JP2004022553A - Method for manufacturing ferroelectric memory device, and ferroelectric memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve electrical characteristic of a capacitor by preventing film peeling which is to be caused by water and hydrogen in an insulating film coating the capacitor having a ferroelectric film and preventing reduction of the ferroelectric film. <P>SOLUTION: The method for manufacturing a ferroelectric storage device which is provided with the capacitor 16 having the ferroelectric film 14 is provided with a process for forming the capacitor 16, a process for forming an interlayer insulating film 19 (insulating film) constituted of a barrier film 17 coating the capacitor 16 and of the insulating film 18, a process for forming a contact hole 20 from the interlayer insulating film 19 to an upper electrode film 15 of the capacitor 16 of a lower layer, and a process for forming a wiring 21 which is connected with the capacitor 16 via the contact hole 20. In the method, thermal treatment is performed in oxygen atmosphere of at least 100°C and at most 850°C after the insulating film (e.g. the barrier film 17) is formed and before the contact hole 20 is formed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a ferroelectric memory device and a ferroelectric memory device, and more particularly to a method for manufacturing a ferroelectric memory device for removing moisture and hydrogen contained in an insulating film covering a capacitor and a method for manufacturing the same. And a ferroelectric memory device manufactured by the same.
[0002]
[Prior art]
After an aluminum oxide film is formed on the capacitor formed on the insulating film by sputtering or CVD, for example, a contact hole reaching the upper electrode of the capacitor is opened, and the capacitor is electrically connected to the upper electrode through the contact hole. Wiring is formed. Water or hydrogen is generated from the insulating film by the heat generated when the aluminum wiring is formed, and the generated water or hydrogen enters through the contact hole to reduce the ferroelectric film. As a result, the electrical characteristics of the capacitor deteriorated.
[0003]
Next, a conventional manufacturing method will be described with reference to a manufacturing process diagram of FIG.
As shown in FIG. 5A, a silicon oxide film 12 is formed on a silicon substrate 11 to a thickness of, for example, 300 nm by a thermal oxidation method. Next, the lower electrode film 13 is formed on the silicon oxide film 12 by sputtering, for example, titanium oxide (TiO 2). ₂ After forming the film 131 to a thickness of 40 nm, an iridium (Ir) film 132 is formed to a thickness of 100 nm. Next, a ferroelectric film 14 is formed on the lower electrode film 13 by a spin coating method. Here, SrBi ₂ Ta ₂ O ₉ Was formed into a film having a thickness of 100 nm. At this time, the crystallization temperature of the ferroelectric film 14 was set to 700 ° C. to 800 ° C. in an oxygen atmosphere. Further, by sputtering, iridium (Ir) is deposited to a thickness of 100 nm on the ferroelectric film 14 to form the upper electrode film 15.
[0004]
Thereafter, as shown in FIG. 5B, the upper electrode film 15, the ferroelectric film 14, and the lower electrode film 13 are sequentially processed to form the capacitor 16.
[0005]
Next, as shown in FIG. 5C, a barrier film 17 covering the capacitor 16 is formed by depositing an aluminum oxide film to a thickness of, for example, 50 nm by sputtering or CVD. Further, an insulating film 18 is formed on the barrier film 17 by sputtering or CVD, for example, by depositing silicon oxide to a thickness of 250 nm. Therefore, the thickness of the interlayer insulating film 19 composed of the barrier film 17 and the insulating film 18 is 300 nm.
[0006]
Thereafter, as shown in FIG. 5D, a contact hole 20 reaching the upper electrode film 15 of the capacitor 16 is formed in the interlayer insulating film 19, and a wiring 21 connected to the upper electrode film 15 through the contact hole 20 is formed. Is formed of, for example, an aluminum-based material.
[0007]
Next, the electrical characteristics of the capacitor 16 manufactured by the manufacturing method described with reference to FIG. 5 were evaluated. Furthermore, the electrical characteristics after nitrogen sintering were also evaluated. FIG. 6 shows a current (leakage current) -voltage (applied voltage) characteristic (hereinafter, referred to as an IV characteristic) immediately after the wiring 21 is formed. FIG. 7 shows IV characteristics immediately after nitrogen sintering. The nitrogen sintering was performed in a nitrogen atmosphere at 400 ° C. for 30 minutes. As a result, a decrease in the breakdown voltage was observed immediately after the nitrogen sintering as compared to immediately after the formation of the wiring 21. It is considered that this withstand voltage deterioration is caused by hydrogen and moisture in the barrier film 17 and the insulating film 18 due to the nitrogen sinter.
[0008]
Alternatively, after a barrier film made of, for example, an aluminum oxide film is formed on a capacitor having a ferroelectric film by a sputtering method or a CVD method, an insulating film made of an oxide film such as silicon oxide is formed by a sputtering method or a CVD method. Form a film. Thereafter, a contact hole is opened from the insulating film to the upper electrode film of the capacitor. Thereafter, heat treatment is performed at a temperature of 400 ° C. in an inert gas atmosphere or a nitrogen atmosphere as an inert gas to release moisture and hydrogen in the insulating film made of an oxide film to the outside of the film. Thereafter, a wiring for conducting with the upper electrode film is formed by, for example, an aluminum wiring.
[0009]
This conventional manufacturing method will be described below with reference to a manufacturing process sectional view of FIG.
[0010]
As shown in FIG. 8A, a silicon oxide film 12 having a thickness of, for example, 300 nm is formed on a silicon substrate 11 by a thermal oxidation method as described with reference to FIG. Next, the lower electrode film 13 is formed on the silicon oxide film 12 by sputtering, for example, titanium oxide (TiO 2). ₂ After forming the film 131 to a thickness of 40 nm, an iridium (Ir) film 132 is formed to a thickness of 100 nm. Next, a ferroelectric film 14 is formed on the lower electrode film 13 by a spin coating method. Here, SrBi ₂ Ta ₂ O ₉ Was formed into a film having a thickness of 100 nm. At this time, the crystallization temperature of the ferroelectric film 14 was set to 700 ° C. to 800 ° C. in an oxygen atmosphere. Further, by sputtering, iridium (Ir) is deposited to a thickness of 100 nm on the ferroelectric film 14 to form the upper electrode film 15.
[0011]
Thereafter, as shown in FIG. 5 (2), the upper electrode film 15, the ferroelectric film 14, and the lower electrode film 13 are sequentially processed to form the capacitor 16.
[0012]
Next, as shown in FIG. 5C, a barrier film 17 covering the capacitor 16 is formed by sputtering or CVD to deposit an aluminum oxide film to a thickness of, for example, 50 nm. Further, an insulating film 18 is formed on the barrier film 17 by sputtering or CVD, for example, by depositing silicon oxide to a thickness of 250 nm. Therefore, the thickness of the interlayer insulating film 19 composed of the barrier film 17 and the insulating film 18 is 300 nm.
[0013]
Thereafter, a contact hole 20 reaching the upper electrode film 15 is formed in the interlayer insulating film 19 in the same manner as described with reference to FIG. Thereafter, heat treatment is performed in a nitrogen atmosphere at 400 ° C. for one hour.
[0014]
Next, as shown in FIG. 8B, the wiring 21 connected to the upper electrode film 15 through the contact hole 20 is made of, for example, an aluminum-based material in the same manner as described with reference to FIG. Form.
[0015]
The electrical characteristics of the capacitor manufactured by the manufacturing method described with reference to FIG. 8 were evaluated. Furthermore, the electrical characteristics after nitrogen sintering were also evaluated. FIG. 9 shows IV characteristics immediately after the aluminum wiring is formed. FIG. 10 shows IV characteristics immediately after the nitrogen sintering. This nitrogen sinter was performed in a nitrogen atmosphere at 400 ° C. for 30 minutes. As a result, in the manufacturing method shown in FIG. 8, the voltage at which the leak current occurs is higher and the breakdown voltage is better because the leak current is smaller than in the manufacturing method shown in FIG. 5. It was recognized that.
[0016]
Further, after the step of forming the aluminum wiring is completed, a nitrogen sintering process is performed to improve the contact characteristics. Further, forming annealing for restoring the characteristics of the transistor formed on the same substrate, which has deteriorated in the process of forming the capacitor, is performed. This sintering is performed in a nitrogen atmosphere, for example, at a temperature of about 400 ° C. The forming annealing is performed at a temperature of about 400 ° C. in an atmosphere of, for example, 5% of hydrogen and 95% of nitrogen. Note that the forming annealing need not always be performed.
[0017]
[Problems to be solved by the invention]
However, due to the heat generated when forming the aluminum wiring, water or hydrogen is generated from the insulating film, and the generated water or hydrogen enters through the contact hole, and the ferroelectric film is reduced. There was a problem of deterioration. Further, there is a problem that the electrical characteristics are deteriorated after the forming annealing.
[0018]
As a factor of the deterioration of the electric characteristics, when nitrogen sintering is performed after the aluminum wiring is formed, water and hydrogen are generated from the oxide insulating film. Alternatively, water generated from the oxide insulating film reacts with aluminum to generate a larger amount of hydrogen. The water and hydrogen thus generated diffuse from the opening of the contact hole into the upper electrode and the ferroelectric film, and the water and hydrogen cause peeling of the film, thereby deteriorating the electrical characteristics.
[0019]
[Means for Solving the Problems]
The present invention provides a method of manufacturing a ferroelectric memory device and a ferroelectric memory device which have been made to solve the above problems.
[0020]
A method for manufacturing a ferroelectric memory device according to the present invention is a method for manufacturing a ferroelectric memory device including a capacitor having a ferroelectric film, wherein a step of forming the capacitor and an insulating film covering the capacitor are provided. Forming a contact hole below the insulating film, and forming a wiring connected to the capacitor through the contact hole, the method of manufacturing a ferroelectric memory device, comprising: After the formation and before the formation of the contact hole, a heat treatment is performed in an oxygen atmosphere of 100 ° C. or more and 850 ° C. or less.
[0021]
In the method of manufacturing a ferroelectric memory device, the heat treatment is performed in an oxygen atmosphere at 100 ° C. or more and 850 ° C. or less after forming the insulating film and before forming the contact hole. Is released from the film. That is, since the heat treatment temperature is 100 ° C. or higher, the separated moisture is vaporized, and the hydrogen is combined with oxygen and vaporized, and is removed from the film. Since the moisture and hydrogen in the insulating film have been removed in this way, even if a contact hole is formed in the insulating film that leads to the upper electrode film of the capacitor, the hydrogen and moisture in the insulating film are transferred to the ferroelectric film through the contact hole. And the ferroelectric film is not reduced.
[0022]
Further, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds at a portion from which moisture or hydrogen has been released, and the oxide film is more densely formed, so that a stronger oxide film is obtained. Even when the insulating film is made of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is more densely formed, so that a stronger oxynitride film is obtained. Thereby, invasion of hydrogen from the outside can be prevented.
[0023]
Therefore, it is possible to prevent the deterioration of the electric characteristics of the capacitor, especially the deterioration of the withstand voltage. Further, peeling of the film due to hydrogen or moisture is prevented, and deterioration of the film adhesion is also prevented. Therefore, a stable ferroelectric memory device is manufactured.
[0024]
A ferroelectric memory device according to the present invention includes a capacitor having a ferroelectric film, an insulating film covering the capacitor, a contact hole extending from the insulating film to the capacitor, and a wiring connected to the capacitor through the contact hole. Wherein the heat treatment is performed in an oxygen atmosphere of 100 ° C. or more and 850 ° C. or less after forming the insulating film and before forming the contact hole. Things.
[0025]
In the ferroelectric memory device, the heat treatment is performed in an oxygen atmosphere at a temperature of 100 ° C. or more and 850 ° C. or less before forming the contact hole after forming the insulating film. Is that moisture and hydrogen in the insulating film are released from the film. That is, since the heat treatment temperature is 100 ° C. or higher, the released moisture is vaporized, and the hydrogen is combined with oxygen to be vaporized and removed from the film. As described above, since moisture and hydrogen in the insulating film have been released, even if a contact hole is formed in the insulating film, which leads to the upper electrode film of the capacitor, the hydrogen and moisture in the insulating film are transferred to the ferroelectric substance through the contact hole. Infiltration into the film is avoided, and the ferroelectric film is not reduced.
[0026]
Further, since the heat treatment is performed in an oxygen atmosphere, moisture and hydrogen are released, oxygen is bonded to dangling bonds in the portion, and the oxide film is more densely formed, so that a stronger oxide film is formed. Further, even when the insulating film is formed of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is formed more densely, so that a stronger oxynitride film is obtained. Thereby, invasion of hydrogen from the outside can be prevented.
[0027]
Therefore, the capacitor has no deterioration in electrical characteristics, particularly, no deterioration in breakdown voltage. Further, since peeling of the film due to hydrogen and moisture is prevented, there is no deterioration in the adhesion of the film. Therefore, a stable ferroelectric memory device is obtained.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
The ferroelectric memory device of the present invention has a capacitor provided with an upper electrode and a lower electrode so as to sandwich a ferroelectric film, and upper and lower electrodes such as iridium (Ir) and platinum (Pt). An electrode made of a noble metal is used. As a ferroelectric material constituting the ferroelectric film, for example, PbZr _x Ti _1-x O ₃ , PbTiO ₃ Lead compounds such as SrBi ₂ Ta ₂ O ₉ , Bi ₄ Ti ₃ O ₁₂ And the like can be used. These ferroelectric films can be formed by an MOD (Metal Organic Decomposition) method using an alkoxide raw material, a laser ablation method, an MOCVD (Metal Organic Chemical Vapor Deposition) method, a spin coating method, an LSMCD method, or the like. After film formation, heat treatment is performed to crystallize and stabilize.
[0029]
Next, an aluminum oxide film is formed on the capacitor by a sputtering method or a CVD method as a film for preventing entry of hydrogen from the outside into the capacitor as an insulating film. Further thereon, an insulating film of an oxide such as silicon oxide is formed by a sputtering method or a CVD method. Thus, a laminated insulating film structure was obtained. Next, dehydration and dehydrogenation of the oxide insulating film are performed by heat treatment. By this heat treatment, the adhesion between the films is enhanced, and even if heat treatment is performed in a later step, film peeling does not occur, and a stable capacitor without deterioration in characteristics can be obtained.
[0030]
Next, a first embodiment of the method of manufacturing a ferroelectric memory device according to the present invention will be described with reference to the manufacturing process diagram of FIG.
[0031]
As shown in FIG. 1A, a silicon oxide film 12 is formed on a silicon substrate 11 to a thickness of, for example, 300 nm by a thermal oxidation method. Next, the lower electrode film 13 is formed on the silicon oxide film 12 by sputtering, for example, titanium oxide (TiO 2). ₂ After forming the film 131 to a thickness of 40 nm, an iridium (Ir) film 132 is formed to a thickness of 100 nm. Next, a ferroelectric film 14 is formed on the lower electrode film 13 by a spin coating method. Here, SrBi ₂ Ta ₂ O ₉ Was formed into a film having a thickness of 100 nm. At this time, the crystallization temperature of the ferroelectric film 14 was set to 700 ° C. to 800 ° C. in an oxygen atmosphere. Next, iridium (Ir) is deposited to a thickness of 100 nm on the ferroelectric film 14 by a sputtering method to form the upper electrode film 15.
[0032]
Thereafter, as shown in FIG. 1B, the upper electrode film 15, the ferroelectric film 14, and the lower electrode film 13 are sequentially processed to form the capacitor 16.
[0033]
Then, as shown in FIG. 1C, an aluminum oxide film is coated as the barrier film 17 for covering the capacitor 16 by a sputtering method or a CVD method and preventing hydrogen from entering the capacitor 16, for example, It is formed to a thickness of 50 nm. After that, heat treatment is performed in an oxygen atmosphere. Here, heat treatment was performed in an oxygen atmosphere at 400 ° C. for one hour. This heat treatment is performed in an oxygen atmosphere at 100 ° C. to 850 ° C. The barrier film 17 is made of tantalum oxide (Ta) in addition to aluminum oxide. ₂ O ₅ ), Hafnium oxide (HfO ₂ ), Titanium oxide (TiO) ₂ ), Zirconium oxide (ZnO) ₂ ), Silicon nitride (SiN), titanium nitride (TiN), aluminum nitride (AlN), or the like.
[0034]
The reason why the heat treatment temperature in the oxygen atmosphere is set to 100 ° C. to 850 ° C. is that if the heat treatment temperature is lower than 100 ° C., vaporization of moisture in the insulating film becomes insufficient. Characteristics may be adversely affected. Therefore, the heat treatment in an oxygen atmosphere was performed within the above temperature range.
[0035]
Further, as shown in FIG. 1D, an insulating film 18 made of silicon oxide is formed on the barrier film 17 to a thickness of, for example, 250 nm by sputtering or CVD. Therefore, the thickness of the interlayer insulating film 19 composed of the barrier film 17 and the insulating film 18 is 300 nm.
[0036]
Thereafter, as shown in FIG. 1 (5), a contact hole 20 reaching the upper electrode film 15 is formed in the interlayer insulating film 19, and a wiring 21 connected to the upper electrode film 15 through the contact hole 20 is formed, for example. It is formed of an aluminum-based material.
[0037]
In the method of manufacturing the ferroelectric memory device according to the first embodiment, the heat treatment is performed in an oxygen atmosphere of 100 ° C. or more and 850 ° C. or less before forming the contact hole after forming the barrier film 17 as the insulating film. As a result, moisture and hydrogen in the barrier film 17 are released from the film. That is, since the heat treatment temperature is 100 ° C. or higher, the separated moisture is vaporized, and the hydrogen is combined with oxygen and vaporized, and is removed from the film. In this manner, moisture and hydrogen in the barrier film 17 are released, so that even if a contact hole 20 leading to the upper electrode film 15 of the capacitor is formed in the barrier film 17, hydrogen and hydrogen in the barrier film 17 are formed through the contact hole 20. The entry of moisture into the ferroelectric film 14 is avoided, and the reduction of the ferroelectric film 14 is suppressed.
[0038]
Furthermore, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds from which moisture and hydrogen have been released, and the oxide film is more densely formed, so that a stronger oxide film is obtained. Even when the barrier film 17 is made of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is more densely formed, so that a stronger oxynitride film is obtained. Thereby, invasion of hydrogen from the outside can be sufficiently prevented.
[0039]
Therefore, it is possible to prevent the deterioration of the electrical characteristics of the capacitor 16, particularly the deterioration of the breakdown voltage. Further, peeling of the film due to hydrogen or moisture is prevented, and deterioration of the film adhesion is also prevented. Therefore, a stable ferroelectric memory device is manufactured.
[0040]
In the ferroelectric memory device manufactured by the method of manufacturing a ferroelectric memory device according to the first embodiment, after forming the barrier film 17 and before forming the contact hole, the oxygen of 100 to 850 ° C. Since the heat treatment is performed in the atmosphere, at least moisture and hydrogen in the barrier film 17 are eliminated from the film before forming the contact hole. That is, since the heat treatment temperature is 100 ° C. or higher, the released moisture is vaporized, and the hydrogen is combined with oxygen to be vaporized and removed from the film. Since moisture and hydrogen in the barrier film 17 are thus separated, even if a contact hole 20 leading to the upper electrode film 15 of the capacitor is formed, hydrogen and moisture enter the ferroelectric film 14 through the contact hole 20. And the reduction of the ferroelectric film 14 is suppressed.
[0041]
Furthermore, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds from which moisture and hydrogen have been released, and the oxide film is more densely formed, so that a stronger oxide film is formed. Even when the barrier film 17 is made of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is formed more densely, so that a stronger oxynitride film is obtained. Thereby, invasion of hydrogen from the outside can be prevented.
[0042]
Therefore, the capacitor 16 is free from deterioration in electrical characteristics, particularly, deterioration in breakdown voltage. Further, since peeling of the film due to hydrogen and moisture is prevented, there is no deterioration in the adhesion of the film. Therefore, a stable ferroelectric memory device is obtained.
[0043]
Next, a second embodiment of the method of manufacturing a ferroelectric memory device according to the present invention will be described with reference to the manufacturing process diagram of FIG.
[0044]
As shown in FIG. 2A, as described with reference to FIGS. 1A and 1B of the first embodiment, a silicon oxide film 12 is formed on a silicon substrate 11 by a thermal oxidation method, for example. It is formed to a thickness of 300 nm. Next, the lower electrode film 13 is formed on the silicon oxide film 12 by sputtering, for example, titanium oxide (TiO 2). ₂ After forming the film 131 to a thickness of 40 nm, an iridium (Ir) film 132 is formed to a thickness of 100 nm. Next, a ferroelectric film 14 is formed on the lower electrode film 13 by a spin coating method. Here, SrBi ₂ Ta ₂ O ₉ Was formed into a film having a thickness of 100 nm. At this time, the crystallization temperature of the ferroelectric film 14 was set to 700 ° C. to 800 ° C. in an oxygen atmosphere. Next, iridium (Ir) is deposited to a thickness of 100 nm on the ferroelectric film 14 by a sputtering method to form the upper electrode film 15. After that, the upper electrode film 15, the ferroelectric film 14, and the lower electrode film 13 are sequentially processed to form the capacitor 16.
[0045]
Next, as shown in FIG. 2B, a barrier film 17 for covering the capacitor 16 is formed by, for example, depositing aluminum oxide to a thickness of 50 nm by sputtering or CVD. After that, heat treatment is performed in an oxygen atmosphere. Here, heat treatment was performed in an oxygen atmosphere at 400 ° C. for one hour. This heat treatment is performed in an oxygen atmosphere at 100 ° C. to 850 ° C. The barrier film 17 is made of tantalum oxide (Ta) in addition to aluminum oxide. ₂ O ₅ ), Hafnium oxide (HfO ₂ ), Titanium oxide (TiO) ₂ ), Zirconium oxide (ZnO) ₂ ), Silicon nitride (SiN), titanium nitride (TiN), aluminum nitride (AlN), or the like.
[0046]
Further, as shown in FIG. 2C, a silicon oxide film 18 is formed on the aluminum oxide film 17 to a thickness of, for example, 250 nm by sputtering or CVD. After that, heat treatment is performed in an oxygen atmosphere. Here, heat treatment was performed in an oxygen atmosphere at 400 ° C. for one hour. This heat treatment is performed in an oxygen atmosphere at 100 ° C. to 850 ° C. Therefore, the thickness of the interlayer insulating film 19 is 300 nm.
[0047]
Thereafter, as shown in FIG. 2D, a contact hole 20 reaching the upper electrode film 15 is formed in the interlayer insulating film 19, and a wiring 21 connected to the upper electrode film 15 through the contact hole 20 is formed, for example. It is formed of an aluminum-based material.
[0048]
In the method of manufacturing the ferroelectric memory device according to the second embodiment, after forming the barrier film 17 and the insulating film 18 and before forming the contact hole, the heat treatment is performed in an oxygen atmosphere at 100 ° C. or more and 850 ° C. or less. As a result, moisture and hydrogen in the barrier film 17 and the insulating film 18 are released from the film. That is, since the heat treatment temperature is 100 ° C. or higher, the separated moisture is vaporized, and the hydrogen is combined with oxygen and vaporized, and is removed from the film. Since the moisture and hydrogen in the barrier film 17 and the insulating film 18 have been removed in this manner, even if the contact hole 20 communicating with the upper electrode film 15 of the capacitor 16 is formed in the barrier film 17 and the insulating film 18, The entry of hydrogen and moisture in the barrier film 17 and the insulating film 18 into the ferroelectric film 14 through the holes 20 is avoided, and the ferroelectric film 14 is not reduced.
[0049]
Furthermore, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds from which moisture and hydrogen have been released, and the oxide film is more densely formed, so that a stronger oxide film is obtained. Further, even when the barrier film 17 and the insulating film 18 are made of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is more densely formed, so that a stronger oxynitride film is obtained. Thereby, invasion of hydrogen from the outside can be prevented.
[0050]
Therefore, it is possible to prevent the deterioration of the electrical characteristics of the capacitor 16, particularly the deterioration of the breakdown voltage. Further, peeling of the film due to hydrogen or moisture is prevented, and deterioration of the film adhesion is also prevented. Therefore, a stable ferroelectric memory device is manufactured.
[0051]
Next, a third embodiment of the method of manufacturing a ferroelectric memory device according to the present invention will be described with reference to the manufacturing process diagram of FIG.
[0052]
As shown in FIG. 3A, the silicon oxide film 12 is formed on the silicon substrate 11 by the thermal oxidation method, for example, as described with reference to FIGS. 1A and 1B of the first embodiment. It is formed to a thickness of 300 nm. Next, the lower electrode film 13 is formed on the silicon oxide film 12 by sputtering, for example, titanium oxide (TiO 2). ₂ After forming the film 131 to a thickness of 40 nm, an iridium (Ir) film 132 is formed to a thickness of 100 nm. Next, a ferroelectric film 14 is formed on the lower electrode film 13 by a spin coating method. Here, SrBi ₂ Ta ₂ O ₉ Was formed into a film having a thickness of 100 nm. At this time, the crystallization temperature of the ferroelectric film 14 was set to 700 ° C. to 800 ° C. in an oxygen atmosphere. Next, iridium (Ir) is deposited to a thickness of 100 nm on the ferroelectric film 14 by a sputtering method to form the upper electrode film 15. After that, the upper electrode film 15, the ferroelectric film 14, and the lower electrode film 13 are sequentially processed to form the capacitor 16.
[0053]
Next, as shown in FIG. 3 (2), a barrier film 17 covering the capacitor 16 is formed by, for example, depositing aluminum oxide to a thickness of 50 nm by sputtering or CVD. Subsequently, an insulating film 18 made of an oxide film such as silicon oxide is formed on the barrier film 17 to a thickness of, for example, 250 nm. Therefore, the thickness of the interlayer insulating film 19 including the barrier film 17 and the insulating film 18 is 300 nm. After that, heat treatment is performed in an oxygen atmosphere. Here, heat treatment was performed in an oxygen atmosphere at 400 ° C. for one hour. This heat treatment is performed in an oxygen atmosphere at 100 ° C. to 850 ° C. As the barrier film 17, in addition to aluminum oxide, tantalum oxide (Ta) ₂ O ₅ ), Hafnium oxide (HfO ₂ ), Titanium oxide (TiO) ₂ ), Zirconium oxide (ZnO) ₂ ), Silicon nitride (SiN), titanium nitride (TiN), aluminum nitride (AlN), or the like.
[0054]
Next, as shown in FIG. 3C, a contact hole 20 reaching the upper electrode film 15 is formed in the interlayer insulating film 19, and a wiring 21 connected to the upper electrode film 15 through the contact hole 20 is formed. For example, it is formed of an aluminum-based material.
[0055]
The electrical characteristics of the capacitor manufactured by the manufacturing method described with reference to FIG. 3 were evaluated. This evaluation was performed after performing nitrogen sintering. FIG. 4 shows IV characteristics immediately after the aluminum wiring is formed. As a result, it was found that the manufacturing method of the present invention described with reference to FIG. 3 described above did not generate a leak current and improved the withstand voltage as compared with the capacitor formed by the conventional manufacturing method. The same result was obtained for the capacitor formed by the manufacturing method described with reference to FIGS. 1 and 2.
[0056]
In the method of manufacturing a ferroelectric memory device, since the heat treatment is performed in an oxygen atmosphere at 100 ° C. or more and 850 ° C. or less before forming the contact hole after forming the insulating film 18, the barrier film 17 and the insulating film The moisture and hydrogen in 18 are released from the film. That is, since the heat treatment temperature is 100 ° C. or higher, the separated moisture is vaporized, and the hydrogen is combined with oxygen and vaporized, and is removed from the film. Since the moisture and hydrogen in the barrier film 17 and the insulating film 18 have been removed in this manner, even if the contact hole 20 communicating with the upper electrode film 15 of the capacitor 16 is formed in the barrier film 17 and the insulating film 18, The entry of hydrogen and moisture in the barrier film 17 and the insulating film 18 into the ferroelectric film 14 through the holes 20 is avoided, and the ferroelectric film 14 is not reduced.
[0057]
Furthermore, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds from which moisture and hydrogen have been released, and the oxide film is more densely formed, so that a stronger oxide film is obtained. Further, even when the barrier film 17 and the insulating film 18 are made of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is more densely formed, so that a stronger oxynitride film is obtained. Thereby, invasion of hydrogen from the outside can be prevented.
[0058]
Therefore, it is possible to prevent the deterioration of the electrical characteristics of the capacitor 16, particularly the deterioration of the breakdown voltage. Further, peeling of the film due to hydrogen or moisture is prevented, and deterioration of the film adhesion is also prevented. Therefore, a stable ferroelectric memory device is manufactured.
[0059]
In the ferroelectric memory device manufactured by the method of manufacturing the ferroelectric memory device according to the second or third embodiment, after forming the barrier film 17 and the insulating film 18 or after forming the insulating film 18. Since the heat treatment is performed in an oxygen atmosphere at a temperature of 100 ° C. or more and 850 ° C. or less before forming the contact hole, the moisture or hydrogen in the barrier film 17 and the insulating film 18 is formed before the contact hole is formed. Is detached from the film. That is, since the heat treatment temperature is 100 ° C. or higher, the released moisture is vaporized, and the hydrogen is combined with oxygen to be vaporized and removed from the film. Since the moisture and hydrogen in the insulating film 18 have been separated from the barrier film 17 as described above, even if a contact hole 20 leading to the upper electrode film 15 of the capacitor 16 is formed in the interlayer insulating film 19, Hydrogen and moisture in the interlayer insulating film 19 are prevented from entering the ferroelectric film 14, and the ferroelectric film 14 is not reduced.
[0060]
Furthermore, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds from which moisture and hydrogen have been released, and the oxide film is more densely formed, so that a stronger oxide film is formed. Even when the barrier film 17 and the insulating film 18 are made of a nitride film, the oxygen is bonded to the dangling bond, so that the nitride film is formed more densely, so that a stronger oxynitride film is obtained. . Thereby, invasion of hydrogen from the outside can be prevented.
[0061]
Therefore, the capacitor 16 is free from deterioration in electrical characteristics, particularly, deterioration in breakdown voltage. Further, since peeling of the film due to hydrogen and moisture is prevented, there is no deterioration in the adhesion of the film. Therefore, a stable ferroelectric memory device is obtained.
[0062]
Further, as described in the second embodiment, after forming the barrier film 17, heat treatment is performed in an oxygen atmosphere at 100 ° C. to 850 ° C., and after forming the insulating film 18, 100 ° C. to 850 ° C. In the manufacturing method of the second embodiment, the heat treatment is performed in the oxygen atmosphere at a temperature of 100 ° C. or more and 850 ° C. or less. The effect of removing moisture and hydrogen is further enhanced.
[0063]
In each of the above embodiments, although not shown, an MIS transistor as a selection element is formed on the silicon substrate 11, and the insulating film 12 is formed so as to cover the MIS transistor. Further, a contact connecting the capacitor 16 and the MIS transistor is formed.
[0064]
In each of the above manufacturing methods, SrBi is added to the ferroelectric film 14. ₂ Ta ₂ O ₉ Although the configuration example using SrBi has been described, ₂ Ta ₂ O ₉ Other ferroelectric film materials that can be used for capacitors may be used. For example, PZT [Pb (Zr, Ti) O ₃ ], SrBi ₂ TaO ₉ , BaTiO ₃ , PbTiO ₃ , LiNbO ₃ , LiTaO ₃ , SbSI, (Pb, La) (Zr, Ti) O ₃ , (Bi, La ₄ ) Ti ₃ O ₁₂ , PZT in which Pb is replaced by La, Sr, and Ca, PLSCZT (Pb _0.96 La _0.1 Sr _0.2 Ca _0.1 Zr _0.3 Ti _0.7 O ₃ ), Bi layered ferroelectric Bi ₄ Ti ₃ O ₁₂ Bi in which Bi is replaced with Nd _3.54 Nd _0.46 Ti ₃ O ₁₂ Alternatively, a ferroelectric film such as a ferroelectric film can be used.
[0065]
【The invention's effect】
As described above, according to the method of manufacturing a ferroelectric memory device of the present invention, after forming an insulating film and before forming a contact hole, heat treatment is performed in an oxygen atmosphere at 100 ° C. or more and 850 ° C. or less. Therefore, moisture and hydrogen in the insulating film can be released from the film. For this reason, even if a contact hole leading to the upper electrode film of the capacitor is formed in the insulating film, it is possible to prevent hydrogen and moisture in the insulating film from invading the ferroelectric film through the contact hole and reduce the ferroelectric film. Can be prevented. Further, since the heat treatment is performed in an oxygen atmosphere, oxygen is bonded to dangling bonds, so that the insulating film becomes denser and becomes a strong insulating film. Thereby, invasion of hydrogen from the outside can be prevented. Therefore, it is possible to form a capacitor having excellent electrical characteristics, particularly withstand voltage, and prevent film peeling due to hydrogen or moisture, so that a stable ferroelectric memory device can be manufactured.
[0066]
Since the ferroelectric memory device according to the present invention is manufactured by the method for manufacturing a ferroelectric memory device according to the present invention, the above-described operation and effect can be obtained, and a highly reliable ferroelectric memory device can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a manufacturing process showing a first embodiment of a method of manufacturing a ferroelectric memory device according to the present invention.
FIG. 2 is a sectional view showing a manufacturing process according to a second embodiment of the method for manufacturing a ferroelectric memory device of the present invention.
FIG. 3 is a cross-sectional view showing a manufacturing process according to a third embodiment of the method for manufacturing a ferroelectric memory device of the present invention.
FIG. 4 is a diagram illustrating current-voltage characteristics of a ferroelectric film immediately after nitrogen sintering in a third embodiment.
FIG. 5 is a manufacturing process sectional view showing a method for manufacturing a conventional ferroelectric memory device.
6 is a diagram showing current-voltage characteristics of a ferroelectric film immediately after forming a wiring in the method of manufacturing the conventional ferroelectric memory device shown in FIG.
7 is a diagram showing current-voltage characteristics of a ferroelectric film immediately after performing nitrogen sintering in the method of manufacturing the conventional ferroelectric memory device shown in FIG.
FIG. 8 is a manufacturing process sectional view showing a method for manufacturing a conventional ferroelectric memory device.
9 is a diagram showing current-voltage characteristics of a ferroelectric film immediately after forming a wiring in the method of manufacturing the conventional ferroelectric memory device shown in FIG.
10 is a diagram showing current-voltage characteristics of a ferroelectric film immediately after performing nitrogen sintering in the method of manufacturing the conventional ferroelectric memory device shown in FIG.
[Explanation of symbols]
14: ferroelectric film, 16: capacitor, 17: barrier film (insulating film), 18: insulating film, 20: contact hole, 21: wiring

Claims (8)

A method of manufacturing a ferroelectric memory device including a capacitor having a ferroelectric film,
Forming the capacitor;
Forming an insulating film covering the capacitor;
Forming a contact hole in the lower layer from the insulating film;
Forming a wiring connected to the capacitor through the contact hole, the method of manufacturing a ferroelectric memory device,
A method of manufacturing a ferroelectric memory device, comprising: performing a heat treatment in an oxygen atmosphere at 100 ° C. or more and 850 ° C. or less after forming the insulating film and before forming the contact hole. At least one of the insulating films is formed of a barrier film that prevents hydrogen from entering the capacitor side,
2. The method according to claim 1, wherein the heat treatment is performed after forming the barrier film. The insulating film is formed in a plurality of layers,
2. The method according to claim 1, wherein the heat treatment is performed after each insulating film is formed. The insulating film is formed in a plurality of layers,
2. The method according to claim 1, wherein the heat treatment is performed after all of the plurality of insulating films are formed. A capacitor having a ferroelectric film;
An insulating film covering the capacitor;
A contact hole leading from the insulating film to the capacitor;
A ferroelectric memory device comprising: a wiring connected to the capacitor through the contact hole;
A ferroelectric memory device, wherein a heat treatment is performed in an oxygen atmosphere at a temperature of 100 ° C. or more and 850 ° C. or less after forming the insulating film and before forming the contact hole. At least one of the insulating films is formed of a barrier film that prevents hydrogen from entering the capacitor side,
6. The ferroelectric memory device according to claim 5, wherein the heat treatment is performed after forming the barrier film. The insulating film includes a plurality of insulating films,
6. The ferroelectric memory device according to claim 5, wherein said heat treatment is performed after each of said insulating films is formed. The insulating film includes a plurality of insulating films,
6. The ferroelectric memory device according to claim 5, wherein the heat treatment is performed after forming all of the plurality of insulating films.

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