DE102008013513B4 - Dielectric component with high relative permittivity, its use and crystalline substrate with integrated circuits - Google Patents

Abstract

Component having at least one dielectric lanthanum-strontium-nickel oxide component (LSNO component), wherein
the device is an active or passive semiconductor device or a capacitive device;
wherein the at least one LSNO component has the composition La _2-x Sr _x NiO ₄ , and
where 0 <x ≤ 0.5 and above 10 MHz, the relative permittivity of ε _r ≥ 8,000.

Description

The invention relates to a lanthanum-strontium-nickel oxide (LSNO) component, in particular an LSNO layer or an LSNO plate, with dielectric properties. Furthermore, the invention relates to components with LSNO components and their use.

According to Moore's Law, which is now considered a "roadmap" for the semiconductor industry, an attempt is being made to increase the performance of integrated circuits. Accordingly, in addition to solutions for further miniaturization of integrated circuits, materials with relatively high relative permittivities are intensively researched worldwide, since the electrical permittivity of the currently used silicon compounds lies only in the range of ε _r ≈ 4-8. Interesting are such materials on the one hand for energy storage and on the other hand for electronic circuits.

The use of dielectric materials to increase the capacitance of a capacitor is known and widely used. The materials used so far can be roughly divided into three categories. The first category includes materials whose dielectric properties are relatively independent of temperature and frequency. However, the relative permittivity of these materials is rather low (ε _r ≈ 5.5-25). A prominent member of this group is HfO ₂ (ε _r ≈ 25), which will be implemented in the future as a high-k gate oxide in integrated circuits. The second category includes ferroelectric materials (eg BaTiO ₃ ), whose relative permittivity is very high (ε _r ≈ 10 ³ - 10 ⁴ ) but has pronounced temperature dependence. The last category includes novel materials that on the one hand have extremely high relative permittivities (ε _r ≈ 10 ⁴ - 10 ⁶ ), but which are also constant over a wide temperature and frequency range. An important representative of this group is CaCu ₃ Ti ₄ O ₁₂ (CCTO), which has been the focus of scientific interest since 2001 and whose application is being vigorously investigated - CC Homes, T. Vogt, SM Shapiro, S. Wakimoto, and AP Ramirez , Science 293, 673 (2001); S. Krohns, P. Lunkenheimer, SG Ebbinghaus, and A. Loidl, Appl. Phys. Lett. 91, 022910 (2007); Kant, T. Rudolf, F. Mayr, S. Krohns, P. Lunkenheimer, SG Ebbinghaus, and A. Loidl, Phys. Rev. B 77, 045131 (2008); or P. Lunkenheimer, R. Fichtl, SG Ebbinghaus and A. Loidl, Phys. Rev. B 70, 172102 (2004). One problem here is the decline in relative permittivity to much smaller values at frequencies in the MHz-GHz range - cf. the corresponding values in 1 for CCTO.

T. Park was in 2005 in Phys. Rev. Lett. (PRL 94, 017002 (2005)) published measurements up to 500 kHz on LSNO (La _2-x Sr _x NiO ₄ ) with Sr dopants of x = 1/3. It also pointed to an exceptionally high relative permittivity and discussed possible causes for this effect.

M. Kato et al .: Two-dimensional antiferromagnetic correlation with spin 1/2 in magnetic susceptibility of (La, Sr) ₂ NiO ₄ , in: Physica C, Vol. 176 (1991) pp. 533-540, discloses an LSNO material with an x value in the range of 0 to 0.325.

RJ Mcqueeney et al .: Phonon densities of states of La _2-x Sr _x NiO ₄ : Evidence for strong electron-lattice coupling. (abstract) CAPLUS (online). Accession No. 1999: 418431, discloses an LSNO material with an x value of 1/8.

US 2007/0 180 689 A1 such as US 2007/0 228 285 A1 disclose substrates coated with LSNO material.

It is an object of the invention to provide a device, a use of a device and a crystalline substrate with a dielectric material of high relative permittivity.

This object is achieved with the features of claim 1, 2 and 11, respectively. Advantageous embodiments are the subject of the dependent claims.

As exemplified above for some dielectrics, in the known dielectrics used in semiconductor fabrication, the relative permittivities over the entire frequency range (1 Hz to 1 GHz) are generally very low (ε _r <1,000). Moreover, in all known dielectrics, there is a large decrease in relative permittivity with increasing frequency, especially at frequencies above 1 MHz, as is typical in US Pat 1 shown for CCTO.

It has surprisingly been found that La2-xSrxNiO4 (lanthanum-strontium-nickel oxide - hereinafter referred to as LSNO) has huge relative permittivities over a wide frequency range over a wide frequency range for values in the range of x <x≤0.5. In contrast to all known dielectrics and thus contrary to the previous doctrine, even at frequencies above 10 MHz, in particular up to the gigahertz range (at room temperature), relative permittivities εr of more than 8,000 result. Thus, LSNO is predestined for applications in modern electronics in ultra-high frequency applications. Due to the exceptional relative permittivity, which reaches values> 10 ⁴ at gigahertz and room temperature, this material is particularly suitable for applications in diodes, capacitors and integrated circuits. But also in low frequency applications, especially in static energy storage or at For low frequency converter or rectifier applications, LSNO is particularly suitable at values of x in a range of 0 <x ≤ 0.3 as an alternative to, for example, CCTO due to the extremely high relative permittivity of ε _r ≥ 25,000.

Particularly in the range of x below 0.3, a significant increase in the relative permittivity and an expansion of the high values beyond the MHz range (> 10 MHz) could be achieved. Significantly, ε _r increases by x ≈ 0.125 (0.05 ≤ x ≤ 0.2), which could not have been expected because La ₂ NiO ₄ (x = 0) is not a dielectric with a large or exceptional diel. Permittivity distinguishes. Even with oxygen-doped LNO (La ₂ NiO _{4 + Δ} with Δ> 0), no significant relative permittivity ε _r could be expected which would have led to such values at La _2-x Sr _x NiO ₄ (x ≈ 0.125).

The advantageous embodiments specified in the subclaims preferably relate to values of ε _r at room temperature (300 ° K).

Advantageously, an LSNO crystal (polycrystalline or monocrystalline) of La _2-x Sr _x NiO _{4 is} either formed flat or sawed out of a crystal block in the form of thin substrates. On this substrate, semiconductor elements can be formed, for example, in thin-film technology, as it is known from semiconductor manufacturing using silicon wafers accordingly. On the LSNO substrate, (poly) crystalline layers can be epitaxially deposited, for example Si layers of silane precursors. Due to the agreement in the crystal lattice structure, high-quality crystalline layers grow on the LSNO substrate. Alternatively, such an LSNO substrate is provided as small, thin platelets or foil which are useful in the manufacture of capacitors or accumulators. With respect to the design of the LSNO substrate, the embodiments for the LSNO component apply accordingly.

The component advantageously has at least one LSNO layer as the at least one dielectric lanthanum-strontium-nickel oxide component (LSNO component).

Examples of an active or passive semiconductor component or a capacitive component are a diode, a memory element, a battery element, an energy store or a capacitor.

Preferably, the relative permittivity of the LSNO component is ε _r ≥ 15,000, ε _r ≥ 20,000 or ε _r ≥ 25,000. In a frequency range of 10 MHz to 3 GHz or 100 MHz to 1 GHz, the relative permittivity of the LSNO component ε _r ≥ 8,000, ε _r ≥ 10,000, ε _r ≥ 15,000, ε _r ≥ 20,000 or ε _r ≥ 25,000 is advantageous.

The LSNO component is advantageously an LSNO crystal, in particular an LSNO monocrystal or polycrystal.

In a further embodiment, the LSNO component is a layer produced by deposition, in particular an amorphous, polycrystalline or microcrystalline layer. Preferably, the LSNO layer is deposited on a substrate, in particular on a semiconductor substrate, a wafer substrate, a metal substrate or a metal foil. In the case of an LSNO substrate, this is advantageously a wafer, in particular with integrated circuits. In particular, the LSNO substrate is a monocrystalline or polycrystalline material.

According to one aspect of the invention, a component, in particular a semiconductor component, with a lanthanum-strontium-nickel oxide component (LSNO component) is used for high-frequency applications in the range above 1 MHz, in particular above 10 MHz or 100 MHz.

The only 1 shows the frequency dependence of the relative permittivity of CaCu ₃ Ti ₄ O ₁₂ at room temperature (full _circles ) and La _15/8 Sr _1/8 NiO ₄ (open symbols) for different temperatures. The solid lines are simulated curves that are calculated on the basis of an equivalent circuit diagram for LSNO and can describe the behavior of LSNO in a very good approximation. The simulation method used here is described in P. Lunkenheimer, R. Fichtl, SG Ebbinghaus, and A. Loidl, Phys. Rev. B 70, 172102 (2004).

In the present text, the dielectric constant ε = ε _r · ε _{0 is referred} to as permittivity according to the newer convention. Accordingly, the relative dielectric constant ε _r as relative permittivity.

In the preferred embodiment of the invention La _15/8 Sr _1/8 NiO ₄ single crystals are used, which can be produced by zone melting. The starting material required for this purpose is synthesized as follows: Stoichiometric amounts of the commercially available pulverulent precursors La ₂ O ₃ , NiO and SrCO ₃ are mixed and sintered at about 1100 ° C. The resulting ceramic is again ground, mixed and then sintered. This process is repeated three times and finally the powder is pressed into a cylindrical shape. In a mirror oven, this cylinder is melted zone by zone and crystallized by means of a seed crystal. In addition to monocrystalline samples, polycrystalline samples can also be produced in this way (eg without zone melting process).

It is also possible to synthesize LSNO thin films, for example by means of pulsed laser deposition (PLD). In addition, LSNO with appropriate stoichiometry can also be made using chemical vapor deposition (CVD) or sputtering techniques. Especially in integrated semiconductor applications, such thin-film deposition methods can be integrated much better into existing production structures and systems.

In the preferred embodiment, a disk is sawn out of the single crystal and contacted on both sides with conductive silver for the preparation of a prototypical capacitor with LSNO as a dielectric. The dielectric properties were determined using an Alpha-A High Performance Frequency Analyzer from Novocontrol Technologies and an Agilent E4991A RF Impedance / Material Analyzer from Agilent Technologies in the frequency range 1 Hz to 1 GHz. The measured variable obtained is the capacitance, which is converted into the relative permittivity ε _r on the basis of the geometry of the measured sample.

In 1 is the relative permittivity ε _r of La _15/8 Sr _1/8 NiO ₄ at different temperatures and compared to that of CCTO at room temperature (300 ° K) frequency dependent applied. At low frequencies, in the range from a few hertz to kilohertz, this value is called "colossal relative permittivity" in analogy to the colossal magnetoresistance. The transition from the colossal relative permittivity to a significantly lower relative permittivity is clearly visible (ε _r ≈ 100-300) to recognize. At higher temperatures, this so-called relaxation step shifts to higher frequencies and thus gives colossal dielectric behavior up to about 1 MHz at CCTO and up to about 300 MHz at La _15/8 Sr _1/8 NiO ₄ at room temperature. An extrapolation based on the fit curves shown can be expected huge values of relative permittivity well into the GHz range.

The capacitance of the LSNO capacitor reached 2 nF at 100 MHz. In view of the simple geometry of the test capacitor used, this is an extremely high value. For CCTO only 10 pF (at 100 MHz) was achieved with the same capacitor dimensions. In contrast, the SiO ₂ commonly used in the semiconductor field would lead to values around 0.5 pF for this capacitor geometry.

This surprising material property of LSNO in the ultra-high frequency range thus predestines it for the abovementioned applications, for example in the case of capacitive components with LSNO as the dielectric. These are due to the mentioned properties of LSNO for industrial application of paramount importance. They allow an increase in performance over previously available components, eg. B. with respect to the storable energy in relation to mass and size and with respect to the further miniaturization of electronic circuits at frequencies up to GHz.

Capacitive devices with LSNO dielectric are of particular importance for use in modern electronics and electrical engineering because of the exceptional dielectric properties of this material, since LSNO has "colossal" relative permittivity at room temperature down to the gigahertz range compared to other materials. Furthermore, the material can be produced both monocrystalline and polycrystalline. Based on single crystals, various capacitors have already been prepared with LSNO demonstrating the superior properties. Furthermore, it is important that in addition to LSNO ceramics even thin LSNO films (with similar stoichiometry) could be successfully synthesized by PLD.

In the above-mentioned article Phys. Rev. Lett. (PRL 94, 017002 (2005)), high relative permittivities were observed for measurements up to 500 kHz on LSNO with Sr dopants of x = 1/3. Contrary to the published data, however, it has been found with the present invention that for Sr dopants with x≈1 / 8 an extraordinary relative permittivity is achieved at room temperature and at frequencies up to gigahertz, which is of great interest for industrial application.

But also an application of solid state capacitors is conceivable for this purpose. La _2-x Sr _x NiO ₄ with x≈1 / 8 is an excellent candidate for this because of its extremely high relative permittivity, which leads to a large capacitance of the components with moderate mass and size at the same time and due to the constant behavior of this material size in a broad range Temperature and frequency range.

Claims (12)

A device comprising at least one lanthanum-strontium-nickel oxide (LSNO) dielectric component, the device being an active or passive semiconductor device or a capacitive device; wherein the at least one LSNO component has the composition La _2-x Sr _x NiO ₄ , and wherein 0 <x ≤ 0.5 and above 10 MHz the relative permittivity of ε _r ≥ 8,000. Use of a component with a lanthanum-strontium-nickel oxide component (LSNO component) for high-frequency applications in the range above 1 MHz, 10 MHz or 100 MHz; wherein the LSNO component has the composition La _2-x Sr _x NiO ₄ , and wherein 0 <x ≤ 0.5 and above 10 MHz, the relative permittivity of ε _r ≥ 8,000. Component according to claim 1 or use of a component according to claim 2, wherein 0 <x ≤ 0.3 and the relative permittivity ε _r ≥ 15,000. Component according to claim 1 or use of a component according to claim 2, wherein the relative permittivity of the LSNO component ε _r ≥ 10,000. Component according to claim 1 or use of a component according to claim 2, wherein the relative permittivity of the LSNO component ε _r ≥ 8,000 in a frequency range of 10 MHz to 10 GHz is present. Component according to claim 5 or use of a component according to claim 5, wherein in the frequency range from 10 MHz to 10 GHz, the relative permittivity of the LSNO component ε _r ≥ 10,000, ε _r ≥ 15,000, ε _r ≥ 20,000 or ε _r ≥ 25,000. A component according to claim 1, 4, 5 or 6 or use of a component according to claim 2, 4, 5 or 6, wherein 0.05 ≤ x ≤ 0.4, 0.05 ≤ x ≤ 0.3, 0.1 ≤ x ≤ 0.25 or 0.1 ≤ x ≤ 0.2. A component according to any one of claims 1 or 3 to 7 or use of a component according to any one of claims 2 to 7, wherein the LSNO component is an LSNO crystal. Component according to one of claims 1 or 3 to 7 or use of a component according to one of claims 2 to 7, wherein the LSNO component is a deposited layer produced by deposition. A component or use of a device according to claim 9, wherein the LSNO layer is deposited on a substrate. Crystalline LSNO substrate with integrated circuits wherein the substrate has the composition La _2-x Sr _x NiO ₄ , and wherein 0 <x ≤ 0.5 and above 10 MHz, the relative permittivity of ε _r ≥ 8,000. The crystalline LSNO substrate according to claim 11, wherein 0 <x ≦ 0.3 and the relative permittivity ε _r ≥ 15,000.

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