KR20090014658A - Method of forming a layer and method of manufacturing a non-volatile memory device using the same - Google Patents

Abstract

A method of forming a layer and method of manufacturing a non-volatile memory device using the same is provided to improve the property of the semiconductor device by forming a film at interface which relatively the nitrogen distribution density is high. In a method of forming a layer and method of manufacturing a non-volatile memory device, an oxide film(102) for pad is formed on the substrate(100). A silicon-rich nitride layer(104) is formed on the oxide film for pad. The oxide film in which the nitrogen is accumulated is formed on the interface of the substrate by oxidizing the silicon-rich nitride layer. The silicon-rich nitride layer is formed after forming the silicon nitride film on the oxide film for pad by inserting silicon into the silicon nitride film.

Description

Method of forming a layer and method of manufacturing a non-volatile memory device using the same

The present invention relates to a method of forming a thin film used in a memory device and a method of manufacturing a nonvolatile memory device using the same. More particularly, the present invention relates to a thin film forming method suitable for use as a tunnel oxide film or a gate oxide film and a method of manufacturing a nonvolatile memory device using the same.

Among the semiconductor devices, the nonvolatile memory device may maintain its state even after time of inputting data. In particular, there is an increasing demand for flash memory devices capable of electrically inputting and outputting data.

The memory cell for storing data in the flash memory device has a stacked gate structure including a tunnel oxide layer pattern, a charge storage layer pattern, a dielectric layer pattern, and a control gate electrode on a substrate.

In the nonvolatile memory device having the above-described structure, data is stored by applying an appropriate voltage to the control gate electrode and the substrate to inject or extract electrons into the charge storage film pattern. Therefore, when an operation of repeatedly writing or reading data to the nonvolatile memory device is performed, charges continue to enter and exit the tunnel oxide layer interposed between the substrate and the charge storage layer pattern.

As described above, when the nonvolatile memory device is repeatedly operated, the bonds in the tunnel oxide layer may be broken by the stress caused by the operation. Therefore, dangling bonds are generated in the tunnel oxide layer, and fixed charges or holes are trapped in the dangling bonds to change threshold voltages of cells in the nonvolatile memory device. Therefore, the reliability of the nonvolatile memory device is remarkably degraded.

In order to increase the reliability of the nonvolatile memory device and to improve durability and data retention capability, the tunnel oxide film should have very good characteristics. To this end, there should be little dangling bond at the interface portion between the tunnel oxide layer and the substrate and the tunnel oxide layer and the charge storage layer pattern, thereby preventing the trapping of charges or holes at the interface portion. In addition, the inflow of impurity ions or hydrogen into the tunnel oxide film from the floating gate used as the charge storage film pattern should be suppressed.

In order to improve the characteristics of the tunnel oxide film, the tunnel oxide film is formed of silicon oxide containing nitrogen. As an example of a method of forming a tunnel oxide film with silicon oxide containing nitrogen, Japanese Patent Application Laid-Open No. 2002-353343 and 2000-232170 and the like can be given.

However, since a dangling bond due to stress is mainly generated at the interface between the tunnel oxide layer and the substrate and the tunnel oxide layer and the charge storage layer pattern, in order to suppress generation of the dangling bond, at the interface portion of the tunnel oxide layer Large amounts of nitrogen should be distributed. However, it is difficult to distribute a large amount of nitrogen locally at the interface portion of the tunnel oxide film by the above method. Moreover, it is not easy to form the tunnel oxide film without generating damage in the substrate and the tunnel oxide film.

One object of the present invention is to provide a method for forming a thin film having a relatively high concentration of nitrogen distribution at the interface portion.

Another object of the present invention is to provide a method of manufacturing a nonvolatile memory device including the thin film.

In the thin film forming method according to an embodiment of the present invention for achieving the above object, an oxide film for a pad is formed on a substrate. A silicon rich nitride film is formed on the pad oxide film. Next, by oxidizing the silicon rich nitride film, an oxide film in which nitrogen is accumulated is formed at the interface with the substrate.

In order to form the silicon rich nitride film, a silicon nitride film is formed on the pad oxide film. Silicon is injected into the silicon nitride film. Next, the amorphous silicon film is nitrided.

The silicon rich nitride layer may be formed such that a content ratio of silicon and nitrogen contained therein is lower than 1: 1.34.

The forming of the oxide film in which nitrogen is accumulated may be performed through radical oxidation, in-situ steam generation, or plasma oxidation.

A process of forming an upper silicon rich nitride film on the oxide film and a process of forming an upper oxide film having nitrogen accumulated at an interface with the substrate by oxidizing the upper silicon rich nitride film may be performed.

The upper oxide film is preferably formed to a thickness thinner than the oxide film.

In addition, a plasma nitridation process may be further performed on the upper oxide layer.

In the nonvolatile memory device manufacturing method according to an embodiment of the present invention for achieving the above object, an oxide film for a pad is formed on a substrate. A silicon rich nitride film is formed on the pad oxide film. By oxidizing the silicon rich nitride film, an oxide film in which nitrogen is accumulated is formed at the interface with the substrate. The preliminary floating gate is formed on the oxide film. A dielectric film is formed on the preliminary floating gate. A control gate layer is formed on the dielectric layer. Next, the control gate layer, the dielectric layer, and the preliminary floating gate are sequentially patterned to form a control gate electrode, a dielectric layer pattern, and a floating gate electrode.

As described, according to the method of the present invention, a silicon oxide film having a relatively high nitrogen distribution concentration can be formed. In particular, the silicon oxide film according to the present invention has a very high concentration of nitrogen at the interface portion in contact with the other films. Therefore, in the silicon oxide film, generation of dangling bonds due to stress generated at an interface portion is suppressed. Therefore, the characteristics of the semiconductor device can be improved by using the silicon oxide film formed by the method of the present invention as a tunnel oxide film of a cell transistor or a gate oxide film of a MOS transistor of a nonvolatile memory device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Example 1

1 to 3 are cross-sectional views for describing a method of forming a thin film including nitrogen having a relatively high concentration at an interface according to Example 1 of the present invention.

The thin film described below may be used as a tunnel oxide film of a nonvolatile memory device or a gate oxide film of a MOS transistor.

Referring to FIG. 1, a pad oxide film 102 is formed on a substrate 100. The pad oxide film 102 is made of silicon oxide having a very thin thickness of 5 to 15 Å. The pad oxide layer 102 is formed to reduce stress generated when silicon nitride is in direct contact with the substrate 100. When the thickness of the pad oxide film 102 becomes thicker than 15 kPa, it is not preferable to increase the nitrogen concentration at the interface portion with the substrate due to the pad oxide film.

The pad oxide layer 102 may be formed through a radical oxidation process, an in-situ steam generation method, or a plasma oxidation process. Alternatively, the pad oxide film 102 may be formed through an ozone water treatment process.

Referring to FIG. 2, a silicon rich nitride film 104 is formed on the pad oxide film 102. The silicon rich nitride film 104 is a thin film in which an excessive amount of silicon may cause oxidation. Specifically, it is preferable that the content ratio of silicon and nitrogen contained in the silicon rich nitride film 104 is lower than 1: 1.34 (ie, SiNx 0 <x <1.34).

As one of methods for forming the silicon rich nitride film 104, first, a silicon nitride film is formed on the pad oxide film 102 by chemical vapor deposition. Next, silicon is implanted into the silicon nitride film. In order to inject the silicon, an ion implantation method or a plasma doping method may be performed.

As another method for forming the silicon rich nitride film 104, first, an amorphous silicon film is formed on the pad oxide film 102. Next, the amorphous silicon film is nitrided. The nitriding process may be performed through a thermal nitriding treatment process using a reaction gas containing nitrogen, a plasma nitriding treatment process or a plasma doping process. N ₂ gas, NH ₃ gas, NO gas, N ₂ O gas, or the like may be used as the reaction gas in the nitriding process. These are preferably used alone, but may be used by mixing with each other.

If the silicon rich nitride film 104 is thinner than 20 kPa, the nitrogen concentration at the interface will not be sufficient. In addition, when the silicon rich nitride film 104 is thicker than 50 GPa, the silicon rich nitride film 104 is not easily oxidized. Therefore, the silicon rich nitride film 104 preferably has a thickness of about 20 to 50 kPa. More preferably, the silicon rich nitride film 104 has a thickness of about 30 to 40 kPa.

Referring to FIG. 3, the silicon rich nitride film 104 is oxidized to form a silicon oxide film 106 in which nitrogen is accumulated at an interface with the substrate 100.

The oxidation process for forming the silicon oxide film 106 may be selected from one of radical oxidation, in-situ steam generation, and plasma oxidation. The oxidation process is preferably performed to oxidize all of the silicon rich nitride film 104.

At this time, the longer the time for performing the oxidation process or the thicker the thickness of the silicon oxide film 106 formed through the oxidation process, the more nitrogen is released from the film, the nitrogen concentration at the interface can be reduced. Therefore, by adjusting the oxidation process method or the thickness of the oxide film for forming the silicon oxide film 106, it is possible to control the nitrogen concentration in the silicon oxide film 106 to be formed.

Specifically, the silicon oxide film 106 may be formed to have a thickness greater than the target thickness, and then partially remove the silicon oxide film 106 to form the silicon oxide film 106 having the target concentration and thickness. In addition, by performing a radical oxidation process requiring a relatively long process time, the nitrogen concentration in the silicon oxide film 106 may be relatively low. On the contrary, by performing the in-situ steam generation and plasma oxidation processes requiring a relatively short process time, the nitrogen concentration in the silicon oxide layer 106 may be relatively increased.

Since the silicon oxide film formed by performing the process is formed by oxidizing the silicon rich nitride film, the concentration of nitrogen is very high at the interface between the substrate and the silicon oxide film. Therefore, in the silicon oxide film, generation of dangling bonds due to stress generated at the interface with the substrate is suppressed.

Example 2

4 and 6 are cross-sectional views illustrating a method of forming a thin film including nitrogen having a relatively high concentration at an interface according to Example 2 of the present invention.

The thin film of the present embodiment described below is formed by performing additional processes to the method of Example 1 above. The thin film of this embodiment has a high nitrogen concentration at the upper and lower interfaces of the silicon oxide film.

First, by performing the same process as described with reference to FIGS. 1 to 3, the silicon oxide film 106 in which nitrogen is accumulated is formed at the interface with the substrate 100.

Referring to FIG. 4, an upper silicon rich nitride film 108 is formed on the silicon oxide film 106. The upper silicon rich nitride film 108 may have a content ratio of silicon and nitrogen lower than 1: 1.34 (ie, SiNx 0 <x <1.34). The upper silicon rich nitride film 108 may be formed by one of the methods described in the first embodiment. In addition, the upper silicon rich nitride film 108 preferably has a thickness of about 20 to about 50 microns.

Referring to FIG. 5, the upper silicon rich nitride film 108 is oxidized to form an upper silicon oxide film 110 in which nitrogen is accumulated on an upper surface portion. The oxidation process for forming the upper silicon oxide layer 110 may be selected from radical oxidation, in-situ steam generation, and plasma oxidation.

In this case, the upper silicon oxide film 110 preferably has a thickness thinner than that of the silicon oxide film 106 formed below. This is because when the upper silicon oxide layer 110 is formed thick, the nitrogen concentration of the upper surface portion does not increase sufficiently.

On the other hand, although not shown, when the upper silicon oxide film 110 is formed somewhat thick, the surface of the upper silicon oxide film 110 may be partially removed. In addition, in order to have the highest nitrogen concentration at the upper interface portion of the upper silicon oxide layer 110, a portion of the upper interface portion of the upper silicon oxide layer 110 may be removed. The removal process may be performed through a wet etching process.

Referring to FIG. 6, a plasma nitridation process is performed on the resultant on which the upper silicon oxide layer 110 is formed.

Specifically, the plasma nitridation treatment may be performed using a nitride gas such as N ₂ gas, NH ₃ gas, NO gas, N ₂ O gas, or the like, and a carrier gas such as Ar gas and He gas, and the pressure and the normal temperature of about 1 mtorr to 10 torr. It may be carried out at a temperature of about 600 ℃.

By performing the plasma nitridation process, the nitrogen concentration in the film can be increased somewhat. However, when the plasma nitridation process is performed, damage may occur to the film, and thus the process may be omitted. In particular, even if the nitriding treatment process is not performed, since nitrogen is included in the oxide film structure, the plasma nitriding treatment is not performed when the nitrogen concentration in the structure is at a target level.

Meanwhile, the process of removing a portion of the upper silicon oxide layer 110 may be performed after the plasma nitridation process is performed.

As a result, an oxide film structure having a shape in which the pad oxide film 102, the silicon oxide film 106, and the upper silicon oxide film 110 are stacked is formed. In the oxide structure formed by performing the process, the concentration of nitrogen at the interface portion between the substrate 100 and the oxide structure and the upper interface portion of the oxide structure is very high. That is, when the nitrogen concentration is measured at each depth of the oxide film structure, the peak value of the nitrogen concentration at the interface portion of the substrate 100 and the oxide film structure and the upper interface portion of the oxide film structure is respectively measured. Therefore, the oxide structure is suppressed from generating a dangling bond due to stress generated at an interface portion and an upper surface portion of the substrate 100.

Example 3

7 and 8 are cross-sectional views for explaining a method of forming a thin film containing a relatively high concentration of nitrogen at the interface according to the third embodiment of the present invention.

The method of Example 3 described below is similar to Example 1 except that a process of forming an oxide film for pads and an oxidation process including a nitrogen source when oxidizing the silicon rich nitride film are performed.

First, a first oxide film 120 containing nitrogen is formed by performing an oxidation process including a nitrogen source on a substrate 100 made of single crystal silicon. The first oxide film 120 has a thickness of 5 to 50 kPa. In this manner, the first oxide film may be formed thicker than the pad oxide film of the first embodiment.

Specifically, the first oxide film 120 including nitrogen may be formed by performing an oxidation process using oxygen and hydrogen gas as the source gas and subsequently performing a heat treatment process using NO gas.

A silicon rich nitride film 122 is formed on the first oxide film 120. The silicon rich nitride film 122 may be formed by one of the methods described in the first embodiment.

Next, the silicon rich nitride film 122 is oxidized through an oxidation process including a nitrogen source to form a second oxide film 124 in which nitrogen is accumulated. That is, as described above, the second oxide film 124 including nitrogen may be formed by performing an oxidation process using oxygen and hydrogen gas as the source gas and subsequently performing a heat treatment process using NO gas. have. As such, when performing an oxidation process using a nitrogen source, it is possible to further increase the nitrogen concentration in the oxide film.

Example 4

9 and 10 are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device in accordance with a fourth embodiment of the present invention.

Referring to FIG. 9, a shallow isolation process is performed on the substrate 200 to form an isolation layer (not shown). By forming the device isolation layer, the substrate is divided into an device isolation region and an active region. The device isolation region and the active region extend in the first direction and are disposed in parallel with each other. In FIG. 9, only the active region of the substrate 200 is shown.

A tunnel oxide film 202 is formed on the substrate 200.

The ability to preserve the data stored in the nonvolatile memory device is largely dependent on the reliability of the tunnel oxide film 202. Conventional nonvolatile semiconductor memory devices are required to be able to repeat at least about one million programming and erase operations. Therefore, a tunnel oxide film 202 having a high nitrogen concentration at the interface portion is required so that dangling bond formation is suppressed at the interface portion. Therefore, the tunnel oxide film 202 included in the nonvolatile memory device of the present embodiment may be formed by any of the methods described in the first to third embodiments.

The tunnel oxide film 202 formed by the above-described method can prevent hydrogen from penetrating into the tunnel oxide film in a subsequent process, and prevent the generation of charge trap sites therein, and between the tunnel oxide film and the silicon substrate Interface uniformity is improved.

A charge storage layer is formed on the tunnel oxide layer 202. The charge storage layer may be formed by depositing polysilicon, a metal oxide layer having a high dielectric constant, a silicon nitride layer, a nanocrystal, or the like. These are more preferably used alone. When the charge storage layer is formed of polysilicon, a floating gate type nonvolatile memory device is formed. In contrast, when the charge storage layer 204 is formed of a silicon nitride layer, a metal oxide layer, or a nanocrystal, a non-volatile memory device of a charge trapping type is formed. In this embodiment, the charge storage layer is described as being formed of polysilicon.

Thereafter, the charge storage film is patterned to form a preliminary charge storage film pattern 204. The preliminary charge storage layer pattern 204 may have a shape extending in the same direction as the active region.

A dielectric layer 206 is formed on the preliminary charge storage layer pattern 204. The dielectric film 206 may be formed by atomic layer deposition or chemical vapor deposition. Alternatively, the dielectric layer 206 may be formed by sequentially stacking silicon oxide, silicon nitride, and silicon oxide.

Next, the dielectric film 206 formed in the partial region is removed by a photolithography or etching process. For example, the dielectric film 206 positioned at the portion where the string select transistor SST and the ground select transistor GST are to be formed is selectively removed. A conductive film 208 for forming a control gate electrode is formed on the dielectric film 206.

Referring to FIG. 10, a hard mask pattern 210 is formed on the conductive layer 208. Specifically, the hard mask pattern 210 has a shape extending in a direction perpendicular to the extending direction of the device isolation layer pattern. The conductive layer 208, the dielectric layer 206, the preliminary charge storage layer pattern 204, and the tunnel oxide layer 202 are sequentially etched using the hard mask pattern 210.

By performing the above process, the tunnel oxide film pattern 202a, the charge storage film pattern 204a, the dielectric film pattern 206a, the control gate electrode 208a and the hard mask pattern 210 are stacked on the substrate 200. Complete the gate structure 212. In addition, through the process, a second gate structure (not shown) forming the ground selection line and the string selection line is simultaneously formed. The second gate structure is formed at a portion where the dielectric layer 206 is selectively removed. Thus, unlike the first gate structure 212, the second gate structure has a shape in which the charge storage layer pattern 204a and the control gate electrode 208a are connected to each other by partially removing the dielectric layer pattern 206a. Have

The second gate structures are provided at both sides of the 32 first gate structures 212, respectively, and serve to select the first gate structures 212.

Thereafter, the impurity regions 214 are formed by ion implanting impurities under the surface of the substrate 200 exposed by the first and second gate structures.

In Example 4, a manufacturing method of the NAND type flash memory device has been described. However, the NOR flash memory device may be manufactured by applying the tunnel oxide film forming method. In addition, the gate oxide film of the MOS transistor may be formed using the tunnel oxide film forming method.

Hereinafter, the concentration of nitrogen contained in the oxide film formed by the method of the present invention is measured, and the results are described.

Experimental Example 1

An oxide film was formed by the method of Example 1 of the present invention, and the concentration of nitrogen by depth of the film was measured through SIMS analysis.

The formation conditions of the oxide film used in the present experimental example are as follows. First, a pad oxide film was formed on the substrate by treating a single crystal silicon substrate with ozone water. Thereafter, after forming a silicon nitride film on the pad oxide film, silicon was implanted to form a silicon rich nitride film having a thickness of 35 kPa. Next, a radical oxidation process was performed to oxidize the silicon rich nitride film to form an oxide film. Here, the radical oxidation process was performed under the condition that an oxide film of 60 kV was formed when the bulk silicon substrate was oxidized.

FIG. 11 is a graph showing nitrogen concentrations according to depths of membranes in Experimental Example 1. FIG.

Referring to FIG. 11, it can be seen that a peak value of nitrogen concentration is located at a depth of about 4 nm. The depth at which the peak value of the nitrogen concentration is located corresponds to the interface between the substrate and the oxide film. As shown, it was found that the method of Example 1 can be used to form an oxide film having a high concentration of nitrogen at the interface with the substrate.

Experimental Example 2

An oxide film structure was formed by the method of Example 3 of the present invention, and the concentration of nitrogen by depth of the film was measured through SIMS analysis of the oxide film structure.

Formation conditions of the oxide film structure used in this Experimental Example are as follows. First, after performing a radical oxidation process using hydrogen and oxygen as a reaction gas on a single crystal silicon substrate, a first oxide film containing nitrogen was formed by heat treatment with NO gas. At this time, the first oxide film was formed to have a thickness of about 40 GPa. Thereafter, a silicon rich nitride film having a thickness of 30 GPa was formed on the first oxide film. Next, a radical oxidation process using hydrogen and oxygen as a reaction gas was performed to oxidize the silicon rich nitride film, and then heat treated with NO gas to form a second oxide film including nitrogen. The radical oxidation process was performed under the condition that an oxide film of 40 kV was formed when the bulk silicon substrate was oxidized.

FIG. 12 is a graph showing nitrogen concentration by depth of the oxide film structure in Experimental Example 2. FIG.

Referring to FIG. 12, it can be seen that the peak value of nitrogen concentration is located at a depth of about 2 nm. The depth at which the peak value of the nitrogen concentration is located is adjacent to the surface portion of the oxide film structure. As shown, it can be seen that the method of Example 3 can be used to form an oxide film structure having a high concentration of nitrogen on the upper surface portion.

As described above, according to the method of the present invention, an oxide film having a relatively high nitrogen concentration can be formed at the upper and / or lower interface portions. The oxide film may be used as a tunnel oxide film of a nonvolatile memory device and a gate oxide film of a MOS transistor. In addition, when the oxide film having a high nitrogen concentration at the interface portion is used as the tunnel oxide film or the gate oxide film as described above, the reliability of the memory device can be improved.

1 to 3 are cross-sectional views for describing a method of forming a thin film including nitrogen having a relatively high concentration at an interface according to Example 1 of the present invention.

4 and 6 are cross-sectional views illustrating a method of forming a thin film including nitrogen having a relatively high concentration at an interface according to Example 2 of the present invention.

7 and 8 are cross-sectional views for explaining a method of forming a thin film containing a relatively high concentration of nitrogen at the interface according to the third embodiment of the present invention.

9 and 10 are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device in accordance with a fourth embodiment of the present invention.

FIG. 11 is a graph showing nitrogen concentration by depth of membrane in Experimental Example 1. FIG.

12 is a graph showing nitrogen concentrations according to depths of membranes in Experimental Example 2. FIG.

Claims (9)

Forming an oxide film for a pad on the substrate; Forming a silicon rich nitride film on the pad oxide film; And And oxidizing the silicon rich nitride film to form an oxide film in which nitrogen is accumulated at an interface with the substrate. The method of claim 1, wherein the forming of the silicon rich nitride film, Forming a silicon nitride film on the pad oxide film; And And injecting silicon into the silicon nitride film. The method of claim 1, wherein the forming of the silicon rich nitride film, Forming an amorphous silicon film on the pad oxide film; And Thinning the amorphous silicon film. The method of claim 1, wherein the silicon rich nitride film is formed such that a content ratio of silicon and nitrogen contained therein is lower than 1: 1.34. The method of claim 1, wherein the forming of the oxide film in which nitrogen is accumulated is performed through a radical oxidation, an in-situ steam generation, or a plasma oxidation process. The method of claim 1, Forming an upper silicon rich nitride film on the oxide film; And And oxidizing the upper silicon rich nitride film to form an upper oxide film in which nitrogen is accumulated at an interface with the substrate. The method of claim 6, wherein the upper oxide film is formed to a thickness thinner than the oxide film. The method of claim 6, further comprising performing a plasma nitridation process on the upper oxide layer. Forming an oxide film for a pad on the substrate; Forming a silicon rich nitride film on the pad oxide film; Oxidizing the silicon rich nitride film to form an oxide film in which nitrogen is accumulated at an interface with the substrate; Forming the preliminary floating gate on the oxide film; Forming a dielectric film on the preliminary floating gate; Forming a control gate layer on the dielectric layer; And And sequentially patterning the control gate layer, the dielectric layer, and the preliminary floating gate to form a control gate electrode, a dielectric layer pattern, and a floating gate electrode.

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