JP2006279912A - Near electric field electromagnetic wave noise suppressing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a near electric field electromagnetic wave noise suppressing thin film material for efficiently suppressing near electric field electromagnetic wave noise that occurs at an electronic device or an electronic circuit operating in a sub-microwave band. <P>SOLUTION: In the near electric field electromagnetic wave noise suppressing thin film material, surface resistance Rs (ρ/t) of the thin film material is controlled to between 10 Ω/square and 1,000 Ω/square that matches the spatial characteristic impedance Z (377 Ω), in order to secure the reflection coefficient (S<SB>11</SB>) of the noise occurring at the electronic device or electronic circuit operating in a sub-microwave band to be -10 dB or lower, as a practical level, and to simultaneously secure that the electromagnetic noise suppression effect (ΔP<SB>loss</SB>/P<SB>in</SB>) is 0.5 or higher. Furthermore, the near electric field electromagnetic wave noise suppressing thin-film material comprises a soft magnetic thin-film material that satisfies the above conditions, has a magnetic resonance frequency in the desired frequency band, and represents large resistance loss, as well as the magnetic loss. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive thin film that suppresses near-field electromagnetic noise in a high-frequency band of 1 GHz or more and 20 GHz or less, and particularly relates to a method for suppressing near-field electromagnetic noise that causes a problem in a semiconductor element or high-frequency electronic component that operates at high speed.

  In recent years, electronic devices in the advanced information society have been accelerating in frequency. A typical one is a personal computer, and the operation frequency of the central processing unit exceeds 1 GHz. In addition, in communication devices, mobile phones (0.9, 1.5, 1.9 GHz), satellite broadcasting (11.7 to 19.0 GHz), wireless LAN (2.45, 5.0, 19.0 GHz), etc. Has been implemented or is under consideration. In addition, non-stop automatic toll collection system (ETC) (5.8 GHz), rear-end collision prevention radar (7.6 GHz), etc. in highway traffic system (ITS) are used, and will continue to be used in the GHz band in the future. The use of high-speed semiconductor integrated devices is expected to increase.

  In parallel with the trend toward higher frequencies, electronic devices are becoming lighter, thinner, and smaller. The size of electronic components used, the degree of integration of semiconductor elements, and the density of electronic component mounting boards are significantly increasing. . Accordingly, the electronic parts and signal wirings that are densely integrated and mounted are close to each other, and are combined with the above-described high frequency operation, so that unnecessary radiation of electromagnetic waves is likely to occur. This leads to malfunction of the equipment, and is a serious technical factor that hinders downsizing and high performance of the equipment. Recently, EMI (electromagnetic wave interference) such as unwanted radiation has been actively pointed out with respect to this problem, and EMC (electromagnetic compatibility) has been emphasized as a comprehensive countermeasure, and research in this field has begun to flourish. . Measures have been taken for electronic devices with a drive frequency of low frequency to several MHz by covering the housing with a soft magnetic material, and for electronic devices with a drive frequency of about 1 to 2 GHz, a sheet-like composite magnetic material is used. Measures are applied directly to electronic components and electromagnetic noise sources.

Invention disclosure

Problems to be solved by the invention

  In the future, if the drive frequency is increased and the device is further reduced in thickness, the wavelength of the electromagnetic wave will be almost the same as that of the printed wiring. Technology (micro EMC) that can prevent electromagnetic noise is required.

  Currently, the electromagnetic noise suppression technology using a magnetic thin film is proposed as a micro-EMC technology, which is a method of simultaneously integrating thin films having electromagnetic noise suppression performance during printed circuit board fabrication. When thin films are used to suppress near-field electromagnetic noise, reflection due to the impedance of the thin film becomes a problem, and if this reflection is large, part of the electromagnetic noise returns to the signal source, causing secondary disturbance in the signal source. To do. This reflection has a practically required level of −10 dB or less.

  As for the application of thin films to near-field electromagnetic noise countermeasures, nano-granular soft magnetic thin films using a large magnetic loss (μ ”) have been studied. However, since nano-granular has a small electrical resistivity of about several hundred μΩcm, Due to the problem of impedance mismatching, there is a problem that reflection becomes large and a large μ ″ effect on the radio wave absorption characteristics cannot be obtained sufficiently. Therefore, in this material, a measure for controlling the impedance of the entire thin film by patterning the thin film into a strip shape is taken for the reflection reduction.

Means for solving the problem

In view of the above circumstances, the inventors pay attention to the surface resistance Rs (Ω / □) determined from the specific resistance (ρ) and the film thickness (t) of the thin film as a parameter for determining the impedance of the thin film. As a result of making sincere efforts to investigate the relationship between the surface resistance (Rs), reflection (S11), and near-field electromagnetic noise suppression effect (P _loss / P _in ), surface resistance Rs (Ω / □) of the conductive thin film It has been found that the reflection can be reduced to a practical level of −10 dB or less by controlling the impedance to 50Ω / □ or more, which matches with the characteristic impedance (˜377Ω) of the space. Furthermore, when the surface resistance (Rs) is controlled to a value approximately equal to the characteristic impedance Z (˜377Ω) of the space, the two are perfectly matched, and the unwanted radiation is absorbed into the thin film with high efficiency. It has been found that a very large near-field electromagnetic wave noise suppression effect can be obtained with high efficiency due to the resistance loss and magnetic loss. Up to now, there has been no report examined from the viewpoint of matching the surface resistance Rs with the spatial impedance Z in the countermeasure against near-field electromagnetic noise by a thin film.

  The present invention is a method of suppressing reflection and electromagnetic noise by controlling the surface resistance (Rs) of a conductive thin film, and has been studied for the purpose of applying the thin film to the suppression of near-field electromagnetic noise.

The features of the present invention are as follows. In the first invention, the electromagnetic wave noise generated in the quasi-microwave band has a reflection coefficient (S ₁₁ ) of −10 dB or less, which is a practical level, and a noise suppression effect (ΔP _loss / P _in ) of 0.1. In order to suppress to 5 or more, the surface resistance Rs (ρ / t) of the thin film material is controlled to be 10Ω / □ or more and 1000Ω / □ or less, which matches the characteristic impedance Z (377Ω) of the space. The present invention relates to a near-field electromagnetic noise suppression thin film material.

The second invention suppresses the reflection coefficient (S ₁₁ ) to −10 dB or less and the noise suppression effect (ΔP _loss / P _in ) to 0.7 or more with respect to electromagnetic wave noise generated in the quasi-microwave band. Therefore, the present invention relates to a near-field electromagnetic wave noise suppressing thin film material having a surface resistance Rs (ρ / t) equivalent to a space characteristic impedance Z (377Ω).

  The third invention relates to the first and second inventions, wherein the use frequency band is 1 GHz or more and 20 GHz or less.

  The fourth invention relates to the first and third inventions characterized in that near-field electromagnetic noise is lost using resistance loss.

  A fifth invention relates to the first to fourth inventions, characterized in that an electromagnetic wave noise suppression thin film is disposed on or in the vicinity of an electronic circuit.

  The sixth invention uses an electromagnetic wave noise suppressing conductive magnetic thin film having a natural resonance frequency of permeability of 0.5 GHz or more and 10 GHz or less, and obtains an electromagnetic wave noise suppressing effect using both resistance loss and magnetic loss. The present invention relates to the first to fifth inventions characterized.

  A seventh invention relates to the first to sixth inventions characterized by using an electromagnetic wave noise suppressing conductive thin film having a nano granular structure or a nano hetero structure.

  An eighth invention relates to the first to seventh inventions, characterized in that the electromagnetic noise suppressing conductive thin film for countermeasures against the noise generating portion has a dimension width of at least twice the signal wiring width.

The invention's effect

  In order to suppress electromagnetic noise generated from a microcircuit such as a semiconductor that operates at high speed, countermeasures using a thin film are urgently needed. In the present invention, the surface resistance (Rs) of a conductive thin film is controlled by the present invention. It was explained that reflection (S11) was suppressed to a practical level and that a large electromagnetic noise suppression effect was obtained by matching with the impedance Z (377Ω) of the space. These results are basic technologies for application of thin film materials to near field electromagnetic noise suppression measures, and enable application of thin film electromagnetic noise suppression bodies.

Embodiments of the present invention will be described below. First, the thin film used in the present invention is an Al—O conductive thin film formed on a glass substrate by sputtering. An Al—O conductive thin film having an arbitrary specific resistance (ρ) with different oxygen content was prepared by reactive sputtering in an Ar + O ₂ mixed gas atmosphere using RF magnetron sputtering under the following conditions. .

Sputtering gas pressure: 5 × 10 ⁻³ Torr
Input power: 150W
Substrate: Corning # 7059
Oxygen flow ratio: 1.0-1.6%
Film thickness: ~ 1μm

  The specific resistance (ρ) of the obtained sample was measured by the direct current four-terminal method, and the surface resistance Rs (Ω / □) was determined from the value and film thickness by Rs = ρ / t.

  The electromagnetic noise suppression effect of the obtained sample was investigated using the electromagnetic noise evaluation system shown in FIG. Referring to FIG. 1, the evaluation system for electromagnetic wave noise suppression effect is a network analyzer through coaxial cables 2a and 2b on both ends of a microstrip line (MSL) 1a formed on a dielectric substrate 1 whose back surface is a ground conductor. The sample 3 is cut out so as to have a size of 15 × 35 mm, and is arranged on the MSL so that the film surface is in contact therewith. The line width of the MSL used for evaluation here is 3.5 mm, and the line length is 40 mm.

FIG. 2 shows the evaluation results of the electromagnetic wave noise suppression characteristics of Al—O conductive thin films having different surface resistances Rs. A dotted line represents the characteristics of MSL alone, and the magnitude of the surface resistance Rs is distinguished by a plot shape. It can be seen from FIG. 2 that the surface resistance showing a reflection (S11) of −10 dB or less at a practical level is 50Ω / □ or more. In addition, even when Rs is 50 Ω / □ or more at 1 GHz or less, S11 does not become −10 dB or less from the problem due to the wavelength of the frequency, and from this result, it can be seen that the corresponding frequency is 1 GHz or more. Further, when Rs is 50 and 200Ω / □, transmission (S21) is greatly attenuated, and from these values, 1- [| S11 | ² + | S21 | ² ] suppresses electromagnetic wave noise (ΔP _loss / P _in ). Is obtained, a very large electromagnetic noise suppression effect exceeding 0.6 is obtained. From the above results, it can be seen that a conductive thin film having a surface resistance controlled to 50 Ω / □ or more is effective for suppressing reflection (S11) at 1 GHz or more to −10 dB or less.

FIG. 3 summarizes the surface resistance (Rs) dependence of the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) at each frequency. According to FIG. 3, the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) increases as Rs approaches 10 ² Ω / □ near each frequency. Although 1 GHz is a broad change, both 2 GHz and 6 GHz appear remarkably. This represents a matching state between Rs of 10 ² Ω / □ and space impedance Z (377 Ω), that is, when Rs is closest to the space impedance Z (377 Ω), both are perfectly matched and low. The electromagnetic wave noise introduced into the conductive thin film by reflection (S11) represents a state of being lost with high efficiency due to the resistance loss of the conductive thin film.

FIG. 4 shows the results of the surface resistance (Rs) dependence of the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) at 6 GHz for various conductive thin films having different constituent elements, film thicknesses, and specific resistances. In any case, when arranged by Rs (ρ / t) determined from the specific resistance (ρ) and the film thickness (t), it almost coincides with a curve having a peak at Rs = −10 ² Ω / □.

From the above results, since the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) is dependent on Rs, _in order to obtain a larger electromagnetic wave noise suppression effect (ΔP _loss / P _in ), Rs is the impedance of the space. It is important to control to perfectly match Z (377Ω).

FIG. 5 shows the Rs dependence of the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) at each frequency of an Al—O nonmagnetic film having a similar Rs and a CoAlO magnetic film having a natural resonance frequency of permeability at ˜2 GHz. It is the summary result. When 1 GHz and 2 GHz of the CoAlO magnetic film are compared with the Al—O nonmagnetic film, the peak position is shifted to the low Rs side, and the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) increases. In addition, at 6 GHz, both results are almost the same. From the above, it can be seen that in the vicinity of the natural resonance frequency, the magnetic loss in addition to the resistance loss greatly contributes to the electromagnetic wave noise suppression effect (ΔP _loss / P _in ).

FIG. 6 shows 1.0 mm and 3.5 mm wide micro thin films of Al—O conductive thin film exhibiting a high electromagnetic noise suppression effect (ΔP _loss / P _in ) in which space impedance Z (377Ω) and Rs are matched. It is the result of investigating the relationship between the sample line width and the signal line width using the strip line. From this result, even when the signal line width is different from 1 mm and 3.5 mm, a high electromagnetic wave noise suppression effect (ΔP _loss / P _in ) can be maintained if a sample width of ˜2 times the signal line width is provided. I understand.

For comparison, a composite magnetic material sheet (commercially available electromagnetic wave noise suppressor) in which ferromagnetic fine powder is dispersed in a polymer at a high density in FIG. 7 was evaluated in the same manner as in the example. Comparing the representative Al—O conductive thin film (Rs = 200Ω / □, ρ = 2.5 × 10 ⁴ μΩcm, t = 1.25 μm) and the composite magnetic sheet (t = 50 μm) examined this time When the reflection (S11) value is viewed at ˜1 GHz or more, the practical level of −10 dB is cleared in both cases, which is the same result, but a large difference is seen in the transmission (S21). Compared with the electromagnetic wave noise suppression effect (ΔP _loss / P _in ) obtained from these, the Al—O conductive thin film is 2 to 3 times larger. Moreover, since the thickness of both is about 1 μm for the Al—O conductive thin film and about 50 μm for the composite magnetic material sheet, the thickness of the Al—O conductive thin film is about 1 / 50th the thickness of the composite magnetic material sheet. 2 to 3 times the performance.

  In order to suppress electromagnetic noise generated from a microcircuit such as a semiconductor that operates at high speed, countermeasures using a thin film are urgently needed. In the present invention, the surface resistance (Rs) of a conductive thin film is controlled by the present invention. It has been explained that reflection (S11) is suppressed to a practical level, and that a large electromagnetic noise suppression effect is obtained by matching with the impedance Z (377Ω) of the space. These results are basic technologies when thin film materials are applied as a countermeasure for suppressing near-field electromagnetic noise, which is expected to enable the realization of a thin film electromagnetic noise suppressor, and the industrial applicability is extremely high. large.

  This is an evaluation system for electromagnetic wave noise suppression effect.   It is an evaluation result of the electromagnetic wave noise suppression characteristic of the Al-O electroconductive thin film from which surface resistance Rs differs. A surface resistance (Rs) dependence of electromagnetic noise suppression effect (ΔP _loss / _{P in)} at each frequency in the Al-O conductive thin film. It is the result which put together the surface resistance (Rs) dependence of the electromagnetic wave noise suppression effect ((DELTA) _Ploss / Pin) _in 6 GHz about various electroconductive thin films. As a result of summarizing the Rs dependence of the electromagnetic noise suppression effect (ΔP _loss / P _in ) at each frequency of the Al—O nonmagnetic film having the same Rs and the CoAlO magnetic film having a natural resonance frequency of permeability of about 2 GHz. is there.   It is the result of investigating the relationship between the sample width and the signal line width.   It is the result of having performed comparison with this electroconductive thin film and a composite magnetic material sheet.

Claims (8)

To reduce the reflection coefficient (S ₁₁ ) to −10 dB or less, which is a practical level, and the noise suppression effect (ΔP _loss / P _in ) to 0.5 or more with respect to electromagnetic wave noise generated in the quasi-microwave band. Further, the near-field electromagnetic wave noise suppression thin film characterized in that the surface resistance Rs (ρ / t) of the thin film material is controlled to 10 Ω / □ or more and 1000 Ω / □ or less to match the spatial characteristic impedance Z (377 Ω). material. In order to reduce the reflection coefficient (S ₁₁ ) to −10 dB or less and the noise suppression effect (ΔP _loss / P _in ) to 0.7 or more with respect to electromagnetic wave noise generated in the quasi-microwave band, A near-field electromagnetic noise suppression thin film material having a surface resistance Rs (ρ / t) equivalent to a characteristic impedance Z (377Ω). The use frequency band is 1 GHz or more and 20 GHz or less, The near-field electromagnetic wave noise suppression thin film material according to claim 1 or 2 characterized by things. Resistance film is used, The near field electromagnetic wave noise suppression thin film material of any one of Claims 1-3 characterized by the above-mentioned. A near-field electromagnetic noise suppression material, comprising: the electromagnetic wave noise suppression thin film material according to any one of claims 1 to 4 in close contact with or in the vicinity of an electronic circuit. An electromagnetic wave noise-suppressing conductive magnetic thin film having a natural resonance frequency of 0.5 GHz or more and 10 GHz or less in the thin film material according to any one of claims 1 to 5, wherein both resistance loss and magnetic loss are obtained. A near-field electromagnetic wave noise suppression thin film material characterized by obtaining an electromagnetic wave noise suppression effect using 7. A near-field electromagnetic wave noise suppression material according to claim 1, wherein the film structure is a nano granular structure or a nano hetero structure. A near-field electromagnetic noise suppression material, wherein the dimensional width of the electromagnetic noise suppression thin film material according to any one of claims 1 to 7 is at least twice the width of a signal wiring or an electronic device.

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