JP4622213B2 - Semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, with the miniaturization of a semiconductor device, the area of the information storage capacitive element has decreased, and the absolute value of the capacitance tends to decrease. For example, in the case of a parallel plate electrode structure, the capacitance C is
C = ε · S / d
Determined by Here, ε is the dielectric constant of the dielectric, S is the area of the capacitive electrode (hereinafter also referred to as electrode), and d is the thickness of the dielectric (distance between the electrodes). In order to ensure the capacitance without increasing the area S of the electrode used for the information storage capacitive element, it is necessary to use a dielectric having a high dielectric constant ε or to reduce the thickness d of the dielectric. is necessary. Currently, the film thickness has been reduced to about 10 nm, and in highly integrated memories of 64 Mbits or more, the capacity insulation film is reaching the limit. development is underway, tantalum oxide (Ta ₂ O ₅₎ is 64M~256M bits, in the DRAM of 1G bits, for example, barium strontium titanate, as described in JP-a-9-186299 (Ba _x Sr _y The use of Ti _s O _t (BST), etc. is being studied. As the non-volatile memory, as well as lead zirconate titanate, as described in _{JP-A-10-189881 (Pb x Zr y Ti s} O t: PZT) Using the like have been studied.
[0003]
Since it is known that oxides such as BST and PZT do not exhibit good characteristics unless subjected to high temperature treatment, high temperature treatment of about 600 ° C. or higher is required in the production process. Therefore, it is necessary to use a material that does not easily oxidize even at a high temperature as a capacitor electrode material that contacts an oxide such as BST or PZT. This is because when the capacitor electrode is a material that is easily oxidized, an oxidation-reduction reaction occurs at the contact interface between the electrode and the oxide at a high temperature, and the characteristics of the oxide deteriorate.
[0004]
Against this background, noble metal materials such as ruthenium (Ru) and platinum (Pt) and conductive oxides such as ruthenium oxide (Ru _x O _y ) are being studied as capacitive electrode materials that are difficult to oxidize. . However, when these capacitor electrode materials are in direct contact with silicon (Si), silicon (Si) diffuses inside the capacitor electrode, so a barrier film is required to prevent diffusion under the capacitor lower electrode. It becomes. As this barrier film, a conductive film made of titanium nitride (Ti _x N _y ) or the like is used as described in, for example, Japanese Patent Laid-Open No. 9-186299.
[0005]
[Problems to be solved by the invention]
As mentioned above, it is known that oxides such as BST and PZT do not exhibit good characteristics unless they are subjected to high-temperature treatment, but for use in DRAMs of 1 Gbit or more, high-temperature treatment is performed in an oxygen atmosphere. It has been found that sufficient properties are not exhibited unless it is received inside. Therefore, a high-temperature treatment at about 600 ° C. or higher in an oxygen atmosphere is newly required in the manufacturing process. However, in the structure using the conductive film made of titanium nitride (Ti _x N _y ) or the like as the barrier film as described above, for example, Japanese Patent Application Laid-Open No. 10-189881 and Journal of Materials Research Society Bulletin As can be seen from the contents described on pages 55 to 58 of Vol. 21 No. 6 (issued in June 1996), oxygen atoms in BST, PZT, etc. and oxygen atoms in the oxygen atmosphere are about There is a problem in that the high-temperature treatment at 600 ° C. or more passes through the capacitor lower electrode and reaches the barrier film, and oxidizes the barrier film to cause poor conduction.
[0006]
Also, as a problem close to this, when the gate electrode has a structure in which a barrier film is sandwiched between polycrystalline silicon and a metal film (a so-called polymetal gate structure for realizing low resistance) There is a problem that the barrier film is oxidized during the heat treatment for improving the characteristics of the gate insulating film.
[0007]
An object of the present invention is to provide a highly reliable semiconductor device, to provide a semiconductor device with a high yield, to provide a semiconductor device having a capacitor element structure that is less likely to cause poor conduction, and to a gate structure that is less likely to cause oxidation It is to solve at least one of the problems such as providing a semiconductor device having the above.
[0008]
[Means for Solving the Problems]
The inventors have conducted intensive research to solve the above problems, and that the oxidation of the barrier film, which causes poor conduction, proceeds by the diffusion of oxygen atoms within the crystal grain boundaries and crystal grains of the barrier film. I found it. Therefore, it has been found that in order to prevent poor conduction, it is sufficient to suppress the grain boundary diffusion and intragranular diffusion of oxygen atoms in the barrier film. The inventors have found that by adding an additive element for narrowing the oxygen diffusion path in the barrier film to the barrier film, the grain boundary diffusion and intragranular diffusion of oxygen atoms in the barrier film can be suppressed.
[0012]
An object of the present invention includes, for example, a semiconductor substrate, a gate insulating film formed on one main surface side of the semiconductor substrate, and a gate electrode formed on the gate insulating film, wherein the gate electrode is and a polycrystalline silicon film formed in contact with the gate insulating film, main constituent material wherein is formed in contact with the polycrystalline silicon film is titanium nitride, is selected from cobalt, nickel, the group consisting of ruthenium A barrier film containing one kind of additive element; and a metal film formed so as to be in contact with the barrier film, wherein the content of the additive element with respect to the main constituent material of the barrier film is 0.05 at.% Or more This can be solved by a semiconductor device of 18 at.
[0013]
According to this configuration, it is possible to provide a semiconductor device having a gate structure that hardly causes oxidation.
[0015]
Here, the main constituent metal element of the conductive film means a metal element contained most in the conductive film. The main constituent material means a material that is contained most.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the examples shown in the drawings.
First, FIG. 1 shows a cross-sectional structure of a DRAM (Dynamic Random Access Memory) memory cell according to the first embodiment of the present invention. This is a cross-sectional view taken along AB or CD in the example of the planar layout shown in FIG. As shown in FIG. 1, the semiconductor device of this embodiment includes a MOS (Metal Oxide Semiconductor) type transistor 2 formed in an active region on the main surface of a silicon substrate 1, and an information storage capacitor disposed thereon. An element 3 is provided. The insulating film 4 is a film for element isolation.
[0017]
The MOS transistor 2 of the memory cell includes a gate electrode 5, a gate insulating film 6, and a diffusion layer 7. The gate insulating film 6 is made of, for example, a silicon oxide film, a silicon nitride film, a ferroelectric film, or a laminated structure thereof. The gate electrode 5 is made of, for example, a polycrystalline silicon film, a metal thin film, a metal silicide film, or a laminated structure thereof. An insulating film 9 made of, for example, a silicon oxide film is formed on the top and side walls of the gate electrode 5. A bit line 11 is connected to one diffusion layer 7 of the memory cell selection MOS transistor via a plug 10. Over the entire upper surface of the MOS transistor, for example, a BPSG (Boron-doped Phospho Silicate Glass) film, SOG (Spin On Glass) film, or a silicon oxide film or a nitride film formed by chemical vapor deposition or sputtering is used. A film 12 is formed.
[0018]
An information storage capacitive element 3 is formed on the insulating film 12 covering the MOS transistor. The information storage capacitive element 3 is formed on the other diffusion layer 8 of the memory cell selection MOS transistor, for example, from polycrystalline silicon. Are connected through a plug 13. The information storage capacitor element 3 has a structure in which a conductive barrier film 14, a capacitor lower electrode 15, a high dielectric constant or ferroelectric oxide film 16, and a capacitor upper electrode 17 are stacked in order from the lower layer. Yes. The information storage capacitive element 23 is covered with an insulating film 1518.
[0019]
Here, the barrier film 14 contains at least one kind of additive element, and at least one of the additive elements has an action of narrowing the diffusion path of oxygen atoms in the barrier film 14. Specifically, when the main constituent material of the barrier film 14 is titanium nitride (Ti _x N _y ), the barrier film 14 includes silicon (Si), cobalt (Co), nickel (Ni), ruthenium (Ru). 1 type of additional elements selected from the group consisting of: When the main constituent material of the barrier film 14 is tungsten nitride (W _x N _y ), the barrier film 14 contains molybdenum (Mo) as an additive element. When the main constituent material of the barrier film 14 is ruthenium (Ru), the barrier film 14 has one kind of additive element selected from the group consisting of silicon (Si), cobalt (Co), and nickel (Ni). Containing.
[0020]
Hereinafter, the effect of the present embodiment will be described.
When a conventional semiconductor device is exposed to a high temperature of about 600 ° C. or higher in an oxygen atmosphere when forming the oxide film 16 having a high dielectric constant or ferroelectricity or during the subsequent heat treatment, the barrier film It has been experimentally clarified that oxidation of 14 proceeds and a conduction failure occurs. The inventors have found that the oxidation of the barrier film 14 proceeds by oxygen atoms diffusing in the crystal grain boundaries and in the crystal grains of the barrier film 14. Thus, the inventors have found that conduction failure due to oxidation is prevented by suppressing oxygen grain boundary diffusion and intragranular diffusion. The inventors have also found that the addition of an additive element that narrows the diffusion path of oxygen atoms in the barrier film to the barrier film can suppress the grain boundary diffusion and intragranular diffusion of oxygen atoms in the barrier film. In this embodiment, the barrier film 14 contains at least one kind of additive element, and at least one of the additive elements contains an additive element that narrows the diffusion path of oxygen atoms. Therefore, the grain boundary diffusion and intragranular diffusion of oxygen atoms in the barrier film 14 are suppressed, and poor conduction is prevented. In order to explain this in detail, the results of calculating the diffusion coefficient of oxygen atoms at the grain boundaries by molecular dynamics simulation are shown below. Molecular dynamics simulation works for each atom through the interatomic potential, as described, for example, on pages 4864 to 4878 of Journal of Applied Physics, Volume 54 (published in 1983). In this method, the position of each atom at each time is calculated by calculating a force and solving Newton's equation of motion based on this force. The method of calculating the diffusion coefficient by molecular dynamics simulation is described, for example, from page 5363 to page 5371 of Volume 29 (issued in 1984) of Physical Review B. Here, description will be given using an example in which the temperature is set to 1000 K and the diffusion coefficient of oxygen atoms in the crystal grain boundaries and in the crystal grains is calculated. The effects described here can be explained in the same manner even if the simulation conditions are changed.
[0021]
In this example, the following effects could be clarified by calculating the interaction between different elements by incorporating charge transfer into the above molecular dynamics method. First, the results of analyzing the influence of the additive element on the diffusion coefficient of oxygen atoms at the grain boundaries in the case where the main constituent material of the barrier film is titanium nitride (Ti _x N _y ) will be described. 3 and 4 show the results of analyzing the concentration dependence of the diffusion coefficient when silicon (Si), cobalt (Co), nickel (Ni), and ruthenium (Ru) are added as additive elements. Here, D _GB0 represents the grain boundary diffusion coefficient when no additive element is contained. _DIN0 represents the intragranular diffusion coefficient when no additive element is contained. As can be seen from FIG. 3, when the additive concentration of silicon (Si), cobalt (Co), nickel (Ni), and ruthenium (Ru) is 0.05 at.% Or more, the effect of suppressing diffusion becomes significant. Further, as can be seen from FIG. 4, when the added concentration is about 18 at. This is because if the additive element is too much, the crystal structure of titanium nitride (Ti _x N _y ), which is the main constituent material, is disturbed, so that oxygen is likely to diffuse.
[0022]
Next, the result of analyzing the influence of the additive element on the diffusion coefficient of oxygen atoms at the crystal grain boundary in the case where the main constituent material of the barrier film is tungsten nitride (W _x N _y ) will be described. 5 and 6 show the results of analyzing the concentration dependence of the diffusion coefficient when molybdenum (Mo) is added as an additive element. Here, D _GB0 represents the grain boundary diffusion coefficient when no additive element is contained. _DIN0 represents the intragranular diffusion coefficient when no additive element is contained. As can be seen from FIG. 5, when the additive concentration of molybdenum (Mo) is 0.05 at.% Or more, the effect of suppressing diffusion becomes significant. Further, as can be seen from FIG. 6, when the additive concentration is about 18 at.% Or more, the effect of suppressing diffusion is weakened. This is because when the additive element is too much, the crystal structure of tungsten nitride (W _x N _y ), which is the main constituent material, is disturbed, so that oxygen easily diffuses.
[0023]
Next, the results of analyzing the influence of the additive element on the diffusion coefficient of oxygen atoms at the grain boundaries when the main constituent material of the barrier film is ruthenium (Ru) will be described. 7 and 8 show the results of analyzing the concentration dependence of the diffusion coefficient when silicon (Si), cobalt (Co), and nickel (Ni) are added as additive elements. Here, D _GB0 represents the grain boundary diffusion coefficient when no additive element is contained. _DIN0 represents the intragranular diffusion coefficient when no additive element is contained. As can be seen from FIG. 7, when the additive concentration of silicon (Si), cobalt (Co), and nickel (Ni) is 0.05 at.% Or more, the effect of suppressing diffusion becomes significant. Further, as can be seen from FIG. 8, when the added concentration is about 18 at.% Or more, the effect of suppressing diffusion is weakened. This is because if the additive element is too much, the crystal structure of ruthenium (Ru), which is the main constituent material, is disturbed, so that oxygen easily diffuses. Therefore, the addition concentration is preferably 0.05 at.
[0024]
Next, FIG. 9 shows a cross-sectional structure of a DRAM (Dynamic Random Access Memory) memory cell according to the second embodiment of the present invention. This is also a cross-sectional view taken along AB or CD in the example of the planar layout shown in FIG. The difference of the second embodiment from the first embodiment is that another conductive film 19 is formed below the barrier film 14. In particular, when the main constituent material of the capacitor lower electrode 15 is ruthenium (Ru) and the main constituent material of the barrier film 14 is titanium nitride (Ti _x N _y ), ruthenium (Ru) and titanium nitride (Ti _x In order to stabilize the crystal structure of N _y ), it is preferable to use titanium (Ti) as the conductive film 19. By stabilizing the crystal structure of ruthenium (Ru) and titanium nitride (Ti _x N _y ), the crystal structure of the capacitive insulating film 16 becomes stable, and the device characteristics are improved. Further, another layer or more may exist between the conductive film 14a and the plug 13.
[0025]
Next, FIG. 10 shows a cross-sectional structure of a DRAM (Dynamic Random Access Memory) memory cell according to a third embodiment of the present invention. This is also a cross-sectional view taken along AB or CD in the example of the planar layout shown in FIG. The difference of the third embodiment from the first embodiment is that the conductive film 20 is formed in contact with the plug 13. In particular, when the main constituent material of the plug 13 is tungsten nitride (W _x N _y ), for example, titanium nitride (Ti _x N _y ) is used as the main constituent material in order to improve adhesion to the insulating film 12. The conductive film 20 is preferably formed. In this case, one or more other films may exist between the conductive film 20 and the insulating film 12.
[0026]
Next, FIG. 11 shows a sectional structure of a DRAM (Dynamic Random Access Memory) memory cell according to the fourth embodiment of the present invention. This is also a cross-sectional view taken along AB or CD in the example of the planar layout shown in FIG. The main difference of the fourth embodiment from the first embodiment is that the gate electrode 5 has a three-layer structure (that is, a polymetal gate structure) of a metal film 5a , a barrier film 5b , and a polycrystalline silicon film 5c. It is that. Here, when the main constituent material of the barrier film 5b is titanium nitride (TixNy), the barrier film 5b is made of silicon (Si), cobalt (Co), nickel (Ni), ruthenium (Ru). One selected additive element is contained. When the main constituent material of the barrier film 5b is tungsten nitride (WxNy), the barrier film 5b contains molybdenum (Mo) as an additive element. When the main constituent material of the barrier film 5b is ruthenium (Ru), the barrier film 5b includes one kind of additive element selected from the group consisting of silicon (Si), cobalt (Co), and nickel (Ni). Containing. As a result, an effect that the barrier film 5b is hardly oxidized is obtained. In many cases, tungsten (W) or molybdenum (Mo) having a high melting point and a low resistance is used for the metal film 5a . In this case, a material composed of the same kind of element, that is, molybdenum (Mo) is added. It is preferable to use tungsten nitride (WxNy) contained as an element as the barrier film 5b . When ruthenium (Ru), which is resistant to oxidation, is used as the metal film 5a , it is selected from the group consisting of the same kind of element, that is, ruthenium (Ru) consisting of silicon (Si), cobalt (Co), and nickel (Ni). It is preferable to use a material containing one kind of additive element as the barrier film 5b .
[0027]
In these embodiments, the case where the information storage capacitive element 3 and the silicon substrate 1 are connected via the plug 13 has been described. However, the information storage capacitive element 3 and the silicon substrate 1 are in direct contact with each other. It may be.
[0028]
In the above embodiment, when the main constituent material of the capacitor lower electrode 15 is ruthenium (Ru), the capacitor lower electrode 15 is selected from the group consisting of silicon (Si), cobalt (Co), and nickel (Ni). When one kind of additive element is contained, oxygen does not easily pass through the capacitor lower electrode 15, and as a result, the effect that the oxidation of the barrier film 14 is more easily suppressed can be obtained. In the above embodiment, the capacitor lower electrode 15 and the capacitor upper electrode 16 may be composed of a plurality of films.
[0029]
In the above embodiments, the barrier film containing the additive element can be formed by, for example, a binary sputtering method, a single sputtering method, a chemical vapor deposition method, or the like.
For example, if a film is formed using a binary sputtering method, a target of a single element can be used, so that the target can be easily obtained and the ratio of additive elements can be easily changed. Further, if a film is formed by a one-way sputtering method using a target containing an additive element, the sputtering time can be shortened and the ratio of the additive element can be kept constant. Furthermore, if the film is formed by a chemical vapor deposition method using a mixed gas, when a barrier film is formed by filling a groove after forming a groove in the insulating film, the filling property is good even if the groove width is narrow. .
[0030]
In order to contain the additive element more simply, after forming a film of the main constituent material, a film of the additive element is formed, and heat treatment is performed to raise the substrate temperature to 200 ° C. or higher. In this case, the film of the additive element is preferably removed by etching or the like after the heat treatment.
[0031]
In the above embodiment, when the main constituent material of the barrier film 14 is titanium nitride (Ti _x N _y ), it is made of silicon (Si), cobalt (Co), nickel (Ni), ruthenium (Ru). Although it has been described that the inclusion of one kind of additive element selected from the group consisting of the above elements is effective in preventing the oxidation of the barrier film 14, it is possible to improve the adhesion between the barrier film 14 and the plug 13. In order to obtain a good effect, it is preferable to select silicon (Si) as an additive element. This is because the plug 13 often has silicon as a main constituent material, and when the same kind of silicon element is added to the barrier film 14, the bond with the plug 13 is strengthened. In order not to deteriorate the electrical resistance of the barrier film 14, it is preferable to select cobalt (Co) or nickel (Ni) having a low electrical resistance as the additive element. Further, in order to obtain an additional effect of improving the adhesion with the capacitor lower electrode 15, it is preferable to select ruthenium (Ru) as an additive element. This is because the capacitor lower electrode 15 often has ruthenium as a main constituent material, and when the same kind of ruthenium element is added to the barrier film 14, the bond with the capacitor lower electrode 15 becomes stronger.
[0032]
Further, in the above embodiment, when the main constituent material of the barrier film 14 is ruthenium (Ru), one kind of addition selected from the group consisting of silicon (Si), cobalt (Co), and nickel (Ni). Although it has been described that the inclusion of an element is effective in preventing oxidation of the barrier film 14, as an additional element for obtaining an additional effect of improving the adhesion between the barrier film 14 and the plug 13. It is preferable to select silicon (Si). In order not to deteriorate the electrical resistance of the barrier film 14, it is preferable to select cobalt (Co) or nickel (Ni) as the additive element.
[0033]
【The invention's effect】
According to the present invention, it is possible to provide a highly reliable semiconductor device, to provide a semiconductor device with a high yield, to provide a semiconductor device having a capacitive element structure that is unlikely to cause poor conduction, and to a gate structure that is unlikely to cause oxidation. It is possible to realize at least one of the following.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a semiconductor device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an example of a planar layout of the semiconductor device according to the first example of the present invention.
FIG. 3 is a diagram showing an additive concentration dependency of a diffusion coefficient in a low concentration region when titanium nitride according to the first embodiment of the present invention is used as a main constituent material of a barrier film.
FIG. 4 is a diagram showing the concentration dependence of diffusion coefficient in a high concentration region when titanium nitride according to the first embodiment of the present invention is used as a main constituent material of a barrier film.
FIG. 5 is a graph showing the additive concentration dependence of the diffusion coefficient in the low concentration region when tungsten nitride according to the first embodiment of the present invention is used as the main constituent material of the barrier film.
FIG. 6 is a graph showing the concentration dependence of diffusion coefficient in a high concentration region when tungsten nitride according to the first embodiment of the present invention is used as a main constituent material of a barrier film.
FIG. 7 is a graph showing the additive concentration dependence of the diffusion coefficient in the low concentration region when ruthenium according to the first embodiment of the present invention is used as the main constituent material of the barrier film.
FIG. 8 is a diagram showing the dependence of the diffusion coefficient on the concentration concentration in the high concentration region when ruthenium according to the first embodiment of the present invention is used as the main constituent material of the barrier film.
FIG. 9 is a cross-sectional view of a main part of a semiconductor device according to a second embodiment of the present invention.
FIG. 10 is a cross-sectional view of a main part of a semiconductor device according to a third embodiment of the present invention.
FIG. 11 is a cross-sectional view of a main part of a semiconductor device according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Transistor, 3 ... Information storage capacitive element, 4 ... Element isolation film, 5 ... Gate electrode, 6 ... Gate insulating film, 7, 8 ... Diffusion layer, 9 ... Insulating film, 10 ... Plug, DESCRIPTION OF SYMBOLS 11 ... Bit line, 12 ... Insulating film, 13 ... Plug, 14 ... Conductive film, 15 ... Capacitor lower electrode, 16 ... Capacitor insulating film, 17 ... Capacitor upper electrode, 18 ... Insulating film, 19 ... Conductive film, 20 ... conductive film.

Claims (3)

A semiconductor substrate;
A gate insulating film formed on one main surface side of the semiconductor substrate;
A gate electrode formed on top of the gate insulating film,
The gate electrode includes a polycrystalline silicon film formed in contact with the gate insulating film;
A barrier film that is formed so as to be in contact with the polycrystalline silicon film, the main constituent material is titanium nitride, and contains one kind of additive element selected from the group consisting of cobalt, nickel, and ruthenium;
A metal film formed in contact with the barrier film,
The semiconductor device, wherein a content ratio of the additive element with respect to the main constituent material of the barrier film is 0.05 at.% Or more and 18 at.% Or less. A semiconductor substrate;
A gate insulating film formed on one main surface side of the semiconductor substrate;
A gate electrode formed on top of the gate insulating film,
The gate electrode is a polycrystalline silicon film formed in contact with the gate insulating film;
A barrier film formed in contact with the polycrystalline silicon film, the main constituent material is tungsten nitride, and molybdenum is added as an additive element;
A metal film that is formed in contact with the barrier film and whose main constituent material is tungsten or molybdenum, and
The semiconductor device, wherein a content ratio of the additive element with respect to the main constituent material of the barrier film is 0.05 at.% Or more and 18 at.% Or less. A semiconductor substrate;
A gate insulating film formed on one main surface side of the semiconductor substrate;
A gate electrode formed on top of the gate insulating film,
The gate electrode is a polycrystalline silicon film formed in contact with the gate insulating film;
Wherein formed in contact with the polycrystalline silicon film, the main component material is ruthenium, and a barrier film containing one kind of additive elements selected from the group consisting of divorced, cobalt, nickel,
A metal film whose main constituent material formed so as to be in contact with the barrier film is ruthenium, and
The semiconductor device, wherein a content ratio of the additive element with respect to the main constituent material of the barrier film is 0.05 at.% Or more and 18 at.% Or less.

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