KR20080013174A - Method for isolation of storagenode in capacitor - Google Patents

Abstract

A method for isolating a storage node of a capacitor is provided to prevent a lower layer from being attacked in a subsequent wet deep out process by blocking damage of a bottom of the storage node. A sacrificial layer(22) is formed on a lower layer(21) on which a predetermined lower structure is formed. A part of the sacrificial layer is etched to form plural open regions(23). A conductive layer(24) is formed on the entire surface along a surface shape of the open region. A capping layer(25A) is formed in the open region. The conductive layer outside the open region is etched with a dry etching process using plasma to perform isolation between storage nodes. The conductive layer is selectively etched until a surface of the sacrificial layer is exposed, and then the conductive layer, the sacrificial layer, and the capping layer are etched at the same time. When the capping layer is formed in the open region, the capping layer is deposited on the entire surface until the open region is filled. The capping layer remains only in the open region through a wet etching.

Description

How to remove a storage node from a capacitor {METHOD FOR ISOLATION OF STORAGENODE IN CAPACITOR}

1A to 1C are cross-sectional views illustrating a method of separating a storage node using a plasma front etching method according to the related art.

2 shows an attack of an underlying layer according to the prior art;

3A to 3F are cross-sectional views illustrating a method of manufacturing a capacitor according to an embodiment of the present invention.

Figure 4a is a photograph showing the results after the plasma front dry etching in accordance with the prior art.

Figure 4b is a photograph showing the results after the plasma front dry etching in accordance with an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

21: lower layer 22, 22A: sacrificial oxide film

23: open area 24, 24A, 24B: conductive film

25, 25A, 25B: capping oxide film

The present invention relates to a method of manufacturing a capacitor, and more particularly, to a storage node isolation method.

As the degree of integration of semiconductor devices increases, the area in which the devices are implemented is decreasing. However, in the case of a semiconductor device such as DRAM, the minimum necessary capacitance of the capacitor must be secured even if the device area is reduced. Various measures to secure the capacitance have been studied, for example, a method of increasing the effective surface area by making a lower electrode of a capacitor into a three-dimensional structure, a method of using a high-k dielectric material in the dielectric film of the capacitor, and a metallic material as the electrode of the capacitor How to use is currently introduced.

When manufacturing a capacitor which forms the lower electrode in the three-dimensional structure with the metal-based lower electrode, the separation process of the lower electrode is essential.

The separation process of the lower electrode is generally known using a chemical mechanical polishing (CMP) process or an etch-back process. However, the chemical mechanical polishing process has a disadvantage in that the electrode material is not removed at the local step, causing problems as residual impurities in subsequent processes.

Therefore, recently, the entire surface etching method has been applied in the lower electrode separation process.

1A and 1B are cross-sectional views illustrating a method of separating a storage node using a plasma front etching method according to the related art.

As shown in FIG. 1A, after depositing a sacrificial insulating layer 12 on a lower layer 11 having a predetermined process, the sacrificial insulating layer 12 is etched to form an open region 13 in which a storage node is to be formed. To form.

Subsequently, a conductive film 14 to be used as a storage node is deposited on the sacrificial insulating film 12 along the surface shape of the open region 13.

Thereafter, the storage node separation process is performed, and the entire surface etching is performed using plasma. That is, the conductive film 14 is etched until the upper surface of the sacrificial insulating film 13 is exposed.

Then, as illustrated in FIG. 1B, the conductive layer 14 is completely removed from the upper surface of the sacrificial insulating layer 12 to separate the storage nodes, and the conductive layer 14 remains only inside the open region 13.

However, in the storage node separation process according to the related art, the conductive layer 14 remains in the form of a spacer on the upper sidewall of the open region 13 to form a point (ie, a sharp end) (see 'H'). There is. As described above, the generation of the peaks H occurs because only the conductive film 14 is selectively etched during the entire surface etching.

For example, as the conductive film 14 to as TiN, to dry etching using a Cl _2, and Ar is mixed with Cl ₂ / Ar plasma at the front etch, Cl ₂ / Ar plasma is only TiN selectively etching the front Due to the nature of etching, the occurrence of sharp peaks on the upper sidewall of the open region 13 is inevitable.

In this way, the upper sidewall of the open region 13 remains in the form of a spacer to form a peak (that is, a sharp end), through which leakage current occurs.

As such, the sharpness H remaining on the sidewall has a problem of acting as a bridge between neighboring storage nodes while performing an insulating film dip out process to form a cylinder capacitor.

In addition, the storage node at the bottom of the open area during the front dry etching is partially damaged, and the capacitor underlayer is attacked by the wet chemical during the deep out.

FIG. 2 is a view illustrating an attack of a lower layer according to the prior art. When a sacrificial insulating layer is removed through a wet deep out to form a cylinder structure exposing both an inner wall and an outer wall of a storage node, an attack occurs in the lower layer. It can be seen.

In other words, if the storage node at the bottom of the open area is partially damaged, the wet chemical used for the wet deep-out penetrates into the lower layer through the grain boundary of the thinned portion of the storage node, thereby bunkering the insulating layer of the lower layer. Causes defects such as

The above-described problems occur when a metal electrode such as Ru or Pt is used in addition to TiN as a storage node.

The present invention has been proposed to solve the above problems of the prior art, and an object of the present invention is to provide a storage node separation method of a capacitor capable of removing a peak during a storage node separation process.

In addition, another object of the present invention is to provide a method of manufacturing a capacitor that can prevent the attack of the lower layer by the wet chemical during the subsequent wet deep-out process.

The storage node separation method of the capacitor of the present invention for achieving the above object comprises the steps of forming a sacrificial film on the lower layer formed with a predetermined lower structure; Etching a portion of the sacrificial layer to form a plurality of open regions; Forming a conductive film on an entire surface of the open region along the surface shape of the open region; Forming a capping layer in the open region; And etching the conductive layer outside the open region by a front dry etching using plasma to selectively separate the storage nodes, and selectively etching the conductive layer until the surface of the sacrificial layer is exposed, and then the conductive layer, the sacrificial layer, and the like. And etching the capping film at the same time.

In addition, the method of manufacturing the capacitor of the present invention comprises the steps of: forming a sacrificial oxide film on a lower layer on which a predetermined lower structure is formed; Etching a portion of the sacrificial oxide layer to form a plurality of open regions; Forming TiN on the entire surface along the surface shape of the open region; And forming a capping oxide film in the open area. Performs separation between storage nodes by etching TiN outside the open region by a front dry etching using a plasma, and selectively etching only TiN until the surface of the sacrificial oxide is exposed, after which the TiN, the sacrificial oxide layer, and the capping are performed. And etching the oxide film simultaneously.

Hereinafter, the preferred 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. .

3A to 3F are cross-sectional views illustrating a method of manufacturing a capacitor according to an embodiment of the present invention.

As shown in FIG. 3A, the sacrificial insulating layer 22 is formed on the lower layer 21 on which the predetermined lower structure is formed. Although not shown, a storage node contact is formed in the lower layer 21, for example, which is connected to the storage node of the capacitor. The material of the sacrificial insulating film 22 is preferably, for example, a silicon oxide film, but other kinds of oxide films may be used. In addition, a silicon nitride layer, which is an etch stopper, may be formed between the lower layer 21 and the sacrificial insulating layer 22.

Subsequently, a portion of the sacrificial insulating layer 22 is etched to form a plurality of open regions 23 exposing predetermined regions (eg, storage node contacts) of the lower layer 21.

As shown in FIG. 3B, a conductive film 24 to be used as a storage node is deposited on the entire surface of the open region 23. Here, the conductive film 24 is a metal film or a metal compound, and includes any one selected from the group consisting of TiN, Ti, W, Pt, Ru, RuO ₂ and IrO ₂ , for example.

Subsequently, a capping oxide 25 is applied to the entire surface of the resultant to completely fill the inside of the open area 23. Here, the material constituting the capping oxide film 25 is also preferably a silicon oxide film like the sacrificial insulating film 22, but other kinds of oxide films may be used.

The capping oxide film 25 described above is deposited to a thickness of at least 1000 kPa so that the thickness of 600 kPa or more remains on the conductive film 24 while filling the inside of the open region 23. To this end, the capping oxide layer 25 is deposited by atomic layer deposition (ALD). Although not shown, the height difference of the capping oxide film between the cell region and the peripheral circuit region is set to 100 mW or less.

As shown in FIG. 3C, the capping oxide film 25 is selectively etched to leave the capping oxide film 25A only in the open region 23. As such, wet etching is performed with hydrofluoric acid (HF) solution using a spin dry method in order to leave the capping oxide film 25A only in the open region 23.

When the surface of the conductive film 24 is exposed by the wet etching by the rotary drying method as described above, the loss of the capping oxide film 25A in the open region 23 is not more than 2000 μs.

In the capping oxide film 25A remaining in the open region 23 by the above-described series of processes, the bottom conductive film 24 of the open region 23 is lost during the dry plasma etching of the subsequent conductive film 24. It is to prevent becoming.

On the other hand, when the capping oxide film 25, which is an oxide film material, is etched by a dry etching method, the surface of the exposed conductive film 24 is damaged. Therefore, it is preferable to proceed by wet etching.

As shown in FIGS. 3D and 3E, the entire surface dry etching process using plasma is performed on the conductive layer 24.

The plasma dry etching of the conductive film 24 proceeds in two steps as follows.

First, the first step shown in FIG. 3D (primary etching) ensures that almost no oxide material is lost during the etching of the conductive film 24. That is, when the conductive layer 24 is etched, the oxide material has a very high etching selectivity, so that the oxide layer material should not be lost. Therefore, only the conductive film 24 on the surface of the sacrificial insulating film 22 is selectively dry-etched by the first step, and the capping oxide film 25A and the sacrificial insulating film 22 which are oxide materials are not etched.

In the first step, the conductive film 24A remains in the open region.

Next, the second step (secondary etching) shown in FIG. 3E proceeds with a selectivity of at least 2: 1 with the oxide material. That is, while the conductive film and the oxide material are etched simultaneously, the conductive film 24A proceeds at a select ratio such that the etching is faster than the oxide film material. Accordingly, the sacrificial insulating film 22, the capping oxide film 25A, and the conductive film 24A are all etched, and the reference numerals 22A, 25B, and 24B are respectively shown in the profile after the first etching (see reference numeral 'P'). Change to form.

As such, the sacrificial insulating film 22 and the capping oxide film 25A and the selectivity are maintained at least 2: 1 or more (2: 1 to 10: 1), so that the upper portion of the conductive film 24B in the open region 23 is maintained. Is etched in a shape having a lower height than the sacrificial insulating film 22A. Preferably, the capping oxide film 25B has the lowest height, the surface of the sacrificial insulating film 22A is the highest, and the upper surface of the conductive film 24B is located at the middle height thereof. As described above, if the conductive film 24B, the sacrificial insulating film 22A, and the capping oxide film 25B are simultaneously etched, the conductive film 24B can be left without a point. Here, the conductive film 24B becomes a storage node.

As the plasma etching apparatus for plasma dry etching as described above, ICP (Inductively Coupled Plasma), ECR (Electron Cyclotron Resonance), microwave (Microwave), CCP (Capacitively Coupled Plasma) and the like are used.

For example, when the conductive film 24B is TiN, the first and second steps are performed using the following recipe.

First, in the first step, a total dry etching is performed using a plasma in which chlorine-based gas and inert gas are mixed so that oxide material is hardly lost. At this time, the chlorine-based gas uses Cl ₂ , the inert gas is used argon (Ar) gas. That is, Cl ₂ / Ar plasma is used.

Next, in the second step, the oxide material and the TiN are simultaneously etched, and the entire dry etching is performed by using a plasma mixed with chlorine gas, an inert gas, and a fluorine gas to etch TiN faster than the oxide material. In this case, chlorine-based gas is used Cl ₂ , inert gas is used argon (Ar) gas, fluorine-based gas is used SF ₆ gas. That is, SF ₆ / Cl ₂ / Ar plasma is used. Here, when SF ₆ is used, the selectivity between TiN and the oxide film material is at least 2: 1. Preferably, the flow rate ratio of SF ₆ / Cl _{2 in} the SF ₆ / Cl ₂ / Ar plasma is 0.4 to 2.5 to obtain the above selectivity.

As described above, the substrate temperature during the plasma dry etching of TiN proceeding to the first and second steps is 20 to 40 ° C, and the bias power is 100 to 200W.

In the above-described example, the case where the conductive film for the storage node is TiN has been described. However, the present invention can be applied to the case where any one selected from Ti, W, Pt, Ru, RuO ₂ or IrO ₂ is used as the storage node.

As described above, since the plasma dry etching is performed while minimizing the loss of the oxide material, the storage nodes can be separated from each other without reducing the height of the storage nodes and without any additives.

Thereafter, a washing process using an acetone (ACT) solution is performed to remove the polymer generated during the dry etching. At this time, since the polymer may act as a bridge between storage nodes, it must be removed.

As shown in FIG. 3F, the capping oxide layer 25B and the sacrificial insulating layer 22A are removed by performing a wet deep out process. At this time, the wet dipout process uses a hydrofluoric acid solution.

Therefore, after the wet deep-out process, both the inner wall and the outer wall of the storage node 24B are exposed, thereby making the storage node 24B a cylinder structure.

Meanwhile, the wet chemical does not penetrate through the bottom portion of the storage node 24B during the wet deep out process. This is because an attack at the bottom of the storage node 24B is prevented by the capping oxide film 25B during the plasma dry etching.

Figure 4a is a photograph showing the result after the plasma front dry etching according to the prior art, Figure 4b is a photograph showing the result after the plasma front dry etching according to an embodiment of the present invention. 4A and 4B, the storage node uses TiN.

Referring to FIGS. 4A and 4B, it can be seen that when the plasma front dry etching is performed according to an exemplary embodiment of the present invention, no peaking occurs at the top of the storage node. On the other hand, in Figure 4a of the prior art it can be seen that sharp point is occurring sharply.

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

The present invention described above has the effect of preventing the occurrence of bridges by separating the storage node without a peak at the top of the storage node by proceeding by dividing the selection ratio in two steps during the storage node separation process.

In addition, the present invention has the effect of preventing the damage of the bottom of the storage node by attacking the bottom layer during the subsequent wet deep-out process by proceeding in the state in which the capping oxide film remaining in the open area during the storage node separation process. .

Claims (16)

Forming a sacrificial layer on an underlayer on which a predetermined understructure is formed; Etching a portion of the sacrificial layer to form a plurality of open regions; Forming a conductive film on an entire surface of the open region along the surface shape of the open region; Forming a capping layer in the open region; And The conductive layer outside the open area is etched by using a plasma front surface etching to separate the storage nodes, and the conductive layer is selectively etched until the surface of the sacrificial layer is exposed, and then the conductive layer, the sacrificial layer, and the capping are performed. Simultaneously etching the membrane Storage node separation method of the capacitor comprising a. The method of claim 1, Front dry etching using the plasma, A method for separating a storage node of a capacitor, which proceeds by dividing into primary etching for selectively etching only the conductive film, and etching simultaneously while maintaining a selectivity ratio between the conductive film, the sacrificial film, and the capping film at least 2: 1. The method of claim 1, Forming a capping film inside the open area, Depositing a capping film over the entire surface until the open region is filled; And Leaving the capping layer only inside the open region through wet etching; Storage node separation method of the capacitor comprising a. The method of claim 3, The capping layer is formed of an oxide film, and the wet etching method of separating the storage node of the capacitor by wet etching with hydrofluoric acid solution using a rotary drying method. The method of claim 3, Depositing the capping film, Storage node separation method of a capacitor deposited by atomic layer deposition. The method of claim 1, After the front dry etching using the plasma, A storage node separation method of performing a cleaning process using an acetone solution to remove the polymer generated during the dry etching. Forming a sacrificial oxide film on a lower layer on which a predetermined lower structure is formed; Etching a portion of the sacrificial oxide layer to form a plurality of open regions; Forming TiN on the entire surface along the surface shape of the open region; Forming a capping oxide film in the open region; And Performs separation between storage nodes by etching TiN outside the open region by a front dry etching using plasma, and selectively etching only TiN until the sacrificial oxide surface is exposed, and then the TiN, sacrificial oxide layer and capping oxide layer. Simultaneously etching Method of manufacturing a capacitor comprising a. The method of claim 7, wherein Front dry etching using the plasma, And a method of manufacturing a capacitor by dividing the first and second etching selectively and selectively etching the TiN while simultaneously maintaining the selectivity of the TiN, the sacrificial oxide layer, and the capping oxide layer at least 2: 1. The method of claim 8, The first etching is performed using a plasma mixed with a chlorine-based gas and an inert gas, the second etching is a manufacturing method of a capacitor using a plasma mixed with a chlorine-based gas, an inert gas and a fluorine-based gas. The method of claim 9, The chlorine-based gas is Cl ₂ , the inert gas is used argon, the fluorine-based gas is SF ₆ manufacturing method of a capacitor. The method of claim 10, The ratio of the flow rate (SF ₆ / Cl ₂ ) of SF ₆ to Cl ₂ at the time of the secondary etching is in the range of 0.4 to 2.5. The method according to any one of claims 7 to 11, In the front surface dry etching using the plasma, the substrate temperature is 20 to 40 ℃, the bias power is used for the capacitor manufacturing method of 100 to 200W. The method of claim 7, wherein Forming a capping oxide film in the open area, Depositing a capping oxide layer over the entire surface until the open region is filled; And Leaving the capping oxide layer only inside the open region through wet etching; Method of manufacturing a capacitor comprising a. The method of claim 13, The wet etching, A method for producing a capacitor wet etching with hydrofluoric acid solution using a rotary drying method. The method of claim 13, Depositing the capping oxide film, A method for producing a capacitor deposited by atomic layer deposition. The method of claim 7, wherein After the front dry etching using the plasma, Performing a washing process using an acetone solution to remove the polymer generated during the dry etching; And Removing both the sacrificial oxide layer and the capping oxide layer through a wet deep out; Method of manufacturing a capacitor further comprising.

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