Semiconductor device and method for fabricating the same

A method for fabricating a capacitor includes: forming a bottom electrode; forming a dielectric layer on the bottom electrode; forming a metal oxide layer including a metal having a high electronegativity on the dielectric layer; forming a sacrificial layer on the metal oxide layer to reduce the metal oxide layer to a metal layer; and forming a top electrode on the sacrificial layer to convert the reduced metal layer into a high work function interface layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application No. 10-2017-0160654, filed on Nov. 28, 2017, which is incorporated herein by reference in its entirety.

BACKGROUND

Exemplary embodiments of the present invention relates generally to a semiconductor device and a method for fabricating the same. More particularly, the present invention relates to a semiconductor device including a capacitor and a method for fabricating the semiconductor device.

2. Description of the Related Art

A capacitor of a semiconductor device may include a bottom electrode, a dielectric layer, and a top electrode. As the degree of integration of a semiconductor device increases, the thickness of the dielectric layer decreases which may result in increased leakage current. Increasing the thickness of the dielectric layer to reduce the leakage current leads to an increase in the equivalent oxide layer thickness (Tox).

SUMMARY

Exemplary embodiments of the present invention are directed to a semiconductor device including a capacitor which has improved leakage current characteristics, and a method for fabricating the semiconductor device.

In accordance with an embodiment of the present invention, a method for fabricating a capacitor includes: forming a bottom electrode; forming a dielectric layer on the bottom electrode; forming a metal oxide layer including a metal having a high electronegativity on the dielectric layer; forming a sacrificial layer on the metal oxide layer to reduce the metal oxide layer to a metal layer; and forming a top electrode on the sacrificial layer to convert the reduced metal layer into a high work function interface layer.

The forming of the sacrificial layer on the metal oxide layer may be performed under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer may include: forming a silicon layer on the metal oxide layer using a hydrogen-containing silicon source gas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer may include: forming a doped silicon layer on the metal oxide layer using a hydrogen-containing silicon source gas and a hydrogen-containing dopant gas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer may include: forming a silicon oxide layer on the metal oxide layer; and forming a silicon layer on the silicon oxide layer using a hydrogen-containing silicon source gas under a hydrogen gas atmosphere.

The forming of the silicon oxide layer on the metal oxide layer may include: forming a laminate structure by alternatively depositing the metal oxide layer and the silicon oxide layer.

The forming of the top electrode on the sacrificial layer may include: forming a silicon germanium layer doped with an impurity on the sacrificial layer.

The forming of the top electrode on the sacrificial layer may be performed at a temperature such that the sacrificial layer and the reduced metal layer react to form a metal silicide layer or a metal germanide.

The metal oxide layer may include a nickel oxide, the reduced metal layer may include a nickel layer, and the high work function interface layer may include a nickel silicide or a nickel-rich nickel silicide.

The metal oxide layer may include a cobalt oxide, the reduced metal layer may include a cobalt layer, and the high work function interface layer may include a cobalt silicide or a cobalt-rich cobalt silicide.

The metal oxide layer may include a tungsten oxide, the reduced metal layer may include a tungsten layer, and the high work function interface layer may include a tungsten silicide or a tungsten-rich silicide.

The forming of the sacrificial layer on the metal oxide layer may include: forming a germanium layer on the metal oxide layer using a hydrogen-containing germanium source gas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer may include: forming a doped germanium layer on the metal oxide layer using a hydrogen-containing germanium source gas and a hydrogen-containing dopant gas under a hydrogen gas atmosphere.

The forming of the sacrificial layer on the metal oxide layer may include: forming a germanium oxide layer on the metal oxide layer; and forming a germanium layer on the germanium oxide layer using a hydrogen-containing germanium source gas under a hydrogen gas atmosphere.

The forming of the germanium oxide layer on the metal oxide layer may include: forming a laminate structure by alternatively depositing the metal oxide layer and the germanium oxide layer.

The metal oxide layer may include a nickel oxide, the reduced metal layer may include a nickel layer, and the high work function interface layer may include a nickel germanide.

The metal oxide layer may include a cobalt oxide, the reduced metal layer may include a cobalt layer, and the high work function interface layer may include a cobalt germanide.

The metal oxide layer may include a tungsten oxide, the reduced metal layer may include a tungsten layer, and the high work function interface layer may include a tungsten germanide.

The dielectric layer may include a zirconium oxide, an aluminum oxide, or a combination thereof.

The bottom electrode may include a titanium nitride, and the top electrode may include a boron-doped silicon germanium layer.

In accordance with an embodiment of the present invention, a capacitor includes: a bottom electrode; a dielectric layer formed on the bottom electrode; a high work function interface layer formed on the dielectric layer; and a top electrode including a silicon germanium layer formed on the high work function interface layer, wherein the high work function interface layer includes a silicide having a high electronegativity or a germanide having a high electronegativity.

The high work function interface layer may include a nickel silicide or a nickel-rich nickel silicide.

The high work function interface layer may include a cobalt silicide, a cobalt-rich cobalt silicide, a tungsten silicide, or a tungsten-rich tungsten silicide.

The high work function interface layer may include a nickel germanide, a cobalt germanide, or a tungsten germanide.

The top electrode may include a boron-doped silicon germanium layer.

The dielectric layer may include a zirconium oxide, an aluminum oxide, or a combination thereof.

The bottom electrode may have a cylindrical shape or a pillar shape.

The bottom electrode may include a titanium nitride.

DETAILED DESCRIPTION

Hereafter, the embodiments of the present invention are described in detail. To simplify the description, a Dynamic Random Access Memory (DRAM) device is taken as an example, but the concept and spirit of the present invention are not limited to the DRAM only, and they may be applied to other memory devices or semiconductor devices.

The embodiments described below are directed to an interface layer and a top electrode having a high work function of approximately 4.9 eV or higher while preventing a reduction of a dielectric layer.

FIG. 1Ais a cross-sectional view of a semiconductor device100in accordance with an embodiment of the present invention.

Referring toFIG. 1A, the semiconductor device100may include a first conductive layer101, a dielectric layer102, and a second conductive layer103.

The first conductive layer101may be formed of a silicon-containing material and/or a metal-containing material. For example, the first conductive layer101may be or include polysilicon, a metal, a metal nitride, a conductive metal oxide or combinations thereof. In some embodiments, the first conductive layer101may be or include doped polysilicon, titanium (Ti), a titanium nitride (TiN), a tantalum nitride (TaN), tungsten (W), a tungsten nitride (WN), ruthenium (Ru), iridium (Ir), a ruthenium oxide, an iridium oxide or combinations thereof.

The dielectric layer102may be formed of a high-k material. The dielectric layer102may be or include a high-k material having a dielectric constant that is higher than the dielectric constant of a silicon oxide. Examples of suitable high-k materials may include a hafnium oxide (HfO2), a zirconium oxide (ZrO2), an aluminum oxide (Al2O3), a titanium oxide (TiO2), a tantalum oxide (Ta2O5), a niobium oxide (Nb2O5) or a strontium titanium oxide (SrTiO3). According to another embodiment of the present invention, the dielectric layer102may be a composite layer including two or more layers made of a high-k material. According to an embodiment of the present invention, the dielectric layer102may be formed of a zirconium oxide-based material having fine leakage current characteristics while sufficiently decreasing an equivalent oxide layer thickness. For example, in some embodiments the dielectric layer102may be or include a ZAZ (ZrO2/Al2O3/ZrO2) or a ZAZA (ZrO2/Al2O3/ZrO2/Al2O3). According to other embodiments of the present invention, the dielectric layer102may be or include a HAH (HfO2/Al2O3/HfO2). According to yet other embodiments of the present invention, the dielectric layer102may be or include one of the following multi-layer structures TiO2/ZrO2/Al2O3/ZrO2, TiO2/HfO2/Al2O3/HfO2, Ta2O5/ZrO2/Al2O3/ZrO2or Ta2O5/HfO2/Al2O3/HfO2.

The second conductive layer103may be formed of a non-metal material. For example, the second conductive layer103may be formed of a silicon-containing material, a germanium-containing material or a combination thereof. In some embodiments, the second conductive layer103may include a silicon (Si) layer, a germanium (Ge) layer, a silicon germanium (SiGe) layer or combinations thereof. In some embodiments, the second conductive layer103may have a multi-layer structure (SiGe/Si) formed by stacking the silicon germanium layer on the silicon layer. In other embodiments, the second conductive layer103may have a multi-layer structure (SiGe/Ge) formed by stacking the silicon germanium layer on the germanium layer.

An interface layer104may be formed between the dielectric layer102and the second conductive layer103. The interface layer104may be formed of a conductive material. The interface layer104may be or include a high work function material. The interface layer104may be qualified as a “high work function interface layer.” For example, the interface layer104may include a metal silicide. The interface layer104may include a silicide whose electronegativity is high. In some embodiments, the interface layer104may include a nickel silicide, a cobalt silicide or a tungsten silicide.

A stack structure of the first conductive layer101, the dielectric layer102, the interface layer104and the second conductive layer103may become a capacitor.

FIG. 1Bis a cross-sectional view of a capacitor100M as an application example of the semiconductor device in accordance with an embodiment of the present invention.

Referring toFIG. 1B, the capacitor100M may include a bottom electrode101M, a dielectric layer102M, an interface layer104M, and a top electrode103M.

The bottom electrode101M may be formed of a metal nitride. For example, the bottom electrode101M may be formed, for example, of a titanium nitride (TiN).

The top electrode103M may be formed, for example, of a silicon germanium (SiGe) layer. The silicon germanium layer may be doped with a dopant, for example, boron.

The dielectric layer102M may have a ZAZ (ZrO2/Al2O3/ZrO2) stack structure. The dielectric layer102M may include a first zirconium oxide102A, an aluminum oxide102B and a second zirconium oxide102C which are sequentially stacked. The dielectric layer102M may further include an aluminum oxide102D formed on the second zirconium oxide102C. This structure is referred to as a ZAZA stack structure. The aluminum oxide102D, which is a material with a large bandgap, may improve a leakage current. According to another embodiment, SiO2may be employed as a large bandgap material instead of aluminum oxide102D.

The interface layer104M may be formed, for example, a nickel silicide (Ni-Silicide).

FIG. 1Cis a cross-sectional view of a capacitor100M′ as an application example of the semiconductor device in accordance with an embodiment of the present invention.

Referring toFIG. 1C, the capacitor100M′ may include a bottom electrode101M, a dielectric layer102M, an interface layer104M′, and a top electrode103M. Hence, the capacitor100M′ may be identical to the capacitor100M ofFIG. 1Bexcept for the interface layer104M′. Specifically, the bottom electrode101M may be formed of a metal nitride. For example, the bottom electrode101M may be formed, for example, of a titanium nitride (TIN).

The top electrode103M may be formed, for example, of a silicon germanium (SiGe) layer. The silicon germanium layer may be doped with a dopant, for example, boron.

The dielectric layer102M may have a ZAZ (ZrO2/Al2O3/ZrO2) stack structure. The dielectric layer102M may include a first zirconium oxide102A, an aluminum oxide102B and a second zirconium oxide102C which are sequentially stacked. The dielectric layer102M may further include an aluminum oxide102D formed on the second zirconium oxide102C. This structure is referred to as a ZAZA stack structure. The aluminum oxide102D, which is a material with a large bandgap, may improve a leakage current. According to another embodiment, SiO2may be employed as a large bandgap material instead of aluminum oxide102D.

The interface layer104M′ may include a nickel-rich nickel silicide (Ni-rich Ni-Silicide). The nickel-rich nickel silicide refers to a nickel silicide where the number of nickel atoms is greater than the number of silicon atoms. For example, nickel-rich nickel silicide include Ni3Si, Ni2Si, and Ni3Si2.

FIGS. 2A to 2Dare cross-sectional views illustrating an example of a method for fabricating the semiconductor device100in accordance with an embodiment of the present invention.

Referring toFIG. 2A, a first conductive layer11may be formed. The first conductive layer11may be formed of a silicon-containing material and/or a metal-containing material. For example, the first conductive layer11may include polysilicon, a metal, a metal nitride, a conductive metal oxide or combinations thereof. In some embodiments, the first conductive layer11may include doped polysilicon, titanium (Ti), a titanium nitride (TiN), a tantalum nitride (TaN), tungsten (W), a tungsten nitride (WN), ruthenium (Ru), iridium (Ir), a ruthenium oxide, an iridium oxide, etc. In an embodiment, the first conductive layer11may be formed, for example, by Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD) or any other suitable method.

A dielectric layer12may be formed on the first conductive layer11. The dielectric layer12may be formed of a high-k material. The dielectric layer12may be formed of a high-k material having a dielectric constant that is higher than the dielectric constant of a silicon oxide. In some embodiments, the dielectric layer12may include a hafnium oxide (HfO2), a zirconium oxide (ZrO2), an aluminum oxide (Al2O3), a titanium oxide (TiO2), a tantalum oxide (Ta2O5), a niobium oxide (Nb2O5) or a strontium titanium oxide (SrTIO3). According to another embodiment of the present invention, the dielectric layer12may be a composite layer including two or more layers of the aforementioned high-k materials. According to an embodiment of the present invention, the dielectric layer12may be formed of a zirconium oxide-based material having fine leakage current characteristics while sufficiently reducing an equivalent oxide layer thickness. For example, the dielectric layer12may include a ZAZ (ZrO2/Al2O3/ZrO2) or a ZAZA (ZrO2/Al2O3/ZrO2/Al2O3) structure. According to another embodiment of the present invention, the dielectric layer12may include a HAH (HfO2/Al2O3/HfO2) structure. According to yet another embodiment of the present invention, the dielectric layer12may be one of the following multi-layer structures TiO2/ZrO2/Al2O3/ZrO2, TiO2/HfO2/Al2O3/HfO2, Ta2O5/ZrO2/Al2O3/ZrO2or Ta2O5/HfO2/Al2O3/HfO2.

Referring toFIG. 2B, a sacrificial interface layer13may be formed on the dielectric layer12. The sacrificial interface layer13may include an easily-reduced chemical species of oxide. The sacrificial interface layer13may include a chemical species of oxide whose electronegativity is high. The sacrificial interface layer13may include an easily-reduced chemical species of oxide whose electronegativity is high. The sacrificial interface layer13may be 2 nm or less in thickness D1.

According to an embodiment of the present invention, the sacrificial interface layer13may include an easily-reduced metal oxide whose electronegativity is high. For example, the sacrificial interface layer13may be a nickel-containing layer. In an embodiment, the sacrificial interface layer13may include an oxide containing nickel, i.e., a nickel oxide (NiO). The electronegativity of nickel may be approximately 1.91. According to another embodiment of the present invention, the sacrificial interface layer13may be made of or include a cobalt oxide or a tungsten oxide. The electronegativity of cobalt may be approximately 1.8, and the electronegativity of tungsten may be approximately 1.7.

Generally, a work function of a material relates to the electronegativity of an element or elements making up the material. For example, an element having a higher electronegativity has a larger work function, and an element having a lower electronegativity has a smaller work function. In case of a metal, the electronegativity increases through oxidation.

Referring toFIG. 2C, the sacrificial interface layer13may be exposed to a reducing atmosphere14to reduce the sacrificial interface layer13and form an initial interface layer16. The reducing atmosphere14may include a hydrogen gas. In an embodiment, the initial interface layer16may be formed by depositing a sacrificial silicon layer15at the hydrogen gas reducing atmosphere.

The sacrificial silicon layer15may be deposited under the reducing atmosphere14including the hydrogen gas. Since hydrogen has great reducing power, the sacrificial interface layer13may be reduced when the sacrificial silicon layer15is deposited. A material remaining due to the reduction of the sacrificial interface layer13is qualified as an initial interface layer16for short. When the sacrificial interface layer13is formed of a metal oxide, the metal oxide may be reduced to a metal by hydrogen. For example, when the sacrificial interface layer13is formed, for example, a nickel oxide (NiO), nickel (Ni) may be formed by a reduction of the nickel oxide (NiO). The initial interface layer16may have high electronegativity. When the sacrificial silicon layer15is formed under the reducing atmosphere14of hydrogen gas, the sacrificial silicon layer15can be deposited at a low temperature. For example, the sacrificial silicon layer15is formed at a low temperature of 450° C.

The sacrificial silicon layer15may be or include a doped silicon layer. For example, the sacrificial silicon layer15may be a silicon layer doped with boron. The sacrificial silicon layer15may be formed by a CVD method. The sacrificial silicon layer15may be deposited using a hydrogen-containing silicon source gas under the reducing atmosphere14including the hydrogen gas. According to another embodiment of the present invention, the sacrificial silicon layer15may be deposited using the hydrogen-containing silicon source gas and a hydrogen-containing dopant gas under the reducing atmosphere14including the hydrogen gas. The hydrogen-containing silicon source gas may include silane (SiH4) or disilane (Si2H6). The hydrogen-containing dopant gas may include boron, borane (BH3), diborane (B2H6) or any combinations thereof. In this manner, the hydrogen-containing silicon source gas and the hydrogen-containing dopant gas, which are as compounds containing hydrogen, may promote the reduction of the sacrificial interface layer13.

As described above, when the sacrificial silicon layer15is formed, the sacrificial interface layer13is reduced so that the initial interface layer16is formed between the sacrificial silicon layer15and the dielectric layer12. The initial interface layer16has high electronegativity and a high work function.

When the sacrificial silicon layer15is formed, the dielectric layer12is be exposed to the silicon source gas, the dopant gas and the reducing atmosphere14. In other words, the sacrificial interface layer13and the initial interface layer16can prevent the dielectric layer12from being reduced.

Referring toFIG. 2D, a second conductive layer17may then be formed on the sacrificial silicon layer15. The second conductive layer17may be or include a silicon-containing material. For example, the second conductive layer17may be or include a silicon germanium (SiGe) layer or a boron-doped silicon germanium (SiGe) layer. The silicon germanium (SiGe) layer may be deposited using a silicon source gas and a germanium source gas. The boron-doped silicon germanium (SiGe) layer may be deposited using the silicon source gas, the germanium source gas and a boron-containing dopant gas. The silicon germanium (SiGe) layer may use a hydrogen-containing gas such as H2as a reaction gas. Each of the silicon source gas, the germanium source gas and the boron-containing dopant gas may contain hydrogen.

In an embodiment, the second conductive layer17may be deposited at a temperature of approximately 400° C. When the second conductive layer17is deposited at the temperature of approximately 400% C, the sacrificial silicon layer15and the initial interface layer16may react due to a thermal budget. For example, an the total amount of energy transferred to the sacrificial silicon layer15and the initial interface layer16at the elevated temperature (the thermal budget). An interface layer18may be formed through silicidation. The sacrificial silicon layer15and the initial interface layer16may be all consumed during the silicidation, thereby being completely converted into the interface layer18. In other words, the interface layer18may be formed through full silicidation of the sacrificial silicon layer15and the initial interface layer16. The interface layer18may be referred to as a fully-silicided interface layer (FUSI IL).

The interface layer18may include a silicide whose electronegativity is high. For example, the interface layer18may include a nickel silicide, a cobalt silicide or a tungsten silicide.

Since the interface layer18includes a material whose electronegativity is high such as nickel, the interface layer18may have a high work function of approximately 4.9 eV or higher.

After the second conductive layer17is deposited, a thermal process may be further performed at a temperature of approximately 500° C. or lower if necessary. Hence, resistance of the interface layer18may decrease.

According to another embodiment of the present invention, the second conductive layer17may be formed by stacking a silicon layer and a silicon germanium layer. The silicon layer and the silicon germanium layer may be doped with a dopant, for example, boron. For example, a boron-doped silicon layer and a boron-doped silicon germanium layer may be stacked to form the second conductive layer17.

As described above, a stack structure of the first conductive layer11, the dielectric layer12, the interface layer18and the second conductive layer17that are formed through a series of processes may become a capacitor. The first conductive layer11may be qualified as a bottom electrode of the capacitor or a storage node, and the second conductive layer17may be qualified as a top electrode of the capacitor or a plate. The interface layer18and the dielectric layer12may be in direct contact. The interface layer18and the second conductive layer17may be in direct contact. Since the second conductive layer17includes the silicon germanium layer, the top electrode of the capacitor may be formed of a non-metal material or a non-metal nitride.

FIGS. 3A to 3Care cross-sectional views illustrating another example of a method for fabricating a semiconductor device in accordance with an embodiment of the present invention illustrated inFIG. 1A. Detailed descriptions of the processes which are identical to those described above with reference toFIGS. 2A to 2Dare omitted.

Referring toFIG. 3A, a method for fabricating the semiconductor device in accordance with a modified example of an embodiment of the present invention may include forming a sacrificial interface layer13′ on a dielectric layer12after forming the dielectric layer12through the processes described above with reference toFIGS. 2A and 2B. The sacrificial interface layer13′ may include an oxide of an easily-reduced material. The sacrificial interface layer13′ may include an oxide whose electronegativity is high. The sacrificial interface layer13′ may include an easily-reduced oxide whose electronegativity is high.

For example in an embodiment, the sacrificial interface layer13′ may be made of or include an easily-reduced, high electronegativity oxide such as an oxide of nickel, i.e., a nickel oxide (NiO). According to another embodiment of the present invention, the sacrificial interface layer13′ may be made of or include a cobalt oxide or a tungsten oxide. The sacrificial interface layer13′ may have a fourth thickness D11.

The fourth thickness D11of the sacrificial interface layer13′ shown inFIG. 3Amay be larger than a first thickness D1of the sacrificial interface layer13shown inFIG. 2B. The thickness of the sacrificial interface layer13′ may be approximately 2 nm or less.

Referring toFIG. 3B, a sacrificial silicon layer15may be formed under a hydrogen gas atmosphere14. When the sacrificial silicon layer15is deposited, an initial interface layer16′ may be formed by a reduction of the sacrificial interface layer13′. The initial interface layer16′ may be formed between the sacrificial silicon layer15and the dielectric layer12and may have a fifth thickness D12. The fifth thickness D12of the initial interface layer16′ may be formed to be larger than a second thickness D2of the initial interface layer16shown inFIG. 2C. The initial interface layer16′ may have the same thickness (D11=D12) as the sacrificial interface layer13′.

Referring toFIG. 3C, a second conductive layer17′ may be formed on the sacrificial silicon layer15. The second conductive layer17′ may be or include a silicon-containing material. The second conductive layer17′ may be or include a silicon germanium (SiGe) layer or a boron-doped silicon germanium (SiGe) layer. The silicon germanium (SiGe) layer may be deposited using a silicon source gas and a germanium source gas. The boron-doped silicon germanium (SiGe) layer may be deposited using the silicon source gas, the germanium source gas and a boron-containing dopant gas. The silicon germanium (SiGe) layer may use a hydrogen-containing gas such as H2as a reaction gas. Each of the silicon source gas, the germanium source gas and the boron-containing dopant gas may contain hydrogen.

The second conductive layer17′ may be deposited at a temperature of approximately 400° C. When the second conductive layer17′ is deposited at the temperature of approximately 400° C., the sacrificial silicon layer15and the initial interface layer16′ react due to the thermal budget. For example, an interface layer18′ may be formed through silicidation. The sacrificial silicon layer15and the initial interface layer16′ may be all consumed during the silicidation, thereby being completely converted into the interface layer18′. In other words, the interface layer18′ may be formed through full silicidation of the sacrificial silicon layer15and the initial interface layer16′. The interface layer18′ may have a sixth thickness D13.

The sixth thickness D13of the interface layer18′ shown inFIG. 3Cmay be larger than a third thickness D3of the interface layer18shown inFIG. 2D.

The interface layer18′ may be formed of a metal-rich metal silicide (MxSiy). The metal-rich metal silicide (MxSiy) may have a ratio of metal to silicon (x/y) greater than 1. The interface layer18′ may include a nickel-rich nickel silicide. For example, the nickel-rich nickel silicide may include a Ni2Si phase or a Ni3Si2phase. The interface layer18′ may include a cobalt-rich cobalt silicide or a tungsten-rich tungsten silicide.

Since the interface layer18′ includes a material whose electronegativity is high such as nickel, the interface layer18′ may have a high work function of approximately 4.9 eV or higher. Besides, since the interface layer18′ includes the metal-rich metal silicide, the interface layer18′ may have a greatly higher work function. For example, a nickel silicide having the Ni2Si phase may have the work function ranging from approximately 4.9 eV to approximately 5.0 eV. The nickel silicide having the Ni2Si phase may have a higher work function than a nickel silicide having a NiSi phase.

As described above, the interface layer18′ may be formed of the metal-rich metal silicide having a large metal content. The metal content may be adjusted by increasing the thickness of the sacrificial interface layer13′ and increasing the amount of hydrogen gas implantation when the second conductive layer17′ is deposited.

A series of processes for forming the interface layer18′ may be represented by the following chemical formula:
NiO+H*+Si2H6*→NixSiy(x>y,x≥2)

According to the embodiments described above, a leakage current may be improved without deterioration of the equivalent oxide layer thickness, and interface resistance may be also improved. In addition, the process cost may decrease while simplifying the process because a TiN process is not performed on the second conductive layers17and17′.

As a comparative example, an upper portion of the dielectric layer12may be directly deposited with a titanium nitride (TIN). A TiN deposition process may be performed by using TiCl4and NH3. Subsequently, a silicon germanium layer may be deposited on the TiN. A deposition process of the silicon germanium layer may be performed by using a gas such as SiH4and GeH4.

NH3, SiH4and GeH4used during such a SiGe/TiN stack deposition process may lead to a reduction of the dielectric layer12as strong reductants. Due to the reduction of the dielectric layer12, the loss of oxygen may occur in the dielectric layer12and the quality of the layer may deteriorate.

According to an embodiment and the modified example of the present invention, since the sacrificial interface layers13and13′ which are easily reduced are formed on the dielectric layer12, the reduction of the dielectric layer12may not occur although the dielectric layer12is exposed to a series of processes including a subsequent hydrogen gas. Accordingly, oxygen of the dielectric layer12may be prevented from being lost.

The use of the top electrode having a high work function to decrease the leakage current of the capacitor does not deteriorate the equivalent oxide layer thickness of the dielectric layer. TiN is widely known to those skilled in the art as the top electrode having high work function. The high work function of TiN is approximately 4.9 eV.

Recently, in order to decrease greatly the leakage current, a top electrode having a high work function of approximately 4.9 eV or higher has been required. It is known that such materials as Ru, Pt, etc. have a higher work function than TiN. However, since these noble metals are expensive and an etch process thereof is difficult, there is limitation in applying them to high integrated capacitors.

According to the present invention, as the interface layers18and18′ are formed by using materials whose electronegativity is high, the desired high work function of approximately 4.9 eV or higher can be obtained, thereby improving the leakage current of a capacitor without deterioration of the equivalent oxide layer thickness.

FIGS. 4A to 4Care cross-sectional views illustrating yet another example of method for fabricating the semiconductor device in accordance with an embodiment of the present invention. Detailed descriptions of the processes which overlap with those described above with reference toFIGS. 2A to 2Dare omitted.

Referring toFIG. 4A, a method for fabricating the semiconductor device in accordance with an embodiment of the present invention may include forming a sacrificial interface layer13on a dielectric layer12after forming the dielectric layer12through the processes described above with reference toFIGS. 2A and 2B. The sacrificial interface layer13may be made of or include a nickel oxide (NiO). According to another embodiment of the present invention, the sacrificial interface layer13may be made of or include a cobalt oxide or a tungsten oxide. The sacrificial interface layer13may be formed by an Atomic Layer Deposition (ALD) or any other suitable method.

Subsequently, an auxiliary sacrificial interface layer21may be formed on the sacrificial interface layer13. The auxiliary sacrificial interface layer21may be formed, for example, by the ALD. The auxiliary sacrificial interface layer21may be or include a silicon-containing material. The auxiliary sacrificial interface layer21may include a silicon oxide (SiO2).

The sacrificial interface layer13and the auxiliary sacrificial interface layer21may be formed, for example, by the ALD. The sacrificial interface layer13and the auxiliary sacrificial interface layer21may be formed in a bi-layer structure. For example, the sacrificial interface layer13and the auxiliary sacrificial interface layer21may be formed in the bi-layer structure of SiO2/NiO.

According to another embodiment of the present invention, the sacrificial interface layer13and the auxiliary sacrificial interface layer21may be formed in a laminate structure. For example, the laminate structure may include alternating layers of the sacrificial interface layer13and the auxiliary sacrificial interface layer21.

FIG. 5is a cross-sectional view illustrating a laminate structure of a nickel oxide and a silicon oxide.

Referring toFIG. 5, the nickel oxide and the silicon oxide may be alternately deposited to form the laminate structure such as SiO2/NiO/SiO2/NiO. Each of the nickel oxide and the silicon oxide may be alternately deposited at least twice.

Total thickness of the sacrificial interface layer13and the auxiliary sacrificial interface layer21may be 2 nm or less.

Referring toFIG. 4B, the sacrificial interface layer13and the auxiliary sacrificial interface layer21may be exposed to a reducing atmosphere14. When the sacrificial interface layer13and the auxiliary sacrificial interface layer21are exposed to the reducing atmosphere14, the sacrificial interface layer13and the auxiliary sacrificial interface layer21may be reduced. An initial interface layer16may be formed by such a reduction of the sacrificial interface layer13. Besides, an auxiliary initial interface layer21′ may be formed by such a reduction of the auxiliary sacrificial interface layer21.

According to an embodiment of the present invention, a deposition process of a sacrificial silicon layer15may be performed to form the initial interface layer16. The deposition process of the sacrificial silicon layer15may be performed under the reducing atmosphere14including a hydrogen gas.

The sacrificial silicon layer15may be deposited under the reducing atmosphere14including a large amount of the hydrogen gas. Since hydrogen has great reducing power, the sacrificial interface layer13and the auxiliary sacrificial interface layer21may be reduced when the sacrificial silicon layer15is deposited. A material remaining due to the reduction of the sacrificial interface layer13is qualified as the initial interface layer16for short. When the sacrificial interface layer13is formed of a metal oxide, the metal oxide may be reduced to a metal by hydrogen. For example, when the sacrificial interface layer13is formed, for example, a nickel oxide (NiO), nickel (Ni) may be formed by a reduction of the nickel oxide (NiO). The initial interface layer16may have high electronegativity. When the sacrificial silicon layer15is formed under the reducing atmosphere14, the sacrificial silicon layer15may be deposited at a low temperature. A material remaining due to the reduction of the auxiliary sacrificial interface layer21is qualified as the auxiliary initial interface layer21′ for short. When the auxiliary sacrificial interface layer21is formed of a silicon oxide, the silicon oxide may be converted into silicon by hydrogen. For example, the auxiliary initial interface layer21′ may be a silicon layer.

The sacrificial silicon layer15may be or include a doped silicon layer. The sacrificial silicon layer15may be a silicon layer doped with boron. The sacrificial silicon layer15may be formed, for example, CVD or any other suitable method. The sacrificial silicon layer15may be deposited using a hydrogen-containing silicon source gas under the reducing atmosphere14including the hydrogen gas. According to another embodiment of the present invention, the sacrificial silicon layer15may be deposited using the hydrogen-containing silicon source gas and a hydrogen-containing dopant gas under the reducing atmosphere14including the hydrogen gas. The hydrogen-containing silicon source gas may include silane (SiH4) or disilane (Si2H6). The hydrogen-containing dopant gas may include boron, borane (BH3), diborane (B2H6) or any combinations thereof. In this manner, the hydrogen-containing silicon source gas and the hydrogen-containing dopant gas, which are compounds containing hydrogen, may promote the reduction of the sacrificial interface layer13.

As described above, when the sacrificial silicon layer15is formed, the sacrificial interface layer13may be reduced so that the initial interface layer16may be formed between the sacrificial silicon layer15and the dielectric layer12. The initial interface layer16has high electronegativity and high work function.

When the sacrificial silicon layer15is formed, the dielectric layer12is not exposed to the hydrogen-containing silicon source gas, the hydrogen-containing dopant gas and the reducing atmosphere14. In other words, the sacrificial interface layer13and the initial interface layer16prevent the dielectric layer12from being reduced.

Referring toFIG. 4C, a second conductive layer17may be formed on the sacrificial silicon layer15. The second conductive layer17may be made of or include a silicon-containing material. The second conductive layer17may be made of or include a silicon germanium (SiGe) layer or a boron-doped silicon germanium (SiGe) layer. The silicon germanium (SiGe) layer may be deposited using a silicon source gas and a germanium source gas. The boron-doped silicon germanium (SiGe) layer may be deposited using the silicon source gas, the germanium source gas and a boron-containing dopant gas. The silicon germanium (SiGe) layer may use a hydrogen-containing gas such as H2as a reaction gas. Each of the silicon source gas, the germanium source gas and the boron-containing dopant gas may contain hydrogen.

The second conductive layer17may be deposited at a temperature of approximately 400° C. When the second conductive layer17is deposited at the temperature of approximately 400° C., the sacrificial silicon layer15, the auxiliary initial interface layer21′ and the initial interface layer16react due to the thermal budget. For example, an interface layer18″ may be formed through silicidation. The sacrificial silicon layer15, the auxiliary initial interface layer21′ and the initial interface layer16may be all consumed during the silicidation, thereby being completely converted into the interface layer18″. In other words, the interface layer18″ may be formed through fully silicidation of the sacrificial silicon layer15, the auxiliary initial interface layer21′ and the initial interface layer16. The interface layer18″ may be referred to as a fully-silicided interface layer (FUSI IL).

The interface layer18″ may include a silicide whose electronegativity is high. For example, the interface layer18″ may include a nickel silicide, a cobalt silicide or a tungsten silicide.

Since the interface layer18″ includes a material whose electronegativity is high such as nickel, the interface layer18″ may have a high work function. The interface layer18″ may have the high work function of approximately 4.9 eV or higher.

As described above, the interface layer18″ may be formed through the silicidation of the sacrificial silicon layer15, the auxiliary initial interface layer21′ and the initial interface layer16. As the auxiliary initial interface layer21′ is additionally formed, the interface layer18″ may be easily controlled to be formed.

After the second conductive layer17is deposited, a thermal process may be further performed at a temperature of approximately 500° C. or lower if necessary. Hence, resistance of the interface layer18″ may decrease.

According to another embodiment of the present invention, the second conductive layer17may be formed by stacking a silicon layer and a silicon germanium layer. The silicon layer and the silicon germanium layer may be doped with a dopant, for example, boron. For example, a boron-doped silicon layer and a boron-doped silicon germanium layer may be stacked to form the second conductive layer17.

As described above, a stack structure of a first conductive layer11, the dielectric layer12, the interface layer18″ and the second conductive layer17that are formed through a series of processes may become a capacitor.

FIG. 6Ais a cross-sectional view of a semiconductor device200in accordance with an embodiment of the present invention. Detailed descriptions of the components and configurations of the semiconductor device which overlap with those shown as above with reference toFIG. 1Aare omitted.

Referring toFIG. 6A, the semiconductor device200may include a first conductive layer101, a dielectric layer102, and a second conductive layer103. An interface layer204may be formed between the dielectric layer102and the second conductive layer103.

The interface layer204may include a conductive material. The interface layer204may be or include a high work function material. The interface layer204may be or include the high work function material of approximately 4.9 eV or higher. The interface layer204may be or include a germanide material whose electronegativity is high. The interface layer204may be or include a metal germanide. The interface layer204may be or include a nickel germanide, a cobalt germanide or a tungsten germanide. The nickel germanide may have a high work function of approximately 5.2 eV.

FIG. 6Bis a cross-sectional view of a capacitor as an application example of the semiconductor device in accordance with an embodiment of the present invention.

Referring toFIG. 6B, a capacitor200M may include a bottom electrode101M, a dielectric layer102M, an interface layer204M, and a top electrode103M.

The bottom electrode101M may be formed of a metal nitride. The bottom electrode101M may be formed, for example, of a titanium nitride (TiN).

The top electrode103M may be formed, for example, of a silicon germanium (SiGe) layer. The silicon germanium layer may be doped with a dopant, for example, boron.

The dielectric layer102M may have a ZAZ (ZrO2/Al2O3/ZrO2) stack structure. The dielectric layer102M may include a first zirconium oxide102A, an aluminum oxide102B and a second zirconium oxide102C which are sequentially stacked. The dielectric layer102M may further include an aluminum oxide102D formed on the second zirconium oxide102C. This structure is referred to as a ZAZA stack structure.

The interface layer204M may be formed, for example, a nickel germanide (Ni-Germanide).

FIGS. 7A and 7Bare cross-sectional views illustrating an example of a method for fabricating the semiconductor device in accordance with the second embodiment of the present invention. Detailed descriptions of the processes which overlap with those shown above with reference toFIGS. 2A to 2Dare omitted.

The method for fabricating the semiconductor device in accordance with an embodiment of the present invention may include forming a sacrificial interface layer13on a dielectric layer12after forming the dielectric layer12through the processes described above with reference toFIGS. 2A and 2B. The sacrificial interface layer13may be made of or include a nickel oxide (NiO). According to another embodiment of the present invention, the sacrificial interface layer13may be made of or include a cobalt oxide or a tungsten oxide. The sacrificial interface layer13may be formed by an Atomic Layer Deposition (ALD) or any other suitable method.

Referring now toFIG. 7A, after the sacrificial interface layer13is formed, the sacrificial interface layer13may be exposed to a reducing atmosphere14. When the sacrificial interface layer13is exposed to the reducing atmosphere14, the sacrificial interface layer13may be reduced. An initial interface layer16may be formed by such a reduction of the sacrificial interface layer13.

According to the illustrated embodiment of the present invention, a deposition process of a sacrificial germanium layer31may be performed to form the initial interface layer16. The deposition process of the sacrificial germanium layer31may be performed under a reducing atmosphere14including a hydrogen gas.

Since hydrogen has great reducing power, the sacrificial interface layer13may be reduced when the sacrificial germanium layer31is deposited. A material remaining due to the reduction of the sacrificial interface layer13is qualified as the initial interface layer16for short. When the sacrificial interface layer13is formed of a metal oxide, the metal oxide may be reduced to a metal by hydrogen. For example, when the sacrificial interface layer13is formed, for example, of a nickel oxide (NiO), nickel (Ni) may be formed by a reduction of the nickel oxide (NiO). The initial interface layer16may have high electronegativity. When the sacrificial germanium layer31is formed under the reducing atmosphere14including a great amount of the hydrogen gas, the sacrificial germanium layer31may be deposited at a low temperature.

The sacrificial germanium layer31may have a doped germanium layer. The sacrificial germanium layer31may be a germanium layer doped with boron. The sacrificial germanium layer31may be formed, for example, by Chemical Vapor Deposition (CVD) or any other suitable method. The sacrificial germanium layer31may be deposited using a hydrogen-containing germanium source gas under the reducing atmosphere14including the hydrogen gas. According to another embodiment of the present invention, the sacrificial germanium layer31may be deposited using the hydrogen-containing germanium source gas and a hydrogen-containing dopant gas under the reducing atmosphere14including the hydrogen gas. In an embodiment, a compound gas containing hydrogen such as GeH4may be used as the hydrogen-containing germanium source gas. The hydrogen-containing dopant gas may include boron, borane (BH3), diborane (B2H6) or any combinations thereof. In this manner, the hydrogen-containing germanium source gas and the hydrogen-containing dopant gas, which are as compounds containing hydrogen, may promote the reduction of the sacrificial interface layer13.

As described above, when the sacrificial germanium layer31is formed, the sacrificial interface layer13may be reduced so that the initial interface layer16may be formed between the sacrificial germanium layer31and the dielectric layer12. The initial interface layer16has high electronegativity and high work function.

When the sacrificial germanium layer31is formed, the dielectric layer12is not exposed to the hydrogen-containing germanium source gas, the hydrogen-containing dopant gas and the reducing atmosphere14. In other words, the sacrificial interface layer13and the initial interface layer16prevent the dielectric layer12from being reduced.

Referring toFIG. 7B, a second conductive layer17may be formed on the sacrificial germanium layer31. The second conductive layer17may be or include a silicon-containing material. The second conductive layer17may be or include a silicon germanium (SiGe) layer or a boron-doped silicon germanium (SiGe) layer. The silicon germanium (SiGe) layer may be deposited using a silicon source gas and a germanium source gas. The boron-doped silicon germanium (SiGe) layer may be deposited using the silicon source gas, the germanium source gas and a boron-containing dopant gas. The silicon germanium (SiGe) layer may use a hydrogen-containing gas such as H2as a reaction gas. Each of the silicon source gas, the germanium source gas and the boron-containing dopant gas may contain hydrogen.

The second conductive layer17may be deposited at a temperature of approximately 400° C. When the second conductive layer17is deposited at the temperature of approximately 400° C., the sacrificial germanium layer31and the initial interface layer16react due to the thermal budget. For example, an interface layer32may be formed through a germanide reaction. The sacrificial germanium layer31and the initial interface layer16may be all consumed during the germanide reaction, thereby being completely converted into the interface layer32. In other words, the interface layer32may be formed through full-germanide reaction of the sacrificial germanium layer31and the initial interface layer16. The interface layer32may be referred to as a fully-germanide interface layer (FUGE IL). The interface layer32may be or include a metal germanide.

The interface layer32may be or include a germanide whose electronegativity is high. For example, the interface layer32may be or include a nickel germanide, a cobalt germanide or a tungsten germanide.

Since the interface layer32includes a material whose electronegativity is high such as nickel, the interface layer32may have a high work function of approximately 4.9 eV or higher. For example, a nickel germanide (NiGe) may have a high work function of approximately 5.2 eV. The nickel germanide (NiGe) may have a higher work function than the nickel silicide.

After the second conductive layer17is deposited, a thermal process may be further performed at a temperature of approximately 500% C or lower if necessary. Hence, resistance of the interface layer32may decrease.

According to another embodiment of the present invention, the second conductive layer17may be formed by stacking a silicon layer and a silicon germanium layer. The silicon layer and the silicon germanium layer may be doped with a dopant, for example, boron. For example, a boron-doped silicon (Si) layer and a boron-doped silicon germanium (SiGe) layer may be stacked to form the second conductive layer17.

As described above, a stack structure of a first conductive layer11, the dielectric layer12, the interface layer32and the second conductive layer17that are formed through a series of processes may become a capacitor.

FIGS. 8A to 8Care cross-sectional views illustrating another example of the method for fabricating the semiconductor device in accordance with an embodiment of the present invention.

The method for fabricating the semiconductor device in accordance with an embodiment of the present invention may include forming a sacrificial interface layer13on a dielectric layer12after forming the dielectric layer12through the processes described above with reference toFIGS. 2A and 2B. The sacrificial interface layer13may be made of or include a nickel oxide (NiO). According to another embodiment of the present invention, the sacrificial interface layer13may be made of or include a cobalt oxide or a tungsten oxide. The sacrificial interface layer13may be formed by an Atomic Layer Deposition (ALD) or any other suitable method.

Subsequently, referring toFIG. 8A, an auxiliary sacrificial interface layer41may be formed on the sacrificial interface layer13. The auxiliary sacrificial interface layer41may be formed, for example, by ALD or any other suitable method. The auxiliary sacrificial interface layer41may include a germanium-containing material. The auxiliary sacrificial interface layer41may include a germanium oxide (GeO2).

The sacrificial interface layer13and the auxiliary sacrificial interface layer41may be formed, for example, by ALD. The sacrificial interface layer13and the auxiliary sacrificial interface layer41may be formed in a bi-layer structure. For example, the sacrificial interface layer13and the auxiliary sacrificial interface layer41may be formed in the bi-layer structure of GeO2/NiO.

According to another embodiment of the present invention, the sacrificial interface layer13and the auxiliary sacrificial interface layer41may be formed in a laminate structure.

FIG. 9is a cross-sectional view illustrating a laminate structure of a nickel oxide and a germanium oxide.

Referring toFIG. 9, the nickel oxide and the germanium oxide may be alternately deposited to form the laminate structure such as GeO2/NiO/GeO2/NiO. Each of the nickel oxide and the germanium oxide may be alternately deposited at least twice.

Total thickness of the sacrificial interface layer13and the auxiliary sacrificial interface layer41may be 2 nm or less.

Referring toFIG. 8B, the sacrificial interface layer13and the auxiliary sacrificial interface layer41may be exposed to the reducing atmosphere14. When the sacrificial interface layer13and the auxiliary sacrificial interface layer41are exposed to the reducing atmosphere14, the sacrificial interface layer13and the auxiliary sacrificial interface layer41may be reduced. An initial interface layer16may be formed by such a reduction of the sacrificial interface layer13. Besides, an auxiliary initial interface layer41′ may be formed by such a reduction of the auxiliary sacrificial interface layer41.

According to an embodiment of the present invention, a deposition process of a sacrificial germanium layer31may be performed to form the initial interface layer16. The deposition process of the sacrificial germanium layer31may be performed under the reducing atmosphere14including a hydrogen gas.

The sacrificial germanium layer31may be deposited under the reducing atmosphere14including a large amount of the hydrogen gas. Since hydrogen has great reducing power, the sacrificial interface layer13and the auxiliary sacrificial interface layer41may be reduced when the sacrificial germanium layer31is deposited. A material remaining due to the reduction of the sacrificial interface layer13is qualified as the initial interface layer16for short. When the sacrificial interface layer13is formed of a metal oxide, the metal oxide may be reduced to a metal by hydrogen. For example, when the sacrificial interface layer13is formed, for example, a nickel oxide (NiO), nickel (Ni) may be formed by a reduction of the nickel oxide (NiO). The initial interface layer16may have high electronegativity. When the sacrificial germanium layer31is formed under the reducing atmosphere14, the sacrificial germanium layer31may be deposited at a low temperature. A material remaining due to the reduction of the auxiliary sacrificial interface layer41is qualified as the auxiliary initial interface layer41′ for short. When the auxiliary sacrificial interface layer41is formed of a germanium oxide, the germanium oxide may be converted into germanium by hydrogen. For example, the auxiliary initial interface layer41′ may be a germanium layer.

The sacrificial germanium layer31may include a doped germanium layer. The sacrificial germanium layer31may be a germanium layer doped with boron. The sacrificial germanium layer31may be formed, for example, by Chemical Vapor Deposition (CVD) or any other suitable method. The sacrificial germanium layer31may be formed using a hydrogen-containing germanium source gas and a hydrogen-containing dopant gas. The hydrogen-containing germanium source gas may include GeH4. The hydrogen-containing dopant gas may include borane (BH3), diborane (B2H6) or any combinations thereof. In this manner, the hydrogen-containing germanium source gas and the hydrogen-containing dopant gas, which are as compounds containing hydrogen, may promote the reduction of the sacrificial interface layer13.

As described above, when the sacrificial germanium layer31is formed, the sacrificial interface layer13may be reduced so that the initial interface layer16may be formed between the sacrificial germanium layer31and the dielectric layer12. The initial interface layer16has high electronegativity and high work function.

When the sacrificial germanium layer31is formed, the dielectric layer12is not exposed to the hydrogen-containing germanium source gas, the hydrogen-containing dopant gas and the reducing atmosphere14. In other words, the sacrificial interface layer13and the initial interface layer16prevent the dielectric layer12from being reduced.

Referring toFIG. 8C, a second conductive layer17may be formed on the sacrificial germanium layer31. The second conductive layer17may be or include a silicon-containing material. The second conductive layer17may be or include a silicon germanium (SiGe) layer or a boron-doped silicon germanium (SiGe) layer. The silicon germanium (SiGe) layer may be deposited using a silicon source gas and a germanium source gas. The boron-doped silicon germanium (SiGe) layer may be deposited using the silicon source gas, the germanium source gas and a boron source gas. The silicon germanium (SiGe) layer may use a hydrogen-containing gas such as H2as a reaction gas.

The second conductive layer17may be deposited at an elevated temperature, for example a temperature of approximately 400° C. When the second conductive layer17is deposited at the temperature of approximately 400° C., the sacrificial germanium layer31, the auxiliary initial interface layer41′ and the initial interface layer16react due to the thermal budget. For example, an interface layer32′ may be formed through a germanide reaction. The sacrificial germanium layer31, the auxiliary initial interface layer41′ and the initial interface layer16may be all consumed during the germanide reaction, thereby being completely converted into the interface layer32′. In other words, the interface layer32′ may be formed through a fully-germanide reaction of the sacrificial germanium layer31, the auxiliary initial interface layer41′ and the initial interface layer16. The interface layer32′ may be referred to as a fully-germanide interface layer (FUGE IL).

The interface layer32′ may be or include a germanide of a material whose electronegativity is high. For example, the interface layer32′ may be or include a nickel germanide, a cobalt germanide or a tungsten germanide.

Since the interface layer32′ includes a material whose electronegativity is high such as nickel, the interface layer32′ may have a high work function. The interface layer32′ may have the high work function of approximately 4.9 eV or higher. For example, a nickel germanide (NiGe) may have a high work function of approximately 5.2 eV. The nickel germanide (NiGe) may have a higher work function than the nickel silicide.

After the second conductive layer17is deposited, a thermal process may be further performed at a temperature of approximately 500° C. or lower if necessary. Hence, resistance of the interface layer32′ may decrease.

According to another embodiment of the present invention, the second conductive layer17may be formed by sequentially stacking a silicon layer and a silicon germanium layer. The silicon layer and the silicon germanium layer may be doped with a dopant, for example, boron. For example, a boron-doped silicon (Si) layer and a boron-doped silicon germanium (SiGe) layer may be stacked to form the second conductive layer17.

As described above, a stack structure of a first conductive layer11, the dielectric layer12, the interface layer32′ and the second conductive layer17that are formed through a series of processes may become a capacitor.

FIGS. 10A to 10Eare cross-sectional views illustrating a method for fabricating a DRAM capacitor in accordance with embodiments of the present invention. A sacrificial interface layer, a sacrificial layer, an initial interface layer, an interface layer, etc. shown inFIGS. 10A to 10Erefer to the aforementioned embodiments of the present invention.

Referring toFIG. 10A, an inter-layer dielectric layer52may be formed on a semiconductor substrate51. A storage node contact plug53coupled to a portion of the semiconductor substrate51may be formed to penetrate through the inter-layer dielectric layer52. The storage node contact plug53may be formed of any suitable material including a polysilicon, a metal, a metal nitride, or combinations thereof. Although not illustrated, a cell transistor and a bit line may be further formed before the inter-layer dielectric layer52is formed. The cell transistor may include a buried word line structure.

A bottom electrode54may be formed on the storage node contact plug53. The bottom electrode54may, for example, have a cylindrical shape. According to another embodiment of the present invention, the bottom electrode54may have a pillar shape. In an embodiment, the bottom electrode54may be formed of a metal nitride, such as, for example, a titanium nitride.

The bottom electrode54may be supported by first and second supporters55A and55B. The first supporter55A may be coupled to a bottom portion of the bottom electrode54. The second supporter55B may be coupled to a top portion of the bottom electrode54. The first and second supporters55A and55B may include a silicon nitride, a silicon carbide, or a combination thereof. The first supporter55A may also be an etch stop layer.

Referring toFIG. 10B, a dielectric layer56may be formed. The dielectric layer56may have a ZAZA stack structure. The dielectric layer56may cover the bottom electrode54and the first and second supporters55A and55B.

Referring toFIG. 10C, a sacrificial interface layer57may be formed on the dielectric layer56. The sacrificial interface layer57may be formed, for example, a nickel oxide. According to another embodiment of the present invention, the sacrificial interface layer57may be formed of a cobalt oxide or a tungsten oxide.

Referring toFIG. 10D, a sacrificial layer59may be formed at a reducing atmosphere58. The reducing atmosphere58may contain a hydrogen gas. The sacrificial layer59may include a silicon layer or a germanium layer. In an embodiment, the sacrificial layer59may be deposited using a compound gas containing hydrogen.

As the sacrificial layer59is formed under the reducing atmosphere58, an initial interface layer57′ may be formed by such a reduction of the sacrificial interface layer57. For example, the sacrificial interface layer57may be or include a nickel oxide, and the initial interface layer57′ may be or include nickel. In other words, the nickel may remain due to a reduction of the nickel oxide.

Referring toFIG. 10E, a top electrode60may be formed. The top electrode60may be or include a silicon germanium layer. When the top electrode60is formed, the sacrificial layer59and the initial interface layer57′ react due to the thermal budget. For example, an interface layer61may be formed through silicidation or a germanide reaction. The interface layer61may be a metal silicide or a metal germanide. The interface layer61may be a nickel silicide or a nickel germanide.

According to another embodiment of the present invention, the interface layer61of the DRAM capacitor may be formed of a metal-rich metal silicide.

According to another embodiment of the present invention, a method for forming the interface layer61of the DRAM capacitor may use a stack of a sacrificial interface layer and an auxiliary sacrificial interface layer. For example, the method for fabricating the DRAM capacitor may include the processes described above with reference toFIGS. 4A to 4C. Besides, the method for fabricating the DRAM capacitor may include the processes described above with reference toFIGS. 8A to 8C.

FIG. 11is a cross-sectional view of the DRAM capacitor in accordance with embodiments of the present invention.

Referring toFIG. 11, a pillar-type bottom electrode54′, a dielectric layer56′, an interface layer61′ and a top electrode60′ may be formed. The DRAM capacitor shown inFIG. 11may be fabricated by the method described above with reference toFIGS. 10A to 10E. However, we note that the pillar-type bottom electrode54′ may be formed by a method that is different from the method for forming the bottom electrode54shown inFIG. 10A.

According to the embodiments of the present invention, the interface layer may be formed between the dielectric layer and the top electrode using a material having a high electronegativity, whereby the leakage current may be greatly reduced. Thus, refresh characteristics of the DRAM may be improved.

According to the embodiments of the present invention, since the equivalent oxide layer thickness and capacitance are not affected, a sensing margin of the DRAM may be maintained and the reliability of the DRAM may be improved.

According to various embodiments of the present invention, an interface layer having a high work function while suppressing the reduction of a dielectric layer may be formed.

Also, according to various embodiments of the present invention, an interface layer may be formed between a dielectric layer and a top electrode using a material having a high electronegativity, whereby the leakage current of a capacitor may be reduced.

Finally, according to various embodiments of the present invention, a dielectric layer may be prevented from being reduced from a top electrode, whereby the capacitance and the leakage current may be improved.

While the present invention has been described with respect to the specific embodiments, it should be noted that the embodiments are for describing, not limiting, the present invention. Further, it should be noted that the present invention may be achieved in various ways through substitution, change, and modification, by those skilled in the art without departing from the scope of the present invention as defined by the following claims.