JPH08330512A - Capacitor and its manufacturing method - Google Patents

Abstract

PURPOSE: To realize a capacitor with large capacitance and high capacitance accuracy by providing a film consisting of oxygen reducing substance on a diffusion layer provided on a semiconductor substrate. CONSTITUTION: Openings 3a and 3b are provided on a specified part on n<+> type diffusion layer 2 at an insulation film 3 on Si substrate 1 where the heavily doped n<+> type diffusion layer 2 is provided in the Si substrate and TiN/Ti film 4 in a specific shape is provided on the n<+> diffusion layer 2 at the part of the opening 3a with the edge part is extended over the insulation film 3 around the opening 3a. Then, Ta2 O5 film 5 and an electrode 6 are provided on it and a capacitor with the similar structure as that of MIS capacitor is formed by the n<+> type diffusion layer 2, the TiN/Ti film 4, Ta2 O5 film 5, and the electrode 6. On the other hand, an electrode 7 is provided as a take-out electrode on the n<+> type diffusion layer 2 at the part of the opening 3b of the insulation film 3, thus achieving a capacitor with large capacitance and high capacitance accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor and its manufacturing method, and is particularly suitable for application to a capacitor used in a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, capacitors used in bipolar semiconductor devices are MIS (Metal-Insulator-Se).
miconductor) structure, and the dielectric film is a depressurized C
A silicon nitride (Si ₃ N ₄ ) film formed by the VD method is used. An example thereof is shown in FIG.

As shown in FIG. 10, in this conventional MIS capacitor, an n ⁺ type diffusion layer 102 having a high impurity concentration is provided in a silicon (Si) substrate 101.
An insulating film 103 such as a silicon dioxide (SiO ₂ ) film is provided on the Si substrate 101. This insulating film 1
03, an opening 10 is formed at a predetermined portion on the n ⁺ type diffusion layer 102.
3a and 103b are provided. Of these, the opening 103
On the n ⁺ type diffusion layer 102 in the portion a, a Si ₃ N ₄ film 105 having a predetermined shape is formed with a natural oxide film 104 interposed between the edges of the Si ₃ N ₄ film 105 and the insulating film 103 around the opening 103a. It is provided. And this Si ₃ N ₄
An electrode 106 made of aluminum (Al) on the film 105
Is provided. These electrodes 106, Si ₃ N ₄ film 105, natural oxide film 104 and n ⁺ type diffusion layer 102 form a MIS capacitor. On the other hand, on the n ⁺ type diffusion layer 102 at the opening 103b, A
The electrode 107 composed of 1 is provided as a take-out electrode.

The natural oxide film 104 existing on the surface of the n ⁺ type diffusion layer 102 in the portion of the opening 103a is removed by washing with a low concentration hydrofluoric acid solution, but is reoxidized in the washing process. It has been thinned and remains thin.

While miniaturization of elements such as transistors is progressing, miniaturization of MIS capacitors has not progressed as compared with other elements because the capacitance thereof depends on the capacitor area. For this reason, the ratio of the MIS capacitor to the chip area is rapidly increasing, which is an obstacle to reducing the chip area. It is also possible to reduce the capacitor area by making the Si ₃ N ₄ film 105 thinner to increase the capacitance per unit area, but in this case, S
The influence of the natural oxide film 104 existing between the i ₃ N ₄ film 105 and the underlying n ⁺ type diffusion layer 102 and acting as a series capacitance is increased, and the effective capacitance of the MIS capacitor is lowered and the capacitance accuracy is deteriorated. Is a problem. In addition, the Si ₃ N ₄ film 10
5 itself is also a problem because the breakdown voltage is reduced due to the thinning.

In order to solve these problems, tantalum oxide (Ta) whose relative dielectric constant is about 4 times larger than that of the Si ₃ N ₄ film is used.
Recently, a technique of using a ₂ O ₅ ) film as a dielectric film of a MIS capacitor has attracted attention. The Ta ₂ O ₅ film was conventionally said to have poor electrical leak characteristics, but the characteristics have been improved to a practical level by annealing in an active oxygen atmosphere (active oxygen annealing). Thus T
FIG. 11 shows an example of an MIS capacitor using an a ₂ O ₅ film as a dielectric film. In FIG. 11, reference numeral 108 is Ta ₂
An O ₅ film is shown. The configuration of the other parts of this MIS capacitor is similar to that of the MIS capacitor shown in FIG.

[0007]

However, Ta ₂
The above MIS capacitor using the O ₅ film as the dielectric film has the following problems. That is, when the sputtering method, a CVD method such as by the Ta ₂ O ₅ film 108 during deposition and subsequent active oxygen annealing, in addition to the natural oxide film originally present on the surface of the n ⁺ -type diffusion layer 102, the n ⁺ -type diffusion An oxide film is newly formed by further oxidizing the surface of the layer 102. In FIG. 11, an oxide film composed of the native oxide film originally existing on the surface of the n ⁺ type diffusion layer 102 and the newly formed oxide film is denoted by reference numeral 109. The oxide film newly formed on the surface of the n ⁺ type diffusion layer 102 also works as a series capacitance, so that the effective capacitance of the MIS capacitor is lowered and the capacitance accuracy is deteriorated. The degree of influence is as follows in this MIS capacitor using the Ta ₂ O ₅ film as the dielectric film.
Since the Ta ₂ O ₅ film has a high relative dielectric constant, it is much larger and more serious than an MIS capacitor using a Si ₃ N ₄ film as a dielectric film.

Therefore, an object of the present invention is to provide a capacitor having a large capacitance and a high capacitance accuracy, and a method for manufacturing the same.

[0009]

In order to achieve the above object, a capacitor according to the present invention comprises a semiconductor substrate, a film made of an oxygen reducing substance and a film made of an oxygen reducing substance provided on the semiconductor substrate. It is characterized in that it has a film made of an oxidation resistant material provided thereon, an insulating film provided on the film made of an oxidation resistant material, and an electrode provided on the insulating film.

In a typical embodiment of the capacitor according to the present invention, a film made of an oxygen reducing substance is provided on the diffusion layer provided in the semiconductor substrate.

A method of manufacturing a capacitor according to the present invention is
A step of forming a film made of an oxygen reducing substance on a semiconductor substrate, a step of forming a film made of an oxidation resistant substance on a film made of an oxygen reducing substance, and an insulating film on the film made of an oxidation resistant substance. And a step of heat-treating the semiconductor substrate, and a step of forming an electrode on the insulating film.

In a typical embodiment of the method for manufacturing a capacitor according to the present invention, a film made of an oxygen reducing substance is formed on a diffusion layer formed in a semiconductor substrate.

In the method of manufacturing a capacitor according to the present invention, particularly when the insulating film is a tantalum oxide (Ta ₂ O ₅ ) film, the semiconductor substrate is preferably heat-treated in an active oxygen atmosphere.

In the present invention, examples of the oxygen reducing substance include titanium (Ti) and platinum silicide (PtS).
i _x ) or the like is used. Further, as the oxidation resistant material, for example, titanium nitride (TiN), tungsten (W), or the like is used.

In the present invention, the insulating film is preferably
It has a relative dielectric constant equal to or higher than that of the silicon nitride (Si ₃ N ₄ ) film. A tantalum oxide (Ta ₂ O ₅ ) film is preferably used as the insulating film.

The capacitor according to the present invention can be used in various types of semiconductor devices such as bipolar semiconductor devices.

[0017]

According to the present invention, after a film made of an oxygen reducing substance and a film made of an oxidation resistant substance are sequentially formed on a semiconductor substrate, the semiconductor substrate is heat-treated so that natural oxidation existing on the surface of the semiconductor substrate is caused. The film is completely removed by, for example, reaction with a film made of an oxygen reducing substance. Further, the film made of the oxidation resistant material on the film made of the oxygen reducing material prevents the surface of the semiconductor substrate from being oxidized during the deposition of the insulating film such as the tantalum oxide film and the heat treatment performed in the subsequent process. It

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a sectional view showing a capacitor according to a first embodiment of the present invention.

As shown in FIG. 1, in the capacitor according to the first embodiment, a Si substrate 1 is provided with an n ⁺ type diffusion layer 2 having a high impurity concentration. On the Si substrate 1,
An insulating film 3 such as a SiO ₂ film is provided.
The insulating film 3 is provided with openings 3a and 3b at predetermined portions on the n ⁺ type diffusion layer 2. Of these, a Ti film and a TiN film formed on the Ti film on the n ⁺ type diffusion layer 2 in the opening 3a
A TiN / Ti film 4 having a predetermined shape is formed so that its edge portion extends over the insulating film 3 around the opening 3a. Then, the Ta ₂ O ₅ film 5 as a dielectric film provided on the TiN / Ti film 4, the Ta ₂ O
_An electrode 6 made of, for example, Al is provided on the film 5. In this case, the n ⁺ type diffusion layer 2, the TiN / Ti film 4, the T
The a ₂ O ₅ film 5 and the electrode 6 form a capacitor having a structure similar to that of the MIS capacitor. On the other hand, on the n ⁺ type diffusion layer 2 in the opening 3b portion of the insulating film 3,
For example, an electrode 7 made of Al is provided as a lead electrode.

2 to 5 are sectional views showing a method of manufacturing the capacitor according to the first embodiment in the order of steps.

In the method of manufacturing the capacitor according to the first embodiment, first, as shown in FIG. 2, an n-type impurity such as arsenic (As) or phosphorus (P) is ion-implanted into a predetermined portion of the Si substrate 1. The n ⁺ -type diffusion layer 2 is formed by doping with a thermal diffusion method or the like.

Next, an insulating film 3 such as a SiO ₂ film is formed on the Si substrate 1 by a thermal oxidation method or a CVD method.

Next, a resist pattern (not shown) having a predetermined shape is formed on the insulating film 3 by lithography, and then the insulating film 3 is etched by using this resist pattern as a mask, whereby the n ⁺ -type in the capacitor formation region is formed. The opening 3a is formed on the diffusion layer 2. This opening 3a
After the formation of n, the n ⁺ exposed on the opening 3a is formed.
A natural oxide film 8 is formed on the surface of the mold diffusion layer 2.

Next, after removing the resist pattern used for forming the opening 3a, cleaning is performed using, for example, a low-concentration hydrofluoric acid solution, so that n ⁺ in the portion of the opening 3a is removed.
The natural oxide film 8 formed on the surface of the mold diffusion layer 2 is removed.

Next, as shown in FIG. 3, a Ti film and a TiN film are sequentially deposited on the entire surface by a sputtering method or a CVD method to form a TiN / Ti film 4. In this case, since the natural oxide film 8 exists thinly on the surface of the n ⁺ type diffusion layer 2 in the opening 3a even after the cleaning is performed using the low concentration hydrofluoric acid solution as described above. At the opening 3a, T is formed on the thin native oxide film 8.
The iN / Ti film 4 is formed.

Next, a Ta ₂ O ₅ film 5 is deposited on the entire surface by sputtering or CVD. In this case, T
The TiN film in the iN / Ti film 4 prevents the surface of the underlying n ⁺ type diffusion layer 2 from being oxidized when the Ta ₂ O ₅ film 5 is deposited.

Next, ozone (O ₃₎ O ₃ generated by the generator, it ultraviolet irradiation O ₃ was irradiated with ultraviolet rays, an annealing in an active oxygen atmosphere such as oxygen plasma, the the Ta ₂ O ₅ film 5 Suppresses electrical leakage.

During the active oxygen annealing, the natural oxide film 8 existing on the surface of the n ⁺ type diffusion layer 2 in the opening 3a reacts with the Ti film in the TiN / Ti film 4 which is in contact with the native oxide film 8. Completely removed. Also, TiN
The TiN film in the / Ti film 4 prevents the surface of the underlying n ⁺ type diffusion layer 2 from being oxidized during this active oxygen annealing. As a result, as shown in FIG.
The i film 4 makes good contact with the underlying n ⁺ type diffusion layer 2.

Next, after forming a lithographic resist pattern (not shown) of a predetermined shape on the Ta ₂ O ₅ film 5, Ta ₂ O using the resist pattern as a mask
_The film 5 and the TiN / Ti film 4 are etched by a reactive ion etching (RIE) method or the like. As a result, as shown in FIG. 5, the Ta ₂ O ₅ film 5 and the TiN / Ti film 4 are patterned into a predetermined shape. Next, after removing the resist pattern used for this patterning, a resist pattern (not shown) having a predetermined shape is formed on the surface of the substrate by lithography, and the insulating film 3 is etched by using this resist pattern as a mask. ^The opening 3b is formed on a predetermined portion of the ⁺ type diffusion layer 2.

Next, after removing the resist pattern used for forming the opening 3b, an Al film is deposited on the entire surface by a sputtering method or a vacuum evaporation method, and this Al film is RIE.
Etching is performed by a method or the like to pattern into a predetermined shape. As a result, the electrodes 6 and 7 are formed as shown in FIG.

As described above, the intended capacitor is manufactured.

As described above, according to the capacitor of the first embodiment, since no oxide film such as a natural oxide film is present on the surface of the n ⁺ type diffusion layer 2, the capacitance decrease due to this oxide film and the capacitance accuracy are reduced. It is possible to prevent the deterioration. As a result, it is possible to realize a capacitor having a large capacity and a high capacity accuracy.

FIG. 6 shows a capacitor according to the second embodiment of the present invention.

As shown in FIG. 6, in the capacitor according to the second embodiment, the PtSi _x film 9 is provided on the n ⁺ type diffusion layer 2 in the opening 3a portion of the insulating film 3. A TiN film 1 having a predetermined shape is formed on the PtSi _x film 9.
0 is provided such that its edge portion extends over the insulating film 3 around the opening 3a. And this TiN film 1
A Ta ₂ O ₅ film 5 as a dielectric film and an electrode 6 are provided on the substrate 0. The structure of the other parts of the capacitor according to the second embodiment is similar to that of the capacitor according to the first embodiment.

Next, a method of manufacturing the capacitor according to the second embodiment will be described.

In the method of manufacturing the capacitor according to the second embodiment, first, the same steps as those in the method of manufacturing the capacitor according to the first embodiment are performed to form the n ⁺ -type diffusion layer 2 in the opening 3a of the insulating film 3. The cleaning process for removing the natural oxide film 8 on the surface is completed.

Next, as shown in FIG. 7, a Pt film 11 is deposited on the entire surface by a sputtering method, a vacuum evaporation method or the like.

Next, for example, annealing is performed at a temperature of about 600 ° C. in a nitrogen (N ₂ ) atmosphere. As a result, as shown in FIG. 8, a portion of the Pt film 11 in the opening 3 a of the insulating film 3 which is in contact with the n ⁺ type diffusion layer 2 is silicidized to become a PtSi _x film 9. In the process of silicidation, the native oxide film 8 existing on the surface of the n ⁺ type diffusion layer 2 in the opening 3a is completely removed, and the PtSi _x film 9 is formed on the n ⁺ type diffusion layer 2.
Will be in good contact.

Next, the Pt film 11 is removed by etching with, for example, aqua regia. At this time, since the PtSi _x film 9 is not etched by aqua regia, remain intact.

Next, as shown in FIG. 9, a TiN film 10 is deposited on the entire surface by a sputtering method, a CVD method or the like, and then the sputtering method or the CVD method is performed on the TiN film 10.
A Ta ₂ O ₅ film 5 is deposited by a method or the like. This Ta ₂
During the deposition of the O ₅ film 5, the TiN film 10 prevents the surface of the n ⁺ type diffusion layer 2 and the PtSi _x film 9 from being oxidized.

Next, the method of manufacturing the capacitor according to the first embodiment, O ₃ generator in the generated O _3, it ultraviolet irradiation O ₃ was irradiated with ultraviolet rays, in an active oxygen atmosphere such as oxygen plasma Annealed, Ta ₂ O
₅ Electric leakage of the film 5 is suppressed. At the time of this active oxygen annealing, the TiN film 10 prevents the surface of the n ⁺ type diffusion layer 2 and the PtSi _x film 9 from being oxidized.

Thereafter, similar to the method of manufacturing the capacitor according to the first embodiment, the Ta ₂ O ₅ film 5 and the TiN film 10 are patterned, the openings 3b are formed in the insulating film 3, and the electrodes 6 and 7 are formed.
The target capacitor is manufactured through steps such as formation of.

In the capacitor according to the second embodiment, as in the capacitor according to the first embodiment, since no oxide film such as a natural oxide film is present on the surface of the n ⁺ type diffusion layer 2, the capacitance due to this oxide film is present. It is possible to prevent the deterioration and the deterioration of the capacitance accuracy, which makes it possible to realize a capacitor having a large capacitance and a high capacitance accuracy.

The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, the structures, materials, numerical values, etc. used in the above-described first and second embodiments are merely examples, and different structures, materials, numerical values, etc. may be used as necessary. Good.

[0047]

As described above, according to the present invention, a film made of an oxygen reducing substance and a film made of an oxidation resistant substance are provided on a semiconductor substrate, and insulation is performed on the film made of the oxidation resistant substance. By providing the film, it is possible to realize a capacitor having a large capacitance and a high capacitance accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view showing a capacitor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the method of manufacturing a capacitor according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the method of manufacturing the capacitor according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining the method of manufacturing the capacitor according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining the method of manufacturing the capacitor according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a capacitor according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating the method of manufacturing a capacitor according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view for explaining the method of manufacturing the capacitor according to the second embodiment of the present invention.

FIG. 9 is a cross sectional view for illustrating the method for manufacturing the capacitor according to the second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing an example of a conventional MIS capacitor.

FIG. 11 is a cross-sectional view showing another example of a conventional MIS capacitor.

[Explanation of symbols]

1 Si substrate 2 n ⁺ type diffusion layer 3 insulating film 3a, 3b opening 4 TiN / Ti film 5 Ta ₂ O ₅ film 6, 7 electrode 8 natural oxide film 9 PtSi _x film 10 TiN film 11 Pt film

Claims (17)

[Claims] 1. A semiconductor substrate, a film made of an oxygen reducing substance provided on the semiconductor substrate, a film made of an oxidation resistant substance provided on the film made of the oxygen reducing substance, and the acid resistant substance. A capacitor having an insulating film provided on a film made of a chemical substance and an electrode provided on the insulating film. 2. The capacitor according to claim 1, wherein a film made of the oxygen reducing substance is provided on a diffusion layer provided in the semiconductor substrate. 3. The capacitor according to claim 1, wherein the oxygen reducing substance is titanium. 4. The capacitor according to claim 1, wherein the oxygen reducing substance is platinum silicide. 5. The capacitor according to claim 1, wherein the oxidation resistant material is titanium nitride. 6. The capacitor according to claim 1, wherein the oxidation resistant material is tungsten. 7. The capacitor according to claim 1, wherein the insulating film has a relative dielectric constant equal to or higher than that of a silicon nitride film. 8. The capacitor according to claim 1, wherein the insulating film is a tantalum oxide film. 9. A step of forming a film made of an oxygen reducing substance on a semiconductor substrate, a step of forming a film made of an oxidation resistant substance on the film made of the oxygen reducing substance, and the oxidation resistant substance. A method of manufacturing a capacitor, comprising: a step of forming an insulating film on the film made of; a step of heat-treating the semiconductor substrate; and a step of forming an electrode on the insulating film. 10. The method of manufacturing a capacitor according to claim 9, wherein a film made of the oxygen reducing substance is formed on the diffusion layer formed in the semiconductor substrate. 11. The method of manufacturing a capacitor according to claim 9, wherein the oxygen reducing substance is titanium. 12. The method of manufacturing a capacitor according to claim 9, wherein the oxygen reducing substance is platinum silicide. 13. The method of manufacturing a capacitor according to claim 9, wherein the oxidation resistant material is titanium nitride. 14. The method of manufacturing a capacitor according to claim 9, wherein the oxidation resistant material is tungsten. 15. The method of manufacturing a capacitor according to claim 9, wherein the insulating film has a relative dielectric constant equal to or higher than that of a silicon nitride film. 16. The method of manufacturing a capacitor according to claim 9, wherein the insulating film is a tantalum oxide film. 17. The semiconductor substrate is heat-treated in an active oxygen atmosphere.
6. The method for manufacturing a capacitor according to 6.