JP4957720B2 - Manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to a method of manufacturing a semiconductor equipment having a ferroelectric capacitor.

  Flash memories and ferroelectric memories (FRAM: Ferroelectric Random Access Memory, registered trademark of Ramtron International Corporation, USA) are known as nonvolatile memories that can store information even when the power is turned off.

  A flash memory has a floating gate embedded in a gate insulating film of an insulated gate field effect transistor (IGFET), and stores information by accumulating charges representing stored information in the floating gate. For writing and erasing information, a tunnel current passing through the insulating film needs to flow, and a relatively high voltage is required.

  On the other hand, the FRAM stores information using the hysteresis characteristic of a ferroelectric substance. A ferroelectric capacitor having a ferroelectric film as a capacitor dielectric between a pair of electrodes generates polarization according to the applied voltage between the electrodes, and has spontaneous polarization even when the applied voltage is removed. If the polarity of the applied voltage is reversed, the polarity of the spontaneous polarization is also reversed. Information can be read by detecting this spontaneous polarization. The FRAM operates at a lower voltage than the flash memory, and can perform high-speed writing with power saving.

  FIG. 13 is a circuit diagram of a 2T / 2C type memory cell of FRAM. FIG. 13 shows a 2T / 2C type memory cell using two transistors Ta and Tb and two capacitors Ca and Cb for storing 1-bit information. In such a 2T / 2C type memory cell, a complementary operation is performed in which “1” or “0” information is stored in one capacitor Ca and the opposite information is stored in the other capacitor Cb. . In addition, the 2T / 2C type memory cell has a structure that is strong against process variations, but the cell area is about twice that of the 1T / 1C type memory cell described below.

  FIG. 14 is a circuit diagram of a 1T / 1C type memory cell of FRAM. FIG. 14 shows a 1T / 1C type memory cell that can use one transistor T1 and one capacitor C1 or one transistor T2 and another capacitor C2 for storing 1-bit information. The configuration is the same as DRAM. Such a 1T / 1C type memory cell has a small cell area and can be highly integrated. However, a reference voltage is required to determine whether the charge read from the memory cell is “1” information or “0” information. Since the reference cell that generates the reference voltage reverses the polarization every time it is read, it deteriorates faster than the memory cell due to fatigue. Further, the 1T / 1C type memory cell has a narrower determination margin than the 2T / 2C type memory cell, and is vulnerable to process variations.

13 and 14 include PZT materials such as PZT (Pb (Zr, Ti) O ₃ ) and La-doped PZT (PLZT), which are ferroelectric films, and SBT (SrBi ₂ Ta ₂ O ₉ ). Bi layered structure compounds such as SBTN (SrBi ₂ (Ta, Nb) ₂ O ₉ ) are used. These ferroelectric films are easily reduced by hydrogen, and in order to ensure the quality as an FRAM, it is necessary to carry out recovery annealing in an oxidizing atmosphere at 500 ° C. to 700 ° C. after the formation of the ferroelectric film. is there. This is because the process after the formation of the ferroelectric capacitor includes a step of generating hydrogen, such as growth of an interlayer insulating film.

  In the next generation FRAM, for example, 0.18 μm generation FRAM, a 1T / 1C type circuit capable of high integration is used, and a stack capacitor structure (a ferroelectric capacitor and a transistor portion are plugged in order to further increase the degree of integration. There is a tendency to employ a structure in which electrodes are directly connected.

  Generally, tungsten (W) is used for the plug electrode in the stack capacitor structure. This is because tungsten has lower resistance and heat resistance than doped silicon. However, when tungsten is oxidized, it becomes a very high-resistance oxide. Therefore, even if a part of the tungsten is oxidized, the resistance becomes high and it is difficult to secure a contact.

On the other hand, a noble metal such as platinum (Pt) or iridium (Ir) is used for the lower electrode of the ferroelectric capacitor in order to avoid oxidative deterioration due to the recovery annealing in the oxidizing atmosphere described above. In addition, a conductive noble metal oxide that can maintain conductivity even when oxidized, such as IrO ₂ , SrRuO ₃ , La _0.5 Sr _0.5 CoO _3, or the like is also used.

  However, these lower electrodes cannot suppress the diffusion of oxygen (O) at a temperature around 600 ° C. Therefore, when recovery annealing is performed at such a high temperature, the tungsten plug electrode in the stack capacitor structure is oxidized through the lower electrode.

  In order to prevent such oxidation, it has been proposed to provide an oxygen barrier layer between the lower electrode and the plug electrode (see, for example, Patent Document 1). In this proposal, it has been reported that a titanium aluminum nitride (TiAlN) film that becomes an oxygen barrier layer is inserted between a titanium nitride (TiN) film that is a part of the plug electrode and the lower electrode. If such an oxygen barrier layer is provided, oxidation of the plug electrode can be prevented. This is because the oxidation rate of titanium aluminum nitride is two orders of magnitude slower than that of titanium nitride. In addition, aluminum nitride (AlN) itself exhibits insulating properties, but a cationic impurity such as titanium (Ti) is added or an aluminum nitride film in which nitrogen (N) is insufficient is formed. Then, since conductivity is exhibited, contact failure due to the provision of the oxygen barrier layer does not cause a problem.

  By the way, as a formation method of the ferroelectric film, a sputtering method, a sol-gel method, and a MOCVD (Metal Organic Chemical Vapor Deposition) method are currently known. When a ferroelectric film, for example, a PZT film is formed by sputtering, platinum is used as a material for the lower electrode serving as the base. This is because, in order to increase the spontaneous polarization of the crystal of the PZT film, it is necessary that the underlying lower electrode is strongly oriented to the (111) plane, but platinum is strongly oriented to the (111) plane. This is because it is suitable as a base for the PZT film.

  However, since the PZT film formed by sputtering has poor crystallinity when formed at a high temperature, it is crystallized by forming an amorphous film at a low temperature and then performing rapid thermal annealing (RTA; Rapid Thermal Annealing) in an oxygen atmosphere. There is a need. Since crystallization by RTA treatment requires a high temperature of 700 ° C. or higher, there is a possibility that the tungsten plug electrode may be oxidized even if an oxygen barrier layer such as titanium aluminum nitride is used in the stacked capacitor structure.

  On the other hand, if the PZT film is formed by the MOCVD method, the PZT film is grown while maintaining good crystallinity on the lower electrode during the growth process. Can be expected.

  However, when the PZT film is formed by the MOCVD method, platinum is not suitable as a constituent material of the lower electrode. This is because lead (Pb) in the PZT film reacts with platinum to form PtPbx, which causes roughness at the interface between the lower electrode and the PZT film and degrades the film quality. Therefore, when the PZT film is formed by the MOCVD method, a material other than platinum must be selected as the lower electrode.

  Therefore, when a ferroelectric film is formed by the MOCVD method, it is necessary to employ a noble metal other than platinum or a conductive noble metal oxide as the lower electrode. Among these materials, when an oxide conductive material such as iridium oxide (IrOx) is used as the lower electrode, the oxide conductive material is reduced when the PZT film is formed by the MOCVD method, which is difficult to employ. Therefore, a noble metal such as iridium is adopted as the material for the lower electrode.

  Even when iridium or the like is used for the material of the lower electrode as described above, the contact property of the tungsten plug electrode is maintained even if recovery annealing is performed at 700 ° C. by using a titanium aluminum nitride film as an oxygen barrier layer. Is done. Therefore, the insertion of the titanium aluminum nitride film is advantageous in terms of oxidation resistance of the tungsten plug electrode.

  However, the crystallinity of the iridium film formed on the titanium aluminum nitride film is not good. This is because the crystallinity of the titanium aluminum nitride film inserted as an oxygen barrier layer is not good, and the crystallinity of the iridium film formed on the titanium aluminum nitride film is also deteriorated due to this. . Therefore, when this iridium film is used as the lower electrode, the crystallinity of the ferroelectric film formed thereon is also dragged and deteriorates.

In order to improve the crystallinity of the titanium aluminum nitride film, the surface of the interlayer insulating film including the tungsten plug electrode, for example, the silicon oxide film is modified by plasma treatment with ammonia (NH ₃ ) gas. There has been proposed a method for improving the crystallinity of a titanium nitride film as a base of a titanium aluminum nitride film (see, for example, Patent Document 2). In this proposal, after a titanium film is formed on a silicon oxide film, the titanium film is nitrided to form a titanium nitride film.

  Oxygen atoms are exposed on the surface of the silicon oxide film not subjected to plasma treatment. When a titanium film is formed on such a silicon oxide film, oxygen and titanium are easily bonded to each other, so that titanium migration hardly occurs on the surface of the silicon oxide film. Therefore, a titanium film with good crystallinity cannot be obtained, and the crystallinity of the titanium nitride film obtained by nitriding the titanium film also deteriorates. Accordingly, the crystallinity of the titanium aluminum nitride film formed thereon is also deteriorated.

  On the other hand, when plasma treatment with ammonia gas is performed on the surface of the silicon oxide film, oxygen on the surface of the silicon oxide film is terminated with N—H groups. When a titanium film is formed on such a silicon oxide film, the bond between titanium and oxygen is suppressed, and migration of titanium is promoted. Since titanium has a self-orientation property, a titanium film with good crystallinity is formed by promoting migration. If the crystallinity of the titanium film is good, the titanium nitride film obtained by nitriding the titanium film also becomes good, and the crystallinity of the titanium aluminum nitride film formed thereon can be obtained with good crystallinity.

As described above, when the plasma treatment with ammonia gas is applied to the interlayer insulating film, the crystallinity of the film laminated on the interlayer insulating film is improved in a chain manner, and finally the crystallinity of the ferroelectric film can be improved. .
JP-A-8-64786 JP 2004-153031 A

  However, in the next generation FRAM, for example, the 0.18 μm generation FRAM, in order to increase the degree of integration, a stack capacitor structure in which a ferroelectric capacitor is directly connected on the plug electrode is adopted. For this reason, the capacitor area with respect to the plug electrode is reduced.

  When the capacitor area with respect to the plug electrode is reduced, the crystallinity of the ferroelectric film is easily affected by the crystallinity of the lower electrode immediately above the plug electrode when the ferroelectric film is formed on the lower electrode. . Therefore, in order to obtain an FRAM having sufficient capacitor characteristics, it is necessary to improve the crystallinity of the lower electrode immediately above the plug electrode before forming the ferroelectric capacitor portion.

  However, although the above-described plasma treatment with ammonia gas has the effect of improving the crystallinity of the lower electrode on the silicon oxide film having oxygen atoms on the surface, for example, the crystallinity of the lower electrode on the tungsten plug electrode is sufficient. It is difficult to improve. This is because there is no oxygen in tungsten, so even if a plasma treatment with ammonia gas is performed, the tungsten surface is difficult to be terminated with nitrogen and hydrogen. As a result, even if the surface of the tungsten plug electrode is subjected to plasma treatment with ammonia gas, migration of titanium atoms hardly occurs on the tungsten plug electrode, and it is possible to form a titanium film with good crystallinity on the tungsten plug electrode. difficult.

  When the crystallinity of titanium on the tungsten plug electrode is deteriorated, the crystallinity of the titanium nitride film obtained by nitriding titanium is also inferior, and the crystallinity of the titanium aluminum nitride film is also inferior. Therefore, the crystallinity of the iridium film formed on the titanium aluminum nitride film is also dragged and deteriorated. When the crystallinity of the iridium film is deteriorated, the crystallinity of the ferroelectric film on the iridium film is also deteriorated due to this, and finally, there is a problem that the device performance as the FRAM cannot be sufficiently obtained.

The present invention has been made in view of these points, is connected to good between plug electrode and the ferroelectric capacitor, and a method of manufacturing a semiconductor equipment having excellent crystallinity ferroelectric capacitor The purpose is to provide.

According to one aspect of the present invention, in a semiconductor device having a ferroelectric capacitor, the lower electrode of the ferroelectric capacitor is electrically connected via a plug electrode connected to the element, the aluminum oxide film .

  According to this semiconductor device, the lower electrode and the plug electrode are connected via the aluminum oxide film. In that case, if the aluminum oxide film is, for example, a film having a lot of oxygen vacancies and an extremely thin film, conduction between the plug electrode and the ferroelectric capacitor is ensured.

According to one aspect of the present invention, a step of forming a plug electrode connected to an element formed on the semiconductor substrate in an insulating film on the semiconductor substrate, and an oxygen vacancy inside the plug electrode A step of forming an aluminum oxide film having a thickness of 1 nm to 5 nm, a step of performing a plasma treatment using a gas containing nitrogen and hydrogen on the aluminum oxide film, and a titanium film on the aluminum oxide film after the plasma treatment. Forming a film, nitriding the titanium film to form a titanium nitride film, forming a titanium aluminum nitride film on the titanium nitride film, and forming a strong film on the titanium aluminum nitride film. There is provided a method of manufacturing a semiconductor device including a step of forming an iridium film as a lower electrode of a dielectric capacitor .

According to this manufacturing method, the aluminum oxide film is formed on the plug electrode, and the aluminum oxide film improves the crystallinity of the titanium nitride film formed thereon. This becomes an orientation improving layer, which improves the crystallinity of the titanium aluminum nitride film formed on the upper layer, and further improves the crystallinity of the iridium film formed as the lower electrode on the upper layer. In addition, since there is a titanium aluminum nitride film between the plug electrode and the lower electrode, oxidation of the plug electrode is prevented at the same time.

According to the disclosed technique, it is possible to connect the plug electrode and the ferroelectric capacitor satisfactorily, and to form a ferroelectric capacitor with good crystallinity. Therefore, a high-performance and highly reliable semiconductor device having a ferroelectric capacitor can be realized.

  These and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments by way of example of the present invention.

It is principal part sectional drawing of the formation process of a MOS transistor and a plug electrode. It is principal part sectional drawing of the formation process of an aluminum oxide film. It is principal part sectional drawing of the formation process of a titanium film. It is principal part sectional drawing of the formation process of a titanium nitride film. It is principal part sectional drawing of the lamination process of a film | membrane. It is principal part sectional drawing of the formation process of a ferroelectric capacitor. It is principal part sectional drawing of the formation process of an aluminum oxide protective film. It is principal part sectional drawing of the formation process of a 2nd interlayer insulation film. It is principal part sectional drawing of the formation process of a plug electrode. It is principal part sectional drawing of the formation process of a plug electrode. It is a rocking curve result of X-ray diffraction of sample A. It is a rocking curve result of X-ray diffraction of sample B. It is a circuit diagram of a 2T / 2C type memory cell of FRAM. It is a circuit diagram of a 1T / 1C type memory cell of FRAM.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 10 are schematic cross-sectional views of the relevant part showing the manufacturing process of a semiconductor device provided with a ferroelectric capacitor. Hereinafter, each manufacturing process will be described in order.

  FIG. 1 is a cross-sectional view of an essential part of a MOS transistor and plug electrode forming process. First, the MOS transistor 20 is formed on the well region 12 defined by the element isolation region 11 in the substrate 10 by a known method. Next, a cover insulating film (for example, SiON film) 21 that protects the MOS transistor 20 is formed. Next, a first interlayer insulating film 22 is formed, and a plug electrode 30 is formed in the contact hole 24 reaching the impurity diffusion region 23 of the MOS transistor 20.

  The plug electrode 30 is formed, for example, by previously forming a glue film 30a composed of titanium nitride (50 nm) / titanium (30 nm) on the inner wall of the contact hole 24 opened in the first interlayer insulating film 22 by a sputtering method. . Further, after the tungsten is formed by the CVD method, it is planarized by a chemical mechanical polishing (CMP) method to form the tungsten layer 30 b in the contact hole 24.

  FIG. 2 is a fragmentary cross-sectional view of the aluminum oxide film forming step. An aluminum oxide film 40 is formed on the first interlayer insulating film 22, the glue film 30a, and the tungsten layer 30b by RF sputtering in an atmosphere of only an inert gas, for example, argon (Ar). The film thickness is formed to be 2 nm, for example. Here, aluminum oxide is used as a target material for RF sputtering.

  The aluminum oxide film 40 is formed by RF sputtering only in an argon atmosphere. By using such a method, the aluminum oxide film 40 has an aluminum (Al) composition that increases in stoichiometry. Furthermore, the film thickness is as extremely thin as 2 nm. By forming the aluminum oxide film 40 having a large number of oxygen vacancies and on the plug electrode 30 in this way, conductivity is exhibited. Therefore, contact between the aluminum oxide film 40 and the plug electrode 30 does not occur. As will be described later, the aluminum oxide film 40 becomes an alignment reset layer that easily causes migration of titanium atoms when forming a titanium film that becomes a seed layer of the titanium nitride film by modifying the surface.

Subsequently, plasma treatment with ammonia gas is performed on the surface of the aluminum oxide film 40 to modify the surface of the aluminum oxide film 40. That is, by this plasma treatment, the surface of the aluminum oxide film 40 is terminated with an N—H group. The plasma treatment conditions using ammonia gas at this time are, for example, a substrate temperature of 400 ° C., an ammonia gas supply amount of 525 sccm (standard cc / min, 1.013 × 10 ⁵ Pa, 0 ° C.), and a pressure of 1 Torr (133.3 Pa). The RF power is 400 W and the processing time is 3 min.

  FIG. 3 is a fragmentary cross-sectional view of the titanium film forming step. The titanium film 50 is formed on the aluminum oxide film 40 so as to have a film thickness of 20 nm by sputtering after modifying the surface of the aluminum oxide film 40. Since the surface of the aluminum oxide film 40 is terminated with an N—H group by plasma treatment, titanium atoms in the film are not bonded to oxygen in the aluminum oxide and are likely to cause migration on the surface of the aluminum oxide film 40. Become. Since titanium has a strong self-orientation property, when migration on the surface of the aluminum oxide film 40 is promoted, a titanium film 50 with good crystallinity is formed on the aluminum oxide film 40.

FIG. 4 is a cross-sectional view of the main part of the titanium nitride film forming step. The titanium nitride film 51 is formed by nitriding the titanium film 50 by performing an RTA process in a nitrogen atmosphere. The conditions of the RTA treatment are, for example, a substrate temperature of 650 ° C., a nitrogen flow rate of 10 slm (standard liter / min, 1.013 × 10 ⁵ Pa, 0 ° C.), and a treatment time of 90 sec.

  Since the titanium nitride film 51 has good crystallinity of the titanium film 50 before nitriding, the titanium nitride film 51 obtained by nitriding the titanium film 50 also has good crystallinity. The titanium nitride film 51 functions as an orientation improving layer that improves the crystallinity of the film formed in the next step.

  FIG. 5 is a fragmentary cross-sectional view of the film lamination step. The stack is composed of a titanium aluminum nitride film 60 as an oxygen barrier layer, an iridium film 70 as a lower electrode, a ferroelectric film 80 as a capacitor, an iridium oxide film 90 as an upper electrode, and an iridium film 100 in order from the lower layer. Has been.

  Specifically, the titanium aluminum nitride film 60 is formed by sputtering so that the film thickness becomes 100 nm. Next, an iridium film 70 as a lower electrode is formed by a sputtering method so as to have a film thickness of 100 nm. Subsequently, a first PZT film having a thickness of 5 nm is formed on the iridium film 70 by MOCVD, and a second PZT film having a thickness of 115 nm is formed thereon by MOCVD. A ferroelectric film 80 is formed. The substrate temperature when forming the PZT film is, for example, 620 ° C. and the pressure is 5 Torr.

  The first and second PZT films have the same composition. However, the first layer is formed with the oxygen partial pressure lowered. This is because the crystallinity of the PZT film itself is better when the film is formed at a lower oxygen partial pressure. However, if the second layer is also formed at a low oxygen partial pressure, oxygen vacancies in the PZT film increase and the leakage current increases. Therefore, here, the first and second layers have different film formation conditions. The growth method is adopted.

  Next, an iridium oxide film 90 having a thickness of 150 nm is formed on the ferroelectric film 80 by a sputtering method, and then an iridium film 100 having a thickness of 50 nm is formed. The iridium oxide film 90 and the iridium film 100 serve as the upper electrode of the ferroelectric film 80.

  FIG. 6 is a fragmentary cross-sectional view of the process of forming the ferroelectric capacitor. The stacked film described above is patterned and etched to form a ferroelectric capacitor 102 having a stacked capacitor structure. The ferroelectric capacitor 102 having a stacked capacitor structure includes a lower electrode made of an iridium film 70, an upper electrode 101 made of an iridium oxide film 90 and an iridium film 100, and a ferroelectric film 80 inserted therebetween. Thus, in the stacked capacitor structure, the lower electrode of the ferroelectric capacitor 102 is formed in an island shape so as to cover each plug electrode and its peripheral region.

  Thereafter, recovery annealing is performed in order to recover damage to the ferroelectric film 80 by forming the upper electrode. The recovery annealing conditions are, for example, an annealing furnace temperature of 550 ° C., an oxygen atmosphere, and a time of 60 minutes.

  FIG. 7 is a fragmentary cross-sectional view of the aluminum oxide protective film forming step. Here, the aluminum oxide protective film 110 having good step coverage is formed to a thickness of 20 nm by an atomic layer deposition (ALD) method.

  FIG. 8 is a fragmentary cross-sectional view of the step of forming the second interlayer insulating film. The second interlayer insulating film 120 is formed by an HDP (High Density Plasma) device. The second interlayer insulating film 120 is formed on the aluminum oxide protective film 110, and then the upper surface is polished by a CMP process. The remaining film thickness after the CMP process is 300 nm from the upper electrode 100.

  FIG. 9 is a fragmentary cross-sectional view of the plug electrode forming step. Specifically, a contact hole 130 connected to the lower tungsten layer 30b is formed in the second interlayer insulating film 120 by patterning and etching. Thereafter, a glue film 131 a of titanium nitride is formed on the inner wall of the contact hole 130. The film thickness of the glue film 131a is 50 nm.

  Then, after a tungsten layer 131b is formed by a CVD method, a CMP process is performed to flatten the upper surface. At this stage, via-to-via contact can be realized by the plug electrode 30 and the plug electrode 131, and contact from the metal wiring located in the upper layer to the substrate 10 is achieved. Then, in order to prevent oxidation of the plug electrode 131, an antioxidant film (for example, SiON film) is formed to a thickness of 100 nm on the second interlayer insulating film 120 and the plug electrode 131 (not shown).

  FIG. 10 is a fragmentary cross-sectional view of the plug electrode forming step. Specifically, a contact hole 140 reaching the iridium film 100 constituting the upper electrode of the ferroelectric capacitor is formed in the second interlayer insulating film 120 by patterning and etching. Thereafter, recovery annealing is performed. Recovery annealing conditions are, for example, a furnace temperature of 500 ° C., an oxygen atmosphere, and a time of 60 minutes. Then, an antioxidant film (for example, SiON film) having a thickness of 100 nm is removed by etch back.

Next, the contact holes are filled with a titanium nitride glue film 141a and a tungsten layer 141b, and the upper surface is polished by CMP to form a plug electrode 141.
Further, the first metal wiring 150 is formed on the plug electrode 141 by patterning and etching. The first metal wiring 150 is formed by sequentially forming a titanium nitride film 150a having a thickness of 70 nm, an aluminum copper (Al—Cu) film 150b having a thickness of 360 nm, and a titanium nitride film 150c having a thickness of 50 nm.

  The subsequent manufacturing steps are not shown in the figure, but the metal wiring in the second and subsequent layers and the plug electrode between the wirings are formed in order, a cover film made of silicon nitride (SiN) is formed, and finally To FRAM.

  In the above description, ammonia is used as the plasma gas for modifying the surface of the aluminum oxide film, but it is not particularly limited to ammonia. Any gas that can terminate the surface of the aluminum oxide film with an N—H group, that is, a gas containing nitrogen and hydrogen may be used.

  The semiconductor device manufactured in this manner includes an alignment reset layer and an oxygen barrier layer on the plug electrode. Therefore, the orientation of the lower electrode and the ferroelectric film can be improved, and the plug electrode can be prevented from being oxidized at the same time.

  Next, the results of studying the effect of the above-described aluminum oxide film will be described. Here, in order to confirm the effect of the aluminum oxide film, an X-ray diffraction (XRD) measurement sample for macroscopically evaluating the crystallinity of the iridium film on the plug electrode was prepared.

  Two types of samples were prepared. As a sample substrate, a silicon wafer was used. First, a 150 nm-thickness silicon oxide film was formed on the surface by thermal oxidation. A titanium nitride film to be a glue film was formed on the entire surface of the wafer so as to have a film thickness of 50 nm, and a tungsten film was formed on the entire surface of the wafer by CVD. Thereafter, the tungsten surface was polished by CMP treatment, and the final tungsten film thickness was set to 150 nm.

  In the first sample (sample A), a plasma treatment with ammonia gas was directly performed on the tungsten film without forming an aluminum oxide film on the tungsten film of the wafer. Further, a titanium nitride film was formed thereon so as to have a film thickness of 20 nm, and subsequently, a titanium aluminum nitride film was formed so as to have a film thickness of 100 nm. Further, an iridium film was formed so as to have a film thickness of 100 nm.

  In another sample (sample B), an aluminum oxide film is formed on a tungsten film so as to have a thickness of 2 nm, and then the surface of the aluminum oxide film is subjected to plasma treatment with ammonia gas. Further on this, a titanium nitride film was formed to a thickness of 20 nm. After performing RTA treatment and nitriding, a titanium aluminum nitride film was formed to a thickness of 100 nm. Further, an iridium film was formed so as to have a film thickness of 100 nm.

That is, both samples are manufactured in the same manufacturing process except for the presence or absence of an aluminum oxide film.
The measurement location of X-ray diffraction is the wafer center. Then, with respect to the iridium (111) peak, a rocking curve measurement is performed to obtain a full width at half maximum (FWHM). The half width means that the narrower the better the crystallinity.

FIG. 11 shows the rocking curve result of X-ray diffraction of Sample A. FIG. 12 shows the rocking curve result of X-ray diffraction of Sample B.
As a result, in the sample A shown in FIG. 11, the half width of the iridium (111) peak was close to 10 °. On the other hand, in Sample B shown in FIG. 12, the FWHM of the iridium (111) peak decreased to 4.74 °. In addition, in Sample B shown in FIG. 12, the integrated intensity of the (111) peak increased. That is, it can be seen that the iridium film formed by inserting aluminum oxide has improved crystallinity.

  Furthermore, for sample B, the thickness of the aluminum oxide film was changed, samples were prepared separately, and X-ray diffraction measurement was performed. As a result, when the film thickness of the aluminum oxide film was 3 nm, the full width at half maximum was 4.70 °, and when the film thickness was 5 nm, the full width at half maximum was 4.92 °. Thus, it can be seen that even if the film thickness of the aluminum oxide film is changed from 2 nm to 5 nm, the half width of the iridium (111) peak is reduced, and the crystal orientation of the iridium film is improved.

  As described above, the aluminum oxide film can be improved in crystallinity by being subjected to predetermined plasma treatment, and the film formed thereon can be electrically connected to the plug electrode. The range is ensured, and the film thickness is preferably in the range of 1 nm to 5 nm.

  When the film thickness of the aluminum oxide film is less than 1 nm, there is a high possibility that the effect of improving the crystallinity of the film formed thereon will be reduced, and when the film thickness of the aluminum oxide exceeds 5 nm, the plug electrode This is because there is a high possibility that electrical continuity with the above cannot be ensured.

  From the above, according to the present invention, even when an oxygen barrier layer is used in an FRAM having a stacked capacitor structure, the crystallinity of the lower electrode is improved by forming aluminum oxide on the plug electrode and performing surface treatment. Thus, the crystallinity of the ferroelectric film can be improved. As a result, a semiconductor device including a ferroelectric capacitor having a high switching charge amount Qsw, that is, high reliability can be obtained.

  The above merely illustrates the principle of the present invention. In addition, many modifications and changes can be made by those skilled in the art, and the present invention is not limited to the precise configuration and application shown and described above, and all corresponding modifications and equivalents may be And the equivalents thereof are considered to be within the scope of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 11 Element isolation region 12 Well region 20 MOS transistor 21 Cover insulating film 22 First interlayer insulating film 23 Impurity diffusion region 24, 130, 140 Contact hole 30, 131, 141 Plug electrode 30a, 131a, 141a Glue film 30b, 131b, 141b Tungsten layer 40 Aluminum oxide film 50 Titanium film 51, 150a, 150c Titanium nitride film 60 Titanium aluminum nitride film 70,100 Iridium film 80 Ferroelectric film 90 Iridium oxide film 101 Upper electrode 102 Ferroelectric capacitor 110 Aluminum oxide protective film 120 Second interlayer insulating film 150 First metal wiring 150b Aluminum copper film

Claims (4)

  Forming a plug electrode connected to an element formed on the semiconductor substrate on an insulating film on the semiconductor substrate;
  Forming an aluminum oxide film having an oxygen deficiency inside and a film thickness of 1 nm to 5 nm on the plug electrode;
  Performing a plasma treatment using a gas containing nitrogen and hydrogen on the aluminum oxide film;
  Forming a titanium film on the aluminum oxide film after the plasma treatment;
  Nitriding the titanium film to form a titanium nitride film;
  Forming a titanium aluminum nitride film on the titanium nitride film;
  Forming an iridium film on the titanium aluminum nitride film as a lower electrode of a ferroelectric capacitor;
  A method for manufacturing a semiconductor device, comprising:   2. The method of manufacturing a semiconductor device according to claim 1, wherein when forming the aluminum oxide film, the aluminum oxide film is formed in an atmosphere of only argon using a sputtering method. 3.   In the step of performing the plasma treatment, the surface of the aluminum oxide film is modified by the plasma treatment,
  In the step of forming the titanium film and the step of forming the titanium nitride film, a seed layer made of titanium is formed as the titanium film on the aluminum oxide film whose surface has been modified, and the seed layer is formed. The method for manufacturing a semiconductor device according to claim 1, wherein the titanium nitride film is formed by nitriding.   4. The method for manufacturing a semiconductor device according to claim 1, wherein the gas containing nitrogen and hydrogen is ammonia.

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