KR20210103274A - Method of depositing thin films using protective material - Google Patents

Abstract

According to one embodiment of the present invention, a thin film formation method using a surface protection material having an asymmetric ether group comprises: a metal precursor supply step of supplying a metal precursor to the inside of a chamber in which a substrate is placed, and adsorbing the metal precursor to the substrate; a step of purging the interior of the chamber; and a thin film forming step of supplying a reactant to the inside of the chamber to react with the adsorbed metal precursor to form a thin film. The method further comprises: a surface protection material supply step of supplying a surface protection material to adsorb the same to the substrate, before the thin film forming step; and a step of purging the inside of the chamber.

Description

A method of forming a thin film using a surface protection material {METHOD OF DEPOSITING THIN FILMS USING PROTECTIVE MATERIAL}

The present invention relates to a method for forming a thin film, and more particularly, to a method for forming a thin film in which it is easy to control the thickness and step coverage of the thin film by forming a thin film having a very thin thickness.

The existing two-dimensional NAND flash process has technical limitations in that the degree of integration in a small area increases, causing cell-to-cell interference and leakage. To overcome these shortcomings, 3D NAND Flash technology that stacks cells vertically has emerged.

The advantage of 3D NAND Flash including a multilayer stack is that it can significantly reduce interference between cells to improve characteristics, and increase the stack to achieve data capacity expansion and cost reduction. Due to this, compared to the conventional NAND memory device, it has more than twice the write speed, more than ten times the durability, and half the power consumption.

However, as the height increases with the ultra-high stacking of more than 90 layers, it becomes more difficult to secure a uniform thin film on the sidewall, and there are limitations such as a difference in characteristics between the uppermost cell and the lowermost cell. Accordingly, there is a growing demand for a manufacturing method capable of forming a thin film of uniform thickness with excellent step coverage on a three-dimensional structure having a large aspect ratio.

Korean Patent Publication No. 2007-0015958 (2007.02.06.)

It is an object of the present invention to provide a method capable of forming a thin film having good step coverage.

Another object of the present invention is to provide a thin film forming method capable of forming a very thin thin film.

Further objects of the present invention will become more apparent from the following detailed description.

According to an embodiment of the present invention, a method for forming a thin film using a surface protection material having an asymmetric ether group includes: supplying a metal precursor into a chamber in which a substrate is placed, and adsorbing the metal precursor to the substrate; purging the interior of the chamber; and supplying a reactant to the inside of the chamber to react with the adsorbed metal precursor and forming a thin film to form a thin film, wherein the method includes, before the thin film forming step, supplying the surface protection material to the substrate adsorbing surface protection material supply step; and purging the inside of the chamber.

The surface protection material may be represented by the following <Formula 1>.

<Formula 1>

In <Formula 1>, n = an integer of 0 to 10, R1 is each independently selected from an alkyl group having 1 to 10 carbon atoms or hydrogen, and R2 is an alkyl group having 1 to 10 carbon atoms.

The surface protection material may be represented by the following <Formula 2>.

<Formula 2>

In <Formula 2>, n = an integer of 1 to 10, m = an integer of 0 to 10, R1 is each independently selected from an alkyl group having 1 to 10 carbon atoms or hydrogen, R2 is an alkyl group having 1 to 10 carbon atoms am.

The reactant may be any one of O3, O2, and H2O.

The metal precursor may be a trivalent metal including Al.

The metal precursor may be represented by the following <Formula 3>.

<Formula 3>

In <Formula 3>, 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 having 1 to 6 carbon atoms, or a cycloamine group having 1 to 6 carbon atoms.

According to an embodiment of the present invention, it is possible to form a thin film having good step coverage. The surface protection material has a similar behavior to the metal precursor during the process, so in a high aspect ratio structure, it is adsorbed at a high density on the upper side (or on the inlet side) and with a low density on the lower side (or on the inner side), and in the subsequent process, the metal precursor is prevent adsorption. Accordingly, the metal precursor can be uniformly adsorbed into the structure.

In particular, it is possible to form a high-purity thin film without impurities while reducing the difference in characteristics of the uppermost and lowermost cells even in an ultra-high stacked structure with excellent step coverage, and to improve the electrical characteristics and reliability of the device.

1 is a flowchart schematically illustrating a method for forming a thin film according to an embodiment of the present invention.
2 is a graph schematically illustrating a supply cycle according to an embodiment of the present invention.
3 is a graph showing the GPC of the aluminum oxide film according to Comparative Examples and Examples 1 and 2 according to the process temperature of the present invention.
4 is a graph showing Secondary Ion Mass Spectroscopy (SIMS) for analyzing the surface of an aluminum oxide film according to a comparative example of the present invention.
5 is a graph showing Secondary Ion Mass Spectroscopy (SIMS) for analyzing the surface of an aluminum oxide film according to Example 1 of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings 1 to 5. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. These examples are provided to explain the present invention in more detail to those of ordinary skill in the art to which the present invention pertains. Accordingly, the shape of each element shown in the drawings may be exaggerated to emphasize a clearer description.

The conventional precursor alone process has a problem of poor step coverage because the thin film is not uniform, such as a thin film at the top (or the inlet side) and thin film at the bottom (or inside) in a high aspect ratio structure.

However, the surface protection material described below behaves the same as the metal precursor, and prevents the metal precursor, which is a subsequent process, from being adsorbed in a state where it is adsorbed at a higher density on the upper part than the lower part of the structure, thereby forming a thin film with a uniform thickness in the structure. to be able to form

1 is a flowchart schematically illustrating a method for forming a thin film according to an embodiment of the present invention, and FIG. 2 is a graph schematically illustrating a supply cycle according to an embodiment of the present invention. The substrate is loaded into the process chamber, and the following ALD process conditions are adjusted. The ALD process conditions may include a temperature of a substrate or a process chamber, a chamber pressure, and a gas flow rate, and the temperature is 50 to 500°C.

The substrate is exposed to the surface protection material supplied to the inside of the chamber, and the surface protection material is adsorbed to the surface of the substrate. The surface protection material has a similar behavior to the metal precursor during the process, so in a high aspect ratio structure, it is adsorbed at a high density on the upper side (or on the inlet side) and with a low density on the lower side (or on the inner side), and the metal precursor in the subsequent process prevent adsorption.

The surface protection material has an asymmetric ether group, and may be represented by the following <Formula 1>.

<Formula 1>

In <Formula 1>, n = an integer of 0 to 10, R1 is each independently selected from an alkyl group having 1 to 10 carbon atoms or hydrogen, and R2 is an alkyl group having 1 to 10 carbon atoms.

In addition, the surface protection material may be represented by the following <Formula 2>.

<Formula 2>

In <Formula 2>, n = an integer of 1 to 10, m = an integer of 0 to 10, R1 is each independently selected from an alkyl group having 1 to 10 carbon atoms or hydrogen, R2 is an alkyl group having 1 to 10 carbon atoms am.

Thereafter, a purge gas (eg, an inert gas such as Ar) is supplied to the inside of the chamber to remove or purify the non-adsorbed surface protection material or by-product.

Thereafter, the substrate is exposed to the metal precursor supplied to the inside of the chamber, and the metal precursor is adsorbed on the surface of the substrate. The metal precursor may be a group III such as Al.

In addition, the metal precursor may be represented by the following <Formula 3>.

<Formula 3>

In <Formula 3>, 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 having 1 to 6 carbon atoms, or a cycloamine group having 1 to 6 carbon atoms.

For example, the above-described surface protection material is more densely adsorbed from the upper portion of the structure than the lower portion, and the metal precursor cannot be adsorbed at the position where the surface protection material is adsorbed. That is, the conventional metal precursor was densely adsorbed from the upper portion of the structure to the lower portion and exhibited a high density. may be uniformly adsorbed to the upper/lower portions of the structure without being over-adsorbed on the upper portion of the structure, and may improve the step coverage of the thin film, which will be described later.

Thereafter, a purge gas (eg, an inert gas such as Ar) is supplied to the inside of the chamber to remove or purify the non-adsorbed metal precursor or by-product.

Thereafter, the substrate is exposed to the reactant supplied into the chamber, and a thin film is formed on the surface of the substrate. The reactant material reacts with the metal precursor layer to form a thin film, and the reactant material may be O3, O2, or H2O gas, and a metal oxide layer may be formed through the reactant material. In this case, the reactant oxidizes the adsorbed surface protection material, and is removed from the surface of the substrate.

Thereafter, a purge gas (eg, an inert gas such as Ar) is supplied to the inside of the chamber to remove or purify the non-adsorbed surface protection material/reacted material or by-product.

On the other hand, although it has been described that the surface protection material is supplied before the metal precursor, otherwise, the surface protection material may be supplied after the metal precursor or both before and after the metal precursor.

- Comparative Example

An aluminum oxide film was formed on the silicon substrate without using the surface protection material described above. An aluminum oxide film was formed through the ALD process, the ALD process temperature was 50 to 500 °C, and O3 gas was used as the reactant.

The aluminum oxide film formation process through the ALD process is as follows, and the following process was performed as one cycle.

1) Using Ar as a carrier gas, the aluminum precursor TMA (Trimethylaluminium) is supplied to the reaction chamber at room temperature and the aluminum precursor is adsorbed on the substrate

2) Removal of unadsorbed aluminum precursors or by-products by supplying Ar gas into the reaction chamber

3) Form a monolayer by supplying O3 gas to the reaction chamber

4) Removal of unreacted substances or by-products by supplying Ar gas into the reaction chamber

The thickness of the aluminum oxide film obtained by the above process was measured using an ellipsometer.

- Example 1

An aluminum oxide film was formed on a silicon substrate using CPME (Cyclopentyl methyl ether) as a surface protection material. An aluminum oxide film was formed through an ALD process, and the ALD process temperature was 50 to 500° C., and O3 was used as a reaction material.

The aluminum oxide film formation process through the ALD process is as follows, and the following process was performed as one cycle (refer to FIGS. 1 and 2).

1) Adsorbed to the substrate by supplying a surface protection material in the reaction chamber

2) Removal of non-adsorbed surface protection materials or by-products by supplying Ar gas into the reaction chamber

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

4) Removal of unadsorbed aluminum precursors or by-products by supplying Ar gas into the reaction chamber

5) Form a monolayer by supplying O3 gas to the reaction chamber

6) Removal of unreacted substances or by-products by supplying Ar gas into the reaction chamber

The thickness of the aluminum oxide film obtained by the above process was measured using an ellipsometer.

- Example 2

An aluminum oxide film was formed on a silicon substrate using Anisole as a surface protection material. An aluminum oxide film was formed through an ALD process, and the ALD process temperature was 50 to 500° C., and O3 was used as a reaction material.

The aluminum oxide film formation process through the ALD process is as follows, and the following process was performed as one cycle (refer to FIGS. 1 and 2).

1) Adsorbed to the substrate by supplying a surface protection material in the reaction chamber

2) Removal of non-adsorbed surface protection materials or by-products by supplying Ar gas into the reaction chamber

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

4) Removal of unadsorbed aluminum precursors or by-products by supplying Ar gas into the reaction chamber

5) Form a monolayer by supplying O3 gas to the reaction chamber

6) Removal of unreacted substances or by-products by supplying Ar gas into the reaction chamber

The thickness of the aluminum oxide film obtained by the above process was measured using an ellipsometer.

3 is a graph showing the GPC of the aluminum oxide film according to Comparative Examples and Examples 1 and 2 of the present invention according to the process temperature. As shown in FIG. 3 , an ideal ALD behavior was exhibited with little change in GPC according to an increase in the temperature of the substrate within a temperature range of 50 to 500° C. of the substrate.

In addition, as compared with Comparative Example 1, it can be seen that the GPC is reduced in Examples 1 and 2 using the surface protection material. This is thought to allow the formation of a thin film with good step coverage on the structure by preventing the adsorption of the metal precursor, which is a subsequent process, in a state in which the surface protection material is adsorbed at a higher density than the lower portion of the structure.

4 is a graph showing Secondary Ion Mass Spectroscopy (SIMS) for analyzing the surface of an aluminum oxide film according to a comparative example of the present invention, and FIG. 5 is an aluminum oxide film according to Example 1 of the present invention. This is a graph showing the secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectroscopy) for surface analysis. In both Comparative Examples and Examples, it was confirmed that no impurities (eg, carbon atoms) remained in the oxide film.

In conclusion, the surface protection material exhibits a high GPC reduction effect through its high adsorption performance, thereby enabling step coverage control as well as improving the electrical characteristics and reliability of the device. In addition, it is possible to form a thin film with high purity without impurities thinner than the thickness of one monolayer obtainable by the conventional ALD process.

Although the present invention has been described in detail through examples above, other types of embodiments are also possible. Therefore, the spirit and scope of the claims set forth below are not limited to the embodiments.

Claims (6)

In the method of forming a thin film using a surface protection material having an asymmetric ether group,
A metal precursor supply step of supplying a metal precursor to the inside of the chamber on which the substrate is placed, and adsorbing the metal precursor to the substrate;
purging the interior of the chamber; and
A thin film forming step of supplying a reactant to the inside of the chamber to react with the adsorbed metal precursor to form a thin film,
The method before the thin film forming step,
a surface protection material supplying step of supplying the surface protection material and adsorbing the surface protection material to the substrate; and
The method of forming a thin film using a surface protection material, further comprising purging the inside of the chamber. According to claim 1,
The surface protection material is represented by the following <Formula 1>, a method of forming a thin film using a surface protection material.
<Formula 1>

In the <Formula 1>, n = an integer of 0 to 10,
R1 is each independently selected from an alkyl group having 1 to 10 carbon atoms or hydrogen,
R2 is an alkyl group having 1 to 10 carbon atoms. According to claim 1,
The surface protection material is represented by the following <Formula 2>, a method of forming a thin film using a surface protection material.
<Formula 2>

In <Formula 2>, n = an integer of 1 to 10, m = an integer of 0 to 10,
R1 is each independently selected from an alkyl group having 1 to 10 carbon atoms or hydrogen,
R2 is an alkyl group having 1 to 10 carbon atoms. According to claim 1,
The reaction material is any one of O3, O2, H2O, a method of forming a thin film using a surface protection material. According to claim 1,
The metal precursor is a trivalent metal including Al, a thin film forming method using a surface protection material. According to claim 1,
The metal precursor is represented by the following <Formula 3>, a method of forming a thin film using a surface protection material.
<Formula 3>

In the <Formula 3>,
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 having 1 to 6 carbon atoms, or a cycloamine group having 1 to 6 carbon atoms.

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