WO2006054854A1 - A method for depositing thin film using ald - Google Patents

Abstract

Provided is a method for depositing a thin film using atomic layer deposition (ALD). The method includes a cycle repeatedly performed, wherein the cycle includes the operations: primary feeding g a first reaction source into a chamber in which a substrate is received; primary purging the first reaction source from the chamber; secondary feeding a second reaction source into the chamber; and secondary purging the second reaction source which does not react with the first reaction source or a by-product generated when the second reaction source reacts with the first reaction source, from the chamber, wherein, when at least one of the primary purging operation and the secondary purging operation is performed, plasma is applied into the chamber.

Description

Description

A METHOD FOR DEPOSITING THIN FILM USING ALD

Technical Field

[1] The present invention relates to a method for depositing a thin film using atomic layer deposition (ALD).

Background Art

[2] In a method for depositing a thin film using atomic layer deposition(ALD), different types of reaction sources are alternately fed and purged into a chamber in which a substrate is received, so that a thin film is deposited on the substrate in atomic layer units. At an initial stage of development of the method for depositing a thin film using ALD, the substrate is usually heated above several hundreds of temperature so that de¬ composition energy is applied to the reaction source.

[3] However, when the substrate is heated at a high temperature, due to a change of characteristics of the thin film that forms a transistor, the characteristics of the transistor such as a change of a take-off voltage or an increase in leakage current may be changed. In addition, a problem that the characteristics of the thin film are changed due to crystallization of the deposited thin film caused by a high temperature occurs.

[4] Thus, in order to reduce a deposition temperature and deposit different types of thin films, metalorganic chemical vapor deposition(MOCVD) or metalorganic atomic layer deposition (MOALD) using a metalorganic precursor as a reaction source has been developed. However, since the metalorganic precursor usually has a low vapor pressure and a large molecular size, the number of deposition of the substrate per unit time is small and there is a limitation in applying a high temperature to deposition. Thus, a method of lowering a deposition temperature and improving a deposition speed by applying subsidiary energy to help decomposition of the reaction source has been studied.

[5] As a result of the study, when depositing a thin film, plasma-enhanced atomic layer deposition (PEALD) or plasma-assisted ALD (PAALD) in which plasma as subsidiary energy is applied into the chamber, has been developed. Referring to FIG. 1, PEALD or PAALD is a method by which, in a method for depositing a thin film using ALD, the method including: a primary feeding operation (Sl) of feeding a first reaction source into the chamber in which the substrate is received; a primary purging operation (S2) of purging the first reaction source from the chamber; a secondary feeding operation (S3) of feeding a second reaction source; and a secondary purging operation (S4) of purging the second reaction source that does not react with the first reaction source, or a generated by-product, the operations are repeatedly performed as one cycle several times, while the primary feeding operation (Sl) and/or the secondary feeding operation (S3) is performed, a first plasma- applying operation (Sl') or a second plasma-applying operation (S3') of applying plasma into the chamber is performed so that the decomposition of the reaction source can be performed well.

[6] However, the plasma applied into the chamber causes the reaction source to be decomposed inside the chamber formed above the surface of the substrate so that CVD characteristics rather than complete ALD characteristics are usually shown.

[7] In addition, when plasma is initially applied into the chamber, the plasma is in an unstable state. Thus, the decomposition of the reaction source is not uniformly performed. As such, the characteristics of the thin film are degraded.

Disclosure of Invention

Technical Solution

[8] The present invention provides a method for depositing a thin film using atomic layer deposition (ALD) by which a reaction source is not decomposed inside a chamber excluding the surface of a substrate so that perfect ALD thin film deposition can be performed.

[9] The present invention also provides a method for depositing a thin film using ALD by which, even when plasma is in an unstable state when plasma is initially applied into a chamber, the characteristics of the thin film deposited on the substrate are prevented from being degraded.

[10] According to an aspect of the present invention, there is provided a method for depositing a thin film using atomic layer deposition (ALD), the method including a cycle repeatedly performed, wherein the cycle includes the operations: primary feeding a first reaction source into a chamber in which a substrate is received; primary purging the first reaction source from the chamber; secondary feeding a second reaction source into the chamber; and secondary purging the second reaction source which does not react with the first reaction source or a by-product generated when the second reaction source reacts with the first reaction source, from the chamber, wherein, when at least one of the primary purging operation and the secondary purging operation is performed, plasma is applied into the chamber.

[11] The primary purging operation may include one or at least two or more primary sub-purging operations, and the plasma is applied into the chamber when the primary sub-purging operation is performed.

[12] The secondary purging operation may include one or at least two or more secondary sub-purging operations, and the plasma is applied into the chamber when the secondary sub-purging operation is performed.

Description of Drawings

[13] FIG. 1 is a graph showing a process sequence of a conventional method for depositing a thin film using atomic layer deposition (ALD);

[14] FIG. 2 is a graph showing a process sequence of a method for depositing a thin film using ALD according to an embodiment of the present invention; and

[15] FIG. 3 is a graph showing a process sequence of a method for depositing a thin film using ALD according to another embodiment of the present invention.

Mode for Invention

[16] Hereinafter, a method for depositing a thin film using atomic layer deposition

(ALD) according to the present invention will be described with reference to the ac¬ companying drawings.

[17] The method for depositing a thin film using ALD includes a cycle, the cycle comprising the operations: primary feeding; primary purging; secondary feeding; and secondary purging. The cycle is repeatedly performed so that the thin film is deposited on the substrate. At this time, plasma is applied into the chamber while at least one of the primary purging operation and the secondary purging operation is performed. This will now be described in details.

[18] FIG. 2 is a graph showing a process sequence of a method for depositing a thin film using ALD according to an embodiment of the present invention. Referring to FIG. 2, the method for depositing a thin film using ALD includes a cycle, the cycle comprising the operations: a primary feeding operation (Sl) of feeding a first reaction source into a chamber in which a substrate is received; a primary purging operation (S2) of purging the first reaction source from the chamber; a secondary feeding operation (S3) of feeding a second reaction source into the chamber; and a secondary purging operation (S4) of purging the second reaction source which does not react with the first reaction source or a by-product generated when the second reaction source reacts with the first reaction source, from the chamber. The cycle is repeatedly performed so that the thin film is deposited on the substrate. When one cycle is performed along the above- described process sequence, a 1 -atomic layer or 1-molecualr layer is formed on the substrate. At this time, an inert gas such as Ar or N is used as a gas for purging the chamber.

[19] At this time, while at least one of the primary purging operation (S2) and the secondary purging operation (S4) is performed, the operation of applying plasma into the chamber is performed. In the present embodiment, the plasma-applying operation includes: a primary plasma- applying operation (S2') performed simultaneously with the primary purging operation (S2) and a secondary plasma-applying operation (S4') performed simultaneously with the secondary purging operation (S4).

[20] The first reaction source and the second reaction source may be a liquid source such as TMA, TEMAHf, TEMASi, or PET, or gas used in ALD, for example, NH , H , SiH , and SiH Cl .

2 2 [21] FIG. 3 is a graph showing a process sequence of a method for depositing a thin film using ALD according to another embodiment of the present invention. Referring to FIG. 3, the method for depositing a thin film using ALD includes a cycle, the cycle comprising the operations: a primary feeding operation (Sl) of feeding a first reaction source into a chamber in which a substrate is received; a primary purging operation (S2) of purging the first reaction source from the chamber; a secondary feeding operation (S3) of feeding a second reaction source into the chamber; and a secondary purging operation (S4) of purging the second reaction source which does not react with the first reaction source or a by-product generated when the second reaction source reacts with the first reaction source, from the chamber. The cycle is repeatedly performed so that the thin film is deposited on the substrate. When one cycle is performed along the above-described process sequence, a 1 -atomic layer or 1-molecualr layer is formed on the substrate. At this time, an inert gas such as Ar or N is used as a gas for purging the chamber.

[22] At this time, the primary purging operation includes one or at least two or more primary sub-purging operations, and plasma is applied into the chamber while the primary sub-purging operation is performed.

[23] In addition, the secondary purging operation includes one or at least two or more secondary sub-purging operations, and plasma is applied into the chamber while the secondary sub-purging operation is performed.

[24] In the present embodiment, the primary purging operation (S2) includes three primary sub-purging operations (S2a, S2b, and S2c), and the secondary purging operation (S4) includes three secondary sub-purging operations (S4a, S4b, and S4c). For example, in the first primary sub-purging operation (S2a), Ar of 500 seem is fed in the chamber, in the second primary sub-purging operation (S2b), Ar of 1000 seem is fed in the chamber, and in the third primary sub-purging operation (S2c), purging can be replaced with pumping. Besides, different combinations of operations can be made.

[25] In this case, the plasma- applying operation includes a primary plasma-applying operation (S2b') performed simultaneously with the second primary sub-purging operation (S2b), and a secondary plasma- applying operation (S4b') performed simul¬ taneously with the second secondary sub-purging operation (S4b).

[26] Here, plasma is applied when only one of the sub-purging operations is performed.

However, of course, plasma can be applied in a portion or all of the purging operations.

[27] In this way, plasma is applied during the primary purging operation and the secondary purging operation, respectively, so that the reaction source cannot be ecomposed inside the chamber excluding the surface of the substrate and the charac¬ teristics of the thin film can be prevented from being degraded caused by initial in¬ stability of plasma. [28] In this way, a time when plasma is applied proceeds not during feeding of the reaction source but during purging so that the possibility that the reaction source may be decomposed by the plasma can be minimized.

[29] In addition, since the inert gas passed through the plasma region, is excited and the excited inert gas is supplied onto the substrate, this causes the surface reaction of the reaction source performed on the substrate to activate so that a high-quality thin film can be obtained.

[30] In addition, the inert gas sprayed onto the substrate is used to remove impurity such as carbon (C) in the thin film and ultimately, to improve the characteristics of the thin film. Thus, the thin film manufactured using the method for depositing the thin film using ALD according to the present invention has a small amount of impurity such as carbon (C), and a dense thin film can be obtained.

Industrial Applicability

[31] As described above, in the method for depositing the thin film using ALD according to the present invention, plasma is applied into the chamber not in a feeding peration but in a purging operation such that the reaction source is prevented from being decomposed inside the chamber excluding the surface of the substrate, perfect ALD thin film decomposition is performed and the characteristics of the thin film are prevented from being degraded by initial instability of plasma.

[32] In addition, the inert gas is excited such that the surface reaction of the reaction source performed on the substrate is activated and the purging ability of the excited inert gas is improved. As such, purging efficiency can be improved and a high-quality thin film can be finally obtained.

[33] Furthermore, the excited inert gas is used to remove impurity such as carbon (C) in the thin film such that the characteristics of the thin film are improved.

Claims

Claims

[1] A method for depositing a thin film using atomic layer deposition (ALD), the method including a cycle repeatedly performed, wherein the cycle comprises the operations: primary feeding a first reaction source into a chamber in which a substrate is received; primary purging the first reaction source from the chamber; secondary feeding a second reaction source into the chamber; and secondary purging the second reaction source which does not react with the first reaction source or a by-product generated when the second reaction source reacts with the first reaction source, from the chamber, wherein, when at least one of the primary purging operation and the secondary purging operation is performed, plasma is applied into the chamber.

[2] The method of claim 1, wherein the primary purging operation comprises one or at least two or more primary sub-purging operations, and the plasma is applied into the chamber when the primary sub-purging operation is performed.

[3] The method of claim 1, wherein the secondary purging operation comprises one or at least two or more secondary sub-purging operations, and the plasma is applied into the chamber when the secondary sub-purging operation is performed.