JP2001274348A - Semiconductor device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the SRO decomposition and capacitor's electric characteristic gradation and reduce the contact resistance between the upper electrode of a capacitor and a plug in a semiconductor device having a ruthenium- containing conductive film. SOLUTION: The semiconductor device comprises a ruthenium-containing conductive film 21 formed above a semiconductor substrate 11 and a protective film 22 formed on the ruthenium-containing conductive film 21, and the film 22 is composed of at least one of a double structure film composed of a silicon oxide and silicon nitride formed and laminated in this order and a titanium nitride film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a conductive film containing ruthenium, for example, a strontium-ruthenium oxide film (SR).
O film), ruthenium (Ru), and a method for manufacturing the same.

[0002]

2. Description of the Related Art (Ba, Sr) TiO ₃ (BST) film, SrTiO ₃ (S
A dielectric film such as a (TO) film, a Ta ₂ O ₅ film,
It is known that a capacitor having a structure sandwiched between Ru films has a high capacity and a low leakage current. This is suitable for the demand of a new generation memory device such as a gigabit DRAM.

[0003] It is known that SRO decomposes into ruthenium (Ru) and strontium oxide (SrO) during hydrogen annealing to improve transistor characteristics. In addition, MIM (met
al-insulator-metal) The leakage current of a capacitor generally increases after hydrogen annealing. In order to prevent such an increase in leakage current, it is preferable to prevent hydrogen permeation through the upper electrode, and a method of covering the upper electrode of the capacitor with a protective film has been adopted.

Alumina (Al ₂ O ₃ ) is suitable as a protective film for the upper electrode made of platinum or ruthenium. FIG. 1 shows a cross section of the structure of a conventional capacitor. In FIG. 1, a contact hole 2a connected to an impurity diffusion layer 3 in a semiconductor substrate 1 is formed in a first insulating film 2 formed on a silicon substrate 1. In the contact hole 2a, a tungsten plug 4a and a barrier metal 4b are provided.
Are sequentially embedded, and a capacitor 5 is formed on the barrier metal 4b and the first insulating film 2. The capacitor 5 includes a lower electrode 5a made of a first SRO film,
It is composed of a dielectric film 5b made of an ST film and an upper electrode 5c made of a second SRO film.

[0005] Such a capacitor 5 is covered with a second insulating film 6, and a plug 7 connected to the upper electrode 5 c is formed in a hole 6 a formed in the second insulating film 6. ing. The plug 7 has a multilayer structure in which titanium (Ti) 7a, titanium nitride (TiN) 7b, and tungsten (W) 7c are sequentially formed in a hole.

[0006]

In such a structure, hydrogen annealing can decompose the SRO and also adversely affect the BST film,
/ BST / SRO causes deterioration of the electrical characteristics of the capacitor. Therefore, it is conceivable to cover the second SRO film 7c with an alumina film, but it is difficult to finely pattern the alumina film in the actual structure of the gigabit DRAM.

Further, the titanium 7a of the plug 7 and S
When the RO upper electrode 5c reacts to form titanium oxide (TiO _x ), the contact resistance between the plug 7 and the upper electrode 5c becomes extremely high. An object of the present invention is to provide a semiconductor device and a method of manufacturing the same, which can prevent SRO decomposition and deterioration of electric characteristics of a capacitor, and can reduce contact resistance between an upper electrode of a capacitor and a plug.

[0008]

SUMMARY OF THE INVENTION The above-mentioned problem is solved by forming a ruthenium-containing conductive film formed above a semiconductor substrate on a conductive film.
Forming at least one of a two-layer structure film formed by stacking silicon oxide and silicon nitride and a titanium nitride film in order from the bottom as a protective film, and heating the semiconductor substrate in a reducing atmosphere after the formation of the protective film. And a method of manufacturing a semiconductor device having the above steps.

In the method of manufacturing a semiconductor device, a first insulating film is formed on the semiconductor substrate before the conductive film containing ruthenium is formed, and a first plug is formed in the first insulating film. Embedded, a capacitor lower electrode connected to the first plug is formed on the first insulating film, a capacitor dielectric film is formed on the capacitor lower electrode, and then the capacitor dielectric film is formed on the capacitor dielectric film. Forming the conductive film containing ruthenium as a capacitor upper electrode;
A second insulating film may be formed over the protective film, and a second plug electrically connected to the conductive film containing ruthenium may be embedded in the second insulating film. In this case, the capacitor dielectric film is made of BST, Ta ₂ O ₅ , STO or PZ.
It may be any of T. Further, the second plug may be made of a film containing tungsten or aluminum formed on the conductive film containing ruthenium via a titanium nitride film.

Another object of the present invention is to form a conductive film containing ruthenium formed above a semiconductor substrate and a silicon oxide and a silicon nitride formed on the conductive film containing ruthenium in order from the bottom. The problem is solved by a semiconductor device having a two-layered structure film and a protective film made of at least one of a titanium nitride film. In the above-described semiconductor device, it is preferable that the silicon oxide forming the two-layer structure film is thinner than 50 nm. Preferably, the titanium nitride film is thinner than 20 nm.

Next, the operation of the present invention will be described. According to the present invention, as the protective film formed on the conductive film containing ruthenium, at least one of a two-layer structure film made of silicon oxide and silicon nitride and a titanium nitride film is selected. According to such a protective film, even if the substrate is annealed in a reducing atmosphere, the conductive film containing ruthenium, for example, an SRO film is prevented from being decomposed and deteriorated.
The contact resistance between the conductive film and the plug formed thereon hardly increases, and the protective film does not peel off.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. SRO to be the upper electrode of the capacitor
As a protective film formed on the film, a sample was prepared for a plurality of materials and structures in order to investigate the fact that the structure of a gigabit DRAM was actually patterned by the CVD method, and the following experiment was performed. Was.

First, a structure in which a protective film is not formed on the SRO film is used as a first sample, and the SRO film is made of silicon nitride (SiN).
) Covered with SiN / SRO structure as the second sample
A third sample is an SiO ₂ / SRO structure in which an O film is covered with silicon oxide (SiO ₂ ), and a fourth sample is a SiN / SiO ₂ / SRO structure in which a silicon oxide film and a silicon nitride film are sequentially formed on the SRO film. The fifth sample was a TiN / SRO structure in which the SRO film was covered with a titanium nitride (TiN) film.

Then, the first to fifth samples are placed in a forming gas atmosphere at a substrate temperature of 400 ° C. for a heating time of 6 hours.
Annealing at 0 minutes resulted in the results shown in Table 1 and the following figures. In this case, a mixed gas of 3% hydrogen and nitrogen was used as the forming gas.

[0015]

[Table 1]

The first sample shown in FIG. 2 (a) is a SEM photograph showing a sample 1 of the section immediately after the formation of the SRO film, FIG. 2 (b), after annealing the sample 1 under the conditions described above It is a SEM photograph which shows a cross section.
As is clear from these SEM photographs, it was found that if the SRO film was annealed in a state where the protective film was not formed on the SRO film, the surface of the SRO film was roughened.

When the X-ray diffraction patterns of the SRO film before and after annealing were observed, as shown in Table 1, after annealing, the peak indicating the (121) plane of the SRO film had disappeared. Further, it was found that when annealing was performed with the SRO film exposed, the SRO film was decomposed and ruthenium was generated. Second Sample FIG. 3 is an SEM photograph showing a cross section of the SiN / SRO structure immediately after forming the second sample, that is, immediately after forming the SiN film on the SRO film.

Looking at the X-ray diffraction pattern of the second sample immediately after film formation, as shown in Table 1, the peak indicating the (121) plane of the SRO film did not exist from the beginning, and ruthenium was generated. I understood that. Like that SRO
When a SiN film is formed on the film, the SRO film is deteriorated only by the gas used for growing the SiN, ie, silane (SiH ₄ ).
It is considered that the SRO film is reduced by the gas and the ammonia (NH ₃ ) gas.

From the above, it can be seen that the SRO film has already been decomposed while the SiN film is being formed on the SRO film, and there is no point in annealing the second sample. The third sample view. 4 (a), SRO film silicon oxide by SEM photograph showing a third sample of the cross-section immediately covered with (SiO _2), FIG. 4 (b)
Is a SEM photograph showing a cross section of the third sample after annealing under the above conditions.

As is apparent from these photographs, it was found that the SRO film deteriorated after annealing the third sample. Looking at the X-ray diffraction patterns of the SRO film before and after annealing, as shown in Table 1, after annealing, SRO film
The peak indicating the (121) plane of the film was shifted. However, it was found that the SRO film did not undergo decomposition such that a ruthenium peak appeared.

In the third sample and the next fourth sample, the Si
The O ₂ film is formed by a CVD method using TEOS (tetraethoxysilane). Fourth Sample FIG. 5 (a) is an SEM photograph immediately after the fourth sample was prepared, and FIG. 5 (b) is a SEM photograph showing a cross section of the fourth sample after annealing under the above conditions. It is.

As is clear from the photographs, it was found that no change was observed in the SRO film after the fourth sample was annealed. Looking at the X-ray diffraction patterns of the SRO film before and after annealing, as shown in Table 1, before and after annealing, a peak indicating the (121) plane of the SRO film was present, and a ruthenium peak appeared. I knew it wasn't. Moreover, even if the contact resistance is measured, little change occurs before and after annealing.

Therefore, the protective film in which the SiO ₂ film is formed on the SRO film and the SiN film is formed on the SiO ₂ film is stable and is effective for preventing the SRO film from being deteriorated or decomposed. You can see that. In this case, it is preferable that the SiO ₂ film has a thickness of 50 nm or less. Fifth Sample FIG. 6 shows a fifth sample immediately after being formed by setting a substrate temperature within a range of 20 ° C. or higher and lower than 400 ° C. and forming a 20 nm-thick TiN film on the SRO film. It is a SEM photograph. When this fifth sample is annealed under the above conditions,
An SEM photograph as shown in FIG. 7A was obtained, and it was found that the TiN film was partially peeled. The SEM
When the photograph is reduced in magnification, the state becomes as shown in FIG. 7 (b), and the surface of the TiN film becomes uneven, so that the TiN film is easily peeled off.

On the other hand, the SRO film has a thickness of 5 nm.
When a TiN film was formed and annealed under the above conditions, an SEM photograph as shown in FIG. 8 was obtained, and no irregularities were generated on the surface of the TiN film. Also, Ti on the SRO film
When the thickness of the N film was smaller than 20 nm, no irregularities occurred even after annealing, and the contact resistance hardly changed.

The substrate temperature at the time of forming the TiN film is 400
C. or higher is not preferable because the SRO film reacts with the TiN film. For example, when the substrate temperature is set to 500 ° C. and a TiN film is formed on the SRO film, the SRO film loses oxygen,
Titanium oxide (TiO ₂ ) is formed between the O film and the TiN film. The titanium oxide causes a parasitic capacitance between the SRO film and the TiN film, and the total capacitance of the capacitor is reduced.

From the above, it can be seen that a TiN film thinner than 20 nm is effective as a protective film for the SRO film. According to the SEM photograph and the X-ray diffraction of the above-mentioned first to fifth samples, as the protective film at the time of annealing of the SRO film, a two-layer structure of a silicon oxide film and a silicon nitride film or a nitride film having a thickness less than 20 nm It has been found that the titanium film prevents the decomposition of the SRO film and reduces the contact resistance between the upper electrode and the tungsten plug. Therefore, such a protective film is effective for preventing deterioration of the SRO / BST / SRO capacitor.

Next, SiN / SiO _{2 is used} as a protective film for the SRO film.
The capacitor structure in the case of using the two-layer structure film or the titanium nitride film thinner than 20 nm will be described with reference to FIGS. In FIG. 9, the surface of the silicon substrate 11 has L
An impurity diffusion layer 13 is formed adjacent to the OCOS film 12. On the silicon substrate 11, SiO ₂ , PS
A first interlayer insulating film 14 of G, BPSG or the like is formed.
Is formed in the contact hole 15, a first plug 16 formed by stacking a barrier metal layer 16b on a tungsten layer 16a is formed. A second interlayer insulating film 17 is formed on the first plug 16 and the first interlayer insulating film 14, and the first plug 16
Is formed.

The first S
An RO film 19 is formed. Further, a BST 20 is formed on the first SRO film 19 and the second interlayer insulating film 17.
And a second SRO film 21 are sequentially formed, and these films are patterned into a desired shape. Second SRO film 2
On top of No. 1, a film having a thickness of 50 nm or less was formed using TEOS gas.
An SiO ₂ film 22a is formed, and a SiN film 22b is formed on the SiO ₂ film 22a using silane and ammonia. The two-layer structure of the SiO ₂ film 22a and the SiN film 22b functions as a protective film 22 of the second SRO film 21, and the protective film 22 can be easily finely patterned by photolithography.

The first SRO film 19 is used as a capacitor lower electrode, the BST film 20 is used as a capacitor dielectric film, and the second SRO film 21 is used as a capacitor upper electrode. Further, a third interlayer insulating film 23 is formed on the protective film 22. The third interlayer insulating film 23 and the protective film 22 are continuously patterned to form the second SRO
An opening 24 is formed on a part of the film 21.

In the opening 24, a titanium nitride film 25a is formed.
And a second plug 25 made of tungsten 25b. It is preferable that the titanium nitride film 25a is formed at a substrate temperature thinner than 20 nm and lower than 400 ° C. Even if the semiconductor device having the above structure is heated in a hydrogen-containing atmosphere, the SiN / SiO ₂ protective film 2
2, the deterioration of the film quality of the second SRO film 21 is prevented. The titanium nitride film 24 between the second plug 25 and the second SRO film 22 is thinner than 20 nm and
It is preferably formed as follows.

FIG. 10 shows an example in which a titanium nitride film is used as a protective film on the second SRO film 21 instead of the SiN / SiO ₂ film. 10, the same reference numerals as in FIG. 9 indicate the same elements. In FIG. 10, a protective film 30 made of titanium nitride is formed on the second SRO film 21. The titanium nitride protective film 30 is formed to a thickness of less than 20 nm, for example, 15 nm or less by sputtering under a substrate temperature condition lower than 400 ° C. The protective film 30 is easily patterned into a desired shape by a photolithography method, and after the patterning, the titanium nitride protective film 30 and the second interlayer insulating film 17 are covered with a third interlayer insulating film 23. .

An opening 24a reaching a part of the titanium nitride protective film 30 is formed in the third interlayer insulating film 23, and the titanium nitride 25a and the tungsten film 25 are formed in the opening 24a.
The second plug 25 made of b is embedded. Even if a semiconductor device having such a structure is heated in a hydrogen atmosphere,
The titanium nitride protective film 30 prevents the quality of the second SRO film 21 from deteriorating.

Note that SRO is used as the upper electrode of the capacitor.
It is not limited to a film and contains other ruthenium.
Alternatively, a conductive film may be used. Also connected to the upper electrode
As the plug, a film containing aluminum may be used.
As a dielectric film of a capacitor, BST ((Ba_xSr_1-x) T
iO_ThreeHowever, instead of 0 ≦ x ≦ 1, STO (SrTiO_Three),
Tantalum oxide (Ta_TwoO_Five), PZT (Pb (Zr_xTi _1-x)
O_ThreeWhere 0 ≦ x ≦ 1), PLZT ((Pb_yLa_1-y) (Zr
_xTi_1-x) O_ThreeWhere 0 ≦ x ≦ 1, 0 ≦ y ≦ 1)
Is also good. In addition, other than the above-mentioned materials,
Mina (Al_TwoO_Three) May be used. << Supplementary Note >> (1) Conduction containing ruthenium formed above the semiconductor substrate
Silicon oxide and silicon nitride in order from the bottom
At least one of a laminated two-layer structure film and a titanium nitride film
Forming one as a protective film, and after forming the protective film
Heating the semiconductor substrate in a reducing atmosphere.
Semiconductor device manufacturing method. (2) The silicon oxide constituting the two-layer structure film is 5
Semiconductor according to (1), characterized by being thinner than 0 nm.
Manufacturing method of body device. (3) The titanium nitride film has a substrate temperature lower than 400 ° C.
Characterized by being formed thinner than 20 nm in degree
The method for manufacturing a semiconductor device according to (1).

[0034]

As described above, according to the present invention, the SR
As a protective film formed on a conductive film containing ruthenium such as an O film, at least one of a two-layer structure film of silicon oxide and silicon nitride and a titanium nitride film was selected.
According to such a protective film, when the substrate is annealed in a reducing atmosphere, the deterioration of the conductive film containing ruthenium can be prevented, and the contact resistance between the conductive film and the plug formed thereon can be increased. Can be suppressed, and peeling of the protective film can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a conventional semiconductor device.

FIG. 2 is SEM photographs showing states before and after annealing of an SRO film used in a semiconductor device.

FIG. 3 is an SEM photograph showing a state in which an SRO film used for a semiconductor device is covered with a silicon nitride film.

FIG. 4 is an SEM photograph showing a state where an SRO film used for a semiconductor device is covered with a silicon oxide film.

FIG. 5 shows the SiN / Si of the semiconductor device according to the embodiment of the present invention.
It is a SEM photograph which shows the state before and after annealing the O2 / SRO structure.

FIG. 6 shows an SRO film having a thickness of 20 n used for a semiconductor device.
S before covering with SiN film
It is an EM photograph.

FIG. 7 shows an SRO film used for a semiconductor device having a film thickness of 20 n.
m after being covered with a SiN film and annealing.
It is an EM photograph.

FIG. 8 shows S after annealing titanium nitride / SRO in the semiconductor device according to the embodiment of the present invention.
It is an EM photograph.

FIG. 9 is a cross-sectional view illustrating a first semiconductor device according to an embodiment of the present invention.

FIG. 10 is a sectional view showing a second semiconductor device according to the embodiment of the present invention.

[Explanation of symbols]

11: silicon substrate (semiconductor substrate), 12: LOCO
S, 13: impurity diffusion layer, 14, 17, 23: interlayer insulating film, 15: contact hole, 16: first plug, 1
8: recess, 19: first SRO film, 20: BST film, 2
DESCRIPTION OF SYMBOLS 1 ... 2nd SRO film, 22 ... protective film, 22a ... silicon oxide film, 22b ... silicon nitride film, 24 ... opening, 25 ...
Plug, 25a: titanium nitride film, 25b: tungsten film, 30: protective film.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Eguchi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Office (72) Inventor Katsuhiko Hieda 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa F-term in Toshiba Yokohama Office (reference) 5F083 FR01 GA21 JA06 JA14 JA15 JA36 JA39 JA40 JA44 MA06 MA17 MA18 NA08 PR21 PR33

Claims (7)

[Claims] An at least one of a two-layer structure film and a titanium nitride film, in which silicon oxide and silicon nitride are sequentially stacked from above on a ruthenium-containing conductive film formed above a semiconductor substrate, is used as a protective film. A method of manufacturing a semiconductor device, comprising: a step of forming; and a step of heating the semiconductor substrate in a reducing atmosphere after forming the protective film. 2. A method according to claim 1, further comprising: forming a first insulating film on the semiconductor substrate before forming the ruthenium-containing conductive film; embedding a first plug in the first insulating film; Forming a capacitor lower electrode connected to the plug on the first insulating film, forming a capacitor dielectric film on the capacitor lower electrode, and then forming the ruthenium-containing conductive film on the capacitor dielectric film Is formed as a capacitor upper electrode. Further, a second insulating film is formed on the protective film, and a second plug electrically connected to the ruthenium-containing conductive film is formed on the second insulating film. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising: 3. A capacitor dielectric film according to claim 1, wherein
_{3. The} method according to claim 2, wherein the semiconductor device is one of O, Ta ₂ O ₅ , PZT, and PLZT. 4. The semiconductor device according to claim 2, wherein the second plug is formed of a film containing tungsten or aluminum formed on the conductive film containing ruthenium via a titanium nitride film. The manufacturing method of the semiconductor device described in the above. 5. A two-layer structure film formed on a conductive film containing ruthenium formed above a semiconductor substrate, and formed on the conductive film containing ruthenium and laminated with silicon oxide and silicon nitride in order from the bottom. And a protective film made of at least one of a titanium nitride film. 6. The semiconductor device according to claim 5, wherein said silicon oxide forming said two-layer structure film is thinner than 50 nm. 7. The semiconductor device according to claim 5, wherein said titanium nitride film is thinner than 20 nm.