KR100291181B1 - Method for forming FeRAM - Google Patents

Abstract

PURPOSE: A fabrication method of ferroelectric memory devices is provided to improve a characteristic of a ferroelectric capacitor by keeping a regular residual polarization on a ferroelectric thin film for a comparatively long time. CONSTITUTION: Contact holes are formed by selectively etching the interlayer dielectrics(34,36) formed on a substrate(30). Polysilicon plugs(37) are formed and connected to the substrate(30) through the contact holes. A titanium layer(38), a titanium nitride(39), a platinum layer(40) for forming lower electrodes and a thin film(41) made of PbBi2Ta2O9 are sequentially formed on the entire surface of the resultant structure. Then, the thin film(41), the platinum layer(40), the titanium nitride(39) and the titanium layer(38) are sequentially and partially etched to form a pattern. A protection layer(42) made of SrBi2-xTa2O9-x formed by annealing at the temperature of 500-700 deg.C is formed on the resultant structure to prevent diffusion of hydrogen ions to the thin film(41), thereby keeping a regular residual polarization on the thin film(41) for a comparatively long time. A protection oxide(43) is formed on the protection layer(42). The protection oxide(43) and the protection layer(42) are partially etched to expose the thin film(41). Upper electrodes are formed by the steps of depositing and etching a platinum layer(44).

Description

Ferroelectric memory device manufacturing method {Method for forming FeRAM}

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 memory device.

Ferroelectrics have a large dielectric constant at room temperature and have stable residual polarization characteristics. Applications of the ferroelectrics have been realized by making the ferroelectrics thin and non-volatile memory devices. When using a ferroelectric thin film as a nonvolatile memory device, the signal is input by adjusting the direction of polarization in the direction of an electric field applied to the ferroelectric thin film, and the digital signals 1 and 0 are determined by the direction of residual polarization remaining when the electric field is removed. Is to use the principle of storage.

Hereinafter, a conventional technology will be described with reference to FIG. 1, which is a cross-sectional view of a ferroelectric memory device manufacturing process according to the related art.

As shown in FIG. 1, the interlayer insulating layers 14 and 16 formed on the semiconductor substrate 10 are selectively etched to form contact holes, and the polysilicon plugs 17 connected to the semiconductor substrate 10 through the contact holes. ), Then a titanium film 18 and a titanium nitride film 19 are formed of a barrier metal film, and then a platinum (Pt) film 20 is formed to form a lower electrode, and platinum (Pt) The film 20, the titanium nitride film 19, and the titanium film 18 are selectively etched to form a lower electrode pattern. Subsequently, after the ferroelectric thin film 21 is formed on the lower electrode and selectively etched to form a pattern, the protective oxide films 22 and 23 are formed and selectively etched to expose the ferroelectric thin film 21. Next, the platinum film 24 is formed and selectively etched to form an upper electrode in contact with the exposed ferroelectric film 21. An interlayer insulating film is then formed and planarized. In FIG. 1, reference numeral '11' denotes a field oxide film, '12' denotes a gate oxide layer, '13' denotes a gate electrode, and '15' denotes a bit line.

In the conventional ferroelectric capacitor forming process as described above, hydrogen generated in the process of forming and planarizing the interlayer insulating film is sucked into the surface of the ferroelectric thin film to form H ₂ O to change the composition of the ferroelectric thin film so that the chemical The stoichiometric is not satisfied. Therefore, there is a problem in that the deterioration of the characteristics such as the capacitor does not maintain a constant residual polarization value by applying an electrical pulse (pulse) to the dielectric film.

An object of the present invention to solve the above problems is to provide a method of forming a ferroelectric capacitor that can prevent the hydrogen generated when forming the interlayer insulating film is sucked into the ferroelectric thin film to prevent degradation of the ferroelectric properties.

1 is a cross-sectional view of a ferroelectric memory device manufacturing process according to the prior art;

2A to 2C are cross-sectional views of a ferroelectric memory device fabrication process according to an embodiment of the present invention.

* Description of the main parts of the drawing

30: semiconductor substrate 31: field oxide film

32: gate oxide film 33: gate electrode

34, 36: interlayer insulating film 37: polysilicon plug

38: titanium film 39: titanium nitride film

40, 44: platinum film 41: PbBi ₂ Ta ₂ O ₉ film

42: SrBi _2-x Ta ₂ O _9-x film 43: protective oxide film

The present invention for achieving the above object, the step of forming a capacitor lower electrode on the semiconductor substrate; Forming a PbBi ₂ Ta ₂ O ₉ capacitor ferroelectric film on the lower electrode; Forming a ferroelectric protective film covering the surface and side surfaces of the PbBi ₂ Ta ₂ O ₉ capacitor ferroelectric film which is not in contact with the capacitor upper electrode, wherein the ferroelectric protective film is formed by heat treatment at a temperature of 500 ° C. to 700 ° C .; And forming a capacitor upper electrode in contact with the PbBi ₂ Ta ₂ O ₉ capacitor ferroelectric layer.

The present invention is a method of protecting a ferroelectric film with an SrBi _2-x Ta ₂ O _9-x (x is 0 <x <2) film to prevent hydrogen generated during the interlayer insulating film forming process from being sucked into the ferroelectric film.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 2A to 2C which are cross-sectional views of a ferroelectric memory device manufacturing process according to an embodiment of the present invention.

First, as shown in FIG. 2A, contact holes are formed by selectively etching the interlayer insulating films 34 and 36 formed on the semiconductor substrate 30, a polysilicon film is formed, and then chemical mechanical polishing is performed. After forming the polysilicon plug 37 connected to the semiconductor substrate 30 through the contact hole, the titanium film 38 and the titanium nitride film 39 are formed of the barrier metal film. Next, a platinum (Pt) film 40 is formed to form a lower electrode, and spin coating, organometallic chemical vapor deposition, sputtering, or liquid source (SMDCD) is formed on the semiconductor substrate 10. mixed chemical deposition) method, after forming the PbBi ₂ Ta ₂ O ₉ thin film 41 of 1000 Å to 2000 Å thick, PbBi ₂ Ta ₂ O ₉ thin film 41, platinum (Pt) film 40, a titanium nitride The ride layer 39 and the titanium layer 38 are selectively etched to form a pattern.

Next, as shown in FIG. 2B, in order to prevent hydrogen from penetrating into the PbBi ₂ Ta ₂ O ₉ film 41 in the process of forming and planarizing the interlayer insulating film after the capacitor formation is completed, the semiconductor substrate 30 is formed. PbBi ₂ Ta ₂ O ₉ thin film by sol-gel, organometallic chemical vapor deposition, or LSMCD method to form a SrBi _2-x Ta ₂ O _9-x film 42 to a thickness of 500 1000 to 1000 Å Enclose (41). In forming the SrBi _2-x Ta ₂ O _9-x film, the annealing temperature is set to 500 ° C. to 700 ° C. to prevent volatilization of the PbBi ₂ Ta ₂ O ₉ film. When heat-treated _{2-x Ta 2 O 9-} x film is SrBi at this temperature range is in a state with which the crystallization is not completely amorphous and crystalline SrBi _{2-x Ta 2 O 9-} x film.

Next, as shown in FIG. 2C, a protective oxide film 43 is formed on the SrBi _2-x Ta ₂ O _9-x film 42, and the protective oxide film 43 and the SrBi _2-x Ta ₂ O _{9-are formed. The} film 42 is etched to expose the PbBi ₂ Ta ₂ O ₉ thin film 41. Next, the platinum film 44 is formed and selectively etched to form an upper electrode in contact with the exposed PbBi ₂ Ta ₂ O ₉ thin film 41. 2A to 2B, reference numeral 31 denotes a field oxide film, 32 a gate oxide film, 33 a gate electrode, and 35 a bit line.

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

The present invention made as described above is a method of protecting the ferroelectric film with the SrBi _2-x Ta ₂ O _9-x film to prevent hydrogen generated during the interlayer insulating film forming process from being sucked into the ferroelectric film of the capacitor. It is possible to improve the characteristics of the ferroelectric capacitor by allowing the residual polarization to be maintained for a relatively long time.

Claims (7)

Forming a capacitor lower electrode on the semiconductor substrate; Forming a PbBi ₂ Ta ₂ O ₉ capacitor ferroelectric film on the lower electrode; Forming a ferroelectric protective film covering the surface and side surfaces of the PbBi ₂ Ta ₂ O ₉ capacitor ferroelectric film which is not in contact with the capacitor upper electrode, wherein the ferroelectric protective film is formed by heat treatment at a temperature of 500 ° C. to 700 ° C .; And Forming a capacitor upper electrode in contact with the PbBi ₂ Ta ₂ O ₉ capacitor ferroelectric layer Ferroelectric memory device manufacturing method comprising a. The method of claim 1, The ferroelectric protective film, SrBi _2-x Ta ₂ O _9-x (x is 0 <x <2). The method according to claim 1 or 2, And forming an oxide film on the SrBi _2-x Ta ₂ O _9-x film. The method of claim 1, The capacitor ferroelectric film, A method of manufacturing a ferroelectric memory device formed by spin coating, organometallic chemical vapor deposition, sputtering, or liquid source mixed chemical deposition (LSMCD). The method according to claim 1 or 4, The capacitor ferroelectric film, A method of manufacturing a ferroelectric memory device, which is formed to a thickness of 1000 GPa to 2000 GPa. The method of claim 2, The ferroelectric protective film, A method of manufacturing a ferroelectric memory device which is formed by a sol-gel, an organometallic chemical vapor deposition method, or a liquid source mixed chemical deposition (LSMCD) method. The method of claim 6, The ferroelectric protective film, A ferroelectric memory device manufacturing method to form a thickness of 500 kHz to 1000 kHz.

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