Image sensor, image sensor device, and computer tomography equipment

Abstract

An image sensor (100) includes a plurality of photodiodes (112a, 112b, 112h) and analog-to-digital converters (121a, 121b, 121h) arranged in adjacent first and second portions (110, 120) of a semiconductor substrate (101). The photodiodes exhibit X-ray radiation tolerance. Several image sensor devices in adjacent rows can be used as X-ray detectors in a computer tomography device.

Description

Technical Field

[0001] The present disclosure relates to an image sensor. Specifically, the present disclosure relates to an image sensor comprising a semiconductor substrate, a photodiode, an analog-to-digital converter and an electrical connection. The present disclosure also relates to an arrangement of several image sensors on a substrate and to a computer tomography device comprising an image sensor device. Background Art

[0002] Image sensors can be used in computed tomography (CT) equipment to record images of people, animals or objects in response to X-ray radiation. The image sensor is an important part of the performance of CT equipment and is also a major cost factor.

[0003] Conventional image sensors for CT applications may consist of two bonded semiconductor substrates with a photodiode in one of the substrates and an analog-to-digital converter (ADC) in the other substrate. The process requires pre-processing and bonding of the two semiconductor wafers, and forming through silicon vias (TSVs) to connect the photodiode at one side of the wafer sandwich to the ADC at the other side of the sandwich. Using two wafers and TSVs is a complex and costly process.

[0004] Another conventional image sensor for CT applications includes a photodiode and ADC close to each other on one side of a semiconductor substrate, where TSVs provide connections to external terminals on the other side of the substrate. This process is also quite expensive, and the area of ​​the ADC on the front side of the substrate reduces the resolution of the sensor.

[0005] Image sensors that avoid the above disadvantages are needed for use in CT applications. In particular, image sensors for low-end CT applications should have good image resolution while requiring less complex manufacturing processes to meet cost expectations.

[0006] One object of the present disclosure is to provide an image sensor that has high image resolution and can be manufactured using a standard CMOS manufacturing process.

[0007] Another object of the present disclosure is to provide an image sensor device for use in computed tomography applications.

[0008] It is a further object of the present disclosure to provide a computer tomography apparatus comprising such an image sensor device. Summary of the invention

[0009] An image sensor according to the present disclosure includes a semiconductor substrate having a first portion and a second portion. The semiconductor substrate may be an n-doped or p-doped silicon wafer used in a complementary metal oxide semiconductor (CMOS) manufacturing process.

[0010] A plurality of photodiodes configured to convert received electromagnetic radiation (such as visible light) into electrical signals are disposed in a first portion of a semiconductor substrate. Since the photodiode is used in an X-ray environment, the photodiode should exhibit X-ray radiation tolerance. Although the photodiode can be covered with a protective layer so that the X-ray radiation does not directly impinge on the photodiode, at least a small portion of the X-ray radiation may penetrate the protective mechanism, so that the photodiode should be X-ray radiation tolerant. The photodiode should have a structure in which the performance is not affected by the reception of X-ray radiation. Various possibilities for X-ray radiation tolerant arrangements of semiconductor layers are known to those skilled in the art. Specific X-ray radiation tolerant photodiode structures that can be used in the present disclosure are described below.

[0011] An analog-to-digital converter (ADC) is provided to convert the electrical analog signal generated by the photodiode into a digital signal to allow further digital processing. The ADC is arranged in the second portion of the semiconductor substrate. Each of the ADCs is associated with one of the photodiodes so that there is a one-to-one relationship between the photodiode and the ADC to ensure fast processing of the signal in the case of dead time. Almost all of the radiation is converted into image information so that the person being examined is not exposed to unnecessary excess radiation.

[0012] Electrical connections, such as connecting vias, are provided to connect each of the photodiodes to an associated one of the ADCs. The electrical connections may be buried in the semiconductor substrate to make more active surface available for the photodiodes. Alternatively, the electrical connections may be provided in one or more dielectric layers on the semiconductor substrate, which uses an acceptable amount of surface area and can be made with a standard, cost-effective CMOS manufacturing process.

[0013] According to one embodiment, an X-ray radiation tolerant photodiode includes a semiconductor substrate of a first conductivity type and a doped well region of a second conductivity type opposite to the first conductivity type disposed in the semiconductor substrate. The doped well faces the surface of the semiconductor substrate to receive radiation, such as ultraviolet radiation, human visible light, or infrared light. In one embodiment, the photodiode is configured to receive visible light and convert it into an analog electrical signal. A relatively shallowly doped surface region of the first conductivity type is disposed in the upper portion of the semiconductor substrate, and its doping concentration is higher than the doping concentration of the semiconductor substrate to achieve X-ray radiation tolerance. The doped surface region surrounds the doped well region. The doped surface region reduces the leakage charge generated by receiving higher energy radiation such as X-ray radiation. The doped surface region can be achieved by shallow implantation, which produces surface passivation for the spectral range of interest without adversely affecting the capacitance of the photodiode. The photodiode has high sensitivity and achieves a low dark current that is hardly increased after X-ray irradiation. In one embodiment, the first conductivity type can be generated by a p-dopant, and the second conductivity type can be generated by an n-dopant.

[0014] According to one embodiment, the doped well region can be surrounded by another doped well region of the first conductivity type, such as a p-doped conductivity type. The other doped well region can contact the doped well region and the doped surface region to ensure that the doped surface region, such as a p-type, has good contact with the doped well region, such as an n-type.

[0015] According to one embodiment, each of the photodiodes comprises a plurality of doped well regions which can be interconnected to one another by means of wires which are arranged in a dielectric layer on a substrate. Thus, one photodiode comprises a plurality of islands, for example of the n-well type, which contribute to the optically active region of the photodiode to generate a relatively high contact surface between the n-doped region and the p-doped region at the semiconductor surface. The arrangement of the layers for the photodiodes described above is described in more detail in European patent application publication EP 3 331 034A1, which is included herein by reference. X-ray radiation tolerant photodiode structures or X-ray radiation hard photodiode structures are also disclosed in other prior art references and can also be used to implement image sensors according to the present disclosure.

[0016] Compared to photodiodes designed for other application areas than computed tomography, the area of ​​the semiconductor substrate covered by the photodiode is relatively large. While camera applications can use photodiodes in the order of micrometers or less to achieve the highest possible pixel resolution, the area of ​​the photodiodes used for CT applications is in the order of millimeters. According to an embodiment, the area of ​​the semiconductor substrate that the photodiode can occupy is 0.5 mm×0.5 mm to 2.0 mm×2.0 mm. The actual range can be 1.0 mm×1.0 mm. It can be expected that the future development trend is to reach as low as 0.1 mm×0.1 mm and as high as 2.5 mm×2.5 mm. These ranges allow, on the one hand, to receive a sufficient amount of radiation to generate an electrical signal of an appropriate dynamic range, and enable the recorded image of the person, animal or object to be examined to have sufficient resolution.

[0017] According to one embodiment, the image sensor can be covered with a wavelength conversion layer, which converts the received X-ray radiation into electromagnetic radiation with a longer wavelength, such as ultraviolet light, visible light or infrared light. Specifically, the wavelength conversion layer converts the X-ray radiation into human visible light radiation that can be detected by the photodiode. The wavelength conversion layer can be a scintillator that converts X-rays into visible light. The wavelength conversion layer or scintillator can be continuously arranged on the surface of the image sensor that continuously covers the photodiode array. According to another embodiment, the wavelength conversion layer or scintillator can be individually arranged on each photodiode. Although the pixel-by-pixel scintillator layer exhibits good conversion quality, continuous layers can be manufactured more easily, however, crosstalk between photodiodes needs to be considered.

[0018] According to one embodiment, the analog-to-digital converter may also be covered by a wavelength conversion layer or a scintillator. Alternatively, an X-ray radiation shielding, such as a metal layer, for example a tungsten layer, provided on the ADC for X-ray protection may be used. Similar wavelength conversion layers or X-ray radiation shielding may also be provided on other electronic components provided in the second portion of the semiconductor substrate.

[0019] According to one embodiment, the semiconductor substrate may have a rectangular or square shape, wherein the rectangle or square has a first edge and a second edge disposed at opposite ends of the semiconductor substrate. The first portion and the second portion including the photodiode or including the ADC are continuous regions disposed adjacent to each other. The first portion includes one of the first edge and the second edge, and the second portion includes the other of the first edge and the second edge.

[0020] According to one embodiment, a parallel-to-serial interface including a parallel port and a serial port may be provided in the second portion of the substrate to convert a signal received from an ADC connected to the parallel port into a serial bit stream at the serial port. An output terminal at the serial port forwards the serial bit stream of image information to a circuit outside the image sensor. The serial bit stream may be supplied to an image processing algorithm running on a computing device in a CT device. In practice, an image sensor includes a serial output port that may be configured as a two-wire port providing a differential signal. The serial port may be configured as a low voltage differential signaling interface (LVDS), which is a standardized physical interface dedicated to serial high-speed data transmission.

[0021] According to one embodiment, with a more detailed view of the photodiode array, the photodiodes can be arranged in rows. A subset of the photodiodes can be arranged in corresponding rows, wherein one row is arranged adjacent to another row. The ADC associated with one of the photodiodes in the row is arranged opposite to the row, i.e., opposite to the photodiode forming the end of the row. It is beneficial to keep a certain distance between the photodiode at the end of the row next to the electronic circuit and the electronic circuit (such as ADC) that receives the signal from the photodiode. The distance should be sufficient to ensure thermal decoupling between the photodiode and the ADC to ensure that the heat generated by the digital operation of the ADC is not coupled into the photodiode. An appropriate distance is used between the photodiode at the end of a row and the ADC to ensure uniform sensitivity of the photodiode across the array. In addition, in the case where there is a gap between the scintillator and / or the X-ray radiation shield on the photodiode and the ADC, respectively, the distance between the photodiode and the ADC ensures that no X-ray radiation reaches the photodiode / ADC through the discontinuity of the material. The effective size of the distance is at least 100 μm. In practice, the distance can be 100 to 200 μm. Depending on the materials used to protect the photodiode and ADC from X-ray radiation, the effective distance can even be greater than 200 μm.

[0022] According to one embodiment, another closer view of the structure of the image sensor shows a matrix arrangement of multiple photodiodes including rows and columns. The analog-to-digital converter associated with one of the photodiodes in the row is arranged near the space of the corresponding row. This means that the analog-to-digital converter associated with one of the photodiodes in the row is arranged next to the corresponding row as described above. The row spacing of the photodiodes is related to the ADC spacing associated with the corresponding row of the photodiodes. When the semiconductor substrate has a rectangular shape, the photodiode is arranged near one of the edges of the rectangle and away from the other edge of the edge. The ADC is arranged near the other edge of the edge and away from one of the edges. It is beneficial to manufacture the electrical connections between the photodiodes and the associated ADCs in one or more dielectric layers on the semiconductor substrate so that the connecting line is located between two adjacent rows. The space required for the line is relatively small so that the loss of the optically active area appears to be tolerable.

[0023] According to one embodiment of the present disclosure, an arrangement of multiple image sensors includes image sensors disposed on a carrier substrate. The carrier substrate is a rigid substrate (such as a ceramic substrate) that includes lines for supplying power and receiving electrical signals, and dissipates heat generated from a single image sensor during operation. The image sensors are mounted on the carrier substrate in a first row and a second row, wherein each row includes one or more image sensors. The image sensors are oriented so that the first portions of the semiconductor substrates containing photodiodes of the first and second rows of image sensors are arranged adjacent to each other. Therefore, all first portions of the image sensors of the first row face the first portions of the image sensors of the second row. The photodiode arrays of adjacent image sensors are cascaded with each other to achieve a continuous expansion area of ​​the photodiodes. In one embodiment, the arrangement includes a plurality of 2×N image sensors arranged in two rows, each row including a number N of image sensors. When the photodiodes of a row include, for example, 8 photodiodes, the docking image sensors of the first and second rows form an array of 16 photodiode widths, i.e., the so-called 16-piece photodiodes disposed in the X-ray detector of a CT device. Current developments are directed to image sensors with rows of 16 or even 32 photodiodes, so that the width of the sensor device comprises 32 or 64 photodiodes or slices. The width of the image sensor device is sufficient to provide images of considerable size and resolution suitable for good CT representation of a person, animal or object at reasonable complexity and cost. Note that the ADCs are arranged in a second region of the semiconductor substrate of the docking image sensor at a distance from each other, wherein the photodiode array covers the region arranged between the ADCs.

[0024] According to one embodiment, a wavelength conversion layer may be disposed on a first portion of the image sensors in each of the first and second rows. In addition, a wavelength conversion layer or an X-ray radiation shield may be disposed on a second portion of the image sensors in the first and second rows to protect the electronics in the ADC from X-ray radiation.

[0025] According to one embodiment, bonding wires may be provided to connect pads on the semiconductor substrate to pads disposed on the carrier substrate. The pads provide power such as power supply potential VDD and ground potential VSS and receive differential electrical output signals containing image information recorded by the photodiode and converted to the digital domain by the ADC.

[0026] In order to dissipate the heat generated in the electronic circuits on the image sensor, such as the ADC, a heat sink or heat spreader is mounted to the carrier substrate to dissipate the heat generated in the electronic circuits and remove it from the photodiode array. The heat sink can be mounted adjacent to the second portion of the semiconductor substrate including the ADC. This arrangement allows the heat generated from the ADC to flow directly to the heat sink to remove the heat from the photodiodes, thereby achieving uniform sensitivity of the photodiode sensor device throughout the image sensor device. Note that the leakage current of the photodiode is highly dependent on temperature.

[0027] According to one embodiment, a computed tomography (CT) device includes an X-ray tube that can generate continuous X-ray radiation. An X-ray detector is arranged opposite to the X-ray tube so that radiation emitted by the X-ray tube is received in the X-ray detector. The X-ray detector includes a plurality of the above-mentioned image sensor devices arranged adjacent to each other. The X-ray detector can have the shape of a cylindrical surface. Depending on the available budget of the image sensor, the width of the X-ray detector can be 16 photodiodes / chips or multiples thereof. The X-ray tube and the X-ray detector can rotate around a space configured to accommodate an object or object to be inspected so that X-ray radiation passing through the object / object is recorded in the X-ray detector. A computer can be connected to the X-ray detector to receive image information from the sensor device, wherein software is installed on the computer to set it to calculate a two-dimensional or three-dimensional representation based on the received image information.

[0028] A CT device according to the present disclosure provides high resolution images at reasonable complexity and cost, wherein the X-ray detector comprises a plurality of image sensor devices consisting of a number of image sensors forming a continuous area of ​​photodiodes having a width of 16 photodiodes / chip or a multiple thereof.

[0029] It should be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operation of the various embodiments. The same elements in different figures of the drawings are denoted by the same reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the attached picture:

[0031] Figure 1 shows a top view of an image sensor;

[0032] Figure 2 shows a cross-sectional view of a portion of a photodiode;

[0033] Figure 3 another cross-sectional view of a portion of a photodiode is shown;

[0034] Figure 4 shows a top view of an arrangement of image sensors comprising several image sensors;

[0035] Figure 5 Shows Figure 4 a cross-sectional view of a portion of an image sensor device; and

[0036] Figure 6 Shown including according to Figure 4 The schematic diagram of the schematic diagram of the CT device shows several image sensor devices. DETAILED DESCRIPTION

[0037] Now, the present disclosure will be described more fully hereinafter with reference to the accompanying drawings showing embodiments of the present disclosure. However, the present disclosure can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will fully convey the scope of the present disclosure to those skilled in the art. The accompanying drawings are not necessarily drawn to scale, but are configured to clearly illustrate the present disclosure.

[0038] Figure 1A top view of an image sensor according to the present disclosure is depicted. The image sensor 100 is implemented as an integrated circuit of a semiconductor substrate 101. The semiconductor substrate has a rectangular or square shape. The semiconductor substrate rectangle includes four edges, where edges 102 and 103 are disposed on opposite ends of the semiconductor substrate 101. The substrate 101 includes two portions 110, 120, which include components of different functions. The portions 110, 120 are continuous, non-overlapping rectangular portions, where portion 110 includes edge 102 and portion 120 includes edge 103.

[0039] The first portion 110 of the semiconductor substrate 101 includes a photodiode array arranged in rows and columns. The photodiode array includes 8×8 photodiodes arranged in eight rows and eight columns. For example, rows 114 and 115 are arranged adjacent to each other, and each row includes a subset of 8 photodiodes, such as photodiodes 112a, 112b, 112h arranged in row 114. Figure 1 In FIG. 1 , the rows 114 , 115 extend in the vertical direction and the columns 116 extend in the horizontal direction. The arrangement of the photodiodes is a regular matrix, wherein the photodiodes are arranged at the intersections of the rows and columns.

[0040] The second part 120 includes analog-to-digital converters, wherein one ADC is associated with one of the photodiodes. The ADCs associated with the photodiodes of row 114 are arranged one after another in a region 121 opposite to the photodiode 112h forming the end of row 114. ADC 121a is associated with photodiode 112a, ADC 121b is associated with photodiode 112b, and ADC 121h is associated with photodiode 112h. The electrical signals generated by the photodiodes are supplied to the associated ADCs through lines, such as line 113a connecting photodiode 112a to ADC 121a and line 113b connecting photodiode 112b to ADC 121b. ADCs 121a, 121b, 121h are arranged so that they fit into the spacing defined by row 114. All other eight rows of image sensor 100 have corresponding structures.

[0041] The image sensor 100 is dedicated to computed tomography equipment so that it meets several requirements. The image sensor receives a continuous stream of radiation and has no dead time to avoid unnecessary radiation to the person to be examined. All photodiodes or pixels of the image are measured simultaneously. In addition to the lines connecting the photodiodes to the ADC, the photodiodes cover as much area of ​​the semiconductor chip as possible so that they provide as much image information as possible. The photodiodes are quite large in size compared to photodiodes in camera applications. In one embodiment, the vertical dimension 142 of the photodiode is about 1 mm (millimeter) and the horizontal dimension is about 1 mm. Depending on the process technology, the size can vary to at most about 2.5 mm×2.5 mm. With the advancement of process technology, it may be beneficial to reduce the size of the photodiode to about 0.1 mm×0.1 mm. In many embodiments, the size will be 0.5 mm×0.5 mm to 2.0 mm×2.0 mm.

[0042] The digital signals generated by the ADC in the second portion 120 of the substrate are connected to the parallel to serial interface 130 so that they can be output from the image sensor chip through the serial interface. In one embodiment, the serial interface port 132 can be a standardized low voltage differential signal interface (LVDS) that provides two differential signals Q1, Q2 at corresponding terminal pads 135, 136 of the semiconductor chip 101. The ADC is connected to the parallel interface port 131. The interface 130 performs multiplexing of the digital information provided in parallel from the ADC to the high-speed serial output 131, so that the amount of external wiring of the image sensor is reduced. The chip 101 also includes pads 133, 134 to provide power to the circuits on the chip 101, such as a positive power supply potential VDD and a ground potential VSS.

[0043] The image sensor 100 includes an array of 8×8 pixels and circuit elements such as an ADC and a parallel / serial interface, wherein these components can be manufactured from one side of the semiconductor substrate using a standard CMOS process. This avoids the necessity of making contacts through silicon (such as through silicon vias). While providing sufficient image information and resolution, it can be manufactured efficiently and at low cost to make it suitable for cost-effective computed tomography equipment. Depending on the process technology, larger photodiode arrays, such as 16×16 or 32×32 photodiodes, can be included on a single chip.

[0044] The photodiode array is arranged close to the edge 102 of the semiconductor substrate and away from the opposite edge 103 of the substrate. The ADC is arranged close to the edge 103 and away from the edge 102. This allows the substrate portion 101 to be subjected to radiation, wherein the ADC of the portion 120 can be protected from the radiation. Between the photodiode and the ADC, i.e., between the first portion 110 and the second portion 120 of the substrate, there is a sufficiently large gap or distance 190 so that good X-ray protection of the ADC can be provided without affecting the reception of radiation in the photodiode. On the other hand, the distance 190 should be such that the power consumption and the corresponding heat generated by the operation of the ADC are substantially decoupled from the photodiodes opposite to the ADC (such as the photodiodes 112h at the ends of the row 114). Since the temperature increase of the photodiode increases the leakage current of the photodiode, the thermal decoupling gap 190 ensures uniform characteristics of the photodiodes throughout the array. In practice, the gap 120 should be at least 100 μm. More practically, the gap 190 can be greater than 200 μm.

[0045] The photodiode array is covered with a photodiode that converts X-ray radiation into longer wavelength radiation such as visible light ( Figure 1 Scintillators are used to convert the X-ray radiation into ultraviolet or infrared light, depending on the receiving capability of the photodiode. The scintillator converts the X-ray radiation into light that can be evaluated by the photodiode. Although the largest part of the light will be converted into light that can be used by the photodiode, a small part of the X-ray radiation may pass through the scintillator layer, so that the photodiode must exhibit X-ray radiation tolerance.

[0046] The scintillator can be provided as one continuous layer on the photodiode array or as an intermittent layer covering the photodiode area with only gaps between the photodiodes. A single scintillator element on a photodiode provides a high level of optical isolation between adjacent photodiodes, so that optical crosstalk between adjacent photodiodes is virtually avoided.

[0047] Now go to Figure 2, showing a cross-sectional view through a portion of a photodiode. The substrate 201 consists of a bulk p-substrate 211 on which a p-epitaxial layer 212 is disposed. The epitaxial layer 212 includes a plurality of n-doped well regions 203. All regions are connected by a wiring layer 204 disposed in a dielectric layer 209 to form the cathode of the photodiode. The n-well region 203 includes a highly doped n+ region 213 to enable contact to the interconnect layer 204. For X-ray radiation tolerance, a p-doped surface layer 202 is provided between the n-well regions 203. The p-doped region 202 contacts the n-well region 203 and reduces leakage current that may be generated by receiving X-ray radiation. The p-surface doped region 203 can be implanted from the surface 210 into the epitaxial layer 212 of the semiconductor substrate 201. The p-doping concentration of the surface region 202 is higher than the p-doping concentration of the substrate layer 212. Additional lines 205 provide a plurality of contacts to the surface doped layer 202 to form a cathode terminal.

[0048] Figure 3 Another cross-sectional view of a portion of a photodiode with an improved layer structure is shown. Figure 3 An additional p-doped region 219 is included in a ring shape surrounding the n-well region 203. The p-doped regions 219 contact the surface doped regions 202 and the n-well region 203 so that they ensure good contact between the surface doped regions 202 and the n-well region 203 to avoid leakage current from X-ray radiation. Figure 2 and Figure 3 The diode structure depicted in the figure is important for forming Figure 1 Other X-ray radiation tolerant photodiode structures that will be apparent to a skilled person may also be beneficial.

[0049] Now go to Figure 4 ,according to Figure 1Several (e.g., 6) image sensors are arranged on a substrate 430 in a close spatial relationship. Specifically, all sensors 411, 412, 413, 421, 422, 423 are mounted on the substrate 430 in two adjacent rows 410, 420 extending in the horizontal direction. The direction of the photodiodes is such that two rows of photodiodes such as photodiodes 412, 422 are arranged adjacent to each other, wherein the photodiode arrays are arranged opposite to each other. Therefore, the edges 102 of the image sensors 412, 422 are adjacent to each other. In general, a number of N image sensors are arranged one after another in each row 410, 420, so that the arrangement on the substrate 430 includes 2×N image sensors. When the first portion 110 of each image sensor faces the first portion 110 of another image sensor, the second portion 120 including the ADC and the contact pads is away from each other and faces the opposite edges 431, 432 of the substrate 430. The arrangement of components adjacent to the image sensor 412, in which the image sensor is 3-side buttable, forms a continuous array of photodiodes with adjacent image sensors 411, 413 in the horizontal direction 452 and image sensor 422 in the vertical direction 451. In the vertical direction 451, many 16 photodiodes are arranged continuously, so that the X-ray detector of the CT device includes 16 pieces of photodiodes extending in the horizontal direction 452. Depending on the size of the image sensor, 32 or 64 pieces are also feasible.

[0050] The electrical contacts of the image sensor are provided in an outer region of the sensor near the edges 431, 432 of the carrier substrate 430. In particular, bonding wires 440 provide electrical connections between pad terminals 441 provided on each of the image sensor chips and pad terminals 442 provided on the substrate 430. The pad terminals supply power, such as operating voltages VDD, VSS, to the image sensor, and retrieve image signals in the form of differential serial signals Q1, Q2 from the image sensor.

[0051] The carrier substrate 430 can be a rigid substrate on which the image sensor is mounted with glue. The substrate can be made of a ceramic material and include one or more wiring layers to transmit electrical signals and power. In addition, the substrate 430 is used to dissipate heat to remove and dissipate the heat generated in the ADC of the image sensor through a suitable heat sink or radiator. This requires good thermal conductivity between the image sensor and the heat sink, and requires a close spatial relationship between the ADC of the image sensor and the heat sink. Preferably, the heat sink is mounted on the substrate 430 in close relation to the ADC of the image sensor. The heat sink can be mounted to the edges 431, 432 of the substrate 430. The glue material that mounts the image sensor to the substrate 430 should exhibit sufficient thermal conductivity.

[0052] Figure 5 Shown along line 460 through Figure 4 Cross section of the arrangement. Figure 5 A portion 510 of a ceramic carrier substrate on which a semiconductor chip 100 is mounted is shown. The portion of the semiconductor chip 100 shown includes three photodiodes 541, 542, 543 disposed in a first substrate portion 110. An ADC 561 is located next to the photodiode 543. A parallel-to-series interface 570 is located next to the ADC 561. The output of the interface 570 is connected to a bonding pad 530 disposed on the surface of the chip 100. Corresponding bonding pads 532 are disposed on the surface of the carrier substrate 510. Bonding wires 531 connect the pads 530 and 532. A heat sink 550 is mounted to a sidewall of the substrate 510, close to the ADC 561 and the interface 570, which may generate a large amount of heat. The close spatial relationship between the ADC 561 and the heat sink 550 allows heat to flow directly from the ADC 561 to the heat sink 550 so that heat is removed from the adjacent photodiode 543.

[0053] The wavelength conversion layer 520 is disposed on the first portion 110 of the chip 100, namely on the photodiodes 541, 542, 543. The wavelength conversion layer 520 may be a scintillator that converts X-ray radiation into visible light, which can be converted into an electrical signal by the photodiode. The scintillator layer 520 may extend (not shown) to the second portion 120 of the chip 100 including the ADC 561 and the interface 570. Figure 5 In another embodiment shown, the ADC 561 and the interface 570 are covered by an X-ray radiation shielding layer 521, which shields the ADC 561 and the interface 570 from any X-ray radiation. The shielding layer 521 extends over the entire surface of the second part 120 of the image sensor to cover the electronic circuits in the second part 120 of the chip 100. The X-ray radiation shielding 521 can be made of a material that is not penetrated by X-ray radiation, such as a metal layer, for example tungsten, so that it rejects any X-ray radiation. Other X-ray shielding metal materials may also be beneficial. The distance between the photodiodes 543 adjacent to the ADC 561 should be large enough so that no X-ray radiation can pass through the potential gap between the scintillator 520 and the X-ray radiation shielding 521 to avoid X-ray radiation hitting the active substrate area of ​​the semiconductor chip, such as the photodiode 543 or the ADC 561.

[0054] Figure 6 The schematic structure of a computer tomography device 600 including the above-mentioned image sensor and image sensor device is shown. An X-ray tube 610 continuously emits an X-ray radiation beam 611 having a defined aperture. The X-rays are received by an X-ray detector 620, which is composed of a combination of Figure 4 The sensor devices 622 are composed of a plurality of, for example, about 30, sensor devices 622 of the discussed principle. The arrangement of the X-ray tube 610 and the X-ray detector 620 rotates continuously around an interior space 630 configured to accommodate a person, animal or object to be examined. The X-ray detector 620 presents a receiving area with a barrel-shaped surface shape having a width 623 of 16 mm and a length 624 of about 1000 mm. Assuming that the square surface area of ​​the photodiodes or pixels of the actual detector 620 is 1 mm×1 mm, 16 photodiodes are arranged along the direction 620 and about 1000 photodiodes are arranged along the direction 624. Each of the sensor devices 622 includes a group of 2×4=8 image sensors mounted on a ceramic substrate 628. Also attached to the ceramic substrate 628 is an electronic circuit 629 provided on a printed circuit board that provides an interface and connection to a computer 640. Although the CT device shown includes 16 sheets of photodiodes arranged adjacent to each other along the direction 623 in the detector 620, a lower or higher number of sheets is also beneficial. Current manufacturing technology also allows the manufacture of image sensors of appropriate size, so that even 32 or 64 chips are possible.

[0055] According to the working principle of the CT device, while the arrangement of the X-ray tube 610 and the X-ray detector 620 is rotated around the individual or object in the space 630, the image information Q1, Q2 is continuously received. The individual or object in the space 630 moves along the direction 623, so that several rotational X-ray images are recorded. The computer 640 generates one or more 2D or 3D representations of the individual or object in the space 630 according to the image information Q1, Q2 according to the image processing algorithm known to those skilled in the art of CT technology.

[0056] The present disclosure describes an image sensor having one ADC per pixel, wherein the ADC is placed in close proximity to a photodiode array. The photodiode array itself contains an arrangement of photodiodes of, for example, 8×8 pixels, which allows simultaneous measurement of the photocurrent signals generated by the photodiodes. Dividing the semiconductor substrate chip into a photodiode portion and a portion including the ADC allows a 3-side dockable image sensor that can be mounted on the substrate using wire bonding techniques. The sensor itself can be manufactured using standard CMOS process technology.

[0057] The arrangement of several 3-side dockable image sensors in two rows enables the realization of, for example, 16 or more slices of X-ray detectors for CT equipment. Since X-ray detectors account for a major part of the cost of CT equipment and can be efficiently manufactured using standard CMOS processes, they are particularly beneficial for cost-sensitive CT applications.

[0058] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the present disclosure as defined in the appended claims. Since modifications, combinations, sub-combinations, and variations of the disclosed embodiments incorporating the spirit and substance of the present disclosure are conceivable to those skilled in the art, the present disclosure should be interpreted as including all within the scope of the appended claims.

Claims

1. An image sensor (100), comprising: - a semiconductor substrate (101) comprising a first portion (110) and a second portion (120); - a plurality of photodiodes (112a, 112b, 112h; 541, 542, 543), the plurality of photodiodes being arranged in the first portion (110) of the semiconductor substrate, the photodiodes having an X-ray radiation tolerant arrangement; - analog-to-digital converters (121a, 121b, 121h) arranged in the second portion (120) of the semiconductor substrate, each of the analog-to-digital converters being associated with a respective one of the plurality of photodiodes; and - electrical connections (113a, 113b), each of which is connected to one of the plurality of photodiodes (112a) and to an associated one of the analog-to-digital converters (121a), The photodiodes each include a semiconductor substrate (101, 211, 212) having a first conductivity type, a doped well region (203), and a doped surface region (202); the doped well region is arranged in the semiconductor substrate and has a second conductivity type opposite to the first conductivity type and faces a surface (210) of the semiconductor substrate; the doped surface region is arranged in the semiconductor substrate (212), has the first conductivity type and a doping concentration higher than the doping concentration of the semiconductor substrate (212), and surrounds the doped well region (203).

2. The image sensor (100) according to claim 1, wherein: The photodiodes each further include another doped well region (219) of the first conductivity type, the other doped well region surrounding the doped well region (203) and contacting the doped well region (203) and the doped surface region (202).

3. The image sensor (100) according to claim 1, wherein: The photodiodes each include a plurality of doped well regions (203, 213) of a second conductivity type interconnected (204) to one another.

4. The image sensor (100) according to claim 1, wherein: The photodiodes (112a, 112b, 112h) each occupy an area of ​​the semiconductor substrate (101) of 0.1mm×0.1mm to 2.5mm×2.5mm or 0.5mm×0.5mm to 2.0mm×2.0mm or 1.0mm×1.0mm.

5. The image sensor (100) according to claim 1, further comprising a wavelength conversion layer (520) disposed on the plurality of photodiodes (541, 542, 543) and one of a wavelength conversion layer and an X-ray radiation shield disposed on the analog-to-digital converter.

6. The image sensor (100) according to claim 1, wherein: The semiconductor substrate (101) has a rectangular or square shape and a first edge and a second edge (102, 103) arranged at opposite ends of the semiconductor substrate (101), wherein each of the first portion and the second portion (110, 120) is continuous and includes one of the first edge and the second edge (102; 103).

7. The image sensor (100) of claim 1, further comprising a parallel-to-serial interface (130) having a parallel port (131) and a serial port (132), wherein: The analog-to-digital converter (121a, 121b, 121h) is connected to a parallel port (131), and at least one serial output terminal (135, 136) is connected to the serial port (132).

8. The image sensor (100) according to claim 1, wherein: The subset of photodiodes is arranged in rows (114, 115), the rows being arranged adjacent to each other, wherein analog-to-digital converters (121a, 121b, 121h) associated with the photodiodes of one of the rows (114) are arranged opposite to the photodiodes (112h) forming the end of the row (114), wherein the distance (190) between the photodiodes (112h) forming the end of the row and the analog-to-digital converters (121a, 121b, 121h) associated with the photodiodes of the row is at least 100ym or at least 200ym.

9. The image sensor according to claim 1, wherein: The plurality of photodiodes (112a, 112b, 112h) are arranged in a matrix including rows (114, 115) and columns (116), and analog-to-digital converters (121a, 121b, 121h) associated with the photodiodes (112a, 112b, 112h) of one of the rows (114) are arranged near a space aligned with one of the rows (114), wherein the semiconductor substrate (101) has a rectangular shape having at least two parallel The edges (102, 103) are arranged, the photodiode is arranged near one of the edges (102) and away from the other edge (103) of the edges, and the analog-to-digital converter (121a, 121b, 121h) is arranged near the other edge (103) of the edges and away from one of the edges (102), wherein the electrical connection (113a, 113b) extends in the space between two adjacent rows (114, 115) of photodiodes.

10. The image sensor according to claim 1, wherein The semiconductor substrate includes a first portion (110) and a second portion (120), the first portion and the second portion not overlapping.

11. The image sensor according to claim 1, wherein: Each of the analog-to-digital converters (121a, 121b, 121h) is associated with one of the plurality of photodiodes in a one-to-one relationship.

12. The image sensor according to claim 10, wherein: The plurality of photodiodes (112a, 112b, 112h) are arranged in a matrix comprising rows (114, 115) and columns (116), the rows being arranged adjacent to each other, wherein an analog-to-digital converter (121a, 121b, 121h) associated with a photodiode of one of the rows (114) is arranged opposite to and aligned with a photodiode (112h) forming an end of the row (114), wherein a distance (190) between the analog-to-digital converter (121a, 121b, 121h) associated with the photodiode of the row and a photodiode (112h) forming an end of a row next to the analog-to-digital converter (121a, 121b, 121h) associated with the photodiode of the row is at least 100 μm or at least 200 μm; The semiconductor substrate (101) has a rectangular shape having at least two edges (102, 103) arranged in parallel, the photodiode is arranged in the first part, close to one of the edges (102) and away from the other of the edges (103), and the analog-to-digital converter (121a, 121b, 121h) is arranged in a second part that does not overlap with the first part, close to the other of the edges (103) and away from one of the edges (102); and Therein, the electrical connection (113a, 113b) extends in the space between two adjacent rows (114, 115) of photodiodes.

13. An image sensor device comprising: - a carrier substrate (430); -An image sensor according to claim 1, wherein the image sensors are mounted on the carrier substrate (430) in a first row and a second row (410, 420), wherein each of the first portions (110) of the semiconductor substrate of one or more image sensors (411, 412, 413) of the first row (410) is respectively arranged to be adjacent to a corresponding one of the first portions (110) of the semiconductor substrate of one or more image sensors (421, 422, 423) of the second row (420).

14. The image sensor device according to claim 13, wherein: A wavelength conversion layer (520) is disposed on a first portion (110) of the image sensor of each of the first and second rows (410, 420), and one of the wavelength conversion layer and the X-ray radiation shield (521) is disposed on a second portion (120) of the image sensor of the first and second rows (410, 420).

15. The image sensor device according to claim 14 further includes bonding wires (440, 531), which are connected to pad terminals (530) arranged on the semiconductor substrate of the image sensor and pad terminals (532) arranged on the carrier substrate to supply power (VDD, VSS) to the image sensor or output an electrical signal containing image information (Q1, Q2) received by the photodiode from the image sensor.

16. The image sensor device according to claim 13, Also included is at least one heat sink (550) mounted to the carrier substrate near the second portion (120) of the semiconductor substrate of the row (410, 420) of image sensors to allow heat generated from the analog-to-digital converter (121a) to flow directly to the at least one heat sink (550).

17. A computer tomography apparatus (600), comprising: - X-ray tube (610); an X-ray detector (620) arranged to receive radiation emitted by the X-ray tube (610), the X-ray detector (620) comprising a plurality of image sensor devices (622) according to claim 14 arranged adjacent to each other; - a space (630) for accommodating a subject or an object, wherein the X-ray tube (610) and the X-ray detector (620) are configured to rotate around the space (630); - a computer (640) connected to the X-ray detector (620) to receive image information (Q1, Q2) received by the sensor device (622) of the X-ray detector (620) and configured to calculate at least one two-dimensional or three-dimensional representation based on the received image information (Q1, Q2).

Images