KR20080028082A - Method for forming a capacitor in semiconductor device - Google Patents

Abstract

A method for forming a capacitor in a semiconductor device is provided to prevent a sharp point from being formed on a bottom electrode by fast etching a sacrificial oxide layer relative to a TiN layer. A substrate(110) with a sacrificial pattern layer(114) is prepared, and then a bottom electrode material is formed along a stepped surface formed by the sacrificial pattern layer. The substrate is subjected to an etch process(116) using an etch selectivity between the bottom electrode material and the sacrificial pattern layer to form a bottom electrode(115A). The etch process is performed in such a way that the sacrificial pattern layer is etched faster than the bottom electrode material. The bottom electrode material is a TiN layer, and the sacrificial pattern layer is an oxide layer.

Description

METHODS FOR FORMING A CAPACITOR IN SEMICONDUCTOR DEVICE

1A and 1B are cross-sectional views illustrating a method of forming a capacitor of a semiconductor device having a cylinder structure according to the related art.

Figure 2 is a SEM (Scanning Electron Microscope) photograph taken after the process shown in Figure 1b.

3A and 3B are cross-sectional views illustrating a method of forming a capacitor of a semiconductor device having a cylinder structure according to an exemplary embodiment of the present invention.

Figure 4 is a SEM photograph taken after the process shown in Figure 3b.

<Explanation of symbols for the main parts of the drawings>

10, 110: substrate

11, 111: interlayer insulation film

12, 112: storage node contact plug

13, 113: etching stop film

14, 114; Sacrificial Oxide (Sacrifice Pattern Layer)

15, 115: TiN film

15A, 115A: lower electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing technique of a semiconductor device, and more particularly, to a method of forming a capacitor of a semiconductor device, and more particularly, to a method of separating a lower electrode of a capacitor.

As the integration of semiconductor devices increases, design rules continue to decrease. Accordingly, the area occupied by the unit cells is also gradually decreasing. In particular, in a DRAM (Dynamic Random Access Memory) device, since a unit cell is composed of one transistor and one capacitor, it is difficult to secure the capacitance of the capacitor when the design rule decreases.

Accordingly, efforts have recently been made to ensure the capacitance of capacitors per unit area. As part of this is the structure change of the capacitor. That is to change the structure of the capacitor in order to ensure the maximum capacitance per unit area. The capacitor structures known to date include a concave structure and a cylinder structure.

The concave structure is shaped like a hole. Therefore, even if the lower electrode, the dielectric film, and the upper electrode are deposited by using a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process with good step coverage, there is a limit in improving the coating property. In order to ensure the thickness of each material (lower electrode, dielectric film, upper electrode) must be reduced. In addition, in order to secure more capacitance, an oxide film for a storage node pattern for forming a storage node, which is a lower electrode of a capacitor, must be formed very thick. As such, in the case of depositing a thick oxide film for a storage node pattern, many difficulties are involved in the etching process, and it is not easy to obtain a vertical profile after the etching process.

The cylinder structure is proposed as part of reducing the difficulty of the oxide etching process while increasing the capacitance of the capacitor and improving the etching profile of the concave structure.

Hereinafter, a method of forming a capacitor of a semiconductor device having a cylindrical structure according to the prior art will be described with reference to FIGS. 1A and 1B. 1A and 1B are cross-sectional views illustrating a method of forming a capacitor of a semiconductor device having a cylinder structure.

First, as shown in FIG. 1A, a semiconductor substrate 10 on which a semiconductor structure is formed is prepared through a series of semiconductor manufacturing processes. The semiconductor structure may include a well, an isolation layer, a word line, a junction region (source / drain region), a landing plug, a contact plug of bit line, a bit line, and an interlayer insulating layer. 11), the storage node contact plug 12. In this case, the storage node contact plug 12 may be formed in a single layer structure or in a stacked structure in order to secure an overlapping area of the capacitor with the storage.

Subsequently, an oxide film (hereinafter referred to as a sacrificial oxide film) 14 is sequentially formed as an insulating film for forming the etch stop film 13 and the storage node pattern on the semiconductor structure.

Subsequently, an etching process using an etching mask (not shown) for forming a storage node electrode is performed to sequentially etch the sacrificial oxide layer 14 and the etch stop layer 13 to expose the storage node contact plug 12. A pattern hole (not shown) to be formed is formed.

Subsequently, the TiN film 15 is deposited to the lower electrode of the capacitor along the stepped surface formed by the pattern hole.

Subsequently, as illustrated in FIG. 1B, an etching process 16 is performed to separate neighboring lower electrodes 15A from each other, thereby etching the TiN film 15 (see FIG. 1A). In this case, the etching process 16 is performed as a front side etching process without an etching mask, and the front side etching process is an anisotropic etching process using a dry etching method, and has a high density such as TCP (Transformer Coupled Plasma) and ICP (Inductively Coupled Plasma). Use plasma equipment. Here, as an etching gas, a plasma having a small amount of Cl ₂ added to Ar is used because the TiN film formed on the sacrificial oxide film 14 is more etched than the TiN film formed on the bottom of the pattern hole. This is to proceed with the process. As a result, the TiN film is present only inside the pattern hole, so that the lower electrodes 15A separated from each other are formed.

However, the following problem occurs in the capacitor forming method according to the related art described above.

As shown in FIG. 1B, when using a plasma in which a small amount of Cl ₂ is added to Ar in an etching process 16 performed to separate neighboring lower electrodes, 'A' shown in FIG. 1B and FIG. 2 are shown. As in 'B', the upper portion of the TiN film is pitted to generate fine points. The reason for this is that, as described above, a plasma having a small amount of Cl ₂ added to Ar is used as an etching gas in the etching process 16. The etching gas has a strong anisotropic etching characteristic and is formed on the bottom of the pattern hole. In comparison, the TiN film formed on the sacrificial oxide film 14 is more etched. That is, the TiN film formed on the sacrificial oxide film 14 is etched a lot, and eventually, an upper point is pitted so that a cusp that lowers the height of the sacrificial oxide film 14 is generated. If the point is severe, the point is broken during the removal process of the sacrificial oxide film 14 using the wet etching process to be separated from the lower electrode 15A to serve as a defect source of the conductive material. As a result, a dual bit fail or a multi-bit fail occurs, thereby lowering device characteristics, particularly yield.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and provides a method for forming a capacitor of a semiconductor device capable of preventing the peaks of the lower electrode generated after the etching process for separating the lower electrode of the capacitor. Its purpose is to.

According to an aspect of the present invention, there is provided a method of preparing a substrate on which a sacrificial pattern layer is formed, forming a lower electrode material along a stepped surface formed by the sacrificial pattern layer, and An etching process using an etching selectivity between an electrode material and the sacrificial pattern layer may be performed, and the etching process may be performed to etch the sacrificial pattern layer faster than the lower electrode material to form a separate lower electrode. It provides a method of forming a capacitor of a semiconductor device comprising.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. In addition, in the drawings, the thicknesses of layers and regions are exaggerated for clarity, and in the case where the layers are said to be "on" another layer or substrate, they may be formed directly on another layer or substrate or Or a third layer may be interposed therebetween. In addition, the same reference numerals throughout the specification represent the same components.

Example

3A and 3B are cross-sectional views illustrating a method of forming a capacitor of a semiconductor device having a cylinder structure according to an exemplary embodiment of the present invention.

First, as shown in FIG. 3A, a semiconductor substrate 110 on which a semiconductor structure is formed is prepared through a series of semiconductor manufacturing processes. The semiconductor structure may include a well, an isolation layer, a word line, a junction region (source / drain region), a landing plug, a bit line contact plug, a bit line, an interlayer insulating layer 111, and a storage node contact plug 112.

Subsequently, an oxide film (hereinafter referred to as a sacrificial oxide film) 114 is sequentially formed as an insulating film for forming the etch stop film 113 and the storage node pattern on the semiconductor structure.

Subsequently, the storage node may be etched by sequentially etching the sacrificial oxide layer 114 and the etch stop layer 113 by performing an etching process using an etching mask (not shown) for forming the storage node electrode to expose the storage node contact plug 112. A pattern hole (not shown) to be formed is formed.

Subsequently, a TiN film 115 is deposited on the lower electrode of the capacitor along the stepped surface formed by the pattern hole.

Subsequently, as illustrated in FIG. 3B, an etching process 116 is performed to separate neighboring lower electrodes, thereby etching the TiN film 115 (see FIG. 3A). In this case, the etching process 116 may bring the etching rate of the sacrificial oxide film 114 to at least 1: 2 or more faster than the etching rate of the TiN film 115 so as to prevent the occurrence of the sharpness shown in FIGS. 1B and 2. do.

Process condition 1

The etching process 116 is performed by a front side etching process without an etching mask, and the front side etching process is performed by dry etching using high density plasma equipment such as TCP and ICP.

Specifically, a plasma in which Cl ₂ and SF ₆ are mixed with Ar in a high density plasma apparatus such as TCP or ICP is used. At this time, the etching conditions are the pressure inside the chamber of the high-density plasma equipment is 5 ~ 50mTorr, source power (100 ~ 1000W), bias power (bias power) 0 ~ 300W, Ar flow rate 100 ~ 1000sccm, Cl ₂ The flow rate is set to 30 to 100 sccm, and the flow rate of SF ₆ is set to 30 to 100 sccm. In this case, it is preferable that the flow rate ratio of SF ₆ to Cl ₂ is 1: 1 to 1: 3, through which the etch rate of the TiN film 115 and the sacrificial oxide film 114 is at least 1: 2. .

In the exemplary embodiment of the present invention, since the TiN film 115 is formed to have a relatively thin thickness of 500 μs or less, and the etching uniformity is also poor, it is difficult to know the etching end point during the TiN 115 etching process. Therefore, even if the etch rate of the TiN film 115 is decreased, the SF ₆ relative to Cl ₂ may be larger than the etch rate of the TiN film 115 so that the etching rate of the sacrificial oxide film 114 is 1: 2 or more. By setting the ratio to 1: 1 or more and performing the etching process 116, it is possible to prevent the occurrence of dew points on the upper portion of the lower electrode 115A (the inner wall of the sacrificial oxide film 114). That is, as shown in the 'C' and 'D' shown in Figure 3b and Figure 4 it can be seen that there is no point.

Experimental Example

When the flow rate ratio of Cl ₂ : SF ₆ is 1: 1, the etching rate [μ / min] of the TiN film 115 is about 13 kPa, and the sacrificial oxide film 114 is about 36 kPa. On the other hand, when the flow rate ratio of Cl ₂ : SF ₆ was increased to 1: 2.5, the etching rate [ms / min] of the TiN film 115 was about 10 kPa, and the sacrificial oxide film 114 was about 37 kPa.

Process condition 2

The etching process 116 is performed by a front side etching process without an etching mask, and the front side etching process is performed by dry etching using high density plasma equipment such as TCP and ICP.

Specifically, a plasma in which Cl ₂ and NF ₃ are mixed with Ar is used in a high density plasma apparatus such as TCP or ICP. At this time, the etching conditions are 5 ~ 50mTorr pressure in the chamber of the high density plasma equipment, 100 ~ 1000W source power, 0 ~ 300W bias power, 100 ~ 1000sccm Ar flow rate, 30 ~ 100sccm, Cl ₂ flow rate, NF ₃ The flow rate of is set to 30 ~ 100sccm. At this time, the flow rate ratio of NF ₃ to Cl ₂ is preferably 1: 1 to 1: 3, and through this, the etch rate of the TiN film 115 and the sacrificial oxide film 114 is at least 1: 2 or more. do.

Process condition 3

The etching process 116 is performed by a front side etching process without an etching mask, and the front side etching process is performed by dry etching using high density plasma equipment such as TCP and ICP.

Specifically, a plasma in which Cl ₂ and CF ₄ are mixed with Ar in a high density plasma apparatus such as TCP or ICP is used. At this time, the etching conditions are the pressure inside the chamber of the high density plasma equipment is 5 ~ 50mTorr, the source power is 100 ~ 1000W, the bias power 0 ~ 300W, the Ar flow rate 100 ~ 1000sccm, Cl ₂ flow rate 30 ~ 100sccm, CF ₄ The flow rate of is set to 30 ~ 100sccm. At this time, the flow rate ratio of CF ₄ to Cl ₂ is preferably 1: 1 to 1: 3, and through this, the etching rate of the TiN film 115 and the sacrificial oxide film 114 is at least 1: 2 or more. .

Process condition 4

The etching process 116 is performed by a front side etching process without an etching mask, and the front side etching process is performed by dry etching using high density plasma equipment such as TCP and ICP.

Specifically, the TiN film 115 is first etched until the top of the sacrificial oxide film 114 is exposed using a plasma in which a small amount of Cl ₂ is added to Ar in a high density plasma apparatus such as TCP or ICP. At this time, the etching conditions are such that the pressure inside the chamber of the high density plasma equipment is 5-50 mTorr, the source power is 100-1000 W, the bias power is 0-300 W, and the flow ratio of Cl _{2 to} Ar is 100: 1-100: 20. . Then, transient etching is performed by secondary etching of the TiN film 115 using a plasma in which Cl ₂ and SF ₆ are mixed with Ar in-situ in the same chamber. At this time, the process conditions are 5 ~ 50mTorr pressure inside the chamber of the high density plasma equipment, 100 ~ 1000W source power, 0 ~ 300W bias power, 100 ~ 1000sccm Ar flow rate, 30 ~ 100sccm, Cl ₂ flow rate SF ₆ The flow rate of is set to 30 ~ 100sccm. In this case, it is preferable that the flow rate ratio of SF ₆ to Cl ₂ is 1: 1 to 1: 3, through which the etch rate of the TiN film 115 and the sacrificial oxide film 114 is at least 1: 2. .

Process condition 5

The etching process 116 is performed by a front side etching process without an etching mask, and the front side etching process is performed by dry etching using high density plasma equipment such as TCP and ICP.

Specifically, the TiN film 115 is first etched until the top of the sacrificial oxide film 114 is exposed using a plasma in which a small amount of Cl ₂ is added to Ar in a high density plasma apparatus such as TCP or ICP. At this time, the etching conditions are such that the pressure inside the chamber of the high density plasma equipment is 5-50 mTorr, the source power is 100-1000 W, the bias power is 0-300 W, and the flow ratio of Cl _{2 to} Ar is 100: 1-100: 20. . Then, transient etching is performed by secondary etching of the TiN film 115 using a plasma in which Cl ₂ and NF ₃ are mixed with Ar in the same chamber. At this time, the process conditions are 5 ~ 50mTorr pressure in the chamber of the high-density plasma equipment, 100 ~ 1000W source power, 0 ~ 300W bias power, 100 ~ 1000sccm Ar flow rate, 30 ~ 100sccm, Cl ₂ flow rate, NF ₃ The flow rate of is set to 30 ~ 100sccm. In this case, it is preferable that the flow rate ratio of NF ₃ to Cl ₂ is 1: 1 to 1: 3, through which the etch rate of the TiN film 115 and the sacrificial oxide film 114 is at least 1: 2 or more. .

Process condition 6

The etching process 116 is performed by a front side etching process without an etching mask, and the front side etching process is performed by dry etching using high density plasma equipment such as TCP and ICP.

Specifically, the TiN film 115 is first etched until the top of the sacrificial oxide film 114 is exposed using a plasma in which a small amount of Cl ₂ is added to Ar in a high density plasma apparatus such as TCP or ICP. At this time, the etching conditions are such that the pressure inside the chamber of the high density plasma equipment is 5-50 mTorr, the source power is 100-1000 W, the bias power is 0-300 W, and the flow ratio of Cl _{2 to} Ar is 100: 1-100: 20. . Then, transient etching is performed by secondary etching with respect to the TiN film 115 using a plasma in which Cl ₂ and CF ₄ are mixed in Ar in the same chamber. At this time, the process conditions are 5 ~ 50mTorr pressure inside the chamber of the high density plasma equipment, 100 ~ 1000W source power, 0 ~ 300W bias power, 100 ~ 1000sccm Ar flow rate, 30 ~ 100sccm, Cl ₂ flow rate CF ₄ The flow rate of is set to 30 ~ 100sccm. At this time, the flow rate ratio of CF ₄ to Cl ₂ is preferably 1: 1 to 1: 3, and through this, the etching rate of the TiN film 115 and the sacrificial oxide film 114 is at least 1: 2 or more. .

Meanwhile, after the lower electrode 115A is separated through the etching process 116, the sacrificial oxide film 114 is removed.

Subsequently, a dielectric film (not shown) and an upper electrode (not shown) are sequentially formed along the stepped surface formed by the lower electrode 115A. Thus, the capacitor having the cylinder structure is completed.

As described above, in each process condition in the etching process 116, Cl ₂ is used as the stock angular gas of the TiN film 115, and SF ₆ , NF ₃ , CF ₄ are the stock angular gas of the sacrificial oxide film 114. Used as Accordingly, when the flow rate ratio of Cl ₂ and SF ₆ (or NF ₃ and CF ₄ ) is appropriately adjusted during the etching process 116, the etching selectivity of the sacrificial oxide film 114 with respect to the TiN 115 may be adjusted.

Although the technical spirit of the present invention has been described in detail in the preferred embodiments, it should be noted that the above-described embodiments are for the purpose of description and not of limitation. In addition, it will be understood by those skilled in the art that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, according to the present invention, the etching selectivity between the TiN film and the sacrificial oxide film is controlled during the etching process for separating the lower electrode of the capacitor so that the sacrificial oxide film is etched at least twice as fast as the TiN film. By doing so, it is possible to prevent the upper point of the lower electrode, thereby improving the characteristics of the device to improve the yield.

Claims (15)

Preparing a substrate on which a sacrificial pattern layer is formed; Forming a material for the lower electrode along the stepped surface formed by the sacrificial pattern layer; And An etching process is performed using an etching selectivity between the lower electrode material and the sacrificial pattern layer, wherein the etching process is performed to etch the sacrificial pattern layer faster than the lower electrode material to form a separated lower electrode. step Capacitor formation method of a semiconductor device comprising a. The method of claim 1, The etching process is a capacitor forming method of a semiconductor device is performed under an etching condition that the sacrificial pattern layer is etched at least two times faster than the material for the lower electrode. The method of claim 1, And a TiN film as the lower electrode material, and the sacrificial pattern layer is formed of an oxide film. The method of claim 3, wherein The etching process is a capacitor forming method of a semiconductor device performed using a high density plasma equipment. The method of claim 4, wherein The etching process is a capacitor forming method of a semiconductor device performed by using a plasma mixed with Ar and Cl ₂ and SF ₆ . The method of claim 4, wherein The etching process, Selectively etching the material for the lower electrode until the top of the sacrificial pattern layer is exposed using a plasma containing Cl ₂ added to Ar; And Overetching the material for the lower electrode using a plasma in which the Cl ₂ and SF ₆ are mixed with the Ar; Capacitor formation method of a semiconductor device comprising a. The method according to claim 5 or 6, And a flow rate ratio of the SF ₆ to the Cl ₂ is 1: 1 to 1: 3. The method of claim 4, wherein The etching process is a capacitor forming method of a semiconductor device performed by using a plasma mixed with Ar and Cl ₂ and NF ₃ . The method of claim 4, wherein The etching process, Selectively etching the material for the lower electrode until the top of the sacrificial pattern layer is exposed using a plasma containing Cl ₂ added to Ar; And Overetching the material for the lower electrode using a plasma in which the Cl ₂ and NF ₃ are mixed with Ar; Capacitor formation method of a semiconductor device comprising a. The method according to claim 8 or 9, And a flow rate ratio of the NF ₃ to the Cl ₂ is 1: 1 to 1: 3. The method of claim 4, wherein The etching process is a capacitor forming method of a semiconductor device performed by using a plasma mixed with Ar and Cl ₂ and CF ₄ . The method of claim 4, wherein The etching process, Selectively etching the material for the lower electrode until the top of the sacrificial pattern layer is exposed using a plasma containing Cl ₂ added to Ar; And Overetching the material for the lower electrode using a plasma in which the Cl ₂ and CF ₄ are mixed with Ar; Capacitor formation method of a semiconductor device comprising a. The method according to claim 11 or 12, And a flow rate ratio of the CF ₄ to the Cl ₂ is 1: 1 to 1: 3. The method according to any one of claims 6, 9 or 12, Selectively etching the lower electrode material and over-etching the lower electrode material in-situ. The method according to any one of claims 5, 6, 8, 9, 11 or 12, In the etching process, the capacitor is formed at a pressure of 5 to 50 mTorr, a source power of 100 to 1000 W, a bias power of 0 to 300 W, and a flow rate ratio of the Cl ₂ to the Ar is 100: 1 to 100: 20. Way.

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