KR101851275B1 - Method for depositing multiple metal system oxide thin film - Google Patents

Abstract

Conventionally, it has been difficult to deposit a composite film by ALD (Atomic Layer Deposition) method and to deposit a composite film having a constant composition and thickness of the polyatomic thin film. In order to solve this problem, the present invention proposes a method of pre-treating a reactor and a wafer to facilitate thin film deposition on a wafer before depositing the thin film by the ALD method. The method for depositing a multi-component metal oxide thin film according to the present invention includes: placing a wafer on a wafer block in a reactor; Subjecting the reactor and the wafer to pretreatment by supplying and purge oxygen-containing gas into the reactor; Forming a first metal oxide on the wafer by supplying and purge a first metal source into the reactor; Subjecting the reactor and the wafer to pretreatment by supplying and purge oxygen-containing gas into the reactor; And forming a second metal oxide on the oxide of the first metal by supplying a second metal source in the reactor and purge, reactant gas supply and purge, wherein the cycle is repeated at least once, Containing gas and the reactive gas only during the supply of the contained gas and the reactive gas, wherein the temperature of the pretreating step is a step of forming an oxide of the first metal and a step of forming an oxide of the second metal May be the same as the temperature of the step of forming the layer.

Description

[0001] The present invention relates to a method for depositing a multi-metal oxide thin film,

The invention, more particularly, SrRuO _3, LaNiO ₃ multi-element conductive metal oxide thin film deposition such as the method relates to the ALD (Atomic Layer Deposition) ALD multi-element thin film forming method capable of depositing a multi-element thin film using the method .

Currently, most of the materials used for DRAM, FRAM, and PRAM are binary materials such as SiO ₂ , Al ₂ O ₃ , and TiN having a composition of A _x B _y . These binary materials are deposited by CVD (Chemical Vapor Deposition) or sputter ) Method. ≪ / RTI > Recently, it has been required to increase the degree of integration of the semiconductor device and to further improve the electrical characteristics. Therefore, a ternary material having a composition of A _x B _y C _z such as Sr _x Ti _1-x O _y , Ti _x Al _{1 -x} N _y , Pb _w Zr _x Ti _y O _z , Br _w Sr _x Ti _y O ₃ , and the like. In many cases, a thin film is formed with a quaternary material having a composition of A _w B _x C _y D _z . However, when a ternary system or a quaternary system material is used, it is very difficult to form a thin film having a desired composition, and deposition is performed on a wafer depending mainly on a sputtering method.

In the sputtering method, an inert gas such as argon is injected into a vacuum chamber while a high voltage is applied to a target made of a ternary or quaternary material in order to generate argon ions in a plasma state. At this time, the argon ions are sputtered on the surface of the target, and the atoms of the target are removed from the surface of the target and stacked on the wafer. Such a sputtering method has an advantage of obtaining a thin film having high purity and constant composition with excellent adhesion to a wafer, but in manufacturing a highly integrated semiconductor device having a thickness of 100 nm or less, the step coverage is poor, And it is very difficult to obtain uniformity over the entire thin film, so there is a limit to the application for fine patterns.

The CVD method is a method in which various kinds of source gases coexist in the inside of a reactor to cause vapor phase reaction inside the reactor, thereby depositing a thin film on the wafer. However, such a CVD method also has a disadvantage in that when the step difference on the wafer is large, the step coverage is poor, and the composition is different according to the step inside the wafer, and there is a disadvantage that particles are liable to be generated .

For example, in a highly integrated and miniaturized semiconductor device, a lower electrode (or a storage electrode) of a capacitor may be formed in various solid structures such as a cylinder, a pin, and a concave structure in order to secure a capacitance of the capacitor. BST [(Ba, Sr) TiO ₃ ] and PZT [(Pb, Zr) TiO ₃ ] having a high-k or ferroelectric characteristic as a dielectric film of a capacitor. Oxide thin film is applied. Further, in the case to apply such an oxide thin film a lower electrode of a capacitor in terms of electrical properties / the upper electrode include platinum (Pt), ruthenium (Ru), iridium, conductive metal oxide such as SrRuO _3, LaNiO ₃ in addition to noble metals such as (Ir) Attempts have been made to use thin films.

Among the above-mentioned conductive metal oxide thin films, for example, in the CVD method of SrRuO ₃ , the decomposition temperatures (Sr source: at least 350 캜 and Ru source: at least 200 캜) of the Sr source and Ru source are very different. Therefore, in order to form a SrRuO ₃ thin film, a method for forming a thin film by a low temperature process is required, and recently, a method of forming the SrRuO ₃ thin film by an ALD method with excellent step coverage has been proposed.

The SrRuO ₃ thin film deposition method by the ALD method is a method of depositing a SrO thin film by loading a wafer in a reactor and then adsorbing the Sr source on the wafer and then oxidizing the Sr source by supplying an oxygen source, And then the Ru source is oxidized by supplying an oxygen source to deposit a RuO thin film to form a laminated SrO / RuO composite film.

However, since the incubation time of each source and the dependence on the underlying film are different, it is difficult to reproduce a thin film having a constant composition in this manner. In particular, the Ru source has a longer incubation time than the other sources, has a larger dependency on the underlying film, and is sensitive to the reactor conditions before deposition. For example, when a composite film of SrO / RuO is formed to form a SrRuO ₃ thin film as in the above example, when the O ₂ is used as an oxygen source, the RuO thin film hardly grows on the SrO thin film. In addition, SrO has a weak dependence on the underlying film, whereas RuO has a different film dependency such as Si, Ta ₂ O ₅ and TEOS and BST. In this case, it is very difficult to deposit SrRuO ₃ having a constant composition due to the difference in the deposition rate of SrO and RuO 3 depending on the characteristics of each source. In the above example, when O ₂ is used as the oxygen source, The reproducibility is poor.

Therefore, a multi-component metal oxide thin film such as Ru-containing SrRuO ₃ can be reproduced uniformly, and a method capable of performing a low temperature process with high step coverage is required.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a method capable of easily depositing a multi-component metal oxide thin film on a wafer and having a constant composition and excellent step coverage.

In order to achieve the above object, a method of depositing a multi-element metal oxide thin film according to the present invention comprises: placing a wafer on a wafer block in a reactor; Subjecting the reactor and the wafer to pretreatment by supplying and purge oxygen-containing gas into the reactor; Forming a first metal oxide on the wafer by supplying and purge a first metal source into the reactor; Subjecting the reactor and the wafer to pretreatment by supplying and purge oxygen-containing gas into the reactor; And forming a second metal oxide on the oxide of the first metal by supplying a second metal source in the reactor and purge, reactant gas supply and purge, wherein the cycle is repeated at least once, Containing gas and the reactive gas only during the supply of the contained gas and the reactive gas, wherein the temperature of the pretreating step is a step of forming an oxide of the first metal and a step of forming an oxide of the second metal Is formed.

The oxygen atom containing gas may be any one selected from oxygen, H ₂ O, and ozone, or an activated oxygen source selected from oxygen plasma and H ₂ O plasma, and the oxygen atom containing gas and the reactive gas may be the same.

In a preferred embodiment, any one of the first metal and the second metal is Ru, and a high frequency power is directly applied to the reactor during the supply of the oxygen atom containing gas and the reaction gas, Can be introduced into the reactor.

According to the present invention, in the deposition of the multi-layer metal oxide thin film by stacking the multi-layer composite film by the ALD method, the pretreatment of the reactor and the wafer is performed so as to facilitate film deposition on the wafer before each thin film is formed. Pretreatment with an oxygen atom-containing gas increases the adsorption efficiency of the metal source to the wiper and removes residual and deposited film components from the reactor, thereby making the next thin film in a state suitable for deposition. Accordingly, a film such as SrRuO ₃ can be deposited in a composition and thickness reproducibility.

In addition, since the ALD method is used, an excellent conductive metal oxide thin film having step coverage and excellent thickness uniformity that can cope with a design rule of 100 nm or less can be formed. Therefore, by using a dielectric film having a perovskite structure (BST, PZT, or the like) as an electrode material, the characteristics of the capacitor can be improved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. Therefore, the shapes and the like of the elements in the drawings are exaggerated in order to emphasize a clearer explanation.

FIG. 2 is a view schematically showing an example of a thin film deposition apparatus for carrying out a thin film deposition method according to the present invention, and FIG. 3 is a graph showing a process sequence of a first embodiment of the thin film deposition method according to the present invention to be.

2, the thin film deposition apparatus 1 is for depositing a thin film made of a material of a ternary or higher system on the wafer w in the reactor 10. [ The reactor 10 has an internal space and is equipped with a gas supply device 20 capable of introducing oxygen-containing gas as different types of metal sources, purge gas, reaction gas and pretreatment gas into the interior thereof. The gas introduced from the gas supply device 20 is injected into the reactor 10 through the showerhead 30 located at the upper inside of the reactor 10. [ The wafer block 40 located below the showerhead 30 supports and supports the wafer W and is installed in the reactor 10 so as to be able to move up and down. There is also provided a pump 50 for keeping the inside of the reactor 10 at a predetermined pressure.

Next, a first embodiment of the present invention will be described with reference to FIG.

First, the wafer w is placed on the wafer block 40 in the reactor 10. This is accomplished by taking a wafer w from a transfer module (not shown) into a robot arm (not shown), introducing the wafer w into the reactor 10, and placing it on the wafer block 40. At this stage, the wafer block 40 preheats the wafer w to an appropriate temperature. The temperature of the pretreatment step is most preferably the same as the temperature of the subsequent film formation step, but may be lower or higher than the temperature of the film formation step if necessary. If the film to be formed in the subsequent process is SrRuO ₃ , the temperature of the pretreatment step may be 250 ° C to 600 ° C which is lower or higher than the film forming temperature.

After the wafer (w) is placed, oxygen atom containing gas is supplied and purged as shown in Fig. 3 to pre-treat the reactor (10) and the wafer (w). The oxygen atom containing gas may be any one selected from oxygen, H ₂ O, and ozone, or may be an activated oxygen source selected from oxygen plasma and H ₂ O plasma. The oxygen-containing gas is supplied in a pulse type maintaining the supply for a predetermined time period as shown in FIG. 3, and then an inert gas such as argon or nitrogen is supplied to the reactor 10 to carry out purging. Further, the purge gas may be pumped by the pump 50 instead of the purge gas supply, and the purge time may be adjusted to 0.1 to 10 seconds. The pretreatment of the reactor 10 and the wafer w has the effect of increasing the adsorption efficiency of the metal source to the wafer w in the subsequent film process and removing any residual components from the reactor 10.

Next, a first metal source is supplied into the reactor 10, and purging, reactive gas supply, and purging are performed to form an oxide of the first metal on the wafer w. That is, an oxide of the first metal is formed by the ALD method.

The ALD method is a deposition method using a chemical reaction like a CVD method, but is distinguished in that each gas is flowed into the reactor one by one without being mixed in the reactor. That is, although the reaction of the first metal source and the reaction gas is used, only the first metal source is injected first. At this time, the first metal source molecule is chemically adsorbed onto the wafer w. The first metal source remaining in the reactor 10 or physically adsorbed onto the chemisorption layer is then purged with an inert gas such as argon or nitrogen. Of course, it may be pumped by the pump 50, not by the purge gas supply. When only the reactive gas is injected thereafter, the reaction between the first metal source and the reactive gas takes place only on the surface having the chemisorbed first metal source, and the monolayer thin film is deposited. For this reason, even a surface having any morphology can attain 100% step coverage. After the reaction of the first metal source and the reaction gas, the reaction gas remaining in the reactor 10 and the reaction by-products are purged.

At this time, for example, Sr is selected as the first metal and the reaction gas is of the same kind as the oxygen atom-containing gas, and the ligand contained in the Sr source is removed in the form of CO ₂ and H ₂ O through a combustion reaction At the same time, the center Sr atoms are oxidized to form a SrO film. The pretreatment step before the film formation allows the Sr source to smoothly adsorb the wafers (w), and the SrO film can be smoothly formed.

Then, the oxygen-containing gas is again supplied and purged to pre-treat the reactor 10 and the wafer w once again. Pretreatment of the reactor 10 and the wafer w has the effect of increasing the adsorption efficiency of the next metal source to the wafer w and removing residual or deposited SrO components from the reactor 10.

Next, a second metal source is fed into the reactor 10 and purged, reactant gas fed and purged to form an oxide of a second metal on the oxide of the first metal, such as SrO. The reaction gas at this time may be the same kind as the oxygen atom-containing gas. When Ru is selected as the second metal, for example, a RuO film is formed at this stage, and a SrO / RuO composite film is formed on the wafer w, thereby forming a SrRuO ₃ layer. Since the pretreatment is performed on the reactor 10 and the wafer w, the dependency of the underlying film on RuO is improved, The Ru source can be adsorbed smoothly, and the RuO film can be uniformly formed. As a result of this pretreatment, it is possible to deposit a composite film having a constant composition and thickness of the polyatoms.

In this embodiment, the pre-treatment -> the first metal oxide formation -> the pretreatment -> the second metal oxide formation forms one cycle, and this cycle is repeated until a multi-element thin film having a desired thickness is deposited.

As a modification of the present embodiment, as shown in FIG. 4, the pretreatment may be performed before the first metal oxide forming step or the second metal oxide forming step. For example, as shown in FIG. 4, The second metal oxide formation may take one cycle, and the first metal oxide formation-> pre-treatment-> second metal oxide formation may take one cycle, as shown in FIG. In addition, the pretreatment may not be included in the cycle, but the first metal oxide formation-> the second metal oxide formation may form a cycle, and pretreatment may be carried out therebetween as necessary.

On the other hand, in the present embodiment, the supply time of each metal source is maintained at 0.1 to 10 seconds because the adsorption reaction and the ligand elimination reaction are sufficiently performed, and the purge time between each metal source and the reaction gas supply is 0.1 to 10 seconds, while the purge time is advantageously longer, but is preferably maintained at 0.1 to 10 seconds to reduce the cycle time.

On the other hand, in the thin film deposition method according to FIG. 3, the same effect can be obtained even if the order of supplying the Sr source and the Ru source is changed. The present invention can be applied to other types of multi-layer thin films including Ru having a particularly high dependency on the lower film. In this case, it is necessary to perform the pre-treatment step before supplying the Ru source to reduce the dependence of the lower film on the Ru source Therefore, it is desirable. The present invention is also applicable to the formation of a conductive metal oxide such as LaNiO ₃ .

6 is a graph showing a process sequence of the second embodiment of the thin film deposition method according to the present invention.

The same process as in the first embodiment is performed in the same manner as in the first embodiment except that the pretreatment-> the formation of the first metal oxide-> the pretreatment-> the formation of the second metal oxide forms one cycle. However, There is a difference in that the plasma is blown into the reactor 10 as shown in Fig. The plasma may be a direct plasma method of applying high frequency power directly into the reactor 10 or a remote plasma method of forming a plasma from the outside and introducing the plasma into the reactor 10.

When the plasma is generated, oxygen or H ₂ O is supplied as the oxygen atom containing gas to generate an activated oxygen source such as an oxygen plasma or H ₂ O plasma. And the reactive gas can also be such an activated oxygen source. When using an activated oxygen source, it is possible not only to burn the ligand of the metal source at a very low temperature but also to oxidize the central metal atom, and since it has a very high energy, the temperature of the ligand decomposition reaction can be greatly lowered. Also, since the activated oxygen is used, the efficiency of the pretreatment is also good.

7 is a result of depositing the SrRuO ₃ according to the first embodiment of the present invention, shows the composition of Sr and Sr century, Ru intensity and the result of a certain thickness to allow reproducible SrRuO ₃ is deposited. This is because the adsorption efficiency of each metal source is increased by pretreatment and the atmosphere of the reactor is improved to a form suitable for film deposition.

 While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications can be made by those skilled in the art within the technical scope of the present invention. Is obvious.

FIG. 1 is a graph showing composition and thickness reproducibility when a SrO / RuO composite film is deposited by a conventional ALD method.

2 is a schematic view illustrating an example of a thin film deposition apparatus capable of performing the multi-element metal oxide thin film deposition method according to the present invention.

3 is a graph showing a process sequence of the first embodiment of the method for depositing a multi-element metal oxide thin film according to the present invention.

4 is a graph showing a process sequence of a modification of the method for depositing a multi-element metal oxide thin film according to the present invention.

5 is a graph showing a process sequence of another modification of the method for depositing a multi-element metal oxide thin film according to the present invention.

6 is a graph showing a process sequence of a second embodiment of the method for depositing a multi-element metal oxide thin film according to the present invention.

FIG. 7 is a graph showing composition and thickness reproducibility when a SrO / RuO 2 composite film is deposited by the method according to the present invention.

Description of the Related Art [0002]

1 ... Thin Film Deposition Device 10 ... Reactor w ... Wafer

20 ... gas supply device 30 ... showerhead 40 ... wafer block

50 ... pump

Claims (6)

Placing the wafer on a wafer block within the reactor; Subjecting the reactor and the wafer to pretreatment by supplying and purge oxygen-containing gas into the reactor; Forming a first metal oxide on the wafer by supplying and purge a first metal source into the reactor; Subjecting the reactor and the wafer to pretreatment by supplying and purge oxygen-containing gas into the reactor; And Forming a second metal oxide on the oxide of the first metal by supplying and purging a second metal source into the reactor, and supplying and purge the reaction gas, Containing gas and the reactive gas only during the supply of the oxygen atom-containing gas and the reactive gas, Wherein the temperature of the pretreatment step is equal to the temperature of the step of forming the oxide of the first metal and the step of forming the oxide of the second metal. The method of claim 1, wherein the oxygen atom-containing gas is any one selected from oxygen, H ₂ O, and ozone, or is an activated oxygen selected from oxygen plasma and H ₂ O plasma. delete The method of claim 1, wherein one of the first metal and the second metal is Ru. 2. The method of claim 1, wherein high-frequency power is directly applied to the reactor during the supply of the oxygen-containing gas and the reaction gas, or plasma is formed from the outside and introduced into the reactor. . 3. The method of claim 2, wherein the oxygen-containing gas and the reactive gas are the same.

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