KR20190136739A - Method of fabrication of NbOx selector device by pulsed laser annealing and selector device fabricated by the same - Google Patents

Abstract

A manufacturing method of a selection element of the present invention can comprise: a step of depositing an Nb_2O_5 film on a patterned substrate which a bottom Pt electrode is exposed; and a step of irradiating a laser to the Nb_2O_5 film. Therefore, the present invention has an advantage of being able to control a forming voltage by increasing a crystallization by adjusting a pulse repetition rate.

Description

Method of fabricating a NbOx selector using a pulsed laser and a selector manufactured by the same {Method of fabrication of NbOx selector device by pulsed laser annealing and selector device fabricated by the same}

Various embodiments of the present invention relate to a method of manufacturing a selection device, and more particularly, to a method of forming a NbOx based selection device using a pulsed laser by a low temperature process.

3D-cross point array is suitable for next-generation memory (PRAM, RRAM, MRAM), and has the advantages of minimum cell size (4F ² ), simple structure (metal / insulator / metal), and high stackability (3D stack). Have. However, in such a structure, when a read voltage is applied, a current may flow in an undesired direction. Therefore, it is necessary to connect the selector directly to the memory so that the current flows only to the desired cell. Among these candidates, NbO ₂ is based on threshold switching with insulator-metal transitions (eg IMT), large theoretical selectivity (high Ion / Ioff ~ 10 ⁷ ), and fast (~ ²² ns). It is a suitable material for selection because it has advantages such as uniform threshold switching and high temperature operation stability. Therefore, many studies have been conducted to solve the large selection ratio, the control of the forming process (a voltage having a large operating voltage to impart crystallinity when the initial voltage is applied).

In the fabrication of existing NbO ₂ based selectors, Nb cations have a variety of valences, and the NbO ₂ phase itself is very difficult to synthesize because it is susceptible to oxygen. Oxide or Nb ₂ O ₅ Nb metal target in the sputtering system In the method of synthesizing NbO ₂ by reducing the target, it is very sensitive to the injection amount of oxygen and hydrogen. In addition, high-temperature synthesis and heat treatment processes are required in the fabrication of selective devices with high selectivity and low forming voltage. This high temperature process is used to increase the temperature of the entire chamber rather than directly applying only the sample, so it takes a lot of time to raise and lower the temperature, which is a very low thermal efficiency method. In addition, it can not be used simultaneously with heat-vulnerable materials and can be a major disadvantage in the semiconductor process that goes through several steps to make a single memory.

The present invention can provide a method for manufacturing a NbOx selection device capable of low-temperature processing and excellent performance in order to solve the above problems. Specifically, the present invention can be injected locally by precisely adjusting the desired region by a method using a photo-thermal effect that directly injects energy into the local region using a laser. Therefore, energy efficiency is very high, and it does not raise the temperature of the whole sample, so heat-sensitive materials can be used. In addition, because the temperature rise and fall time is very short (> 10 ^6o Cs ^-1 ), fast-processing is possible, which can greatly increase the yield. In addition, the present invention is a method that is not affected by the deposition environment of the NbO _x film, it can be applied regardless of the deposition environment.

A method for manufacturing a selection device of the present invention comprises the steps of depositing an Nb ₂ O ₅ film on a patterned substrate to which the lower Pt electrode is exposed; And irradiating a laser to the Nb ₂ O ₅ film, and depositing an upper pt electrode.

The present invention confirmed that the NbO ₂ based selection device can be manufactured by performing laser irradiation on the synthesized Nb ₂ O ₅ film irrespective of the deposition conditions while controlling the pulse repetition rate and the process environment. In particular, the method using a laser has an advantage that an NbO ₂ based selection device can be manufactured regardless of the initial state of the sample, that is, the growth conditions of the Nb ₂ O ₅ film. In addition, by controlling the pulse repetition rate to increase the crystallization, it has the advantage that the forming voltage can be controlled. The selection device manufactured in this way has a selectivity of ~ 100 or more, 100cycles uniformly and durable up to 1000cycles or more. This performance is comparable to or better than that of previous reports of NbOx selective devices using Nb ₂ O ₅ sputtering targets using high temperature processes.

1 is a schematic diagram of a method of manufacturing a threshold switching-based selection device of the present invention.
2 (a) shows Nb ₂ O _{5 -α} (4 <α <5) according to the first embodiment IV characteristic graph of the unipolar resistance switching behavior in the based resistance change memory, Figure 2 (b) is a schematic diagram of the resistance change memory device.
3A is a schematic diagram of a laser irradiation step of adjusting the characteristics of the device by controlling the number of laser pulses and the irradiation atmosphere. FIG. 3B is a graph showing IV characteristics of unipolar resistance switching behavior of the resistance change memory according to the second embodiment and a schematic diagram thereof. FIG. 3C is a graph illustrating an electrical field induced insulator to metal transition (E-IMT) phenomenon in DC IV measurement of an NbO _x device (selection device) according to a third embodiment. 3D is a graph of IV characteristics of the forming phenomenon and the E-IMT phenomenon appearing in the selection device according to the fourth embodiment. 3 (e) shows a DC endurance test result of up to 1000 cycles of the NbO _x selector.
Figure 4 (a) is an X-ray diffraction (GIXRD or GID) graph measured in grazing incidence mode according to the laser irradiation repetition rate. 4B is a GIXRD graph according to the laser irradiation environment (Pt is denoted by *, O-Nb ₂ O ₅ is denoted by ▲, and t-NbO ₂ is denoted by). In addition, (c) and (d) of FIG. 4 are images of a lattice (interface distance, crystallization) and FFT (Fast Fourier Transform) viewed using a spherical aberration correction transmission electron microscope before and after laser irradiation (annealing).
5A is an XPS spectrum of Nb 3d according to the number of laser pulses. 5B is an XPS spectrum of Nb 3d according to the change of the laser irradiation environment. 5 (c) is a graph in percent by percentage of the surface area Nb ^{4 +} Nb 3d spectrum occupies the entire screen. 5 (d) is a graph showing the percentage of the area occupied by the non-lattice oxygen in the entire O 1s spectrum. In addition, the binding energy of O-Nb is indicated on the right axis.
FIG. 6A is an XPS spectrum of O 1s according to the number of laser pulses. 6B is XPS spectrum of O 1s according to the laser irradiation environment.
The graph of FIG. 7 is a result of arranging the graph of FIG. 8. (a) is a result of the IV curve according to the deposition environment of the NbO _x film. Figure 7 (b) is a result of arranging the IV curve according to the deposition time of the NbOx film. FIG. 7C is a spectrum showing forming voltage according to the number of laser pulses.
8 (a) is a DC IV curve according to the deposition time of the NbOx film. 8 (b) is a DC IV curve according to the deposition environment of the NbOx film.

Hereinafter, various embodiments of the present disclosure will be described with reference to the accompanying drawings. The examples and terms used herein are not intended to limit the techniques described in this document to specific embodiments, but should be understood to include various modifications, equivalents, and / or alternatives to the examples.

Various embodiments of the present invention relate to a method of manufacturing a selection device. Specifically, the present invention relates to a method of forming an NbO ₂ based selection device by a low temperature process.

According to various embodiments, a method of manufacturing a selection device may include depositing an Nb ₂ O ₅ film on a patterned substrate; And irradiating a laser to the Nb ₂ O ₅ film.

In this case, the patterned substrate may include holes of 200 nm to 300 nm. The patterned substrate may be a substrate in which a lower SiO ₂ layer, a TiN layer, a lower Pt electrode layer, and an upper SiO ₂ layer are sequentially deposited on the Si substrate. In the patterned substrate, holes of 200 nm to 300 nm may be formed by partially etching the upper SiO ₂ layer. The lower Pt electrode layer may be exposed in the hole. In detail, the patterned substrate may be a substrate patterned with holes of 200 nm to 300 nm.

Nb ₂ O ₅ or NbO _x thin films may be deposited on such a substrate. These films can be deposited from 30 nm to 50 nm using an ultra-high vacuumed radio frequency magnetron sputtering system.

In the step of irradiating the laser onto the Nb ₂ O ₅ thin film, the pulsed laser can be irradiated while the patterned substrate is transferred to a small chamber and the laser irradiation environment is controlled through gas injection, which can have a significant effect on the process. After the irradiation of the laser, the method may further include forming an upper Pt electrode by sputtering.

In the step of irradiating the laser, KrF (a krypton fluoride) pulsed laser may be irradiated. In addition, with a laser energy of 1.8 W, it can be irradiated at the number of repetitions of 3000 to 10000 pulses. The power and pulse repetition rate of such a laser are important factors for raising the temperature and maintaining the temperature instantaneously using the laser. The power of the laser can be finely adjusted to control the temperature at which the material reaches, and the number of pulses of the pulsed laser can be adjusted to determine how much thermal energy to inject. That is, the electrical characteristics of the NbO- _x based selector are changed according to the number of pulses of the laser. When 3000 to 10000 pulses are irradiated, the amount, selectivity, and off-current of NbO ₂ distributed in the NbO _x film is changed. I can regulate it.

In the step of irradiating the laser, by reducing the process environment, in particular, by reducing the composition (H ₂ gas injection) it can promote the reduction reaction. For example, the laser may be irradiated in Ar gas atmosphere or 1% to 5% H ₂ forming gas atmosphere. The laser is irradiated in a more reducing atmosphere, thereby promoting a reduction reaction in the Nb ₂ O ₅ film.

In the present invention, by using a photo-thermal effect that generates energy by directly injecting energy into a local region using a laser, it is possible to precisely control a desired region and inject energy locally. Therefore, energy efficiency is very high, and it does not raise the temperature of the whole sample, so heat-sensitive materials can be used. In addition, the time to raise and lower the temperature is very short (> 10 ^{6 o} Cs ^-1 ) Fast-processing can greatly increase the yield.

In the present invention, irrespective of the deposition conditions, it was confirmed that the NbO ₂ based selection device could be manufactured by performing laser irradiation on the synthesized Nb ₂ O ₅ sample while controlling the repetition rate and the environment. In particular, the method using a laser has the advantage of manufacturing an NbO ₂ based selection device regardless of the initial state of the sample (growth conditions of the Nb ₂ O ₅ film). In addition, by controlling the repetition rate to increase the crystallization, it has the advantage that the forming voltage can be controlled. The selection device manufactured as described above has a selectivity of ~ 100 or more, up to 100 cycles, and a DC endurance up to 1000 cycles or more. This is comparable to or better than the performance of NbOx selection devices using high temperature processes as Nb ₂ O ₅ sputtering targets.

Hereinafter, specific examples are as follows.

NbO according to laser pulse repetition rate and irradiation atmosphere _x  Electrical Characteristics of the Device

Embodiment 1: Ar gas atmosphere and 3000 pulses of laser

Referring to FIG. 1A, a 40 nm Nb ₂ O ₅ film is deposited on a Pt / TiN / SiO ₂ / Si substrate having a 250 nm hole by using an ultra-high vacuumed radio frequency magnetron sputtering system. After that, referring to Figure 1 (b), the pulsed laser was irradiated while controlling the laser irradiation environment through the gas injection after moving to a small chamber for the laser irradiation process. Referring to (c) of FIG. 1, the Pt / NbO _x / Pt (metal / insulator / metal) structure is finally formed by depositing 40 nm of the upper Pt electrode on the DC-sputtering-system again after laser irradiation (annealing). Prepared.

First, laser 3000 pulses with an energy of 1.8 W were irradiated onto the sample while flowing Ar gas into the chamber to make the process environment Ar (80 mL / cm ² ).

As a result, as shown in FIG. 2A, a forming process occurred at 4V when the first voltage was applied to the Nb ₂ O _{5 -α} (4 <α <5) device. 2B is a schematic diagram showing the state of the device before the initial voltage is applied. At an additional voltage, the current dropped to ~ 56uA at 3mA at 0.7V. This is called a reset phenomenon and the device changes from a low resistive state (LRS) to a high resistive state (HRS). Applying successive voltages undergoes a resistance change with a sharp rise in current from 3.8V to 1 mA at ~ 34uA. This process is called set, and the device is changed from HRS to LRS.

Second embodiment: Ar gas atmosphere and 5000 laser pulses applied

DC IV measurement was performed on the device subjected to 5000 pulses with a pulsed laser in an Ar gas atmosphere. As shown in (b) of FIG. 3, in the case of the Nb ₂ O _{5 -δ} (4 <δ <5, α <δ) device, the forming process that occurred in the previous device is not observed, and when the first voltage is applied. A reset occurred first with the current dropping to 5.7uA at 6mA. In addition, when the voltage was repeatedly applied, a set phenomenon occurred in which the current rose from 3.5uA to 1mA again at 3.5V. Subsequently, when the voltage was applied continuously, the set / reset occurred repeatedly. As a result, the switching characteristics of the ReRAM based on the unipolar reset first resistance switching behavior of the LRS and HRS are changed repeatedly with each voltage application. In the case of the devices of FIGS. 2A and 2B, the top electrode is not sufficiently formed because the conductive filament based on the oxygen vacancy is not sufficiently formed in the Nb ₂ O _{5 -α.} A forming process was needed to form a conductive filament between the bottom and bottom electrodes. However, referring to the schematic diagram inserted in (b) of FIG. 3, a device subjected to 5000 pulse laser irradiation has already formed a conductive filament due to sufficient oxygen pore formation during the laser irradiation process. The reset phenomenon has been observed.

Third embodiment: applying 5% forming gas atmosphere and 5000 laser pulses

During laser irradiation, the electrical characteristics of the chamber were changed to an environment with better reduction. Referring to (c) of FIG. 3, 5% forming gas (5% H ₂ / Ar) was flowed into the chamber instead of Ar gas. When the initial voltage was applied in sweep form (0V → 7V → 0V), reset occurred at 0.88V and the current dropped from 853uA to 5.2uA. In the process of voltage application, the current increase phenomenon (57uA → 1mA) was observed again at 6.23 V. And while the voltage is reduced back to 0V, the holding process of the selection device (from 1mA → 22uA) occurs at 1.72V. In addition, the IMT-based selector characteristic repeats on at an additional bias sweep (0V → 7V → 0V), at a threshold voltage (V _TH ) of 1.98V, and at a holding voltage of 1.73V (V _H ). Appeared.

This result is expected to increase the amount of oxygen vacancy or partially NbO ₂ phases formed in the film compared to the second embodiment because the annealing was performed using a laser in a reducing environment. In addition, according as a voltage is applied, and with the growth on the NbO ₂ generated in the conventional joule heating caused by the electric field it can be formed on the additional NbO _2. As a result, the characteristics of the E-IMT-based selection device appear from the second voltage application.

Fourth embodiment: applying 5% forming gas atmosphere and 10000 laser pulses

Referring to (d) of FIG. 3, when the number of laser irradiation pulses is increased from 5000 pulses to 10000 pulses while maintaining the same process atmosphere, laser intensity, and the like, the forming process of the selection device is performed at 4.7V when the initial voltage is applied. Can be observed. In addition, when the voltage was repeatedly applied (0 V → 7 V → 0 V), the electrical characteristics of the selection device turned on at 2.6 V (V _TH ) and off at 2.24 V (V _H ) were observed. Subsequently, the characteristics of the selective device, which exhibits the IMT phenomenon due to the electric field, were observed repeatedly during additional bias sweep. The selectivity (I _on / I _off ratio) of this selector was ~ 105 times.

In the fourth embodiment, a sufficient number of NbO ₂ clusters are formed in the NbO _x film due to the increased laser pulse compared to the process of the third embodiment. In addition, the current flow through the cluster may be better due to the increase in size of the cluster and the formation of additional NbO ₂ clusters by the forming process that occurs when the initial voltage is applied, and the Joule heating generated by the electric field may express IMT. If it is high enough, the E-IMT phenomenon is shown, and thus the characteristics of the NbO ₂ based selection device can be confirmed.

On the other hand, referring to Figure 3 (e), it can be seen that in the additional DC endurance test (endurance test) results that the device having the endurance up to 1000 times with a uniform selectivity up to 100 cycles. NbO ₂ based selectors manufactured by laser irradiation in the DC endurance results boils higher selectivity and endurance than NbO ₂ based selectors made by reducing or increasing post-treatment of conventional Nb ₂ O ₅ sputtering targets Or better.

NbO by laser irradiation _x  Structure Analysis of Devices

In the laser irradiation process, structural analysis was performed by using 3D beam line (10KeV, x-ray diffraction scattering) of the Pohang Accelerator Laboratory to confirm the effect of pulse repetition number and laser irradiation environment on the NbO _x image. NbO _x during measurement XRD analysis (GIXRD or GID) was performed in grazing incident angle mode of 0.3 ^o to obtain all the surface information generated in the device.

First, structural analysis was performed by increasing the pulse repetition frequency of the pulsed laser at 1.8W energy and 5% forming gas atmosphere. Referring to FIG. 4A, diffraction picks other than the (111) plane and the (200) plane of Pt are not detected in the Nb ₂ O ₅ device (Pt / Nb ₂ O ₅ / Pt) without laser irradiation. Did. Pristine as-grown Nb ₂ O ₅ It can be seen that no crystal phase was formed in the film. As the number of laser irradiation pulses is gradually increased to 5000 times and 10,000 times, NbO _x film picks are detected. In the case of film irradiated with 5000 lasers, q _z is 1.6A ^-1 and 2.02A ^-1 , respectively. -Nb ₂ O ₅ Diffraction peaks corresponding to (001) and (131) planes of (orthorhombic phase, Pbam space group) were detected. And a diffraction peak corresponding to the (400) plane of t-NbO ₂ was detected at 1.86A- ¹ . For the sample irradiated with 10000 laser pulses, the diffraction peaks corresponding to the (001) and (131) planes of O-Nb ₂ O ₅ are reduced while the diffraction peaks on the (400) plane of t-NbO ₂ are much lower. You can see a big increase. That is, in the environment of 5% forming gas, as the number of laser irradiation pulses increases, the amount of NbO ₂ distributed in the NbO _x film increases.

Next, referring to FIG. 4 (b), the gas pulse flowing into the chamber after changing the repetition rate of the laser pulse to 10000 pulses is changed to an environment in which reduction can be well performed (Ar gas → 5% forming). The process of changing the phase in the NbO _x film was confirmed. First, after forming the Ar gas atmosphere when given away by a laser beam of 000 pulses, O-Nb ₂ O ₅ (001), diffraction peak of the plane (131) appears most significantly, most film O-Nb ₂ O ₅ It was confirmed that the phase consists of. In addition, t-NbO seen that the (400) diffraction of the _second pick very weakly detected in quite a bit of t-NbO ₂ can check the formed within the film. When the number of pulse repetitions was maintained at 10000 pulses and the laser irradiation environment was changed to 5% forming gas under Ar gas atmosphere, the (400) peak of t-NbO ₂ was greatly increased while that of O-Nb ₂ O ₅ (001 ), (131) picks are much reduced. Based on the above results, it can be seen that when irradiating enough laser pulses, the reduction reaction in the NbO _x film is much more accelerated and the NbO ₂ phase is increased as the change to the environment where the reduction reaction can occur well.

NbO _x due to laser irradiation In order to directly analyze the crystallization and phase of the film, the NbO _x element cross-section formed inside the hole was cut using FIB, and cross-section was performed by using a spherical aberration correction transmission electron microscope (Cs-TEM). First, referring to FIG. 4 (c), it can be seen that no crystal phase is formed in the Nb ₂ O ₅ film in the cross section of the Nb ₂ O ₅ device not subjected to any laser irradiation. The FFT (Fast Fourier Transform) proved to be a complete amorphous state with no crystal phase formed. However, referring to (d) of FIG. 4, when 5000 pulses of a laser having 1.8 W energy is applied in a 5% forming gas atmosphere, a sufficient crystal phase is formed, unlike the previous device (the device that has not undergone the laser irradiation process). Was confirmed. In the NbO _x film, the interphase distance between the crystalline phase corresponding to 0.39 nm and the crystalline phase corresponding to 0.34 nm is mixed. The distances correspond to the interplanar distance corresponding to (001) of O-Nb ₂ O ₅ and t-NbO, respectively. _The interplanar distance corresponding to (400) of ₂ . In this experiment, the results of XRD and the actual imaging of the cross section show that the NbO ₂ phase was formed in the film by laser irradiation.

NbO by laser irradiation _x  Change of valence of cation and anion of film

X-ray photoelectron spectroscopy (XPS) analysis was performed to analyze the valence of Nb cations and O anions according to the change of process environment and pulse number during laser irradiation.

FIG. 5 shows the result of fitting the XPS spectra of 3d of Nb and 1s of O to each peak. Binding energy for the XPS spectra of Nb ^{5 +} ₅ of 3d _{/ 2} and the Nb ^{4 +} 3d _5/2 are each 207.8 eV, 206 eV.

5 (a) shows the change of XPS spectrum of Nb with increasing laser pulse repetition rate. When irradiated with 1000 pulses of laser, the Nb ^{5 +} spectrum at 207.8eV occupied most of the entire Nb 3d spectrum, and the slightly reduced Nb phase Nb ^{γ +} (4 <γ <5) was found to be very small. . From 5% forming gas atmosphere according to Sikkim 5000 times the repetition frequency of pulse laser having energy of 1.8W, increased 000 times the spectrum of Nb ^{+ 5} is reduced spectrum of Nb ^{4 +} 3d _5/2 appears at 206 eV is more Increases. The binding energy of the O 1s spectrum is 530.8 eV for O-Nb ^{5 +} and 531.03 eV for O-Nb ^{4 +} . Referring to FIG. 6A, as the laser repetition rate is increased from 1000 pulses to 10000 pulses, the binding energy represented by the Nb-O spectrum is increased from 530.83 eV to 530.96 eV.

Subsequently, (b) of FIG. 5 shows Nb 3d when an atmosphere in which reduction is accelerated gradually to Ar → 1% forming gas → 5% forming gas is maintained while maintaining the laser power at 1.8 W and the repetition rate at 5000 pulses. Shows changes in the XPS spectrum. When the gas that determines the process environment is more easily reduced from Ar to 1% forming gas and 5% forming gas, the pick of Nb ^{4 +} in the entire spectrum gradually increases. In particular, there is a clear increase in pick when changing from 1% forming gas to 5% forming gas. Referring to (b) of FIG. 6, when the O 1s spectrum is changed, the binding energy of O-Nb is increased from 530.91eV to 530.96eV as an environment in which reduction is accelerated to 5% forming gas is formed from Ar gas. do.

Meanwhile, Referring to FIG. (C) of 5, Nb ^{4 +} are based on each area of the Nb ^{4 +} and Nb ^{5 +} spectrum in order to quantitatively determine the rate at which the charge across the spectrum, Nb ^{4 +} is compared to the total area The area occupied is expressed as a percentage. First, as the irradiation repetition rate increases to 1000 pulses, 5000 pulses, and 10000 pulses in the atmosphere of 5% forming gas, the proportion of Nb ⁴⁺ gradually increases to 13.82%, 34.90%, and 40.95%. In addition, if the laser repetition rate is fixed at 5000 pulses and the irradiation environment is used as a variable, an atmosphere of better reduction from Ar 1% forming gas to 5% forming gas is formed. Nb ^{4 +} accounts for 19.86% 22.57% → 34.90%. To increase. Similar trends (27.71% 30.81% → 40.95%) are observed when 10000 pulses are applied.

In addition, information on non-lattice oxygen can be found in the O 1s spectrum. Non-lattice oxygen generally means the formation of oxygen vacancy. Referring to (d) of FIG. 5, the spectrum of non-lattice oxygen in the O 1s full spectrum is expressed by the percentage of the area occupied by the non-lattice oxygen in the entire O 1s spectra in the same manner as in the case of Nb ^{4 +} . . As the laser irradiation repetition rate was increased from 1000 pulses to 5000 pulses and 10,000 pulses, the content of non-lattice oxygen increased from 18.33% to 26.30% → 23.56 and then decreased. In addition, when the pulse number was fixed to 10000 pulses and the laser irradiation environment was changed from Ar 1% forming gas to 5% forming gas, the percentage of non-lattice oxygen changed from 24.73% to 29.01% to 23.56%. That is, as the laser irradiation process environment is changed, oxygen vacancy increases and oxygen vacancy decreases again when an environment in which reduction is accelerated is formed.

In annealing via laser irradiation, the production of Nb ^{4 +} ions is associated with the formation of oxygen vacancy. In practice, the formation of Nb ^{4 + and} the formation of oxygen vacancy seem to be proportional in the examples of various existing experiments (the formation of Nb ^{4 +} oxygen vacancy). This is because, in laser irradiated Nb ₂ O _{5 -δ} film, the generated oxygen vacancy acts as a donor (V _O ²⁺ ) to provide additional electrons to the entire film, resulting in increased conductivity. However, when a very reducing atmosphere is formed, the interaction between H ₂ and Nb ₂ O ₅ increases during laser irradiation, and as a result, electrons generated by oxygen vacancy (2e ⁻ generated in V _O ²⁺ ) become Nb. ^{5 +} ions are reduced to Nb ^{4 +} . Increasing the number of pulses from 5000 pulses to 10000 pulses while maintaining the process environment at 5% forming gas accelerates this phenomenon because more thermal energy is applied to the NbO _x film. This is in good agreement with the experimental results.The comparison of Nb ^{4 +} and non-lattice oxygen production in XPS analysis shows that Nb ^{4 +} and non-oxygen lattice when the process environment changes from Ar to 1% forming gas. Although they increased by 3.1% and 5.3%, respectively, a 5% forming gas atmosphere, a very reducing atmosphere, increased Nb ^{4 + by} 10.1% but decreased non-lattice oxygen by 5.4%. This is because two electrons are generated in one oxygen vacancy (V _O ²⁺ ), which allows two Nb ^{5 +} ions to be reduced to Nb ^{4 +} . Increasing the number of pulses from 5000 pulses to 10000 pulses in a 5% forming gas environment shows a similar trend: the amount of Nb ⁴⁺ increases by 6.04% but the amount of non-lattice oxygen decreases by 2.8%.

Laser irradiation; less sensitive method at growth condition

Formation during deposition while maintaining the power, deposition time and pressure of the rf-generator of the sputtering system to demonstrate that fabricating NbO _x devices using pulsed laser irradiation can be a less sensitive method for the deposition environment. The experiments were carried out by changing the injection gas which had a significant effect on the oxidized and reduced states. That is, NbO _x film was deposited in three environments, respectively Ar / O ₂ (0.5sccm), Ar, Ar / 5% H ₂ (10sccm). The three pristine NbO _x films thus produced were irradiated with a laser of 1.8 W and 10,000 pulses in a 5% forming gas environment. Then, after depositing the upper Pt electrode, the electrical characteristics were compared.

8 (a) shows a phenomenon appearing in the DC IV curve of three devices. As a result of the electrical property measurement, the characteristics of the IMT-based selection device appear in all three devices having different deposition environments. In the case of NbO _x devices that have undergone laser irradiation after deposition in an Ar / O ₂ environment, a reset phenomenon (LRS → HRS) occurs at 0.5V when the initial voltage is applied, and the resistance decreases again at 6.4V, followed by an additional bias sweep. The E-IMT based selector is shown to be on at 2.35V (V _TH ) and off at 1.94V (V _H ). NbO _x devices that undergo laser irradiation after deposition in an Ar / 5% H ₂ environment form at 4.7V, and are turned on at 2.8V (V _TH ) and off at 2.2V (V _H ) in a continuous bias sweep. The characteristics of the selector are shown. On the other hand, Figure 7 (a) summarizes each IV curve. The selectivity ratios of the three devices deposited on Ar / O ₂ , Ar, and Ar / H ₂ , respectively, are ≧ 230 times, ≥ 105 times, and ≥ 66 times. In addition, when the current (I _off ) in the off-state (~ 1V) is compared, the higher the off-state, the higher the deposition in the reducing atmosphere of ~ 693nA, ~ 1.34uA, and ~ 4.39uA. If O ₂ gas is present during the deposition process, oxygen vacancy is formed to a minimum when NbO _x film is synthesized to form a film that almost fits the stoichiometry of Nb ₂ O ₅ , and when only Ar gas is injected, some oxygen vacancy is formed in the film. Could be formed. In addition, since the film synthesized in the reduction atmosphere (Ar / H ₂ ) may undergo reduction along with sufficient oxygen vacancy formation during the deposition process, a film containing NbO ₂ may be formed during the deposition process. Further reduction and crystallinity are additionally given during subsequent laser irradiation, so that the device deposited in the reducing atmosphere has a smaller selectivity and higher off-current.

NbO _x devices having different thicknesses may be subjected to the same laser irradiation, and thus, characteristics of the selection device may be realized. To prove this, pristine NbO _x films with different thicknesses were prepared by varying the deposition time to 166W of energy, Ar gas, 10 mTorr, 20 minutes, 23 minutes, and 25 minutes at room temperature. Each device is 40nm, 45nm and 50nm thick. Thereafter, the laser was irradiated with 1.8 W and 10000 pulses in a 5% forming gas environment, and the upper Pt electrode was deposited at 40 nm to check electrical characteristics. As a result, referring to FIG. , threshold voltage, hold voltage, all voltages were increased. Referring to FIG. 7B, that is, as the deposition time of the NbO _x film was increased to 20 minutes, 23 minutes, and 25 minutes, the forming voltage was increased to 4.7V, 5.8V, and 6.5V. The threshold voltage also increased to 2.35V, 3.7V, and 4.1V. The reason for this is that due to the increase in thickness, V _F and V _TH increase due to the temperature rise in much more NbO _x layers in order for further crystallization by Iule heating and IMT to occur. In addition, when comparing the off-state current at 1.5V, the thickest device, that is, the NbO _x film deposited for 25 minutes, had the lowest off-current (~ 1.8uA). This is because the amount of NbO ₂ phase and the degree of crystallization generated through the same laser irradiation are limited. Therefore, the thicker the thickness, the more the non-crystallized part exists in the entire film, and this result is because the proportion of NbO ₂ in the overall phase is small. The above experiments demonstrate that even though the thickness is not uniform, the NbO _x selector can be effectively manufactured through the same laser irradiation process.

On the other hand, the forming process that appears when the initial voltage is applied to the selection device depends on the degree of crystallization of the device. The initial voltage is applied to make the crystal that the IMT can occur is excessively higher than the threshold voltage is called forming process. The voltage at the point where the forming process is completed and the current rises sharply is called forming voltage. NbO _x devices made by laser irradiation (annealing) process were used to increase the number of laser pulses to promote crystallization regardless of the film growth process. Referring to (c) of FIG. 7, the NbO ₂ device subjected to 5000 pulses of laser irradiation has a Vf of about 7 V, but when the number of laser pulses is doubled from 5000 pulses to 10000 pulses, crystallization is promoted to form a forming voltage of 4.5 V. (Standard deviation 10%) can be reduced. This allows the heat generated by increasing the number of laser pulses to last longer, which leads to further crystallization of the NbO _x device, thereby reducing the forming voltage.

As described above, it was confirmed that the device manufactured through the laser irradiation (annealing) process by changing the deposition environment, controlling the thickness, and forming voltage did not depend on the pristine state of the film. Therefore, it was confirmed that the manufacturing method according to the present invention may be a less sensitive manufacturing method than the existing manufacturing method.

Features, structures, effects, and the like described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to such combinations and modifications should be construed as being included in the scope of the present invention.

In addition, the above description has been made with reference to the embodiments, which are merely exemplary and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains will be illustrated above without departing from the essential characteristics of the present embodiment. It will be understood that various modifications and applications are not possible. For example, each component specifically shown in the embodiments may be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

Claims (9)

Depositing an Nb ₂ O ₅ film on the patterned substrate with the lower Pt electrode exposed; And
The method of manufacturing a selection device comprising the step of irradiating a laser to the Nb ₂ O ₅ film.
The method of claim 1,
In the step of irradiating the laser, the method of manufacturing a selection device, characterized in that for irradiating the laser repetition rate 3000 pulses to 10,000 pulses with a laser energy of 1.8 W.
The method of claim 1,
The method of manufacturing a selection device, characterized in that the step of irradiating the laser is carried out in a reducing atmosphere.
The method of claim 1,
In the step of irradiating the laser manufacturing method of the selection device, characterized in that carried out in an Ar gas atmosphere or 1% to 5% H ₂ forming gas atmosphere.
The method of claim 1,
In the step of irradiating the laser,
Method of manufacturing a selection device characterized in that for irradiating a KrF (a krypton fluoride) pulsed laser.
The method of claim 1,
And said patterned substrate comprises a Si substrate, a SiO ₂ layer, a TiN layer and a lower Pt electrode.
The method of claim 1,
The patterned substrate is a method of manufacturing a selection device characterized in that it comprises a hole of 200 nm to 300 nm.
The method of claim 1,
And after the irradiating the laser, forming the upper Pt electrode by sputtering.
A selection device manufactured by the manufacturing method according to any one of claims 1 to 8.

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