WO2017124443A1

WO2017124443A1 - Multi-layer boron nitride-based rram device and preparation method therefor

Info

Publication number: WO2017124443A1
Application number: PCT/CN2016/071783
Authority: WO
Inventors: 吉艳凤; 潘成斌; 惠飞; 石媛媛; 肖娜; 马里奥兰扎
Original assignee: 苏州大学
Priority date: 2016-01-18
Filing date: 2016-01-22
Publication date: 2017-07-27
Also published as: CN105679785B; CN105679785A

Abstract

Provided are a multi-layer boron nitride-based RRAM device and a preparation method therefor. The RRAM device comprises a dielectric layer, a lower electrode and an upper electrode, wherein the dielectric layer is a multi-layer boron nitride, the lower electrode is a copper foil, and the upper electrode is titanium and gold. The preparation method comprises: (1) growing boron nitride by a chemical vapour deposition method to obtain a final boron nitride/copper foil sample, the substrate copper foil for growing the boron nitride serving as the lower electrode of the device; and (2) performing evaporation on a titanium electrode and a gold electrode using an electronic beam evaporation instrument and a mask plate. Compared with high dielectric material hafnium oxide devices, the device has stable electrical properties; the device preparation method is simple and avoids contamination of samples, caused by common transfer means for two-dimensional materials; and a mask plate is used for the direct evaporation of the upper electrode, avoiding microprocessing means such as photoetching.

Description

Multi-layer boron nitride based RRAM device and preparation method thereof

Technical field

The invention belongs to the field of information storage materials, and relates to a multi-layer boron nitride-based RRAM device and a preparation method thereof.

Background technique

Electronic information storage has become the mainstream demand of modern society. Among them, flash memory has the widest application due to its simple structure, high integration and fast speed. The core of this device is based on the charge and discharge of the capacitor and uses a sensor as a switch. However, when the device size is reduced, this structure has many physical defects. Therefore, a new method of storing information is urgently needed, and in recent years, in a non-volatile memory, a random resistive memory (RRAM) has attracted a great deal of attention.

The core of the RRAM is a metal-insulator-metal (MIM) structure that can be prepared by conventional microelectronic devices such as electron beam evaporators, sputters, atomic layer deposition, and the like. The memory forms a high resistance state (HRS) and a low resistance state (LRS) by changing the resistance of the insulating layer in the MIM, however the performance of the insulating layer has a great influence on the memory. It is well known that the size of memory cells is getting smaller and smaller, and conventional silicon dioxide cannot satisfy such a development trend because the size reduction causes tunneling of silicon dioxide, increases leakage current, and increases energy consumption. In addition, silicon dioxide interacts with the gate and substrate, reducing carrier mobility and degrading device performance. High dielectric materials are required at this time to reduce the thickness of the insulating layer while having a thicker dielectric layer. Researchers have introduced high dielectric materials such as yttrium oxide, which can solve the problems caused by dimensional efficiency. However, the electrical properties of yttrium oxide are unstable, and uneven thickness is easy to cause scattering, which brings new problems to the device.

Boron nitride is a sp2 hybrid two-dimensional material similar to graphene (lattice disorder only 1.7%), with superior physical and chemical properties, making it resistant to corrosion, flexible capacitors, transparent electrodes, Spintronics, field effect transistors and other aspects have great application prospects. Unlike graphene, boron nitride is an insulator with a band gap of 5.2 to 5.9 eV and a dielectric constant between 2 and 4. This makes boron nitride a good application prospect in logic electronics, such as Boron nitride can be combined with graphene and molybdenum sulfide to produce a metal-insulator-semiconductor structure (MIS) of pure two-dimensional material, which is the core structure of digital devices. The use of boron nitride in place of conventional insulating layers such as tantalum, titanium and aluminum oxides has several advantages: (i) the production of uniform thickness and flat boron nitride can significantly reduce the scattering effect in field effect transistors; Ii) Boron nitride has stronger chemical stability than graphene, avoiding reaction with adjacent metal layers and semiconductor layers; (iii) the high thermal stability of boron nitride can be used to enhance heat dissipation in electronic devices. Advantages; (iv) like other two-dimensional materials, boron nitride is soft Properties, mechanical and transparency can be used to make mechanically flexible optics.

Summary of the invention

Technical Problem to be Solved: The object of the present invention is to overcome the problem that the electrical properties of a high dielectric random resistive memory are unstable and easy to decay, and to introduce an advanced two-dimensional material, and to disclose a multi-layer boron nitride-based RRAM device and Preparation.

Technical Solution: In order to solve the above technical problem, the present invention discloses a multi-layer boron nitride-based RRAM device, which is characterized in that the RRAM device includes a dielectric layer, a lower electrode, and an upper electrode. The electric layer is a plurality of layers of boron nitride, the lower electrode is a copper foil, and the upper electrode is titanium and gold.

Preferably, the multi-layer boron nitride-based RRAM device has a thickness of 10 nm to 20 nm.

Preferably, the above-mentioned multi-layer boron nitride-based RRAM device has a thickness of 15-25 μm.

Preferably, the above-mentioned multi-layer boron nitride-based RRAM device has a titanium electrode thickness of 10 nm to 20 nm and a gold electrode thickness of 30-60 nm.

A method for preparing a multilayer boron nitride-based RRAM device, the method comprising the steps of:

(1) Boron nitride was grown by chemical vapor deposition, and boron borane was used as a precursor. The copper foil was annealed in a 10 sccm hydrogen atmosphere at a low pressure of 1000 ° C for 30 minutes, and the growth temperature of boron nitride was maintained at 750 ° C, time control is 5-30 minutes, the flow rate of borazane is 1-3sccm, hydrogen flow rate is 2000sccm; after the end of growth, the boron nitride / copper foil is annealed in 100sccm hydrogen, 100sccm nitrogen atmosphere for 1 hour, annealing The temperature is 1000 ° C, that is, the final boron nitride / copper foil sample is obtained, and the boron nitride grown substrate copper foil is used as the device lower electrode;

(2) Evaporating the titanium electrode and the gold electrode using an electron beam evaporation instrument and a mask: slowly increasing the electron beam power, the metal begins to evaporate, and then the electron beam power is increased until it reaches

When it is stable, the upper baffle is opened and the electrode is vapor-deposited. The thickness of the titanium electrode is 10-20 m, and the thickness of the gold electrode is 30-60 nm.

Preferably, the method for preparing a multilayer boron nitride-based RRAM device has a thickness of 10 nm to 20 nm.

Preferably, the method for preparing a multilayer boron nitride-based RRAM device has a thickness of 15-25 μm.

Compared with the prior art, the invention has the beneficial effects that the invention adopts a zero transfer method to prepare an ultra-thin dielectric layer RRAM device, and avoids the polymethyl methacrylate (PMMA) on the sample during the boron nitride transfer process. Pollution. The conventional device is based on a silicon wafer, and a lower electrode such as gold, platinum, titanium or the like is evaporated on the substrate. When prepared by CVD When boron nitride is a dielectric layer, it is necessary to transfer boron nitride from the copper foil to the lower electrode by using PMMA as a medium to obtain a structure of PMMA/boron nitride/upper electrode/wafer, but it has not been effectively removed so far. The transferred PMMA makes the sample contaminated, and the present invention does not need to transfer boron nitride, effectively avoiding sample contamination.

The invention adopts a mask plate to directly evaporate the upper electrode, thereby avoiding the use of photolithography to prepare the electrode and preventing the contamination of the photoresist. Conventional methods for preparing electrodes are to use ultraviolet lithography (preparation of large electrodes, electrode size greater than 1 μm) or electron beam etching (preparation of small electrodes, electrode size less than 1 μm), suspension coating of photoresist on the sample before lithography (using Positive glue, if the result of the negative glue is reversed, the light-transmitting area is not affected by the light), the photoresist in the light-transmitting area of the mask changes during photolithography, the macromolecular chain breaks, reacts with the developing solution, and the light-transmitting part is made The sample is exposed, and the sample in the opaque region is still covered with photoresist, and then the evaporation of the upper electrode is performed, and the photoresist outside the electrode is removed. Among them, the removal process of the two photoresists is incomplete, directly affecting the quality of the upper electrode, making the upper electrode incomplete and incomplete contact with the dielectric layer.

The invention adopts two-dimensional boron nitride as a dielectric layer and has high reliability. Compared with the popular high dielectric material yttrium oxide, the electrical properties of boron nitride RRAM are stable, and the electrical curve of yttrium oxide fluctuates greatly and decays rapidly.

The invention is easy to introduce industrial application CVD boron nitride can be mass-produced, zero-transfer direct evaporation of the upper electrode, the preparation process is simple, and the mass production and application of the microelectronic device can be easily realized.

DRAWINGS

Figure 1 is a cycle diagram of a resistance switch (electrode is 100μm x 100μm) collected by the probe station;

2 is a schematic structural view of the device;

3 is a scanning electron microscope (SEM) image of a single layer boron nitride/copper foil grown by the CVD method of the present invention;

4 is a current atomic force microscope (CAFM) current diagram of boron nitride of the present invention;

Figure 5 (a) is the IV curve of boron nitride at the same position, (b) is the Weber distribution of the voltage corresponding to the three current thresholds in Figure 6 (a);

Figure 6 (a) is the IV curve of yttrium oxide at the same position, (b) is the Weber distribution of the voltage corresponding to one current threshold in Figure 7 (a);

Figure 7 is a graph showing the relationship between the initial voltage of boron nitride and yttrium oxide (the voltage corresponding to the selected threshold current) and the number of IV curves;

Figure 8 is an SEM image of the device;

Fig. 9(a) shows the high resistance and low resistance of the electrode at the IV curve of Fig. 12 at 0.1 V, and (b) is the Weber distribution corresponding to the high resistance value and the low resistance value of (a).

detailed description

Example 1

(1) Boron nitride was grown by chemical vapor deposition, and boron borane was used as a precursor. The copper foil was annealed in a 10 sccm hydrogen atmosphere at a low pressure of 1000 ° C for 30 minutes, and the growth temperature of boron nitride was maintained at 750 ° C, time control at 15 minutes, the flow rate of borazane is 3sccm, hydrogen flow rate is 2000sccm; after the end of growth, the boron nitride / copper foil is annealed in 100sccm hydrogen, 100sccm nitrogen atmosphere for 1 hour, annealing temperature is 1000 ° C The final boron nitride/copper foil sample is obtained, and the boron nitride grown substrate copper foil is used as the device lower electrode;

When it is stable, the upper baffle is opened and the electrode is vapor-deposited. The thickness of the titanium electrode is 10 nm, and the thickness of the gold electrode is 50 nm.

The present invention will be further described below in conjunction with the accompanying drawings.

Please refer to FIG. 1, which is a cycle diagram of a resistor switch of the present invention. The schematic diagram of the present invention is as shown in FIG. 2, using a copper foil as a substrate to grow a plurality of layers of boron nitride by a CVD method, and on the basis of the evaporation of the upper electrode titanium and gold by an electron beam evaporator, the thickness of the upper electrode is respectively It is 10 nm titanium and 50 nm gold. 3 is an SEM image of a single layer of boron nitride grown by a CVD method, and characteristics of a two-dimensional material such as wrinkles, island-like multilayer regions, and copper foil steps are very clear. In addition, atomic force microscopy has also been introduced to study the reliability of single-layer boron nitride. The electrical diagram is shown in Figure 3. The analysis shows that the single-layer region accounts for 82%; respectively, applying 3V voltage at the same position of boron nitride and tantalum oxide. As shown in Fig. 4 and Fig. 5, the IV curve can be observed, and the electrical properties of boron nitride can be stabilized. The ruthenium oxide has many internal defects, the electrical curve is uncontrollable, and it is easy to generate charge trapping, stress-induced leakage current and breakdown. This causes the yttrium oxide to decay rapidly (Figure 6), while boron nitride remains stable. According to this electrical property, we use a plurality of layers of boron nitride to directly evaporate 10 nm of titanium and 50 nm of gold as the upper electrode on the boron nitride/copper foil, and the power of the electron beam evaporation apparatus used is 6% and 12%, respectively. A smooth evaporation rate is obtained. In the evaporation process, the electron beam mask produced by Tecan Company is used to directly evaporate the upper electrode without using photolithography to avoid contamination of the sample by the photoresist. 2 is a schematic view of the device, and FIG. 7 is an SEM image of the device. The probe station is introduced and measured by two ends. One end of the probe is connected to the copper foil and grounded, and the other end is connected to the electrode. A circulating voltage of -1 V to 1 V is applied and a protection current of 50 μA is applied. FIG. 1 is a cyclic switch diagram of the device. Figure 9 is a graph showing the relationship between high resistance and low resistance of the cycle diagram and the number of cycles. It can be seen that the switching ratio is greater than one order of magnitude. The invention is a device with stable electrical properties and high reliability.

Example 2

(1) Boron nitride was grown by chemical vapor deposition, and boron borane was used as a precursor. The copper foil was annealed in a 10 sccm hydrogen atmosphere at a low pressure of 1000 ° C for 30 minutes, and the growth temperature of boron nitride was maintained at 750 ° C, time control at 15 minutes, the flow rate of borazane is 3sccm, hydrogen flow rate is 2000sccm; after the end of growth, the boron nitride / copper foil is annealed in 100sccm hydrogen, 100sccm nitrogen atmosphere for 1 hour, annealing temperature is 1000 ° C To get the final boron nitride / a copper foil sample, a boron nitride grown substrate copper foil as a device lower electrode;

(2) Evaporating the titanium 1 electrode and the gold electrode using an electron beam evaporation instrument and a mask: slowly increasing the electron beam power, the metal begins to evaporate, and then the electron beam power is increased until it reaches

When it is stable, the upper baffle is opened and the electrode is vapor-deposited. The thickness of the titanium electrode is 20 nm, and the thickness of the gold electrode is 30 nm.

Example 3

When it is stable, the upper baffle is opened and the electrode is vapor-deposited. The thickness of the titanium electrode is 15 nm, and the thickness of the gold electrode is 60 nm.

Comparative example 1

A 300 nm thick silicon dioxide sheet (300 nm SiO ₂ /n-Si) was used as a substrate, and 50 nm Pt was vapor-deposited as a lower electrode by an electron beam evaporation apparatus. Since the silicon substrate was not electrically conductive, a part of the ruthenium oxide was deposited on the Pt. Pt, when it is tested under an atomic force microscope, the lower electrode and the sample stage can be connected by silver glue to form a passage. When depositing yttrium oxide, a magnetron sputtering apparatus (manufacturer: Kurt J. Lesker, model: PVD75) was used and the yttrium oxide having a purity of 99.999% was used as a source to maintain a chamber pressure of 3 mtorr and an argon gas flow rate of 5 sccm at 100 W. Under the power, sputter 500s. It can be seen from FIG. 6 and FIG. 7 that the electrical properties of yttrium oxide are unstable, internal defects are liable to cause charge trapping, leakage current caused by stress, and breakdown, which leads to rapid decay of yttrium oxide.

Claims

A multi-layer boron nitride-based RRAM device, characterized in that the RRAM device comprises a dielectric layer, a lower electrode and an upper electrode, the dielectric layer is a plurality of layers of boron nitride, and the lower electrode For copper foil, the upper electrode is titanium and gold.
A multilayer boron nitride-based RRAM device according to claim 1, wherein said multilayer boron nitride has a thickness of 10 nm to 20 nm.
A multilayer boron nitride-based RRAM device according to claim 1, wherein said copper foil has a thickness of 15 to 25 μm.
A multi-layer boron nitride-based RRAM device according to claim 1, wherein said titanium electrode has a thickness of 10 nm to 20 nm and a gold electrode has a thickness of 30-60 nm.
A method for preparing a multi-layer boron nitride-based RRAM device, characterized in that the preparation method comprises the following steps:

(1) Boron nitride was grown by chemical vapor deposition, and boron borane was used as a precursor. The copper foil was annealed in a 10 sccm hydrogen atmosphere at a low pressure of 1000 ° C for 30 minutes, and the growth temperature of boron nitride was maintained at 750 ° C, time control is 5-30 minutes, the flow rate of borazane is 1-3sccm, hydrogen flow rate is 2000sccm; after the end of growth, the boron nitride / copper foil is annealed in 100sccm hydrogen, 100sccm nitrogen atmosphere for 1 hour, annealing The temperature is 1000 ° C, that is, the final boron nitride / copper foil sample is obtained, and the boron nitride grown substrate copper foil is used as the device lower electrode;

(2) Evaporating the titanium electrode and the gold electrode using an electron beam evaporation instrument and a mask: slowly increasing the electron beam power, the metal begins to evaporate, and then the electron beam power is increased until it reaches
When it is stable, the upper baffle is opened and the electrode is vapor-deposited. The thickness of the titanium electrode is 10-20 nm, and the thickness of the gold electrode is 30-60 nm.
A method of fabricating a multilayer boron nitride-based RRAM device according to claim 5, wherein said multilayer boron nitride has a thickness of 10 nm to 20 nm.
The method of fabricating a multilayer boron nitride-based RRAM device according to claim 5, wherein the copper foil has a thickness of 15-25 μm.