KR20000042448A - Method for fabricating ferroelectric capacitor of non volatile memory device - Google Patents

Abstract

PURPOSE: A ferroelectric capacitor fabricating method is provided to prevent a titanium film from being diffused from a titanium adhesive film to a ferroelectric film. CONSTITUTION: In a ferroelectric capacitor fabricating method, interlayer insulation layers(14,16) are formed over an entire surface of a substrate(10) on which a word line and a bit line(15) are formed. A contact hole is formed in the interlayer insulation layers(14,16) so as to expose a junction of a transistor. A polysilicon film(17) is formed over the entire surface of the substrate(10), and then is polished so as to form a contact plug. A titanium film(18) is formed on a resultant structure, and a platinum film(19) is formed on the titanium film(18). An NbxOy film(20) is formed on the platinum film(19) by use of one of CVD, PVD and a spin on process.

Description

Method for manufacturing ferroelectric capacitor of nonvolatile memory device

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 capacitor of a nonvolatile memory device capable of effectively preventing Ti from diffusing from a Ti adhesive film into a ferroelectric film.

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). Dielectric materials of ferroelectric memory devices include SrBi ₂ Ta ₂ O ₉ , (Sr _x Bi _2-y (Ta _i Nb _j ) ₂ O _9-z ) (hereinafter SBTN), and Pb (Zr _x Ti _1-x ) O _Three thin films are mainly used. In order to obtain excellent ferroelectric properties of the ferroelectric film as described above, selection of upper and lower electrode materials and control of an appropriate process are essential.

In the ferroelectric memory device manufacturing process, when a ferroelectric film such as SBTN (Sr _x Bi _2-y (Ta _i Nb _j ) ₂ O _9-z ) is formed as a dielectric film, a Pt / Ti structure is mainly used as a lower electrode of the capacitor. Among them, Ti serves as an adhesive film to improve the adhesion between the polysilicon film and the Pt film. Ti, which has a fast diffusion rate, diffuses into the ferroelectric film through the Pt grain boundary during the SBTN film heat treatment process and then diffuses into the TiO. Form _x oxide. The TiO _x oxide formed inside the thin film prevents dipole polling of the SBTN film due to the application of an external voltage, resulting in deterioration of the polarization value, which is a ferroelectric property, and polarization fatigue, which is the biggest problem for nonvolatile memory devices. There is a problem to increase.

The present invention devised to solve the above problems is to provide a method of manufacturing a capacitor of a nonvolatile memory device that can effectively prevent the diffusion of Ti from the Ti adhesive film to the ferroelectric film.

1 to 5 are cross-sectional views of a nonvolatile memory device fabrication process in accordance with one embodiment of the present invention.

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

17: polysilicon film 18: Ti film

19: Pt film 20: Nb _x O _y film

21: SBTN film

The present invention for achieving the above object is a first step of forming a polysilicon plug (plug) connected to the semiconductor substrate through the insulating film formed on the semiconductor substrate; A second step of forming a Ti film and a first conductive film on the entire structure in which the first step is completed; Forming a niobium oxide (Nb _x O _y ) film on the first conductive film; And a fourth step of forming a ferroelectric film and a second conductive film on the niobium oxide film.

The present invention forms a Nb _x O _y film at the interface between the BSTN film and the lower electrode of the nonvolatile memory device capacitor and effectively prevents Ti from diffusing into the BSTN film through the grain boundary of the Pt film. Its characteristics are to improve.

As a Nb _x O _y film forming method, a method is formed by chemical vapor deposition (CVD) using an organic material of Nb metal to form a film with high temperature thermal energy of 500 ° C. or higher, and formed at low temperature using plasma activation energy. Method, physical vapor deposition (PVD) or spin-on method is used.

A nonvolatile memory device manufacturing method according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

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. Etching to form a contact hole for exposing a junction (not shown) of the transistor, and to form a polysilicon film 17 on 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, thereby plugging the polysilicon film 17 into the contact hole. To form.

Subsequently, a Ti film 18 is formed on the entire structure in order to prevent silicide from forming by interfacial reaction between the polysilicon film 17 and the Pt film and to improve adhesion to prevent lifting of the film. The Pt film 19 is formed on the Ti film 18.

Next, as shown in FIG. 3, the Nb _x O _y film 20 is formed on the structure where the Pt / Ti lower electrode is formed by various methods. At this time, the Nb _x O _y film 20 is formed by CVD, PVD or spin on method. Each formation method is as follows.

When the Nb _x O _y film 20 is formed by the CVD method, liquid Nb organic material is sprayed and deposited into the reaction chamber. Plasma activation energy is also used to enable low temperature deposition by CVD method, wherein reaction gas uses N ₂ O in addition to O ₂ , and relatively low RF power is applied as a PLASMA activation energy source and deposition energy is 50 W to Let 120W.

When using the PVD method, an Nb film is deposited on the Pt film 19 and subjected to an oxidation process to form an Nb _x O _y film 20. At this time, in order to prevent diffusion and oxidation of Ti and to oxidize Nb effectively, the oxidation process is carried out by a rapid thermal process (RTP) in a vacuum state, and the ramp-up rate of the RTP is 100 ° C / sec or more. The reaction gas is rapidly oxidized at high temperature using N ₂ O. In addition, the RTP temperature is performed in the range of 600 ° C to 750 ° C to allow decomposition of N ₂ O and recrystallization of Pt.

When applying the Nb _x O _y film 20 by the spin-on method, the Nb organic source is xylene, octace or Iso-propel alcohol (IPA) and MEK (non-hazardous to humans). It is dissolved in a primary solvent such as 2-butanon to form a primary solution, and a secondary solvent is used to form a metal organic deposition (MOD) chemical which is stable to moisture. The film is coated using 2-ethylhexanic acid. On the other hand, when the Nb _x O _y film 20 is formed by the spin-on method, chemicals are applied to the end surfaces of the wafer edges, thereby causing contaminating particles and peeling during subsequent processes. It causes. Therefore, EBR (edge bead removing) is performed using a chemical such as MEK (2-butanon). After applying the Nb _x O _y film 20, the first bake was performed at 120 ° C to 200 ° C and the second bake at 220 ° C to 300 ° C to cure the film. do. Subsequently, a furnace heat treatment is performed to obtain fine grains.

Next, as shown in FIG. 4, ferroelectric films such as SBTN ((Sr _x Bi _2-y (Ta _i Nb _j ) ₂ O _9-z )) film 21 and the like are placed on the Nb _x O _y film 20. Deposition is carried out in various ways, and annealing processes are carried out for perovskite nucleation and grain growth.

Next, as shown in FIG. 5, the upper electrode 22 is formed on the SBTN film 21, and the SBTN film 21, the Nb _x O _y film 20, the Pt film 19, and the Ti film ( 18) is selectively etched to form a capacitor structure, a protective oxide film 23 is formed of SiO _2, etc., and the protective oxide film 23 is selectively etched to expose the upper electrode 22.

Next, a metal wiring forming step or the like is performed.

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.

According to the present invention as described above, by forming an Nb _x O _y film between a ferroelectric film such as an SBTN film and a lower Pt electrode, Ti is effectively prevented from being diffused into the ferroelectric film, thereby improving ferroelectric properties and thus characteristics of a nonvolatile memory device. Can improve.

Claims (10)

In the capacitor manufacturing method of a nonvolatile memory device, A first step of forming a polysilicon plug connected to the semiconductor substrate through an insulating film formed on the semiconductor substrate; A second step of forming a Ti film and a first conductive film on the entire structure in which the first step is completed; Forming a niobium oxide (Nb _x O _y ) film on the first conductive film; And A fourth step of forming a ferroelectric film and a second conductive film on the niobium oxide film Capacitor manufacturing method of a nonvolatile memory device, including The method of claim 1, The first conductive film is formed of a Pt film, A method of manufacturing a capacitor of a nonvolatile memory device, wherein the ferroelectric film is formed of a (Sr _x Bi _2-y (Ta _i Nb _j ) ₂ O _9-z ) film, The method according to claim 1 or 2, In the third step, The method of manufacturing a capacitor of a nonvolatile memory device, characterized in that the niobium oxide film is formed by chemical vapor deposition by injecting a liquid Nb organic material in the reaction chamber (chamber). The method of claim 3, wherein And forming the niobium oxide film by chemical vapor deposition using plasma activation energy. The method of claim 4, wherein A method of manufacturing a capacitor of a nonvolatile memory device, characterized in that the niobium oxide film is formed using O ₂ and N ₂ O as reaction gas. The method of claim 3, wherein And forming said niobium oxide film at a temperature not lower than 500 [deg.] C. The method according to claim 1 or 2, The third step, Forming an Nb film on the first conductive film by physical vapor deposition; And And oxidizing the Nb film by a rapid thermal process in a vacuum state to form the niobium oxide film. The method of claim 7, wherein The rapid heat treatment, Manufacture of a capacitor of a nonvolatile memory device, wherein N ₂ O is used as the reaction gas, and the ramp-up rate of the RTP is not lower than 100 ° C./sec in the range of 600 ° C. to 750 ° C. Way. The method of claim 3, wherein In the third step, And forming the niobium oxide film by a spin-on method. The method of claim 9, The third step, Dissolving the Nb organic source with xylene, octace or primary solvent of Iso-Propyl Alcohol (IPA) and 2-butanon (MEK); Coating the membrane with 2-ehxylhexanic acid as a secondary solvent; Performing a primary bake at a temperature of 120 ° C. to 200 ° C .; Performing a secondary bake at a temperature of 220 ° C. to 300 ° C .; And A method of manufacturing a capacitor of a nonvolatile memory device comprising the step of performing a furnace heat treatment.