JP2002075708A - Abnormal voltage shut off element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormal voltage shut off element, having a low critical voltage which is used to protect a semiconductor element from a transient abnormal voltage. SOLUTION: This abnormal voltage breaking element can act surely as an abnormal voltage breaking element at very low operating voltage of 1.5 V by using amorphous OsO2 metal oxide. Furthermore, a protecting element is assembled in a conducting line itself, and in particular, abnormal voltage protection is enabled with a thin-film multilayer wiring itself. Thereby requirements of both turning into ultra micro dimensions/ultra high density and planarizing in a device manufacturing process can be satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal voltage cutoff device used for protecting a semiconductor device from a transient abnormal voltage.

[0002]

2. Description of the Related Art Semiconductor devices centering on Si have continued to evolve in a wide variety of fields, and have brought downsizing and high performance with various electronic devices such as personal computers. However, a semiconductor element is generally vulnerable to a transient abnormal voltage, and may malfunction or be destroyed by lightning damage (external surge) of a personal computer. Abnormal voltage absorbing elements have been developed in order to remove damage caused by abnormal voltages and the like due to various causes. In such a situation, for example, research on ceramic varistors has been conducted.

[0003] The abnormal voltage absorbing elements, which have been studied above, have a high resistance and hardly any current flows below a certain critical voltage, and when the critical voltage is exceeded, the resistance suddenly becomes low and a current flows. Things. However, the conventional one is a disc-shaped ceramic sintered body having a critical voltage of about 10V.
It is not suitable as an element for protecting a semiconductor element having a low operating voltage such as Si used in a personal computer or the like from lightning damage (lightning surge) due to a high abnormal voltage that senses (actuates). . Furthermore, 1.5V of the semiconductor device drive
Due to the progress of lowering the voltage as described above, the abnormal voltage interrupting element must be a thin film type element that reliably operates at the low operating voltage.

In order to operate at such a low voltage, a low resistivity in a steady state below a certain critical voltage,
Heat generation and current loss are as small as possible, but it is good to have the characteristic that the current is surely cut off at a high voltage higher than the critical voltage. That is, failure and destruction of the personal computer and the like are prevented.

[0005] It is an object of the present invention to provide a novel material which becomes an abnormal voltage cutoff element having characteristics suitable for lowering the operating voltage. In examining the non-linear characteristics of voltage and current for various materials in order to solve the above-mentioned problems, amorphous OsO ₂ has a low resistivity independent of temperature (about 5 × 10 ⁻³ Ωcm) as shown in FIG. FIG. 2 satisfies the requirement that “in a steady state below a certain critical voltage, the resistivity is low and heat generation and current loss are small”, and a high voltage above a certain critical voltage (40 V / c) is satisfied.
In m), they found that the current could be cut off reliably by causing a breakdown,
The problem of providing the novel abnormal voltage cutoff element material has been solved.

[0006]

The present invention SUMMARY OF THE INVENTION are abnormal voltage blocking element, which comprises using a metal oxide OsO ₂ amorphous.

[0007]

Aspects of the Invention A. Amorphous Os with the above characteristics
O ₂ material Amorphous OsO ₂ is obtained by DC glow discharge of OsO ₄ gas. There have been many reports on the synthesis of amorphous OsO ₂ , and the amorphous properties of the synthesized film show no peak in X-ray diffraction and the distribution of Os and O in the thickness method is uniform. It has been reported that this is confirmed by Auger electron beam spectrum observation. It is also reported that the film has a high conductivity (5 × 10 ⁻³ Ωcm) independent of temperature. Furthermore, observation using high-resolution X-ray photoelectron spectroscopy revealed that it was OsO ₂ [Y. Hayakawa, K. Fukuzaki, S. Kohiki, Y. Shibata.
a, T.Matsuo, K, Wagatsma, M.Oku, Thin Solid Films,
347, 56 (1999)].

[0008] Such characteristics will be described in detail.
OsO_FourGlow discharge deposited films have no periodic lattice
(amorphous). Substrate (MgO) in powder X-ray diffraction method
No diffraction other than diffraction from the sample was observed (Fig. 3).
Wide distribution in the oblique incidence X-ray diffraction method
Only intensity peaks are observed (FIG. 4). This
The load peak is the glow discharge deposited film OsO. _TwoThin film
Morphus. More powerful thin film table
Using ion scattering spectroscopy, which is a method for analyzing the surface structure,
As shown in Fig. 5, no periodic structure was observed in the scattered ion intensity.
Not confirmed, this film was confirmed to be amorphous
Was done. Here, the atomic arrangement up to several atomic layers on the film surface
In order to investigate the periodicity of⁺Io
Direct collision ion scattering spectroscopy using Various incidents
Of the shadowing effect on the scattered ion intensity curve at
No effect has been found. These X-ray diffraction and direct collision ion
Scattering spectroscopy results are consistent with the electron transport properties,
sO_FourGlow discharge film is aperiodic (amorphous)
Shows sex.

As shown in FIG. 6, Auger electron spectroscopy
Os and O are uniform in the depth direction composition distribution analysis of the thin film
Distributed in the membrane. CKL of surface contamination layer_{twenty three}L_{twenty three}Strength is
O and Os reduced by argon ion sputtering
Of the Auger peak intensity ratio is almost constant over the entire film.
Is shown. O and Os must be uniformly distributed in the thin film
Was revealed by Auger electron spectroscopy. X-ray light
FIG. 7 shows the chemical state obtained by electron spectroscopy.
Os4d_5/2Electron binding energy and Os4f_7/2electronic
OsO whose binding energy has been reported so far_Twoof
Matches the value, OsO_FourGlow discharge deposited film is amorphous
OsO _TwoIt can be seen that it is. By argon ion
Sputtering changes from lower spectrum to upper
It has become. The attached carbon is removed, but Os4d_5/2Join
The energy remains at 279.0 eV and does not change.
_TwoWas consistent with the reported value of 279.8 eV. Al of 1 keV
Os4d by sputtering with Gon ion_5/2The pea
In this experiment, the gold position was 279.0 eV.
The value of the genus Os was larger than the measured value of 278.1 eV.
These results were obtained by argon ion sputtering.
At 0.5 keV, Os of the thin film sample is not reduced and 1 ke
In V, metal and OsO_TwoIndicates an intermediate state of
You.

The resistance value of the amorphous OsO ₂ film by the four-terminal method is 5 × 10 ⁻³ Ωcm or less, and a metallic band structure is expected. A valence band X-ray photoelectron spectrum (FIG. 8a) was measured to examine this band structure, and a first principle band calculation [8b: DOS (States /
eVCell) is the density of states (the number of electronic states per unit volume and unit energy width). ] Was performed. Amorphous OsO
Valence band spectrum of ₂ similar to the first principles calculations of the single-crystal OsO _2, is now that the world's first measurement and calculation were made. Useful information from this is broadening in the amorphous band spectrum, and the localization of electrons in each crystal field due to random potential and the electric field dependent conductivity nonlinearity due to hopping can be estimated. The valence band X-ray photoelectron spectrum of the amorphous OsO ₂ film showed good agreement in the vicinity of the Fermi surface with the theoretical spectrum of the OsO ₂ crystal obtained from the first principle band calculation.
However, in the theoretical spectrum, O2p in the energy region of -2 eV or less splits into two peaks having maximum values at 4 eV and 8 eV, but the observed spectrum is 3 eV.
From 8 to 8 eV. FIG. 8B shows the linear-muffin-tin-orbital (L) under local density approximation (LDA).
It is a theoretical electronic state density of the OsO ₂ crystal obtained by using the (MTO) method. Electron transport properties are related to the density of states near the Fermi surface, k _B T of about regions. Where k _B is the Boltzmann constant and T is the absolute temperature of the system. In general, the main features of the electronic structure of an amorphous material can be explained by the crystal field up to the first proximity, as in the case of a single crystal. The valence band spectrum of single crystal OsO ₂ has not been reported so far, and a first-principles band structure calculation was performed to obtain information on the density of states near the Fermi surface. From the agreement between the experimental spectrum and the theoretical spectrum near the Fermi energy, it can be inferred that each of them exhibits metallic resistivity and temperature dependence. The resistivity of single crystal OsO ₂ reported to date is 80
3 × 10 ^-6 Ωcm and 6 × 10 ^-5 Ω at K and 300K, respectively
cm and the temperature coefficient of resistivity is positive. The resistivity of amorphous OsO ₂ is _two to three orders of magnitude higher than the reported value of single crystal OsO ₂ , and its temperature dependence shows a behavior completely different from that of metallic single crystal OsO ₂ . The electron transport properties of amorphous OsO ₂ reflect the mobility gap due to a random potential field.

The difference between the observed spectrum and the theoretical spectrum is
As shown in FIG. _TwoFilm resistivity electric field
Strength dependence is due to lack of long-range order (amorphous)
Implications for Fermi level band intrusion at the mobility edge
Is shown. In other words, the Fermi band becomes an excessive electric field
If you cross the upper mobility gap,
Amorphous OsO showing resistivity_TwoSuddenly big
This will cause resistance. Based on the above electronic characteristics,
Rufus OsO_TwoReveals electronic structure and conduction mechanism
Of an abnormal voltage cut-off device with low resistivity
It is a promising material.

EXAMPLE Formation of OsO ₂ deposited film by glow discharge of OsO ₄ . OsO ₄ vapor is introduced into the glow discharge deposition chamber (1 × 10 ⁻³ Torr) while maintaining the pressure at 5 × 10 ⁻² Torr. 1000 nm film thickness under the conditions of an applied electric field of 1.2 kV and a current of 2 mA
Deposited. The film was taken as a thin film type abnormal voltage cutoff device, which was connected to a surge voltage source, and the voltage-current characteristics were examined. When the distance between terminals was 2.5 cm, an excessive voltage of 100 V or more was cut off. As a result, since the OsO ₂ deposited film of the present invention has a small resistivity of about 5 × 10 ⁻³ Ωcm, there is little loss such as heat generation, and it is useful as an abnormal voltage cutoff element under an operating voltage of 1.5 V.

[0013]

As described above, the element made of amorphous OsO _{2 of the} present invention has an excellent characteristic that it can reliably function as an abnormal voltage cutoff element even at an extremely low operating voltage of 1.5 V. It is useful as an abnormal voltage cutoff element that protects an electronic device from abnormal voltage due to an unexpected cause. Further, the amorphous OsO ₂ abnormal voltage cutoff device is manufactured by a dry process compatible with a semiconductor device manufacturing process. Since the device itself is a glow discharge thin film, it becomes a micro conductive path in a multilayer semiconductor device in combination with lithography such as EB exposure, and the conductive path itself functions as a device. Unlike the conventional protection element, which has to add a pellet formed by compressing bulk ceramics as an external circuit, which tends to cause problems in reproducibility of characteristics and its structural strength, the protection element is built into the conductive line itself In particular, since the abnormal voltage protection can be performed by the thin-film multilayer wiring itself, it can satisfy the requirements of both miniaturization, ultra-high density and flattening in the device manufacturing process, and excellent reproducibility of characteristics. It is expected that there is something. From this, the thin film conductive line type amorphous OsO ₂ abnormal voltage cutoff device of the present invention is useful as an abnormal voltage cutoff device of a semiconductor device.

[Brief description of the drawings]

FIG. 1. Temperature dependence of resistivity of amorphous OsO ₂ film

FIG. 2 Dependence of resistivity of amorphous OsO ₂ film on voltage

FIG. 3 is an X-ray diffraction pattern of an OsO ₄ gas DC glow discharge deposited film (substrate, MgO)

FIG. 4 Oblique incidence X-ray diffraction pattern of OsO ₄ gas DC glow discharge deposited film

FIG. 5 is a direct collision ion scattering spectroscopy of an OsO ₄ gas DC glow discharge deposited film.

FIG. 6: Element distribution of this thin film measured using Auger electron spectroscopy.

FIG. 7 shows the change in the chemical state in the depth direction, which was examined by X-ray photoelectron spectroscopy in combination with 0.5 eV argon ion sputtering.

FIG. 8 is a valence band X-ray photoelectron spectrum of an amorphous OsO ₂ film.

FIG. 9 is a schematic diagram of movement of a Fermi band by an electric field and penetration into a mobility edge.

Claims (1)

[Claims] 1. An abnormal voltage cut-off device using an amorphous metal oxide OsO ₂ .