CN108807666B - Research method of mechanism of resistive random access memory - Google Patents

Research method of mechanism of resistive random access memory Download PDF

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CN108807666B
CN108807666B CN201810459342.8A CN201810459342A CN108807666B CN 108807666 B CN108807666 B CN 108807666B CN 201810459342 A CN201810459342 A CN 201810459342A CN 108807666 B CN108807666 B CN 108807666B
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active layer
random access
access memory
resistive random
layer material
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CN108807666A (en
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吕子玉
周晔
韩素婷
王俊杰
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Shenzhen University
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    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20Multistable switching devices, e.g. memristors
    • H10N70/24Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
    • HELECTRICITY
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    • H01L22/00Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10Measuring as part of the manufacturing process
    • H01L22/14Measuring as part of the manufacturing process for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011Manufacture or treatment of multistable switching devices
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011Manufacture or treatment of multistable switching devices
    • H10N70/041Modification of switching materials after formation, e.g. doping
    • H10N70/043Modification of switching materials after formation, e.g. doping by implantation

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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

Research method of mechanism of resistive random access memory
Technical Field
The invention relates to the field of resistive random access memories, in particular to a method for researching the mechanism of a resistive random access memory.
Background
The storage mechanism of a Resistive Random Access Memory (RRAM) is as follows: the middle active layer shows two stable resistances to store information under electric excitation, and the high resistance state and the low resistance state respectively correspond to '0' and '1' in computer binary operation. The RRAM has the advantages of simple structure, non-volatility, repeated erasing and writing, high reading and writing speed and the like.
At present, the research on the carrier behavior of the active layer of the resistive random access memory mainly proposes a corresponding resistance transition mechanism by fitting an obtained current-voltage curve and combining a relevant theory. Since the method is only a fit to the data and derived from some possible theory, the conclusions to be drawn are left to be examined. The method is only suitable for being used as an auxiliary proof of mechanism research.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for researching the mechanism of the resistive random access memory, and aims to solve the problem that no relatively reliable method for researching the carrier behavior of an active layer of the resistive random access memory exists in the prior art.
The technical scheme of the invention is as follows:
a method for researching the mechanism of a resistive random access memory 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 method for researching the mechanism of the resistive random access memory comprises a step A of preparing a thin film by spin coating or thermal evaporation.
The method for researching the mechanism of the resistive random access memory comprises the step A, wherein in the step A, the thickness of the thin film is 50-200 nm.
In the method for researching the mechanism of the resistive random access memory, in the step B, the method for injecting carriers into the surface of the thin film includes: and respectively applying negative bias and positive bias to the conductive atomic force probe on two areas of the surface of the film.
In the method for researching the mechanism of the resistive random access memory, in the step C, the area of the scanning region is 5 times or more of the area of the carrier injection region.
The method for researching the mechanism of the resistive random access memory comprises the following steps of:
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.
The research method of the mechanism of the resistive random access memory is characterized in that the bias voltage for applying bias operation to the thin film is 3-10V.
The method for researching the mechanism of the resistive random access memory further comprises the following steps after the steps in the 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.
According to the research method of the mechanism of the resistive random access memory, the conductive atomic force probe is made of a diamond material.
The research method of the mechanism of the resistive random access memory comprises the step of scraping a layer of active layer material by a conductive atomic force probe, wherein the scraping force is a constant force of 10-100 nN.
Has the advantages that: the invention provides a method for researching the mechanism of the resistive random access memory, which adopts an Atomic Force Microscope (AFM) to inject carriers into the surface of an active material film and carries out in-situ continuous scanning to obtain a surface potential diagram of a scanning area. The injection, migration and retention capabilities of carriers in the active material can be evaluated according to the surface potential diagram, and then whether the resistance change behavior is caused by trapping/releasing of charges by the active layer or not can be judged, and the injection of the carriers and the subsequent monitoring are carried out under the in-situ condition, so that the detection result is accurate and reliable. The research method provided by the invention has an important role in the research of the resistance transformation mechanism of the resistive random access memory.
Drawings
Fig. 1 is a test chart corresponding to the study of the charge trapping/releasing mechanism of the active layer material in example 1 of the present invention.
FIG. 2 is a graph showing IR spectrum measurements corresponding to the investigation of redox mechanism in example 1 of the present invention.
Fig. 3 is a test chart corresponding to the study of the mechanism of the conductive filament in example 1 of the present invention.
Detailed Description
The invention provides a method for researching the mechanism of a resistive random access memory, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a preferable embodiment of a research method of a 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.
Specifically, a substrate (preferably a silicon wafer substrate) is cleaned, and then a thin film is formed on the substrate by using an active layer material through a spin coating or thermal evaporation method. The thickness of the film is 50-200nm (preferably 100 nm).
And B, adjusting the AFM to be in a contact mode, and injecting carriers into the surface of the film by using the conductive atomic force probe to form a carrier injection region.
Specifically, in a contact mode, an electron or a hole is injected into the surface of the film by using a conductive atomic force probe (SCM-PIT), and the injection method comprises the following steps: the electron injection is performed by applying a negative bias to the conductive atomic force probe, and then the hole injection is performed by controlling the conductive atomic force probe to move a distance (for example, 2 μm) in a plane and applying a positive bias.
And 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 (such as nitrogen) 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.
Preferably, the scanning region is 5 times or more the area of the carrier injection region to ensure that the entire carrier transfer region can be covered.
According to the method, carriers are injected on the surface of the active material film by adopting AFM, and in-situ continuous scanning is carried out to obtain a surface potential diagram of a scanning area. The injection, migration and retention capabilities of carriers in the active material can be evaluated according to the surface potential diagram, and then whether the resistance change behavior is caused by trapping/releasing of charges by the active layer or not can be judged, and the injection of the carriers and the subsequent monitoring are carried out under the in-situ condition, so that the detection result is accurate and reliable. The research method provided by the invention has an important role in the research of the resistance transformation mechanism of the resistive random access memory.
Further, the resistance transition mechanism of the resistive random access memory may also be based on the oxidation-reduction reaction of the active layer material, and for this mechanism, the existing method is to perform cyclic voltammetry on the active layer by using an electrochemical workstation, and to observe whether the active layer material undergoes the oxidation-reduction reaction under bias stimulation, so as to determine whether the oxidation-reduction mechanism is the oxidation-reduction mechanism. Because the method is carried out in a liquid phase, the method is different from the electrical stimulation experienced by an actual device, and the accuracy is not high.
In view of the above problems, after the step C, the present invention can further perform in-situ detection to verify whether the resistance transition mechanism of the sample is based on the redox reaction of the active layer material, and specifically includes the step D: and applying bias voltage, preferably 3-10V, to the film or the conductive atomic force probe, wherein the film or the conductive atomic force probe is too large to cause irreversible transformation of a sample, and the film or the conductive atomic force probe is too small to induce the resistance change behavior of the material. And performing bias operation on the active layer to cause the resistance change behavior of the active layer, monitoring current information and an infrared spectrogram in the film in situ by using an AFM and infrared spectrum combined technology, and judging whether the oxidation reduction reaction occurs in the active layer material according to the information monitored in situ. Therefore, in combination with steps a to D, it can be determined through in-situ detection whether the resistance transition mechanism of the resistive random access memory is based on the trapping/releasing of charges by the active layer material or on the oxidation-reduction reaction of the active layer material.
Further, it is also possible that the resistance transition mechanism of the resistance change memory is based on a "conductive filament mechanism (conductive filament is formed in the active layer material)". For this mechanism, the existing method is to use a transmission electron microscope or a scanning electron microscope for research. Specifically, whether a conductive filament exists in a cross section is observed by taking a cross section of the resistive random access memory after resistance transition. The method can only be used for judging whether the mechanism is a conductive filament mechanism, and can not realize the research of multiple mechanisms through in-situ detection.
In order to solve the problems, the invention can also carry out further in-situ detection, and after the redox mechanism and/or conductive filament mechanism research is carried out, the method also comprises the following step E: and switching an AFM (atomic force microscope) mode to a CAFM (conductive atomic force microscope) 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 performed, integrating continuously acquired images to obtain a current distribution diagram of the three-dimensional structure of the thin film, and judging whether conductive filaments are formed in the active layer material according to the current distribution diagram. Preferably, the conductive atomic force probe is made of a diamond material, the scraping force of the probe is preferably a constant force of 10-100nN, and the strength of the probe can be well controlled due to the fact that the diamond is high in rigidity, so that the thickness of an active layer material scraped each time is well controlled.
According to the invention, through in-situ detection on the active layer material of the resistive random access memory, research and verification of three mechanisms (a charge trapping/releasing mechanism, an oxidation-reduction mechanism and a conductive filament mechanism) can be simultaneously realized, and then the resistance transformation mechanism of the resistive random access memory is judged. Because the detection is based on in-situ detection, the detection result is more accurate and reliable.
The present invention will be described in detail below with reference to examples.
Example 1
The atomic force microscope is a Fastscan atomic force microscope from Bruker. SCM-PIT and conductive diamond atomic force probes from bruker were used, respectively.
(1) Sample preparation
Fibroin is used as an active layer material. Dissolving the cut silkworm cocoon in 0.02M sodium carbonate solution, boiling in boiling water for 60 min, and removing sericin contained in the silkworm cocoon. The residual fiber was rinsed with copious amounts of deionized water and dried overnight at room temperature to give a crude fibroin product. The fibroin crude product was then completely dissolved with 9.3M lithium bromide solution and transferred to a dialysis bag (cut-off molecular weight 3000) and dialyzed against ultrapure water for 3 days (ultrapure water was replaced every 12 hours). Finally, the dialyzate was centrifuged (rotational speed: 12000 rpm), and the supernatant was collected to obtain a fibroin solution. And (3) preparing a sample for testing by using the obtained fibroin solution and a cleaned silicon wafer as a substrate and adopting a spin coating method.
(2) Study of Carrier behavior
In the contact mode, the surface of the active layer material is injected with electrons or holes by using a conductive atomic force probe, negative bias is applied to the conductive atomic force probe to inject electrons, then the conductive atomic force probe is controlled to move for 2 μm in a plane, positive bias is applied to inject holes, then the instrument is switched to a surface potential measurement mode under the condition of not changing the scanning position of the probe, a carrier injection region is scanned under the protection of nitrogen, the scanning region is 5 times of the carrier injection region, and as a result, as shown in fig. 1, the potential of a dark circular region is lower and represents the electron injection region, and the potential of a light region (circle mark) is higher and represents the hole injection region. The electron retention time of the fibroin active layer material can reach 3 hours, and the fact that the protein layer has strong capture capacity on electrons is proved.
(3) Research on redox reaction mechanism
Applying a bias voltage of 5 volts to a sample, and monitoring current information and an infrared spectrogram of the fibroin sample in situ by utilizing an AFM and infrared spectrum combined technology, wherein the infrared spectrogram is shown in figure 2, the corresponding peak position of the infrared spectrogram of the fibroin before and after the device is started is basically unchanged, and the change of the fibroin resistance is not caused by an oxidation-reduction reaction.
(4) Conducting filament mechanism study
The CAFM mode of an atomic force microscope is utilized, a diamond conductive atomic force probe is combined, imaging is carried out in a contact mode, an active layer is scraped after one image is scanned, and the scraping force is 40 nN. Continuously monitoring, and integrating continuously acquired pictures by combining with drawing software to obtain a current distribution diagram of a three-dimensional structure of the active layer, as shown in fig. 3, the current distribution diagram sequentially corresponds to the current distribution diagram of the surface of the active layer after each thickness layer is scraped from bottom to top, a conductive wire passage penetrating through the three-dimensional diagram in the Z direction does not exist, and it can be determined that the resistance change mechanism of the active layer material in the embodiment is based on the principle of not being a metal conductive wire.
In summary, the invention provides a method for researching a mechanism of a resistive random access memory, and the method can simultaneously realize research and verification of three mechanisms (a charge trapping/releasing mechanism, an oxidation-reduction mechanism and a conductive filament mechanism) by in-situ detection on an active layer material of the resistive random access memory, so as to judge a resistance conversion mechanism of the resistive random access memory. Because the detection is based on in-situ detection, the detection result is more accurate and reliable, and a brand new and reliable research method is provided for the research of the resistance transformation mechanism of the resistive random access memory.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

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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CN110676379B (en) * 2019-09-30 2021-05-04 东华大学 Preparation method of multifunctional biological memristor based on fibroin nanofiber band
CN110676378B (en) * 2019-09-30 2021-05-04 东华大学 Method for preparing biological memristor based on fibroin nanofiber band
CN115078773B (en) * 2022-05-30 2024-09-13 华东师范大学 Ultrafast atomic force microscope system
CN115170472B (en) * 2022-05-31 2024-05-28 清华大学 Method and device for observing distribution and morphology of multiple conductive channels of resistive random access memory

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