• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
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    • 专利摘要:
    PURPOSE: A scanning SQUID(super conducting quantum interference device) microscope is provided to achieve improved performance of a SQUID sensor by maintaining the temperature of the SQUID sensor low, and improved resolution by minimizing the distance between the SQUID sensor and a specimen. CONSTITUTION: A scanning SQUID microscope comprises a SQUID sensor(41) for measuring magnetic fields of a specimen(50); a vacuum container(43) for maintaining the SQUID sensor at a low temperature; a cooling unit for cooling the SQUID sensor in the vacuum container; a cold finger(44) and a thermal link(45) for connecting the cooling unit and the SQUID sensor; and a thermal barrier(47) connected to the cold finger or the thermal link, and which cuts off the peripheral area of the SQUID sensor from the inner wall of the vacuum container.
    公开号:KR20040072419A
    申请号:KR1020030008893
    申请日:2003-02-12
    公开日:2004-08-18
    发明作者:이호년
    申请人:엘지전자 주식회사；
    IPC主号:
    专利说明:

    Scanning SQUID Microscope
    [10] The present invention relates to a magnetic sensor, and more particularly, to a quantum interference element scanning microscope suitable for preventing signal distortion due to heat introduced from the outside.
    [11] Non-destructive evaluation (NDE) is mainly made by X-ray, ultrasound, heat detection, etc. Applications are determined by precision, spatial resolution, and ease of use.
    [12] In the case of using X-ray, very detailed formation can be obtained, so it is used for the inspection of fine structure, but it requires attention in use and it is basically a transmission method, so there is a disadvantage that a shaded area is generated for the laminated structure.
    [13] Ultrasonic methods are not suitable for precise structures because of their spatial resolution on the order of mm, but they are widely used in relatively macroscopic devices, components, or mechanical structures because of their ease of use.
    [14] The heat sensing method is used only when there is a difference in temperature, but it is suitable for a case where a relatively fast inspection is required because the shape is acquired at once.
    [15] Compared to these methods, non-destructive testing through magnetic field detection is not currently actively applied, but much research is being conducted because of its necessity. The use of magnetic fields is more advantageous than ultrasonic methods for the detection of defects away from the surface due to the high permeability of the magnetic field and allows the analysis of stacked structures.
    [16] In particular, the self-destructive inspection conducted at the detection distance of several mm level, since the shape information is basically obtained by the scanning method, spatial resolution is important, which is determined by the sensitivity and the area of the sensor and the distance between the sample and the sensor.
    [17] In order to be competitive with X-ray and ultrasonic non-destructive testing, magnetic non-destructive testing must accommodate all of these advantages, which requires both good magnetic sensitivity and spatial resolution.
    [18] One of the magnetic sensors that has been developed so far is the SQUID (Super Conducting Quantum Interference Device).
    [19] SQUID is the most sensitive sensor ever developed and can be manufactured in a size of 10 µm, enabling spatial resolution of at least 10 µm. In fact, since SQUID is not a sensor with on / off output but has a continuous output and a high S / N ratio, resolution can be improved through inverse problem analysis.
    [20] In non-destructive testing, the higher the sensitivity of the sensor, the greater the amount of information obtained and thus more accurate testing. In addition, since the amount of information proportional to the spatial resolution can be obtained, the non-destructive test using SQUID enables the test that cannot be obtained by the conventional method.
    [21] New non-destructive inspections that can be implemented using these advantages include planar information, such as breaks or short circuits in interlayer copper wires, and depth information, such as interlayer shorts or open vias, on multi-layer precision circuit boards. Short circuits in packaged semiconductor circuits can also be identified (G. Gerber et al., Appl. Phys. Lett., 68, 1555 (1996), P. Carelli et. Al., IEEE Trans. Appl. Supercon., 11, 210 (2001), JR Kirtley et al., Annu. Rev. Mater. Sci., 29, 117 (1999)).
    [22] The high temperature superconducting SQUID system is largely divided into a SQUID sensor unit for detecting a magnetic field of a sample and a signal processing unit for processing a signal from the SQUID sensor unit.
    [23] FIG. 1 is a view illustrating a structure of the SQUID sensor unit. The SQUID sensor 11 measures a fine magnetic field of a sample, and has a window 12 through which the magnetic field of the sample is transmitted to the SQUID sensor 11. 11, a cooling device 14 composed of a liquid nitrogen supply device or a freezer for cooling the SQUID sensor 11 in the vacuum container 13 for keeping the temperature at a low temperature, and the cooling device 14 A cold finger 15 and a thermal link 16 provided between the SQUID sensor 11 and the SQUID sensor 11 to cool the SQUID sensor 11 by heat conduction, and the SQUID sensor unit from the signal processor. Supply and Return Lines (17), the Supply and Return Lines (17) and the for receiving a signal required for driving and for transmitting a signal measured by the SQUID sensor unit to the signal processing unit Between the vacuum vessels (13) It consists of a flange (Flange) (18).
    [24] At this time, since the cold finger 15 should be excellent in thermal conductivity, copper (Cu) is used in most cases. However, since the SQUID sensor 11 has a very good sensitivity to the magnetic field, the SQUID sensor 11 may distort the signal from the sample due to the eddy current formed in the copper (Cu) having excellent electrical conductivity due to the change in the surrounding magnetic field.
    [25] Therefore, the thermal link 16 close to the SQUID sensor 11 is not easy to use copper (Cu), it is preferable to use a material having excellent thermal conductivity and poor electrical conductivity.
    [26] As such a material, a representative material is sapphire (Sapphire, Al2O3). As shown in FIG. 2, at 77K, which is the liquid nitrogen temperature used for the cooling device 14, the thermal conductivity is superior to that of Cu.
    [27] 3 is an enlarged view of a SQUID sensor unit according to the prior art.
    [28] There is a method of arranging the SQUID sensor 11 in a direction perpendicular to the manner in which the SQUID sensor 11 is arranged in parallel with the sample 20. In the case of FIG. 3, the SQUID sensor 11 is arranged in parallel with the sample 20.
    [29] In order to maximize the resolution of the SQUID sensor 11, it is necessary to close the distance between the sample 20 and the SQUID sensor 11. When the distance between the sample 20 and the SQUID sensor 11 becomes small, the SQUID sensor 11 There is a risk that the wire bonding, which is connected to the SQUID sensor 11, is in contact with the window 12 in order to transfer the signal measured by) to the signal processor.
    [30] Since a large area of the SQUID sensor 11 receives radiation heat from the window 12 close to room temperature, the temperature of the SQUID sensor 11 increases, thereby deteriorating the characteristics of the SQUID.
    [31] When the SQUID sensor 11 is perpendicular to the sample 20, the distance to the sample 20 may be minimized as compared with the parallel case in order to increase the resolution. However, even at this time, in order to further improve the characteristics of the SQUID sensor 11, it is important to keep the temperature of the SQUID sensor 11 lower.
    [32] Therefore, the conventional quantum interference device scanning microscope as described above has the following problems.
    [33] First, in order to maximize the resolution of the SQUID sensor, reducing the distance between the sample and the SQUID sensor causes the wire bonding to come into contact with the window and break.
    [34] Second, as the area of the SQUID sensor receives radiation heat from a window near room temperature, the temperature of the SQUID sensor is increased, thereby deteriorating the characteristics of the SQUID.
    [35] Third, since the distance between the SQUID sensor and the sample is difficult to reduce for the above reason, the resolution decreases.
    [36] An object of the present invention is to provide a quantum interference device scanning microscope that can maximize the performance of the SQUID sensor by maintaining a low temperature of the SQUID sensor to solve the above problems.
    [37] In addition, the object of the present invention is to provide a quantum interference device scanning microscope that can improve the resolution by minimizing the distance between the SQUID sensor and the sample.
    [1] 1 is a view showing a general SQUID sensor unit,
    [2] 2 is a graph showing a change in thermal conductivity of copper (Cu) and sapphire (Sapphire) with temperature,
    [3] 3 is an enlarged view of a SQUID sensor unit according to the prior art,
    [4] 4 is an enlarged view of a SQUID sensor unit according to the present invention.
    [5] ** Description of the symbols for the main parts of the drawings **
    [6] 41: SQUID sensor 42: window
    [7] 43: vacuum vessel 44: cold finger
    [8] 45: thermal link 46: wire
    [9] 47: thermal barrier
    [38] The quantum interference device scanning microscope according to the present invention for achieving the above object is a SQUID (Super Conducting Quantum Interference Device) sensor for measuring the magnetic field of the sample, a vacuum vessel for maintaining the SQUID sensor at a low temperature, within the vacuum vessel A quantum interference device scanning microscope including a low temperature cooling device for cooling a SQUID sensor, a cold finger and a thermal link connecting the cooling device and the SQUID sensor, wherein the SQUID is connected to either the cold finger or the thermal link. And a thermal barrier for blocking the sensor around the inner wall of the vacuum container.
    [39] More specifically, the thermal barrier is characterized in that it is connected to the cold finger or the thermal link using at least one of epoxy, silver paste, mechanical contact.
    [40] More specifically, the thermal barrier is characterized in that it is configured using Sapphire (Sapphire), MgO, LAO, STO and Si.
    [41] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
    [42] 4 is a view showing a SQUID sensor unit according to the present invention, the SQUID sensor 41 for measuring the fine magnetic field of the sample 50, the window 42 for transmitting the magnetic field of the sample 50 to the SQUID sensor 41 And a vacuum device 43 for keeping the SQUID sensor 41 at a low temperature, and a cooling device (illustrated as a liquid nitrogen supply device or a freezer for cooling the SQUID sensor 41 in the vacuum container 43). Cold finger 44 for transferring the low temperature of the cooling device to the SQUID sensor 41 by heat conduction, the upper surface of the side adjacent to the window 42 is connected to the SQUID sensor 41, The opposite side is connected to the cold finger 44, the thermal link (45) for cooling the SQUID sensor 41, the magnetic field measured by the SQUID sensor 41 (not shown) Wire 46 and the cold finger 44 or It consists of a thermal barrier (47) connected to any one of the thermal links (45) and blocking the inner wall of the vacuum vessel (43) around the SQUID sensor (41).
    [43] The thermal barrier 47 is not transmitted to the SQUID sensor 41 by the heat of the radiation heat (irradiation heat) coming from the outside of the vacuum vessel 43 near the room temperature and the movement of the gas molecules remaining inside the vacuum vessel 43. It plays a role of preventing.
    [44] The thermal barrier 47 must be in good contact with the cold finger 44 or the thermal link 45 through epoxy, silver paste or mechanical contact to maintain the same temperature as the cold finger 44. do.
    [45] As the material of the thermal barrier 47, a material having excellent thermal conductivity and poor electrical conductivity is formed by using sapphire, MgO, LAO, STO, and Si.
    [46] In addition, if the above-mentioned material can be used to cover the SQUID sensor 41 from the inner wall of the vacuum vessel 43 and can be brought into contact with the cold finger 44 or the thermal link 45, the cylindrical shape as well as the shape shown in FIG. It can also be processed into other shapes.
    [47] In general, the method of lowering the temperature of the SQUID sensor used in the SSM is a method of thermal conduction as described above.
    [48] Therefore, copper (Cu) having excellent thermal conductivity is used as the cold finger 44 and sapphire or silicon (Si) is used for the thermal link 45 to remove distortion of the signal due to eddy currents and improve thermal conductivity.
    [49] Heat conduction to the SQUID sensor 41 is made through the following path.
    [50] Cooling Unit => Cold Finger => Thermal Link => SQUID Sensor
    [51] However, the SQUID sensor cooled through heat conduction is heated to some extent due to the heat coming from the vacuum vessel 43 near room temperature (300K) or the movement of gas molecules inside the vacuum vessel 43, which is a characteristic of the SQUID sensor. It can be reduced, and eventually, the distance from the sample 50 is bound to be reduced, resulting in a decrease in resolution, which is an advantage of the SSM.
    [52] Among the heat transmitted from the outside, the radiation heat can be described by Stefan-Bolzmann's law.
    [53] The Stefan-Bolzmann law is expressed by Equation 1 below, in which the wavelength of light generated from an ideal black body capable of absorbing all light depends only on temperature, regardless of the type of black body.
    [54] Q irr = εσ SB (T 1 4 -T 2 4 )
    [55] Where ε is the effective degree of blackness, σ SB is the Stefan-Boltzmann constant (= 5.67 x 10-8 W / m 2 K 4), and T 1 and T 2 are the temperatures of two material temperatures, respectively.]
    [56] Therefore, a simple calculation can be made using the equation shown above.
    [57] For example, assuming that the temperature of each part is as shown in Table 1 when there is or without the thermal barrier 47, and compares the heat exiting in the perpendicular direction of the SQUID sensor 41 as follows. (The heat exiting to sample 50 is insignificant and not considered here.)
    [58] Cold finger temperatureThermal link temperatureSQUID sensor temperatureThermal Barrier TemperatureVacuum container inner wall temperature If there is no thermal barrier77 K78 K82 K-300 K If you have a thermal barrier77 K78 K79 K80 K300 K
    [59] therefore, = Therefore, it can be called almost zero.
    [60] Therefore, it can be confirmed through calculation that the thermal barrier 47 of the present invention can effectively prevent the radiation heat from reaching the SQUID sensor 41.
    [61] In addition, when the vacuum is not good, heat may be transferred from the inner wall of the vacuum container 43 to the SQUID sensor 41 due to the movement of the gas molecules remaining inside the vacuum container 43.
    [62] However, in the present invention, not only the thermal barrier 47 around the SQUID sensor 41 interferes with the movement of the gas molecules, but also the gas molecules by reducing the temperature of the gas molecules through the collision with the gas molecules and eventually reducing the movement speed. It is possible to reduce heat due to convection of molecules.
    [63] As a result of applying the invention proposed in the present invention to the actual product, the temperature of the cold finger, the thermal link, the SQUID sensor and the thermal barrier can be similarly observed in Table 1 above, and the operating temperature of the SQUID sensor is compared with the case without the thermal barrier. Successfully lowered more than 2K.
    [64] This is because the thermal barrier is an effective barrier of radiation heat from the inner wall of the vacuum vessel and effectively prevents the movement of gas molecules remaining inside the chamber.
    [65] The reduction of 2K at low temperatures is an important factor in improving the properties of the SQUID sensor, which provides better resolution by bringing the SQUID sensor closer to the sample.
    [66] As described above, the quantum interference device scanning microscope of the present invention can keep the temperature of the SQUID sensor low without distorting the signal coming into the SQUID sensor by using the thermal barrier, thereby minimizing the distance between the sample and the sensor, thereby improving the SSM resolution. And the effect of improving the characteristics of the SQUID sensor.
    [67] Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.
    [68] Therefore, the technical scope of the present invention should not be limited to the contents described in the examples, but should be defined by the claims.
    权利要求:
    Claims (3)
    [1" claim-type="Currently amended] SQUID (Super Conducting Quantum Interference Device) sensor for measuring the magnetic field of the sample, a vacuum vessel for keeping the SQUID sensor at low temperature, a low-temperature cooling device for cooling the SQUID sensor in the vacuum vessel, the cooling device and the SQUID sensor In the quantum interference device scanning microscope including a cold finger and a thermal link connecting,
    And a thermal barrier connected to either the cold finger or the thermal link and blocking the periphery of the SQUID sensor from the inner wall of the vacuum vessel.
    [2" claim-type="Currently amended] The method of claim 1,
    The thermal barrier
    A quantum interference device scanning microscope characterized in that connected to the cold finger or the thermal link using at least one of epoxy, silver paste (Ag paste), mechanical contact.
    [3" claim-type="Currently amended] The method of claim 1,
    The thermal barrier
    A quantum interference device scanning microscope characterized in that the use of sapphire (Sapphire), MgO, LAO, STO and Si.
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    同族专利:
    公开号 | 公开日
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2003-02-12|Application filed by 엘지전자 주식회사
    2003-02-12|Priority to KR1020030008893A
    2004-08-18|Publication of KR20040072419A
    优先权:
    申请号 | 申请日 | 专利标题
    KR1020030008893A|KR20040072419A|2003-02-12|2003-02-12|Scanning squid microscope|
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