JP2003100994A - Ferroelectric memory and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric memory having sufficient memory characteristics by protecting a ferroelectric capacitor against moisture generated during a manufacturing process, and to provide a ferroelectric memory which reduces effects of hydrogen generated in the case of forming a passivation film and a method for manufacturing the same. SOLUTION: The ferroelectric memory comprises a semiconductor substrate 1, a ferroelectric capacitor 7 formed on the substrate 1, a first interlayer film 3 including the capacitor 7, and metal wiring 1M penetrating the film 3. The memory further comprises a moisture diffusion preventive film 4 formed on the film 3. The method for manufacturing the ferroelectric memory comprises a step of forming the moisture diffusion preventive film formed on at least the first interlayer film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric memory and a method of manufacturing the same.

[0002]

2. Description of the Related Art Ferroelectric memories have been attracting attention as next-generation non-volatile memories, and research and development are being actively pursued in each research institute. As a conventional ferroelectric memory, a configuration as shown in FIG. 3 is known, and is manufactured as follows. First, the transistor 32 and the ferroelectric capacitor 33 are provided on the Si substrate 31, and the SiO ₂ film which is the first interlayer film 34 is formed by the CVD method. After removing water in the first interlayer film 34 by heat treatment, contact holes 35C and 36C for connection with the transistor 32 and the ferroelectric capacitor 33 are formed. After the wiring 37M for the transistor 32 and the ferroelectric capacitor 33 is formed by the spattering method, it is etched into a desired pattern. A SiO ₂ film is formed as the second interlayer film 38 by the CVD method, and a contact hole 39 is formed on the wiring 37M for connecting the peripheral circuit and the ferroelectric memory cell. After the wiring 40M is formed by the sputtering method, it is formed into a desired pattern.
Finally, a passivation film 40 is formed as a protective film.

However, when the ferroelectric memory is manufactured as described above, moisture (adsorbed water generated in the cleaning step and the second interlayer film 3) generated in the process after the formation of the wiring 37M is performed.
(Structure water contained in No. 8) was not removed, and there was a problem that sufficient memory characteristics could not be obtained due to hydrogen generated during the process. Also, wiring 37M
It is difficult to newly provide a process for preventing moisture from the point that it cannot be processed in a reducing atmosphere (for example, H ₂ atmosphere) due to its low heat resistance and influence on the ferroelectric capacitor. There was also a problem.

[0004]

From the above, the present invention is
An object of the present invention is to provide a ferroelectric memory having a sufficient memory characteristic, which protects the ferroelectric capacitor from moisture generated during the manufacturing process, and a manufacturing method thereof. It is another object of the present invention to provide a ferroelectric memory and a method for manufacturing the same which can reduce the influence of hydrogen generated when forming a passivation film.

[0005]

As a result of intensive research to solve the above problems, the present inventors have found that the problems can be solved by the present invention described below, and have conceived the present invention. That is, the present invention <1> a semiconductor substrate, a ferroelectric capacitor formed on the semiconductor substrate, a first interlayer film including the ferroelectric capacitor, and a metal wiring penetrating the first interlayer film. And a moisture diffusion prevention film is formed on the first interlayer film. <2> A part of the metal wiring is patterned on the first interlayer film, and the water diffusion preventing film includes the patterned metal wiring in <1>. The ferroelectric memory described. <3> The water diffusion preventing film is Si ₃ N ₄ or SiO
The ferroelectric memory according to <1> or <2>, which is made of N. <4> The ferroelectric memory according to any one of <1> to <3>, wherein the water diffusion preventing film is formed by reactive sputtering. <5> The ferroelectric memory according to any one of <1> to <4>, wherein a hydrogen diffusion preventing film is formed on at least one of the upper and lower sides of the water diffusion preventing film. <6> A ferroelectric memory according to any one of <1> to <5>, wherein the ferroelectric memory is at least one of a planar type and a stack type. <7> A method for manufacturing the ferroelectric memory according to any one of <1> to <6>, which includes a step of forming a moisture diffusion preventing film on at least the first interlayer film. Is a method of manufacturing a ferroelectric memory

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION <Ferroelectric Memory> A ferroelectric memory according to the present invention comprises a semiconductor substrate, a ferroelectric capacitor formed on the semiconductor substrate, and a first interlayer film including the ferroelectric capacitor. And a metal wiring penetrating the first interlayer film, and a water diffusion preventing film is formed on the first interlayer film. The ferroelectric memory of the present invention will be described below with reference to the examples shown in FIGS.

The ferroelectric memory shown in FIG. 1 includes a semiconductor substrate 1, a first interlayer film 3 and a second interlayer film 5 formed thereon.
And the passivation film 6, and the first interlayer film 3
The water diffusion preventing film 4 is formed between the second interlayer film 5 and the second interlayer film 5. Further, a transistor 2 is provided on the semiconductor substrate 1, and a ferroelectric capacitor 7 is provided on the first interlayer film 3, and metal wirings 1M and 2M for electrically connecting them are provided in the contact holes 3a. 3b,
It is provided so as to pass through each interlayer film while passing through TH.

By providing the moisture diffusion preventing film 4 on the first interlayer film 3, the moisture generated during the manufacturing process such as the formation of the passivation film 6 and the like, the ferroelectric capacitor 7 provided on the first interlayer film 3 and the like. It is possible to effectively prevent the diffusion into the ferroelectric memory, resulting in a ferroelectric memory having sufficient memory characteristics. The moisture diffusion prevention film 4 is essential to be formed on the first interlayer film 3 in order to effectively prevent the ferroelectric capacitor 7 and the like from being affected by moisture, and in particular, it includes the patterned metal wiring 1M. Preferably, the thickness is 40 to 160.
nm is preferable, and 100 to 120 nm is more preferable. By setting 40 to 160 nm,
The ferroelectric capacitor 7 can be protected from moisture contained in the second interlayer film 5 and moisture generated during the manufacturing process.
The patterned metal wiring is a metal wiring spread in the plane direction.

The moisture diffusion preventive film 4 is made of S in consideration of corrosion resistance against moisture and the like and heat resistance in various manufacturing processes.
It is preferably composed of i ₃ N ₄ or SiON.
Further, the moisture diffusion preventing film 4 is preferably formed by reactive sputtering that does not require a hydrogen atmosphere in order to eliminate the influence of hydrogen and the like during manufacturing.

As other layers, elements, etc., conventionally known ones can be used. A Si substrate can be used as the semiconductor substrate 1, and materials such as SiO ₂ can be used for the first interlayer film 3 and the second interlayer film 5, respectively. The passivation film 6 is made of silicon nitride (Si ₃
N ₄ ) or the like can be used. As the transistor 2, for example, the source region 2a and the drain region 2 are used.
A MOS transistor composed of b and the gate electrode 2c can be used. The ferroelectric capacitor 7 includes, for example, a lower electrode 7a and an upper electrode 7b made of Pt or the like, and a ferroelectric thin film 7c made of PZT (lead zirconate titanate) or the like provided therebetween. Is preferred. Metal wiring 1M for electrically connecting the transistor 2 and the ferroelectric capacitor 7
It is preferable to use Al or the like as the material of 2M.

Further, as shown in FIG. 2, a hydrogen diffusion preventing film 8 may be formed on the water diffusion preventing film 4. By forming the hydrogen diffusion prevention film 8, the influence of hydrogen generated when forming the passivation film 6 can be reduced. The hydrogen diffusion prevention film 8 is preferably formed on at least one of the upper and lower sides of the water diffusion prevention film 4, and its thickness is preferably 50 to 200 nm.
More preferably, it is from 0 to 170 nm. 50-20
When the thickness is 0 nm, the ferroelectric capacitor can be protected from hydrogen generated during the manufacturing process. As a material of the hydrogen diffusion preventing film 8, tantalum oxide (Ta ₂ O ₅ ) or alumina (Al ₂ O ₃ ) is preferable, and tantalum oxide is more preferable from the viewpoint of workability. In addition, in FIG.
The same reference numerals as those in FIG. 2 indicate the same layers and members as those in FIG.

The ferroelectric memory of the present invention as described above is
At least one of the planar type and the stack type is preferable.

<Method for Manufacturing Ferroelectric Memory> The method for manufacturing a ferroelectric memory according to the present invention has at least a step of forming a water diffusion preventing film. The method for manufacturing the ferroelectric memory of the present invention will be described below by taking the ferroelectric memory shown in FIG. 1 as an example.

First, after providing the transistor 2 and the ferroelectric capacitor 7 on the Si substrate as the semiconductor substrate 1 by a known method, the first interlayer film 3 is formed by the CVD method or the like. After forming the first interlayer film 3, 700 to 800 ° C., 1
After heat treatment is performed for up to 2 hours to remove water in the first interlayer film 3, contact holes 3a and 3b for passing the metal wiring 1M for electrically connecting the transistor 2 and the ferroelectric capacitor 7 are formed. Form. Here, the atmosphere for performing the heat treatment is not particularly limited as long as it is not a reducing atmosphere, but from the viewpoint of interpolating oxygen vacancies in the ferroelectric film, the oxygen atmosphere is preferable. Next, the metal wiring 1M is formed. To form the metal wiring 1M, first, TiN of the adhesion layer is formed. Subsequently, Al of the wiring layer is continuously formed by a sputtering method, and then etched into a desired pattern.

Next, a water diffusion preventing film 4 having an effect of preventing the influence of water is formed by a reactive sputtering method (step of forming a water diffusion preventing film). By applying the reactive spattering method, the moisture diffusion preventing film can be formed in a state in which hydrogen and nitrogen, which have a strong influence on the characteristics of the ferroelectric capacitor, are significantly reduced as compared with the CVD method.

Here, the reactive sputtering is a plasma in which a rare gas is introduced into a film forming processing chamber in which a substrate and a sputtering target are arranged and a high negative voltage is applied to a sputtering electrode (cathode) to which the target is attached. A metal compound thin film is formed on the substrate while generating a discharge and sputtering the target with the rare gas plasma, and at the same time introducing an active gas ((N ₂ etc.)) to react the active gas with the target material. It is a technology.

As a condition for applying the reactive sputtering method, a nitrogen gas or the like as an active gas and an argon gas or the like as a rare gas are mixed and the ratio of the nitrogen is 50.
% Mixed gas atmosphere is preferable. As other conditions, the pressure is 0.04 to 0.15 Pa, R
It is preferable to set the F power source to 1 to 3 kW.

Next, the second interlayer film 5 is formed by the CVD method, and a contact hole TH is formed on the metal wiring 1M for connecting the peripheral circuit and the ferroelectric memory cell. Similar to the case of the metal wiring 1M, the metal wiring 2M is formed by the sputtering method and then formed into a desired pattern. Finally, the passivation film 6 (protective film) is C
It is formed by the VD method or the like.

As described above, a ferroelectric memory with little deterioration can be manufactured by only adding the step of forming the water diffusion preventing film to the conventional manufacturing steps. Conventional C
Si ₃ N ₄ film formation conditions by VD method (substrate temperature 400 ° C.,
SiH ₄ / N ₂ O or SiH ₄ / NH ₃ is 266-119
Conditions (for example, about 200 ° C.) on the metal wiring 1M at a low temperature compared to 7 Pa (2 to 9 Torr) and with a small amount of hydrogen and nitrogen which adversely affect the ferroelectric capacitor (for example,
It is possible to form a water diffusion preventing film such as a Si ₃ N ₄ film with Ar / N ₂ , 0.04 to 0.15 Pa), and the water diffusion preventing film prevents the water generated in the subsequent steps from forming a ferroelectric substance. The memory cell can be protected.

The ferroelectric memory shown in FIG. 2 can be manufactured by the same method as described above except that the step of forming the hydrogen diffusion preventing film is provided. Hereinafter, the step of forming the hydrogen diffusion preventing film will be described.

As described above, the hydrogen diffusion preventing film is formed on either the upper side or the lower side of the water diffusion preventing film, and the forming method thereof is the same as the method for forming the water diffusion preventing film.
It is preferable to apply the reactive sputtering method. By adding the step of forming the hydrogen diffusion preventing film, it is possible to suppress the influence of hydrogen and manufacture a ferroelectric memory with little deterioration.

As described above, if the step of forming the hydrogen diffusion preventing film is further provided in the step of forming the water diffusion preventing film, the ferroelectric capacitor is protected from the water generated during the process by the water diffusion preventing film. Further, the hydrogen diffusion preventing film can protect the passivation film from hydrogen generated in the step of forming (SiN film by CVD method) and the like.

The position where the water diffusion preventing film and the hydrogen diffusion preventing film are provided in the interlayer film is not limited to the position directly above the metal wiring. By forming a moisture diffusion prevention film,
In the subsequent processes, the effect of protecting the ferroelectric memory cell from moisture and from the hydrogen by the hydrogen diffusion preventing film can be obtained.

[0024]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto.

(Example 1) As described below,
The ferroelectric memory shown in FIG. 1 was produced. First, after providing the transistor 2 and the ferroelectric capacitor 7 on the Si substrate which is the semiconductor substrate 1, SiO _{2 is used} as the first interlayer film 3.
The film (4000A) was formed by the CVD method.

After heat treatment at 750 ° C. for 2 hours in an oxygen atmosphere to remove water in the SiO ₂ film, contact holes 3a and 3b for connecting the transistor 2 and the ferroelectric capacitor 7 are formed. . As the metal wiring 1M, first, TiN (thickness 100 nm) of the adhesion layer was formed, and subsequently Al (thickness 300 nm) of the wiring layer was continuously formed by the sputtering method, and then etched into a desired pattern. After that, S which is the water diffusion preventing film 4
Reactive sputtering equipment for i ₃ N ₄ film (manufactured by Shinko Seiki Co., Ltd.)
To have a thickness of 100 nm. As the sputtering conditions, a Si target was used, Ar and N ₂ were introduced into the chamber at a flow rate ratio of 1: 1, and the pressure was 1330.
Hold at mPa (10 mTorr) and RF power supply 2.
Power was supplied at 5 kW and plasma was generated in the chamber to form the Si ₃ N ₄ film.

A SiO ₂ film (having a thickness of 40) is used as the second interlayer film 5.
0 nm) was formed by a CVD method, and a contact hole TH was formed on the metal wiring 1M in order to connect the peripheral circuit and the ferroelectric memory cell. After forming Al (thickness 700 nm) / TiN (thickness 100 nm) as the metal wiring 2M by a sputtering method, it was formed into a desired pattern. Finally, a Si ₃ N ₄ film having a thickness of 850 nm was formed as the passivation film 6 by the CVD method to manufacture a ferroelectric memory.

(Embodiment 2) As described below,
The ferroelectric memory shown in FIG. 2 was produced. First, after forming a transistor and a ferroelectric capacitor on a Si substrate, a SiO ₂ film (thickness 400 nm) was formed as a first interlayer film by a CVD method.

After heat treatment was carried out at 750 ° C. for 2 hours in an oxygen atmosphere to remove water in the SiO ₂ film, contact holes 3a, 3b) for connecting to the transistor and the ferroelectric capacitor were formed. As the metal wiring 1M, first, TiN (thickness 100 nm) of the adhesion layer was formed, and subsequently Al (thickness 300 nm) of the wiring layer was continuously formed by the sputtering method, and then etched into a desired pattern. After that, Si that is the water diffusion preventing film 4
The N film was formed with a thickness of 100 nm by a reactive sputtering device (manufactured by Shinko Seiki Co., Ltd.). The sputtering conditions were the same as in Example 1.

Further, Ta ₂ is effective for preventing the influence of hydrogen.
Similarly, an O ₅ film (hydrogen diffusion prevention film 8) was formed with a thickness of 170 nm by using the reactive sputtering method. As the sputtering conditions, a Ta target was used, Ar and O ₂ were introduced into the chamber at a flow rate ratio of 1: 1 respectively, and the pressure was set to 1
It was kept at 330 mPa (10 mTorr) and 2.5 kW of electric power was supplied by an RF power source to generate plasma in the chamber to form a tantalum oxide film.

A SiO ₂ film (having a thickness of 40) is used as the second interlayer film 5.
0 nm) was formed by a CVD method, and a contact hole TH was formed on the metal wiring 1M in order to connect the peripheral circuit and the ferroelectric memory cell. After forming Al (thickness 700 nm) / TiN (thickness 100 nm) as the metal wiring 2M by a sputtering method, it was formed into a desired pattern. Finally, a SiN film having a thickness of 850 nm was formed as the passivation film 6 by the CVD method to manufacture a ferroelectric memory.

Comparative Example 1 A ferroelectric memory was manufactured in the same manner as in Example 1 except that the water diffusion preventing film was not formed.

When the memory characteristics of the ferroelectric memories manufactured in Examples 1 and 2 and Comparative Example 1 were evaluated by a Sawyer tower circuit, the memory characteristics (residual polarization amount) of Comparative Example 1 was 1.5 μC / cm ^2. However, Examples 1 and 2 could be improved to about 7.5 μC / cm ² .

[0034]

As described above, according to the present invention, it is possible to provide a ferroelectric memory which protects the ferroelectric capacitor from moisture generated during the manufacturing process and has sufficient memory characteristics. It is also possible to provide a ferroelectric memory that reduces the influence of hydrogen generated when forming the passivation film.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a ferroelectric memory of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the ferroelectric memory of the present invention.

FIG. 3 is a schematic sectional view showing an example of a conventional ferroelectric memory.

[Explanation of symbols]

1. Semiconductor substrate 2 ... Transistor 2a ... Source area 2b ... drain region 2c ... Gate electrode 3 ... First interlayer film 4 Moisture diffusion prevention film 5 ... Second interlayer film 6 ... passivation film 7 ... Ferroelectric capacitor 7a ... lower electrode 7b ... upper electrode 7c ... Ferroelectric thin film 1M, 2M ... Metal wiring 3a, 3b, TH ... Contact holes

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Claims (7)

[Claims] 1. A semiconductor substrate, a ferroelectric capacitor formed on the semiconductor substrate, a first interlayer film including the ferroelectric capacitor, and a metal wiring penetrating the first interlayer film. A ferroelectric memory, wherein a moisture diffusion preventing film is formed on the first interlayer film. 2. A part of the metal wiring is patterned on the first interlayer film, and the water diffusion preventing film includes the patterned metal wiring. 1. The ferroelectric memory described in 1. 3. The ferroelectric memory according to claim 1, wherein the water diffusion preventing film is made of Si ₃ N ₄ or SiON. 4. The moisture diffusion preventing film is formed by reactive sputtering.
Either of the ferroelectric memory. 5. The ferroelectric memory according to claim 1, wherein a hydrogen diffusion preventing film is formed on at least one of the upper and lower sides of the water diffusion preventing film. 6. A ferroelectric memory, wherein the ferroelectric memory according to claim 1 is at least one of a planar type and a stack type. 7. A method for manufacturing a ferroelectric memory according to claim 1, further comprising the step of forming a water diffusion preventing film on at least the first interlayer film. Method for manufacturing ferroelectric memory.