Patent Application
20060037942
This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 2004-0064648 filed on Aug. 17, 2004, the contents of which are hereby incorporated by reference in their entirety.
Ruthenium, including ruthenium alloys, such as ruthenium dioxide, may be used as a bottom electrode material of a capacitor for a semiconductor device. A ruthenium alloy may be defined as any composition where ruthenium is the main component. Ruthenium alloys, such as ruthenium dioxide, may have a lower surface resistance because of their conductivity, contrary to other materials, such as titanium oxide, tungsten oxide or tantalum oxide.
Conventionally, a ruthenium film may be deposited using a sputtering method or a CVD method, and afterward, some portion of the ruthenium film may be removed to form a bottom electrode by etching the ruthenium film. However, it may be difficult to etch a ruthenium film by conventional wet etch processes, using conventional etchants, including aqua-regia or a “piranha” etchant. A “piranha” etchant is a semiconductor industry-accepted term for a conventional wet chemical solution containing sulfuric acid and hydrogen peroxide, often used to clean substrates of organic contamination.
Another conventional solution for wet etching a ruthenium film is a solution including ceric ammonium nitrate, (NH4)2Ce(NO3)6, which can be used as a wet etchant or a chemical mechanical polish (CMP) slurry. However, ceric ammonium nitrate has several drawbacks. First, it may be difficult to control the removal rate of ruthenium because of ceric ammonium nitrate's high speed. Second, ceric ammonium nitrate may cause damage to processing machinery due to its high acidity (pH of about 1). Third, it may be difficult to control the pH of the wet etch solution because a precipitate is formed from the combination of cerium ions (Ce4+) and hydroxyl anions (OH−) and therefore it may also be difficult to control the selectivity between the ruthenium film(s) and other films.
Due to the above-mentioned problems with wet etching a ruthenium film, ruthenium films have also been etched using dry etch processes. However, dry etching ruthenium films may also have problems, including the formation of sharp cusps on a top surface of the ruthenium bottom electrode after node separation, recessing of the ruthenium bottom electrode and/or a loss of mold oxide, and a resultant loss of capacitance.
Example embodiments of the present invention are directed to a slurry for a chemical mechanical polishing (CMP) method for polishing a metal film, such as an ruthenium film, which provides a high removal rate selectivity of metal film to other films, a polishing method, for example, a CMP method, using the slurry, and a method of forming a surface for a capacitor using the polishing method.
Example embodiments of the present invention are directed to a slurry, a polishing method, and a method of forming a surface for a capacitor with improved removal rate selectivity and/or better pH control.
Example embodiments of the present invention are directed to slurry for a chemical mechanical polishing (CMP) method for a film including ruthenium, the slurry including an abrasive, an oxidizer, and at least one pH controller to control a pH of the slurry.
Example embodiments of the present invention are also directed to a chemical mechanical polishing (CMP) method for a ruthenium film formed on a semiconductor substrate, the method including preparing a slurry including an abrasive, an oxidizer, and at least one pH controller to control a pH of the slurry and performing chemical mechanical polishing (CMP) of the ruthenium film using the slurry.
Example embodiments of the present invention are also directed to a method for forming a surface for a capacitor including forming an etch stop layer on a semiconductor substrate, forming a mold oxide layer on the etch stop layer, patterning the mold oxide layer to define a region for the capacitor, forming a layer including ruthenium on the patterned mold oxide layer, forming a dielectric layer on the layer including ruthenium, and polishing the layer including ruthenium and the dielectric layer using a slurry including an abrasive, an oxidizer, and at least one pH controller to control a pH of the slurry.
In example embodiments of the present invention, the capacitor is one of a stacked, concave, or OCS capacitor.
The present invention will become more fully understood from the detailed description given below and the accompanying drawings, which are given for purposes of illustration only, and thus do not limit the invention.
It should be noted that these Figures are intended to illustrate the general characteristics of methods and devices of example embodiments of this invention, for the purpose of the description of such example embodiments herein. These drawings are not, however, to scale and may not precisely reflect the characteristics of any given embodiment, and should not be interpreted as defining or limiting the range of values or properties of example embodiments within the scope of this invention.
In particular, the relative thicknesses and positioning of layers or regions may be reduced or exaggerated for clarity. Further, a layer is considered as being formed “on” another layer or a substrate when formed either directly on the referenced layer or the substrate or formed on other layers or patterns overlaying the referenced layer.
In an example embodiment of the invention, a slurry for use in chemical mechanical polishing (CMP) may include an abrasive, an oxidizer, and/or a pH controller.
In an example embodiment, the abrasive may be ceria, silica (in any form, for example, colloidal or fumed silica), alumina, titania, angania, zirconia, germania or mixtures thereof.
In an example embodiment, the oxidizer may be or include periodic acid (H5IO6).
In an example embodiment, the pH controller may be or include an amine compound, for example, BHMT (Bis-(HexamMethylene)Triamine), TMAH (TetraMethyl Ammonium Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA (Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide) and/or choline salt. In other example embodiments, the pH controller may be potassium hydroxide.
In an example embodiment, the abrasive, for example, colloidal silica, may be from 0.01 to 30 (inclusive, as are all ranges disclosed and claimed herein) weight % of the CMP slurry, and more particularly, from 0.1 to 10 weight %, and more particularly, from 0.5 to 3.0 weight %.
In an example embodiment, the oxidizer, for example, periodic acid, may be from 0.1 to 5 weight % of the CMP slurry. In an example embodiment, a content of the oxidizer, for example, periodic acid, may be in a range from 2.5 to 5.0 weight % of a total weight of the slurry. In an example embodiment, a content of the oxidizer, for example, periodic acid, may be in a range from 0.1 to 2.0 weight % of a total weight of the slurry. In an example embodiment, a content of the oxidizer, for example, periodic acid, may be in a range from 0.1 to 1.0 weight % of a total weight of the slurry. In an example embodiment, a content of the oxidizer, for example, periodic acid, may be in a range from 0.1 to 0.5 weight % of a total weight of the slurry. In an example embodiment, a content of the oxidizer, for example, periodic acid, may be in a range from 0.25 to 0.5 weight % of a total weight of the slurry. In an example embodiment, a content of the oxidizer, for example, periodic acid, may be in a range from 0.5 to 1.5 weight % of a total weight of the slurry.
In an example embodiment, the pH of the CMP slurry is from 2 to 8 and more particularly, from 3.5 to 4.5. In an example embodiment, the pH of the CMP slurry is about 4. In another example embodiment, the pH of the CMP slurry is about 8.
In an example embodiment, a content of the colloidal silica is 0.5 weight % of a total weight of the slurry and a content of the periodic acid is 0.5 weight % of a total weight of the slurry. In an example embodiment, a content of the colloidal silica is 3 weight % of a total weight of the slurry and a content of the periodic acid is 0.5 weight % of a total weight of the slurry.
An example slurry according to the present invention includes colloidal silica and periodic acid. The periodic acid may act as an oxidizer of the ruthenium to form ruthenium dioxide on the surface of the ruthenium. The content range of the periodic acid may be from 0.1 weight % to 5 weight The content range of the periodic acid may be from 0.5 weight % to 1.5 weight %. The content range of the periodic acid may be from 0.1 to 5 weight The content range of the periodic acid may be from 2.5 to 5.0 weight %. The content range of the periodic acid may be from 0.1 to 2.0 weight %. The content range of the periodic acid may be from 0.1 to 1.0 weight %. The content range of the periodic acid may be from 0.1 to 0.5 weight %. The content range of the periodic acid may be from 0.25 to 0.5 weight %. The content range of the periodic acid may be from 0.5 to 1.5 weight %.
The colloidal silica may act as an abrasive. In addition to colloidal silica, other components such as ceria, alumina, titania, mangania, zirconia, germania or mixtures thereof can be used as an abrasive. The content range of the abrasive may be from 0.01 weight % to 30 weight %. The content range of the abrasive may be from 0.01 weight % to 1 weight %. The content range of the abrasive may be from 0.01 weight % to 1 weight % to raise the removal rate of other layers, including oxides, such as, Plasma-Tetra-Ortho-Silicate (TEOS), tantalum oxide (TaO), polysilicon, or silicon.
The CMP slurry may further include potassium hydroxide as a pH controller to increase the removal rate for ruthenium and decrease the removal rate for oxides, such as those mentioned above. In an example, the pH range may be from 2 to 8. In another example, the pH range may be from 3.5 to 4.5.
The removal rates of ruthenium, TEOS, TaO, and polysilicon were measured as the pH of slurry was varied. In this example, the main components were 0.5 weight % colloidal silica of 15 nm in diameter and 0.5 weight % periodic acid. In this example, the pH was changed by using potassium hydroxide. The results are shown in Table 1.
As shown in Table 1, the amount of potassium hydroxide may be increased to increase the pH of the CMP slurry. In sample No. 1, no potassium hydroxide is present. As shown in Table 1, the selectivity between ruthenium and other materials, like TEOS, TaO and polysilicon, may be controlled by changing the pH of the CMP slurry.
Another example slurry according to the present invention includes colloidal silica, periodic acid, and an amine compound, as a pH controller. The amine compound may increase the removal rate and selectivity between ruthenium and other materials, like TEOS, TaO, polysilicon, and silicon. The amine compound may be BHMT (Bis-(HexaMethylene)Triamine), TMAH (TetraMethyl Ammonium Hydroxide), TMA (TetraMethylAmine), TEA (TetraEthylAmine), HA (Hydroxylamine), PEA (PolyEthyleneAmine), CH (Choline Hydroxide) or choline salt. Other conditions may be the same as that of Example Slurry 1, except using an amine compound as a pH controller.
The removal rates of ruthenium, TEOS, tantalum oxide (TaO) and polysilicon were measured as the amine compound was varied. In this example, the main components were 0.5 weight % colloidal silica of 15 nm in diameter, 0.5 weight % periodic acid and an amine compound that makes the pH of the slurry either 4 or 8. The results are shown in Table 2.
As shown in Table 2, the amine compound may be varied to increase the selectivity of the CMP slurry. In sample No. 1, no amine compound or oxidizer was present. As shown in Table 2, the selectivity between ruthenium and other materials, for example, TEOS, TaO and polysilicon, may be controlled by changing the amine compound of the CMP slurry. As shown in Table 2, TMAH and TMA exhibit better results.
The removal rates of ruthenium, TEOS, tantalum oxide (TaO) and silicon were measured as the pH of slurry changed by changing the amount of TMAH and TMA. The main components were 0.5 weight % colloidal silica of 15 nm in diameter, 0.5 weight % periodic acid and amine compound that makes the pH of the slurry either 4 or 8. The results are shown in Table 3.
As shown in Table 3, the removal rate of ruthenium increased as pH increased. Moreover, Table 3 shows that not only the removal rate of ruthenium, but also the removal rate of other layers, for example, TaO and silicon, can be controlled by changing the pH of the slurry.
The removal rates of ruthenium, TEOS, tantalum oxide (TaO) and silicon were measured as the amount of colloidal silica was varied. The main components were colloidal silica of 15 nm in diameter, 0.5 weight % periodic acid and TMAH that makes the pH of the slurry about 4. The results are shown in Table 4.
As shown in Table 4, the removal rate of TEOS increased, whereas the removal rate of ruthenium was not significantly affected as the amount of colloidal silica increased. In an example embodiment, a suitable amount of colloidal silica may be about 3 wt % taking the removal rate of silicon and the selectivity between ruthenium and TEOS into consideration.
A method of forming a capacitor using ruthenium or ruthenium alloy as a bottom electrode in accordance with an example embodiment of the present invention is described in conjunction with
As shown in
As shown in
In an example embodiment, the ruthenium film 20 may be a ruthenium alloy. In an example embodiment, the ruthenium film 20 may be deposited by sputtering, chemical vapor deposition (CVD), or atomic layer deposition (ALD), all techniques commonly known in the semiconductor processing art.
As also shown in
In an example embodiment, the dielectric layer may include tantalum (Ta), hafnium (Hf), aluminium (Al), titanium (Ti), strontium titanate (Sb—Ti) or oxides (STO), barium strontium titanate (BST) or oxides or combinations thereof.
In an example embodiment, the removal rate selectivity of the one or more of the slurries may be greater than or equal to 5:1. In other example embodiments, the removal rate selectivity may be greater than or equal to 20:1 or 50:1.
As shown in
Although, as shown in
Another method of forming a capacitor using ruthenium or ruthenium alloy as a bottom electrode in accordance with an example embodiment of the present invention is described in conjunction with
As shown in
As shown in
In more detail, in
In accordance with an example embodiment of the present invention, the adhesion layer 50 may undergo an etchback process until the adhesion spacer 50a remains on only the sidewall of the concave pattern 38a. Thus, only the adhesion spacer 50a and the contact 22 are exposed within the storage node hole 38h.
As shown in
The first conductive layer 60 can be formed by depositing a platinum-group metal, a platinum-group metal oxide, or a material having a perovskite structure using a PVD or CVD method. For example, the first conductive layer 60 can be formed of Pt, Ru, Ir, RuO2, IrO2, SrRuO3, BaSrRuO3, or CaSrRuO.
In an example embodiment, as shown in
The first conductive layer 60 and sacrificial layer 62 on the concave pattern 38a may be etched back or removed by chemical mechanical polishing (CMP) until the upper surface of the concave pattern 38a is exposed. Consequently, the first conductive layer 60 may be divided into a plurality of lower electrodes 60a as shown in
In the storage node hole 38h, the residual portion 62a of the sacrificial layer 62 may remain on the lower electrode 60a. The residual portion 62a of the sacrificial layer 62 may be removed by ashing or wet etch, thus obtaining a resultant structure as shown in
In an example embodiment, the photoresist layer or oxide layer forming the sacrificial layer 62 can be removed at an excellent selectivity with respect to SiON forming the anti-reflection layer pattern 36a in the upper portion of the concave pattern 38a and a conductive material forming the lower electrode 60a. Therefore, when the residual portion 62a of the sacrificial layer 62 is removed, other portions on the semiconductor substrate 10 are not damaged.
Referring to
In an example embodiment, a second conductive layer 80 may be formed on the dielectric layer 70, thus forming an upper electrode of a capacitor. The second conductive layer 80 may be formed by depositing a platinum-group metal, a platinum-group metal oxide, TiN, or a material having a perovskite structure using the PVD method, the CVD method, the MOD method, or the ALD method. For example, the second conductive layer 80 can be formed of Pt, Ru, Ir, RuO2, IrO2, TiN, SrRuO3, BaSrRuO3, or CaSrRuO3.
In an example embodiment, the first capping layer 124 may cover the bit line 122. The bit line 122 may be formed as a first conductive layer connected to an active region of the semiconductor substrate 100 through interlayer dielectric films 110 and 120 on the substrate 100 on which cell array devices 102, for example, cell array transistors are formed. A first insulating layer may be formed on the entire surface of the resultant structure using a first insulating material such as Si3N4. The first insulating material may be anisotropically etched to form first capping layer 124.
In an example embodiment, an OCS capacitor may further include a first interlayer dielectric film 130 and a second capping layer 134. The first interlayer dielectric film 130 may be formed by forming an insulating film such as an oxide film by chemical vapor deposition (CVD) on the entire surface of the resultant structure using a second insulating material having an etch rate different from that of the first insulating material. The first interlayer dielectric film 130 may be planarized by a chemical mechanical polishing (CMP) process with the first capping layer 124 acting as an etch stop layer. The second capping layer 134 may be formed by forming a second insulating layer on the entire surface of the resultant structure using a third insulating material, for example, Si3N4. As shown in
In an example embodiment, an OCS capacitor may further include a plug e1 for forming the storage contact of the cell array region and forming wiring layers e2, e3 and e4 of the peripheral circuit region. In an example embodiment, a second conductive layer may be formed by depositing a metal having excellent filling properties, for example, tungsten (W) or TiN, using CVD.
In an example embodiment, an OCS capacitor may further include a second interlayer dielectric film 140 only in the peripheral circuit region. The second interlayer dielectric film 140 may be formed by forming an insulating film such as an oxide film on the entire surface of the resultant structure and removing the insulating film by etching the insulating film in the cell array region using the second capping layer 134 as an etch stop layer.
In an example embodiment, an OCS capacitor may further include a storage electrode 142 formed to electrically connect to the active region of the substrate 100 through the plug e1 by forming a conductive layer such as a doped polysilicon layer in the cell array region and patterning the conductive layer. It is also possible to form a storage electrode having a structure in which a TiN film and a polysilicon layer are stacked by forming the TiN film and the polysilicon layer and patterning the TiN film and polysilicon layer.
As shown in
Although example embodiments of the present invention are directed to slurries, polishing methods using the slurries, and method of forming a surface of a capacitor using the slurries, other etching materials may also be used, either in place of, or in addition to the slurries described herein, including, but not limited to etchants that includes a mixture of NH4F and HF (commonly referred to in the semiconductor processing art as “LaI solutions”) and mixtures of NH3, H2O2 and deionized water (commonly referred to in the semiconductor processing art as an “sc1 solution”).
Although example embodiments of the present invention are directed to polishing ruthenium films, other films, for example, Pt, Ir, RuO2, IrO2, SrRuO3, BaSrRuO3, or CaSrRuO, may also be polished.
Although example embodiments of the present invention are directed to slurries, slurries with particular classes of components (abrasive, oxidizer, and/or pH controller, etc.), slurries with particular pHs (4, 8, etc), slurries with particular components (colloidal silica, periodic acid, BHMT, etc.), slurries with particular weight percentage ranges of components, slurries with particular weight percentages of components, polishing methods using the slurries, and methods of forming a surface of a capacitor using the slurries, each of the above features may be mixed, matched, and/or interchanged with other features to create numerous, other example embodiments of the present invention.
It will be apparent to those skilled in the art that other changes and modifications may be made in the above-described example embodiments without departing from the scope of the invention herein, and it is intended that all matter contained in the above description shall be interpreted in an illustrative and not a limiting sense.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2004-0064648 | Aug 2004 | KR | national |
