WO2005112082A1

WO2005112082A1 - Cyclic pulsed two-level plasma atomic layer deposition apparatus and method

Info

Publication number: WO2005112082A1
Application number: PCT/KR2005/001382
Authority: WO
Inventors: Young Hoon Park; Hong Joo Lim; Sahng Kyoo Lee; Tae Wook Seo; Ho Seung Chang
Original assignee: Ips Ltd.
Priority date: 2004-05-18
Filing date: 2005-05-12
Publication date: 2005-11-24
Also published as: KR100469132B1; TWI263257B; TW200539297A

Abstract

Provided is a n apparatus for depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a substrate, which includes a substrate support plate loading and supporting the substrate, a reaction chamber including the substrate support plate and providing reaction space, a process gas supply and control unit supplying process gas such as source gas, reaction gas, and purge gas to the reaction chamber, a source gas supply pipe supplying the source gas from the process gas supply and control unit to the reaction chamber, a reaction gas activation unit activating the reaction gas, a reaction gas supply pipe through which the reaction gas is supplied from the process gas supply and control unit to the reaction chamber via the reaction gas activation unit, a variable RF power supply unit having a function of generating plasma having at least two-level energy intensity in the reaction chamber, and an exhaust unit purging the process gas in the reaction chamber.

Description

Description CYCLIC PULSED TWO-LEVEL PLASMA ATOMIC LAYER DEPOSITION APPARATUS AND METHOD Technical Field

[1] The present invention relates to a plasma atomic layer deposition method, and more particularly, to cyclic pulsed two-level plasma atomic layer deposition apparatus and method which can reduce a damage generating in a silicon substrate by minimizing plasma energy applied to a reaction chamber in forming a semiconductor device on the silicon substrate. Background Art

[2] As the width of a circuit line in a semiconductor is becoming ultra-narrow, there has been a need for forming a very thin film exhibiting superior characteristics at low temperature which is applied to an electrode film of a storage capacitor of a DRAM, a gate insulation film, or a copper diffusion prevention film forming part of the electrode film. In a method of forming a thin film using the chemical reactions of gaseous materials, an atomic layer deposition method, in which reaction gases are sequentially supplied and a cycle is repeated, is very useful for forming a very thin film.

[3] U.S. Patent No. 5,916,365 filed by Arthur Sherman and entitled 'Sequential Chemical Vapor Deposition' discloses a pulsed two-level plasma atomic layer deposition method in which plasma is applied at reaction gas supply cycle of an atomic layer deposition method to form a high quality thin film at low temperature. However, the patent does not suggest a method to solve a damage generated in a semiconductor substrate by plasma and problems in reliability of plasma ignition and repeatability of plasma generation.

[4] When plasma is generated in a reaction chamber where a silicon substrate is loaded in order to deposit a thin film on a surface of the substrate, semiconductor devices formed or being formed on the substrate, or the substrate, may be damaged. Thus, even if the pulsed two-level plasma atomic layer deposition method is applied at the same temperature of the substrate and the same plasma energy, when the design rule of a semiconductor circuit is tightened, since the size of the semiconductor device further decreases, a damage can be easily generated so that the characteristic of the semiconductor device is deteriorated or yield directly relating to semiconductor manufacturing costs is reduced.

[5] Korean Patent No. 10-0273473 and U.S. Patent No. 6,645,574 Bl filed by Chun- Soo Lee, et al. and entitled 'Thin Film Forming Method' And 'Method of Forming a Thin Film', respectively, disclose a chemical vapor method to provide materials under a time-division or pulse plasma environment. In the pulsed two-level plasma atomic layer deposition method according to these patents, RF power is applied as soon as reaction gas is supplied in a reaction chamber while the supply of source gas and purge gas are stopped. In a process in which the supply of the source gas and purge gas is stopped and the supply of the reaction gas starts, the pressure and temperature in the reaction chamber undergo a turbulence state. When the RF power is applied to generate plasma, the pressure and temperature in the reaction chamber becomes unstable at each time. Thus, the reliability of plasma ignition and the repeatability of generation are deteriorated.

[6] U.S. Patent No. 6,200,893 B 1 filed by Ofer Sneh and entitled 'Radical-assisted Sequential CVD' discloses a method of forming a thin film by alternately applying a molecular precursor in form of a molecule activated by radical. However, the patent does not suggest a method to solve practical problems such as the damage generated in the semiconductor substrate, the reliability of plasma ignition, and the repeatability of generation, which occur when an activation method such as use of plasma is employed. Disclosure of Invention Technical Problem

[7] To solve the above and/or other problems, the present invention provides cyclic pulsed two-level plasma atomic layer deposition apparatus and method by which a high quality thin film is formed at low temperature by applying a low plasma energy to prevent a damage to a semiconductor substrate.

[8] The present invention provides cyclic pulsed two-level plasma atomic layer deposition apparatus and method which solve problems that the characteristics of a semiconductor device are deteriorated due to a damage to the semiconductor device or circuit on a substrate or that yield directly related to the manufacturing costs of semiconductors is deteriorated.

[9] The present invention provides cyclic pulsed two-level plasma atomic layer deposition apparatus and method which minimize the intensity of plasma energy applied to a reaction chamber and adjust the time and cycle of application of plasma until the pressure and temperature in the reaction chamber become stable so that reliability of plasma ignition and the repeatability of generation of plasma are highly maintained and a high quality thin film can be formed at low process temperature, compared to the conventional methods such as a plasma enhanced chemical vapor deposition (PECVD), a cyclically pulsed plasma atomic layer deposition method, or plasma enhanced atomic layer deposition (PEALD).

[10] The present invention provides cyclic

[11] pulsed two-level plasma atomic layer deposition apparatus and method which produce a thin film having purity equal to or greater than the conventional technology and also remarkably reduce the process temperature of a substrate and plasma application energy. Technical Solution

[12] According to an aspect of the present invention, a high quality thin film can be deposited at low temperature without damaging a silicon substrate in the reaction chamber by applying a possibly lowest plasma energy by previously activating the reaction gas supplied to the reaction chamber.

[13] According to another aspect of the present invention, plasma energy having low intensity is applied to the reaction gas supplied to the reaction chamber after neutral radicals exhibiting a great chemical reactivity are generated through the reaction gas activation unit, at least the reaction gas is thermally activated, or both functions are applied. Then, a thin film having a desired thickness can be deposited at low temperature even when plasma energy having lower energy than the plasma energy in the conventional technology is applied to the reaction chamber during an atomic layer deposition process. Thus, damages generated in a semiconductor device or a circuit board can be remarkably reduced. Also, This method prevents deterioration of the characteristics of a semiconductor device having an ultra-narrow line width and improves yield very effectively.

[14] According to another aspect of the present invention, the source gas is supplied to the reaction chamber and absorbed on the substrate loaded in the reaction chamber. Then, the supply of the source gas is stopped and the source gas remaining in the reaction chamber is purged with the purge gas. In the subsequent step, the activated reaction gas is supplied to the reaction chamber and plasma is applied to the reaction chamber to make the source gas absorbed on the substrate and the reaction gas react with each other. Instead of purging the source gas remaining in the reaction chamber by supplying the purge gas, the activated reaction gas is directly supplied to the reaction chamber to purge the source gas. Here, the source gas remaining in the reaction chamber is purged by supplying the purge gas or directly purged by the reaction gas supplied to the reaction chamber through the reaction gas activation unit. However, during the switching process of the gases, a turbulence state of pressure and temperature in the reaction chamber is generated. To avoid the turbulence state, after the pressure and temperature in the reaction chamber are stabilized after the supply of the activated reaction gas starts, plasma energy is applied to the reaction chamber. By doing so, the reliability of plasma ignition and the repeatability of plasma generation are remarkably improved. Since the turbulence state of the temperature in the reaction chamber is relatively quickly stabilized than the turbulence state of the pressure and the influence by the local transient state of the temperature on the plasma ignition and generation is weaker than that by the local state of the pressure, the stable state of the pressure only needs to be considered. Description of Drawings

[15] FIG. 1 is a flow chart for explaining a cyclic pulsed two-level plasma atomic layer deposition method according to an embodiment of the present invention ;

[16] FIG. 2 is a view schematically illustrating an apparatus for implementing the cyclic pulsed two-level plasma atomic layer deposition method according to the present invention ;

[17] FIG. 3 is a graph showing a process order of a reaction gas supply cycle by time to implement the cyclic pulsed two-level plasma atomic layer deposition method according to the present invention ;

[18] FIG. 4 is a graph showing an example of an unstable state of pressure in a reaction chamber in the process of FIG. 3; and

[19] FIG. 5 is a graph showing an example of indicating the intensity of a two-level RF power to apply two-level plasma to the reaction chamber in the process of FIG. 3. Mode for Invention

[20] A silicon substrate 218 is loaded on a substrate support plate 212 in a reaction chamber 200. In Step 1 (101 and 301 A), source gas including an element 'a' is supplied to the reaction chamber 200 through a source gas supply pipe 220 to be absorbed on the silicon substrate 218. Simultaneously, first plasma G (30001C, 3002C, and 3003C) is applied to the reaction chamber 200. According to the present invention, in Step 1, a first application cycle 3001C of the first plasma G can be skipped, that is, the application of plasma can be made from the next step, that is, Step 2 (102 and 302A) by skipping the plasma application cycle 3001C of the first plasma G. In FIG. 5, the first plasma G changes to a first plasma G ø (3002C and 3003C).

[21] In Step 2 (102 and 302A), the source gas remaining in the reaction chamber 200 without being absorbed on the silicon substrate 218 is purged through an exhaust unit 208 using the purge gas. Simultaneously, the first plasma G or the first plasma G ø is continuously applied to the reaction chamber 200. The purge gas is supplied using the source gas supply pipe 220, reaction gas supply pipes 222A and 222B, or a separate supply pipe (not shown).

[22] According to the present invention, in Step 2, the first application cycle 3001C and the second application cycle 3002C of the first plasma G can be skipped, that is, the application of plasma can be made from the next step, that is, Step 3 (103 and 303 A) by skipping the plasma application cycles 3001C and 3002C of the first plasma G.

[23] In FIG. 5, the first plasma G is changed to the first plasma G " . In Step 3 (103 and 303 A), reaction gas including an element 'b' is passed through the reaction gas supply pipes 222A and 222B and a reaction gas activation unit 206 and then is supplied to the reaction chamber 200 so that the first part of the deposition process in which an 'a' or 'ab' thin film is formed is performed. In the first part of the deposition process, the reaction gas activated by the reaction gas activation unit 206 and the source gas absorbed on the silicon substrate 218 perform a deposition reaction with the assistance of the first plasma G. Simultaneously, the first plasma G(the first plasma G ø or the first plasma G " ) is continuously applied to the reaction chamber 200. In an example of forming an 'a' thin film instead of an 'ab' thin film, for example, when the element 'a' is titanium (Ti), the source gas is titanium chloride (TiCl ), the element 'b' is hydrogen 4 (H), and the reaction gas is hydrogen (H ) gas, the formed thin film is a titanium thin film including a titanium element. Step 3 is a cycle in which the pressure state of the reaction gas supplied to the reaction chamber 200 is mainly settled.

[24] In Step 4 (104 and 304A), while the reaction gas including the element 'b' passed through the reaction gas activation unit 206 is continuously supplied to the reaction chamber 200, the second plasma 3004C is applied in the reaction chamber 200 so that plasma ions and radicals are generated. Accordingly, the second part of the deposition process in which the 'a' or 'ab' thin film is deposed is performed. However, when the source gas does not react, or hardly react, with the activated reaction gas in the reaction chamber 200 without the assistance of plasma, Step 2 (102 and 302A) is skipped so that the remaining source gas in the reaction chamber 200 can be purged with the purge gas.

[25] Finally, in Step 5 (105 and 305 A), the supply of the reaction gas and the application of the second plasma are stopped at a process time point t5 and the reaction gas remaining in the reaction chamber 200 is purged with the purge gas through the exhaust unit 208. Simultaneously, the first plasma H (3005C)is applied to the reaction chamber 200. By continuously supplying the purge gas supplied in Step 2 until Step 5 is completed, as described above, the role of purging in Steps 2 and 3 is performed. Also, by continuously supplying the purge gas and performing supply and the discontinuation of supply only in Steps 2 and 4, the source gas and the reaction gas remaining in the reaction chamber 200 can be purged.

[26] To form a desired thickness of a thin film, the above-described Step 1 though Step 5 are repeated by a desired number of N times. In the above process, the source gas, the reaction gas, and the purge gas are referred to as process gas.

[27] FIG. 2 shows the configuration of a thin film deposition apparatus for implementing the present invention. The thin film deposition apparatus includes the reaction chamber 200 providing space where the thin film deposition process is directly performed, a process gas supply and control unit 210 supplying the process gas such as the source gas, the reaction gas, and the purge gas, the reaction gas activation unit 206 for activating the reaction gas in advance, the exhaust unit 208, an RF power generation unit 204 and a matcher 202 for applying plasma to the reaction chamber 200, the source gas supply pipe 220 connecting the process gas supply and control unit 210 and the reaction chamber 200 to supply the source gas to the reaction chamber 200, the reaction gas supply pipes 222A and 222B connecting the process gas supply and control unit 210 and the reaction gas activation unit 206 to the reaction chamber 200 to supply the reaction gas, and an exhaust pipe 226 connecting the reaction chamber 200 and the exhaust unit 208 to purge the process gas in the reaction chamber 200.

[28] Referring to FIGS. 2, 3, 4, and 5, the substrate supporting platform 212 on which the silicon substrate or wafer 218 can be loaded is installed in the reaction chamber 200. The RF power generation unit 204 and the matcher 202 for applying RF power to apply plasma to the reaction chamber 200 are connected to the reaction chamber 200. The RF power generation unit 204 and the matcher 202 together are referred to as an RF power supply unit and can control the intensity of plasma energy. A ground 214 that is one of electrodes can be connected to the substrate supporting platform 212 installed in the reaction chamber 200 or separately installed in the reaction chamber 200 which is not shown herein.

[29] The plasma applied to the reaction chamber 200 is divided into two groups of the first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C), and the second plasma (3004C). The first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C) are plasma having a relatively lower energy intensity and continuously applied to the reaction chamber 200 during the cycles of Step 1 (101 and 301A), Step 2 (102 and 302A), Step 3 (103 and 303A), and Step 5 (105 and 305A). The second plasma (3004C) is plasma having a relatively higher energy intensity than those of the first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C) and continuously applied to the reaction chamber 200 during the cycle of only Step 4 (104 and 304A) to make the source gas and the reaction gas react with each other. In order to generate plasmas having two different energy intensities, two independent RF power supply units may be used or a single RF power supply unit may be used and controlled to variably apply plasmas having two different energy intensities according to the process cycles. By using the two-level plasma and the reaction gas activation unit, while the thin film deposition reaction temperature is lowered and a damage to the substrate due to the plasma is reduced, a high quality thin film can be formed and the reliability of plasma ignition and the repeatability of the plasma generation can be improved.

[30] The process gas supply and control unit 210 for controlling the supply of the process gas is connected to the reaction chamber 200 through the source gas supply pipe 220. The process gas supply and control unit 210 and the reaction chamber 200 are connected via the reaction gas activation unit 206 and the reaction gas supply pipe 222A and 222B so that the reaction gas is supplied to the reaction chamber 200 after being activated. The process gas supply and control unit 210 can be configured to be able to supply and control of the purge gas. Typically, the purge gas is supplied to the reaction chamber 200 using an additional supply pipe (not shown). The reaction gas activation unit 206 for activating the reaction gas is connected between the reaction gas supply pipes 222A and 222B. The reaction gas activation unit 206 may be configured to have a reaction gas activation function simply by heat or a reaction gas activation function by plasma, or both functions. The heat or plasma energy sources needed for activation can be configured to be a variable type. The exhaust unit 208 for exhausting the process gas is connected to the reaction chamber 200 through the exhaust pipe 226.

[31] According to the present invention, as described above, the process temperature can be lowered and a damage generated in the substrate can be remarkably reduced by lowering the intensity of plasma energy applied to the substrate in the reaction chamber. For example, in the process of performing Step 4 (104 and 304A) in FIGS. 1 and 3, as the second plasma (3004C) is supplied by lowering the energy intensity thereof by 1/3 through 1/2 compared to the conventional technology, the damage to the substrate by the plasma can be remarkably reduced. The energy intensities of the first plasma G (3001A, 3002C, and 3003C) and the first plasma H (3005C) are made to be not more than 1/2 of the energy intensity of the second plasma (3004C).

[32] The source gas typically includes a metal element. In detail, in order to implement the thin film deposition process, for example, to form a nitride thin film, the reaction gas must includes nitrogen. That is, when the source gas is formed to include one of compounds of titanium (Ti), tantalum (Ta), or tungsten (W) metals and the reaction gas is formed by one of nitrogen (N ), ammonia (NH ), or hydrazine (N H ) gases, nitride thin films such as titanium nitride (TiN), tantalum nitride (TaN), or tungsten nitride (WN) are formed.

[33] In another example of the present invention, the reaction gas is formed of a mixture of a gas including the element 'b' and hydrogen (H ) gas. That is, the reaction gas may be formed of a mixture of nitrogen (N ) gas and hydrogen (H ) gas, a mixture of ammonia (NH ) and hydrogen (H ) gas, or a mixture of hydrazine (N H ) gas and hydrogen (H ) gas. In Steps 3 and 4, NH, NH , or H radicals are supplied onto the silicon substrate 218 so that a metal nitride thin film is formed. Also, when the reaction gas is formed of a gas including oxygen (O ) or a mixture of the gas including oxygen (O ) gas and hydrogen (H ) gas, an oxide thin film is formed. When the reaction gas is formed to include hydrogen (H ) gas, since the metal compound of the source gas is deoxidized in Steps 3 and 4, a metal thin film is formed. [34] The configuration and operation principle of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are mere examples of the present invention to help those skilled in the art understand the basic principle of the present invention. Thus, it should be noted that the present invention is not limited to the following embodiments and a variety of modifications and applications of the following embodiments are available.

[35] [First embodiment]

[36] As shown in the flow chart of FIG. 1, the process of forming the thin film including the elements 'a' and 'b' on the surface of the silicon substrate 218 loaded on the substrate supporting platform 212 installed in the reaction chamber 200 is formed in the cyclic pulsed two-level plasma atomic layer deposition method according to the present invention. FIG. 2 shows the concept of a cyclic pulsed two-level plasma atomic layer deposition apparatus to implement the present invention.

[37] Referring to FIGS. 1, 2, 3, 4, and 5, in Step 1 (101 and 301A), the source gas including the element 'a' is supplied to the reaction chamber 200 through the source gas supply pipe 220 to be absorbed on the surface of the silicon substrate 218. Simultaneously, the application of the first plasma G (3001A, 3002C, and 3003C) to the reaction chamber 200 is initiated.

[38] In Step 2 (102 and 302A), the supply of the source gas is stopped and the purge gas is supplied to the reaction chamber 200 so that the source gas remaining in the reaction chamber 200 without being absorbed on the silicon substrate 218 is purged. Argon (Ar), helium (He), nitrogen (N ), or hydrogen (H ) gas is used as the purge gas. Simultaneously, the first plasma G (3001C, 3002C, and 3003C) are continuously applied.

[39] In Step 3 (103 and 303 A), the supply of the purge gas is discontinued and the reaction gas including the element 'b' is supplied to the reaction chamber 200 through the reaction gas supply pipes 222A and 222B. The reaction gas supplied to the reaction chamber 200 passes through the reaction gas activation unit 206. Here, radicals are picked up by means of a plasma generation function in the reaction gas activation unit 206. The reaction gas may be thermally activated in the reaction gas activation unit 206 or by the above-mentioned two functions. Simultaneously, the first plasma G (3001C, 3002C, and 3003C) is continuously applied during the process cycle of Step 3. At this time, the first part of the deposition process takes place, that is, a deposition reaction occurs on the substrate as the source gas absorbed on the substrate in the reaction chamber 200 reacts with the reaction gas supplied to the reaction chamber 200 with the assistance of the first plasma G applied to the reaction chamber 200. Simultaneously, during this process cycle, the turbulence state of pressure generated when the reaction gas is supplied to the reaction chamber 200 is stabilized.

[40] In Step 4 (104 and 304A), the reaction gas including the element 'b' is continuously supplied to the reaction chamber 200. The second plasma (3004C) having energy intensity greater than that of the first plasma G is applied to the reaction chamber 200. Since the pressure of the reaction gas in the reaction chamber at this time is already stable, the thin film deposition process is actively performed with the assistance of the second plasma applied to the reaction chamber 200 so that an 'a' or 'ab' thin film is formed on the silicon substrate 218. Furthermore, the second part of the deposition process is performed which is a thin film deposition phenomenon actively occurring as not only the ions and radicals gained when the reaction gas supplied onto the substrate passes through the reaction gas activation unit 206 but also the ions and radicals generated by the second plasma having high energy intensity applied to the reaction chamber 200 are mixed.

[41] In Step 5 (105 and 305 A) that is a final process cycle, the supply of the reaction gas and the application of the second plasma are discontinued. The reaction gas remaining in the reaction chamber 200 is purged by the purge gas. In general, since a layer of the thin film formed in the above-described atomic layer deposition method is too thin although having a high quality, to obtain a thin film having a desired thickness, Step 1 through Step 5 are repeated by a desired number of N times.

[42] According to the above-described first embodiment of the present invention, since the intensity of the plasma energy applied to the reaction chamber 200 is reduced by 1/2 through 1/2 using the thin film deposition apparatus according to the present invention, the damage to the substrate due to the second plasma applied to the reaction chamber 200 can be remarkably reduced. Also, since the point of the process cycle for applying the plasma to the reaction chamber 200 in Step 3 is delayed later than the point of the process cycle of supplying the activated reaction gas until the pressure in the reaction chamber 200 is stabilized, the reliability of ignition of the second plasma and the repeatability of generation of the second plasma are gradually improved.

[43] Since, during the above process cycles, the influence by a turbulence state in temperature in the reaction chamber 200 on the reliability of ignition of the second plasma and the repeatability of generation of the second plasma is relatively smaller than that by the turbulence state in pressure, in the present embodiment, only instability of the plasma due to the turbulence state in pressure generated in the reaction chamber 200 is considered. Physically, the turbulence state in temperature is stabilized more quickly than the turbulence state in pressure.

[44] [Second embodiment]

[45] In this second embodiment, the process cycles performed in the first embodiment are repeated while only the process of applying plasma applied to the reaction chamber 200 is different. That is, referring to FIGS. 1, 2, 3, 4, and 5, according to a second embodiment of the present invention, in Step 1 (101 and 301 A), the source gas including the element 'a' is supplied to the reaction chamber 200 via the source gas supply pipe 220 to be absorbed on the surface of the silicon substrate 218. In Step 2 (102 and 302A), the supply of the source gas is stopped and the purge gas is supplied to the reaction chamber 200 so that the source gas remaining in the reaction chamber 200 without being absorbed on the substrate is purged. Argon (Ar), helium (He), nitrogen (N ), or hydrogen (H ) gas is used as the purge gas. In Step 3, (103 and 303 A), the supply of the purge gas is stopped and the reaction gas including the element 'b' is supplied to the reaction chamber 200 through the reaction gas supply pipes 222A and 222B. The reaction gas supplied to the reaction chamber 200 passes through the reaction gas activation unit 206. In doing so, radicals are picked up by the plasma in the reaction gas activation unit 206, the reaction gas is thermally activated in the reaction gas activation unit 206, or the reaction gas is activated by these two processes.

[46] The first plasma G (3001C, 3002C, and 3003C) is continuously applied to the reaction chamber 200 during the process cycles of Step 1 through Step 3. The first part of the deposition process is performed by the first plasma G in Step 3 and simultaneously the turbulence state in the pressure of the reaction gas in the reaction chamber 200 is stabilized. In Step 4 (104 and 304A), the reaction gas including the element 'b' is continuously supplied to the reaction chamber 200 through the reaction gas supply pipes 222A and 222B. Simultaneously, the second plasma (3004C) is applied to the reaction chamber 200. Since the pressure of the reaction gas in the reaction chamber 200 is already stabilized, the thin film deposition phenomenon is actively performed on the substrate between the source gas absorbed on the substrate and the reaction gas so that the 'a' or 'ab' thin film is formed on the silicon substrate 218. The deposition reaction is actively performed not only by the mixture of the ions and the radicals gained while the reaction gas in the reaction chamber 200 passes through the reaction gas activation unit 206, but also by the ions and the radicals generated by the second plasma (3004C) applied to the reaction chamber 200, so that the second part of the deposition process is performed. The first plasma G (3001A, 3003B, and 3003C) and the first plasma H (3005C) directly or indirectly contribute to the deposition reaction between the source gas and the reaction gas.

[47] Referring to FIG. 5, the plasma applied to the reaction chamber 200 is plasma (3001C, 3002C, 3003C, 3004C, and 3005C) having two-step energy intensity. The first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C) have the same energy intensity which is about 1/2 of that of the second plasma (3004C). The energy intensity of the second plasma (3004C) is 1/3 through 1/2 of the conventional technology. In Step 5 (105 and 305 A), the supply of the reaction gas is stopped at the initial stage of the process cycle t5 and the application of the second plasma is turned off. Also, by supplying the purge gas, the reaction gas remaining in the reaction chamber 200 is purged. Simultaneously, the first plasma H (3005C) is continuously applied to the reaction chamber 200. Finally, to obtain a thin film having a desired thickness, Step 1 through Step 5 are repeated by a desired number of N times.

[48] As described above, the plasma energy applied to the reaction chamber 200 is applied in two steps of the first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C), and the second plasma (3004C). The energy intensity of the first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C) are the same and applied to the reaction chamber 200 throughout Step 1 (101 and 301A), Step 2 (102 and 302A), Step 3 (103 and 303A), and Step 5 (105 and 305A). The application of the first plasma G (3001C, 3002C, and 3003C) may start from the point tl of Step 1 (101 and 301 A) or the point t2 of Step 2 (102 and 302A), in which the first plasma G (3001C, 3002C, and 3003C) changes to the first plasma G ø (3002C and 3003C) (not shown). Also, the application of the first plasma G (3001C, 3002C, and 3003C) may start from the point t3 of Step 3 (103 and 303 A), in which the first plasma G (3001C, 3002C, and 3003C) changes to the first plasma G ² (3003C) (not shown).

[49] In the present embodiment, the energy intensity of the second plasma (3004C) is about 1/3 through 1/2 of the conventional technology and applied only in Step 4 (104 and 304A) in which the reaction gas is supplied and stabilized. The first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C) are continuously applied except for Step 4 (104 and 304A). However, when the first plasma G ø (3002C and 3003C) and the first plasma G ² (3003C) are applied, the non-corresponding plasma application cycle is omitted. The plasma energy application unit in the reaction chamber 200 may include two pairs of independent electrodes, or it may be possible to include a single pair of electrodes and control the plasma energy intensity and the application timing. As the first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C) are applied, the reliability of ignition of the second plasma 3004C and the repeatability of the generation of the second plasma 3004C are improved. The first plasma G' (3002C and 3003C) and the first plasma G" (3003C) may be applied. Furthermore, as described above, after the pressure turbulence state in the reaction chamber is stabilized by the process cycle of Step 3 (103 and 303 A), the second plasma (3004C) is applied to the reaction chamber while the reaction gas is continuously supplied in Step 4 (104 and 304A). Thus, the deposition reaction is performed by the second plasma (3004C) that is a main plasma so that the reliability of ignition of the second plasma (3004C) and the repeatability of the generation of the second plasma (3004C) are further improved.

[50] In detail, as an example of the thin film deposition process, to form a nitride thin film, the process gas including nitrogen is formed as the reaction gas. That is, when the source gas is formed to include one of compounds of titanium (Ti), tantalum (Ta), or tungsten (W) metals and the reaction gas is formed by one of nitrogen (N ), ammonia (NH ), or hydrazine (N H ) gases, nitride thin films such as titanium nitride (TiN), tantalum nitride (TaN), or tungsten nitride (WN) are formed. In another example of the present invention, the reaction gas may be formed of a mixture of nitrogen (N ) gas and hydrogen (H ) gas, a mixture of ammonia (NH ) and hydrogen (H ) gas, or a mixture of hydrazine (N H ) gas and hydrogen (H ) gas. In Steps 3 and 4, NH, NH , or H radicals are supplied onto the silicon substrate 218 so that a metal nitride thin film is formed. Also, when the reaction gas is formed of a gas including oxygen (O ) or a mixture of the gas including oxygen (O ) gas and hydrogen (H ) gas, an oxide thin film is formed. When the reaction gas is formed to include hydrogen (H ) gas, since the metal compound of the source gas is deoxidized in Steps 3 and 4, a metal thin film is formed.

[51] FIG. 3 is a graph showing the process steps of Step 1 through Step 5 of the flow chart of FIG. 1 by the order of the process time. Referring to FIGS. 1, 2, 3, 4, and 5, in Step 1 (101 and 103A), the source gas is supplied to the reaction chamber 200 to be absorbed on the silicon substrate 218 loaded on the substrate support plate 212 in the reaction chamber 200. The first plasma G (3001C, 3002C, and 3003C) are applied to the reaction chamber 200. In Step 2 (102 and 302A), the purge gas is supplied to the reaction chamber 200 to purge the source gas remaining in the reaction chamber 200 without being absorbed on the silicon substrate 218 through the exhaust unit 208. As described above, the first plasma G (3001C, 3002C, and 3003C) for which application is started from Step 1 (101 and 301 A) may not be applied in Step 1 (101 and 301 A) and may be applied in Step 2 (102 and 302A) or Step 3 (103 and 303 A).

[52] When the supply of the purge gas applied to the reaction chamber 200 is stopped at the beginning of Step 3 (103 and 303 A) and the supply of the reaction gas is stated immediately, the position of a control valve in the process gas control and supply unit 210, the length of the process gas supply lines 220, 222A, and 222B, the difference in the supply line length, and the switching of the process gas cause a transient phenomenon in a pressure change in the reaction chamber 200 so that an unstable state 313B is generated. Accordingly, according to the present invention, the supply of the purge gas is not discontinued after the reaction chamber 200 is purged. Although the turbulence state 313B occurs in the reaction chamber 200 as the reaction gas is continuously supplied in Step 3 (103 and 303 A), the degree of the turbulence state is lower than a case in which the supply of the purge gas is stopped. However, according to the present invention, the supply of the purge gas can be stopped when Step 3 (103 and 303 A) begins, as in the conventional technology. When plasma is applied together with switching of the process gases supplied to the reaction chamber 200, since the pressure of the reaction chamber 200 enters in the turbulence state 313B, the intensity of the second plasma (3004C) applied to Step 4 (104 and 304A) may be instable with the change in the pressure or ignition of the second plasma may fail. According to the present invention, since the reaction gas is continuously supplied to the reaction chamber 200 in Step 4 (104, 304A, 314B, and 3004C) after the reaction gas is supplied to the reaction chamber 200 in Step 3 (103, 303A, and 313B) and thus the pressure in the reaction chamber 200 is stabilized, the ignition conduction of the second plasma (3004C) is stabilized when the second plasma (3004C) is applied without changing the flow rate of the reaction gas. Thus, the failure of the ignition is prevented so that reliability is improved. Also, when this step is repeated at every process cycle, the repeatability of the generation of the second plasma (3004C) repeated at every supply cycle of the reaction gas can be highly maintained.

[53] According to the present invention, the intensity of the RF power to apply plasma to the reaction chamber 200 is 300 through 1200 watts for the second plasma (3004C). This value varies according to the source gas, the reaction gas, and the process conditions and is about 1/3 through 1/2 of the conventional technology. The energy intensity of each of the first plasma G (3001C, 3002C, and 3003C) and the first plasma H (3005C), which is the same as that of each of the first plasma G ø and the first plasma G ² , is about 1/2 of the energy intensity of the second plasma (3004C). Thus, according to the present invention, the damage to the substrate can be remarkably reduced by the second plasma (3004C). Also, according to the present invention, the purge gas may be continuously supplied to the reaction chamber while the second plasma (3004C) is applied to the reaction chamber 200 in this process step. Finally, in Step 5 (105 and 305 A), the supply of the reaction gas is stopped and the purge gas continuously supplied purges the reaction gas remaining in the reaction chamber. When the supply of the purge gas is stopped in Step 2 (102 and 302A), the supply of the reaction gas is stopped in Step 5 (105 and 305 A) and the purge gas is supplied again to purge the reaction gas remaining in the reaction chamber 200. When the supply of the purge gas starts in Step 2 (102 and 302A), the supply of the purge gas is stopped at the point t6 of Step 5 (105 and 305 A). Otherwise, the supply of the purge gas continues.

[54] While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Industrial Applicability

[55] As described above, according to the present invention, in order to prevent a damage to the substrate by activating the reaction gas in advance, RF power which is remarkably lower than the conventional technology is applied so that a thin film is deposited. Also, by applying plasma having two different energy intensities to reduce the energy intensity of the plasma, a high quality thin film is formed at low temperature and the damage to the substrate by the plasma is remarkably reduced. That is, the reaction gas in an already activated state is supplied to the substrate and plasma having low energy intensity is continuously applied to the reaction chamber so that and a high quality thin film is formed even when the energy intensity of the plasma applied to the reaction chamber to make the reaction gas react is quite lowered. Also, by delaying the plasma application point later than the reaction gas supply point at every reaction gas supply cycle, the reliability of plasma ignition and the repeatability of plasma generation are improved. Also, the deposition of an atomic layer having high purity and high density is possible at low temperature. The present invention can prevent deterioration of the characteristics of a semiconductor device with an ultra- narrow line width and improve yield.

Claims

[1] 1. An apparatus for depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a substrate, the apparatus comprising: a substrate support plate loading and supporting the substrate; a reaction chamber including the substrate support plate and providing reaction space; a process gas supply and control unit supplying process gas such as source gas, reaction gas, and purge gas to the reaction chamber; a source gas supply pipe supplying the source gas from the process gas supply and control unit to the reaction chamber; a reaction gas activation unit activating the reaction gas; a reaction gas supply pipe through which the reaction gas is supplied from the process gas supply and control unit to the reaction chamber via the reaction gas activation unit; a variable RF power supply unit having a function of generating plasma having at least two-level energy intensity in the reaction chamber; and an exhaust unit purging the process gas in the reaction chamber.

2. The apparatus of claim 1, wherein the reaction gas activation unit comprises a plasma application function.

3. The apparatus of claim 1, wherein the reaction gas activation unit includes a function of activating through heat treatment.

4. The apparatus of claim 1, wherein the reaction gas activation unit includes functions of generating plasma and activating through heat treatment.

5. The apparatus of either claim 2 or claim 4, wherein the plasma generation function is capable of controlling intensity of RF power.

6. A method of depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a surface of a substrate in a reaction chamber, the method comprising: supplying source gas to the reaction chamber to be absorbed on the surface of the substrate loaded in the reaction chamber; applying first plasma to the reaction chamber; stopping the supply of the source gas, purging the source gas remaining in the reaction chamber without being absorbed by supplying purge gas, and continuously supplying the purge gas; passing reaction gas through a reaction gas activation unit and supplying the reaction gas to the reaction chamber; applying second plasma having energy intensity higher than the first plasma but lower than 1,200 watts to the reaction chamber after continuously supplying the activated reaction gas to the reaction chamber so that pressure in the reaction chamber is stabilized; stopping the supply of the reaction gas and the application of the second plasma, and purging the reaction gas remaining in the reaction chamber with the continuously supplied purge gas; stopping the supply of the purge gas; and repeating the above operations until a thin film having a desired thickness is formed.

7. The method of claim 6, wherein the supply of the purge gas is stopped after the source gas and the reaction gas remaining in the reaction chamber are purged by supplying the purge gas.

8. The method of claim 6, wherein the energy intensity of the first plasma applied to the reaction chamber is not more than 1/2 of that of the second plasma.

9. The method of claim 6, wherein, instead of purging the source gas remaining in the reaction chamber with the purge gas, the reaction gas is directly supplied in the subsequent step to purge the source gas remaining in the reaction chamber and simultaneously the reaction gas is supplied to the reaction chamber.

10. The method of claim 6, wherein the purge gas is selected from the group consisting of argon (Ar), helium (He), nitrogen (N ), and hydrogen (H ).

11. The method of claim 6, wherein the reaction gas comprises hydrogen element (H ).

12. A method of depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a surface of a substrate in a reaction chamber, the method comprising: supplying source gas to the reaction chamber to be absorbed on the surface of the substrate loaded in the reaction chamber; applying first plasma to the reaction chamber; stopping the supply of the source gas, purging the source gas remaining in the reaction chamber without being absorbed by supplying purge gas, and continuously supplying the purge gas; passing reaction gas including nitrogen element (N) through a reaction gas activation unit and supplying the reaction gas to the reaction chamber; applying second plasma having energy intensity higher than the first plasma but lower than 1,200 watts to the reaction chamber after continuously supplying the activated reaction gas to the reaction chamber so that pressure in the reaction chamber is stabilized; stopping the supply of the reaction gas and the application of the second plasma, and purging the reaction gas remaining in the reaction chamber with the continuously supplied purge gas; stopping the supply of the purge gas; and repeating the above operations until a nitride thin film having a desired thickness is formed.

13. The method of claim 12, wherein the supply of the purge gas is stopped after the source gas and the reaction gas remaining in the reaction chamber are purged by supplying the purge gas.

14. The method of claim 12, wherein the energy intensity of the first plasma applied to the reaction chamber is not more than 1/2 of that of the second plasma.

15. The method of claim 12, wherein, instead of purging the source gas remaining in the reaction chamber with the purge gas, the reaction gas is directly supplied in the subsequent step to directly purge the source gas remaining in the reaction chamber and simultaneously the reaction gas is supplied to the reaction chamber.

16. The method of claim 12, wherein the reaction gas is formed of a mixture of gas including nitrogen (N ) and hydrogen (H ) gas.

17. The method of claim 12, wherein the source gas is a compound of transition metal such as titanium (Ti), tantalum (Ta), or tungsten (W) and the reaction gas comprises one selected from the group consisting of nitrogen (N ), ammonia (NH ), and hydrazine N H gases, so that a deposited thin film includes a nitride of the transition metal.

18. The method of claim 12, wherein the purge gas is selected from the group consisting of argon (Ar), helium (He), nitrogen (N ), or hydrogen (H ).

19. A method of depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a surface of a substrate in a reaction chamber, the method comprising: supplying source gas to the reaction chamber to be absorbed on the surface of the substrate loaded in the reaction chamber; applying first plasma to the reaction chamber; stopping the supply of the source gas, purging the source gas remaining in the reaction chamber without being absorbed by supplying purge gas, and continuously supplying the purge gas; passing reaction gas including oxygen element (O) through a reaction gas activation unit and supplying the reaction gas to the reaction chamber; applying second plasma having energy intensity higher than the first plasma but lower than 1,200 watts to the reaction chamber after continuously supplying the activated reaction gas to the reaction chamber so that pressure in the reaction chamber is stabilized; stopping the supply of the reaction gas and the application of the second plasma, and purging the reaction gas remaining in the reaction chamber with the continuously supplied purge gas; stopping the supply of the purge gas; and repeating the above operations until an oxygen thin film having a desired thickness is formed.

20. The method of claim 19, wherein the supply of the purge gas is stopped after the source gas and the reaction gas remaining in the reaction chamber are purged by supplying the purge gas.

21. The method of claim 19, wherein the energy intensity of the first plasma applied to the reaction chamber is not more than 1/2 of that of the second plasma.

22. The method of claim 19, wherein, instead of purging the source gas remaining in the reaction chamber with the purge gas, the reaction gas is directly supplied in the subsequent step to directly purge the source gas remaining in the reaction chamber.

23. The method of claim 19, wherein the reaction gas is formed of a mixture of gas including oxygen (O ) and hydrogen (H ) gas.

24. The method of claim 19, wherein the purge gas is selected from the group consisting of argon (Ar), helium (He), nitrogen (N ), or hydrogen (H ).

25. A method of depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a surface of a substrate in a reaction chamber, the method comprising: supplying source gas to the reaction chamber to be absorbed on the surface of the substrate loaded in the reaction chamber; applying first plasma to the reaction chamber; stopping the supply of the source gas, purging the source gas remaining in the reaction chamber without being absorbed by supplying purge gas, and continuously supplying the purge gas; passing reaction gas including hydrogen element (H) through a reaction gas activation unit and supplying the reaction gas to the reaction chamber; applying second plasma having energy intensity higher than the first plasma but lower than 1,200 watts to the reaction chamber after continuously supplying the activated reaction gas to the reaction chamber so that pressure in the reaction chamber is stabilized; stopping the supply of the reaction gas and the application of the second plasma, and purging the reaction gas remaining in the reaction chamber with the continuously supplied purge gas; stopping the supply of the purge gas; and repeating the above operations until a metal thin film having a desired thickness is formed.

26. The method of claim 25, wherein the supply of the purge gas is stopped after the source gas and the reaction gas remaining in the reaction chamber are purged by supplying the purge gas.

27. The method of claim 25, wherein the energy intensity of the first plasma applied to the reaction chamber is not more than 1/2 of that of the second plasma.

28. The method of claim 25, wherein, instead of purging the source gas remaining in the reaction chamber with the purge gas, the reaction gas is directly supplied in the subsequent step to directly purge the source gas remaining in the reaction chamber.

29. The method of claim 25, wherein the purge gas is selected from the group consisting of argon (Ar), helium (He), nitrogen (N ), or hydrogen (H ).

30. A method of depositing a cyclic pulsed two-level plasma atomic layer to deposit a thin film on a surface of a substrate in a reaction chamber, the method comprising: supplying source gas to the reaction chamber to be absorbed on the surface of the substrate loaded in the reaction chamber; continuously applying first plasma to the reaction chamber before the source gas is repeatedly supplied in the subsequent process cycle except for a period in which the reaction gas is supplied to the reaction chamber; stopping the supply of the source gas, purging the source gas remaining in the reaction chamber without being absorbed by supplying purge gas, and continuously supplying the purge gas; passing reaction gas through a reaction gas activation unit and supplying the reaction gas to the reaction chamber; applying second plasma having energy intensity higher than the first plasma but lower than 1,200 watts to the reaction chamber after continuously supplying the activated reaction gas to the reaction chamber so that pressure in the reaction chamber is stabilized; stopping the supply of the reaction gas and the application of the second plasma, and purging the reaction gas remaining in the reaction chamber with the continuously supplied purge gas; stopping the supply of the purge gas; and repeating a basic process cycle formed of the above process operations by N times, where N=l, until a thin film having a desired thickness is formed.

31. The method of claim 30, wherein the energy intensity of the first plasma applied to the reaction chamber is not more than 1/2 of that of the second plasma.

32. The method of claim 30, wherein, instead of purging the source gas with the purge gas, the reaction gas is supplied in the subsequent step to directly purge the source gas remaining in the reaction chamber.

33. The method of claim 30, wherein the source gas is a metal compound and the reaction gas is formed of gas including hydrogen (H ).

34. The method of claim 30, wherein the purge gas is selected from the group consisting of argon (Ar), helium (He), nitrogen (N ), and hydrogen (H ).