WO2010064693A1 - 放射線の位置を2次元で検出する半導体検出器及びそれを用いた放射線の2次元位置検出方法 - Google Patents
放射線の位置を2次元で検出する半導体検出器及びそれを用いた放射線の2次元位置検出方法 Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/02016—Circuit arrangements of general character for the devices
- H01L31/02019—Circuit arrangements of general character for the devices for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/02024—Position sensitive and lateral effect photodetectors; Quadrant photodiodes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/1446—Devices controlled by radiation in a repetitive configuration
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
- H01L31/108—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the Schottky type
Definitions
- the present invention relates to a semiconductor two-dimensional position detector that detects a radiation position in two dimensions, which is preferably used in physical measurement, a positron emission tomography apparatus (PET), and the like, and a radiation two-dimensional position detection method using the same.
- PET positron emission tomography apparatus
- a positron emission tomography device uses a positron emitting nuclide to detect two gamma rays emitted at an angle of 180 ° when the emitted positron and the electron in the material meet and disappear, A distribution image is obtained (see Non-Patent Document 1).
- scintillator detectors are used as ⁇ -ray detectors in positron tomography apparatuses.
- the scintillator detector receives light emitted by gamma ray detection by several photomultiplier tubes, and determines which scintillator measures gamma rays from the intensity ratio of each light.
- the spatial resolution of a positron tomography apparatus based on this principle is limited to several millimeters. Therefore, the scintillator detector cannot obtain a spatial resolution of 1 mm or less, which is the same as that of X-ray CT.
- Known semiconductor detectors for detecting light or particle beams include semiconductor position detection elements (see Patent Document 1) and detectors using CdTe crystals that have a large absorption effect on gamma rays (see Patent Document 2). .
- a detector using a CdTe crystal is made of a CdTe crystal semiconductor plate having an electrically conductive electrode formed on the front and back surfaces, and takes out an electric signal through an amplifier. By using this semiconductor detector, the detector can be made small, and a 1 mm size detector can be realized. Therefore, it is possible to realize a semiconductor detector having a spatial resolution of 1 mm or less by arranging a plurality of detectors.
- Patent Document 2 uses, for example, a 20 mm square semiconductor plate in which an electrically conductive resistive electrode is formed on the front surface and an electrically conductive electrode is formed on the rear surface, and electrical signals from four corners of the electrically conductive resistive electrode are used.
- a detector that two-dimensionally detects a detection position of a gamma ray in a semiconductor plate using the above ratio is disclosed. In this detector, it is sufficient to prepare four amplifiers.
- FIG. 12 is a schematic diagram showing a semiconductor two-dimensional position detector 50 disclosed in Patent Document 2.
- the thin semiconductor crystal plate 51 is made of a CdTe crystal, one surface is an electrically conductive resistive electrode 52, and the other surface is an electrically conductive electrode 53.
- an indium electrode 52 is formed on one surface and a platinum electrode 53 is formed on the other surface.
- the indium electrode is made of indium thin and, for example, has an electric conduction resistance by depositing about 600 mm. Thereby, the indium vapor deposition surface of the semiconductor crystal plate 51 has electric conduction resistance, and the semiconductor crystal plate 51 operates as a Schottky type radiation detector.
- the semiconductor two-dimensional position detector 50 is provided with terminals at the four corners A, B, C, and D of the electrically conductive resistive electrode surface, each connected to the amplifier circuit 55, and the output generated at the four terminals.
- the calculated position coordinates (X, Y) (hereinafter referred to as temporary position coordinates) of the gamma rays on the semiconductor plate 51 are expressed as V A , V B. , V C , and V D (see Patent Document 2).
- FIG. 13 is a diagram showing the irradiation position of the radiation 57 in the conventional semiconductor two-dimensional position detector 50.
- FIG. 14 is a diagram showing the result of position detection by the conventional semiconductor two-dimensional position detector 50, and shows temporary position coordinates 59 calculated using output signals V 1 to V 4 generated at four terminals.
- the detection result by the temporary position coordinate 59 is a distribution in which the position obtained by the signal and the actual radiation detection position are nonlinear, asymmetric and highly distorted. This is insufficient to identify the detection position of the radiation 57.
- Patent Document 3 discloses a semiconductor two-dimensional position detector in which each side is not a quadrangle on a semiconductor substrate but has an arc-shaped resistance layer, and currents are output using four points as apexes of each side as output electrodes. It is described that the incident position of ⁇ rays can be detected without distortion by detection.
- Patent Document 4 a radiation position detection device is disclosed, and two-dimensional position detection is performed by a cascade-connected resistor. Two amplifiers connected to the resistor and two amplifiers are connected to this amplifier. A complicated circuit configuration is composed of four A / D converters, two position calculators, one adder, one wave height discriminator, and one control signal generator.
- Patent Documents 5 and 6 CdTe, CdZnTe, or BrTl is used as a semiconductor substrate used in a semiconductor two-dimensional position detector, and linear resistance lines are arranged in parallel (Patent Document 5) or a matrix. Forming a structure (Patent Documents 5 and 6) is disclosed.
- the detection elements are arranged in a two-dimensional matrix. In this case, it is necessary to provide a switching element and an amplifier for each detection element in the image processing, and the circuit configuration becomes complicated as in Patent Document 4.
- Patent Document 7 discloses a semiconductor two-dimensional position detector in which Si is used as a semiconductor substrate and Al electrodes are formed in a stripe shape on the surface layer.
- the position obtained by the signal and the actual radiation detection position are non-linear, asymmetric and highly distorted, and the radiation detection position is determined. It was insufficient for identification. Further, in order to solve this problem in the past, the electrode structure on the position detection surface is not suitable for practical use because it has a complicated shape such as an arc shape (see, for example, Patent Documents 1 and 3). In addition, when a circuit directly joined with a circuit such as an amplifier is stacked on the back surface of the detector, a portion insensitive to radiation is formed, which is not suitable for PET.
- a semiconductor position detector for two-dimensionally detecting the position of radiation includes a semiconductor substrate and a surface of the semiconductor substrate arranged in parallel at a predetermined interval in the X direction.
- a second configuration of the semiconductor position detector for two-dimensionally detecting the position of radiation according to the present invention is a Y direction in which a semiconductor substrate and a surface of the semiconductor substrate are juxtaposed at a predetermined interval in the X direction.
- First to nth (n is an integer greater than or equal to 2) stripe electrodes parallel to each other, a plurality of resistors connected between the upper ends of the first to nth stripe electrodes, and the first to nth stripes
- a plurality of resistors connected between the lower end portions of the electrodes, a first signal output terminal connected to the lower end portion of the first stripe electrode via the resistor, and a resistor at the lower end portion of the nth stripe electrode
- a second signal output terminal connected via a resistor, a fourth signal output terminal connected via a resistor to the upper end of the first stripe electrode, and a resistor connected to the upper end of the nth stripe electrode.
- a third signal output terminal connected via the semiconductor substrate and the back of the semiconductor substrate
- Each of the first to nth stripe electrodes is formed of m strip electrodes formed in the Y direction and separated from each other, and each strip electrode is formed along the Y direction. Adjacent strip electrodes are connected by resistors to form respective stripe electrodes, and output signals from radiation incident on an arbitrary point of the semiconductor substrate are obtained from first to fourth signal output terminals. .
- the resistance connected between the upper end portions and the lower end portions of the stripe electrodes is preferably formed such that the resistance value thereof can be adjusted.
- the resistance ratio between the resistance of each stripe electrode and the resistance connected between the upper end portions and / or the lower end portions of the stripe electrodes is: Preferably, it is 10: 1 to 100: 1.
- the first to nth stripe electrodes are preferably separated from each other along the Y direction.
- the strip electrodes forming the first to nth stripe electrodes are preferably separated from each other along the X direction.
- the stripe electrode may be a Schottky type electrode having high electrical conductivity resistance, and the electrode disposed on the back surface of the semiconductor substrate may be an electrode having high electrical conductivity.
- the semiconductor substrate is preferably made of any one of CdTe, CdZnTe, and BrTl, and the electrode is preferably made of indium or platinum.
- a calculation unit that calculates the position of radiation from the output signal is provided, and the calculation unit outputs voltages output from the first to fourth signal output terminals as V 1 , V 2 , V, respectively.
- V 4 by the following equation (1) and (2), radiation of temporary position coordinates (X i, Y j) was computed, tentative position coordinates (X i, Y j) with, Radiation detection position coordinates (X p , Y q ) are calculated by the following equations (3) and (4).
- the functions f (X i , Y j ) and g (X i , Y j ) in the above equations (3) and (4) are used to express the radiation spot on the stripe electrode of the semiconductor two-dimensional position detector. After irradiating at intervals in the Y direction and calculating the temporary position coordinates of each irradiation point, assuming a correction function between the position coordinates of each irradiation point and the temporary position coordinates of each irradiation point, This is obtained by fitting as a function for reproducing the position coordinates of the irradiation point.
- the X p and X i, the Y q calculated by the following equation (5) or (6), radiation corrected position coordinates (X p, Y q) may be calculated.
- This correction position coordinate is also called a detection position coordinate.
- the coefficients a, b and c of the quadratic function in the equation (5) are arbitrary constants, and d * is a standard constant.
- the coefficients a ′, b ′ and c ′ of the quadratic function in the equation (6) are arbitrary constants, and d ′ is a standard constant.
- a method for detecting a two-dimensional position of radiation includes first to nth (n Are arranged in parallel, the upper ends of the first to nth stripe electrodes are connected to each other via a resistor, and the lower ends of the first to nth stripe electrodes are connected to each other.
- Each is connected via a resistor, one end of the resistor is connected to the lower end of the first stripe electrode, the first signal output terminal is arranged at the other end of the resistor, and the lower end of the nth stripe electrode
- One end of the resistor is connected to the second end, the second signal output terminal is disposed on the other end of the resistor, one end of the resistor is connected to the upper end of the first stripe electrode, and the fourth end is connected to the other end of the resistor.
- the signal output terminal is arranged, and one end of the resistor is connected to the upper end of the nth stripe electrode.
- a third signal output terminal is disposed at the other end of the resistor, an electrode is disposed on the back surface of the semiconductor substrate, and an output signal from radiation incident on the semiconductor substrate is output from the first to fourth signal output terminals. It is characterized by obtaining.
- each of the first to nth stripe electrodes is formed from m strip electrodes formed in the Y direction and separated from each other, and the strip electrodes adjacent to each other along the Y direction of each strip electrode are resisted.
- Each stripe electrode may be formed by connecting via the.
- the X p and X i, the Y q calculated by the above equation (5) or (6), the radiation detection position coordinates (X p, Y q) may be calculated.
- the semiconductor two-dimensional position detector for detecting the position of radiation in two dimensions has only four signal output terminals, the number of signal amplifiers can be greatly reduced. Further, by configuring this semiconductor two-dimensional position detector in a multiplex manner, it is possible to specify a radiation detection position with an accuracy shorter than 1 mm in three dimensions, and to a positron emission tomography apparatus having a spatial resolution of 1 mm or less. Can be applied. Further, since the detection sensitivity portion is the entire surface of the semiconductor detector, the detector block in which the detection detector is multiplexed does not have a radiation insensitive portion, and is suitable as a PET detector block.
- the radiation two-dimensional position detection method of the present invention when radiation is irradiated, signals from the four signal output terminals of the plurality of stripe electrodes are calculated, and further, correction calculation is performed, whereby 1 mm in the two-dimensional direction. It becomes possible to specify the radiation irradiation position with shorter accuracy.
- FIG. 2 is a cross-sectional view taken along line II-II in FIG. It is sectional drawing which shows another structure of a semiconductor two-dimensional position detector. It is a top view which shows the radiation irradiation position to a semiconductor two-dimensional position detector. It is a figure which shows the temporary position coordinate acquired with the semiconductor two-dimensional position detector with respect to the irradiation position of the radiation shown in FIG. It is a flowchart which shows the process of calculating a detection position coordinate ( Xp , Yq ).
- FIG. 10 is a cross-sectional view taken along line VIII-VIII in FIG. 9.
- FIG. It is an equivalent circuit diagram which shows resistance arrangement
- FIG. It is a figure which shows the irradiation position of the radiation in the conventional semiconductor two-dimensional position detector. It is a figure which shows the position detection result by the conventional semiconductor two-dimensional position detector.
- SYMBOLS 1,30 Semiconductor two-dimensional position detector 2: Semiconductor substrate 2A: The surface 2B of a semiconductor substrate: The back surface 2C of a semiconductor substrate: The groove part of a semiconductor substrate 3: Stripe electrodes 4, 5: Resistors 6, 8, 10, 12: Output Resistor 7: first signal output terminal 9: second signal output terminal 11: fourth signal output terminal 13: third signal output terminal 15: Schottky electrode 16: radiation 17-20 : Signal detector 22: Calculation unit 25: Radiation irradiation position 26: Temporary position coordinate 33: Stripe electrode 33 ij : Strip electrode 35: Resistance for connecting strip electrode
- FIG. 1 is a plan view showing the configuration of a semiconductor two-dimensional position detector 1 for two-dimensionally detecting the position of radiation according to the first embodiment of the present invention.
- FIG. It is sectional drawing along the II line.
- the semiconductor two-dimensional position detector 1 includes a semiconductor substrate 2 and first to nth (n is 2) parallel to the Y direction, juxtaposed on the surface 2A of the semiconductor substrate 2 with a predetermined interval in the X direction.
- (Integer) stripe electrode 3 a plurality of resistors 4 connected between upper end portions 3A of first to nth stripe electrodes, and between lower end portions 3B of first to nth stripe electrodes 3.
- a plurality of resistors 5 connected, a first signal output terminal 7 connected to the lower end 3B of the first stripe electrode 31 via an output resistor 6, and an nth stripe electrode 3n
- a second signal output terminal 9 connected to the lower end 3B via the output resistor 8 and a fourth signal output connected to the upper end 3A of the first stripe electrode 31 via the output resistor 10
- a third signal output terminal 13 connected via the resistor 12 and an electrode 15 disposed on the back surface 2B of the semiconductor substrate 2 are provided.
- the semiconductor two-dimensional position detector 1 is a so-called Schottky diode comprising a first to nth stripe electrode 3 disposed on the front surface 2A of the semiconductor substrate 2 and an electrode 15 disposed on the back surface 2B side. It is.
- the semiconductor two-dimensional position detector 1 of the first embodiment is biased in the reverse direction. In this state, a depletion layer is formed in the semiconductor substrate 2, and output signals from the radiation 16 incident on the semiconductor substrate 2 are output from the first to fourth signal output terminals 7, 9, 11, 13. Obtainable.
- the output from the signal output terminals 7, 9, 11, and 13 is a voltage or a current.
- the semiconductor two-dimensional position detector 1 has, for example, n stripe electrodes 3 made of, for example, eight indiums extending in the Y direction and having a constant width in the X direction on the surface 2A of the semiconductor substrate 2 made of, for example, CdTe crystal. They are lined up in parallel at a distance of.
- the electrode 15 on the back surface 2B side of the semiconductor substrate 2 can be formed of, for example, an electrode made of platinum (Pt).
- the stripe electrode has high electrical conduction resistance and a Schottky electrode can be used.
- positioned at the back surface of a semiconductor substrate can be made into an electrode with high electrical conductivity.
- FIG. 3 is a cross-sectional view showing another configuration of the semiconductor two-dimensional position detector 1.
- the semiconductor two-dimensional position detector 1A shown in FIG. 3 is different from the semiconductor two-dimensional position detector 1 shown in FIG. 2 in that each of the stripe electrodes 3 arranged on the surface 2A of the semiconductor substrate 2 is separated by an elongated groove 2C. There is in point.
- each of the stripe electrodes 3 is electrically divided.
- the groove 2C can be formed by forming a thin film made of a metal material to be the stripe electrode 3 on the semiconductor substrate 2 by vacuum deposition, and then cutting (cutting) using diamond or photolithography and etching.
- the metal material used for the stripe electrode 3 is, for example, indium.
- One stripe electrode 3 is, for example, an indium vapor deposition film having a length in the Y direction of 20 mm, a width in the X direction of 1.1 mm, and a thickness of 500 mm.
- the resistance value between both ends of the single stripe electrode 3 is, for example, 1 M ⁇ .
- the pitch between the adjacent stripe electrodes 3, that is, the distance between the center lines of the adjacent stripe electrodes 3 is 1.2 mm, for example. In this case, the gap between adjacent stripe electrodes 3 or the width of the groove 2C is about 0.1 mm.
- a signal amplifier (not shown) may be provided between the signal detectors 17 to 20 connected to the first to fourth signal output terminals 7, 9, 11, and 13 to adjust the output signal. .
- charge sensitive amplifiers can be used. In the following description, the signal detectors 17 to 20 will be described as charge sensitive amplifiers.
- each of the adjacent stripe electrodes 3 is electrically connected via a resistor 4.
- each of the adjacent stripe electrodes 3 is electrically connected via the resistor 5.
- the values of the resistors 4 and 5 are, for example, 20 k ⁇ .
- the resistors 4 and 5 are inserted in order to distinguish the output of each stripe electrode 3.
- an external resistor connected to the stripe electrode 3 or a resistor formed on the semiconductor substrate 2 can be used.
- the resistance values of the resistors 4 and 5 may be formed to be adjustable. When the resistors 4 and 5 are formed of a metal thin film, the resistance value can be adjusted by laser trimming or the like.
- the first to fourth signal output terminals 7, 9, 11, and 13 are connected to the first to fourth signal detectors 17 to 20, respectively, and the first to fourth signal detectors 17 to 20 outputs an output signal of V 1 to V 4 .
- the output signals V 1 to V 4 are input to the calculation unit 22.
- the calculation unit 22 includes a computer such as an A / D converter, an interface circuit (I / O), and a RISC.
- the distance from the incident position of the radiation 16 to both ends of the stripe electrode 3 is proportional to the resistance value in the Y direction, it is detected by, for example, the first and fourth signal detectors 17 and 20 on both sides in the Y direction. From the voltage ratio, the incident position of the radiation 16 in the Y direction can be calculated. In order to calculate the incident position of the radiation 16 in the Y direction, second and third signal detectors 18 and 19 may be further used.
- the distance from the incident position of the radiation 16 to both ends of the stripe electrode 3 is proportional to the resistance value in the Y direction, but the current flowing through the resistance is inversely proportional. Since the current is proportional to the induced charge, the output of the charge-sensitive amplifier increases in proportion to the current. For this reason, the incident position of the radiation 16 in the Y direction is calculated from the signals detected by, for example, the first, second, third, and fourth charge sensitive amplifiers 17 to 20 on both sides in the Y direction. Can do.
- the distance from the stripe electrode 3 on which the radiation 16 is incident to both ends in the X direction is proportional to the resistance value in the X direction. Since the stripe electrodes 3 are sequentially connected via the resistors 4 and 5, the number of resistors 4 and 5 between them increases and the resistance value increases as the distance in the X direction increases. Therefore, the incident position of the radiation 16 in the X direction can be calculated from the ratio of the voltages detected by, for example, the first and second signal detectors 17 and 18 on both sides in the X direction. In order to calculate the incident position of the radiation 16 in the X direction, second and third signal detectors 18 and 19 may be further used.
- the incident position of the radiation 16 in the Y direction can be calculated from the signals detected by the first, second, third, and fourth charge sensitive amplifiers 17 to 20. Since there are resistors 4 and 5 between the adjacent stripe electrodes 3, information for identifying which stripe electrode 3 has generated current can be obtained. For convenience of calculation, it is desirable that the resistance values of the resistors 4 and 5 are equal.
- the width of the groove 2C be as narrow as possible.
- the position resolution in the X direction is improved as the stripe electrode 3 is narrower.
- the narrower the width of the stripe electrode 3 the larger the ratio of the width of the groove 2C to the electrode width, the higher the ratio of the area of the groove 2C to the entire substrate, and the lower the detection accuracy.
- the signal detector on the same side across the stripe electrode 3 becomes close to the direct connection state, and the current generated by the incidence of the radiation 16 and other noise currents are reduced. It becomes difficult to identify.
- the signal detectors on the same side are, for example, the first signal detector 17 and the second signal detector 18 or the fourth signal detector 19 and the third signal detector 20.
- charge-sensitive amplifiers can be used as the first to fourth signal detectors 17 to 20, charge-sensitive amplifiers can be used.
- the stripe electrode 3 and the resistance 4 are preferably 10: 1 to 100: 1. In the measurement example described later, the resistance value of the stripe electrode 3 was 1 M ⁇ , and the preferable resistance values of the resistors 4 and 5 were 10 k ⁇ to 40 k ⁇ .
- FIG. 4 is a plan view showing the irradiation position of the radiation 16 on the semiconductor two-dimensional position detector 1.
- the semiconductor substrate 2 is made of CdTe and has eight rows of stripe electrodes 3.
- One of the stripe electrodes 3 is an indium vapor deposition film having a length in the Y direction of 20 mm, a width in the X direction of 1.1 mm, and a thickness of 500 mm.
- the resistance value between one end of the stripe electrode 3 is 1 M ⁇ .
- the pitch between the adjacent stripe electrodes 3 (the distance between the center lines of the adjacent electrodes 3) is 1.2 mm. In this case, the width of the groove 2C between the electrodes of the adjacent stripe electrodes 3 is about 0.1 mm.
- the electrode 15 on the back surface 2B of the semiconductor substrate 2 was made of platinum. A portion indicated by a cross in the figure indicates an irradiation position 25 of the radiation 16. As radiation 16, alpha rays from a 241 Am radiation source were used.
- FIG. 5 is a diagram showing temporary position coordinates 26 acquired by the semiconductor two-dimensional position detector 1 with respect to the irradiation position 25 of the radiation 16 shown in FIG.
- the horizontal axis and the vertical axis in the figure correspond to the plan view of FIG.
- the temporary position coordinates 26 of the radiation 16 in the X and Y directions are separated to such an extent that they can be discriminated, and compared to the conventional semiconductor two-dimensional position detector 50 shown in FIG. It has been found that the resolution at is significantly improved.
- the X direction is substantially equally spaced.
- the Y direction is greatly distorted particularly in the central portion, and the actual irradiation position 25 of the radiation 16 is not sufficiently reproduced.
- FIG. 6 is a flowchart illustrating a process of calculating the detection position coordinates (X p , Y q ).
- step ST1 in order to check the detection position accuracy of the semiconductor two-dimensional position detector 1, the entire surface is irradiated with gamma rays by a 22 Na ray source or the like.
- step ST2 the calculation value distribution is measured, the discrimination performance in the X direction is confirmed, and the values of the resistors 4 and 5 are adjusted.
- step ST3 If the position detection of the X axis and the discrimination performance in the X direction can be confirmed, the process proceeds to step ST3. On the other hand, if the position detection of the X axis and the discrimination performance in the X direction are insufficient, the process returns to step ST1.
- step ST3 the resistance value r in the X direction is determined.
- step ST4 irradiation with alpha rays or the like is performed by a 241 Am radiation source (collimated to 0.5 mm).
- Alpha rays are irradiated to the irradiation position 25 indicated by the crosses in FIG. 4 at an interval of 2 mm in the Y direction in the center of each stripe electrode 3 in the X direction, and temporary position coordinates 26 are calculated. Irradiation and calculation were repeated at one irradiation point 4, and each point was measured for 10 minutes.
- step ST5 the detection position coordinates in the Y direction are calculated in the same manner as in the X direction. If necessary, fitting to a quadratic curve described later is performed in step ST6, and the measurement ends. As a result, the temporary position coordinates 26 of the radiation 16 were obtained as shown in FIG.
- the temporary position coordinate groups arranged in the X direction are distributed at equal intervals in the X direction.
- the position of Y j in the temporary position coordinate (X i , Y j ) group arranged in the X direction is recessed in the Y direction.
- the detection position coordinates (X p , Y q ) of the radiation 16 are calculated from the temporary position coordinates (X i , Y j ) using the following relational expressions (3) to (5).
- Equation (5) the X p and X i, the Y q, can be calculated by dividing the quadratic function of the X i to Y j.
- the following formula (6) may be used.
- (6) is a X p and X i, the Y q, it can be calculated by multiplying the quadratic function of the X i to Y j.
- the coefficients a ′, b ′, and c ′ of the quadratic function in the above equation (6) are arbitrary constants, and d ′ is a standard constant.
- FIG. 7 is a diagram illustrating a result of deriving the detected position coordinates (X p , Y q ) from the temporary position coordinates (X i , Y j ) using the expressions (3) and (4). It can be seen that the measurement points correspond to the irradiation positions indicated by x in FIG. As apparent from FIG. 7, in the detection position coordinates (X p , Y q ), the interval in the X direction is 1.2 mm, the interval in the Y direction is 2 mm, and the position resolution in the Y direction is 1 mm. I understand that.
- the detected position coordinates (X p , Y q ) obtained by correcting the expressions (3) and (4) and the actual radiation. It can be seen that 16 detection positions coincide with each other and a detection result with high position accuracy is obtained.
- X p is equal to X i.
- Y q is given by Equations (5) and (6), it is a great feature that Y j is obtained by multiplying or dividing Y j by a quadratic function of X i .
- the temporary position coordinate group is performing fitting as being the Y j on the quadratic curve of X i, it is possible to choose the appropriate correction function.
- FIG. 8 is a graph showing the dependency of the resistances 4 and 5 on the resolution in the X and Y directions, where (A) shows the half width (FWMH) in the X direction and (B) shows the half value in the Y direction.
- the value range (FWMH) is shown.
- the horizontal axis in FIG. 8 is the resistance value (k ⁇ ), and the vertical axis in FIG. 8 is the half-value width (mm).
- the half width in the X direction is about 0.3 mm or more when the resistance values of the resistors 4 and 5 are 20 k ⁇ or less.
- the half-value width in the X direction is about 0.3 mm to 0.25 mm when the resistance values of the resistors 4 and 5 are 20 k ⁇ or more to 100 k ⁇ , and the half-value width decreases. From this, it was found that when the resistance values of the resistors 4 and 5 are 20 k ⁇ or less, the half-value width in the X direction increases, that is, the spatial resolution of the semiconductor two-dimensional position detector 1 deteriorates.
- the resistance value of the stripe electrode 3 is 1 M ⁇ as described above. In this case, the ratio between the resistance value of the stripe electrode (1 M ⁇ ) and the resistance (20 k ⁇ ) of the resistances 4 and 5 connected between the upper ends of the stripe electrode 3 is 50: 1, and the spatial resolution is deteriorated. do not do.
- the half-value width in the Y direction has a minimum resolution when the resistance values of the resistors 4 and 5 are 20 k ⁇ , and the half-value width increases as the resistance values of the resistors 4 and 5 increase.
- the ratio of the resistance value (1 M ⁇ ) of the stripe electrode to the resistance (20 k ⁇ ) of the resistances 4 and 5 connected between the upper ends of the stripe electrode 3 is 50: 1, and the spatial resolution is Does not deteriorate.
- the thickness of indium needs to be 150 to 600 mm. There is. With an indium thickness in this range, the resistance value of the stripe electrode 3 is 1 M ⁇ to 4 M ⁇ . Therefore, in order not to deteriorate the spatial resolution of the semiconductor two-dimensional position detector 1, the resistance values of the resistors 4 and 5 may be selected to be 1/10 to 1/100 of the resistance value of the stripe electrode 3. .
- alpha rays are exemplified as the radiation source.
- the present invention can be similarly applied to other radiation sources such as gamma rays.
- FIG. 9 is a plan view showing a configuration of a semiconductor two-dimensional position detector 30 according to the second embodiment of the present invention
- FIG. 10 is a cross-sectional view taken along line VIII-VIII in FIG.
- the semiconductor two-dimensional position detector 30 of the second embodiment differs from the semiconductor two-dimensional position detector 1A of the first embodiment shown in FIG. 3 in the structure of the stripe electrodes 33 in each column.
- a plurality of later-described strip electrodes 33 ij separated by the Y-direction groove 2C and the X-direction groove 2D are connected via the resistor 35 only in the Y direction to form the stripe electrode 33. Since other configurations are the same as those of the semiconductor two-dimensional position detectors 1 and 1A of the first embodiment, the description thereof is omitted.
- the strip electrode 33 is composed of a plurality of strip electrodes 33 ij arranged in a matrix of m rows ⁇ n columns.
- a row consists of natural numbers up to m when i is 2 or more
- a column consists of natural numbers up to n when j is 2 or more. Since the strip electrode connecting resistors 35 for connecting the strip electrodes 33 ij are also arranged in a matrix, each of them is denoted as 33 ij or r ij .
- FIG. 11 is an equivalent circuit diagram showing a resistor arrangement of the semiconductor two-dimensional position detector 30 of the second embodiment.
- the resistance of the resistor 35 ij in the first row and the first column is r 11
- the resistance values of the resistors 4 and 5 connecting the stripe electrodes 33 j juxtaposed in the column direction are R1 and R2.
- r ij is set to the same resistance value r
- R1 and R2 are set to the same resistance value R.
- the resistance value r is larger than the resistance value R. That is, r> R.
- the electrode formed by connecting the strip electrodes 33 jk in the j-th column (k is a natural number equal to or less than m) to each other by the resistor r j in the j-th column is referred to as a stripe electrode 33 j .
- the state where the strip electrodes 33 j in the j-th column are connected to each other by the resistor r j in the j-th column is referred to as a stripe electrode 33 j .
- the current generated by the radiation 16 does not flow to the stripe electrode 33 j connected by the resistance r j of the other column. Therefore, the current generated by the radiation 16 is divided by the division ratio of the resistance value r in the same column where the radiation is detected.
- the temporary position coordinates 26 and the detected position coordinates of the radiation can be calculated by the above formulas (1) to (6).
- the strip electrodes 33 ij are arranged in a matrix and the column stripe electrodes 33 j are connected by resistors 35, so that the position resolution of radiation detection in the X direction and the Y direction can be reduced.
- the two-dimensional position detectors 1 and 1A can be improved to the same level or higher.
- the strip electrode 33 ij has been described as an electrode having high electrical conductivity.
- the stripe electrode 3 and the strip electrode 33 ij are shot. It may be a key electrode.
- the electrode 15 formed on the back surface 2B side of the semiconductor substrate 2 may be an electrode having high electrical conductivity.
- the temporary position coordinates 26 in the Y direction of the radiation are corrected by calculation.
- the semiconductor two-dimensional position detector 30 it is predicted at the time of design that the temporary position coordinates 26 are distorted in the Y direction, and the resistance value r is changed so as to reduce the distortion in the Y direction during the manufacturing process. May be.
- the surfaces of the platinum electrodes 15 of the semiconductor substrate 2 made of CdTe crystal are pasted together with a paste having electrical conductivity.
- a semiconductor detector block capable of measuring the position of gamma rays three-dimensionally is formed by alternately laminating this with a very thin insulating thin film.
- Which semiconductor substrate 2 of the semiconductor detector block has the gamma ray measured is determined by the simultaneous counting of the platinum electrode 15 and the stripe electrode 3 made of indium.
- the method for detecting the two-dimensional position of the radiation 16 according to the present invention can also be applied to a semiconductor detector block capable of measuring the position of gamma rays three-dimensionally.
- the semiconductor detector blocks are arranged in several layers and arranged in a circular or opposed manner.
- the semiconductor detector block has a structure that moves in the radial direction or the opposite direction.
- a positron emission tomography apparatus with a packing ratio of 100% is realized by arranging the electrode surface of the semiconductor detector block perpendicularly to the gamma ray detection direction.
- the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention.
- the width and length of the stripe electrode 3, the resistors 4 and 5 connected to the stripe electrode 3, and the resistors 6 and 8 connected to the stripe electrode 3 and the first to fourth signal output terminals 7, 9, 11 and 13 , 10, 12 and the like can be appropriately designed according to the position detection accuracy of the target radiation 16.
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Abstract
Description
したがって、シンチレーター検出器では、X線CT並みの1mm以下の空間分解能を得ることができない。
本発明の他の目的は、上記半導体2次元位置検出器を用いて放射線の2次元位置を検出する方法を提供することにある。
後述する数式(3)及び(4)で位置弁別を行うためには、各ストライプ電極の抵抗とストライプ電極の上端部同士間及び/又は下端部同士間に接続される抵抗との抵抗比は、好ましくは、10:1~100:1である。
第1~第nの各ストライプ電極は、好ましくは、Y方向に沿って互いに溝分離されている。第1~第nの各ストライプ電極を形成するストリップ電極同士が、好ましくは、X方向に沿って互いに溝分離されている。
ストライプ電極は電気伝導抵抗性が高く且つショットキー型電極であり、前記半導体基板の裏面に配置された電極は電気伝導性の高い電極としてもよい。
前記半導体基板は、好ましくは、CdTe、CdZnTe及びBrTlの何れかからなり、電極は、好ましくはインジウム又は白金からなる。
上記構成において、第1~第nの各ストライプ電極を、Y方向に形成されかつ互いに分離されたm個のストリップ電極から形成し、各ストリップ電極のY方向に沿って隣り合うストリップ電極同士を抵抗を介して接続して各ストライプ電極を形成してもよい。
2:半導体基板
2A:半導体基板の表面
2B:半導体基板の裏面
2C:半導体基板の溝部
3:ストライプ電極
4,5:抵抗
6,8,10,12:出力用の抵抗
7:第1の信号出力用端子
9:第2の信号出力用端子
11:第4の信号出力用端子
13:第3の信号出力用端子
15:ショットキー電極
16:放射線
17~20:信号検出器
22:演算部
25:放射線の照射位置
26:仮位置座標
33:ストライプ電極
33ij:ストリップ電極
35:ストリップ電極接続用の抵抗
〔第1の実施の形態〕
図1は、本発明の第1の実施形態に係る放射線の位置を2次元で検出するための半導体2次元位置検出器1の構成を示す平面図であり、図2は、図1のII-II線に沿った断面図である。
この半導体2次元位置検出器1は、半導体基板2と、この半導体基板2の表面2AにX方向に所定の間隔を置いて並置された、Y方向と平行な第1~第n(nは2以上の整数)のストライプ電極3と、第1~第nのストライプ電極の上端部3A同士間に接続される複数の抵抗4と、第1~第nのストライプ電極3の下端部3B同士間に接続される複数の抵抗5と、第1のストライプ電極31の下端部3Bに出力用の抵抗6を介して接続される第1の信号出力用端子7と、第nのストライプ電極3nの下端部3Bに出力用の抵抗8を介して接続される第2の信号出力用端子9と、第1のストライプ電極31の上端部3Aに出力用の抵抗10を介して接続される第4の信号出力用端子11と、第nのストライプ電極3nの上端部3Aに出力用の抵抗12を介して接続される第3の信号出力用端子13と、半導体基板2の裏面2Bに配置された電極15と、を備えている。第1~第nのストライプ電極3は、各列を示すのに、例えば1列目のストライプ電極3は、31と表記する。
ここで、半導体2次元位置検出器1は、半導体基板2の表面2Aに配置される第1~第nのストライプ電極3と、裏面2B側に配置される電極15と、からなる所謂ショットキーダイオードである。
ここで、ストライプ電極は、電気伝導抵抗性が高く且つショットキー型電極を用いることができる。また、半導体基板の裏面に配置される電極は電気伝導性の高い電極とすることができる。
なお、第1~4の信号出力用端子7,9,11,13と接続されている信号検出器17~20の間に信号増幅器(図示せず)を設け、出力信号を調整してもよい。信号検出器17~20としては、電荷有感型増幅器を用いることができる。以下の説明では、信号検出器17~20は電荷有感型増幅器として説明する。
上記第1実施形態に係る半導体2次元位置検出器1における電流経路を説明する。
半導体2次元位置検出器1へ放射線16が照射され、ストライプ電極3に衝突することで生じた電流は、ストライプ電極3の両端側へ流れる。図12のような従来の面状の電極の場合、電流は二次元的な方向へ流れるのに対し、半導体2次元位置検出器1では一次元的な方向へ流れる。つまり、面状の電極の場合、電流は放射線16の衝突位置から多方向へ流れるのに対し、半導体2次元位置検出器1では各ストライプ電極3が分離されX方向への流れが制限されるため、ストライプ電極3が伸びているY方向へ電流が流れる。
放射線16の入射位置からストライプ電極3の両端部までの距離とY方向の抵抗値とは比例するが、抵抗を流れる電流は反比例する。電流は誘起電荷に比例するので、電流に比例して電荷有感型増幅器の出力が増大する。このため、Y方向の両側にある、例えば第1、第2、第3及び第4の電荷有感型増幅器17~20で検出された信号から、Y方向における放射線16の入射位置を算出することができる。
これらの事情に鑑み、検出すべき電流とノイズ電流との識別性を維持しつつ仮位置座標(Xi,Yj)におけるY方向の歪みを抑えることを考慮し、ストライプ電極3と抵抗4,5との抵抗比は10:1~100:1とすることが望ましい。後述する測定例において、ストライプ電極3の抵抗値は1MΩで、抵抗4,5の好ましい抵抗値は、10kΩから40kΩであった。
第1の実施形態に係る半導体2次元位置検出器1における放射線16の入射位置の算出方法について説明する。
第1~第4の信号検出器17~20の出力信号V1~V4が、演算部22において、演算処理され放射線16の入射位置が算出される。具体的には、出力信号V1~V4を基に、下記(1)式及び(2)式によって仮位置座標(Xi,Yj)を算出する。
半導体2次元位置検出器1を用いた放射線16の検出例1について説明する。
図4は、半導体2次元位置検出器1への放射線16の照射位置を示す平面図である。図4に示す半導体2次元位置検出器1は半導体基板2がCdTeからなり、8列のストライプ電極3を有している。ストライプ電極3の1本は、Y方向の長さが20mm、X方向の幅は1.1mm、厚さ500Å厚のインジウム蒸着膜である。このストライプ電極3の1本の両端間の抵抗値は1MΩである。隣り合うストライプ電極3の間のピッチ(隣り合う電極3の中心線と中心線の距離)は、1.2mmである。この場合、隣り合うストライプ電極3の電極間の溝2Cの幅は0.1mm程度となっている。半導体基板2の裏面2Bの電極15は白金で形成した。図中の×印で示す箇所は、放射線16の照射位置25を示している。放射線16として、241Am線源によるアルファ線を用いた。
図5から明らかなように、放射線16のXY方向の仮位置座標26は判別可能な程度に分離されており、図12で示した従来の半導体2次元位置検出器50に比較して2次元平面における分解能が著しく向上していることが分かった。特に、X方向は概ね等間隔である。しかしながら、Y方向では特に中央部で大きく歪んでおり、実際の放射線16の照射位置25を十分再現していないことが判明した。
そこで、仮位置座標(Xi,Yj)を基に、更に演算処理を行い、検出位置座標(Xp,Yq)を導出する。
図6は、検出位置座標(Xp,Yq)を算出する工程を示すフローチャートである。図6に示すように、最初にステップST1で、半導体2次元位置検出器1の検出位置精度を調べるため、22Na線源等によるガンマ線の全面照射を行う。
ステップST2で、演算値分布の測定、X方向の弁別性能の確認及び上記抵抗4,5の値を調整する。X軸の位置検出とX方向の弁別性能の確認ができた場合には、ステップST3に進む。一方、X軸の位置検出やX方向の弁別性能が不十分な場合には、ステップST1に戻る。
ステップST4では、241Am線源(0.5mmにコリメート)によるアルファ線等の照射を行う。アルファ線を、各ストライプ電極3のX方向中央へ、Y方向に2mm間隔に、図4の×印で示す照射位置25に照射し、仮位置座標26を算出する。一つの照射点4で照射と算出を繰り返し、1点につき10分間ずつ測定した。
ステップST5では、X方向と同様に、Y方向の検出位置座標の算出を行い、必要に応じて、後述する2次曲線へのフィッティングをステップST6で行い、測定を終了する。その結果、上記図5に示すような、放射線16の仮位置座標26が得られた。
(1)X方向に並んだ仮位置座標群は、X方向には等間隔に分布している。
(2)X方向に並んだ仮位置座標(Xi,Yj)群におけるYjの位置は、Y方向に凹んでいる。
そこで、数式Yj=aXi 2+bXi+cとする2次曲線上にあるとし、上記係数a、b、cは、X方向に並んだ座標(Xi,Yj)群を基にそれらが2次曲線上にあるとしてフィッティングすることにより、最適な係数a、b、cが決定され、上記2次曲線が特定できる。
図7は、(3)式及び(4)式を用いて仮位置座標(Xi,Yj)より、検出位置座標(Xp,Yq)を導出した結果を示す図である。図4において×で示す照射位置に測定点が対応していることが分かる。
図7から明らかなように検出位置座標(Xp,Yq)において、X方向の間隔は1.2mm、Y方向の間隔は2mmであり、Y方向の位置分解能は、1mmが得られていることが分かる。
図8(A)から明らかなように、X方向の半値幅は、抵抗4,5の抵抗値が20kΩ以下では、約0.3mm以上となる。一方、X方向の半値幅は、抵抗4,5の抵抗値が20kΩ以上~100kΩでは、約0.3mm~0.25mmとなり、半値幅が低下することが分かる。これから、抵抗4,5の抵抗値が20kΩ以下では、X方向の半値幅が増大、つまり半導体2次元位置検出器1の空間分解能が劣化することが判明した。ストライプ電極3の抵抗値は上記したように1MΩである。この場合、ストライプ電極の抵抗値(1MΩ)と、ストライプ電極3の上端部同士間等に接続された抵抗4、5との抵抗(20kΩ)との比は、50:1となり、空間分解能が劣化しない。
本発明の第2の実施形態に係る半導体2次元位置検出器について以下説明する。
図9は、本発明の第2の実施形態に係る半導体2次元位置検出器30の構成を示す平面図であり、図10は、図9のVIII-VIII線に沿った断面図である。
第2実施形態の半導体2次元位置検出器30が、図3に示す第1実施形態の半導体2次元位置検出器1Aと異なるのは、各列のストライプ電極33の構造である。つまり、Y方向の溝2C及びX方向の溝2Dで分離された複数の後述するストリップ電極33ijが、Y方向にのみ抵抗35を介して接続されてストライプ電極33が構成されている。他の構成は、第1実施形態の半導体2次元位置検出器1,1Aと同じであるので説明は省略する。
ここで、j列目のストリップ電極33jk(kはm以下の自然数)同士がj列の抵抗rjで接続されて形成された電極を、ストライプ電極33jと呼ぶ。このj列目のストリップ電極33j同士がj列の抵抗rjで接続された状態を、ストライプ電極33jと呼ぶ。
この半導体2次元位置検出器30によれば、ストリップ電極33ijをマトリクス状とし、各列ストライプ電極33jを抵抗35で接続することによって、X方向及びY方向の放射線検出の位置分解能を、半導体2次元位置検出器1,1Aと同等、又はそれ以上に向上させることができる。
CdTe結晶からなる半導体基板2の白金電極15の面同士を電気伝導性を持つペーストで相互に貼り付ける。これを、非常に薄い絶縁薄膜と交互に幾重にも張り合わせることによって、ガンマ線の位置を3次元的に測定できる半導体検出器ブロックが形成される。
Claims (15)
- 半導体基板と、
上記半導体基板の表面にX方向に所定の間隔を置いて並置された、Y方向と平行な第1~第n(nは2以上の整数)のストライプ電極と、
上記第1~第nのストライプ電極の上端部同士間に接続される複数の抵抗と、
上記第1~第nのストライプ電極の下端部同士間に接続される複数の抵抗と、
上記第1のストライプ電極の下端部に抵抗を介して接続される第1の信号出力用端子と、
上記第nのストライプ電極の下端部に抵抗を介して接続される第2の信号出力用端子と、
上記第1のストライプ電極の上端部に抵抗を介して接続される第4の信号出力用端子と、
上記第nのストライプ電極の上端部に抵抗を介して接続される第3の信号出力用端子と、
上記半導体基板の裏面に配置された電極と、
を備え、
上記半導体基板の任意の点に入射した放射線からの出力信号を上記第1~第4の信号出力用端子から得ることを特徴とする、放射線の位置を2次元で検出するための半導体2次元位置検出器。 - 半導体基板と、
上記半導体基板の表面にX方向に所定の間隔を置いて並置された、Y方向と平行な第1~第n(nは2以上の整数)のストライプ電極と、
上記第1~第nのストライプ電極の上端部同士間に接続される複数の抵抗と、
上記第1~第nのストライプ電極の下端部同士間に接続される複数の抵抗と、
上記第1のストライプ電極の下端部に抵抗を介して接続される第1の信号出力用端子と、
上記第nのストライプ電極の下端部に抵抗を介して接続される第2の信号出力用端子と、
上記第1のストライプ電極の上端部に抵抗を介して接続される第4の信号出力用端子と、
上記第nのストライプ電極の上端部に抵抗を介して接続される第3の信号出力用端子と、
上記半導体基板の裏面に配置された電極と、
を備え、
上記第1~第nの各ストライプ電極は、Y方向に形成されかつ互いに分離されたm個のストリップ電極から形成され、
該各ストリップ電極は、Y方向に沿って隣り合うストリップ電極同士が抵抗を介して接続されて上記各ストライプ電極を形成し、
上記半導体基板の任意の点に入射した放射線からの出力信号を、上記第1~第4の信号出力用端子から得ることを特徴とする、放射線の位置を2次元で検出するための半導体2次元位置検出器。 - 前記ストライプ電極の上端部同士間及び下端部同士間に接続される抵抗は、その抵抗値が調整可能に形成されていることを特徴とする、請求項1又は2に記載の半導体2次元位置検出器。
- 前記各ストライプ電極の抵抗と前記ストライプ電極の上端部同士間及び/又は下端部同士間に接続された抵抗との抵抗比は、10:1~100:1であることを特徴とする、請求項1又は2に記載の半導体2次元位置検出器。
- 前記第1~第nの各ストライプ電極が、前記Y方向に沿って互いに溝分離されていることを特徴とする、請求項1又は2に記載の半導体2次元位置検出器。
- 前記第1~第nの各ストライプ電極を形成するストリップ電極同士が、前記X方向に沿って互いに溝分離されていることを特徴とする、請求項2に記載の半導体2次元位置検出器。
- 前記ストライプ電極は電気伝導抵抗性が高く且つショットキー型電極であり、前記半導体基板の裏面に配置された電極は電気伝導性の高い電極であることを特徴とする、請求項1又は2に記載の半導体2次元位置検出器。
- 前記半導体基板は、CdTe、CdZnTe及びBrTlの何れかからなり、前記電極は、インジウム又は白金からなることを特徴とする、請求項1又は2に記載の半導体2次元位置検出器。
- 前記出力信号から前記放射線の位置を演算する演算部を備え、
上記演算部は、第1~第4の信号出力用端子から出力される電圧を、それぞれV1,V2,V3,V4としたとき、下記(1)式及び(2)式によって、放射線の仮位置座標(Xi,Yj)を演算し、
上記仮位置座標(Xi,Yj)を用いて、下記(3)式及び(4)式によって前記放射線の検出位置座標(Xp,Yq)を算出することを特徴とする、請求項1~8の何れかに記載の半導体2次元位置検出器。
- 半導体基板の表面に、Y方向と平行であってX方向に所定の間隔で第1~第n(nは2以上の整数)のストライプ電極を並置し、
上記第1~第nのストライプ電極の上端部同士間のそれぞれを抵抗を介して接続し、
上記第1~第nのストライプ電極の下端部同士間のそれぞれを抵抗を介して接続し、
上記第1のストライプ電極の下端部に抵抗の一端を接続し、該抵抗の他端部に第1の信号出力用端子を配置し、
上記第nのストライプ電極の下端部に抵抗の一端を接続し、該抵抗の他端部に第2の信号出力用端子を配置し、
上記第1のストライプ電極の上端部に抵抗の一端を接続し、該抵抗の他端部に第4の信号出力用端子を配置し、
上記第nのストライプ電極の上端部に抵抗の一端を接続し、該抵抗の他端部に第3の信号出力用端子を配置し、
上記半導体基板の裏面に電極を配置し、
上記半導体基板に入射した放射線からの出力信号を、上記第1~第4の信号出力用端子から得ることを特徴とする、放射線の2次元位置検出方法。 - 上記第1~第nの各ストライプ電極を、Y方向に形成されかつ互いに分離されたm個のストリップ電極から形成し、該各ストリップ電極のY方向に沿って隣り合うストリップ電極同士を抵抗を介して接続して上記各ストライプ電極を形成することを特徴とする、請求項11に記載の放射線の2次元位置検出方法。
- 第1~第4の信号出力用端子から出力される電圧を、それぞれV1,V2,V3,V4としたとき、下記(1)式及び(2)式によって、放射線の仮位置座標(Xi,Yj)を演算し、
上記仮位置座標(Xi,Yj)を用いて、下記(3)式及び(4)式によって前記放射線の検出位置座標(Xp,Yq)を算出することを特徴とする、請求項11又は12に記載の放射線の2次元位置検出方法。
- 請求項1~10の何れかに記載の半導体2次元位置検出器を用いたことを特徴とする、陽電子断層撮影装置。
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