CN108807666B - A research method for the mechanism of resistive memory - Google Patents

Abstract

The invention discloses a method for researching the mechanism of a resistive random access memory, which comprises the following steps: step A, providing an active layer material used in the resistive random access memory, and manufacturing the active layer material into a thin film on a substrate; b, adjusting the AFM to be in a contact mode, and injecting carriers into the surface of the thin film by using a conductive atomic force probe to form a carrier injection region; and C, switching the AFM in situ to a surface potential measurement mode, continuously scanning a region containing the carrier injection region in a protective atmosphere to obtain a surface potential diagram of the scanned region, and evaluating the behavior capability of carriers in the active layer material according to the surface potential diagram. The invention carries out carrier injection and continuous scanning based on in-situ, further evaluates the injection, migration and retention capabilities of the carriers in the active material, further can judge whether the resistance change behavior is caused by trapping/releasing of charges by the active layer, and has accurate and reliable detection result.

Description

A research method for the mechanism of resistive memory

technical field

The present invention relates to the field of resistive memory, in particular to a method for researching the mechanism of resistive memory.

Background technique

The storage mechanism of resistive random access memory (RRAM) is that the active layer in the middle exhibits two stable resistances to store information under electrical excitation. "and 1". RRAM has a simple structure, and has the advantages of non-volatile, rewritable, and fast read and write speed.

At present, the research on the carrier behavior of the active layer of the resistive memory is mainly based on the fitting of the obtained current-voltage curve, and the corresponding resistance transition mechanism is proposed in combination with relevant theories. Since this method is only a fitting of the data and derivation according to some possible theories, the conclusions drawn need to be studied. This method is only suitable as an auxiliary proof for mechanistic studies.

Therefore, the existing technology still needs to be improved and developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a research method for the mechanism of the resistive memory, aiming to solve the problem that there is no relatively reliable carrier behavior of the active layer of the resistive memory in the prior art. Research methods.

The technical scheme of the present invention is as follows:

A research method for the mechanism of a resistive memory, including the following:

Step A, providing the active layer material used in the resistive memory, and making the active layer material into a thin film on the substrate;

Step B, adjusting the AFM to the contact mode, and using a conductive atomic force probe to inject carriers on the surface of the thin film to form a carrier injection region;

Step C. Switch the AFM to the surface potential measurement mode in situ, and continuously scan the region including the carrier injection region in a protective atmosphere to obtain a surface potential map of the scanned area, and evaluate the carrier according to the surface potential map. The ability of the current to behave in the active layer material.

In the method for researching the mechanism of the resistive memory, wherein, in the step A, the manufacturing method of the thin film is spin coating or thermal evaporation.

The method for researching the mechanism of the resistive memory, wherein, in the step A, the thickness of the thin film is 50-200 nm.

The research method for the mechanism of the resistive memory, wherein, in the step B, the method for injecting carriers into the surface of the thin film is: in two regions on the surface of the thin film, respectively conduct conductive Atomic force probes apply negative and positive biases.

In the method for researching the mechanism of the resistive memory, in the step C, the scanning area is more than 5 times the area of the carrier injection area.

The method for researching the mechanism of the resistive memory, wherein, after the step C, further comprising:

Step D, implementing bias operation on the thin film, using AFM and infrared spectroscopy combined technology to monitor the current information and infrared spectrum in the thin film in situ, and determine whether the active layer material has or not according to the in situ monitoring information A redox reaction occurs.

In the method for researching the mechanism of the resistive memory, wherein the bias voltage for biasing the thin film is 3-10V.

The research method for the mechanism of the resistive memory, wherein, after completing the steps in the above research method, further comprising:

Step E: Switch the AFM in situ to the CAFM mode, and perform imaging in the contact mode. For each imaging, a layer of the active layer material is scraped off with a conductive atomic force probe, and the continuously collected images are integrated to obtain the thin film. The current distribution diagram of the three-dimensional structure, according to the current distribution diagram to determine whether conductive filaments are formed in the active layer material.

The research method for the mechanism of the resistive memory, wherein the conductive atomic force probe is made of diamond material.

In the method for researching the mechanism of the resistive memory, when the conductive atomic force probe scrapes off a layer of the active layer material, the scraping force is a constant force of 10-100 nN.

Beneficial effects: The present invention provides a method for researching the mechanism of the resistive memory as described above. The present invention uses atomic force microscopy (AFM) to inject carriers on the surface of the active material thin film, and performs in-situ continuous scanning A surface potential map of the scanned area is obtained. According to the surface potential map, the ability of carrier injection, migration and retention in the active material can be evaluated, and then it can be judged whether the resistive switching behavior is caused by the capture/release of charges by the active layer, carrier injection and subsequent monitoring. All are carried out under in situ conditions, so the detection results are accurate and reliable. The research method of the present invention plays an important role in the research on the resistance transition mechanism of the resistive memory.

Description of drawings

FIG. 1 is a test diagram corresponding to the study of the trapping/releasing mechanism of the charge by the active layer material in Example 1 of the present invention.

FIG. 2 is an infrared spectrum test diagram corresponding to the study of the redox reaction mechanism in Example 1 of the present invention.

FIG. 3 is a test diagram corresponding to the research on the mechanism of the conductive filament in Example 1 of the present invention.

Detailed ways

The present invention provides a method for researching the mechanism of a resistive memory. In order to make the purpose, technical solutions and effects of the present invention clearer and clearer, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The present invention provides a preferred embodiment of a research method for the mechanism of a resistive memory, including the following:

Step A, providing the active layer material used in the resistive memory, and making the active layer material into a thin film on the substrate.

Specifically, the substrate (preferably a silicon wafer substrate) is cleaned first, and then the active layer material is made into a thin film on the substrate by spin coating or thermal evaporation. Since this process is a mature process, the present invention no longer Repeat. The thickness of the film is 50-200 nm (preferably 100 nm).

In step B, the AFM is adjusted to the contact mode, and a conductive atomic force probe is used to inject carriers on the surface of the thin film to form a carrier injection region.

Specifically, in the contact mode, the conductive atomic force probe (SCM-PIT) is used to inject electrons or holes into the surface of the film. Control the conductive atomic force probe to move a certain distance (for example, 2 μm), and then apply a positive bias voltage for hole injection.

Step C. Switch the AFM to the surface potential measurement mode in situ, and continuously scan the region containing the carrier injection region in a protective atmosphere (such as nitrogen) to obtain a surface potential map of the scanned region, according to the surface The potential map evaluates the behavior of charge carriers in the active layer material.

Preferably, the scanning area is more than 5 times the area of the carrier injection area to ensure that the carrier migration area can be fully covered.

In the present invention, AFM is used to inject carriers on the surface of the active material thin film, and in-situ continuous scanning is performed to obtain the surface potential map of the scanning area. According to the surface potential map, the ability of carrier injection, migration and retention in the active material can be evaluated, and then it can be judged whether the resistive switching behavior is caused by the capture/release of charges by the active layer, carrier injection and subsequent monitoring. All are carried out under in situ conditions, so the detection results are accurate and reliable. The research method of the present invention plays an important role in the research on the resistance transition mechanism of the resistive memory.

Further, the resistance transition mechanism of the resistive memory may also be based on the redox reaction of the active layer material. For this mechanism, the existing method is to use an electrochemical workstation to perform a cyclic voltammetry test on the active layer, and observe the active layer material in the active layer. Whether a redox reaction occurs under bias stimulation can be judged whether it is a redox mechanism. Since this method is performed in the liquid phase, there is a difference between the electrical stimulation experienced by the actual device and the accuracy is not high.

In view of the above problems, after the aforementioned step C, the present invention can also perform further in-situ detection to verify whether the resistance transition mechanism of the sample is based on the redox reaction of the active layer material, which specifically includes step D: the film or the conductive atomic force The bias voltage applied to the probe, preferably 3-10V, is too large to cause irreversible transformation of the sample, and too small cannot induce the resistive switching behavior of the material. The bias operation of the active layer can cause the resistive switching behavior of the active layer. Using the combined technology of AFM and infrared spectroscopy, the current information and infrared spectrum in the film are monitored in-situ, and the in-situ monitoring information is used to determine the Whether the active layer material undergoes redox reaction or not. Therefore, combining steps A to D, in-situ detection can be used to determine whether the resistance transition mechanism of the resistive memory is based on the capture/release of charges by the active layer material or the redox reaction of the active layer material.

Further, the resistance transition mechanism of the resistive memory may also be based on the "conductive filament mechanism (conductive filaments are formed in the active layer material)". For this mechanism, the existing method is to use transmission electron microscopy or scanning electron microscopy to study. Specifically, by taking a cross-sectional view of the resistive memory after the resistance transition, it is observed whether there are conductive filaments in the cross-section. This method can only be used to judge whether it is the mechanism of conductive filaments, and cannot realize the research of various mechanisms through in-situ detection.

In view of the above problems, the present invention can also perform further in-situ detection. After the redox mechanism and/or the conductive filament mechanism is studied, it also includes step E: switching the AFM in-situ to the CAFM (conducting atomic force microscope) mode, in the For imaging in contact mode, every imaging time, a conductive atomic force probe is used to scrape off a layer of the active layer material, and the continuously acquired images are integrated to obtain a current distribution diagram of the three-dimensional structure of the film. According to the current distribution The figure determines whether conductive filaments are formed in the active layer material. Preferably, the conductive atomic force probe is made of diamond material, and the scraping force of the probe is preferably a constant force of 10-100 nN. Due to the large rigidity of diamond, the strength of the probe can be well controlled, so that the Active layer material thickness per scratch.

The invention can realize the research and verification of three mechanisms (charge capture/release mechanism, redox mechanism and conductive filament mechanism) through in-situ detection of the active layer material of the resistive memory, and then judge the resistance of the resistive memory. transformation mechanism. Because it is based on in-situ detection, the detection results are more accurate and reliable.

The present invention will be described in detail below through examples.

Example 1

The atomic force microscope is the Fastscan atomic force microscope of Bruker. Bruker's SCM-PIT and conductive diamond atomic force probes were used, respectively.

(1) Sample making

Silk protein is used as the active layer material. The cut silkworm cocoons were dissolved in a 0.02M sodium carbonate solution and boiled in boiling water for 60 minutes to remove sericin contained in the silkworm cocoons. Residual fibers were rinsed with a large amount of deionized water and dried at room temperature overnight to obtain a crude fibroin product. Then, the crude fibroin product was completely dissolved with 9.3M lithium bromide solution, transferred to a dialysis bag (molecular weight cut-off of 3000), and dialyzed with ultrapure water for 3 days (the ultrapure water was replaced every 12 hours). Finally, the dialysate was centrifuged (rotation speed: 12000 rpm), and the supernatant was taken to obtain a silk protein solution. Using the obtained fibroin solution, a clean silicon wafer is used as the substrate, and the sample used for the test can be prepared by the method of spin coating.

(2) Research on carrier behavior

In the contact mode, the conductive atomic force probe is used to inject electrons or holes into the surface of the active layer material, a negative bias is applied to the conductive atomic force probe for electron injection, and then the conductive atomic force probe is controlled to move 2μm in the plane, and then A positive bias is applied to inject holes, and then, without changing the scanning position of the probe, the instrument is switched to the surface potential measurement mode, and the carrier injection area is scanned under the protection of nitrogen, and the scanning area is the carrier injection area. The results are shown in Figure 1. The darker circle area has a lower potential, representing the electron injection area, and the lighter color area (marked by a circle) has a higher potential, representing the hole injection area. The electron retention time of the silk protein active layer material can reach 3 hours, which proves that the protein layer has a strong ability to capture electrons.

(3) Research on the mechanism of redox reaction

Apply a bias voltage of 5 volts to the sample, and use AFM and infrared spectroscopy to monitor the current information and infrared spectrum of the silk protein sample in situ. The infrared spectrum is shown in Figure 2. There was basically no change in the peak position of the infrared spectrum, indicating that the resistance change of silk protein was not caused by redox reaction.

(4) Research on the mechanism of conductive filaments

Using the CAFM mode of the atomic force microscope, combined with a diamond conductive atomic force probe, imaging was performed in contact mode, and each image was scanned, and an active layer was scraped off with a scraping force of 40 nN. Continuous monitoring is carried out, and the continuously collected pictures are integrated with the drawing software to obtain the current distribution diagram of the three-dimensional structure of the active layer, as shown in Figure 3. The distribution diagram shows that there is no conductive filament path running through the Z direction in the three-dimensional diagram. It can be determined that the resistance-change mechanism of the active layer material in this embodiment is based on the principle of not metal conductive filaments.

To sum up, the present invention provides a research method for the mechanism of the resistive memory. The present invention can realize three mechanisms simultaneously (charge capture/release mechanism, oxidation of The reduction mechanism and the conductive filament mechanism) were researched and verified, and then the resistance transition mechanism of the resistive memory was judged. Because it is based on in-situ detection, the detection results are more accurate and reliable, which provides a new and reliable research method for the research on the resistance transition mechanism of resistive memory.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (10)

1. A method for researching a mechanism of a resistive random access memory is characterized by comprising the following steps:

step A, providing an active layer material used in the resistive random access memory, and manufacturing the active layer material into a thin film on a substrate;

b, adjusting the AFM to be in a contact mode, and injecting carriers into the surface of the thin film by using a conductive atomic force probe to form a carrier injection region;

and step C, switching the AFM to a surface potential measurement mode in situ, continuously scanning a region containing the carrier injection region in a protective atmosphere to obtain a surface potential diagram of the scanned region, evaluating the behavior capability of carriers in the active layer material according to the surface potential diagram, and determining whether the resistance change behavior is caused by trapping/releasing of charges by the active layer.

2. The method for studying the mechanism of the resistive random access memory according to claim 1, wherein in the step a, a method for manufacturing the thin film is spin coating or thermal evaporation.

3. The method for studying the mechanism of the resistance change memory according to claim 1, wherein in the step a, the thickness of the thin film is 50 to 200 nm.

4. The method for studying the mechanism of the resistance change memory according to claim 1, wherein in the step B, the method for injecting carriers into the surface of the thin film comprises: and respectively applying negative bias and positive bias to the conductive atomic force probe on two areas of the surface of the film.

5. The method for studying the mechanism of the resistance change memory according to claim 1, wherein in the step C, the scanning region is 5 times or more the area of the carrier injection region.

6. The method for studying the mechanism of the resistance change memory according to claim 1, further comprising, after the step C:

and D, performing bias operation on the film, monitoring current information and an infrared spectrogram in the film in situ by utilizing an AFM and infrared spectrum combined technology, and judging whether the active layer material generates an oxidation reduction reaction or not according to the information monitored in situ.

7. The method for studying the mechanism of the resistance change memory according to claim 6, wherein a bias voltage for applying a bias operation to the thin film is 3 to 10V.

8. The method for studying the mechanism of the resistive random access memory according to any one of claims 1 to 7, further comprising, after the steps in the studying method are completed:

and E, switching the AFM mode to a CAFM mode in situ, imaging in a contact mode, scraping a layer of the active layer material by using a conductive atomic force probe every time imaging is carried out, integrating continuously collected images to obtain a current distribution diagram of the three-dimensional structure of the film, and judging whether conductive filaments are formed in the active layer material according to the current distribution diagram.

9. The method for researching the mechanism of the resistive random access memory according to claim 8, wherein the conductive atomic force probe is made of a diamond material.

10. The method for studying the mechanism of the resistive random access memory according to claim 8, wherein when the conductive atomic force probe scrapes off a layer of the active layer material, the scraping force is a constant force of 10 to 100 nN.

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