KR101073129B1 - Method for isolation of storagenode in capacitor - Google Patents

Abstract

An object of the present invention is to provide a method of removing a storage node of a capacitor which can remove a sharp point during a storage node separation process and can prevent the storage node of the open area bottom from being damaged during front etching. The node separation method may include 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 performing the separation between the storage nodes by etching the conductive layer with two blanket etch having the selectivity between the conductive layer and the sacrificial layer, wherein the present invention is selected during the storage node separation process. By dividing the ratio into two steps with different ratios, there is an effect of preventing the occurrence of bridges by separating the storage node without a peak at the top of the storage node.

Capacitor, Storage Node Separation, Capping Oxide, Plasma, Etching, Point

Description

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

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

2A to 2F are cross-sectional views illustrating a method of manufacturing a capacitor according to 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 that forms the storage node in a three-dimensional structure with the metal-based lower electrode, the storage node separation process is essential.

The separation process of the storage node is generally known using a chemical mechanical polishing (CMP) process or a blanket etch 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 is applied to the storage node separation process.

1A and 1B are cross-sectional views illustrating a method of separating a storage node using front etching 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 on the upper sidewall of the open region 13 in the form of a spacer 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 is partially damaged during the front surface etching, and the capacitor underlayer is attacked by the wet chemical during the deep out.

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 the storage node separation process.

Another object of the present invention is to provide a storage node separation method of a capacitor which can prevent the storage node of the open area bottom from being damaged during the front surface etching.

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 performing separation between storage nodes by etching the conductive layer with two blanket etch having different selectivity between the conductive layer and the sacrificial layer. When the conductive film is etched, the first etching is performed by increasing the selectivity of the sacrificial layer and the second etching is performed simultaneously without etching the selectivity of the conductive film and the sacrificial layer. When the sacrificial layer is exposed using the EPD) method, it is characterized in that the conversion to the second etching immediately.

Preferably, the conductive film is a TiN film, and the second front surface etching of the TiN film is performed by first etching using a plasma mixed with a chlorine-based gas and an inert gas, and a plasma containing a chlorine-based gas, an inert gas, and a fluorine-based gas is mixed. It characterized in that the secondary etching using.

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. .

2A to 2F are cross-sectional views illustrating a method of separating a storage node of a capacitor according to an embodiment of the present invention.

As shown in FIG. 2A, 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. 2B, 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. On the other hand, although not shown, the capping oxide film 25 also serves to prevent the conductive film 24 from being damaged during an etching process for removing defects at the wafer edge, which is commonly known as a bevel etch.

As shown in FIG. 2C, the capping oxide layer 25 is selectively etched to leave the capping oxide layer 25A only in the open region 23. As such, wet etching is performed with hydrofluoric acid (HF) solution in order to leave the capping oxide layer 25A only in the open region 23. Here, the height of the capping oxide film 25A is the middle height of the open region 23.

The capping oxide film 25A remaining in the open region 23 by the above-described series of steps is lost when the bottom conductive film 24 of the open region 23 is lost during the subsequent plasma etching of the conductive film 24. It is to prevent that.

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. 2D and 2E, the front surface etching using the plasma is performed on the conductive layer 24.

The plasma entire surface etching of the conductive layer 24 proceeds in two steps as follows.

First, the first step shown in FIG. 2D (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 addition, the first step is etched using an end point detection method, so that the oxide material is exposed to the next second step.

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

Next, the second step (secondary etching) shown in FIG. 2E proceeds to the condition where there is no selectivity with respect to the oxide material. In other words, the conductive film and the oxide material may be simultaneously etched (see reference numeral 'P') to leave the conductive film 24B without a dot. Here, the conductive film 24B becomes a storage node.

As a plasma etching apparatus for plasma front etching as described above, a TCP (Transformer Coupled Plasma) type is 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, the entire surface is etched by using a plasma in which chlorine 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. In addition, the first step uses an End Point Detection system (using a TiCl waveform) to switch to the next second step as soon as the oxide is exposed to minimize oxide loss at the top sidewall of the open area. Here, the end point detection means that only Ti and N peaks are detected during the TiN etching, but the etching is completed when the peaks of the Si and O oxides are detected.

Next, in the second step, the front surface etching is performed by using a plasma mixed with a chlorine gas, an inert gas, and a fluorine gas to simultaneously etch the oxide material and TiN without a selectivity. 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. In this case, when SF ₆ is used, the selectivity between TiN and the oxide film is 1: 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 so that no residue is generated in the open region 23.

As described above, the substrate temperature during the plasma dry etching of TiN proceeding to the first step and the second step is 20 to 40 ° C, and the bias power is 100 to 200W. As such, using bias power below 200 W minimizes TiN attack at the bottom of the open area.

As described above, when TiN is etched using plasma of different mixed gases, the storage nodes may be separated from each other without height reduction and peaks of the storage nodes.

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.

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

As shown in FIG. 2F, 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 front surface etching.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. 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 a state in which the capping oxide film remaining in the open area during the storage node separation process. .

Claims (13)

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 Etching the conductive layer with two blanket etch having the selectivity between the conductive layer and the sacrificial layer to perform separation between storage nodes; Storage node separation method of the capacitor comprising a. Claim 2 has been abandoned due to the setting registration fee. The method of claim 1, The two front etchings, The method of claim 1, wherein the etching of the conductive layer is performed by increasing the selectivity of the sacrificial layer and performing secondary etching to simultaneously etch without selecting the conductive layer and the sacrificial layer. Claim 3 was abandoned when the setup registration fee was paid. The method of claim 2, The first etching method, the storage node separation method of the capacitor to switch to the second etching immediately when the sacrificial layer is exposed using an end point detection (EPD) method. Claim 4 was abandoned when the registration fee was paid. 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 to fill a portion of the open region by wet etching; Storage node separation method of the capacitor comprising a. Claim 5 was abandoned upon payment of a set-up fee. 5. The method of claim 4, The capping layer is formed of an oxide film, the wet etching is a storage node separation method of a capacitor to proceed with a hydrofluoric acid solution. Claim 6 was abandoned when the registration fee was paid. The method of claim 1, After the over etching, A storage node separation method of performing a cleaning process using acetone solution to remove the polymer generated during the front surface etching. Claim 7 was abandoned upon payment of a set-up fee. The method of claim 1, The method of claim 1, wherein the sacrificial layer is formed of an oxide layer. Claim 8 was abandoned when the registration fee was paid. The method according to any one of claims 1 to 7, The conductive film is a TiN film storage node separation method of a capacitor. Claim 9 was abandoned upon payment of a set-up fee. The method of claim 8, Twice the front etch of the TiN film, A method of separating a storage node of a capacitor in which primary etching is performed using a plasma mixed with chlorine gas and inert gas, and secondary etching is performed using plasma in which chlorine gas, inert gas and fluorine gas are mixed. Claim 10 was abandoned upon payment of a setup registration fee. 10. The method of claim 9, The chlorine-based gas is Cl ₂ , the inert gas is used argon (Ar), the fluorine-based gas is SF ₆ using a storage node separation method. Claim 11 was abandoned upon payment of a setup registration fee. 10. The method of claim 9, And a flow rate ratio of the fluorine-based gas to the chlorine-based gas during the second etching is in the range of 0.4 to 2.5. Claim 12 was abandoned upon payment of a registration fee. 10. The method of claim 9, The substrate temperature of the primary and secondary etching is 20 ~ 40 ℃, the secondary etching method of the storage node of the capacitor using a bias power of 100 to 200W. Claim 13 was abandoned upon payment of a registration fee. 10. The method of claim 9, The storage node separation method of the capacitor using the end point detection (EPD) method using the TiCl waveform during the first etching.

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