KR100324587B1 - Method for forming ferroelectric capacitor capable of preventing degradation of electrode during high temperature annealing - Google Patents

Abstract

The present invention relates to a method of manufacturing a ferroelectric capacitor capable of preventing the deterioration of the characteristics of an electrode due to high temperature heat treatment. The present invention provides a method in which a dielectric film of a capacitor constituting a nonvolatile memory device is grown in an epitaxial or preferred orientation. Size of grain by uniaxially growing a ferroelectric film on a lower electrode made of SrTiO _3-X, LSCO (La-Sr-Cu-O), YBCO (Y-Ba-Cu-O), IrO ₂ , or RuO ₂ And increase the orientation of the domain so that the ferroelectric has a high polarization value and a low constant voltage.

Description

Method for forming ferroelectric capacitor capable of preventing degradation of electrode during high temperature annealing}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a ferroelectric capacitor capable of preventing the deterioration of characteristics of an electrode generated during a high temperature heat treatment process.

Ferroelectric memory devices are a kind of non-volatile memory devices that not only store stored information even when the power supply is cut off, but also operate at a speed comparable to that of conventional dynamic random access memory (DRAM). As the dielectric material of the ferroelectric memory device, SrBi ₂ Ta ₂ O ₉ , Sr _x Bi _2-x (Ta _i Nb _j ) ₂ O ₉ ) or Pb (Zr _x Ti _1-x ) O ₃ thin films are mainly used. In order to obtain the excellent ferroelectric properties of the ferroelectric film as described above, it is necessary to select the upper and lower electrode materials and control the appropriate process.

_{Sr X Bi 2-X (Ta} i Nb j) 2 O 9 minutes of the peak having a capacitor (hereinafter referred to as SBTN) a dielectric is proportional to the grain size. That is, SBTN with large grains has a high polarization value. Therefore, the conventional process flow is performed for a long time furnace heat treatment at a high temperature of 800 ℃ or more after the heat treatment process for nucleation, in order to improve the size of the crystal grains, in this way the surface of the metal electrode in the heat treatment process performed at a high temperature for a long time Due to the generated hillock and thin film stress, short circuits occur due to desorption and the like, thereby deteriorating electrical characteristics.

In addition, as the degree of integration of the FeRAM device increases, a larger polarization value is required, but the overall amount of charge decreases due to the reduction of the capacitor size as the degree of integration increases. Therefore, there is a need for a process of increasing the amount of charge in various ways.

The present invention devised to solve the above problems is to provide a ferroelectric capacitor manufacturing method that can prevent the degradation of the characteristics of the electrode due to high temperature heat treatment.

1 to 6 are cross-sectional views of a nonvolatile memory device capacitor fabrication process.

* Explanation of reference numerals for the main parts of the drawings

18: first oxide electrode 19: SBTN film

20: second oxide electrode

The present invention for achieving the above object is a first step of growing a first oxide electrode to form a lower electrode of the capacitor in an epi-taxial (epi-taxial); Forming a ferroelectric film on the first oxide electrode in the uniaxial direction; And a third step of forming a second oxide electrode forming the upper electrode of the capacitor on the ferroelectric film.

The present invention relates to SrTiO _3-X, LSCO (La-Sr-Cu-O), YBCO (Y-Ba-Cu-), in which a dielectric film of a capacitor constituting a nonvolatile memory device is grown in a uniaxial direction (epi-taxial, preferred orientation). The ferroelectric layer grows uniaxially on a lower electrode made of O), IrO ₂ , or RuO ₂ to increase the grain size and domain orientation so that the ferroelectric has a high polarization value and a low constant voltage. .

The ferroelectric film is formed of an SBTN film, and is referred to as metal organic chemical vapor deposition (MOCVD), plasma enhanced metal organic chemical vapor deposition (PE-MOCVD) for the deposition of ferroelectric films. Various vapor deposition methods such as chemical vapor deposition (chemical vapor deposition, CVD) or sputtering (physical vapor deposition, PVD) are used.

SBTN film grown in the uniaxial direction has a large grain and the polarization orientation is improved to have improved electrical properties such as a large increase in the polarization value of the ferroelectric properties.

Hereinafter, a method of manufacturing a capacitor of a nonvolatile memory device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

First, as shown in FIG. 1, an interlayer insulating film 16 is formed on a semiconductor substrate 10 on which word lines and bit lines are formed, and the interlayer insulating films 16 and 14 are selectively selected. Is etched to form a contact hole exposing a junction (not shown) of the transistor, and a polysilicon film 17 is formed over the entire structure. In FIG. 1, reference numeral 11 denotes an isolation layer. '12' is a gate oxide film. '13' represents a gate electrode and '15' represents a bit line, respectively.

to the next. As shown in FIG. 2, the polysilicon film 17 is planarized by chemical mechanical polishing until the interlayer insulating film 16 is exposed to form a polysilicon plug 17A in the contact hole. do.

Next, as shown in FIG. 3, the first oxide electrode 18, which forms the lower electrode of the capacitor, is grown on the polysilicon plug 17A and the interlayer insulating film 16 in the uniaxial direction.

In this case, the first oxide electrode is formed of SrTiO _3-X having an IrO ₂ , RuO ₂ or perovskite structure, or a superconducting oxide such as YBCO or LSCO is formed by various deposition methods such as CVD and PVD.

When the perovskite and the superconducting oxidation electrode are formed in the uniaxial direction by the CVD method, deposition is performed using plasma energy. At this time, a low power of 50 W to 150 W is applied, and H ₂ O or N ₂ O gas is injected into the reaction source.

In addition, the first oxide electrode 18 is formed in a double layer so that the first oxide electrode layer becomes a site of the second uniaxial growth, and the total thickness of the first oxide electrode 18 is about 2000. Let be.

Next, as shown in FIG. 4, an SBTN (Sr _x Bi _2-x (Ta _i Nb _j ) ₂ O ₉ )) film 19 is uniaxially formed on the first oxide electrode 18 grown in the uniaxial direction. To form. At this time, SBTN is dissolved in a solid organic material of Sr, Bi, Ta, Nb in xylene or octane solvent (solvent) to make a liquid chemical (solution), the solution 2-butanon or n-butylacetate is used as a viscosity and property stabilizer of state chemicals. Subsequently, a rapid thermal process (RTP) for crystal growth of SBTN is performed at a temperature of 700 ° C to 1000 ° C. In this case, in order to increase the size of the grains, the RTP ramp-up rate is 30 ° C./sec to 300 ° C./sec.

When forming the SBTN film 19 by sputtering, considering that Bi has a strong volatility, different targets (multi-targets) are used for each element, and sputtering energy sources are used. It is deposited at room temperature using RF (radio frequency) or RF magnetron (electron) and electron cyclotron resonance (electron resonance) power.

to the next. As shown in FIG. 5, the second oxide electrode 20 constituting the upper electrode of the capacitor is grown on the SBTN film 19 in the same manner as the first oxide electrode 18 to form a metal ferroelectric metal (MFM) structure. Form.

Next, as shown in FIG. 6, the second oxide electrode 20, the SBTN film 19, and the first oxide electrode 18 are selectively etched to form a capacitor, and 800 to prevent a short circuit caused by Bi. Heat treatment is carried out at a temperature of 캜 to oxidize Bi.

Subsequently, the protective oxide film 21 is formed of SiO ₂ or the like, and the protective oxide film 21 is selectively etched to expose the second oxide electrode 20.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

In order to solve the problem of the poor adhesion between the metal electrode and the oxide, the present invention uses the oxide electrode having an excellent adhesion between the oxide film and the oxide, thereby causing peeling due to stress of the laminated film generated during integration. Lifting of the entire film can be prevented, thereby preventing the occurrence of the heel lock of the metal electrode in the high temperature thermal process, thereby suppressing the occurrence of a short circuit.

Claims (5)

In the capacitor manufacturing method, A first step of growing a first oxide electrode forming the lower electrode of the capacitor in an epi-taxial direction; Forming a dielectric film as an SBTN film in the uniaxial direction on the first oxide electrode; And A third step of forming a second oxide electrode forming the upper electrode of the capacitor on the ferroelectric film Capacitor manufacturing method comprising a. The method of claim 1, Each of the first oxide electrode and the second oxide electrode A method for producing a capacitor, characterized in that formed by any one selected from IrO ₂ , RuO ₂ , SrTiO _3-X , LSCO (La-Sr-Cu-O), YBCO (Y-Ba-Cu-O). The method of claim 2, Forming each of the first oxide electrode and the second oxide electrode using SrTiO _3-X , LSCO (La-Sr-Cu-O), or YBCO (Y-Ba-Cu-O) using plasma energy. Capacitor manufacturing method, characterized in that. The method according to any one of claims 1 to 3, And forming the first oxide electrode in a double layer so that the first oxide electrode layer is a site of second uniaxial growth. The method of claim 1, After the third step, A fourth step of selectively etching the second oxide electrode, the ferroelectric layer and the first oxide electrode to form a capacitor pattern; And And a fifth step of heat treating the capacitor pattern.