Thin film forming method using surface protective material

Abstract

According to one embodiment of the present invention, a method for forming a thin film using a surface protective substance includes: a surface protective layer forming step, supplying a surface protective substance into a cavity where a substrate is placed to form a surface protective layer on the surface of the substrate; a step of purifying the interior of the cavity once; a metal precursor supplying step, supplying a metal precursor into the cavity; a step of purifying the interior of the cavity twice; and a thin film forming step, supplying a reaction substance into the cavity to react with the metal precursor to form a thin film.

Description

Technical Field

[0001] The present invention relates to a thin film forming method, and more particularly, to a thin film forming method, so that the film thickness and step coverage can be easily controlled. Background Art

[0002] DRAM devices have continued to become smaller through the development of innovative technologies and have reached the 10nm era. In order to improve performance and reliability, it is necessary to maintain high capacitance and low leakage characteristics even if the capacitor size is reduced, and a high breakdown voltage is also required.

[0003] In the past, when a single zirconium oxide film was used as the dielectric film of MIM capacitors, although the equivalent oxide film thickness characteristic (Toxeq) was good, the leakage characteristic was weak. In order to overcome these problems, a combined high dielectric layer such as ZrO2 / Al2O3 / ZrO2 is widely used.

[0004] However, these dielectric films are thicker than ZrO2 dielectric films, so the Toxeq characteristics are not good. In addition, the ZAZ structure of Al2O3 is a structure that prevents capacitor leakage. When the thickness is too large, the electrostatic capacitance becomes smaller; when the thickness is too small, the leakage increases, so the thickness needs to be properly controlled.

[0005] Therefore, in order to maintain certain capacitance and leakage characteristics, it is necessary not only to develop materials that meet the characteristics, but also to make the capacitor dielectric film ultra-thin. Summary of the invention

[0006] Issues to be solved

[0007] An object of the present invention is to provide a thin film forming method capable of forming a very thin film.

[0008] Another object of the present invention is to provide a thin film forming method capable of forming a thin film with good step coverage.

[0009] Other objects of the present invention will become more apparent from the following detailed description.

[0010] Problem Solution

[0011] According to one embodiment of the present invention, a method for forming a thin film using a surface protective substance having multiple ether groups is characterized in that it includes: a metal precursor supplying step, supplying a metal precursor to the inside of a cavity where a substrate is placed, and adsorbing the metal precursor on the substrate; a step of purifying the inside of the cavity; and a thin film forming step, supplying a reaction substance to the inside of the cavity to react with the adsorbed metal precursor and form a thin film; the method also includes: a surface protective substance supplying step, supplying the surface protective substance to be adsorbed on the substrate; and a step of purifying the inside of the cavity before the thin film forming step.

[0012] The surface protecting substance can be represented by the following <Chemical Formula 1>.

[0013] <Chemical Formula 1>

[0014]

[0015] In the above-mentioned <Chemical Formula 1>, n is an integer of 0 to 5, and R1 and R2 are selected from an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0016] The surface protecting substance can be represented by the following <Chemical Formula 2>.

[0017] <Chemical Formula 2>

[0018]

[0019] In the above-mentioned <Chemical Formula 2>, n is an integer of 0 to 5, m is an integer of 1 to 5, and R is selected from a plurality of ether groups including an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0020] The surface protecting substance can be represented by the following <Chemical Formula 3>.

[0021] <Chemical formula 3>

[0022]

[0023] In the above-mentioned <Chemical Formula 3>, n1 and n2 are integers of 0 to 5, m1 and m2 are integers of 1 to 5, and R is selected from a plurality of ether groups including an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0024] The reaction material may be any one of O3, O2, and H2O.

[0025] The metal precursor may be a compound including one or more of the following metals: a trivalent metal including Al, a tetravalent metal including Zr and Hf, and a pentavalent metal including Nb and Ta.

[0026] The metal precursor can be represented by the following <Chemical Formula 4>.

[0027] <Chemical Formula 4>

[0028]

[0029] In the above-mentioned <Chemical Formula 4>, R1, R2 and R3 are different from each other and are each independently selected from an alkyl group having 1 to 6 carbon atoms, a dialkylamine group having 1 to 6 carbon atoms or a cyclic amine group having 1 to 6 carbon atoms.

[0030] Effects of the Invention

[0031] According to an embodiment of the present invention, a thin film with high purity and no impurities and thinner than a single layer thickness that can be obtained by the existing ALD process can be formed. Since the film growth rate is very slow, the film thickness can be easily adjusted, the step coverage can be controlled, and the electrical characteristics and reliability of the device can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is a flowchart briefly showing a thin film forming method according to an embodiment of the present invention.

[0033] Figure 2 : is a diagram briefly showing a supply cycle according to an embodiment of the present invention.

[0034] Figure 3 This is a graph showing GPC of an aluminum oxide film according to the process temperature in Comparative Example 1 of the present invention.

[0035] Figure 4 This is a graph showing secondary ion mass spectrometry (SIMS) for analyzing the surface of an aluminum oxide film according to Comparative Example 1 of the present invention.

[0036] Figure 5 This is a graph showing GPC of aluminum oxide films according to the process temperature in Comparative Examples 1 and 2 and Example 1 of the present invention.

[0037] Figure 6 This is a graph showing secondary ion mass spectrometry (SIMS) for analyzing the surface of an aluminum oxide film according to Example 1 of the present invention.

[0038] Figure 7This is a graph showing GPC of aluminum oxide films according to process temperatures in Comparative Examples 1 and 2 and Examples 1 and 2 of the present invention. DETAILED DESCRIPTION

[0039] Below, refer to the attached Figures 1 to 7 The preferred embodiment of the present invention is described in more detail. The embodiment of the present invention can be deformed into various forms, and the scope of the present invention should not be interpreted as being limited to the embodiment described below. This embodiment is provided to explain the present invention in more detail to a person skilled in the art to which the present invention belongs. Therefore, in order to emphasize a clearer description, the shapes of the elements appearing in the drawings may be exaggerated.

[0040] The existing precursor separate process has the problem of poor step coverage due to film unevenness such as thickening of the film at the upper part (or entrance side) and thinning of the film at the lower part (or inner side) in the groove structure with a high aspect ratio (for example, above 40:1).

[0041] However, the surface protection material described below has the same function as the metal precursor and is adsorbed at a higher density in the upper part of the groove than in the lower part, thereby preventing the metal precursor in the subsequent process from being adsorbed, thereby forming a thin film of uniform thickness in the groove.

[0042] Figure 1 is a flowchart briefly showing a thin film forming method according to an embodiment of the present invention, Figure 2 1 is a diagram briefly showing a supply cycle according to an embodiment of the present invention. The substrate is loaded into the process chamber, and the following atomic layer deposition process (ALD) conditions are adjusted. The atomic layer deposition process conditions may include the temperature of the substrate or the process chamber, the chamber pressure, and the gas flow rate, and the temperature is 50 to 600°C.

[0043] The substrate is exposed to the surface protection material supplied to the inside of the chamber, and the surface protection material is adsorbed on the surface of the substrate. During the process, the surface protection material has a similar behavior to the metal precursor, and in the groove structure with a high aspect ratio (for example, 40:1 or more), it is adsorbed at a high density at the upper part (or the entrance side) and at a low density at the lower part (or the inner side), which hinders the metal precursor from being adsorbed in the subsequent process.

[0044] The surface protective material has a plurality of ether groups and can be represented by the following <Chemical Formula 1>.

[0045] <Chemical Formula 1>

[0046]

[0047] In the above-mentioned <Chemical Formula 1>, n is an integer of 0 to 5, and R1 and R2 are selected from an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0048] In addition, the surface protective substance can be represented by the following <Chemical Formula 2>.

[0049] <Chemical Formula 2>

[0050]

[0051] In the above-mentioned <Chemical Formula 2>, n is an integer of 0 to 5, m is an integer of 1 to 5, and R is selected from a plurality of ether groups including an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0052] In addition, the surface protective substance can be represented by the following <Chemical Formula 3>.

[0053] <Chemical formula 3>

[0054]

[0055] In the above <Chemical Formula 3>, n1 and n2 are integers of 0 to 5, m1 and m2 are integers of 1 to 5, and R is selected from a plurality of ether groups including an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

[0056] Thereafter, a purge gas (eg, an inert gas such as Ar) is supplied into the chamber to remove or purge the non-adsorbed surface protection substances or by-products.

[0057] Afterwards, the substrate is exposed to a metal precursor supplied into the chamber, and the metal precursor is adsorbed on the surface of the substrate. The metal precursor may include a group III element such as Al, or a group IV element such as Zr and Hf, or a group V element such as Nb and Ta.

[0058] In addition, more specifically, the metal precursor can be represented by the following <Chemical Formula 4>.

[0059] <Chemical Formula 4>

[0060]

[0061] In the above <Chemical Formula 4>, R1, R2 and R3 are different from each other and are each independently selected from an alkyl group having 1 to 6 carbon atoms, a dialkylamine group having 1 to 6 carbon atoms or a cyclic amine group having 1 to 6 carbon atoms.

[0062] For example, the surface protection substance described above is more densely adsorbed on the upper part of the groove than on the lower part, and the metal precursor cannot be adsorbed to the position where the surface protection substance has been adsorbed. That is, in the past, the metal precursor was more densely adsorbed on the upper part of the groove than on the lower part, showing a high density, but as in this embodiment, the surface protection substance is densely adsorbed on the upper part of the groove and hinders the adsorption of the metal precursor, so the metal precursor will not be excessively adsorbed on the upper part of the groove, but uniformly adsorbed on the upper part / lower part of the groove, which can improve the step coverage of the thin film described later.

[0063] Next, a purge gas (eg, an inert gas such as Ar) is supplied into the chamber to remove or purge the unadsorbed metal precursor or by-products.

[0064] Then, the substrate is exposed to the reaction material supplied into the chamber, and a thin film is formed on the surface of the substrate. The reaction material reacts with the metal precursor layer to form a thin film. The reaction material can be O3, O2, or H2O gas, and a metal oxide film can be formed by the reaction material. At this time, the protective material adsorbed by the reaction material is oxidized and separated and removed from the surface of the substrate.

[0065] Then, a purge gas (for example, an inert gas such as Ar) is supplied into the chamber to remove or purge the non-adsorbed surface protection substances / unreacted substances or by-products.

[0066] Furthermore, although it has been described above that the surface protecting substance is supplied before the metal precursor, the surface protecting substance may be supplied after the metal precursor, or the metal precursor may be supplied both before and after the surface protecting substance.

[0067] ——Comparative Example 1

[0068] The aluminum oxide film was formed on the silicon substrate without using the surface protection material described above. The aluminum oxide film was formed by an atomic layer deposition process, the atomic layer deposition process temperature was 250 to 350° C., and O 3 gas was used as the reaction material.

[0069] The process of forming the aluminum oxide film by the atomic layer deposition process is as follows: The following process is performed as one cycle.

[0070] 1) Ar is used as a carrier gas to supply an aluminum precursor (Trimethylaluminium) to a reaction chamber at room temperature, and the aluminum precursor is adsorbed on a substrate.

[0071] 2) Supplying Ar gas into the reaction chamber to remove unabsorbed aluminum precursor or by-products.

[0072] 3) Supply O3 gas into the reaction chamber to form a monolayer.

[0073] 4) Ar gas is supplied into the reaction chamber to remove unreacted substances or by-products.

[0074] The thickness of the aluminum oxide film obtained by the above process was measured. The thickness of the aluminum oxide film obtained in each cycle of the ALD process was about cycle.

[0075] Figure 3 1 is a graph showing the GPC (Growth Per Cycle) of the aluminum oxide film according to the process temperature according to Comparative Example 1 of the present invention. Figure 3 As shown, in the substrate temperature range of 250 to 350° C., an ideal ALD behavior is exhibited with almost no GPC change as the substrate temperature increases.

[0076] Figure 4 A graph showing secondary ion mass spectrometry (SIMS) for analyzing the surface of an aluminum oxide film according to Comparative Example 1 of the present invention. Figure 4 As shown, it was confirmed that no impurities (eg, carbon atoms) derived from the aluminum precursor TMA remained in the oxide film.

[0077] ——Comparative Example 2

[0078] A substance with one ether group was used as a surface protective substance to form an aluminum oxide film on a silicon substrate. The aluminum oxide film was formed by an atomic layer deposition process, and the atomic layer deposition process temperature was 250 to 350°C, and O3 gas was used as a reaction medium.

[0079] The aluminum oxide film formation process based on the atomic layer deposition process is as follows. The following process is performed as a cycle (refer to Figure 1 and Figure 2 ).

[0080] 1) Supplying a surface protection substance into the reaction chamber to be adsorbed on the substrate.

[0081] 2) Ar gas is supplied into the reaction chamber to remove unadsorbed surface protection substances or by-products.

[0082] 3) Using Ar as a carrier gas, the aluminum precursor TMA (Trimethylaluminium) is supplied into the reaction chamber at room temperature, and the aluminum precursor is adsorbed on the substrate.

[0083] 4) Supplying Ar gas into the reaction chamber to remove unabsorbed aluminum precursor or by-products.

[0084] 5) Supply O3 gas to the reaction chamber to form a monolayer.

[0085] 6) Ar gas is supplied into the reaction chamber to remove unreacted substances or by-products.

[0086] As a result of using a substance having one ether group as a surface protective substance, the GPC reduction rates were 10.42% and 13.81% at 320°C and 350°C, respectively. As a result, when a substance having one ether group was used as a surface protective substance, a low GPC reduction rate of about 10 to 13% was exhibited.

[0087] ——Example 1

[0088] An aluminum oxide film was formed in the same manner as in Comparative Example 2 except that the surface protective substance was changed from a substance having one ether group to MTHP (Methoxy Tetrahydropyran) having a plurality of ether groups.

[0089] Figure 5 This is a graph showing the GPC of the aluminum oxide film according to the process temperature of Comparative Examples 1 and 2 and Example 1 of the present invention. As a result of using MTHP as the surface protective material, the GPC reduction rate was 33.19% and 34.78% at 300°C and 350°C, respectively. As a result, when a substance having multiple ether groups was used as the surface protective material, a high GPC reduction rate of 33 to 34% was shown. This is considered to be because in the case of a surface protective material having multiple ether groups, the adsorption force to the substrate is increased (or the density is increased) compared to a surface protective material having one ether group, thereby showing a high GPC reduction effect.

[0090] Figure 6 : is a graph showing secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectroscopy) for analyzing the surface of an aluminum oxide film according to Example 1 of the present invention. Figure 6 As shown, it was confirmed that impurities (for example, carbon atoms, etc.) derived from the aluminum precursor TMA and the surface protection substance were not present in the oxide film.

[0091] -Example 2

[0092] An aluminum oxide film was formed in the same manner as in Comparative Example 2 except that the surface protective substance was changed from MTHP to MMTHF (Methoxymethyl Tetrahydrofuran).

[0093] Figure 7This is a graph showing the GPC of the aluminum oxide film according to the process temperature according to Comparative Examples 1 and 2 and Examples 1 and 2 of the present invention. As a result of using MMTHF as a surface protective substance, the GPC reduction rate was 35.35% and 29.86% at 300°C and 350°C, respectively. As a result, when MMTHF was used as a surface protective substance, a high GPC reduction rate of 29 to 35% was shown.

[0094] In conclusion, the surface protection material exhibits a high GPC reduction effect through high adsorption performance, thereby being able to form a thinner and impurity-free high-purity film than a single layer thickness that can be obtained by the existing ALD process. Since its film growth rate is very slow, the film thickness can be easily adjusted, the step coverage can be controlled, and the electrical characteristics and reliability of the device can be improved.

[0095] The present invention has been described in detail above by using the embodiments, but embodiments in different forms are also possible. Therefore, the technical concept and scope of the claims described below are not limited to the embodiments.

[0096] Industrial Applicability

[0097] The present invention can be applied to various types of semiconductor manufacturing methods.

Claims

1. A method for forming a thin film using a surface protective substance, wherein the surface protective substance has a plurality of ether groups, characterized in that: include: A metal precursor supplying step, supplying the metal precursor into the cavity where the substrate is placed, and adsorbing the metal precursor onto the substrate; A step of purifying the interior of the cavity; and a thin film forming step of supplying a reaction substance into the cavity to react with the adsorbed metal precursor and form a thin film; The method further comprises, before the thin film forming step: a surface protection material supplying step, supplying the surface protection material into the cavity so that the surface protection material is adsorbed onto the substrate; as well as a step of purifying the interior of the cavity, The surface protection material is represented by the following <Chemical Formula 3>: <Chemical formula 3> In the above <Chemical Formula 3>, n1 and n2 are integers of 0 to 5, m1 is an integer of 1 to 5, and R is selected from a plurality of ether groups including an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 12 carbon atoms.

2. The method for forming a thin film using a surface protective substance according to claim 1, wherein: The reaction substance is one of O3, O2, and H2O.

3. The method for forming a thin film using a surface protective substance according to claim 1, wherein: The metal precursor is a compound including one or more of the following metals: a trivalent metal including Al, a tetravalent metal including Zr and Hf, and a pentavalent metal including Nb and Ta.

4. The method for forming a thin film using a surface protective substance according to claim 1, wherein: The metal precursor is represented by the following <Chemical Formula 4>: <Chemical Formula 4> In the above <Chemical Formula 4>, R1, R2 and R3 are different from each other and are each independently selected from an alkyl group having 1 to 6 carbon atoms, a dialkylamine group having 1 to 6 carbon atoms or a cyclic amine group having 1 to 6 carbon atoms.

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