KR100297723B1 - Capacitor of Semiconductor Device Using Ferroelectric Thin Film and Its Manufacturing Method - Google Patents

Abstract

Disclosed are a capacitor of a semiconductor device using a ferroelectric thin film and a method of manufacturing the same. An aspect of the present invention is to provide a lower electrode formed on a semiconductor substrate, an upper electrode formed on a lower electrode, a dielectric film formed of a ferroelectric material at an interface between the lower electrode and the upper electrode, and a sidewall of the dielectric film to block hydrogen supply to the dielectric film. To provide a capacitor of a semiconductor device comprising a protective spacer to protect. Protective spacers are formed as _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, SrRuO ₃ or the like. A lower insulating film is further provided to insulate the spacer from the upper electrode, the dielectric film, and the lower electrode as the lower film of the protective spacer.

Description

Capacitor of Semiconductor Device Using Ferroelectric Thin Film and Its Manufacturing Method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a capacitor of a semiconductor device and a method of manufacturing the same, which prevent deterioration of a ferroelectric thin film caused by hydrogen.

As chip density increases in a semiconductor integrated circuit process, an area that a capacitor can have becomes narrower. Accordingly, there is a demand for an increase in capacitance that a capacitor can have per unit area. Among these methods, a ferroelectric material having a high dielectric constant is used as the dielectric film.

For example, an inter-electrode dielectric film of a capacitor of a dynamic random access memory (DRAM) may be formed of BST (Ba (Sr, Ti) O ₃ ), BaTiO ₃ , SrTiO _3, or PZT (Pb (Zr, Ti) O _3, etc.). In this case, the capacitance of the capacitor is approximately 100 times higher than that of nitride, etc. Furthermore, when PZT or the like is used as a dielectric film, an electric field is applied to the capacitor. Since the data does not disappear even if it is removed, it can be applied to nonvolatile memory.

On the other hand, such ferroelectric materials are formed into thin films at relatively high temperatures of approximately 600 ° C to 700 ° C. Thus, the electrode of a capacitor using a dielectric film made of ferroelectric material is formed of a material that can withstand such high temperature environments and is not easily oxidized. For example, the electrode is formed of platinum (Pt), palladium (Pd) or ruthenium (Ru).

By the way, after forming a capacitor using a dielectric film made of PZT, PLZT ((Pb, La) (Zr, Ti) O ₃ ), PLT ((Pb, La) Ti) O ₃ ) or BST, hydrogen is contained. An interlayer dielectric / intermetal dielctric (ILD / IMD) forming process or passivation using a source gas is performed. This process involves the generation of hydrogen gas.

For example, when the interlayer insulating film is formed of silicon oxide, a source gas containing hydrogen, such as a silane (SiH ₄ ) gas, is used as the silicon source. Such silane gas can generate hydrogen gas by reaction. The hydrogen gas generated as described above is decomposed into hydrogen radicals by reacting with Pt used as the upper electrode. Such decomposed hydrogen radicals may diffuse into the dielectric layer to cause deterioration of characteristics of the dielectric layer. That is, property damage by so-called hydrogen, which deteriorates the property of the dielectric film due to hydrogen invading, may occur.

1 schematically shows a capacitor of a conventional semiconductor device.

Specifically, the capacitor of the conventional semiconductor device includes a lower electrode 30 having the insulating film 20 as a lower film on the semiconductor substrate 10 and an upper electrode 50 formed on the lower electrode 30. The lower electrode 30 and the upper electrode 50 are made of Pt, and a dielectric film 40 made of PZT or the like is provided at an interface between the upper electrode 50 and the lower electrode 30.

The TiO ₂ insulating film 60 is coated on the upper electrode 50. The TiO ₂ insulating film 60 is introduced to suppress an interfacial reaction between a subsequent interlayer insulating film (not shown) and the dielectric film 40 which cover and insulate the upper electrode 50 or the dielectric film 40 and the like. The TiO ₂ insulating layer 60 may partially prevent diffusion of hydrogen or hydrogen radicals as described above, but the TiO ₂ insulating layer 60 may not completely prevent diffusion of hydrogen.

In addition, the sidewall of the dielectric film 40 is only covered with the TiO ₂ insulating film 60. Accordingly, the hydrogen diffusion can easily occur from the sidewall of the dielectric film 40. Further, as the semiconductor device is highly integrated, as the aspect ratio of the pattern increases, the area occupied by the sidewall of the dielectric film 40 is relatively increased. That is, the area fraction of the side surface is increasing. Accordingly, diffusion in the sidewalls of the number can occur very predominantly. As described above, when hydrogen is diffused, the PZT thin film constituting the dielectric film 40 is damaged by hydrogen diffused and its properties are deteriorated.

An object of the present invention is to provide a capacitor of a semiconductor device capable of preventing a dielectric film made of a ferroelectric material from being damaged by hydrogen in a subsequent process and deteriorating its characteristics.

Another object of the present invention is to provide a method of manufacturing a capacitor of a semiconductor device capable of preventing a dielectric film made of a ferroelectric material from being damaged by hydrogen in a subsequent process and deteriorating its characteristics.

1 is a cross-sectional view schematically illustrating a capacitor of a conventional semiconductor device.

2 is a cross-sectional view schematically illustrating a capacitor of a semiconductor device according to an embodiment of the present invention.

3 to 5 are cross-sectional views schematically illustrating a method of manufacturing a capacitor of a semiconductor device according to an embodiment of the present invention.

6 and 7 illustrate the measured coercive electric field (Ec) and coercive electric field-shift (Ec-shift) according to the position on the semiconductor substrate, respectively, to illustrate the effect of the embodiment of the present invention. ) Are graphs schematically showing.

Schematic description of the main reference signs

100; Semiconductor substrate 300; Bottom electrode

400; Dielectric film 500 of ferroelectric material; Upper electrode

600; A lower insulating film 700; Protective spacer

250; Upper insulating film

One aspect of the present invention for achieving the above technical problem is a lower electrode formed on a semiconductor substrate, an upper electrode formed on the lower electrode, a dielectric film formed of a ferroelectric material at the interface between the lower electrode and the upper electrode, and A capacitor of a semiconductor device includes a protective spacer covering a sidewall of the dielectric layer to block and protect a hydrogen supply to the dielectric layer.

The upper electrode is formed of a metal oxide such as IrO ₂ , RuO ₂ , or LaSrCoO. The protective spacers are formed as _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, SrRuO ₃ or the like. A lower insulating layer is further provided to insulate the spacer, the upper electrode, the dielectric layer, and the lower electrode as a lower layer of the protective spacer.

One aspect of the present invention for achieving the above technical problem is to form a lower electrode, a dielectric film of a ferroelectric material and an upper electrode on a semiconductor substrate. A protective spacer is formed to cover the sidewall of the dielectric layer to block and protect the hydrogen supply to the dielectric layer.

The upper electrode is formed of a metal oxide such as IrO ₂ , RuO ₂ , or LaSrCoO. The protective spacers are formed as _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, SrRuO ₃ or the like. A lower insulating layer is further formed to insulate the spacer, the upper electrode, the dielectric layer, and the lower electrode as a lower layer of the protective spacer.

According to the present invention, it is possible to prevent the dielectric film made of the ferroelectric material from being damaged by hydrogen in a subsequent process and deteriorating its properties.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the thickness of the film and the like in the drawings are exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings mean the same elements. Also, when a film is described as being on or in contact with another film or semiconductor substrate, the film may be in direct contact with the other film or semiconductor substrate, or a third film is interposed therebetween. It may be done.

2 schematically shows a capacitor of a semiconductor device according to an embodiment of the present invention.

Specifically, the capacitor of the semiconductor device according to the embodiment of the present invention has a structure of the lower electrode 300 / dielectric film 400 / upper electrode 500 on the semiconductor substrate 100.

The lower electrode 300 is electrically insulated from the semiconductor substrate 100 by the insulating film 200. The lower electrode 300 may be formed of metal or metal oxide. For example, it may be formed of a metal oxide such as iridium oxide (IrO ₂ ), ruthenium oxide (RuO ₂ ), or LSCO (LaSrCoO).

The dielectric film 400 is formed of a ferroelectric material at an interface between the lower electrode 300 and the upper electrode 500. For example, the dielectric layer 400 is formed using ferroelectric or high dielectric materials such as BaTiO ₃ , SrTiO ₃ , PZT, PLZT, PLT, or BST.

The upper electrode 500 is formed of a metal oxide such as IrO ₂ , RuO _2, or LaSrCoO. In this case, the upper electrode 500 may be formed in a double layer structure in which a metal film is formed on the metal oxide thin film after the thin film is formed of the metal oxide. For example, it is preferable to form the upper electrode 500 using a double film in which an Ir thin film is formed on an IrO ₂ thin film.

Using the metal oxide as described above as an electrode material forming the upper electrode 500 may have the following advantages. When Pt is used as the electrode material, Pt causes decomposition of hydrogen molecules, and the decomposed hydrogen reacts with the ferroelectric material of the dielectric film 400 through diffusion to deteriorate its quality. However, when metal oxide is used as the electrode material, such deterioration of properties by hydrogen can be prevented. In addition, as the reading and writing of the data is repeated, electrical characteristics deterioration, that is, fatigue characteristics are excellent, and thus reliability may be secured. For example, it is advantageous to secure reliability of a ferroelectric random access memory (FRAM) device.

The capacitor according to the embodiment of the present invention further includes a protective spacer 700 covering sidewalls of the dielectric layer 400 having the structure of the lower electrode 300, the dielectric layer 400, and the upper electrode 500. The protective spacer 700 may cover the sidewalls of the dielectric layer 400 and may extend to the sidewalls of the upper electrode 500. Then, it extends to cover a part of the lower electrode 300. Accordingly, the dielectric film 400 is completely shielded and protected by the protective spacer 700 and the upper electrode 500 or the lower electrode 300.

Accordingly, the dielectric film 500 may be protected from an interlayer insulating film (not shown), for example, an ILD or an IMD, which covers and protects the capacitor on the upper electrode 500. In more detail, when the interlayer insulating film is formed of an insulating material such as silicon oxide, the dielectric film 500 is protected from hydrogen gas generated from silane gas or the like used as the silicon source.

Furthermore, the protective spacer 700 is formed of a material that can prevent the diffusion or movement of hydrogen. That is, the metal or metal oxide capable of adsorbing hydrogen, for example, IrO _2, RuO _2, LaSrCoO, CaRuO _3, SrRuO ₃ or the protective spacer 700 is formed of a metal oxide, such as. Accordingly, when hydrogen radicals or hydrogen atoms formed by decomposition of the hydrogen gas are diffused through the protective spacer 700, the hydrogen radicals or hydrogen elements are absorbed by the metal oxide forming the protective spacer 700. Or adsorbed.

In more detail, the metal oxide exhibits unusually low bond strength between metal and oxygen. This means that the oxygen can be relatively easily bonded to hydrogen radicals and the like. Therefore, oxygen combined with the metal is easily oxidized (reduction reaction in metal oxide) of hydrogen radicals or hydrogen atoms to be supplied. By such a mechanism, hydrogen radicals or the like penetrated into the protective spacer 700 are trapped and do not diffuse into the dielectric layer 400. That is, the supply of hydrogen radicals or hydrogen atoms to the dielectric film 400 can be suppressed, so that deterioration of ferroelectric materials such as PZT by hydrogen can be prevented.

Further, it is formed the upper electrode 500 formed on top of the dielectric layer 400 in FIG metal oxides such as _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, SrRuO _3, or as described above. Accordingly, the hydrogen radicals passing through the upper electrode 500 may also be prevented from being diffused into the dielectric film 400 by the mechanism as described above. Accordingly, degradation of the ferroelectric material constituting the dielectric film 400 by hydrogen may be prevented.

The protective spacer 700 may be formed of a metal oxide as described above as well as a material capable of preventing the diffusion of hydrogen radicals or hydrogen atoms. However, since the metal oxide as described above effectively prevents the diffusion of hydrogen by the mechanism described above, it is preferable to form the protective spacer 700 with the metal oxide.

Such metal oxides are generally conductive. Since the conductivity is unnecessary for the operation of the capacitor, the metal oxide constituting the protective spacer 700 must be insulated from the upper electrode 500, the dielectric film 400, or the lower electrode 300. To this end, the lower insulating film 600 is further provided as a lower film of the protective spacer 400. The lower insulating layer 600 may be formed of titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon nitride, BST, or the like.

Meanwhile, an upper insulating layer 250 may be further formed on the protective spacer 700. The upper insulating layer 250 may be formed of an insulating material such as TiO ₂ , Al ₂ O ₃ , silicon nitride, or BST. The upper insulating layer 250 serves to protect the protective spacer 700 from the interlayer insulating layer. In more detail, the metal oxide constituting the protective spacer 700 and the silicon oxide constituting the interlayer insulating layer may be prevented from interdiffusion, thereby protecting the protective spacer 700.

A method of manufacturing a capacitor of a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS. 3 to 5.

3 schematically illustrates a step of sequentially forming the lower electrode 300, the dielectric layer 400, and the upper electrode 500 on the semiconductor substrate 100.

Specifically, an insulating film 200 having a contact hole (not shown) for exposing a part of the semiconductor substrate 100 is formed on the semiconductor substrate 100. Thereafter, after forming a conductive contact filling the contact hole, the lower electrode 300 connected to the contact and electrically connected to the semiconductor substrate 100, the dielectric film 400 and the upper electrode formed on the lower electrode 300. 500 and the like are formed through a deposition and patterning process.

The lower electrode 300 may be formed of a metal oxide such as IrO ₂ , RuO _2, or LaSrCoO. The dielectric film 400 may be formed to a predetermined thickness, for example, 2500Å by using ferroelectric or high dielectric materials such as BaTiO ₃ , SrTiO ₃ , PZT, PLZT, PLT, or BST. The dielectric film 400 uses a ferroelectric thin film formed by a sol-gel method, a sputtering method, a Molecular Organic Chemical Vapor Deposition (MOCVD) method, or a pulse laser deposition method. .

The upper electrode 500 may be formed of a metal oxide such as IrO ₂ , RuO _2, or LaSrCoO. The upper electrode 500 may be formed of a double layer of a metal oxide thin film and a metal thin film in consideration of a connection to a later formed wiring, for example, an aluminum (Al) wiring. For example, the upper electrode 500 is formed of a double layer of an IrO ₂ thin film having a predetermined thickness, for example, 300 μs thick, and an Ir thin film having a predetermined thickness, for example, 1700 μs thick. This is to prevent the aluminum oxide (Al ₂ O ₃ ) is formed by the reaction of Al and IrO ₂ to cause the increase of resistance.

4 schematically illustrates a step of forming the lower insulating film 600 protective spacer thin film 701 on the upper electrode 500.

In detail, the lower insulating layer 600 is formed on the upper electrode 500 to cover the sidewall of the upper electrode 500 and the sidewall of the dielectric layer 400 and to cover and shield the lower electrode 400. In this case, the lower insulating layer 600 is formed of an insulating material such as titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon nitride, or BST. Preferably, the TiO ₂ thin film is formed to a thickness of about 1000 GPa and used as the lower insulating film 600.

Then, a lower insulating spacer protective thin film 701 on the (600) to form a metal oxide such as _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, SrRuO _3, or. The metal oxide may be used as an electrode material forming an electrode such as the upper electrode 500. In addition, diffusion of hydrogen radicals or hydrogen atoms into the dielectric film 400 can be prevented. Preferably, the protective spacer thin film 701 is formed of IrO ₂ to a thickness of about 1000 GPa.

5 schematically illustrates a step of patterning the protective spacer thin film 701 to form the protective spacer 700.

Specifically, the entire surface of the protective spacer thin film 701 is etched by an etching method having a directivity. For example, a dry etching method using plasma, a physical etching method such as chemical mechanical polishing, or the like is used. By using the etching method as described above, the protective spacer thin film 701 is entirely etched, so that a portion of the protective spacer thin film 701 is left to cover the sidewall of the dielectric film 400 to form the protective spacer 700.

Alternatively, without forming the protective spacer thin film 701, an additional material pattern is formed to have an open hole exposing a sidewall of the dielectric film 400 or a portion of the lower insulating film 600 covering the sidewall. . Thereafter, after forming a material film filling the open hole, the protective spacer 700 may be formed to cover and cover the sidewalls of the dielectric film 400.

The protective spacer 700 may cover the sidewalls of the dielectric layer 400 and may extend to the sidewalls of the upper electrode 500. Then, it extends to cover a part of the lower electrode 300. Accordingly, the dielectric film 400 is completely shielded and protected by the protective spacer 700 and the upper electrode 500 or the lower electrode 300.

On the other hand, since the protective spacer 700 is formed of a metal oxide having conductivity as described above, the lower insulating film 600 is a metal oxide constituting the protective spacer 700, the upper electrode 500, the dielectric film 400 or the lower electrode. It serves to insulate from 300. In addition, the lower insulating film 600 also has an additional function of preventing interdiffusion between the interlayer insulating film formed later, for example, the silicon oxide film used as the ILD or the IMD and the dielectric film 400.

After the protective spacer 700 is formed in this manner, an interlayer insulating film covering the entire resultant is formed. In this case, an upper insulating layer 250 is formed as an insulating material such as TiO ₂ , Al ₂ O ₃ , silicon nitride, BST, or the like as the lower layer of the interlayer insulating layer. Preferably, the TiO ₂ thin film is formed to a thickness of about 500 GPa. The upper insulating layer 250 serves to protect the protective spacer 700 from the interlayer insulating layer.

6 and 7 illustrate coercive electric field (Ec) and coercive electric field-shift (Ec-shift) according to positions on a semiconductor substrate, respectively, to illustrate the effect of the embodiment of the present invention. The graphs are shown schematically.

Specifically, the specimen was produced as follows. The TiO ₂ thin film was formed to a thickness of about 1000 mW and a spacer was formed on the resultant on which the upper electrode of the lower electrode / PZT dielectric film / IrO ₂ -Ir thin film was formed. The spacer is formed to form an IrO ₂ thin film on the lower insulating film having a thickness of about 1000 mW and then etch the entire surface to remain at about 300 mW to surround the PZT dielectric layer. Subsequently, the upper insulating film covering the spacer was formed to a thickness of about 500 kPa of TiO ₂ thin film. A comparative specimen in which only a TiO ₂ thin film was formed to a thickness of 1500 않고 without spacers was prepared together with the specimen according to the embodiment of the present invention prepared as described above.

Electric field-remnant polarization (E-Pr) characteristics of the specimens were measured and shown in FIGS. 6 and 7. In particular, these specimens set the region where the pattern was formed in a long line shape next to a rectangular pad among the various patterns formed on the semiconductor substrate. Since these areas are areas where the sidewall occupies a large area, the effect of the spacer introduction according to the present invention can be clearly seen.

In FIG. 6 and FIG. 7, the center is shown as C, the top as T, the bottom as B, the left as L, and the right as R, depending on the location of the specimens on the semiconductor substrate. In addition, the specimen incorporating the spacer according to the embodiment of the present invention is the case of the reference numerals 820 and 840 of FIG. 6 and the reference numerals 920 and 940 of FIG. 7. 840 and 940 are the results under a voltage of 3V. In addition, the comparison specimen without introducing the spacer is the case of the reference numerals 810 and 830 of FIG. 6 and the reference numerals 910 and 930 of FIG. 7, and the reference numerals 810 and 910 are the results under a voltage of 3V, The result is under a voltage of 5V.

The specimens with or without spacers all exhibited Pr values of approximately 12-13 μC / cm 2. However, as shown in FIG. 6, when the spacers are not introduced (810, 830), the average Ec is higher than that when the spacers are introduced (820, 840). As shown in FIG. 7, when the spacers are not introduced (910, 930), the center voltage transfer degree is higher in the + direction on average than in the case where the spacers are introduced (920, 940). . This result indicates that the spacer prevented deterioration of the dielectric film such as PZT thin film by hydrogen, thereby suppressing property damage.

According to the present invention described above, by forming a spacer that shields and protects the side wall of the dielectric film, it is possible to prevent deterioration by hydrogen of the ferroelectric dielectric film. By forming the spacer from a metal oxide or the like used as the electrode material, the deterioration of the hydrogen characteristic of the ferroelectric dielectric film can be prevented by the property of suppressing the diffusion of hydrogen radicals or hydrogen atoms of the metal oxide.

Claims (6)

A lower electrode formed on the semiconductor substrate; An upper electrode formed on the lower electrode; A dielectric film formed of a ferroelectric material at an interface between the lower electrode and the upper electrode; A protective spacer covering a sidewall of the dielectric layer to block hydrogen supply to the dielectric layer; And And a lower insulating film which insulates each of the upper electrode, the dielectric film, and the lower electrode from the protective spacer at an interface between the protective spacer and the dielectric film. The capacitor of claim 1, wherein the upper electrode is formed of any one metal oxide selected from the group consisting of IrO ₂ , RuO ₂ , and LaSrCoO. The method of claim 1, wherein said protective spacer capacitor of a semiconductor device being formed by any one selected from the group consisting of _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, and SrRuO _3. Forming a lower electrode, a dielectric film of ferroelectric material and an upper electrode on the semiconductor substrate; Forming a lower insulating layer covering and insulating the lower electrode, the dielectric layer, and the upper electrode; And Forming a protective spacer covering the lower insulating film on the sidewall of the dielectric film to block and protect the hydrogen supply to the dielectric film. The method of claim 4, wherein the upper electrode is formed of any one metal oxide selected from the group consisting of IrO ₂ , RuO ₂ , and LaSrCoO. The method of claim 4, wherein the protective spacer _{IrO 2, RuO 2, LaSrCoO,} CaRuO 3, and the capacitor manufacturing method of a semiconductor device characterized in that the SrRuO ₃ with any one form selected from the group consisting of.