KR20080011956A - Preparation of iron oxide thin films by chemical vapor deposition for non-volatile resistance random access memory devices - Google Patents

Abstract

A method for fabricating an iron oxide thin film for a non-volatile ReRAM(resistance random access memory) device by a chemical deposition method is provided to embody an excellent resistance switching phenomenon by fabricating an iron oxide thin film having low surface roughness, a uniform growth surface and no carbon contamination. A substrate is introduced into a chemical deposition reactor. A Fe source and an O source are supplied to fabricate a FexOy thin film. The Fe source and the O source are supplied by a MOCVD(metal organic chemical vapor deposition) method for simultaneously supplying the Fe source and the O source or by an ALD(atomic layer deposition) method for alternately supplying the Fe source and the O source.

Description

Production method of iron oxide thin film for nonvolatile REMA element by chemical vapor deposition {PREPARATION OF IRON OXIDE THIN FILMS BY CHEMICAL VAPOR DEPOSITION FOR NON-VOLATILE RESISTANCE RANDOM ACCESS MEMORY DEVICES}

1 is an X-ray photoelectron spectroscopic spectrum of an iron oxide thin film according to the present invention,

2 is an X-ray diffraction pattern of iron oxide over temperature variations of the substrate,

3 is a schematic diagram of a capacitor structure of an electrode-iron oxide-electrode prepared using an iron oxide thin film deposited by a metal organic chemical vapor deposition method,

       4 is a current-voltage (I-V) measurement result of the resistance conversion phenomenon of iron oxide according to the present invention.

The present invention relates to a method for manufacturing an iron oxide thin film, and more specifically, using a iron source and an oxygen source (metal organic chemical vapor deposition (MOCVD), atomic layer deposition method such as chemical vapor deposition method such as ReRAM ( resistance random access memory) A method of manufacturing an iron oxide thin film for a device, and a method of manufacturing a nonvolatile ReRAM device using the same.

Iron oxide (Fe _x O _y ) has various applications depending on the crystal structure. Generally known Fe ₂ O ₃ is a hematite structure of the α-type and a maghematite structure of the γ-type, the application research to the hydrocarbon gas sensor, magnetic recording disk application so far is active. In addition, α-Fe ₂ O ₃ has been studied a lot of catalysts, attracting attention as an important material for solar energy conversion device because of low cost and high stability.

Recently, as the research on the next generation nonvolatile memory device is active, many researches are applied to the nonvolatile memory device using the resistance switching phenomena of various metal oxides. This resistance conversion phenomenon has been known since the 1960s in nickel oxide (NiO), titania (TiO ₂ ), zirconia (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), and chromium-doped strontium zirconate (Cr-doped SrZrO _3). (JF Gibbons et al., "Switching properties of thin NiO films," Solid-State Electron. , 1964 , 7 , 785-790; WR Hiatt et al. , "Bistable switching on niobium oxide diodes," Appl. Phys. Lett. ., 1965, 6, 106-108; F. Argall, "switching phenomena in titanium oxide thin films," Solid-State Electron, 1968, 11, 535-541;. KC Park , etc., "Bistable switching in Zr-ZrO 2 -Au junctions, " J. Non-Cryst. Solids , 1970 , 2 , 284-291; A. Beck et al.," Reproducible switching effect in thin oxide films for memory applications, " Appl. Phys. Lett. , 2000 , 77 , 139-141).

In the research of next-generation non-volatile memory devices that want to use various non-volatile characteristics of materials in memory devices, resistance RAM (ReRAM) using resistance switching or conductivity switching of metal oxide thin films Compared with other nonvolatile memory devices, the device structure is relatively simple and the manufacturing process is relatively simple. For the development of nonvolatile ReRAM devices, as mentioned above, the implementation of excellent resistance conversion in the basic capacitor structure of metal-oxide-metal (MOM) is the most important factor. In fact, to achieve high density deviceization, the difference between the large resistance (or conductivity) of the on- and off-states to achieve a high signal-to-noise (SN) ratio (high flash rate, high on / off ratio, low on-state maximum current value, low reset voltage to lower the drive voltage of the entire device, and stable conversion of external variables such as temperature. Therefore, finding an excellent material for satisfying the conditions of deviceization can be said to be one of the most important factors, and is recognized as an important candidate to which a transition metal oxide is applicable.

The method of coating the iron oxide thin film on a substrate may be classified into physical vapor deposition methods such as sputtering, chemical vapor deposition such as metal organic chemical vapor deposition (MOCVD), and atomic layer deposition. There are several reports on the deposition of iron oxide by the chemical method, but there is no research to apply it to the ReRAM device through the implementation of the resistance conversion phenomenon of the deposited iron oxide and the manufacture of the MOM structure.

In general, in the physical vapor deposition method, the surface of the growing thin film is rough, it is difficult to grow a uniform thin film on a large-area substrate or a three-dimensional substrate, and it is difficult to manufacture a thin film thinner than the chemical vapor deposition method. On the other hand, in the chemical vapor deposition method, compared with the physical vapor deposition method, the surface roughness of the thin film is small and it is easy to grow a relatively uniform film on a large area substrate. Therefore, the present invention is to fabricate a high quality iron oxide thin film MOM structure by using a metal organic chemical vapor deposition method that can overcome the shortcomings of the physical vapor deposition method and to implement an excellent resistance conversion phenomenon to be applied to the next-generation nonvolatile ReRAM device.

Several studies have been reported on the application of metal organic chemical vapor deposition to iron oxide deposition (T. Maruyama et al., "Iron-iron oxide composite thin films prepared by chemical vapor deposition from iron pentacarbonyl," Thin Solid Films , 1998 , 333, 203-206; B. Pal et al., "Preparation of iron oxide thin film by metal organic deposition from Fe (III) -acetylacetonate: a study of photocatalytic properties," Thin Solid Films , 2000 , 379, 83-88 As such, there have been no examples of the thin film grown by chemical vapor deposition in the fabrication of a MOM structure for the resistance conversion phenomenon and its application to a ReRAM device.

Meanwhile, the iron compounds applied to the conventional metal organic chemical vapor deposition method are Fe (CO) ₅ (CO = carbonyl), Fe (acac) ₃ (acac = acetylacetonato), Fe (thd) ₃ (thd = 2,2, Some 6,6-tetramethyl-3,5-heptanedionato), [Fe (O ^t Bu) ₃ ] ₂ (O ^t Bu = butoxide) compounds are known (T. Maruyama et al., “Iron -iron oxide composite thin films prepared by chemical vapor deposition from iron pentacarbonyl, " Thin Solid Films , 1998 , 333, 203-206]; B. Pal et al.," Preparation of iron oxide thin film by metal organic deposition from Fe (Ⅲ) -acetylacetonate: a study of photocatalytic properties, " Thin Solid Films , 2000 , 379, 83-88).

On the other hand, the present inventors have filed an iron aminoalkoxide compound represented by Fe [OCR ¹ R ² (CH ₂ ) _m NR ³ R ⁴ ] ₃ , which is useful as a precursor of iron oxide, to Korean Patent Application No. 2006-0006743.

The inventors have found that the iron oxide thin film prepared by the chemical vapor deposition method using the above-described iron compound as an iron source has an excellent resistance conversion phenomenon, and completed the present invention. In particular, a high-quality iron oxide thin film was chemically deposited using an iron aminoalkoxide compound represented by Fe [OCR ¹ R ² (CH ₂ ) _m NR ³ R ⁴ ] ₃ , which is useful as a precursor of iron oxide among the above-described iron compounds. It is intended to be used as a next-generation nonvolatile ReRAM device by manufacturing and implementing excellent resistance conversion phenomenon.

Therefore, an object of the present invention by using the advantages of the chemical vapor deposition method to produce an iron oxide thin film having a low surface roughness, uniform growth surface, free of carbon contamination and good quality to realize excellent resistance conversion phenomenon and to provide a non-volatile ReRAM device Another object of the present invention is to provide a method for manufacturing the iron oxide thin film by chemical vapor deposition in the manufacture of a ReRAM device having a metal-iron oxide-electrode structure.

In addition, the present invention uses the iron amino alkoxide as an iron precursor with an oxygen source to deposit a high-quality iron oxide thin film by chemical vapor deposition, and to manufacture a MOM device structure to implement an excellent resistance conversion phenomenon, for a nonvolatile ReRAM device It is an object of the present invention to provide a method for producing an iron oxide thin film.

Another object of the present invention is to provide a method of manufacturing a nonvolatile ReRAM device using the method of manufacturing the iron oxide thin film.

In order to achieve the above technical problem, the method for manufacturing an iron oxide thin film for a nonvolatile ReRAM device of the present invention is characterized in that the iron oxide thin film is formed by supplying an iron source and an oxygen source to a chemical vapor deposition reactor on a substrate. The chemical vapor deposition method may use a metal organic chemical vapor deposition (MOCVD) to supply an iron source and an oxygen source at the same time, or may use an atomic layer deposition method (ALD) to alternately supply an iron source and an oxygen source.

In addition, the manufacturing method of the nonvolatile ReRAM device according to the present invention is a metal organic chemical vapor deposition method (metal organic chemical vapor deposition) of the iron oxide thin film in the manufacture of a ReRAM device consisting of a capacitor structure of a metal-iron oxide (Fe _x O _y ) -electrode It is characterized by manufacturing by chemical vapor deposition such as organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD).

Hereinafter, the present invention will be described in detail.

The present invention provides a method for producing an iron oxide thin film for a nonvolatile ReRAM device comprising the following steps.

Introducing a substrate into a chemical vapor deposition reactor; And

Supplying an iron (Fe) source and an oxygen (O) source to produce an iron oxide (Fe _x O _y ) thin film on a substrate.

Metal organic chemical vapor deposition (MOCVD) method of the iron oxide thin film manufacturing method according to the present invention, after introducing the substrate into the chemical vapor deposition reactor, the iron (Fe) source and oxygen (O) while maintaining the temperature of the substrate constant A circle is fed to the substrate to form an iron oxide thin film. When the amount of oxygen source is changed in order to cause the iron oxide thin film to react at a constant pressure, an inert gas such as argon is used to adjust the working pressure of the reactor and to deposit the thin film.

A method of atomic layer deposition (ALD) in the method for producing an iron oxide thin film according to the present invention is to form an iron oxide thin film by alternately supplying an iron source and an oxygen source after introducing a substrate into a chemical vapor deposition reactor, Specifically, the iron source is first supplied to adsorb the iron source on the substrate, the unreacted iron source and the reaction by-products are removed from the chemical vapor deposition reactor, the oxygen source is supplied to the chemical vapor deposition reactor, and the iron source adsorbs the substrate. Adsorbing an oxygen source above to cause an oxidation reaction, and removing unreacted oxygen source and reaction by-products from the atomic layer deposition reactor.

In the present invention, there is no need to limit the iron source for producing the iron oxide thin film, Fe (CO) ₅ (CO = carbonyl), Fe (acac) ₃ (acac = acetylacetonato), Fe (thd) Compounds such as ₃ (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato), [Fe (O ^t Bu) ₃ ] ₂ (O ^t Bu = t-butoxide) alone or It can be used in mixture, iron amino alkoxide can also be used, It is more preferable to use the iron amino alkoxide of following formula (1).

[Formula 1]

Fe [OCR ' ₂ (CH ₂ ) _m NR ₂ ] ₃

[Wherein m is 1 to 3 and R and R 'are independently C1 to C5 linear or branched alkyl, with or without fluorine independently of one another.]

In the compound of Formula 1, m is preferably 1 or 2, and R and R 'are preferably selected from CH ₃ , CF ₃ , C ₂ H ₅ , CH (CH ₃ ) ₂ and C (CH ₃ ) ₃ . Do. In particular, when R is a methyl group, the distillation temperature among the known trivalent iron alkoxide compounds is 120 ° C. (10 ⁻² torr), which is a liquid having excellent volatility.

The temperature of the iron source supplied to the chemical vapor deposition process is preferably 0 ℃ to 100 ℃, when the iron oxide thin film using the iron amino alkoxide of the formula (1) is preferably 60 ℃ to 100 ℃.

In addition, water, oxygen (O ₂ ), ozone, or oxygen plasma may be used as the oxygen source, and using oxygen (O ₂ ) as the oxygen source may be easily applied to the system.

In the method of the present invention, a silicon (Si) wafer, a germanium (Ge) wafer, a silicon carbide (SiC) wafer, a silicon oxide (SiO ₂ ), and a glass substrate may be used as the substrate, and platinum (Pt) and iridium on the substrate. Metals such as (Ir), gold (Au), ruthenium (Ru), or metal oxide electrodes such as indium tin oxide (ITO) and ruthenium dioxide (RuO ₂ ) may be used, and the temperature of the substrate may be 100 to It can be maintained at 400 ℃, more preferably 200 to 270 ℃ to form an iron oxide thin film excellent in properties. If the temperature of the substrate is less than 100 ℃ there is a problem that the deposition is not made, when the temperature of the substrate exceeds 400 ℃ the roughness of the thin film is severe.

The present invention provides a method for manufacturing a ReRAM device comprising an iron oxide thin film manufactured according to the above-described method for manufacturing an iron oxide thin film.

The ReRAM device according to the present invention includes a structure of an electrode-iron oxide-electrode, and the iron oxide is manufactured by a method of manufacturing an iron oxide thin film using a chemical vapor deposition method such as the MOCVD method or the ALD method as described above. It is done.

Electrode formed on the iron oxide thin film to manufacture a ReRAM device consisting of an electrode-iron oxide-electrode structure [metal-oxide-metal (MOM)] is platinum (Pt), iridium (Ir), gold (Au), Ruthenium (Ru), indium tin oxide (rudium), ruthenium oxide (RuO ₂ ) is selected from, and the formation of the electrode by a conventional method in the art, such as a sputtering method using an electrode mask.

The present invention will be described in more detail with reference to the following examples. However, the embodiment illustrating the process of forming the iron oxide thin film by the following metal organic chemical vapor deposition method is only one embodiment of the present invention, and the claims of the present invention are not limited thereto.

Preparation Example 1 Synthesis of Tris (dimethylamino-2-methyl-2-propoxy) iron (III) [Fe (dmamp) ₃ ]

In a 100 mL Schlenk flask, 1 g (6.16 mmol) of anhydrous FeCl ₃ and 2.57 g (18.5 mmol) of Na (dmamp) (dmamp = dimethylamino-2-methyl-2-propoxy) were respectively added to tetrahydrofuran (THF). After dissolving in 40 mL, the two solutions were mixed and stirred at room temperature for 3 days. After completion of the reaction, the resultant was filtered to remove NaCl and the filtrate was dried in vacuo to give the title compound as a dark brown liquid. Tris (dimethylamino-2-methyl-2-propoxy) iron (III), the title compound obtained above, was purified by vacuum distillation at 120 ° C / 10 ^-2 torr.

Elemental Analysis C ₁₈ H ₄₂ N ₃ O ₃ Fe {calculated (calculated)}: C, 53.46 (50.10); H, 10.47 (10.04); N, 10.39 (9.90).

FT-IR (cm ⁻¹ , KBr pellet): υ (MO) 430.

Mass spectrometry MS (EI, 70 eV), m / z (ion, relative intensity): 288 ([Fe (dmamp) ₂ ] ⁺ , 30), 230 ([Fe (dmamp) ₂ -CH ₃ COCH ₃ ] ⁺ , 23 ), 172 ([Fe (dmamp)] ⁺ , 10), 58 ([CH ₃ COCH ₃ ], 100).

Example 1

The silicon and platinum / silicon substrates to form the iron oxide thin film were sequentially washed with acetone, ethanol and deionized water, and then mounted in a chemical vapor deposition reactor, and the reactor was evacuated with an exhaust pump. There are dozens of native oxide layers on the surface of the silicon substrate and the platinum / silicon substrate provides a clean platinum surface. The temperature of the substrate was adjusted to 250 ° C., and the temperature of the vessel containing Fe (dmamp) ₃ of Production Example 1 as the iron source was maintained at 60 ° C. Under these conditions, open the valve on the iron source supply line and use 20 sccm of argon gas as the carrier gas. As an oxygen source, 20 sccm of oxygen gas was used.

The reactor substrate temperature, the iron source, and the temperature of the iron source vessel were kept constant and the deposition reaction was performed. At this time, the working pressure of the reactor was adjusted to 930 mTorr.

FIG. 1 is an X-ray photoelectron spectroscopy spectrum measured after cleaning the surface by argon ion sputtering for 5 minutes to remove carbon contamination on the surface of the thin film formed in Example 1 with a thickness of 600 mm 3. In this spectrum, only the characteristic optoelectronic peaks of iron and oxygen can be observed. In particular, near 284 eV, there are few C 1s peaks indicating carbon contamination. Contamination of carbon adversely affects the characteristics of the iron oxide thin film, and from this, it was confirmed that the iron oxide thin film having almost no carbon contamination was produced under the conditions of Example 1.

Example 2

Under the same conditions as in Example 1, a thin film was prepared at 190, 220, 270, and 300 ° C. only at the process temperature. The deposition time was fixed to 30 minutes by chemical vapor deposition. Figure 2 shows the X-ray diffraction pattern of the iron oxide thin film according to the temperature of the substrate, it can be seen that the peak intensity increases with increasing substrate temperature.

Example 3

In order to manufacture the MOM structure on the platinum / silicon substrate, a platinum electrode was coated on the iron oxide thin film by a sputtering method using a mask to implement the MOM structure as shown in FIG. 3. At this time, Fe (dmamp) ₃ was used as an iron source, and the thickness of the iron oxide film formed by chemical vapor deposition was about 60 nm. The resistance conversion phenomenon as shown in FIG. 4 was confirmed by analyzing the electrical characteristics of the MOM structure thus prepared. As a result, since the on / off ratio of the current is very large and the reset voltage is low, the iron oxide thin film manufactured by chemical vapor deposition is expected to be applied to the nonvolatile ReRAM device to exhibit excellent device characteristics.

As can be seen from the foregoing, the method of manufacturing the iron oxide thin film by the chemical vapor deposition according to the present invention has a very small surface roughness and a uniform thickness in a large-area thin film with a precise composition as compared with the conventional physical vapor deposition method. By producing a thin film and showing excellent resistance conversion phenomenon, the iron oxide thin film of the present invention is expected to be applied to the manufacture of nonvolatile ReRAM devices and exhibit excellent device characteristics.

Claims (11)

In the method for producing an iron oxide thin film on a substrate, Introducing a substrate into a chemical vapor deposition reactor; And Supplying an iron (Fe) source and an oxygen (O) source to produce an iron oxide (Fe _x O _y ) thin film; Method for producing an iron oxide thin film for a nonvolatile ReRAM device comprising a. In claim 1, The thin film manufacturing method is a metal organic chemical vapor deposition method (MOCVD) for supplying an iron source and an oxygen source at the same time, or an atomic layer deposition method (ALD) for supplying an iron source and an oxygen source alternately. Method for producing an oxide thin film. In claim 1, Fe (CO) ₅ (CO = carbonyl), Fe (acac) ₃ (acac = acetylacetonato), Fe (thd) ₃ (thd = 2,2,6,6-tetramethyl-3 , 5-heptanedionate) and [Fe (O ^t Bu) ₃ ] ₂ (O ^t Bu = t-butoxide) of at least one compound selected from the iron oxide thin film for non-volatile ReRAM device, characterized in that for use Manufacturing method. In claim 1, A method for producing an iron oxide thin film for a nonvolatile ReRAM device, characterized in that one or more compounds are selected from the iron aminoalkoxides of the general formula (1) as the iron source. [Formula 1] Fe [OCR ' ₂ (CH ₂ ) _m NR ₂ ] ₃ [Wherein m is 1 to 3 and R and R 'are independently C1 to C5 linear or branched alkyl, with or without fluorine independently of one another.] In claim 4, In Formula 1, m is 1 or 2, and R and R 'are independently selected from CH ₃ , CF ₃ , C ₂ H ₅ , CH (CH ₃ ) ₂ and C (CH ₃ ) ₃ . Method for producing iron oxide thin film for volatile ReRAM device. In claim 1, A method for producing an iron oxide thin film for a nonvolatile ReRAM device, characterized by using water, oxygen, ozone, or an oxygen plasma as an oxygen source. In claim 1, The substrate is a silicon (Si) wafer, germanium (Ge) wafer, silicon carbide (SiC) wafer, silicon oxide (SiO ₂ ) or a glass substrate manufacturing method of the iron oxide thin film for a nonvolatile ReRAM device, characterized in that. In claim 7, The substrate is characterized in that a thin film selected from platinum (Pt), iridium (Ir), gold (Au), ruthenium (Ru), indium tin oxide (ITO) or ruthenium dioxide (RuO ₂ ) is formed on the substrate. Method for producing iron oxide thin film for nonvolatile ReRAM device. In claim 7, A method for producing an iron oxide thin film for a nonvolatile ReRAM device, characterized in that the temperature of the substrate is maintained in the range of 100 to 400 ° C. In a method of manufacturing a ReRAM element comprising the structure of an electrode-iron oxide-electrode, 10. A method of manufacturing a nonvolatile ReRAM device, characterized in that the iron oxide thin film is produced by the method according to claims 1-9. In claim 10, Fabrication of non-volatile ReRAM device, characterized in that the electrode is selected from platinum (Pt), iridium (Ir), gold (Au), ruthenium (Ru), indium tin oxide or ruthenium dioxide (RuO ₂ ) Way.

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