JPH1056153A - Thin-film capacitor and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small thin-film capacitor with large capacitance suitable for a storing capacitor in DRAM or a bypass capacitor in GaAs MMIC. SOLUTION: A thin-film capacitor has a layer 13 that contains a material obtained by reducing an oxide material in platinum group, a layer 12 that contains non-platinum group metal, and a then film 14 that contains a non- platinum group metal oxide obtained by reducing the non-platinum group metal between these layers 12 and 13. Then, the manufacturing step includes a step for forming a laminated structure made up of a non-platinum group metal (Ta) layer and a platinum group metal oxide (RuO2 ) layer, and a step for heating the laminated structure above a temperature of thermal decomposition for the oxide material in the platinum group element and forming a thin film that contains a non-platinum group metal oxide (Ta2 O5 ) between these layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a thin film capacitor used as a capacitor for retaining a charge in a DRAM, a bypass capacitor of a GaAs MMIC, and a method of manufacturing the same.

[0002]

2. Description of the Related Art DRAM which is a representative of a semiconductor integrated circuit
However, as the degree of integration has been increasing year by year, the device size has been shrinking, but in view of the sensitivity of the sense amplifier and the bit line capacitance, the capacitance of the thin film capacitor that accumulates electric charges must be maintained at 30 PF or more. Must. Capacitance C of the thin film capacitor is given by _{C = ε o ε r A /} t. Here, ε _o is the dielectric constant in a vacuum, ε _r is the relative dielectric constant of the dielectric, A is the effective area, and t is the thickness of the dielectric. Therefore, in order to keep the capacitance C at a certain level, the effective area A
The increase or, or to reduce the thickness t, there is no choice but to increase the specific dielectric constant epsilon _r of the dielectric.

As a method of miniaturizing a thin film capacitor of a DRAM to date, a method of increasing the effective area A and decreasing the thickness t has been adopted. As a specific example of this, a fin-type stack is used. A three-dimensional structure called a structure is employed. Further, SiO ₂ -based materials have been used as dielectrics.

[0004]

However, DRA
If the integration degree of M is 256 Mbits or more, it becomes difficult to secure a desired capacitance value even if the above-mentioned three-dimensional structure is adopted. In the case of SiO ₂ -based thin films, the equivalent thickness has already reached the limit value of about 50 mm, which is considered to be the limit value. To increase the capacitance value, use a dielectric with a large relative dielectric constant as a material for the thin film It is desired to do.

As a dielectric having a large relative dielectric constant, a thin film of a monometal paraelectric oxide such as Ta ₂ O ₅ has been studied. These monometal paraelectric oxides are formed by a method of sputtering a metal or metal oxide target in an oxidizing atmosphere. However, since it is difficult to uniformly form a thin metal oxide film on the surface of a device having considerable unevenness, it has become difficult to adapt to a highly integrated LSI that has advanced in three dimensions. A method of forming a metal oxide film by a thermal CVD method is also being studied, but there is a problem that a thin film formed by this method is inferior in insulation to a thin film formed by a sputtering method.

When a quasi-microwave GaAs MMIC up to the L band used in a cellular phone or the like is used, a bypass capacitor having a capacitance of 100 PF or more is required.
Due to the high chip cost of the MMIC, it was difficult to use on-chip capacitors using SiN as the dielectric. Therefore, when using a GaAs MMIC, the package requires pins to be connected to an external bypass capacitor, which increases the size. The size of the external capacitor and package increases the mounting area.

Accordingly, an object of the present invention is to provide a small-sized and large-capacity thin-film capacitor which enables high integration of a DRAM and on-chip quasi-microwave to a GaAs MMIC, and a method of manufacturing the same.

[0008]

A thin film capacitor according to the present invention which solves the above-mentioned problems of the prior art comprises a layer containing a platinum group element, a layer containing a metal of a non-platinum group element, and a layer formed between these layers. A dielectric thin film made of an oxide of a metal of the non-platinum group element. The thin film capacitor of the present invention includes a step of forming a laminated structure of a layer containing a metal of a non-platinum group element and a layer containing an oxide of a platinum group element, and a layer containing a platinum group element by heating the laminated structure. Forming a dielectric thin film made of an oxide of the non-platinum group metal in the middle of the layer containing the non-platinum group metal.

[0009]

According to a preferred embodiment of the present invention, the metal of the non-platinum group element is a metal whose oxide forms a monometallic paraelectric oxide; Hf, Y, Al, Zr
Including at least one of the above, the oxide of the metal of the platinum group element is a non-platinum group element of the platinum group element and the metal of the non-platinum group element, which are more likely to form an oxide than the platinum group element. Consist of combinations.

[0010]

FIG. 1 is a sectional view showing the structure of a thin film capacitor according to one embodiment of the present invention, in which 11 is a semiconductor substrate, 12 is a metal tantalum (Ta) film formed on this semiconductor substrate,
Reference numeral 13 denotes a film containing ruthenium, in which ruthenium (Ru) of a platinum group element and its conductive oxide (RuO ₂ ) are mixed, or only ruthenium, and 14 denotes an electrically insulating tantalum oxide (Ta ₂ O _5). ) Thin film, 15 is an aluminum (Al) electrode. A film 13 containing conductive ruthenium, an insulating tantalum oxide (Ta ₂ O ₅ ) thin film 14 having a thickness of about 1000 mm,
Metal-insulator-metal is formed by the metal Ta film 12.
A thin film capacitor having an Insulator-Metal (MIM) structure is formed.

FIG. 2 is a sectional view showing a method of manufacturing the thin film capacitor according to one embodiment of the present invention shown in FIG. First,
As shown in FIG. 2A, a 4000 ° Ta film 12 is formed on a semiconductor substrate 11 using a DC magnetron sputtering apparatus in a 100% Ar gas using a tantalum (Ta) target at 500 W power.

Next, as shown in (B), using a DC magnetron sputtering apparatus, 50% oxygen (O ₂ ) and 50%
A RuO ₂ film 13 ′ having a thickness of 2000 ° is formed on the Ta film 12 with a power of 500 W in a mixed gas of argon (Ar) and a ruthenium (Ru) target.

Subsequently, as shown in FIG.
mal Anealing (RTA) equipment in nitrogen (N ₂ ) atmosphere
A heat treatment is performed to maintain the sample at 900 ^° C. for 10 seconds. By this heat treatment, oxygen is separated from a part of Ru in the RuO ₂ film 13 ′, and accordingly, a part of the Ru oxide film is changed to Ru of the metal, and the metal and the conductive oxide thereof are separated. A mixed Ru / RuO ₂ film is formed. At the same time, oxygen separated from Ru enters the surface region of the Ta film 12, and a thin film 14 of Ta oxide (Ta ₂ O ₅ ) having a thickness of about 1000 ° is formed there. Depending on the thickness of the RuO ₂ film 13 ′ and the heat treatment conditions, the RuO ₂ film may be entirely changed to metal ruthenium.

The heat treatment temperature of 900 ^° C. has a boiling point of
Although the temperature is quite high for the Ta element with a relatively low value of 1457 ± 10 ^oC , its surface is closed by a film containing ruthenium, so even if the Ta element has a relatively low boiling point, Can not be dissipated to the outside through a membrane containing.

Next, as shown in FIG. 1D, a mask 15 made of a circular Al thin film having a diameter of 10 μm is formed on the ruthenium-containing film 13, and the ruthenium-containing film 13 is formed by reverse sputtering using the mask 15. By removing unnecessary portions of the outer peripheral portion of the above, a thin film capacitor having the structure shown in FIG. 1 is formed.

The thin film capacitor manufactured as described above exhibited good electrical characteristics such as a capacitance of 0.72 μF / cm ² and a dielectric loss of 1 × 10 ³ . Ta ₂ O ₅ thin film is 1000Å thick
When the relative dielectric constant was calculated, a value of 25 was obtained.

In the above embodiment, the method of forming the RuO ₂ film 13 ′ by the reactive sputtering method has been exemplified. However, it is also possible to generate this RuO ₂ film 13 ′ by applying MOCVD using Ru (DPM) ₃ as a CVV material, and in this case, good step coverage can be obtained.

Further, ruthenium (Ru) is used as a platinum group metal.
The configuration using is exemplified. However, when platinum (Pt) is used as the platinum group metal and the PtO ₂ film of the oxide is formed on thallium, 500 ^° C. is lower than that of the RuO ₂ film.
By performing the heat treatment at a temperature of C to 600 ^° C., a thallium oxide film can be formed immediately below the heat treatment, and damage to the semiconductor substrate and the like due to the heat treatment can be reduced.

Further, the oxides of Ru and Pt are not limited to RuO ₂ and PtO ₂ but may be oxides represented by the structural formulas of RuO and PtO. Similarly, oxides of other platinum group metals (M) such as Rh, Os, and Ir
It is also possible to form a (MOx) film on a metal of a non-platinum group element and oxidize a part of the metal of the non-platinum group element directly thereunder to form a dielectric. Since the oxide of the platinum group element has conductivity similarly to the case of ruthenium, a layer in which a metal and its oxide are mixed can be used as a part of the electrode.

In addition, the configuration using a Ta oxide as a single metal paraelectric oxide having a large relative dielectric constant has been exemplified.
A configuration using an oxide such as i, Hf, Y, Al, or Zr can also be used. As the combination of the platinum group element and the metal of the non-platinum group element, a combination in which the metal of the non-platinum group element easily forms an oxide as compared with the platinum group element is selected.

Further, the configuration in which a layer of an oxide of a platinum group element is formed on a metal film of a non-platinum group element and heat-treated is exemplified. However, if necessary, a configuration in which the upper and lower relations are reversed and a heat treatment is performed by forming a metal film of a non-platinum group element on the oxide layer of the platinum group element may be adopted.

Further, the configuration in which the thin film capacitor of the present invention is formed on a semiconductor substrate has been exemplified. However, the thin film capacitor of the present invention may be formed of a semiconductor substrate on which an insulating film is formed, or a ceramic substrate, a ferrite substrate or any other suitable electronic material. On the substrate.

[0023]

As described in detail above, the thin-film capacitor of the present invention is characterized in that a laminated structure of a non-platinum group metal layer such as tantalum and a platinum group element oxide layer is heated by heating both layers. Since a thin film of tantalum oxide or the like is formed between the layers, such a thin film can be formed uniformly on the surface of a device such as a DRAM or a quasi-microwave GaAs MMIC having considerable unevenness. This is because, unlike the conventional case where a thin film of tantalum oxide or the like is directly formed on the surface of the device by sputtering or the like, a relatively thick tantalum layer and a layer of a platinum group element oxide are sputtered. This is because a thin film of oxide having a uniform thickness can be formed by temporarily oxidizing only a part of the surface of the tantalum layer by heat treatment for a short time after the device is once laminated on a device surface having considerable unevenness.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a thin film capacitor according to one embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing the thin film capacitor.

[Explanation of symbols]

11 semiconductor substrate 12 Ta film 13 film 13 'Ru0 ₂ film 14 of tantalum oxide containing ruthenium (Ta ₂ O ₅₎ film 15 Al electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication H01L 21/822

Claims (4)

[Claims] A layer containing a platinum group element formed by reducing an oxide of a platinum group element; a layer containing a metal of a non-platinum group element;
A thin film containing an oxide of the metal of the non-platinum group element formed by oxidizing the metal of the non-platinum group element interposed between these layers. 2. The thin film capacitor according to claim 1, wherein the metal of the non-platinum group element is a metal containing at least one of Ta, Ti, Hf, Y, Al, and Zr. 3. A step of forming a laminated structure of a layer containing a metal of a non-platinum group element and a layer containing an oxide of a platinum group element, wherein the laminated structure is at or above the thermal decomposition temperature of the oxide of the platinum group element. The platinum group element oxide is reduced by heating to form a layer containing the platinum group element, and the metal of the non-platinum group element is oxidized to form a layer containing the platinum group element and the non-platinum group. Forming a thin film containing an oxide of the metal of the non-platinum group element between the layer and the layer containing the elemental metal. 4. The method according to claim 3, wherein the metal of the non-platinum group element is a metal containing at least one of Ta, Ti, Hf, Y, Al, and Zr. Method.