KR20020013276A - A method for formation of semiconductor capacitors comprising noble metal plate-electrode - Google Patents

Abstract

PURPOSE: A method for forming a capacitor of a semiconductor device having an upper electrode including a noble metal layer is provided to make a barrier metal layer and a polysilicon layer absorb residual thermal stress generated on the noble metal layer in a heat treatment process, by forming a tri layer composed of the noble metal layer, the barrier metal layer and the polysilicon layer as an upper electrode of a dielectric layer. CONSTITUTION: A lower electrode(103) connected to a predetermined active region of a semiconductor substrate(100) is formed on the substrate. The dielectric layer(104) is formed on the lower electrode. The noble metal layer(105) is formed on the dielectric layer. A conductive barrier metal layer(106) and the polysilicon layer(107) are sequentially formed on the noble metal layer. The upper electrode composed of the noble metal layer, the barrier metal layer and the polysilicon layer is formed.

Description

A method for formation of semiconductor capacitors comprising noble metal plate-electrode

The present invention relates to a method of forming a capacitor of a semiconductor device, and more particularly, to a method of forming a capacitor of a semiconductor device having an upper electrode including a noble metal such as Ru and Pt.

As the degree of integration of semiconductor devices increases, research into capacitors having high dielectric constant materials such as Ta ₂ O ₅ or a material having a perovskite structure such as BST or PZT as a dielectric film has been actively conducted. Conventionally, polysilicon is mainly used as an upper electrode of a capacitor. However, dielectric films with high dielectric constants generally not only affect the electrical properties of capacitors due to their interaction with polysilicon, ie, the diffusion of oxygen atoms in dielectric films into polysilicon, but also when polysilicon is used as electrode Since silicon has a small work function, there is a problem in that the leakage current is large. Therefore, research using a rare earth metal such as Ru, Pt as an electrode as an alternative material is in progress.

However, some problems occur when the precious metal electrode is used as the electrode of the capacitor. In particular, when the precious metal electrode is used as the upper electrode, the following problems occur.

According to the prior art using polysilicon as the upper electrode, after the dielectric film is formed, polysilicon is deposited over the entire surface of the semiconductor substrate, wherein the polysilicon deposited in the cell region is used as the upper electrode of the capacitor, and the ferry region Polysilicon deposited on is used as a resistance element. Therefore, when the upper electrode is formed by Ru or Pt alone, there is a problem that the resistance value is lower than that of polysilicon so that the resistance element cannot be formed in the ferry region.

In addition, Ru or Pt may degrade electrical characteristics due to residual thermal stress in a subsequent heat treatment process after forming the upper electrode. Ru or Pt has good permeability to gases such as hydrogen or oxygen, and there is a risk that the dielectric film or other semiconductor devices under the capacitor are exposed to the atmosphere gas in a subsequent process, for example, a hydrogen atmosphere heat treatment process for improving transistor characteristics.

An object of the present invention is to provide a method of forming a capacitor having a precious metal electrode as an upper electrode, the method of forming a capacitor which is highly compatible with a subsequent process and reliable.

1 to 3 are cross-sectional views illustrating a method of forming a capacitor according to an embodiment of the present invention.

The present invention includes forming a lower electrode connected to a predetermined active region of the substrate on a semiconductor substrate, forming a dielectric film on the lower electrode and forming a noble metal layer on the dielectric film, on the noble metal layer A method of forming a capacitor of a semiconductor device, the method comprising forming a conductive barrier metal layer and a polysilicon film sequentially to form an upper electrode formed of a triple layer of a noble metal layer / barrier metal layer / polysilicon film.

The dielectric film may be used in combination or in combination with a silicon oxide film, a silicon nitride film or an alumina film. In addition, a material film having a perovskite crystal structure such as a tantalum oxide film (Ta ₂ O ₅ ) having a high dielectric constant or a BST film or a PZT film may be used.

The noble metal layer is characterized in that formed of Ru or Pt. According to an embodiment of the present invention, the noble metal layer is formed to a thickness of about 50 to 1000 kPa, and preferably is formed to a thickness of 100 to 500 kPa.

According to an embodiment of the present invention, after the forming of the dielectric film or the forming of the noble metal layer, the step of heat treatment in an oxidizing atmosphere may be further included.

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

<Example>

1 to 4 are cross-sectional views for explaining a step of forming a stacked capacitor according to the present invention.

FIG. 1 illustrates a state where a contact plug 102 is formed to connect a source region of a semiconductor substrate 100 to a lower electrode of a semiconductor capacitor. Referring to the process of forming the contact plug 102, first, the interlayer insulating layer 101 on the semiconductor substrate is patterned to form a contact hole connecting the lower electrode and the source region of the semiconductor substrate. Although not shown in FIG. 1, an element such as a transistor is formed between the interlayer insulating film 101 and the semiconductor substrate 100. Subsequently, the contact hole is filled with a conductive material such as polysilicon to form the contact plug 102. The process of embedding the polysilicon may be performed through a planarization process through chemical mechanical polishing after polysilicon is deposited. A barrier metal layer (not shown) may be further formed on the contact plug 102 and the interlayer insulating film 101 to prevent diffusion of oxygen atoms into the contact plug 102 in a subsequent heat treatment process, for example, an oxygen atmosphere heat treatment process.

Referring to FIG. 2, a polysilicon film is formed on the contact plug 102 and the interlayer insulating film 101 by the lower electrode 103 by a conventional method, such as chemical vapor deposition. In place of polysilicon, conductive metal nitrides such as TiN, TaN, TaSiN, TiAlN, etc., which are vapor deposited by chemical vapor deposition, and precious metal electrodes such as Pt and Ru formed by organometallic chemical vapor deposition (MOCVD) may be used. In addition, the lower electrode 103 may be a multilayer in which the polysilicon, the conductive metal nitride, or the noble metal electrode is stacked.

Subsequently, a dielectric film 104 is formed on the lower electrode 103 by a conventional method. As the dielectric film 104, a silicon oxide film, a silicon nitride film, or an alumina film may be used or combined. In addition, a tantalum oxide film having a high dielectric constant or a material film having a perovskite crystal structure such as a BST film or a PZT film may be used. The conventional method may vary depending on the dielectric film, which means that the silicon oxide film, tantalum oxide film, or alumina film may be formed by chemical vapor deposition, and in the case of silicon nitride film, the organic metal in the PECVD method, the BST film, and the PZT film. It can be formed by vapor deposition (MOCVD).

If necessary, a heat treatment step may be added to improve electrical characteristics of the dielectric film 104. For example, when the dielectric film is an oxide film, heat treatment is performed at a temperature of about 200 to 600 ° C. and an ozone atmosphere (O ₃ ) or an oxygen atmosphere (O ₂ or N ₂ O) to densify the film quality and improve leakage current characteristics. Can be. In addition, the heat treatment step may be performed after the subsequent noble metal layer forming step.

3 is a cross-sectional view for explaining the formation of the upper electrode 108 of the multilayer of the present invention on the dielectric film 104. In detail, first, a noble metal layer 105 such as Pt or Ru is formed on the dielectric layer 104 by an organometallic vapor deposition method or a sputtering method. The precious metal layer 105 may be formed to a thickness of about 50 to 1000 kPa, and in order to obtain a uniform film, it is preferable to deposit it at a thickness of 100 kPa or more, and considering the efficiency of the subsequent heat treatment step and the cost of the precious metal electrode, It is preferable to form.

Next, the conductive barrier metal layer 106 is formed on the noble metal layer by a conventional chemical vapor deposition method. As the conductive barrier metal layer 106, binary conductive metal nitrides such as TiN, TaN, and WN, and ternary conductive metal nitrides such as TaSiN and TiAlN can be used. In the conductive barrier metal layer 106, a noble metal layer such as Ru, Pt, or the like is exposed to an atmosphere gas by the dielectric film 104 or other semiconductor devices under the capacitor in a subsequent process, for example, a hydrogen atmosphere heat treatment process for improving transistor characteristics. It is formed to prevent deterioration of properties. In addition, the conductive metal barrier layer 106 also plays a role of alleviating the thermal stress that the dielectric film receives in a subsequent heat treatment process together with the polysilicon film formed later. The conductive metal barrier layer 106 is preferably formed to a thickness of 50 to 500 kPa suitable for blocking the permeation of atmospheric gas.

Subsequently, the polysilicon film 107 is formed on the conductive barrier metal layer 106 by a conventional method such as chemical vapor deposition. As described above, the polysilicon film 107 absorbs the thermal stress received by the noble metal layer 105 made of Ru, Pt, or the like in a subsequent heat treatment process after capacitor formation. In addition, since the polysilicon film is formed in the ferry region (not shown), sufficient resistance to form the resistive element of the ferry region can be ensured as compared to the case where only the precious metal layer is formed, and thus the subsequent process can be performed smoothly.

In the present embodiment, a stacked capacitor has been described as an example. However, the upper electrode of the noble metal layer / barrier metal layer / polysilicon film of the present invention is a capacitor having a three-dimensional electrode structure such as another type of semiconductor capacitor, for example, a cylindrical capacitor. Applicable to

According to the present invention, by sequentially forming a triple layer of a noble metal layer, a barrier metal layer, and a polysilicon film as the upper electrode of the dielectric film, the barrier metal layer and the polysilicon film absorb the residual thermal stress generated in the noble metal layer in a subsequent heat treatment process to prevent distortion. In addition, since the polysilicon film can be simultaneously formed in the ferry region at the time of forming the polysilicon upper electrode, sufficient resistance for forming the resistive element of the ferry region can be ensured, thereby ensuring compatibility with the conventional process. .

Claims (3)

Forming a lower electrode connected to a predetermined active region of the substrate on a semiconductor substrate; Forming a dielectric film on the lower electrode; And Forming a precious metal layer on the dielectric film, and sequentially forming a conductive barrier metal layer and a polysilicon film on the precious metal layer to form an upper electrode formed of a triple layer of the precious metal layer / barrier metal layer / polysilicon film. A capacitor forming method of a semiconductor device. The method of claim 1, wherein the noble metal layer is formed to a thickness of 100 to 500 kHz. The method of claim 1, further comprising heat treatment in an oxidizing atmosphere or an inert atmosphere after the forming of the dielectric film or the forming of the noble metal layer.