Method of forming a dielectric layer having an ONO structure using an in-situ process

A method of forming a dielectric layer, the method including sequentially forming a first oxide layer, a nitride layer, and a second oxide layer on a substrate by performing a plasma-enhanced atomic layer deposition process, wherein a first nitrogen plasma treatment is performed after forming the first oxide layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2011-0063973 filed on Jun. 29, 2011 in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. 119, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND

Embodiments relate to a method of forming a dielectric layer having an oxide/nitride/oxide (ONO) structure using an in-situ process.

2. Description of the Related Art

In a flash memory device, a dielectric layer having an ONO structure may be used to separate a floating gate electrode from a control gate electrode. For example, the ONO dielectric layer may be formed by a three-step process of sequentially depositing a silicon oxide layer, a silicon nitride layer, and a silicon oxide layer on a substrate.

The silicon oxide layer and the silicon nitride layer (at the ONO dielectric layer) may be formed at different temperatures in different reactors. For example, the silicon oxide layer and the silicon nitride layer may be formed at a temperature of about 700° C. or higher.

SUMMARY

Embodiments are directed to a method of forming a dielectric layer having an oxide/nitride/oxide (ONO) structure using an in-situ process

The embodiments may be realized by providing a method of forming a dielectric layer, the method including sequentially forming a first oxide layer, a nitride layer, and a second oxide layer on a substrate by performing a plasma-enhanced atomic layer deposition process, wherein a first nitrogen plasma treatment is performed after forming the first oxide layer.

Forming the first oxide layer, the nitride layer, and the second oxide layer and performing the first nitrogen plasma treatment may be performed using an in-situ process.

During forming the first oxide layer, the nitride layer, and the second oxide layer and performing the first nitrogen plasma treatment, the substrate may be placed on a susceptor in a chamber and the susceptor may be maintained at a constant temperature.

Performing the first nitrogen plasma treatment may include performing a nitrogen plasma treatment on a surface of the first oxide layer using a gas containing nitrogen and helium.

The method may further include performing a second nitrogen plasma treatment on a surface of the nitride layer, after forming the nitride layer.

Forming the first and second oxide layers may include supplying first and second silicon precursors and oxidizing the first and second silicon precursors, respectively, by performing an oxygen plasma treatment, and forming the nitride layer may include supplying a third silicon precursor and nitridating the third silicon precursor by performing a third nitrogen plasma treatment.

The first to third silicon precursors may be the same and the first to third silicon precursors may have Si—N bonds.

A first power applied to the chamber during the first nitrogen plasma treatment may be larger than a second power applied to the chamber during the oxygen plasma treatments and the third nitrogen plasma treatment.

Performing the third nitrogen plasma treatment may include nitridating the third silicon precursor using a gas containing nitrogen and hydrogen.

The embodiments may also be realized by providing a method of forming a dielectric layer, the method including placing a substrate on a susceptor in a chamber; and sequentially forming a first oxide layer, a nitride layer, and a second oxide layer on the substrate using an in-situ process, wherein the susceptor is maintained at a constant temperature during forming the first oxide layer, the nitride layer, and the second oxide layer.

The method may further include performing a first nitrogen plasma treatment on a surface of the first oxide layer, after forming the first oxide layer.

The method may further include performing a second nitrogen plasma treatment on a surface of the nitride layer, after forming the nitride layer.

Forming the first oxide layer, the nitride layer, and the second oxide layer may include performing a plasma enhanced atomic layer deposition process, and a first power applied to the chamber during the first nitrogen plasma treatment and the second nitrogen plasma treatment may be larger than a second power applied to the chamber to form the first oxide layer, the nitride layer, and the second oxide layer.

Forming the first and second oxide layers may include supplying first and second silicon precursors and oxidizing the first and second silicon precursors, respectively, by performing oxygen plasma treatments, and forming the nitride layer may include supplying a third silicon precursor and nitridating the third silicon precursor by performing a third nitrogen plasma treatment.

The first to third silicon precursors may be the same and the first to third silicon precursors may have Si—N bonds.

The embodiments may also be realized by providing a method of forming a dielectric layer using an in-situ process, the method including forming a first oxide layer on a substrate by performing a plasma-enhanced atomic layer deposition process; performing a first nitrogen plasma treatment on the first oxide layer; forming a nitride layer on the first oxide layer by performing a plasma-enhanced atomic layer deposition process; forming a second oxide layer on the nitride layer by performing a plasma-enhanced atomic layer deposition process.

Performing the first nitrogen plasma treatment may include performing a nitrogen plasma treatment on a surface of the first oxide layer using a gas containing nitrogen and helium.

Forming the first oxide layer may include supplying a silicon precursor and oxidizing the silicon precursor by performing an oxygen plasma treatment, forming the nitride layer may include supplying the silicon precursor and nitridating the precursor by performing a third nitrogen plasma treatment, and forming the second oxide layer may include supplying the silicon precursor and oxidizing the silicon precursor by performing an oxygen plasma treatment.

Performing the third nitrogen plasma treatment may include nitridating the precursor using a gas containing nitrogen and hydrogen.

The method may further include performing a first nitrogen plasma treatment on a surface of the first oxide layer, after forming the first oxide layer; and performing a second nitrogen plasma treatment on a surface of the nitride layer, after forming the nitride layer.

DETAILED DESCRIPTION

Hereinafter, plasma deposition equipment to which a method for forming a dielectric layer according to an embodiment is applied will be described with reference toFIG. 1.FIG. 1illustrates a schematic view of plasma deposition equipment to which a method for forming a dielectric layer according to an embodiment is applied.

Referring toFIG. 1, the plasma deposition equipment100may include a chamber120having a susceptor110and a shower plate115facing the susceptor110. The susceptor110may support a substrate200while a deposition process is performed. In addition, the susceptor110may serve as a heater to maintain the substrate200at a constant temperature while performing the deposition process. The susceptor110may also serve as a lower electrode.

The shower plate115may supply gases used for forming a dielectric layer into the chamber120. Gases may be supplied from first to sixth sources140,150,160,170,180, and190to the shower plate115to then be injected into the chamber120. First to sixth valves145,155,165,175,185, and195may be controlled to determine which gas is to be injected from the first to sixth sources140,150,160,170,180, and190into the chamber120.

The plasma deposition equipment100may include a bias power unit130(that supplies bias power to the susceptor110) and a source power unit135(that supplies source power to the shower plate115). Plasma reactions of gases supplied from the first to sixth sources140,150,160,170,180, and190may be induced using the bias power unit130and the source power unit135.

In addition, the plasma deposition equipment100may include a pump125for maintaining the chamber120at a vacuum and exhausting gases remaining in the chamber120.

A method of forming a dielectric layer according to an embodiment will now be described with reference toFIGS. 1 through 13.FIG. 2illustrates a flowchart showing the method for forming a dielectric layer according to an embodiment.FIG. 3illustrates a timing diagram showing the method for forming a dielectric layer ofFIG. 2.FIGS. 4 through 13illustrate cross-sectional views showing stages in the method of forming a dielectric layer ofFIG. 2.

Referring toFIGS. 1 and 2, the substrate200may be placed in the chamber120(S100).

For example, the substrate200may be positioned on the susceptor110in the chamber120. As described above, the susceptor110may serve as a heater. Thus, the susceptor110may be maintained at a constant temperature while performing the ONO dielectric layer formation process. For example, while the ONO dielectric layer formation process is performed, the temperature of the substrate200may be constantly maintained by the susceptor110. In an implementation, the susceptor110may be maintained at about 500° C. or less.

Next, referring toFIGS. 1 through 6, a first oxide layer210may be formed on the substrate200(S200).

Referring toFIG. 3, during a first oxide layer forming period T1, a first silicon precursor207may be fed into the chamber120, purged, oxidized by performing oxygen plasma treatment on the first silicon precursor207, and purged. Here, the substrate200may be maintained at a constant temperature by the susceptor110during the first oxide layer forming period T1.

For example, referring toFIGS. 1 and 3, the first valve145may be opened to feed the first silicon precursor207(of the first source140) into the chamber120through the shower plate115. Referring toFIG. 4, the first silicon precursor207may be fed onto the substrate200. Referring toFIG. 5, a portion207_1of the first silicon precursor207may be adsorbed onto the substrate200.

The substrate200may include, e.g., silicon (Si). If the substrate200includes silicon (Si), a native oxide layer205may be formed on a portion of the substrate200. For example, the first silicon precursor207may include a silane-based material or a material having Si—N bonds. In an implementation, the first silicon precursor207may include, e.g., bis(tertiarybutylamino)silane (BTBAS).

Next, referring toFIGS. 1 and 5, the second valve155may be opened to feed a purge gas (of the second source150) into the chamber120through the shower plate115. A portion207_2of the first silicon precursor207that is not adsorbed onto the substrate200may be purged by the purge gas to then be exhausted outside of the chamber120through the pump125.

Referring toFIGS. 1 and 6, the third valve165may be opened to feed an oxygen gas (of the third source160) into the chamber120through the shower plate115. In order to activate plasma, a power of about 100 W may be applied between the shower plate115and the susceptor110. Applying the power into the chamber120may change the oxygen gas into plasma. Thus, the first silicon precursor portion (207_1ofFIG. 5) may be oxidized by oxygen plasma treatment, and the first oxide layer210may be formed on the substrate200.

Next, referring back toFIG. 1, the second valve155may be opened to feed the purge gas (of the second source150) into the chamber120through the shower plate115. Unreacted gases (not having participated in reactions taking place in the chamber120) may be purged by the purge gas to then be exhausted outside of the chamber120through the pump125.

Referring toFIGS. 1,3, and7, a surface of the first oxide layer210may be subjected to first nitrogen plasma treatment (S300).

Referring toFIGS. 1 and 3, during a nitrogen plasma treatment period T2, the fourth valve175may be opened to feed a nitrogen gas (of the fourth source170) into the chamber120through the shower plate115. In order to activate plasma, a power of about 200 W may be applied between the shower plate115and the susceptor110. Applying the power into the chamber120may change the nitrogen gas into plasma. Thus, a surface of the first oxide layer210may be subjected to the first nitrogen plasma treatment (S300).

In an implementation, the fifth valve185may be opened to feed a helium gas (of the fifth source180) into the chamber120at the same time with the nitrogen gas (of the fourth source170). The helium gas may facilitate changing of the nitrogen gas into plasma. For example, the helium gas may be supplied during at least a portion of or during the entire nitrogen plasma treatment period T2.

Referring toFIG. 7, hydroxide (—OH) groups on the surface of the first oxide layer210may be substituted by amino (NH) groups by the first nitrogen plasma treatment. For example, the first nitrogen plasma treatment may reduce a density of the hydroxide (—OH) groups on the surface of the first oxide layer210.

The hydroxide (—OH) group may have a weaker bonding force than the amino (NH) group. Thus, the first nitrogen plasma treatment may increase a bonding force between the first oxide layer210and a nitride layer (220ofFIG. 11) by substituting the hydroxide (—OH) groups on the surface of the first oxide layer210with amino (—NH) groups. In addition, it is possible to suppress generation of particles caused by an unstable interface state between the first oxide layer210and the nitride layer220.

As described above, during the formation process of the first oxide layer210, a power of about 100 W may be applied to the chamber120. By contrast, during the first nitrogen plasma treatment process, a power of about 200 W may be applied to the chamber120. In order to substitute hydroxide (—OH) groups with amino (NH) groups, relatively high energy plasma may be required. Thus, more power may be applied to the chamber120during the first nitrogen plasma treatment period T2.

Next, referring toFIGS. 1,2, and8through12, the nitride layer220may be formed on the first oxide layer210(S400).

Referring toFIG. 3, during a nitride layer forming period T3, a second silicon precursor217may be fed into the chamber120, purged, oxidized by performing nitrogen plasma treatment on the second silicon precursor217, and purged. Here, the substrate200may be maintained at a constant temperature by the susceptor110during the nitride layer forming period T3.

Referring toFIGS. 1 and 3, the first valve145may be opened to feed the second silicon precursor217(of the first source140) into the chamber120through the shower plate115. For example, referring toFIG. 8, the second silicon precursor217may be fed onto the first oxide layer210. Referring toFIGS. 9 and 10, a portion217_1of the second silicon precursor217may be adsorbed onto the first oxide layer210.

The second silicon precursor217may be the same with the first silicon precursor (207ofFIG. 4). For example, in the method for forming a dielectric layer according to the present embodiment, the same silicon precursor may be supplied when the oxide layer and the nitride layer are formed, while different reactant gases may be fed into the chamber120.

Next, referring toFIGS. 1 and 10, the second valve155may be opened to feed the purge gas (of the second source150) into the chamber120through the shower plate115. A portion217_2of the second silicon precursor217(that is not adsorbed onto the substrate200) may be purged by the purge gas to then be exhausted outside of the chamber120through the pump125.

Referring toFIGS. 1 and 11, the fourth valve175may be opened to feed the nitrogen gas (of the fourth source170) into the chamber120through the shower plate115. In order to activate plasma, a power of about 100 W may be applied between the shower plate115and the susceptor110. Applying the power into the chamber120may change the nitrogen gas into plasma. Thus, the second silicon precursor portion (217_1ofFIG. 10) may be nitridated by nitrogen plasma treatment, and the nitride layer220may be formed on the first oxide layer210.

In an implementation, the sixth valve195may be opened to feed a hydrogen gas (of the sixth source190) into the chamber120at the same time with the nitrogen gas (of the fourth source170). Forming the nitride layer220using the nitrogen gas and the hydrogen gas may increase a density of the nitride layer220, thereby improving an insulating property of the nitride layer220.

Next, referring back toFIG. 1, the second valve155may be opened to feed the purge gas (of the second source150) into the chamber120through the shower plate115. Unreacted gases (not having participated in reactions taking place in the chamber120) may be purged by the purge gas to then be exhausted outside of the chamber120through the pump125.

Referring toFIGS. 1,3and12, a surface of the nitride layer220may be subjected to a second nitrogen plasma treatment (S500).

Referring toFIGS. 1 and 3, during a nitrogen plasma treatment period T4, the fourth valve175may be opened to feed the nitrogen gas (of the fourth source170) into the chamber120through the shower plate115. In order to activate plasma, a power of about 200 W may be applied between the shower plate115and the susceptor110. Applying the power into the chamber120may change the nitrogen gas into plasma. Thus, a surface of the nitride layer220may be subjected to second nitrogen plasma treatment.

In an implementation, the fifth valve185may be opened to feed the helium gas (of the fifth source180) into the chamber120at the same time with the nitrogen gas (of the fourth source170). The helium gas may facilitate changing of the nitrogen gas into plasma.

Referring toFIG. 12, hydrogen (H) contained in the amino (—NH) groups on the surface of the nitride layer220may be removed by the second nitrogen plasma treatment. For example, the second nitrogen plasma treatment may reduce a density of the amino (NH) groups on the surface of the nitride layer220, thereby reducing a density of hydrogen (H) on the surface of the nitride layer220.

For example, an insulating property of the nitride layer220may be improved by performing the second nitrogen plasma treatment on the nitride layer220to reduce the hydrogen (H) density of the surface of the nitride layer220. Thus, the dielectric layer may be formed even at a low temperature, e.g., when the susceptor110maintains the temperature at about 500° C. or less.

As described above, during forming the first oxide layer210and the nitride layer220, a power of about 100 W may be applied to the chamber120. In contrast, during the first nitrogen plasma treatment process, a power of about 200 W may be applied to the chamber120. In order to remove hydrogen (H) from amino (—NH) groups, relatively high energy plasma may be required. Thus, more power may be applied to the chamber120during the second nitrogen plasma treatment period T4.

Next, referring toFIGS. 1,3, and13, a second oxide layer230may be formed on the nitride layer220(S600).

Forming the second oxide layer230may be substantially the same as forming the first oxide layer210, except that the oxide layer is formed on the nitride layer220, and thus the following description will be briefly given.

A third silicon precursor may be the same as the first or second silicon precursor (207ofFIG. 4or217ofFIG. 8). For example, in the method for forming a dielectric layer according to the present embodiment, the same silicon precursor may be supplied when the oxide layer and the nitride layer are formed.

Thus, referring toFIG. 13, according to the present embodiment, the first oxide layer210, the nitride layer220, and the second oxide layer230may be sequentially formed on the substrate200, thereby forming the dielectric layer having an oxide/nitride/oxide (ONO) structure.

For example, forming the first oxide layer210, the nitride layer220, and the second oxide layer230and performing first and second nitrogen plasma treatments may be performed using an in-situ process. For example, the substrate200may be maintained at a constant temperature by the susceptor110, and the in-situ process may be performed using the same silicon precursor. Thus, the dielectric layer forming process may be streamlined and simplified, thereby increasing manufacturing efficiency of the dielectric layer. In addition, multiple layers may be formed on a substrate200disposed in a single chamber. Thus, it may not be necessary to transfer the substrate200to another chamber, and contamination of the dielectric layer (which may be caused while moving the substrate200), may be avoided, thereby increasing the reliability of the dielectric layer.

In the method for forming a dielectric layer according to the present embodiment, plasma-enhanced atomic layer deposition (PEALD) may be used. Therefore, the dielectric layer formed by the method for forming a dielectric layer according to the present embodiment may have high step coverage. Further, the method for forming a dielectric layer according to the present embodiment may be performed using an in-situ process. Thus, a nitride layer may be easily formed and a thickness of the nitride layer may be easily adjusted. For example, an oxide layer and a nitride layer may be formed using the same silicon precursor. Thus, it may be easy to determine which of the oxide layer and the nitride layer is to be formed by controlling reactant gases supplied to a chamber. In addition, if it is desired that the oxide layer be thickly formed, an oxide layer forming process may be repeatedly performed several times until the oxide layer has the desired thickness, followed by performing the nitride layer forming process.

FIG. 14illustrates a flowchart showing a method of forming a dielectric layer according to another embodiment. The following description will focus on differences from the method according to the previous embodiment.

Referring toFIG. 14, the method for forming a dielectric layer according to the present embodiment is different from the previous embodiment in that a surface of a nitride layer (220ofFIG. 13) may not be subjected to second nitrogen plasma treatment.

FIG. 15illustrates a flowchart showing a method of forming a dielectric layer according to yet another embodiment. The method for forming a dielectric layer according to the present embodiment will be described with reference toFIG. 15. However, the following description will focus on differences from the method according to the previous embodiments.

Referring toFIG. 15, the method of forming a dielectric layer according to the present is different from the previous embodiments in that a surface of a first oxide layer (210ofFIG. 13) may not be subjected to first nitrogen plasma treatment.

FIG. 16illustrates a flowchart showing a method of forming a dielectric layer according to still another embodiment. The method of forming a dielectric layer according to the present will be described with reference toFIG. 16. However, the following description will focus on differences from the method according to the previous embodiments.

Referring toFIG. 16, the method of forming a dielectric layer according to the present embodiment is different from the method of forming a dielectric layer according to the previous embodiments in that a surface of a first oxide layer (210ofFIG. 13) may not be subjected to first nitrogen plasma treatment and a surface of a nitride layer (220ofFIG. 13) may not be subjected to second nitrogen plasma treatment.

FIG. 17illustrates a cross-sectional view of an intermediate structure for explaining a method for forming a dielectric layer according to still another embodiment. The method for forming a dielectric layer according to the present embodiment will be described with reference toFIG. 17.

Referring toFIG. 17, a dielectric layer having a nitrogen concentration increasing upwardly and an oxygen concentration increasing downwardly may be formed. An oxide layer310and a nitride layer320may be formed such that a thickness of the nitride layer320gradually increases upwardly (with respect to a plane ofFIG. 17), while a thickness of the oxide layer310gradually increases downwardly (with respect to a plane ofFIG. 17).

Equipment to which a method of forming a dielectric layer according to an embodiment is applied will now be described with reference toFIGS. 18 through 21.FIGS. 18 through 21illustrate perspective and cross-sectional views of devices to which a method for forming a dielectric layer according to an embodiment is applied.

First, referring toFIGS. 18 and 19, the method of forming a dielectric layer according to an embodiment may be used in forming a flash memory device.

Referring toFIG. 18, a first oxide layer412, a nitride layer414, a second oxide layer416, and a control gate electrode420may be sequentially formed on a substrate400. For example, the first oxide layer412may be a tunnel oxide layer, and the nitride layer414may be a charge trap layer.

Referring toFIG. 19, a tunnel oxide layer532, a floating gate electrode530, an ONO dielectric layer510, and a control gate electrode520may be sequentially formed on a substrate500. The floating gate electrode530and the control gate electrode520may be separated from each other by the ONO dielectric layer510. The ONO dielectric layer510may be configured such that a first oxide layer512, a nitride layer514, and a second oxide layer516are sequentially formed.

Referring toFIGS. 20 and 21, the method of forming a dielectric layer according to an embodiment may be used in forming other types of memory devices.

Referring toFIG. 20, a substrate600may include a plurality of protrusions, and a first oxide layer610, a nitride layer620, and a second oxide layer630may be sequentially formed on the substrate600. The dielectric layer formed by the method of forming a dielectric layer according to an embodiment may have high step coverage. Thus, the dielectric layer may be stably deposited on the substrate600having the plurality of protrusions.

FIG. 21illustrates a cross-sectional view of the device ofFIG. 20, taken along the line A-A′. Referring toFIG. 21, not only an ONO dielectric layer (formed on top surfaces of protrusions of the substrate600), but also an ONO dielectric layer (formed on surfaces of the protrusions) may be used in discrete memory devices.

By way of summation and review, the ONO dielectric layer may be formed in multiple reactors. In this case, it may be necessary for the dielectric layer to be moved between different reactors, thereby reducing manufacturing efficiency of the dielectric layer and increasing the likelihood contamination of the dielectric layer while moving between reactors. The contaminated dielectric layer may cause an unstable interface state, thereby lowering the reliability of the dielectric layer.

For example, the ONO dielectric layer may be formed by a three-step process of sequentially depositing a silicon oxide layer, a silicon nitride layer, and a silicon oxide layer on a substrate. The silicon oxide layer and the silicon nitride layer included in the ONO dielectric layer may be formed at different temperatures in different reactors. In detail, the silicon oxide layer and the silicon nitride layer may be formed at a temperature of 700° C. or higher.

The embodiments provide a process for preparation of a semiconductor device including an ONO structure, including forming the ONO structure by providing a semiconductor substrate having a silicon surface; forming a first oxide layer on the silicon surface; depositing a silicon nitride layer on the first oxide layer, wherein the silicon nitride layer is formed by in-situ plasma generated nitration of surface of the silicon oxide layer; and forming a top oxide layer on the silicon nitride layer within same chamber. The embodiments provide a method of forming a dielectric layer, which may increase manufacturing efficiency of the dielectric layer and may protect and/or prevent the dielectric layer from being contaminated by forming an oxide/nitride/oxide (ONO) dielectric layer using an in-situ process. An ONO layer, by using in-situ plasma generated nitration, may be fabricated without creation of interface states resulting from weak bonding and contamination. The embodiments may be carried out in a single reactor and under like temperature conditions.