KR20040059967A - Method for fabricating capacitor in semiconductor device - Google Patents

Abstract

PURPOSE: A method for manufacturing a capacitor of a semiconductor device is provided to prevent reduction of capacitance and degradation of electric properties by restraining the generation of a native oxide layer between a lower electrode and a dielectric film. CONSTITUTION: A lower electrode(26) is formed on a silicon substrate(20) with a contact plug(23). A metal film is formed on the lower electrode. A dielectric film(28) is formed by oxidizing the metal film using anodizing. An upper electrode(29) is then formed on the dielectric film. Al, Hf or Ta is used as the metal film.

Description

Method for fabricating capacitor in semiconductor device

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

As the degree of integration of semiconductor devices, in particular DRAM (Dynamic Random Access Memory) semiconductor memories, increases, the area of memory cells, which are basic units for information storage, is rapidly being reduced.

Such a reduction in the memory cell area is accompanied by a reduction in the area of the cell capacitor, thereby lowering the sensing margin and the sensing speed, and causes a problem that the durability against soft errors caused by α-particles is degraded. Accordingly, there is a need for a method capable of securing sufficient capacitance in a limited cell area.

The capacitance C of the capacitor is defined as in Equation 1 below.

C = ε · As / d

Is the dielectric constant, As is the effective surface area of the electrode, and d is the distance between the electrodes.

Therefore, in order to increase the capacitance of the capacitor, it is necessary to increase the surface area of the electrode, reduce the thickness of the dielectric thin film, or increase the dielectric constant.

Among these, the first method of increasing the surface area of the electrode has been considered. Capacitors of three-dimensional structures, such as concave structures, cylinder structures, multilayer fin structures, and the like, are all proposed to increase the effective surface area of the electrode in a limited layout area. However, this method has a limitation in increasing the effective surface area of the electrode as the semiconductor device is very high integration.

In addition, the method of reducing the thickness of the dielectric thin film in order to minimize the distance between electrodes (d) also faces the limitation due to the problem that the leakage current increases as the thickness of the dielectric thin film is reduced.

Therefore, in recent years, research and development have been focused on securing capacitance of a capacitor mainly by increasing the dielectric constant of a dielectric thin film. Traditionally, so-called NO-nitride (NO) -capacitors using silicon oxide or silicon nitride as the dielectric thin film have become mainstream, but recently, Ta ₂ O ₅ , Al ₂ O ₃ , HfO ₂ , Al ₂ O ₃ / High dielectric materials such as HfO ₂ , Al ₂ O ₃ / Ta ₂ O ₅ , Ta ₂ O ₅ , (Ba, Sr) TiO ₃ (hereinafter referred to as BST), or (Pb, Zr) TiO ₃ (hereinafter referred to as PZT) ), (Pb, La) (Zr, Ti) O ₃ (hereinafter referred to as PLZT), SrBi2Ta2O ₉ (hereinafter referred to as SBT), Bi _4-x La _x Ti ₃ O ₁₂ (hereinafter referred to as BLT) The material is applied as a dielectric thin film material.

In manufacturing a high dielectric capacitor or a ferroelectric capacitor using such a high dielectric material or ferroelectric material as a dielectric thin film material, proper control of dielectric surrounding materials and processes must be accompanied to realize dielectric properties specific to the high dielectric material or ferroelectric material. do.

Generally, noble metals or compounds thereof, such as platinum (Pt), iridium (Ir), ruthenium (Ru), and iridium oxide (RuO ₂ ), are used as the upper and lower electrode materials of the high dielectric capacitor or the ferroelectric capacitor. Or a metal such as ruthenium oxide (IrO ₂ ) is used.

1A and 1B are cross-sectional views illustrating a method of manufacturing a capacitor according to the prior art.

First, as shown in FIG. 1A, the interlayer insulating film 12 is formed on the semiconductor substrate 10 on which the active region 11 is formed, and then penetrates the interlayer insulating film 12 to form an active region ( A contact hole connected to 11) is formed. A contact plug 13 is formed by filling the contact hole with a conductive material. Subsequently, the insulating film 14 for forming a capacitor is formed as large as the capacitor is to be formed. Subsequently, the capacitor forming insulating film 14 is selectively removed to form the capacitor forming hole 15 through which the contact plug 13 is exposed.

Subsequently, as shown in FIG. 1B, the lower electrode 16 is formed of a conductive film in the capacitor forming hole 15.

Next, the dielectric thin film 16 is formed on the lower electrode 16 and the upper electrode (not shown) is formed thereon. Previously, a silicon-based dielectric was used as the dielectric thin film. However, in order to secure a capacitance of more than a predetermined capacity as a semiconductor device becomes high, a high dielectric material such as a Ta ₂ O ₅ film, an Al ₂ O ₃ film, and an HfO ₂ film is used.

In addition, as shown in order to increase the surface area, the lower electrode is formed in a three-dimensional shape, and in order to secure step coverage of the dielectric thin film, such as a Ta ₂ O ₅ film, an Al ₂ O ₃ film, an HfO ₂ film, and the like. A dielectric thin film is formed on the lower electrode 16 by chemical vapor deposition or atomic layer deposition.

However, when forming the dielectric thin film 16 using atomic layer deposition or chemical vapor deposition, a reaction gas containing oxygen such as H ₂ O, O ₂ , O ₃ together with an organic metal source is used as a reactant. Therefore, oxygen penetrates the interface between the lower electrode 17 and the dielectric thin film 16 in the process of forming the dielectric thin film 16.

At this time, the infiltrated oxygen reacts with the material used as the lower electrode in a subsequent thermal process to form an interfacial oxide film (for example, SiO ₂ when the lower electrode is a polysilicon film, TiO _2, etc. when the TiN film is a polysilicon film), and a metal lower electrode In order to prevent the interdiffusion between the contact plug of the silicon film and the silicon film, an oxide film (not shown) formed on the contact plug is oxidized. The formation of the oxide film is caused by an increase in contact resistance and oxidation due to oxidation of the contact plug. Increased instability of the capacitor structure due to the volume change of the thin film, the formation of a series capacitor having a low capacitance lowers the capacitance of the overall capacitor, and increases the deterioration of electrical characteristics such as leakage current characteristics deterioration.

An object of the present invention is to provide a method of manufacturing a capacitor capable of preventing the formation of an oxide film at an interface between an electrode film and a dielectric thin film of a capacitor, thereby preventing a decrease in capacitance and deterioration of electrical characteristics.

1A and 1B are cross-sectional views showing a method of manufacturing a cylindrical capacitor according to the prior art.

2A through 2D are cross-sectional views illustrating a method of manufacturing a semiconductor capacitor in accordance with a preferred embodiment of the present invention.

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

20: substrate

21: active area

22: interlayer insulating film

23: Contact Plug

24: insulating film for capacitor formation

25: hole for capacitor formation

26: lower electrode

27: metal for dielectric thin film

28: dielectric thin film

29: upper electrode

In order to achieve the above object, the present invention comprises the steps of forming a conductive film for the lower electrode on the substrate; Forming a metal for a dielectric thin film on the conductive film; Oxidizing the metal to form a dielectric thin film by anodizing; And forming a top electrode-conductive film on the dielectric thin film.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

Figure 2a to 2d is a view showing a cylindrical capacitor manufacturing method according to a preferred embodiment of the present invention.

First, as shown in FIG. 2A, the interlayer insulating film 22 is formed on the semiconductor substrate 20 on which the active region 21 is formed, and then penetrates the interlayer insulating film 22 to form the active region of the semiconductor substrate 20 ( A contact hole connected to 21 is formed. A contact plug 23 is formed by filling a contact hole with a conductive snow material.

Subsequently, a portion of the upper portion of the contact plug 23 is recessed to form a titanium silicide film (not shown) in the recessed region, and a barrier metal (not shown) is formed thereon. Barrier metal is usually formed by using a titanium nitride film, which is an anti-diffusion film between a material used as a lower electrode and a material used as a contact plug.

Subsequently, an insulating film 24 for forming a capacitor is formed to a height at which the capacitor is to be formed. Subsequently, the capacitor forming insulating film 24 is selectively removed to form the capacitor forming hole 25 through which the contact plug 22 is exposed.

Subsequently, as shown in FIG. 2B, the lower electrode 26 is formed in the capacitor forming hole 25. The lower electrode uses atomic layer deposition or chemical vapor deposition using a conductive silicon, platinum, iridium, ruthenium, iridium oxide, ruthenium oxide, titanium nitride (TiN) and the like to have a thickness of 50 to 500 mm.

Subsequently, the dielectric thin film metal 27 is formed on the lower electrode 26 by using atomic layer deposition or chemical vapor deposition. Al, Hf, Ta, etc. are used as the dielectric thin film 27.

Subsequently, as shown in FIG. 2C, an oxide of Al ₂ O ₃ , HfO ₂ , Ta ₂ O _5, and the like is formed using an anodizing process to form the dielectric thin film 28. In the anodizing process, an aqueous solution including a catalyst and the like is used as the electrolyte while maintaining the wafer temperature at 350 ° C. at a temperature of 0.1 V to 1 MV and a current of 0.1 A to 1 kA. The cathode uses all available metals. For example, when forming an HfO ₂ film, Hf on the wafer is an anode. Pt may be used as the negative electrode and ammonium pentaborate may be used as the electrolyte.

Subsequently, a furnace heat treatment or rapid heat treatment process is performed to improve the crystallization and permittivity of the thin film.

Subsequently, as shown in FIG. 2D, a lower electrode 29 is formed on the dielectric thin film with a conductive film in a range of 50 to 1000 mW.

As described above, according to the present invention, in the formation of the dielectric thin film, the capacitor first deposits a metal used for the dielectric thin film using atomic layer deposition or chemical vapor deposition, and then deposits a wafer in an electrolyte solution (anode; Using an electrochemical rebound as an anode, an oxide film is formed by reacting oxygen in an electrolyte with a metal of an anode to complete a dielectric thin film. In the anodization process, oxygen penetration does not occur when the dielectric thin film is formed, or an oxide film is formed at a low temperature to suppress the formation of an interfacial oxide film between the dielectric thin film and the lower electrode.

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.

According to the present invention, it is possible to manufacture a capacitor having a high capacitance by suppressing an interfacial oxide film between the dielectric thin film of the capacitor and the electrode film, thereby improving the reliability of the semiconductor device.

Claims (5)

Forming a conductive film for the lower electrode on the substrate; Forming a metal for a dielectric thin film on the conductive film; Oxidizing the metal to form a dielectric thin film by anodizing; And Forming an upper electrode conductive film on the dielectric thin film Capacitor manufacturing method of a semiconductor device comprising a. The method of claim 1, The metal is Capacitor manufacturing method of a semiconductor device, characterized in that one selected from Al, Hf or Ta. The method of claim 1, The anodization process The metal is used as an anode, and the wafer temperature is maintained at 350 ° C. at room temperature while the voltage is 0.1V to 1MV, and the current proceeds at 0.1A to 1kA. The method of claim 1, The method of manufacturing a capacitor of a semiconductor device, characterized in that further comprising the step of thermal treatment or rapid heat treatment for crystallization of the dielectric thin film. The method of claim 1, The metal is a capacitor manufacturing method of the semiconductor device, characterized in that formed in the range of 30 ~ 300Å.