may be performed using a method such as electron beam lithography or nanoimprinting. Further, when it is necessary to prevent damage due to a chemical reaction in the reactive ion etching process, polishing processing by ion milling may be performed. Further, the element structure may be formed by lift-off, not limited to simply scraping.

(About the superimposition of voltage fluctuation on the drive signal for the analog resistance changing element)
In the embodiment, a voltage fluctuation having a minute voltage height is superimposed on the drive voltage (Set / Reset pulse) for driving the analog resistance changing element 100 with respect to the voltage value of the drive voltage. The voltage fluctuation can be sufficiently effective at a voltage sufficiently lower than the drive voltage, for example, a voltage value less than 1/10 of the drive voltage.

As explained in the prior art, many technologies for enhancing the resistance to fluctuations in input signals and power output or noise have been disclosed for electronic devices and information processing devices. These conventional techniques are techniques for removing the influence of disturbance such as noise. On the other hand, the inventors have found that power consumption can be reduced and the resistance change process can be flattened by positively superimposing voltage fluctuations on the drive signal of the analog resistance change element 100. ..

The voltage fluctuation superimposed on the drive signal is, for example, white noise or Gaussian noise that can be easily generated in an electronic circuit. For example, the frequency band (Bandwidth) is 30 MHz and the voltage amplitude (Amplitude) is 100 mVpp. (Peek to peak). The type of voltage fluctuation may be, in addition to white noise, various waveforms such as repetition of a predetermined waveform, for example, a sine wave (sine wave), a triangular wave, or a square wave. The voltage fluctuation is not limited as long as it gives a fluctuation to the drive pulse of the voltage that drives the resistance change. Further, it is desirable that the frequency of the voltage fluctuation has a time determined as the reciprocal thereof equal to or less than the drive pulse width.

(Characteristic measurement results due to voltage fluctuation superimposition)
Next, the characteristic measurement result when the voltage fluctuation is superimposed on the drive signal for the analog resistance changing element 100 will be described.

FIG. 5 is a diagram showing a characteristic measurement result when voltage fluctuation is superimposed on the drive signal for the analog resistance changing element according to the embodiment. The horizontal axis is time (number of pulses), and the vertical axis is current value (μA). The drive signal (pulse condition) supplied to the analog resistance changing element 100 was 1.95 V for Set, −2.05 V for Set, and a cycle of 100 ns. In FIG. 5, the voltage fluctuation superimposed on the drive signal is Gaussian Noise, the frequency band is 30 MHz, and the voltage amplitude is 100 mVpp.

FIG. 5A shows a state in which only the drive signal is supplied to the analog resistance changing element 100 (that is, an existing drive state), and shows a state in which the drive voltage (Set / Reset) for three cycles is applied. As shown in FIG. 5A, it shows a characteristic that the resistance is lowered by the Set pulse in one cycle and the current value is continuously increased correspondingly. Further, the resistance is increased by the Reset pulse, and the current value is continuously decreased. This state is measured as a phenomenon in which the current value changes in a sawtooth shape with respect to the number of pulses on the horizontal axis. The current change amount iOFF in the Set process and the Reset process is 1 μA or less. Further, it is shown that the amount of change in current, that is, the magnitude of change in analog resistance tends to increase as the pulsed voltage value increases as long as the element is not destroyed.

When the waveform of the existing drive state shown in FIG. 5A is partially enlarged, the current waveform for each of the applied pulses P1 to Pn is not continuous. High resistance may occur when a pulse is applied in the process of low resistance. In the partially expanded Set process, the current value repeatedly rises and falls each time a pulse is applied. For example, it is a disordered (irregular) waveform in which the current value rises in the pulse P2 after the pulse P1, the current value falls in the pulse P3, and then the current value rises in the pulse P4.

In this way, the current value does not rise (increase) smoothly in the Set process, but shows a discontinuous (irregular) change. In the Reset process as well, the current value does not smoothly decrease (decrease) and shows irregular changes as in the Set process.

FIG. 5B shows the characteristics when the voltage fluctuation is superimposed (ON) on the drive signal. It is shown that even in the drive signal (pulse condition) in which the current change amount iOFF is only 1 μA or less, the current change amount iON is increased by superimposing the voltage fluctuation with a slight fluctuation width of 100 mVpp. In this case, the voltage (100 mVpp) applied as the voltage fluctuation is a voltage sufficiently lower than the drive voltage (Set: 1.95 V, Reset: -2.05 V), for example, a voltage value less than 1/10 of the drive voltage. Sufficient effect has been obtained. Then, under the pulse conditions shown in FIG. 5, the change state of the current value becomes smoother (continuous, one side of the serrated waveform) as shown in FIGS. 5 (b) and 5 (c) each time the measurement is repeated. Was observed to become flat).

The fluctuation width of the voltage fluctuation is larger than, for example, the current fluctuation value in the discontinuous waveform shown in the partial enlargement of FIG. 5 (a) (for example, the current fluctuation value when a pair of drive pulses P1-P2 is applied). By setting, the current change in the Set process and the Reset process can be continuously performed. That is, the voltage fluctuation may be a voltage fluctuation that causes a sufficiently small current fluctuation as compared with the current change of the element caused by the drive pulse of the voltage required for the analog resistance change.

The resistance value of the analog resistance changing element 100 appears as the reciprocal of the change in the current value. Therefore, according to the embodiment, the change in the resistance value of the analog resistance changing element 100 can be smoothed by superimposing the voltage fluctuation on the drive signal. At the same time, the amount of current change can be increased.

As a result, according to the embodiment, a smooth resistance change can be obtained by removing noise of the resistance change component in the analog resistance change element 100, and the power consumption and speed of the product-sum circuit can be reduced and increased. Become.

FIG. 6 is a chart illustrating the reproducibility of the superimposition effect of the voltage fluctuation applied to the embodiment. As in FIG. 5, the voltage fluctuation application conditions were Gaussian Noise, the frequency band (Bandwidth) was 30 MHz, and the voltage amplitude (Amplitude) was 100 mVpp.

In FIG. 6, the drive voltage (Set / Reset voltage) of the analog resistance changing element 100 is set to a lower voltage condition than the example (optimal condition) of FIG. 5, Set is 1.85 V, Set is -1. The cycle is .95V and 100ns.

Here, FIG. 6A is a state in which the voltage fluctuation is superimposed on the drive signal (ON), and FIG. 6B is a state in which the voltage fluctuation is not superimposed on the drive signal (OFF). The application of the drive voltage (Set / Reset) shows the state of 3 cycles (measured 13 times). Subsequent FIGS. 6 (c) to 6 (e) show a state in which the superimposition (ON) of the high voltage fluctuation is continued. FIG. 6D shows a state in which the drive voltage is applied for 3 cycles (measured 15 times), and FIG. 6 (e) shows a state in which the drive voltage is applied for 8 cycles (measured 8 times).

When the superimposition of the voltage fluctuation shown in FIG. 6A is switched from the state where the superimposition of the voltage fluctuation shown in FIG. 6B is ON to the superimposition of the voltage fluctuation shown in FIG. The current change amount iOFF becomes smaller than the current change amount iOFF shown in FIG. 5A corresponding to the condition lower than the condition 5.

However, as shown in FIG. 6 (c), the voltage fluctuation is superimposed (ON) again, and then, as shown in FIGS. 6 (d) and 6 (e), the voltage fluctuation is superimposed (ON). It has been shown that by continuing, the change in the current value of the analog resistance changing element 100 gradually becomes a smooth and stable sawtooth waveform. Then, as shown in FIG. 6, even when the drive voltage (Set / Reset voltage) of the analog resistance changing element 100 is set to a lower voltage than the example of FIG. 5 (optimal conditions), the voltage fluctuation is superimposed (ON). ) Is continued, it is shown that the change of the current value of the analog resistance changing element 100 can be made into a smooth and stable saw-like waveform, and the amount of the current change can be increased.

FIG. 7 is a chart illustrating the reproducibility of the superimposition effect of the voltage fluctuation applied to the embodiment. The conditions for applying the voltage fluctuation were a sine wave (Sin Noise), a frequency band (Bandwidth) of 30 MHz, and a voltage amplitude (Amplitude) of 100 mVpp.

FIG. 7 shows a state in which the superimposition of the voltage fluctuation shown in FIG. 7A is ON, and thereafter, FIG. 7B shows a state in which the superimposition of the voltage fluctuation is OFF and the superimposition is repeatedly turned ON / OFF. It should be noted that FIGS. 7 (f) and 7 (g) show a state in which ON is continued.

In addition, in FIG. 7, the drive voltage (Set / Reset voltage) of the analog resistance changing element 100 is set to a lower voltage condition than in the example of FIG. 6, Set is 1.80 V, Set is -1. The cycle is .85V and 200ns.

As shown in FIG. 7, even when the voltage fluctuation superimposition is repeatedly turned ON / OFF, every time the voltage fluctuation superimposition is turned ON, the current value of the analog resistance changing element 100 changes during this ON period. Has been shown to produce a smooth, stable sawtooth waveform. Then, as shown in FIG. 7, even when the drive voltage (Set / Reset voltage) of the analog resistance changing element 100 is set to a lower voltage than the example of FIG. 6, the voltage fluctuation is superimposed (ON). It has been shown that during this period, the change in the current value of the analog resistance changing element 100 can be made into a smooth and stable saw-like waveform, and the amount of change in the current can be increased.

From the measurement results of FIGS. 6 and 7, the analog resistance changing element 100 is used during the period when the voltage fluctuation superimposition is ON, regardless of whether the voltage fluctuation superimposition is continuously turned ON or ON / OFF is repeated. It has been shown that the change in the current value of can be a smooth and stable sawtooth waveform.

8 and 9 are diagrams showing a mounting example of the analog resistance changing element of the embodiment. FIG. 8 is a configuration example using the selection transistor 802, which is a typical circuit configuration used for a product-sum circuit or the like. An analog resistance changing element 100 constituting a memory cell and a selection transistor 802 are connected between the bit line (BL) and the source line (SL). The source of the selection transistor 802 is connected to the source line (SL), the drain is connected to one end of the analog resistance changing element 100, and the other end of the analog resistance changing element 100 is connected to the bit line (BL). A drive driver (WL Driver) 801 is connected to the gate of the selection transistor 802 via a word line (WL).

The drive driver 801 superimposes and supplies a drive signal (Set / Reset pulse) and a voltage fluctuation to the selection transistor 802. That is, the drive driver can be configured by adding a function of generating the above-mentioned voltage fluctuation and superimposing it on the drive signal to the existing drive signal (Set / Reset pulse) generation function of 801.

In the above-described embodiment, the empirical results regarding the analog resistance changing operation of the analog resistance changing element 100 are described. However, the present invention does not depend on whether the resistance change is an analog type or a digital type. Therefore, even for a normal non-volatile memory, the voltage fluctuation is superimposed on the drive signal to make it non-volatile. It is effective in reducing the operating voltage of the non-volatile memory.

Further, FIG. 9 is an example of a crosspoint type cell configuration, in which analog resistance changing elements 100 are arranged in a matrix at each crosspoint of a plurality of word lines (WL) and a plurality of bit lines (BL) intersecting each other. To. The bit line decoder 902 selects one bit line (BL) corresponding to the supplied address, and the word line decoder 903 selects one word line (WL).

The voltage pulse / fluctuation generation circuit 901 superimposes and supplies a drive signal (Set / Reset pulse) and a voltage fluctuation to the analog resistance changing element 100 selected on the cross point. That is, the voltage pulse / fluctuation generation circuit 901 can be configured by adding a function of generating the voltage fluctuation described above and superimposing it on the drive signal to the existing drive signal (Set / Reset pulse) generation function. Here, the voltage pulse / fluctuation generation circuit 901 may superimpose the voltage fluctuation on either the word line (WL) or the bit line (BL), or one of them. For example, by superimposing a voltage fluctuation on the bit line (BL) side, it is possible to superimpose the voltage fluctuation on the drive signal and supply it to the analog resistance changing element 100 whose address is specified, and change the resistance of the analog resistance changing element 100. Can be made to.

For example, using the structure of an existing memristor in which a plurality of RANDs are arranged adjacent to each other on a substrate, a plurality of analog resistance changing elements are formed in RAND units, and an arbitrary analog resistance changing element 100 is selected for each cross point. And can be operated.

Not limited to the mounting examples of FIGS. 8 and 9, the present invention can be applied to various drive circuits having a function of superimposing voltage fluctuations on drive signals. Here, as described above, since the voltage fluctuation is a voltage sufficiently lower than the drive voltage, for example, a voltage value less than 1/10 of the drive voltage, the power required to drive the analog resistance changing element 100 is reached. The increase can be suppressed, and the increase in the power consumption of the drive circuit and the information processing device can be suppressed.

(Other embodiments)
In the embodiment described above, a drive method is used in which a drive pulse having a constant voltage is continuously applied to the analog resistance changing element 100 at a predetermined cycle. On the other hand, in another embodiment described below, the driving method of the analog resistance changing element 100 is different. In the driving method of another embodiment, as a condition for applying the driving pulse to the analog resistance changing element 100, the applied voltage having a predetermined pulse width is varied from the initial value to the ending voltage for each predetermined step voltage.

For example, the conditions for applying the drive pulse in the Set process are an initial value (Initial Voltage) of 1 V, a step voltage (Voltage Step) of 0.05 V, a supply pulse number (No. of Pulse) of 13, and an end voltage (Finish). Voltage) is 1.6 V, and the pulse width (Pulse Wid) is 5 μs. By the way, also in other embodiments, voltage fluctuations such as high frequency noise are superimposed on the drive signal as in the above embodiment.

In another embodiment, for example, the drive pulse in the Set process is 1 V for the analog resistance changing element 100 in the Reset state, the second pulse is 1.05 V, 1.1 V, ..., 1.55 V. And increases by 0.05V, and the final pulse becomes 1.6V. In the Reset process, the voltage may be applied under the conditions for applying the drive pulse opposite to that in the Set process.

FIG. 10 is a chart showing the characteristic measurement results when the analog resistance changing element according to another embodiment is driven by another driving method. The horizontal axis is the resistance value of the analog resistance changing element 100 under the application condition of the drive pulse (Resistance [kΩ], and the vertical axis is the Weibull plot (Ln [Ln (1 / (1-F (R_i))). ]).

Then, by applying a drive pulse from 1V to 1.6V in 0.05V steps to the analog resistance changing element 100 in the high resistance state, the analog resistance changing element 100 is in the low resistance state. Here, the measurement was repeated under the condition of the presence or absence of high frequency noise. In FIG. 10, after that, the resistance value at the time when the drive voltage was 1.3 V was weibull plotted, and the variation in the resistance value was evaluated.

Measurement is 1. No high frequency noise 50 times, 2. With high frequency noise (Gaussian noise 1 mV, 20 MHz) 55 times, 3. No high frequency noise 50 times, 4. It was set to 50 times with high frequency noise (Gaussian noise 1 mV, 2 MHz). 1.2.3.4. The reproducibility of the measurement was made by alternately performing the measurement in the order of, that is, the measurement without high frequency noise and with high frequency noise.

Regarding the measurement results shown in FIG. 10, 1. No high frequency noise (marked with ■ in the figure) and 2. Compared with the presence of high frequency noise (□ in the figure), it corresponds to the embodiment. The one with high frequency noise (□) is 1. The distribution of resistance values is narrower than that without high-frequency noise (■). Similarly, 3. No high frequency noise (● mark in the figure) and 4. Compared with the presence of high frequency noise (marked with ◯ in the figure), it corresponds to the embodiment. Those with high frequency noise (○) are 3. The distribution of resistance values is narrower than that without high-frequency noise (●).

As described above, in the analog resistance changing element 100 of the other embodiment, the driving condition is the condition with noise 2.4. In the case of, the condition without noise 1.3. It was clarified that the resistance distribution became smaller as the resistance became lower than that. As described above, the small resistance distribution makes it possible for the analog resistance changing element 100 of the other embodiment to suppress the current variation.

In addition, in the drive method of the other embodiment shown in FIG. 10, the voltage of the high frequency noise can be made lower than that of the above-described embodiment. In the above-described embodiment, the drive pulse is about several V (for example, ± 2 V), and the voltage fluctuation (high frequency noise) is about 1/10 of the drive pulse (for example, ± 100 mV). On the other hand, in FIG. 10, the drive pulse is several V (for example, ± 1 V to ± 1.6 V), while the voltage fluctuation (high frequency noise) is 1/1000 of the drive pulse (for example, ± 1 mV), which is much lower. can do.

Further, as shown in the Weibull plot of FIG. 10, by varying the applied voltage of the drive pulse of the analog resistance changing element 100 for each step voltage by the drive method of another embodiment, the resistance value corresponding to each step voltage is changed. Can be obtained with good reproducibility. For example, even if Set / Reset is repeated, when the drive pulse is 1.2V, a predetermined resistance value corresponding to this 1.2V can always be obtained.

As described above, according to the present embodiment, the information processing apparatus includes an analog resistance changing element composed of a pair of electrodes and an oxide layer provided between the pair of electrodes, and an analog resistance changing element. It is provided with a drive circuit that superimposes and supplies a voltage fluctuation having a fluctuation component on the drive signal. According to such a configuration, it becomes possible to suppress a sudden resistance change in the process of lowering the resistance (SET) and the process of increasing the resistance (RESET) when the analog resistance changing element is driven.

Further, the drive circuit generates a drive pulse having a predetermined voltage as a drive signal, and as a voltage fluctuation, from the current fluctuation value in a discontinuous waveform generated when the resistance value of the analog resistance changing element changes based on the drive pulse. Can also be configured to generate a voltage value corresponding to a large swing width. This makes it possible to achieve low power consumption when driving the resistance changing element and flattening the resistance changing process.

Further, the drive pulse has a constant voltage of about several V, and the voltage fluctuation can be a voltage of about 1/10 of the drive pulse. For example, as described above, the drive pulse may be about ± 2 V, and the voltage fluctuation may be about ± 100 mV at a frequency of 30 MHz, and the drive voltage can be suppressed.

Further, the drive pulse is a voltage of about several V, the voltage can be varied from the initial voltage to the end voltage at a predetermined step voltage, and the voltage fluctuation can be a voltage of about 1/1000 of the drive pulse.

Further, the high frequency noise can be any of Gaussian noise, white noise, sine wave, triangular wave, and square wave. As described above, various general-purpose noises can be used as the voltage fluctuation.

Further, the analog resistance changing element can be connected to the selection transistor in memory cell units, and the drive circuit can be configured to supply the drive signal in which the voltage fluctuation is superimposed to the selection transistor. In addition, the analog resistance changing element is arranged at a plurality of cross points where the word line and the bit line intersect, the analog resistance changing element is driven and selected by the word line decoder and the bit line decoder, and the drive circuit is the word line decoder. Alternatively, it can be configured to supply a drive signal in which voltage fluctuations are superimposed to one of the bit line decoders. As described above, a plurality of analog resistance changing elements can be easily selectively driven by using a general-purpose circuit configuration.

From the above, according to the present embodiment, the drive signal for driving the analog resistance change element is superposed with the voltage fluctuation and supplied, and the power consumption at the time of driving is reduced and the resistance change process is achieved. Flattening can be achieved. By suppressing the irregular resistance change characteristic, the noise of the resistance change component can be removed, the resistance change becomes smooth, and the power consumption and the speed of the product-sum circuit can be reduced and increased. Further, it becomes possible to simultaneously obtain low power consumption and high reliability of the analog resistance changing element.

The present invention can be applied to electronic devices and information processing devices equipped with artificial intelligence, particularly brain-type information processing devices used in the field of edge computing.

100 Analog resistance change element 101 RAND
111 Upper electrode (TE)
112 Lower electrode (BE)
113 Oxide layer (MO, MO1, MO2)
200 Si substrate 305 Insulation film 801 Drive driver 901 Voltage pulse / fluctuation generation circuit

Claims

An analog resistance changing element composed of a pair of electrodes and an oxide layer provided between the pair of electrodes.
A drive circuit that superimposes and supplies a voltage fluctuation having a fluctuation component on the drive signal of the analog resistance changing element, and
An information processing device characterized by being equipped with.
The first aspect of the present invention is characterized in that the drive circuit generates a voltage fluctuation that causes a sufficiently small current fluctuation as compared with the current change of the element caused by the drive pulse of the voltage required for the analog resistance change. The information processing device described.
The information processing apparatus according to claim 2, wherein the drive pulse has a constant voltage of about several V, and the voltage fluctuation has a voltage of about 1/10 of the drive pulse.
Claim 3 is characterized in that the drive pulse is more preferably a voltage of about 1/10 of the drive pulse of about 0.3 V to 5 V used in an electronic device for IoT. The information processing device described in.
The drive pulse has a voltage of about several V, the voltage is variable from the initial voltage to the end voltage at a predetermined step voltage, and the voltage fluctuation is about 1/1000 of the drive pulse. Item 2. The information processing apparatus according to Item 2.
The information processing apparatus according to claim 1, wherein the voltage fluctuation is any one of Gaussian noise, white noise, sine wave, triangular wave, and square wave.
The analog resistance changing element is connected to a selection transistor in memory cell units.
The information processing apparatus according to claim 1, wherein the drive circuit supplies the drive signal in which the voltage fluctuation is superimposed to the selection transistor.
The analog resistance changing element is arranged at a plurality of cross points where the word line and the bit line intersect, respectively, and the analog resistance changing element is driven and selected by the word line decoder and the bit line decoder.
The drive circuit supplies the drive signal in which the voltage fluctuation is superimposed to either the word line decoder or the bit line decoder.
The information processing apparatus according to any one of claims 1 to 7.
A voltage fluctuation is superimposed on a drive signal for driving an analog resistance changing element composed of a pair of electrodes and an oxide layer provided between the pair of electrodes.
A method of driving an information processing device, which is characterized in that.
The ninth aspect of claim 9, wherein the drive signal is a voltage fluctuation that causes a sufficiently small current fluctuation as compared with the current change of the element caused by the drive pulse of the voltage required for the analog resistance change. How to drive an information processing device.
The driving method for an information processing apparatus according to claim 10, wherein the driving pulse has a constant voltage of about several V, and the voltage fluctuation has a voltage of about 1/10 of the driving pulse.
The drive pulse has a voltage of about several V, and the voltage is variable from the initial voltage to the end voltage at a predetermined step voltage, and the voltage fluctuation is a voltage of about 1/1000 of the drive pulse. The driving method of the information processing apparatus according to claim 10.