Selective deposition method of silicon oxide film using an amino silane-based precursor.

Abstract

A method for selectively depositing a silicon oxide film using an aminosilane-based precursor is disclosed. The method according to one embodiment includes a preparation step of preparing a substrate on which a first silicon oxide film (SiO2) and a titanium nitride film (TiN) are exposed in a vacuum chamber, a first supply step of supplying an aminosilane-based gas to the vacuum chamber so as to be adsorbed at least on the first silicon oxide film, and a second supply step of supplying an oxidizing agent to the vacuum chamber so as to react with the adsorbed aminosilane-based gas. The first supply step and the second supply step are repeatedly performed a plurality of times to form a second silicon oxide film having a predetermined thickness on the first silicon oxide film.

Description

Technical Field

[0001] The present invention relates to a semiconductor deposition process, and more specifically, to a method for selectively depositing a silicon oxide layer only on a specific region on a substrate using an aminosilane-based precursor.

Background Art

[0002] As the miniaturization of semiconductor elements continues to progress, semiconductor manufacturing processes have become more complex and stringent. As a result, in the case of existing downward patterning processes based on optical lithography, issues such as misalignment non-uniformity due to a decrease in pattern line width (Critical Dimension Face, CD) and an increase in the roughness of the pattern surface (e.g., LER (Line Edge Roughness), LWR (Line Width Roughness)) have become core issues.

[0003] As one solution to such problems, an area-selective deposition process has been proposed. The area-selective deposition process refers to a deposition process in which deposition is performed on a specific region on a substrate, but is controlled so that deposition does not occur on other regions in the vicinity.

[0004] One of the area-selective deposition processes is to perform deposition on the entire surface of a substrate after forming a cover layer that shields the areas where deposition is not intended on the substrate. For example, a method is known in which an ultra-fine pattern cover layer is formed only on a partial area of the substrate using an inhibitor of the self-assembly monolayer series, and then deposition is performed. According to this, after completion of the deposition, by removing the cover layer and the deposited film on its upper side in processes such as ashing and etching, a deposited film (pattern) can be left only on the area of the substrate where the cover layer is not formed. However, this method has the demerits that additional processes for forming and removing the cover layer using an inhibitor are required, so the process is complicated, and also the time required for the deposition process increases. Also, in the deposition process, when applying a plasma-enhanced atomic layer deposition (Plasma Enhanced ALD, PEALD) process using direct plasma, problems such as recess patterns and damage to the underlying layer due to the plasma occur during the process.

[0005] As an area-selective deposition process for solving the above-mentioned demerits, a selective deposition process using the inherent selectivity property of a material is known. According to this, by using the inherent properties of the material, for example, the relative properties of affinity and adhesion to a specific substance, deposition is performed only on the surface of some of the plurality of surfaces of different substances on the substrate. At this time, no deposition occurs on the surface of other substances, or a predetermined reaction is induced. For example, in Korean Patent Publication No. 2018-0111537, "Selective Growth Method" (Patent Document 1), a method is disclosed in which a silicon-based insulating film is selectively grown only on an insulating film while vaporizing a conductive film to reduce the film thickness by repeatedly performing a process of sequentially supplying an aminosilane-based gas having a hydrocarbon group and a reaction gas several times on a workpiece having a substrate on which an insulating film and a conductive film are exposed.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Korean Patent Publication No. 2018 - 0111537 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] In the manufacture of next - generation DRAM devices having ultra - fine patterns, when forming the storage node of DRAM using photolithography and etching processes, problems such as non - uniform line widths and / or the collapse or bending of narrow pillars may occur. Also, when forming a silicon oxide film by supplying a silicon source gas through an ALD process using direct plasma, damage to the exposed metal film is likely to occur.

[0008] Therefore, for a substrate on which a titanium nitride film (TiN) and a silicon oxide film (SiO2) are simultaneously exposed, by utilizing the inherent selective characteristics of the materials, it is required to deposit a silicon oxide film only on the region of the silicon oxide film while not damaging the titanium nitride film. In particular, in the manufacture of a DRAM device having a capacitor node where at least a silicon oxide film is exposed together with a titanium nitride film, a process of selectively depositing a silicon oxide film only on the sidewalls of pillars made of a silicon oxide film without damaging the titanium nitride film is necessary.

[0009] The problem to be solved by the present invention is to provide a selective deposition method of a silicon oxide film using an aminosilane - based precursor that can selectively deposit a silicon oxide film only on a silicon oxide film without damaging a titanium nitride film for a semiconductor substrate on which a titanium nitride film and a silicon oxide film are exposed, by using the inherent selective characteristics of the materials. [Means for Solving the Problems]

[0010] One embodiment of the method for selectively depositing silicon oxide according to the present invention for solving the above problems includes a preparation step of preparing a substrate on which a first silicon oxide film (SiO2) and a titanium nitride film (TiN) are exposed in a vacuum chamber, a first supply step of supplying an aminosilane-based gas to the vacuum chamber so as to be adsorbed at least on the first silicon oxide film, and a second supply step of supplying an oxidizing agent to the vacuum chamber so as to react with the adsorbed aminosilane-based gas. The first supply step and the second supply step are repeatedly performed a plurality of times to form a second silicon oxide film having a predetermined thickness on the first silicon oxide film.

[0011] According to one aspect of the above embodiment, the aminosilane-based gas may include one or more of BDIPADS, DIPAS, and 3DMAS.

[0012] According to another aspect of the above embodiment, the oxidizing agent may include one or more gases selected from ozone gas, oxygen gas, and oxygen / hydrogen mixed gas.

[0013] According to still another aspect of the above embodiment, a pretreatment step of cleaning the substrate with a hydrofluoric acid solution may be further included before the first supply step.

[0014] According to still another aspect of the above embodiment, in the first supply step and the second supply step, the temperature of the vacuum chamber can be set to 100 to 200 °C.

Advantages of the Invention

[0015] According to the above embodiment of the present invention, when the silicon oxide film and the titanium nitride film are simultaneously exposed, the aminosilane-based gas is selectively adsorbed only on the silicon oxide film and not adsorbed or only slightly adsorbed on the titanium nitride film. Therefore, without adding a step of using and then removing an inhibitor, silicon oxide can be selectively deposited only on the silicon oxide film.

Brief Description of the Drawings

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Figure 1

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Figure 2b

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Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms and words used in this specification are terms selected in consideration of the functions in the embodiments, and the meanings of the terms may vary depending on the intention of the invention or conventions, etc. Therefore, the terms used in the embodiments described below should be construed in accordance with the definitions when specifically defined in this specification, and in the absence of specific definitions, should be construed as meanings generally recognized by those skilled in the art.

[0018] FIG. 1 is a flowchart showing an example of a method for selectively depositing a silicon oxide film according to an embodiment of the present invention, and FIGS. 2a to 2c are cross-sectional views schematically showing the states when each step of the selective deposition method shown in FIG. 1 is performed.

[0019] Referring to FIGS. 1 and 2a, first, a workpiece on which a silicon oxide film 22 (first silicon oxide film) and a titanium nitride film 24 are formed on a substrate 10 is loaded into a vacuum chamber (step S1). For subsequent deposition steps, at least the silicon oxide film 22 and the titanium nitride film 24 are exposed on the upper side of the workpiece. Such a workpiece schematically represents a semiconductor element, for example, a structure during the manufacture of a DRAM, and the exposed surfaces of the silicon oxide film 22 and the titanium nitride film 24 become the surfaces to be processed, and a thin film (silicon oxide film) is selectively deposited on the upper side thereof.

[0020] Here, the substrate 10 is a semiconductor wafer, and can be, for example, a silicon wafer, but is not limited thereto. And the silicon oxide film 22 and the titanium nitride film 24 do not necessarily have to be directly formed on the substrate 10, and one or more other material films may be interposed therebetween. The interposed material film may be an insulating film and / or a conductive film, and there is no particular limitation on its type. Depending on the embodiment, one or more silicon oxide films and / or titanium nitride films may be further interposed.

[0021] And the heights of the silicon oxide film 22 and the titanium nitride film 24 do not necessarily have to be the same as shown in the figure, and either one of the films (for example, the titanium nitride film 24) may be higher than the other film (for example, the silicon oxide film 22). Also, on the substrate 10, as shown in the figure, the silicon oxide film 22 and the titanium nitride film 24 do not necessarily have to be formed alternately, and other material films (for example, conductive films such as tungsten (W), copper (Cu), cobalt (Co), etc. and / or insulating films such as silicon nitride film (Si3N4), etc.) may be interposed between adjacent silicon oxide film 22 and titanium nitride film 24.

[0022] According to one aspect of this embodiment, before loading the object to be processed into the vacuum chamber, a step of pre-treating the object to be processed can be further performed. The pre-treatment step is a step for ensuring the surface functional groups of each substrate by removing impurities adhering to the surface of the object to be processed, particularly the silicon oxide film 22 and the titanium nitride film 24, and removing the natural oxide film existing on the substrate surface. More specifically, after washing the object to be processed with a cleaning solution such as a hydrofluoric acid solution (for example, applying it for 30 seconds using a 0.5 wt% HF solution), rinsing step and drying step and the like can be sequentially performed. Here, purified water can be used for the rinsing step, and nitrogen gas or the like can be used for the drying step, but this is merely exemplary.

[0023] Subsequently, referring to FIGS. 1 and 2b, a silicon precursor 32a is supplied into the vacuum chamber so as to be adsorbed at least on the silicon oxide film 22 (S2). At this time, the silicon precursor 32a is not adsorbed at all on the titanium nitride film 24, or even if adsorbed, a relatively small amount is adsorbed. Depending on the embodiment, during the first half cycle of the atomic layer deposition process, the silicon precursor 32a is not adsorbed on the titanium nitride film 24, and after performing a predetermined number of cycles, the silicon precursor 32a may also be adsorbed on the titanium nitride film 24.

[0024] According to this embodiment, the selective adsorption of such a silicon precursor 32a utilizes the inherent selective characteristics of the corresponding substance, and under the same process conditions (for example, the temperature inside the process chamber, pressure, flow rate of the silicon precursor gas, etc.), the silicon precursor 32a is adsorbed only on the silicon oxide film 22, or utilizes the characteristic that a relatively larger amount is adsorbed on the silicon oxide film 22 than on the titanium nitride film 24. Therefore, the silicon precursor 32a does not need to be activated by plasma and supplied to the vacuum chamber, and may be supplied to a vacuum chamber set at a relatively low temperature, about 50 to 300 ° C, preferably about 100 to 200 ° C. At this time, the process temperature may vary depending on the type of precursor used in the subsequent thin film deposition process.

[0025] As the silicon precursor 32a, an aminosilane compound can be used. The aminosilane compound has the characteristic of being easily adsorbed on the surface of the silicon oxide film 22 having an -OH functional group rather than on the surface of the titanium nitride film 24 having no -OH functional group at the end. As will be described later, as a result of experiments by the present inventors, when an atomic layer deposition (ALD) process is performed using an aminosilane compound, a silicon oxide film having a thickness of about 4 to 5 nm grows on the silicon oxide film 22, but it was confirmed that no silicon oxide film grows on the surface of the titanium nitride film 24. According to this embodiment, there is no particular limitation on the type of aminosilane compound, and examples thereof include 1,2-bis(diisopropylamino)disilane (BDIPADS), diisopropylaminosilane (DIPAS), tris(dimethylamino)silane (3DMAS), and the like. However, the type of aminosilane compound is not limited thereto, and trimethylsilyldimethylamine (TMSDMA), tetrakis(dimethylamino)silane (4DMAS), etc. can also be used.

[0026] In step S2, the internal pressure of the vacuum chamber into which the silicon precursor 32a is supplied can be set to a pressure of about 2 Torr or less. And as described above, the internal temperature of the vacuum chamber can be set to a temperature of about 50 to 300 °C, preferably about 100 to 200 °C. The silicon precursor 32a is, for example, evaporated or sublimated and supplied alone in a gaseous state into the vacuum chamber, or may be supplied into the vacuum chamber together with a predetermined carrier gas, such as nitrogen (N2) gas, argon (Ar) gas, helium (He) gas, and / or hydrogen (H2) gas. Alternatively, the silicon precursor 32a may evaporate or sublimate in the vacuum chamber to be in a gaseous state.

[0027] Also, although not shown in the figure, after introducing the silicon precursor 32a into the vacuum chamber, a purge process may be further performed to supply a purge gas for removing the excess silicon precursor and carrier gas that are not adsorbed on the substrate from the vacuum chamber. As the purge gas, an inert gas such as nitrogen gas or argon gas can be used. If the carrier gas in step S2 and the purge gas in the purge process are the same inert gas, there is no need to add a means for supplying only the purge gas, and the purge process is performed simply by interrupting the supply of the silicon precursor while the carrier gas is being supplied to the vacuum chamber. As a result of performing step S2 and the purge process, as shown in FIG. 2b, a single layer of the silicon precursor 32a, that is, an aminosilane-based gas, is formed only on the silicon oxide film 22.

[0028] Next, referring to FIGS. 1 and 2C, an oxidizing agent gas is supplied into the vacuum chamber (S3). As the oxidizing agent gas, ozone (O3) gas, oxygen (O2) gas, etc. are used. Alternatively, depending on the embodiment, other gases containing oxygen as the oxidizing agent gas, such as a mixed gas of oxygen (O2) / hydrogen (H2), water vapor (H2O), etc. may be used. The oxidizing agent gas supplied into the vacuum chamber can be bonded to the silicon of the aminosilane-based gas adsorbed on the silicon oxide film 22. It is preferable that the oxygen gas or the oxygen-containing gas is not in a plasma state. However, if a plasma state oxygen gas or the like is used, the reactivity is too high and it is difficult to ensure the selectivity ratio with respect to the titanium nitride film.

[0029] Thus, when the oxidizing agent gas is supplied, it reacts with the silicon of the aminosilane precursor 32a adsorbed on the silicon oxide film 22, and a single-layer silicon oxide film 32 (second silicon oxide film) is further formed on the silicon oxide film 22. On the other hand, the silicon oxide film 32 is not formed on the titanium nitride film 24 on which the aminosilane precursor 32a is not adsorbed.

[0030] Subsequently, although not shown, a purge gas is supplied into the vacuum chamber to exhaust the remaining oxidizing agent gas, reaction by-products, etc. to the outside of the vacuum chamber. Thereby, one cycle of the atomic layer deposition (ALD) process for selective deposition of the silicon oxide film 32 is completed.

[0031] Subsequently, the ALD process cycle including the above-described steps S2 and S3 is repeated a predetermined number of times until a silicon oxide film 32 with a desired thickness is formed on the silicon oxide film 22. At this time, as the number of cycle repetitions increases, a silicon oxide film is further formed on the silicon oxide film 22, while no silicon oxide film is formed on the titanium nitride film 24, or a silicon oxide film (not shown) with a predetermined thickness (however, a very small thickness compared to that formed on the silicon oxide film 22) may be formed. However, in the latter case, a predetermined etching process such as the Atomic Layer Etching (ALE) method may be used to simultaneously remove a part of the upper side of the silicon oxide film 32 deposited on the silicon oxide film 22 and the silicon oxide film deposited on the titanium nitride film 24, so that finally only the silicon oxide film 32 with the desired thickness remains on the silicon oxide film 22.

[0032] Figure 3 is a graph showing the results of measuring the water contact angle (WCA) of the material film on the substrate subjected to a predetermined treatment. The measurement of the water contact angle is for grasping the hydrophilic characteristics of the material film, and thereby, it is possible to predict how well the aminosilane-based compound can be adsorbed on the material film.

[0033] Figure 3 shows the water contact angles measured after pre-treating the silicon oxide film (SiO2) and the titanium nitride film (TiN) with a hydrogen fluoride (HF) solution (after HF), heating the substrate to 50°C (Heating 50(°C)), and then performing the step of adsorbing a single layer of BDIPADS as in step S2 of FIG. 1 (BDIPADS). The adsorption step of BDIPADS was also carried out at a process temperature of 50°C with an exposure time of 2 seconds corresponding to one cycle of ALD.

[0034] Referring to FIG. 3, in the case of a silicon oxide film, the water contact angle was about 4° after simply treating the substrate with HF, but when heated to 50°C, the water contact angle slightly increased to about 7°, and it can be seen that the water contact angle increased to about 65° after the BDIPADS adsorption process. According to this, it can be seen that a single layer of BDIPADS was actually formed on the silicon oxide film after the BDIPADS adsorption process. On the other hand, in the case of a titanium nitride film, the water contact angle was about 25° after simply treating the substrate with HF, but the water contact angle increased to about 50° after the BDIPADS adsorption process, which is almost the same as the water contact angle when heated to 50°C, indicating that almost no single layer of BDIPADS was formed on the titanium nitride film even after the BDIPADS adsorption process.

[0035] To summarize, when an amino-silane compound such as BDIPADS is brought into contact with a substrate on which both a silicon oxide film and a titanium nitride film are exposed, the amino-silane compound is adsorbed on the silicon oxide film, but it can be seen that the amino-silane compound is not adsorbed or the adsorption rate is extremely low on the titanium nitride film.

[0036] FIG. 4 is a graph showing the deposition rate of the silicon oxide film 32 depending on the temperature of the ALD process, that is, the temperature inside the vacuum chamber. The experimental results in FIG. 4 are for the case where the silicon oxide film 32 was deposited by an ALD process composed of a cycle of 2 seconds of BDIPADS precursor exposure, 30 seconds of nitrogen purge, 5 seconds of ozone oxidant exposure, and 60 seconds of nitrogen purge, with the ALD process temperature set at 50°C, 150°C, and 250°C respectively. Referring to FIG. 4, the deposition rate of the silicon oxide film 32 increases as the process temperature increases, but it is deposited at an average deposition rate of about 0.5 Å to 1 Å per cycle, and it can be seen that the deposition rate is even greater when the number of cycles exceeds 50 compared to before. According to the same graph, it can be seen that at least 50 or more ALD cycles must be performed to deposit a silicon oxide film 32 with a thickness of about 30 Å to 100 Å.

[0037] Figures 5 to 7 are Ion-milling transmission electron microscope (TEM) photographs showing the results of selectively depositing a silicon oxide film using the ALD process according to the above-described embodiments of the present invention, where the temperature inside the vacuum chamber is 200 °C, 100 °C, and 150 °C, respectively. All process conditions other than the temperature are the same. After cleaning (pretreating) the substrate with a 0.5% hydrofluoric acid (HF) solution for 30 seconds, each cycle of the ALD process consisted of 2 seconds of BDIPADS precursor supply, 30 seconds of nitrogen purge, 5 seconds of ozone oxidant supply, and 60 seconds of nitrogen purge for deposition.

[0038] In Figures 5 to 7, Figure (a) is an Ion-milling TEM photograph (SiO2_before ALD) of the silicon oxide film before the ALD process, Figure (b) is an Ion-milling TEM photograph (SiO2_after ALD) of the silicon oxide film after the ALD process, and Figure (c) is an Ion-milling TEM photograph (TIN_after ALD) of the titanium nitride film after the ALD process.

[0039] Referring to Figure 5, as a result of performing the ALD process at 200 °C for 120 cycles, a silicon oxide film with a thickness of 12.7 nm (32.4 nm - 19.7 nm) was deposited on the silicon oxide film, while a silicon oxide film with a thickness of 8.4 nm was deposited on the titanium nitride film. Therefore, at a process temperature of 200 °C, the silicon oxide film has a selectivity ratio in which 4.3 nm more silicon oxide film is deposited on the silicon oxide film compared to the titanium nitride film.

[0040] Referring to Figure 6, as a result of performing the ALD process at 100 °C for 60 cycles, a silicon oxide film with a thickness of 2.8 nm (21.4 nm - 18.6 nm) was deposited on the silicon oxide film, while it can be seen that no silicon oxide film was deposited on the titanium nitride film. Therefore, at a process temperature of 100 °C, the silicon oxide film has a selectivity ratio in which 2.8 nm more silicon oxide film is deposited on the silicon oxide film compared to the titanium nitride film.

[0041] Referring to FIG. 7, as a result of performing the ALD process at 150° C. for 35 cycles, a silicon oxide film with a thickness of 2.8 nm (21.7 nm - 18.9 nm) was deposited on the silicon oxide film, while it was found that no silicon oxide film was deposited on the titanium nitride film. Therefore, at a process temperature of 150° C., the silicon oxide film has a selectivity in which 2.8 nm of silicon oxide film is deposited more on the silicon oxide film than on the titanium nitride film.

[0042] Also, although not shown in the figure, as a result of performing the ALD process at 50° C., a silicon oxide film with a thickness of 4.5 nm was deposited on the silicon oxide film, while it was confirmed that a silicon oxide film with a thickness of 2.2 nm was deposited on the titanium nitride film. Therefore, at a process temperature of 50° C., the silicon oxide film has a selectivity in which 2.3 nm of silicon oxide film is deposited more on the silicon oxide film than on the titanium nitride film.

[0043] As described above, the present invention has been described in detail with reference to preferred embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made by those having ordinary knowledge in the art within the scope of the technical idea of the present invention.

Industrial Applicability

[0044] The present invention can be applied to the manufacturing process of semiconductor elements.

Claims

1. A preparation step of preparing a substrate on which a first silicon oxide film (SiO₂) and a titanium nitride film (TiN) are exposed in a vacuum chamber, A first supply step of supplying an aminosilane-based gas to the vacuum chamber so as to be adsorbed at least on the first silicon oxide film, A second supply step of supplying an oxidizing agent to the vacuum chamber so as to react with the adsorbed aminosilane-based gas, and The first supply step and the second supply step are repeatedly performed a plurality of times to form a second silicon oxide film having a predetermined thickness on the first silicon oxide film. A method for selective deposition of silicon oxide, characterized in that.

2. The method for selective deposition of silicon oxide according to claim 1, wherein the aminosilane-based gas contains one or more of BDIPADS, DIPAS, and 3DMAS.

3. The method for selective deposition of silicon oxide according to claim 1, wherein the oxidizing agent contains one or more gases selected from ozone gas, oxygen gas, and oxygen / hydrogen mixed gas.

4. Before the first supply step, The method for selective deposition of silicon oxide according to claim 1, further comprising a pretreatment step of cleaning the substrate with a hydrofluoric acid solution.

5. In the first supply step and the second supply step, the temperature of the vacuum chamber is set to 100 to 200°C. The method for selective deposition of silicon oxide according to claim 1, characterized in that.

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