KR20040057830A - Method for forming a capacitor of a semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming a capacitor of a semiconductor device is provided to improve process margin and reliability by improving the surface roughness of a storage node electrode. CONSTITUTION: An interlayer dielectric(22) is formed on a substrate. A pad oxide layer(24), an etch stop layer(26) and an oxide layer are sequentially formed on the interlayer dielectric. A contact hole is formed by patterning the oxide layer, the etch stop layer, the pad oxide layer and the interlayer dielectric. A polysilicon layer is filled in the contact hole. A storage node electrode pattern(30) is formed by etching the polysilicon layer. A nitride spacer(34) is formed at sidewalls of the storage node electrode pattern to prevent oxidation. An oxide layer(36) is formed on the storage node electrode pattern. The nitride spacer is removed. Then, an upper electrode is formed.

Description

Method for forming a capacitor of a semiconductor device

The present invention relates to a method of manufacturing a semiconductor memory device, and more particularly, to a method of forming a capacitor having a fin structure.

In general, semiconductor memory devices, particularly DRAM DRAMs having memory densities of 2M to 6M, are representative systems manufactured by adding only some capacitor forming processes to the existing logic device manufacturing process. It is a System on Chip (SoC) product. The high integration of such MDL devices is achieved at a high speed, and a decrease in cell capacitance due to a decrease in memory cell area is a serious obstacle to increase in integration.

The reduction of cell capacitance not only decreases the readability of the memory cell, increases the soft error rate, but also makes it difficult to operate the device at low voltage, resulting in excessive power consumption during device operation. Therefore, it is required to secure sufficient cell capacitance such that the operating characteristics of the memory cell are not degraded. To achieve a constant capacitance within the reduced cell area, the use of more complex processes and capacitor structures, such as three-dimensional structures, is inevitable. The double stack structure, fin structure, spread stack structure, box structure and cylindrical electrode structure are three-dimensional proposed to increase the capacitance of memory cells. Structures.

1A to 1D are cross-sectional views illustrating a manufacturing process of a capacitor having a fin structure as an example of a three-dimensional structure.

Referring to FIG. 1A, an interlayer insulating film 2 is formed by depositing an oxide film on a semiconductor substrate (not shown) on which a lower structure such as a transistor is formed. On the interlayer insulating film, a pad oxide film 4, a nitride film 6 and an oxide film are sequentially deposited. Subsequently, a contact hole is formed by sequentially etching the layers of the region where the capacitor is to be formed by a photolithography process. Next, a polysilicon film 10 is deposited on the entire surface of the resultant product to completely fill the contact hole, and then a photoresist pattern 12 defining a region where a storage electrode is to be formed is formed.

Referring to FIG. 1B, the polysilicon layer is dry-etched using the photoresist pattern as a mask to form a storage electrode pattern 10. Next, the photoresist pattern is removed. Subsequently, a predetermined wet etching is performed on the oxide film formed under the storage electrode pattern to be removed.

Referring to FIG. 1C, when the polysilicon film 14 is deposited on the entire surface of the resultant on which the storage electrode pattern 10 is formed, the polysilicon film 14 is formed to surround the storage electrode pattern as shown. .

Referring to FIG. 1D, by performing dry etching using plasma, the polysilicon film 14 remaining on the side and the bottom of the storage electrode pattern 10 is removed and the polysilicon film in the remaining area is removed. The storage electrode of the structure is completed.

According to the conventional method described above, an overetch is performed to completely remove the polysilicon layer under the storage electrode pattern 10 in the etching process for the polysilicon layer. As a result, as illustrated in FIG. 1D, the upper portion of the storage electrode pattern 10 is eroded, resulting in poor surface roughness, which in turn adversely affects the reliability of the device. In addition, since the nitride film exists under the storage electrode 10 + 14, the margin for the gas and the process step is reduced due to the high etching selectivity with the oxide film in the subsequent etching process for forming the contact hole.

An object of the present invention is to provide a method for forming a capacitor of a semiconductor device capable of improving the surface roughness of the storage electrode having a fin structure to secure device reliability and improve process margins.

1A to 1D are cross-sectional views illustrating a manufacturing process of a capacitor having a conventional fin structure.

2A to 2E are cross-sectional views illustrating a method of forming a capacitor having a fin structure according to the present invention.

In order to achieve the above object, a method of forming a capacitor of a semiconductor device according to the present invention includes forming an interlayer insulating film on a semiconductor substrate, sequentially forming a pad oxide film, an etch stop film, and an oxide film on the interlayer insulating film, the oxide film, Etching the etch stop layer, the pad oxide layer, and the interlayer insulating layer to form a contact hole exposing the semiconductor substrate; depositing a polysilicon layer on the front surface to fill the contact hole; and patterning the polysilicon layer to form a storage electrode pattern. Forming an oxide film on the side and bottom of the storage electrode pattern, forming an oxide film on an upper surface of the storage electrode pattern, removing the antioxidant film, and removing the storage electrode. Forming a polysilicon film on the side and bottom of the pattern, and And forming a dielectric film and a plate electrode in turn on a group of storage electrodes.

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

2A to 2E are cross-sectional views illustrating a method of forming a capacitor having a fin structure according to the present invention.

Referring to FIG. 2A, an oxide film is deposited on a semiconductor substrate (not shown) on which a lower structure such as a transistor is formed to form an interlayer insulating layer 22 to insulate and protect the lower structures from the upper conductive layer. On the interlayer insulating film 22, a thin first oxide film 24, a nitride film 26, and a second oxide film 28 are sequentially deposited. The second oxide layer 28 is to form a storage electrode having a three-dimensional structure, and the nitride layer 26 is the first oxide layer 24 and the interlayer insulating layer 22 in an etching process for removing the second oxide layer 28. It acts as an etch barrier to protect.

Subsequently, a contact hole is formed by sequentially etching the layers of the region where the capacitor is to be formed by a photolithography process. Next, a polysilicon layer 30 is deposited on the entire surface of the resultant to completely fill the contact hole, and then a photoresist pattern 32 is formed on the polysilicon layer to define a region where a storage electrode is to be formed.

Referring to FIG. 2B, the polysilicon layer is dry-etched using the photoresist pattern as a mask to form a storage electrode pattern 30, and then the photoresist pattern is removed. Subsequently, a predetermined wet etching is performed on the second oxide film formed under the storage electrode pattern to be removed. In this case, the nitride layer 26 formed under the second oxide layer serves as an etch stop layer. Next, a sacrificial nitride film 34 is formed by depositing a material having a predetermined etching selectivity, for example, a nitride film, on the entire surface of the polysilicon film for storage electrodes on the front surface of the resultant.

Referring to FIG. 2C, the nitride spacer 34 is formed on the side surface of the storage electrode pattern 30 by performing plasma etching using a mixed gas of carbon (F) -fluorine (F) and argon (Ar). Form. Next, an oxide film 36 is formed by oxidizing a portion not covered by the nitride film spacer 34, that is, an upper surface of the storage electrode pattern 30. The oxide film 36 is formed to a thickness of about 100 kPa in an 800 ° C. temperature and steam (H ₂ O) atmosphere by using a wet oxidation method.

Referring to FIG. 2D, the nitride film spacer (34 in FIG. 2C) and the nitride film for etching barrier layer (26 in FIG. 2C) are removed using a phosphoric acid solution at a temperature of about 155 ° C. The polysilicon film 38 is formed on the entire surface of the resultant product. By removing the nitride layer for the etching barrier layer as described above, it is possible to prevent problems such as the change of the etching gas and the increase of the process step due to the difference in the etching rate between the nitride layer and the oxide layer in the etching process for forming the contact.

Referring to FIG. 2E, the polysilicon film is dry-etched using plasma to remove the polysilicon film in the remaining region while leaving the polysilicon film 14 existing on the side and the bottom of the storage electrode pattern 10. The storage electrode of (Fin) structure is completed. At this time, the transient etching is essential for the complete removal of the polysilicon present between the storage electrodes, in the present invention, the surface is protected by an oxide film (36 in Fig. 2d) of the upper portion of the storage electrode pattern to prevent surface erosion have. The oxide film is removed in a cleaning step using hydrofluoric acid (HF) before subsequent processing.

Subsequently, although not shown, a capacitor is formed by forming a dielectric film on the resultant and depositing a polysilicon film on the entire surface to form a plate electrode according to a conventional method.

On the other hand, the present invention is not limited to the above-described embodiment, various modifications are possible by those skilled in the art within the spirit and scope of the present invention described in the claims to be described later.

According to the method for forming a storage electrode of a semiconductor device according to the present invention, by forming a nitride film on the side and the bottom of the storage electrode and then oxidizing the upper portion of the storage electrode to form an oxide film, the oxide film is present between the storage electrode The surface of the storage electrode can be protected from overetching to completely remove polysilicon, thereby preventing erosion. Therefore, the surface roughness of the storage electrode may be improved to ensure reliability of the device and to improve process margins.

Claims (6)

Forming an interlayer insulating film on the semiconductor substrate; Sequentially forming a pad oxide film, an etch stop film, and an oxide film on the interlayer insulating film; Etching the oxide layer, the etch stop layer, the pad oxide layer, and the interlayer insulating layer to form a contact hole exposing a semiconductor substrate; Depositing a polysilicon film on the entire surface to fill the contact hole; Patterning the polysilicon layer to form a storage electrode pattern; Forming an anti-oxidation film on side and bottom of the storage electrode pattern; Forming an oxide film on an upper surface of the storage electrode pattern; Removing the antioxidant film; Forming a polysilicon film on side and bottom of the storage electrode pattern; And And sequentially forming a dielectric film and a plate electrode on the storage electrode. The method of claim 1, wherein the etch stop layer is formed of a nitride film. The method of claim 1, wherein the antioxidant film is formed of a nitride film. The method of claim 1, wherein the forming of the anti-oxidation film on the side and the bottom of the storage electrode pattern comprises depositing a nitride film on the entire surface of the resultant product on which the storage electrode pattern is formed, and etching back the nitride film. A method of forming a capacitor of a semiconductor device. The method of claim 1, wherein the forming of an oxide film on the upper surface of the storage electrode pattern comprises thermally oxidizing the storage electrode pattern to form an oxide film. The method of claim 1, wherein the etch stop layer is removed together with the step of removing the antioxidant layer.