JPH1123723A - Particle beam detector - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the noise level by using an STJ element,
Provided is a particle beam detection device with improved performance reproducibility. SOLUTION: A chip 2 in which an STJ element array used as a particle beam detector is integrated on a substrate 10 having an opening 11 and wiring layers 12a to 12d made of a superconductive material.
0 and a chip 30 on which a signal processing circuit composed of a SQUID, a superconducting ADC, or the like is integrated, by flip-chip bonding to form a hybrid. The chip 20 is mounted such that the STJ element array faces the opening 11,
The chip 30 has a box-shaped shield body 60 made of a superconductive material.
Put on. A magnetic field is applied only to the chip 20 to detect a particle beam that has entered the STJ element through the opening 11 of the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to photons (electromagnetic waves),
The present invention relates to a particle beam detection device used for detecting a particle beam such as a charged particle and a neutral particle.

[0002]

2. Description of the Related Art As a particle beam detector having high energy resolution and excellent time resolution, a superconducting tunnel junction (hereinafter referred to as S)
A combination of a detection element using a TJ element) and a low-noise signal amplification element using a superconducting quantum interference device (SQUID) is known.

[0005] As shown schematically in FIG.
The element 100 has a structure in which a thin insulating layer 103 is sandwiched between two superconductors 101 and 102. Superconductor 10 on both sides
The 1,102 electrons form a Cooper pair near the Fermi surface and cause Bose condensation. Superconductor 10 on both sides
When causing a difference in potential of each bias voltage V _B to 1,102, the insulation only quasiparticles thermally excited thickness 10~20Å is in the following 2Δ where the difference corresponds to the dissociation energy of the Cooper pairs Quantum mechanically passes through the layer 103 by tunnel effect, and the superconductors 101 and 10 on both sides
A small current flows between the two. The current rapidly increases when increasing the bias voltage V _B over 2.DELTA., Bias voltage and ST
The relationship between the currents flowing through the J element shows a VI characteristic as shown in FIG. Further, when the bias voltage V _B is 0, it flows so called Josephson current Cooper pair passes through the insulating layer 103 by the tunneling effect.

[0004] The basic operation principle of a particle beam detector is to convert the energy given to the detector when the particle beam enters the detector into a current or voltage signal in some form and to extract the signal. In the case of the STJ element, the bias voltage V _B is set to 2Δ or less in FIG. 11 and the quasiparticles generated by dissociation of the Cooper pair by the energy given when the particle beam is incident on the superconductor 101 or 102. Is taken out as a current, it operates as a detector. At this time, bias the voltage V _B is very small, the flow at the same time a large Josephson current and the signal current caused by the incidence of the particle beam, the original signal is buried. Since the magnitude of the Josephson current can be controlled by applying a magnetic field to the STJ element, in order to operate the STJ element as a particle beam detector, a magnetic field B having a magnitude such that the Josephson current becomes 0 is applied. It is essential.

[0005] The operating temperature of the STJ element as a particle beam detector must be sufficiently lower than the superconducting transition temperature _Tc .
It is about T _c / 10. This is because it is necessary to make thermal excitation less likely in order to minimize the noise, that is, the bias current due to thermally excited quasiparticles, which is one of the causes of deteriorating the energy resolution.

On the other hand, SQ used as a signal amplifying element
The UID is similarly configured by a combination of STJ elements, and detects a small change in the magnetic field and amplifies it. In practice, the signal current generated by the detector is guided to a coil close to the SQUID, and a change in the current is converted into a change in the magnetic field, and the change is detected and amplified by the SQUID. Therefore, the coil and the SQUID must be completely isolated from the external magnetic field.
The operating temperature of the SQUID may be _Tc or lower because the element only needs to be superconductive.

[0007]

As described above, since the signal obtained from the STJ element as a particle beam detecting element is weak, a superconducting quantum interferometer (dc-SQUID) having an STJ is used as a preamplifier. Is done. Conventional particle beam detectors using superconducting particle beam detectors were assembled by manually bonding, but the wiring picked up noise and the noise level was high, resulting in a reduction in resolution. It was not said that it had high reliability.

Further, S used as a particle beam detecting element
Each of the TJ elements is a minute one of about 100 μm square, and the detection area of the detector needs to be several mm to about 1 cm in order to perform high-precision measurement in a short time. . Therefore, it is necessary to form a system by arranging a large number of bonding elements. In order to use the STJ element under optimal conditions, it is essential to reduce the noise in the transmission of electric signals from the low-temperature section to the normal-temperature section. Specifically, either the signal is amplified by SQUID or AD conversion is performed in a low temperature part. In the case of a medium-scale STJ element array, it is sufficient to amplify the SQUID and bring it to the room temperature section. In the case of a large-scale STJ element array, it is desirable to perform AD conversion in a low-temperature section due to wiring problems. In any case, when the number of elements increases, wiring becomes difficult.

Further, in order to use the STJ element as a particle beam detecting element, it is necessary to apply a magnetic field.
ADCs using superconducting devices do not operate when a magnetic field is applied. Therefore, the detection unit and the reading SQ are simply
Simply integrating a UID or superconducting ADC monolithically does not work. The present invention has been made in view of the current state of particle beam detectors using such STJ elements, and has as its object to provide a particle beam detector having a low noise level and improved performance reproducibility. .

[0010]

According to the present invention, a chip on which an STJ element array used as a particle beam detector is integrated and a chip on which a signal processing circuit such as SQUID or superconducting ADC is integrated are separated. Make it as a chip. These chips are combined and hybridized by, for example, superconducting flip chip bonding. The above object is achieved by providing a magnetic partition with a superconducting material in a space formed between the chips so that a magnetic field can be applied only to necessary devices.

That is, a particle beam detecting apparatus according to the present invention comprises a substrate, a superconducting tunnel junction (STJ) element array, a detecting section chip having input / output terminals respectively connected to the superconducting tunnel junction element array, A particle beam detection device including a signal processing circuit that processes a signal from the conduction tunnel junction element and a signal processing chip having an input / output terminal connected to the signal processing circuit, wherein the detection unit chip and the signal processing chip are: It is characterized in that it is magnetically separated and mounted on a substrate so that a magnetic field is applied only to the detection unit chip.

An opening is provided in the substrate and a wiring layer made of a superconducting material is provided. In the detector chip, a superconducting tunnel junction element faces the opening of the substrate and its input / output terminals are provided around the opening. The signal processing chip is mounted on the board so that it is connected to the wiring layer, and the input / output terminals of the signal processing chip and the input / output terminals of the detector chip are connected by a wiring layer made of a superconductive material. It is convenient to mount it on the same side as the chip.

According to such a mounting method, the detection unit chip and the signal processing chip can be mounted on the substrate by flip-chip bonding to be hybridized. According to the flip-chip bonding, the STJ element array is directed to the substrate side, and as it is, it does not become a particle beam detector.
The light can be incident on the element array. According to this arrangement, since the signal processing chip is shielded from the incident particle beam by the substrate, it is possible to prevent the particle beam from entering the SQUID amplifier or the like constituting the signal processing circuit and causing a malfunction.

In order to prevent a magnetic field from being applied only to the detection unit chip and from applying a magnetic field to the signal processing chip, for example, the signal processing chip may be surrounded by a superconductor material so that magnetic flux does not enter. Alternatively, only the detection unit chip may be surrounded by a superconducting material in a cylindrical shape so that the magnetic flux applied to the detection device passes only inside the cylinder.

In order to sufficiently magnetically shield the signal processing chip also on the substrate side, a superconductor layer is provided on the substrate in parallel with the substrate surface, and a wiring layer made of the superconductor is insulated thereon. Is preferred. The detector needs to be kept at a sufficiently lower temperature than other signal processing circuits in order to maintain performance. However, the STJ element array of the detector chip is
Since cooling is performed only from the substrate side via bonding, sufficient cooling cannot be performed. For this reason, it is preferable that a superconducting Peltier element using an STJ element is also attached to the back surface of the detection unit chip, that is, the surface opposite to the side facing the opening of the substrate, for cooling.

The signal processing circuit of the signal processing chip is constituted by a superconducting device. The signal processing circuit includes an amplifier circuit for amplifying the output of the superconducting tunnel junction element, a digitizing circuit (ADC circuit) for AD-converting the amplified signal,
An arithmetic circuit for performing arithmetic processing on the digitized signal, a communication circuit for performing communication processing with the outside, and the like can be included. The amplifier circuit can be constituted by SQUID. ADC circuits, arithmetic circuits, communication circuits, etc. are all S
The signal processing chip can be manufactured by the existing semiconductor integrated circuit manufacturing technology.

By arranging the ADC circuit, or even the arithmetic circuit and the communication circuit in the low-temperature part cooled to an extremely low temperature, the number of wirings connecting the low-temperature part and the normal-temperature part is greatly reduced. (In the case where only the communication line is used to connect the low-temperature section and the normal-temperature section, at least two wires are required), the wiring can be simplified and the heat input to the low-temperature section can be minimized.

As described above, according to the present invention, it is possible to obtain a particle beam detector having a low noise level and improved reproducibility of performance as a detector. This particle beam detector can be used for electromagnetic waves (photons) ranging from near-infrared light to visible light, ultraviolet light, X-rays and gamma rays, charged particles such as electrons and ions, and neutral particles such as molecular beams and neutral atomic beams. Can be used to detect the particle beam.

[0019]

Embodiments of the present invention will be described below. FIG. 1 is a schematic plan view showing an example of the substrate. The substrate 10 has an opening 11 at the center and wiring layers 12a to 12d around the opening. Wiring layers 12a to 12d
Is formed by patterning a superconducting material layer, for example, an Nb layer. The wiring layers 12a to 12d
A connection is made between the input / output terminals of the detector chip mounted on the opening 11 of the “0” and the input / output terminals of the signal processing chip mounted on the peripheral area of the substrate 10. At the position where the signal processing chip is mounted, frames 13a to 13c which are slightly larger than the outer dimensions of the signal processing chip and are made of a superconducting material.
13d is formed.

FIG. 2 is a sectional view taken along the line AA of FIG.
(A) and (b) are sectional views taken along line BB of FIG. 2 and CC.
It is arrow sectional drawing. As shown in FIGS. 2 and 3, the substrate 10 is provided with Nb on an insulating plate 14 such as a flowing glass.
Is formed on one surface, and furthermore, S
The insulating layer 16 of iO ₂ or the like after having formed on one surface, a wiring layer 12a~12d consisting superconducting material is formed. The patterning of the wiring layers 12a to 12d can be performed by a known photolithography method. Signal processing chip 30
Are mounted around the wiring layers 12a to 12a.
Frames 13a to 13d made of a superconducting material such as Nb are formed so as to cover d. Wiring layers 12a-12
3d, as shown in FIG. 3A, around the conductors of the wiring layers 12a to 12d, the frames 13a to 13d made of the superconductive material do not directly contact the conductors of the wiring layers 12a to 12d. The insulating layer 17 is formed.

FIG. 4 is a schematic plan view showing an example of the detection section chip, and FIG. 5 is a schematic plan view showing an example of the signal processing chip. The detection unit chip 20 includes, for example, an STJ element array 21 in which about 100 to 10000 STJ elements are schematically arranged in FIG. 10, and input / output terminals connected to each STJ element in the array, which are arranged at the periphery of the chip. 22a-2
2d. The superconducting material that constitutes the STJ element is
For example, it can be selected from the elements shown in Table 1 below. Table 1 shows the critical temperature T _c [K] and the critical magnetic flux density H _c
[Gauss] and gap energy Δ [meV] are also shown. In addition, an alloy, an intermetallic compound, a metal oxide, or the like exhibiting superconductivity can be used.

[0022]

[Table 1]

The signal processing chip 30 includes a preamplifier, an AD
C, an arithmetic processing circuit, a communication circuit and the like are integrated, and a circuit section 31 and input / output terminals 32 electrically connected to the circuit section
Having.

FIG. 6 is a schematic diagram showing an example of a preamplifier and an ADC. The detection signal from the STJ element 40 is dc-
After amplification by SQUID41, A
The digital signal is converted by the DC circuit 50. The ADC circuit 50 includes quantum interference devices 51 to 51 whose input lines are connected in series.
54. The Josephson junction 42 of the dc-SQUID 41 does not have a hysteresis characteristic, but the Josephson junction 55 of the quantum interference devices 51 to 54 has a hysteresis characteristic. The degree of coupling between the input lines of the quantum interference elements 52 to 54 and each circuit is twice, four times, or eight times the degree of coupling with the quantum interference element 51. The signal can be digitized. The digitized detection signal is further processed by the arithmetic processing circuit 57.

FIG. 7 is a diagram for explaining a method of magnetically separating and mounting a detection unit chip and a signal processing chip on a substrate. The detection unit chip 20 includes an STJ element array 21
Are aligned with the opening 11 of the substrate 10, the input / output terminals 22a are located on the pad portions of the wiring layer 12a, the input / output terminals 22b are located on the pad portions of the wiring layer 12b, and the input / output terminals 22c are located on the wiring layer 12b. The input / output terminals 22d are connected to the pad portions of the wiring layer 12c by flip chip bonding such that they are aligned with the pad portions of the wiring layer 12d.

The signal processing chip 30 is positioned so that the surface on which the signal processing circuit 31 is formed faces the substrate, and the input / output terminals 32 are positioned on the pads of the wiring layers 12a to 12d of the substrate. They are connected by flip chip bonding. Subsequently, a hollow box-shaped magnetic shield body 60 made of a superconducting material is put on each signal processing chip. The bottom end surface of the box-shaped body 60 is placed on a frame (frame 13c in the illustrated example) made of a superconductive material formed on the substrate 10 and mechanically adhered to the lower superconductive layer.

FIG. 8 is a schematic sectional view of the substrate 10 on which the detector chip 20 and the signal processing chip 30 are mounted.
The signal processing chip 30 is surrounded by a box-shaped magnetic shield body 60 made of a superconducting material on the upper surface and front, rear, left and right surfaces, and is surrounded by a superconducting material layer 15 previously formed on the substrate 10 on the bottom surface.
It is mounted on the substrate 10 while being magnetically insulated from the surroundings. On the other hand, the detector chip 20 is not surrounded by the magnetic shield, and both are magnetically separated. Therefore, for example, by placing the entire particle beam detector in an external magnetic field, it is possible to apply a magnetic field only to the detection unit chip 20 without applying a magnetic field to the signal processing chip 30.

FIG. 9 is an explanatory view showing an example of a cooling method of the particle beam detector. In this example, the particle beam detector is a copper cold finger 7 cooled by liquid helium 3 contained in a container 70 in a cryostat.
1 is attached with the substrate 10 in contact therewith. In this way, the temperature is cooled to a low temperature of about T _c / 10, for example, 0.3 to 0.5 K, and 50 mm is applied to the STJ element array of the detection unit chip 20 by a permanent magnet or a magnet coil arranged around.
It is used by applying a magnetic field of about Gauss. The particle beam to be detected passes through a beryllium window (not shown) having a thickness of about 100 μm of the cryostat and passes through the cold finger 71.
Through the opening 72 of the substrate 10 and the opening 11 of the substrate 10 to enter the STJ element array of the detection unit chip 20.

Since the detector chip 20 is connected to the substrate 10 by flip chip bonding,
Cooling is performed only through bonding, and sufficient cooling cannot be performed as it is. Therefore, in the present invention, the superconducting Peltier element 75 also using the STJ element is attached to the back surface of the detection unit chip 20 and cooled, so that the temperature can be cooled to a low temperature of about T _c / 10. The heat generated by the superconducting Peltier device is
Through the cold finger 71.

A superconducting Peltier device is a device having a laminated structure such as a normal metal / insulator / superconductor (NIS) or a superconductor / insulator / normal metal / insulator / superconductor (SINIS). In the superconductor layer, electrons with energy equal to or greater than the gap energy can be quantum mechanically tunneled through the insulator layer to release the energy (greater than the gap energy) in the normal conductor. , Which forcibly transports heat in a direction perpendicular to the stacking plane (Appl. Phys. Lett. 68 (14), pp. 1996-1998, App
l. Phys. Lett. 70 (14), pp. 1885-11887).

[0031]

According to the present invention, the noise level is low,
A particle beam detector with improved reproducibility of performance as a detector can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an example of a substrate.

FIG. 2 is a sectional view taken along the line AA of FIG.

3A is a cross-sectional view taken along a line BB in FIG. 2, and FIG.
FIG.

FIG. 4 is a schematic plan view showing an example of a detection unit chip.

FIG. 5 is a schematic plan view illustrating an example of a signal processing chip.

FIG. 6 is a schematic diagram showing an example of a preamplifier and an ADC.

FIG. 7 is an explanatory diagram of a method of magnetically separating and mounting a detection unit chip and a signal processing chip on a substrate.

FIG. 8 is a schematic cross-sectional view of a substrate on which a detection unit chip and a signal processing chip are mounted.

FIG. 9 is a diagram illustrating an example of a cooling method of the particle beam detection device.

FIG. 10 is a schematic view of a superconducting tunnel junction element (STJ element).

FIG. 11 is a VI characteristic diagram of an STJ element.

[Explanation of symbols]

10: substrate, 11: opening, 12a to 12d: wiring layer,
13a to 13d: frame of superconducting material, 14: insulating plate, 15
... superconducting material layer, 16 ... insulating layer, 17 ... insulating layer, 20 ...
Detector chip, 21 ... STJ element array, 22a to 22
d: input / output terminal, 30: signal processing chip, 31: circuit unit, 32: input / output terminal, 40: STJ element, 41: dc
-SQUID, 42 ... Josephson junction, 50 ... ADC
Circuits 51 to 54: quantum interference device, 55: Josephson junction, 57: arithmetic processing circuit, 60: box-shaped magnetic shield, 70: container, 71: cold finger, 72: opening, 75: superconducting Peltier device , 76 ... thermal conductor, 1
00: STJ element, 101, 102: superconductor, 103
… Insulating layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiromi Sato 9-29-14, Tajima, Urawa-shi, Saitama (72) Inventor Takayuki Oku 2857-1 Okura, Okura, Wako-shi, Saitama Fine Corpora B202 No. 72 (72) Inventor Nakagawa Hiroshi 1-1-4, Umezono, Tsukuba, Ibaraki Pref., Within the Institute of Technology, Electronic Technology Research Institute (72) Inventor Masahiro Aoyagi 1-4-1, Umezono, Umezono, Tsukuba, Ibaraki, Japan (72) Invention Hiroshi Ako 1-1-4 Umezono, Tsukuba, Ibaraki Pref., National Institute of Advanced Industrial Science and Technology

Claims (6)

[Claims] 1. A substrate, a detector chip having a superconducting tunnel junction element array and an input / output terminal respectively connected to the superconducting tunnel junction element array, and processing a signal from each of the superconducting tunnel junction elements. A particle beam detection device comprising: a signal processing circuit and a signal processing chip having an input / output terminal connected to the signal processing circuit, wherein the detection unit chip and the signal processing chip have a magnetic field applied only to the detection unit chip. Characterized in that the particle beam detection device is magnetically separated and mounted on the substrate so that a voltage is applied. 2. The substrate has an opening and a wiring layer made of a superconducting material, and the detecting unit chip has a superconducting tunnel junction element array facing an opening of the substrate and an input / output terminal thereof. The signal processing chip is mounted on the substrate so as to be connected to the wiring layer provided around the opening, and the input / output terminals of the signal processing chip and the input / output terminals of the detection unit chip are made of the superconductive material. The particle beam detection device according to claim 1, wherein the particle beam detection device is mounted on the same side of the substrate as the detection unit chip so as to be connected by a wiring layer. 3. The particle beam detection device according to claim 1, wherein the signal processing chip is surrounded by a superconductor material so that a magnetic flux does not enter. 4. The substrate according to claim 1, wherein the substrate has a superconductive material layer parallel to the substrate surface, and a wiring layer made of the superconductive material is provided thereon insulated. Or the particle beam detector according to 3. 5. The particle according to claim 1, wherein the detector chip has a superconducting Peltier element mounted on a surface opposite to a side facing the opening. Line detector. 6. The signal processing circuit includes a superconducting device, an amplifier circuit for amplifying an output of the superconducting tunnel junction element, a digitizing circuit for AD-converting the amplified signal, and a digitized signal. 6. An arithmetic circuit for calculating the following formula:
Item beam detector.