Radiation detector module

Abstract

A radiation detector module (10) for position resolved radiation detection comprises at least one sensor sheet (1) extending in two dimensions (x, y) of a horizontal plane. The sensor sheet (1) comprises a sensor material sensitive to radiation and a set of electrically conductive pixels (12) in contact with the sensor material. The radiation detector module (10) further comprises at least one readout chip (2) arranged in parallel to the sensor sheet (1) for processing signals provided by the set of pixels (12). The readout chip (2) extends in at least one of the two dimensions less than the sensor sheet (1) extends in this dimension. The readout chip (2) comprises a set of input contacts (21) electrically connected to the pixels (12) and one or more output contacts (22) for providing processed signals. The readout chip (2) further comprises a substrate (4) arranged in parallel to the sensor sheet (1). The substrate (4) comprises a set of input contacts (41), input wiring (43) electrically connecting the input (41) contacts to the input contacts (21) of the readout chip (2), one or more output contacts (42) at a bottom surface thereof, and output wiring (44, 45) connecting the one or more output contacts (42) to the one or more output contacts (22) of the readout chip (2).

Description

Technical Field

[0001] This invention relates to a radiation detector module. Background Technology

[0002] In a computed tomography (CT) medical imaging system, an X-ray source emits a beam of radiation toward the patient. The transmitted beam is collected by an X-ray detector, which is typically arranged in an arc shape opposite the X-ray source. This arc is usually precisely assembled from small detector modules (e.g., 4 × 2 cm²). To avoid imaging artifacts and information loss during diagnostic examinations, it is desirable that the detector modules, assuming they are rectangular or square, be adjacent to each other on their four sides.

[0003] Hybrid pixel detectors (HPDs) consist of pixelated sensors connected pixel-by-pixel to a readout chip (ROC). The semiconductor sensors are typically made of one or more of Si, GaAs, CdTe, and CZT and generate charge pulses by absorbing ionizing radiation energy through the photoelectric effect or Compton interaction. The corresponding signal travels through the sensor pixels, which are interconnected with dedicated circuitry (also called ROC pixels) within the ROC, where the signal is analyzed and digitized. Traditionally, ROC pixels are connected to the readout board via wire bonding.

[0004] Hybrid pixel detectors are manufactured using a modular assembly approach. Multiple detector modules (each including a sensor, ROC pixels, and a readout board) are assembled together in a two-dimensional arrangement until the final detector size is achieved. Wire bonding connections result in dead detection areas, or gaps, between detector modules, especially between module sensors. The presence of gaps in the detector is incompatible with most imaging applications, particularly medical imaging. Summary of the Invention

[0005] Therefore, the overall objective of this invention is to provide a radiation detector module that allows multiple such modules to be arranged side-by-side without gaps between them.

[0006] Now, in order to achieve these and other objects of the present invention (which will become more apparent as the description proceeds), a radiation detector module is provided according to claim 1.

[0007] The radiation detector module includes at least one sensor chip, preferably made of a semiconductor material, preferably one or more of Si, GaAs, CdTe, and CZT, i.e., a sensor material that absorbs ionizing radiation energy through the photoelectric effect or Compton interaction. In computed tomography imaging applications, the sensor chip is preferably made of a high-Z material.

[0008] The sensor sheet is typically a flat sheet whose horizontal extension in both the x and y dimensions exceeds its extension in the third dimension z, orthogonal to the horizontal plane, i.e., its height. The sensor sheet includes a set of pixels of conductive material in contact with the sensor material. A pixel is defined as a surface region in the horizontal plane, preferably located on the bottom surface of the sensor sheet, and is typically made of metal. In another embodiment, a pixel may refer to a corresponding region defined by a conductive diffusion layer on or within the sensitive material of the sensor sheet, with metal contacts at the top. Here, the diffusion layer may, for example, be part of a PIN diode structure, which is formed internally, for example, through a silicon layer of the sensor sheet.

[0009] Any charge induced in a pixel, particularly that originating from converted photons or electrons, generates an electrical signal provided by the sensor pixel and contributes to the measurement. Therefore, the detector module allows for position-resolved detection. This means that the amount of radiation at each location in space can be detected, such as the number of photons, electrons, or deposited energy. The spatial resolution of the detector module, i.e., the number of pixels or measurements per unit area, depends on the pixel pitch. The pitch is preferably defined as the spatial period of the pixels in a uniform pixel matrix distribution. The pixel pitch corresponds to the measured distance between adjacent pixels, such as pixel center to pixel center.

[0010] Typically, the pixel pitch is uniform across the entire sensor sheet. Preferably, the pixels are rectangular, particularly square, with side lengths typically between 5 micrometers (µm) and 1000 micrometers, more preferably between 30 micrometers and 450 micrometers. This group of pixels can be arranged in a grid pattern, such as a rectangular grid, ideally covering a large portion of the sensitive material of the sensor sheet, for example, at least 90%, 95%, or 99%. Preferably, the number of sensor pixels in a group of sensor pixels on the sensor sheet is at least four. Preferably, the number of sensor pixels n on the sensor sheet is n², for example, n = 128 or n = 256.

[0011] The radiation detector module also includes at least one ROC, preferably in the form of an ASIC (Application-Specific Integrated Circuit). Each ROC includes input contacts, preferably arranged on the top surface of the ROC, and each input contact is internally connected to a designated readout circuit implemented in the ROC, which (preferably includes the corresponding input contact) is also referred to as an ROC pixel. Each sensor pixel is electrically connected to the designated ROC pixel in a 1:1 relationship via intermediate interconnects described below.

[0012] One or more ROCs are preferably configured to process electrical signals from sensor pixels. The processing may specifically include one or more of the following: amplifying the signal from the sensor pixels; comparing the amplified signal with a threshold and providing an electrical pulse for the duration during which the amplified signal exceeds the threshold; determining the amount of charge per pixel and per unit time; counting the number of incident photons or electrons that exceed a given signal threshold and are converted into charge per pixel and per unit time; and further processing such as calibration.

[0013] Preferably, one or more readout chips also have a horizontal extension and are arranged parallel to the sensor sheet. In one embodiment, a single ROC is assigned to a single sensor sheet to process signals from all sensor pixels. In a different embodiment, multiple ROCs are assigned to a single sensor sheet to process signals from all sensor pixels. In yet another embodiment, multiple ROCs are assigned to multiple sensor sheets to process signals from all sensor pixels across the multiple sensor sheets. In the case of multiple ROCs, these ROCs are arranged side-by-side with each other in a horizontal plane.

[0014] In a ROC, the spacing between input contacts is defined as similar to the pixel spacing of a sensor, relative to the input contacts of each readout circuit within the ROC. Typically, the spacing between input contacts is uniform across the entire ROC. The preferred spacing between two input contacts is between 20 micrometers and 500 micrometers.

[0015] Preferably, the spacing between ROC pixels is smaller than the spacing between sensor pixels. This is because additional space is needed next to one or more ROCs to provide output wiring.

[0016] The radiation detector module also includes a substrate, preferably a printed circuit board (PCB) or a molded interconnect device (MID), wherein the MID is preferably made of an epoxy compound or a glass substrate. The substrate is arranged parallel to the sensor sheet and preferably stacked with the sensor sheet along a third dimension, with the sensor sheet positioned above the substrate. The substrate includes a set of input contacts. The number of input contacts preferably corresponds to the cumulative number of input contacts of one or more ROCs. Therefore, wiring is provided in the substrate for electrically connecting its input contacts to the input contacts of one or more ROCs; this wiring is referred to as input wiring. Preferably, the substrate extends horizontally and includes a top surface and a bottom surface. Preferably, the input contacts are arranged on the top surface. In a preferred embodiment, the input contacts of the substrate are electrically connected to the sensor pixels in a 1:1 relationship via interconnect devices (e.g., including solder bumps, C4, copper pillars, solder-coated copper pillars, gold pillar bumps, anisotropic conductive adhesive, and any other suitable micro-interconnects). The spacing of the input contacts on the substrate is defined as similar to the spacing of the sensor pixels and the spacing of the ROC pixels. In one embodiment, the spacing of the input contacts of the substrate corresponds to the spacing of the sensor pixels, and in the assembled state of the sensor sheet and the substrate, the center of the input contacts of the substrate and the center of the sensor pixels match each other in the third dimension, that is, there is no lateral offset between the corresponding centers.

[0017] The substrate also includes one or more output contacts disposed on its bottom surface. Each ROC also provides one or more output contacts, preferably on its top surface, i.e., the same surface as its input contacts. In operation, the one or more output contacts provide processed input signals. Preferably, the number of output contacts of the ROC is less than the number of its input contacts, because there is no need to maintain a 1:1 relationship. For example, processed information, particularly counting information, can be provided through one or more output contacts, for example, in a multiplexed manner and / or in other digital manner. Furthermore, this can mean providing power supply voltage and ground voltage to the ASIC, or providing digital configuration data to the ASIC and the pixels.

[0018] Therefore, the substrate also includes wiring known as output wiring for connecting one or more of its output contacts to one or more output contacts of one or more ROCs.

[0019] This arrangement first connects the sensor pixels to the input contacts of the substrate, while only the input contacts of the substrate are connected in some way to the input contacts of the ROC. In prior art detectors, the sensor pixels are directly connected to the input contacts of the ROC. This means that the ROC is no longer arranged on top of the substrate directly facing the sensor pixels, but is preferably embedded in the substrate, or even arranged below the substrate, as will be explained below. This, in turn, allows for a redistribution layer in the substrate for connecting sensor pixels with different spacings to the ROC pixels.

[0020] In a highly preferred embodiment, one or more ROCs are embedded in a substrate. "Embedded" is understood to mean that at least the top and bottom surfaces of one or more ROCs are covered by an insulating substrate material. Therefore, each ROC is preferably cast into the substrate material. In one embodiment, all four end faces of each ROC (i.e., the sides between the top and bottom surfaces) are covered by the substrate material, i.e., not exposed, and thus mechanically protected by the surrounding substrate. In this embodiment, the ROC is completely cast into the substrate material, i.e., all its surfaces are covered by the substrate material. Specifically, the substrate material is an insulating material and is the same material covering all surfaces of the ROC. In this embodiment, the height of the substrate in the third dimension exceeds the height of the ROC. In different embodiments, at least one end face is not covered by the substrate material.

[0021] Preferably, each of the sensor sheet, ROC, and substrate is rectangular, particularly square. Preferably, the sensor sheet and substrate are stacked and have the same extension in a horizontal plane. The sensor sheet includes a top surface (e.g., including a top electrode) and a bottom surface (including a set of pixels). In the top region of the sensor sheet, incident radiation is converted into electrical charge. The sensor pixels on the bottom surface face the substrate and therefore also the input contacts of the substrate.

[0022] In one embodiment, a single ROC is embedded in the substrate. In another embodiment, at least two ROCs are embedded in the substrate. In a preferred embodiment, eight ROCs are embedded in the substrate, preferably arranged in two rows, i.e., 2. Four ROCs are used, specifically for computed tomography imaging applications. In cases with multiple ROCs, these ROCs are arranged side-by-side. Preferably, each module has only one substrate.

[0023] Given that the spacing of the input contacts of the ROC is smaller than the spacing of the sensor pixels, the extension of the ROC in the horizontal plane is preferably smaller than the extension of one or more sensor patches on the same plane, at least in one dimension, for example, x, and preferably in both x and y dimensions. When one or more ROCs are embedded in a substrate, the extension of the substrate exceeds the extension of that or each ROC in the horizontal plane, preferably in at least one dimension, x or y, and preferably in both dimensions, i.e., x and y. This allows sufficient space for output wiring to connect the output contacts of the readout chip to the output contacts of the substrate. The output wiring preferably has one or more vias extending in a third dimension and passing through the substrate, located next to the ROC.

[0024] A module comprising one or more ROCs embedded in a substrate represents a novel 3D packaging solution. With the module having a rectangular footprint, four-sided mating X-ray or electron detector modules can be fabricated. A module can be assembled with additional, preferably identical, modules to form a radiation detector. For ease of assembly, the substrate's extension in both the x and y dimensions is preferably equal to or less than the sensor sheet's extension in the same two dimensions. Thus, a stack is formed from the sensor sheet and the substrate. With the substrate having a rectangular or square base, the resulting module has a cuboid or cubic shape and can be arranged side-by-side on a common substrate. In other words, the ROC group and redistribution layer (RDL) circuitry in the substrate are shielded by the sensor sheet, resulting in a gapless module, and, by arranging multiple modules side-by-side, for example, in a grid pattern, a large-area gapless detector, such as a flat panel detector, is created.

[0025] Therefore, according to another aspect of the present invention, a radiation detector is provided, comprising a substrate and a radiation detector module according to any of the preceding claims disposed on the substrate.

[0026] The wiring in the substrate acts as a redistribution layer to adapt the spacing of the sensor pixels to the smaller spacing of the input contacts of the readout chip.

[0027] Output signals are routed from the ROC to the bottom surface of the substrate, preferably the bottom surface of the module, via vias arranged in the space next to or between the ROCs in the substrate. Specifically, the output wiring between the output contacts of the substrate and the output contacts of the ROC may include wiring arranged in one or more layers between the bottom surface of the substrate and the top surface of the ROC. In the case of a PCB, these layers may represent metal layers of a multi-layer PCB. Although referred to herein as output signals, contacts, and wiring, these terms should not be limited to signals leaving the module and the associated contacts and wiring. Similarly, these contacts and wiring can be used to route signals from external sources (e.g., power or control signals) to the ROC. Therefore, and as implemented in the detailed description in the accompanying drawings, output contacts are also referred to as I / O contacts.

[0028] The proposed concept is cost-effective because it can utilize scalable substrate technology. Therefore, manufacturing is simplified and subject to fewer environmental limitations.

[0029] Another advantage of this packaging is that it requires only one flip-chip step, which is when the sensor chip is attached to the substrate.

[0030] Another advantage is that this module allows the use of a single ASIC design across different products, such as sensors with different pixel pitches. In the CT market, sensor pixel pitch is typically specified by the customer.

[0031] In an embedded embodiment, preferably, a set of input contacts of the substrate is disposed on its top surface, and a set of input contacts and one or more output contacts of the readout chip are also disposed on its top surface, such that the input wiring is disposed in one or more layers between the top surface of the substrate and the top surface of the readout chip. If the substrate is a PCB, these layers may represent metal layers of a multilayer PCB. Therefore, the portion of the substrate covering the top surface of the ROC acts as a redistribution layer (RDL). Thus, the RDL is integrated into the substrate including the embedded ROC, adapting the ROC pixel pitch to the sensor pixel pitch. In other words, the input wiring connecting the input contacts of the substrate and the input contacts of the ROC includes via portions, i.e., portions extending vertically / along a third dimension in the substrate.

[0032] In the case of multiple sensor pixels and corresponding ROC pixels, and / or where the spacing of the ROC pixels is significantly smaller than the spacing of the sensor pixels, it is preferable to introduce another layer, namely a second redistribution layer, into the module. Therefore, the spacing matrix of the sensor pixels is transformed into the spacing matrix of the input contacts of the ROC through two different redistribution layers, one of which is the RDL integrated into the substrate as described above. In these embodiments, the spacing of the input contacts of the substrate is no longer matched to the spacing of the sensor pixels, but is smaller.

[0033] Another implementation can be in the form of an interposer layer arranged parallel to the sensor sheet, particularly between the sensor sheet and the substrate. The interposer layer is understood as an element extending horizontally across the extension of the sensor sheet. In cases where the module includes multiple sensor sheets, a single, continuous interposer layer is preferably provided, on which the sensor sheets are mounted. The interposer layer includes input contacts on its top surface, which faces the bottom surface of the sensor sheet. The spacing of the input contacts of the interposer layer matches the spacing of the sensor pixels. Therefore, it is preferred that the input contacts of the interposer layer are electrically connected to the sensor pixels in a 1:1 relationship via interconnecting devices (e.g., solder balls or any of the alternatives listed above). The interposer layer also includes a set of output contacts arranged on its bottom surface. The number of output contacts is preferably matched to the number of its input contacts, and thus also to the number of sensor pixels. The spacing of the output contacts of the interposer layer is preferably smaller than the spacing of the input contacts, and therefore also smaller than the spacing of the sensor pixels. Wiring, including vertical portions, is provided within the interposer layer for electrically connecting each input contact to its corresponding output contact.

[0034] The spacing of the output contacts of the interposer is preferably equal to the spacing of the input contacts of the substrate, but greater than the spacing of the input contacts of the readout chip. The output contacts of the interposer are electrically connected to the input contacts of the substrate in a 1:1 ratio via interconnection devices, and are connected to the input contacts of the ROC via the input wiring of the substrate.

[0035] In another embodiment of the second redistribution layer, another redistribution layer is implemented within the sensor sheet. The sensor sheet preferably includes a monolithic integrated wiring layer covering a set of pixels. This wiring layer includes a set of output contacts on its bottom surface facing the substrate, and wiring electrically connecting its output contacts to the sensor pixels. The spacing between the output contacts of the wiring layer is preferably smaller than the spacing between the sensor pixels, such that the wiring layer acts as another redistribution layer. The spacing between the output contacts of the wiring layer is preferably equal to the spacing between the input contacts of the substrate, such that the output contacts of the wiring layer are electrically connected to the input contacts of the substrate via interconnection means (e.g., solder balls or any of the other alternatives listed above).

[0036] In another embodiment, including readout chips embedded in a substrate, the radiation detector module comprises a single substrate, m sensor chips (m>1), and n readout chips (n>1) embedded in the substrate. The following combination is preferred:

[0037] - m=2 and n=2 - m=2 and n=4 - m=2 and n=8 - m=4 and n=4 - m=4 and n=8 - m=4 and n=16.

[0038] Preferably, each readout chip is electrically connected to only one assigned sensor chip. The spacing between the input contacts of each readout chip is smaller than the spacing between the sensor pixels of its assigned sensor chip. Preferably, the output wiring in the substrate includes one or more vias that extend in a third dimension and through the substrate, located adjacent to the readout chip. In one embodiment, vias belonging to the output wiring of two adjacent readout chips extend between the adjacent readout chips.

[0039] According to another embodiment of the invention, the ROC is not at least completely embedded in the substrate, which acts as an interposer and is disposed between one or more sensor chips on one side and one or more readout chips on the other side. Thus, the substrate is sandwiched between the sensor chips and the readout chips. In this arrangement, preferably, the readout chips are bonded to the bottom surface of the substrate, for example, via interconnects such as solder balls or alternatives listed above. In one embodiment, an underfill may be applied between the substrate and the ROC. Underfill compounds are widely used in packaging because they provide mechanical stability, mitigate the effects of mechanical stress, and prevent moisture. Preferably, after the two components are electrically interconnected, the underfill fluid is dispensed between the substrate and the ROC and then cured.

[0040] Preferably, the pitch of the input contacts of the substrate matches the pitch of the sensor pixels, such that an interconnection means, such as a solder ball or any of the alternatives listed above, provides a vertical electrical connection. The substrate now provides additional output contacts on its bottom surface, the pitch of which is smaller than the pitch of its input contacts. The pitch of the additional output contacts matches the pitch of the input contacts of the readout circuit. Accordingly, the wiring in the substrate represents redistribution wiring. The output contacts of the readout chip are routed through the substrate on its bottom surface to the output contacts of the substrate. The output contacts of the substrate are preferably connected to the outside world by means of solder balls with a sufficiently large diameter (for example 50 micrometers < d < 500 micrometers), or copper pillars, or any other suitable micro-interconnection technology with a corresponding height / vertical extension, so as to extend beyond the ROC arrangement below the substrate in the vertical direction.

[0041] All embodiments that include a redistribution layer for connecting the sensor pixels to the ROC pixels of different pitch sizes inherently have wires of different lengths in the redistribution layer, accompanied by respective wiring capacitances. In addition, the high interconnection wiring density of such a redistribution layer may lead to the accumulation of parasitic capacitance between adjacent RDL wires. Therefore, the fan-out RDL may lead to the accumulation of input capacitance at each ROC pixel of the readout chip. Preferably, each ROC pixel comprises an amplifier stage for pre-amplification purposes. The capacitance accumulated at the input end of each ROC pixel may affect the signal transmitted by the wire, thereby affecting the pulse length at the output end of the corresponding amplifier stage. Furthermore, the distribution of accumulated capacitance over the ROC pixel matrix may be non-uniform, thereby exerting different influences on the analog amplification performance of each ROC pixel.

[0042] Therefore, the amplifier stage output of each ROC pixel may be affected by the fan-out RDL accumulated capacitance (Ci), which represents at least the capacitance from the input wiring between the input contacts of the substrate and the input contacts of the ROC, and usually leads to a longer signal pulse shape. During operation at high X-ray or electron flux, the pulse signal count rate may increase, and lead to an increased probability of pulse overlap events (also referred to as pile-up events). In a pulse overlap event, a subsequent pulse rises before the previous pulse has fully fallen to a given level. This may lead to photon or electron counting losses. Considering the RDL in this embodiment of the radiation detector module, the longer pulse signals that may occur increase the risk of pile-up events, even at lower fluxes.

[0043] In a preferred embodiment for solving the problem of capacitance variation, the input contacts of the readout chip are arranged in groups, wherein the pitch between the input contacts within a group is smaller than the distance between the input contacts of adjacent groups. Such a group may comprise 2×2, 3×3, 4×4, 5×5 or g×h input contacts, where g>1 and h>1. Preferably, the input contacts within the group are arranged in a grid pattern. Thus, for example, the wiring length in the redistribution layer of the substrate is reduced on average.

[0044] Sensor pixels can be arranged in a grid pattern with a consistent spacing on the sensor sheet.

[0045] In different embodiments, sensor pixels may also be arranged in groups. This is done to reduce the impact of scattered radiation (e.g., Compton or milder Rayleigh) on image quality during CT scans. Therefore, the gaps between groups of sensor pixels are used for a grid, also known as an anti-scattering grid (ASG). The grid consists of a striped pattern of absorbing material. The anti-scattering grid is preferably placed on top of the sensor sheet, i.e., between the sensor sheet and the X-ray source. Therefore, the layout of the sensor pixels is preferably designed to match the ASG. The grid selectively absorbs scattered radiation and allows primary X-rays to reach the detector.

[0046] Therefore, in this embodiment, the spacing between sensor pixels within a group is preferably smaller than the distance between sensor pixels in adjacent groups. Such groups may include 2×2, 3×3, 4×4, 5×5, or g×h input contacts, where g>1 and h>1. Preferably, the group size and layout of the sensor pixels match the group size and layout of the ROC input contacts. Preferably, each group of sensor pixels is assigned to the corresponding group of input contacts on the substrate and the readout chip, such that the pixels in that group are connected only to the input contacts of the corresponding group.

[0047] In other embodiments of the invention, the capacitance change caused by the input wiring is handled individually for each ROC pixel. For example, the parameter may take different values ​​for each ROC pixel, for example, depending on the wiring length of the redistribution layer.

[0048] Preferably, each readout circuit is electrically connected to an assigned input contact and configured to process signals received from the assigned sensor pixel through that input contact. Each readout circuit preferably includes a comparator (also called a discriminator) configured to compare the received signal with a threshold and output a pulse for the duration during which the signal exceeds the threshold. Preferably, each readout circuit includes a pulse evaluation unit (also called a re-trigger unit) configured to evaluate the pulses received from the comparator and generate x pulses of a defined length and / or count x events for each received pulse, wherein if the length Δtp of the received pulse is less than the defined length Δtd, then x = 1; otherwise, x = an integer function of Δtp / Δtd. The defined length Δtd is also called the re-trigger time because a new counting pulse is triggered each time the pulse length Δtp exceeds the defined length Δtd.

[0049] Furthermore, each readout circuit preferably includes an amplifier stage configured to amplify the signal received at the corresponding input contact. The output of the amplifier stage is electrically connected to the input of a comparator for comparing the amplified signal with a threshold, preferably generated by a threshold generator. The output of the comparator is preferably electrically connected to the input of the pulse evaluation unit.

[0050] To handle varying input capacitance via signal circuitry, in one embodiment, at least two different thresholds are applied in the ROC, meaning at least two ROC pixels implement different thresholds. In another embodiment, it is recommended to apply at least two different re-trigger times in different readout circuits, meaning at least two ROC pixels implement different re-trigger times. Different thresholds and different re-trigger times can also be combined. The thresholds and / or re-trigger times can be set or adjusted individually for each readout circuit. Each of the thresholds and re-trigger times can be selected / adjusted within a defined range.

[0051] In one embodiment, the threshold and / or re-trigger time settings preferably depend on the input capacitance primarily derived from the input wiring. Preferably, the higher the parasitic / input capacitance of the assigned ROC pixel, the lower the threshold is set and / or the longer the re-trigger time is set. Conversely, the lower the parasitic / input capacitance, the higher the threshold is set and / or the shorter the re-trigger time is set. In other words: the threshold set in a low-capacitance scenario exceeds the threshold set in a high-capacitance scenario. The re-trigger time set in a high-capacitance scenario exceeds the threshold set in a low-capacitance scenario. In another embodiment, the threshold and / or re-trigger time of each ROC pixel are evaluated during calibration. In the first step of the calibration process, a pulse of known charge is injected into the sensor, for example, by exposing the sensor to X-rays of known energy. The X-rays may originate from a fluorescent sample with a known emission line, such as by excited K-lines or L-lines. An S-curve is recorded by scanning the threshold voltage. Its inflection point corresponds to the amount of charge injected. This operation is repeated for different amounts of injected charge (e.g., different fluorescent samples). In the second step, the threshold is fixed at 10%, 40%, 50% up to 90% of the injected charge, and the re-trigger time is scanned. The resulting count-to-re-trigger time curves have similar S-curve shapes, with different plateaus corresponding to counts 1, 2, 3, 4, etc., and multiple inflection points in between. The inflection point of the shortest re-trigger time then corresponds to the average signal length for a given threshold. Therefore, the pulse length for different thresholds can be determined without knowing the precise individual input capacitance. In another embodiment, the second part of the above calibration algorithm is applied to a known charge distribution, for example, by exposing the sensor to X-rays from a source with a broad X-ray spectrum. This spectrum can be generated by an X-ray tube, and the calibration can be applied to different tube high-voltage settings, such as 10 kVp, 40 kVp, 80 kVp, 120 kVp, 160 kVp up to 500 kVp.

[0052] Therefore, for variable retrievable times, consistent response of ROC pixels can be achieved even at high throughput by adjusting the retrievable time for each pixel. Longer overlapping pulse signals from ROC pixels connected to long RDL paths are preferably not processed using the same retrievable time as pulse signals from short RDL paths. It is preferable to adjust (tune) the retrievable time for each individual pixel to obtain accurate count rate correction.

[0053] In a more general embodiment of the invention, a radiation detection module is provided that integrates redistributed wiring between sensor pixels with different spacing and input contacts of a readout chip into one or more substrates, interposers, or wiring layers integrated in a sensor chip.

[0054] Redistributed wiring can create different capacitances between the wires of different pixels, which can affect the effective gain and may vary from pixel to pixel. Preferably, means is provided for compensating for signal variations at the input contacts of the readout chip caused by the capacitance from the redistributed wiring between the input contacts and the sensor pixels.

[0055] These devices preferably enable all pixels in the detector module to provide a consistent response in terms of energy resolution response, count rate response, and gain response.

[0056] In one embodiment, the compensation device includes circuitry that uses a re-trigger unit in the readout circuitry of each pixel, thereby achieving, among other advantages, a higher maximum event detection rate than when no such re-trigger unit is used. Furthermore, to compensate for further differences in the count rate profiles between pixels, the re-trigger time of such re-trigger units can be adjusted or tuned individually for each pixel. Additionally or alternatively, the threshold in the comparator of the readout circuitry can be adjusted or tuned individually for each pixel.

[0057] In manufacturing a substrate into which one or more readout chips are embedded, the ROC is preferably embedded in the substrate during the substrate manufacturing process. Contact vias are then fabricated on the top (RDL-TS = top surface of the redistribution layer = input wiring) and bottom (RDL-BS = bottom surface of the redistribution layer = output wiring) of the substrate. The former connects the embedded input contacts of the readout chips to the top surface of the substrate. The contact matrix spacing of the resulting substrate input contacts matches the contact matrix spacing of the sensor sheet. In this concept, the ROC does not require TSVs (Through Silicon Vias), and signals from the output contacts of the readout chips are routed to the back side of the substrate via metal vias (e.g., Cu in the substrate industry) fabricated in the embedded substrate (RDL-BS). To allocate space for such vias in the module, the x and / or y dimensions of the one or more readout chips allocated to the sensor sheet are preferably smaller than the size of the sensor sheet. The ROC pixels are fanned out to match the size of the sensor pixel matrix.

[0058] The substrate-ROC arrangement is then bonded to the pixelated sensor chip (i.e., a sensor chip with pixels on its bottom surface). Bonding is preferably performed, for example, by screen printing low-temperature solder paste onto the substrate or by using column bump bonding, or by using anisotropic conductive adhesive, followed by flip-chip and reflow / curing process steps.

[0059] Preferably, the radiation detector module is used in a computed tomography (CT) system. Attached Figure Description

[0060] The invention will be more thoroughly understood from the following detailed description, and other objectives besides those described above will become clearer. This description refers to the accompanying drawings, in which: Figure 1 It is a pixelated sensor chip (left) and a readout chip (right) including an input contact array, based on the existing technology of a radiation detector module. Figure 2 It is based on Figure 1 A cross-sectional view of a radiation detector module with pixelated sensors and pixelated readout chips; Figure 3 It is by Figure 2 A cross-sectional view of a radiation detector composed of radiation detector modules. Figure 4 This is a cross-sectional view of a radiation detector module according to an embodiment of the present invention; Figure 5 This is a perspective view of a radiation detector including a radiation detector module during the assembly process according to an embodiment of the present invention; Figure 6 This is a cross-sectional view of a radiation detector module according to an embodiment of the present invention; Figure 7 This is a cross-sectional view of two adjacent radiation detector modules according to an embodiment of the present invention. Figure 8 This is a cross-sectional view of two adjacent radiation detector modules according to another embodiment of the present invention; Figure 9 This is a cross-sectional view of a radiation detector module according to another embodiment of the present invention; Figure 10 This is a diagram of the signals at each stage in the readout circuit of a readout chip according to an embodiment of the present invention; Figure 11 This is a block diagram of a readout circuit included in a readout chip according to an embodiment of the present invention; Figure 12 This is a different view of a radiation detector module according to another embodiment of the present invention; Figure 13 This is a diagram of the signals at each stage in the readout circuit of a readout chip according to an embodiment of the present invention; Figure 14 This is a diagram of the signals at each stage in the readout circuit of the readout chip according to another embodiment of the present invention; Figure 15 This is a different view of a radiation detector module according to another embodiment of the present invention. Detailed Implementation

[0061] To better understand the problem and the solution according to the present invention, firstly, by means of... Figures 1 to 3 Describe the characteristics of existing radiation detector modules.

[0062] Figure 1 A bottom view of a pixelated sensor chip 1 (left side) of a radiation detector module according to the prior art, comprising an array of pixels 12, and a top view of a readout chip 2 (right side), comprising an array of input contacts 21, are shown. The pixelated sensor chip 1 and the pixelated readout chip 2 define a radiation detector module, wherein one or more radiation detector modules constitute a radiation detector.

[0063] exist Figure 1 In the sensor chip 1, an array of pixels 12, such as 256×256 pixels, is in contact with a radiation-sensitive sensor material. The pixelated readout chip 2 (located in...) Figure 1 (On the right) It has the same number of input contacts 21 as the pixels 12 of the pixelated sensor chip 1, i.e., 256×256. In addition, the readout chip 2 includes I / O pads 22 for input / output of electrical signals and peripheral circuitry, such as control blocks and guard rings, which occupy a portion of the readout chip surface.

[0064] Typically, sensor pixels 12 and input contacts 21 of the readout chip 2 are electrically connected to each other in a one-to-one correspondence, meaning the number of input contacts 21 equals the number of sensor pixels 12. For simplicity, corresponding sensor pixels 12 and input contacts 21 are positioned adjacent to each other. In some prior art radiation detector modules, the sensor pixels 12 in the outermost row and outermost column of the pixel matrix may be larger than the conventional sensor pixels 12 within the pixel matrix—such as... Figure 1 As shown, the sensor pixel 12 is used to cover the area above the peripheral circuit of the readout chip 2, so that the area is also sensitive to radiation.

[0065] Figure 2 A cross-sectional view of the detector module is shown, in which... Figure 1 The sensor chip 1 and the readout chip 2 are attached to each other, with the sensor pixel 12 facing the input contact 21 of the readout chip 2. For example... Figure 2 As shown, sensor pixel 12 and corresponding input contact 21 are typically located directly above / below each other, where above and below are related to a third vertical dimension z, which is defined as the horizontal extensions of sensor chip 1 and readout chip 2 in the x and y dimensions perpendicular to each other. Electrical connections are typically established using solder balls, bump bonding, cylindrical bumps, anisotropic conductive adhesive, copper pillars, or any other microelectronic interconnect device 3.

[0066] Figure 2The radiation detector module is mounted on a high-density interconnect (HDI) printed circuit board 4 with readout electronics. In the prior art, the electrical connection between the I / O contacts 22 of the readout chip 2 and the HDI PCB 4 is established via wire bonding 7. Assuming the spacing between the pixels 12 of the sensor chip 1 and the input contacts 21 of the readout chip 2 is the same, the readout chip extends beyond the sensor chip at least in the x and y dimensions. Otherwise, the I / O contacts 22 would not be able to find a position on the top surface of the readout chip 2.

[0067] Multiple such as Figure 2 The radiation detector modules shown are arranged side by side to obtain a larger detector area, thus forming a shape like... Figure 3 The radiation detector shown. From Figure 3 It can be seen that arranging the existing detector modules side-by-side on PCB4 results in gaps g between sensor chips 1. Therefore, the existing radiation detector exhibits gaps g in the horizontal plane xy, where no sensor material is placed, meaning that radiation or photons cannot be detected in these gaps g. This leads to loss of detail in the generated image and loss of the measurement signal. Figure 3 In this configuration, each readout chip 2 is equipped with a sensor chip 1, and multiple readout chips 2 are located on a common PCB 4.

[0068] Figure 4 A cross-sectional view of a radiation detector module 10 according to an embodiment of the present invention is shown. The sensor chip 1 includes a sensor material capable of absorbing ionizing radiation energy (e.g., X-rays, electrons). The sensor material may be Si, GaAs, CdTe or CZT, InP, HgI2, perovskite compounds, LGAD, or any other semiconductor material known in the art. The incident radiation energy causes charge pulses to be generated in the sensor material through the photoelectric effect or Compton interaction.

[0069] A top electrode 11 is provided on the top surface of the sensor material. A plurality of pixels 12 in a grid structure are defined on the bottom surface of the sensor material. The spacing Δs between the sensor pixels 1 is preferably between 5 micrometers and 1 millimeter. The thickness of the sensor sheet 1 in the z-axis is preferably between 300 micrometers and 2 millimeters.

[0070] This radiation detector module includes a substrate, such as a printed circuit board (PCB) 4. At least one readout chip 2 is embedded in the PCB 4. The PCB includes a set of input contacts 41 arranged on its top surface and one or more output contacts 42 arranged on its bottom surface.

[0071] One or more readout chips 2 are preferably embedded in the dielectric material of PCB 4 and are compatible with microelectronics manufacturing processes. Embedding manufacturing methods are, for example, listed in "Printed circuit board embedded power semiconductors: A technology review" (Till Huesgen, Elsevier, *Power Electronic and Devices*, October 2022, Vol. 3). The readout chip 2 includes a set of input contacts 21 arranged on its top surface. Furthermore, the readout chip 2 also includes one or more output contacts 22, also arranged on its top surface.

[0072] The spacing Δc of the input contacts 41 of PCB4 matches the spacing Δs of the sensor pixels 12. Therefore, the input contacts 41 of PCB4 (e.g., in the form of contact pads on the top surface of PCB4) are vertically aligned with the sensor pixels 12, or in other words, their horizontal offset relative to the sensor pixels 12 is no greater than the sensor pixel spacing. In this embodiment, solder balls 3 are used as interconnects to electrically connect the sensor pixels 12 to the input contacts 41 of PCB4 in a 1:1 ratio. Alternatively, other types of interconnects can be used, such as C4, copper pillars, solder-coated copper pillars, gold pillar bumps, anisotropic conductive adhesive, or any other suitable micro-interconnects.

[0073] The spacing Δr between the input contacts 21 of the readout chip 2 (which may differ in the y and x directions) is smaller than the spacing Δs between the sensor pixels 12 and the spacing Δc between the input contacts of the PCB 4. The spacing Δr between the input contacts 21 of the readout chip 2 can be, for example, between 5 micrometers and 1 millimeter. Therefore, the portion of the PCB 4 between its input contacts 41 and the input contacts 21 of the embedded readout chip 2 serves as a redistribution layer, connecting the input contacts 21 on the top surface of the readout chip 2 to the input contacts 41 on the top surface of the PCB 4. The redistribution layer is implemented by input wiring 43, which preferably electrically connects the contact pads 21 and 41 in a 1:1 ratio, and includes a vertical portion in the z-direction.

[0074] PCB 4 is preferably processed to define the layout of the redistribution layer. The embedded input contacts 21 of the readout chip 2 are preferably made contact by means of, for example, mechanical drilling or laser drilling, or selective chemical etching. The input wiring 43 of the redistribution layer is preferably integrated by means of, for example, electroplating, chemical plating / sputtering, metal evaporation, or metal printing.

[0075] Therefore, PCB4 implements a fan-out redistribution layer that uniquely connects each input contact 21 and its corresponding readout circuit to the corresponding PCB input contact 41 on the top surface of the PCB, and to the corresponding sensor pixel 12 on the bottom surface of the sensor chip 1 via solder bumps 3. Input wiring 43 adapts the pixel pitch Δr of the readout chip 2 to the pixel pitch Δs of the sensor chip 1, wherein the pixel pitch Δs of the sensor chip 1 is greater than the pixel pitch Δr of the readout chip 2. Input wiring 43 may include multiple layers with metal traces and interlayer vias for connecting traces between two layers.

[0076] Therefore, sensor chip 1 extends beyond readout chip 2 in the x and / or y dimensions, preferably in both x and y dimensions, to create space in PCB 4 to allocate one or more vias 45 that route output signals from output contacts 22 of readout chip 2 to output contacts 42 of PCB 42 disposed on its bottom surface. Given that one or more output contacts 42 of PCB 4 are located on its bottom surface, while one or more output contacts of readout chip 2 are located on its top surface, output wiring 44, 45 is required to electrically connect these output contacts 22 and 42. Output wiring 44 may also represent a redistribution layer. It preferably includes at least one via extending vertically in the PCB, preferably located adjacent to readout chip 2.

[0077] Figure 4 In the radiation detector module, the sensor chip 1 and PCB 4 have the same extension in the x and y dimensions, or the sensor chip's extension is slightly greater than the PCB's extension. Multiple such modules can be assembled side-by-side to construct a gapless radiation detector, for example, by arranging rectangular or square modules side-by-side. However, the radiation detector module is not limited to a 1:1 relationship between the sensor chip, readout chip, and PCB. In one example, each module has more than one sensor chip, and in another embodiment, each module has more than one readout chip; for both embodiments, all components are located on or within a common PCB.

[0078] Figure 5 A perspective view illustrates the concept of a gapless radiation detector according to an embodiment of the present invention. A substrate 6 can be used as a mounting plate. The substrate 6 can be implemented as a printed circuit board, its top surface including one or more contact areas for contacting one or more output contacts 42 of a module PCB 4. Figure 5 In the example, a single radiation detector module is designated by reference numeral 10. Multiple modules 10 have been mounted on the substrate 6, with one module 10 being installed. From Figure 5It can be seen that each module PCB 4 of this radiation detector module 10 includes two sensor chips 1, and each sensor chip 1 includes four readout chips 2, that is, each PCB 4 includes eight readout chips 2.

[0079] Therefore, this radiation detector module implements a packaging concept that allows for the assembly of four side-joinable X-ray or EM detectors.

[0080] Figure 6 A cross-sectional view of a radiation detector module according to an embodiment of the present invention is shown. The module 10 shown may be... Figure 5 Module 10 is used in the components. Therefore, Figure 6 The module 10 shown includes a common PCB 4 for two sensor chips 1. Currently, each sensor chip 1 is assigned one readout chip 2; however, each sensor chip 1 can be assigned two, four, or even more readout chips 2. The readout chips 2 are embedded in the common PCB 4. Apart from this, the layout, wiring, etc., of module 10 are similar to... Figure 4 similar.

[0081] Figure 7 A cross-sectional view of two radiation detector modules 10 arranged adjacent to each other according to an embodiment of the present invention is shown. Each module 10 preferably has a dedicated PCB 4, a sensor chip 1, and a readout chip 2 integrated in the PCB 4. The extension of the PCB 4 in the horizontal dimensions x and y is smaller than the extension of the sensor chip 1. The spacing between the input contacts 21 of the readout chip 2 is even smaller than in other embodiments. Therefore, if according to Figure 4If implemented in the following embodiments, it may be difficult to lay out and manufacture the input wiring 43 in PCB 4. In particular, the line width and / or spacing of the wiring 43 may be too small for applicable processing techniques. Therefore, an additional redistribution device is provided in the form of an interposer layer 5. The interposer layer 5 includes input contacts 51 on its top side, preferably having the same spacing as the sensor pixels 12, such that each combination of sensor pixel 12 and input contact 51 can be electrically connected via solder bumps 3 or one of the other interconnects listed above. Output contacts 52 are disposed on the bottom surface of the interposer layer 5, having a smaller spacing than the input contacts 51. The output contacts 52 are connected to the input contacts 51 via wiring 53. However, the output contacts 52 of the interposer layer 5 still have a spacing equal to or greater than that of the input contacts 21 of the readout chip 2. However, the spacing of the output contacts 51 matches the spacing of the input contacts 41 of the PCB, allowing the output contacts 52 of the interposer layer 5 to be connected 1:1 to the input contacts 41 of the PCB 4 using interconnects such as solder bumps 3. Therefore, the interposer layer 5 includes wiring 53 used as a redistribution layer. With the PCB4 still providing input wiring 43 in the form of a redistribution layer, the redistribution from sensor pixel 12 to ROC pixel will be achieved in two steps, namely through the interposer layer 5 and the top layer of PCB 4.

[0082] Intermediate layer 5 is preferably made of silicon, glass or organic material.

[0083] Figure 8 A cross-sectional view is shown of two radiation detector modules 10 arranged adjacent to each other according to another embodiment of the present invention. Basic situation and... Figure 7 The same implementation applies, meaning that redistribution alone on PCB4 may not be feasible. Similarly, the pixel pitch difference between the input contact 21 of the readout chip 2 and the sensor pixel 12 of the sensor chip 1 is adapted by a combination of two fan-out redistribution layers. The first redistribution layer is integrated into PCB4, just like... Figure 4 and Figure 7 The implementation is the same. However, the other redistribution layer is not... Figure 7Instead of the intermediate layer 5, the wiring layer 13 is monolithically integrated into the sensor chip 1 and is preferably manufactured using microtechnology processes such as photolithography, PVD, spin coating or spraying of dielectric materials, and photoresist to isolate polymers and metals. The wiring layer 13 covers the sensor pixels 12. Output contacts 131 of the wiring layer 13 are arranged on its bottom surface and have a smaller pitch than the pixel pitch of the sensor chip 12. The output contacts 131 are connected to the sensor pixels 12 via wiring 132. However, the pitch of the output contacts 131 of the wiring layer 131 is still equal to or greater than the pitch of the input contacts 21 of the readout chip 2. However, the pitch of the output contacts 131 matches the pitch of the input contacts 41 of the PCB, so that interconnecting devices (e.g., solder bumps 3) can be used to connect the output contacts 131 of the wiring layer 13 to the input contacts 41 of the PCB 4 in a 1:1 manner.

[0084] Figure 9 A cross-sectional view of a radiation detector module 10 according to another embodiment of the present invention is shown. Module 10 includes two sensor chips 1, two readout chips 2, and a PCB 4. In this embodiment, the readout chips 2 are not embedded in the PCB 4. Instead, the PCB 4 acts as an intermediary layer sandwiched between the sensor chips 1 and the readout chips 2. The input contacts 41 of the PCB 4 are connected to the sensor pixels 12 via interconnects such as solder balls 3 and have the same spacing as the sensor pixels 12.

[0085] In addition, PCB 4 includes additional output contacts 46 on its bottom surface. The additional output contacts 46 have the same spacing as the input contacts 21 of the read chip 2 and are interconnected via interconnects such as solder balls 3. The output contacts 22 of the read chip 2 are also connected to contacts on the bottom surface of PCB 4 and are connected to the output contacts 42 on the bottom surface of PCB 4 via wiring 44 in the PCB or on the bottom surface of PCB 4. The output contacts 42 of the PCB are connected to the input contacts 71 of the read board 7 via interconnects such as solder balls 3, and the board 7 is connected to the outside world via one or more output contacts 72 on its bottom surface.

[0086] In this embodiment, PCB 4 can also be regarded as a redistribution layer and / or an interposer, and is preferably made of silicon, glass or organic materials.

[0087] Figure 10 The diagram shows the response of two different ROC pixels to an increasing electron or X-ray photon count rate, one on the left and the other on the right. The underlying circuitry of the ROC pixels is shown in... Figure 11 As shown in the image. Figure 11A block diagram of the ROC pixel 23, also known as the readout circuit 23, included in the readout chip 2, is shown, illustrating its core function. Charge generated in the sensor material of the sensor sheet drifts through the sensor sheet to one or more sensor pixels and reaches the input contacts 21 of the ROC pixel 23 of the readout chip 2 via interconnects and redistribution layers. The charge enters an amplifier stage 231, which converts the generated charge into voltage pulses. To achieve a high incident electron count rate, the amplifier stage 231 is preferably designed to generate very short pulses with an FWHM pulse duration between 5 ns and 500 ns, more preferably shorter than 40 ns, 20 ns, or 10 ns. Following the amplifier stage 231 is a fast discriminator, also known as a comparator 232, used to discriminate the voltage pulses. Pulses with voltages above a threshold are converted into digital pulses whose pulse length corresponds to the duration of the analog pulse voltage above the threshold voltage. Pulses that do not exceed the threshold cannot reach the output of the discriminator stage 232. Therefore, in the discriminator stage 232, the voltage pulse is compared with the threshold. Threshold generator 233 is used to provide a threshold. The threshold is preferably determined based on the global voltage applied to the readout chip 2, and preferably in combination with individual tuning for each pixel, as described later.

[0088] To prevent pulse buildup at high count rates from causing counting paralysis, a re-triggering unit, also known as pulse evaluation unit 234, is used. Pulse evaluation unit 234 is preferably user-disabled or enabled. The adjustable re-triggering length (i.e., the time period after a re-triggering event is initiated) is preferably matched to the average analog voltage pulse duration, where the analog voltage pulse duration is defined as the duration for which the analog pulse is above a threshold voltage. In a preferred embodiment, the re-triggering duration is set slightly longer than the analog pulse duration, for example, 2 nanoseconds, 5 nanoseconds, 10 nanoseconds, or 20 nanoseconds longer. Therefore, the instantaneous pulse evaluation unit 234 re-evaluates the pulse signal provided by the discrimination stage 232. After the predetermined re-triggering length, i.e., after each count, a subsequent counting unit 235 is triggered to increment the count in case of pulse buildup. In this linear counting unit 235 (also known as a counter), each pulse generated at the output of the re-triggering unit 234 increments the counter in the counting unit 235 by 1. Preferably, the counting unit 235 includes at least two counters that can switch between consecutive exposures and allow continuous (dead zone-free) reading, i.e., while one counter is being read, the other counter is in a counting active state.

[0089] Back Figure 10 : Figure 10The x-axis in the graph represents time. The y-axis of the topmost chart represents the amplitude of the (analog) input signal acquired from the corresponding input contact 21, which is amplified by amplifier stage 231 and then shaped by a shaper after amplifier stage 231. Figure 11 Shaping (not shown in the diagram). The second diagram above shows the corresponding output of comparator 232, which compares the amplified input signal with a threshold, and provides a pulse-shaping signal. The duration of the pulse in the pulse-shaping signal represents the time period during which the amplified input signal exceeds the specified threshold. The pulse-shaping signal is then preferably fed to the shortening unit (…). Figure 11 (not shown in the image) to shorten the pulses in the pulse shaping signal to a predetermined consistent duration. Preferably, according to... Figure 10 (b) The pulse-shaped paralysis signal is also fed to the re-trigger unit 234 of the corresponding ROC pixel 23. The re-trigger unit 234 detects whether the pulse length from the discriminator stage 232 exceeds a predefined re-trigger length. The re-trigger length can represent the duration for which the amplified signal of a typical single event in a low-throughput detection scenario exceeds a specified threshold. If the re-trigger length is exceeded, the re-trigger unit 235 generates another shortened pulse. The counter 236 counts the shortened pulses (including the re-trigger pulse) from the shortening circuit to provide a non-stacking count.

[0090] exist Figure 10 The output of each unit of the first ROC pixel is shown in the left-hand scene / ROC pixel. It is assumed that there is a minimum RDL connection between this particular ROC pixel and the corresponding sensor pixel, for example, a purely vertical RDL connection between the ROC pixel represented by input contact 21 and the corresponding input contact 41 of PCB 4, such as... Figure 10 (a) As shown in the upper left of the box. Therefore, in this scenario, the input wiring 43 should be as short as possible. According to Figure (a), in response to a radiation event at the location corresponding to the ROC pixel in the sensor chip, a narrow signal pulse can be observed at the output of the amplifier stage. The ROC pixel is able to handle pulses generated by low-throughput input (1), and even pulses generated by high electron and X-ray excitation rates in response to high-throughput input (2), however, until a limit (3) is reached where signal buildup prevents the counting of individual photons in paralysis mode. In this event, the amplified input signal in response to the first impact has not yet fallen below the threshold ETh (dashed line) before the amplified input in response to subsequent impacts exceeds the threshold again. Therefore, without any adjustment means, scenario (3) results in a single long pulse at the output of comparator 232 instead of three pulses that can be distinguished from each other. The output of the shortening unit provides a corresponding shortened pulse, see Figure 10 The diagram in (c) shows that the information about the three pulses hitting the sensor pixel at (3) is lost at the output of the shortening unit.

[0091] However, preferably, with Figure 11 Re-evaluation of the re-trigger function in the form of re-trigger unit 235 Figure 10 (b) describes the duration / length of the pulse amplification input signal and effectively counts the incident photons; see [reference needed]. Figure 10 (d) Output of the re-trigger unit 235.

[0092] for Figure 10 The different ROC pixels shown on the right, the sensor pixels, and the corresponding ROC pixels are connected by more complex RDL wires, for example, longer wires than those in the ROC pixel scene on the left. These longer wires are more prone to accumulating self-capacitance and parasitic capacitance. For example, the input wiring 43 of PCB 4 for the ROC pixel on the right exceeds the input wiring 43 of the ROC pixel on the left. In this example, the relevant 43 should now include the wiring between the input contact 21 of the ROC pixel and the corresponding input contact 41 of PCB 4. Therefore, the output of the amplifier stage is a longer signal (4), and the accumulation effect occurs at lower electron and X-ray excitation rates, see (5) and (6). In this particular case, the performance of the detector module would be greatly affected at moderate X-ray and electron fluxes without implementing instantaneous re-trigger functionality. Therefore, the pulse width of the signal in each individual pixel depends on the precise geometry of the RDL connection, capacitance, etc.

[0093] Therefore, in one embodiment, a re-trigger unit 235 and its corresponding re-trigger function are preferably provided and applied, which monitors the pulse duration / length of the output pulse from the discriminator unit 232, and restarts (re-triggers) the counting, in particular, when a defined re-trigger time (which indicates a stacking event) is exceeded after each count. The re-trigger function allows for non-paralyzing counting and allows for enhanced count rate correction.

[0094] In different embodiments, ROC pixels and potentially sensor pixels can be arranged using a simplified redistribution layer (RDL) design. In this embodiment, the input contacts of the readout chip are not equidistant from each other across the entire top surface of the readout chip. Instead, they are formed into subgroups, also known as submatrices or macropixels, thereby providing uniform pixel spacing between input contacts belonging to the same subgroup. However, the distance between (adjacent) input contacts in different subgroups differs from the spacing between input contacts within the same subgroup. This results in a shorter overall length of wires in the RDL and reduces the complexity of wiring in the RDL. Consequently, self-capacitance and parasitic coupling with adjacent ROC pixels are reduced. The space between pixel submatrices in the readout chip can be allocated to I / O pads, test pads, wiring perimeters, etc.

[0095] This embodiment is in Figure 12 As shown in the image. Figure 12b) shows a top view of readout chip 2, without the sensor chip. According to Figure 12 In the legend at the bottom right, each ROC pixel and its input contact 12 are shown as a shaded rectangle. The corresponding RDL line, i.e., the input routing line, is represented by 43. From Figure 12 b) It can be seen that ROC pixel 21 is grouped into 3×3 subgroups. Figure 12 c) shows a transparent top view of one of the subgroups, also including the corresponding sensor pixel 12. Along Figure 12 c) Sectional view in the direction of the dashed line Figure 12 Figure d) shows a side cross-sectional view passing through the three intermediate input contacts 21 and sensor pixels 12, as well as the corresponding input wiring 43. This figure most clearly shows that the ROC pixel-sensor pixel combinations in the middle of each subgroup exhibit the shortest possible wiring, i.e., a vertical straight-line connection between the ROC pixel and its corresponding sensor pixel. Adjacent ROC pixel-sensor pixel combinations exhibit at least a moderate wiring length, shorter than the individual wiring lengths of ungrouped ROC pixels.

[0096] Figure 12 a) shows the arrangement in Figure 12 a) A transparent top view of sensor sheet 1 on top of ROC 2, wherein sensor pixels 12 are evenly arranged, i.e., the sensor pixel spacing is constant and no groups are formed.

[0097] Figure 15 A radiation detector module according to another embodiment of the present invention is shown. Its views and elements are similar to those of the present invention. Figure 12 Corresponding to the illustration. With Figure 12 Compared to the previous embodiment, sensor pixels 12 are not uniformly arranged, but rather arranged in groups. However, ROC pixels 21 are arranged in conjunction with... Figure 12 The same or similar group arrangements of the embodiments.

[0098] Therefore, according to Figure 15 a), which shows a transparent top view of sensor patch 1, with the corresponding sensor pixels 12 grouped into 3×3 subgroups, for example, in conjunction with the use of an anti-scattering grid. This arrangement can also be additionally applied to the subgrouping of ROC pixels. In this figure, the subgroups of sensor pixels are spaced further apart than the spacing between the sensor pixels within the subgroup.

[0099] Of course, besides 3×3, other subgroup sizes are also possible, such as 4×4, 5×5, etc. Non-square subgroups are also possible, such as 2×3, 4×3, etc.

[0100] Pulse signals from different ROC pixels can vary significantly in height and length. Differences in pulse shape can affect detector performance. Figure 13This illustrates one of the potential problems affecting detector performance associated with fan-out RDLs. Due to the pulse shape variation caused by the RDL, two signal pulses generated from the same X-ray or electron beam in two different ROC pixels may result in different count values. Figure 13 The top chart of a1 illustrates this effect, showing the effect for two different ROC pixels with different corresponding wiring lengths in the redistribution layer. Figure 11 The amplifier stage output changes over time. Signal (1) originates from the ROC pixel connected to the corresponding sensor pixel via a short wire, while signal (2) originates from the ROC pixel connected to the corresponding sensor pixel via a long wire. Signal (2), which accumulates more capacitance in the RDL, does not reach the threshold ETh2, while signal (1) easily exceeds this threshold. Therefore, it is preferable to adjust the threshold of the second ROC pixel associated with the higher capacitance signal input to ETh1. <ETh2。

[0101] Preferably, the individual threshold for each pixel can be set at least based on the individual wiring length in the redistribution layer. In one embodiment, the individual threshold can be set in a manner that does not involve any measurement for a single ROC pixel. Preferably, a minimum and a maximum possible value are predefined, and the individual threshold is set within a range between the minimum and the maximum value, also known as a tuning range.

[0102] In different embodiments, the response (e.g., the output signal of an amplifier stage) of each ROC pixel is determined using the same energy radiation sensor sheet. The threshold is adjusted pixel by pixel based on the measured response.

[0103] More generally, in this embodiment, the threshold is set or adjusted individually for each ROC pixel.

[0104] Figure 13 a2) shows the tuning range, where the highest threshold ETh2 is set to the threshold of the ROC pixel that generates signal (1), and the lowest threshold ETh1 is set to the threshold of the ROC pixel that generates signal (2). Figures 13b) and 13c) show the corresponding outputs of comparator 234 and re-trigger unit 235 for signals (1) and (2).

[0105] Figure 14 Another scheme for compensating for different wiring patterns and their associated different input capacitances in an RDL is shown. Here, the re-trigger time is adjusted individually for each pixel.

[0106] exist Figure 14In the top graph of (a), the left side shows the amplifier stage output signal of the ROC pixel connected to the corresponding sensor pixel via a short wire over time, and the right side shows the amplifier stage output signal of the ROC pixel connected to the corresponding sensor pixel via a long wire. The threshold ETh is set consistently for both / all ROC pixels and is set quite low, so even for high input capacitance ROC pixels ( Figure 14 The output signal of the right side of a can also reach the threshold ETh.

[0107] However, this results in the output signal exceeding the threshold ETh differing for a single pulse and for accumulated pulses. This can be seen from... Figure 14 As shown in b), the different comparator outputs reveal that if the same (short) re-trigger time Δt1 is applied to both ROC pixels, the counter may be triggered with three pulses for the first ROC pixel (left) and with four pulses for the second ROC pixel (right). Therefore, it is recommended to adjust or set different re-trigger times / lengths for each ROC pixel.

[0108] Preferably, the re-trigger time is set at least according to the wiring in the RDL, and in particular according to the length of each wiring.

[0109] Although the presently preferred embodiments of the invention have been shown and described, it should be clearly understood that the invention is not limited thereto, but may be practiced and implemented in various other ways within the scope of the appended claims.

[0110] List of reference numerals in the attached diagram: 1 sensor chip 11 Top Electrode 12 (sensor) pixels 13 Wiring Layer 131 output contact 132 wiring 2 Readout Chip 21 Input Contacts 22 Output contacts 23 Readout Circuit 231 amplifier stage 232 comparator 233 Threshold Generator 234 Pulse Evaluation Unit 3 solder bumps 4. Substrates, such as printed circuit boards 41 Input Contact 42 Output contacts 43 Input wiring 44 Output wiring 45 via 46 Additional output contacts 47. Wiring 5 Intermediate Layers 51 Input Contacts 52 output contacts 53 wiring 6 substrate 7 Readout Board 71 Input Contacts 72 output contacts 9 gaps 10 Radiation Detector Module

Claims

1. A radiation detector module (10) for position-resolved radiation detection, including - At least one sensor sheet (1) extending in two dimensions (x, y) of a horizontal plane, including • Sensor materials that are sensitive to radiation, • A set of pixels (12) made of conductive material are in contact with the sensor material. - At least one readout chip (2), arranged in parallel with the sensor sheet (1) and configured to process signals provided by the group of pixels (12), including • The extension in at least one of the two dimensions is smaller than the extension of the sensor piece (1) in that dimension. • A set of input contacts (21) are electrically connected to the pixel (12). • One or more output contacts (22) for providing the processed signal, - A substrate (4) arranged parallel to the sensor chip (1), and including • A set of input contacts (41). • Input wiring (43) electrically connects its input contact (41) to the input contact (21) of the readout chip (2). • One or more output contacts (42) located on its bottom surface, and • Output wiring (44, 45) connects one or more of its output contacts (42) to one or more output contacts (22) of the readout chip (2).

2. The radiation detector module (10) according to claim 1. - in, The spacing between the input contacts (21) of the readout chip (2) is smaller than the spacing between the pixels (12) of the sensor chip (1). - Wherein, the input wiring (43) includes via portions in the third dimension (z) orthogonal to the horizontal plane.

3. The radiation detector module (10) according to claim 2. in, The at least one readout chip (2) is embedded in the substrate (4). Wherein, the extension of the substrate (4) in at least one of the two dimensions (x, y) exceeds the extension of the readout chip (2) in that dimension (x, y). Preferably, the readout chip (2) is embedded in the substrate (4) from all its sides. Preferably, the material of the substrate (4) covers all surfaces of the readout chip (2). Preferably, the substrate (2) extends beyond the third dimension of the readout chip (2).

4. The radiation detector module (10) according to claim 3. - in, A set of input contacts (41) of the substrate (4) are arranged on its top surface. - Wherein, a set of input contacts (21) and one or more output contacts (22) of the readout chip (2) are arranged on its top surface, - Preferably, the input wiring (43) includes wiring disposed in one or more layers between the top surface of the substrate (4) and the top surface of the readout chip (2).

5. The radiation detector module (10) according to claim 4. in, The output wiring (44, 45) includes one or more vias (45) extending in the third dimension and passing through the substrate (4) and located next to the readout chip (2). Preferably, the input wiring (43) includes wiring disposed in one or more layers between the bottom surface of the substrate (4) and the top surface of the readout chip (2).

6. The radiation detector module (10) according to any one of the preceding claims. in, The extension of the substrate (4) in the two dimensions (x, y) is equal to or less than the extension of the sensor sheet (1) in the two dimensions (x, y).

7. The radiation detector module (10) according to any one of the preceding claims, comprising: - An intermediate layer (5) arranged parallel to the sensor sheet (1) includes a set of input contacts (51) arranged on its top surface and a set of output contacts (52) arranged on its bottom surface. The spacing of the input contacts (51) of the intermediate layer (5) is equal to the spacing of the pixels (12) of the sensor sheet (1), and The spacing of the output contacts (52) of the intermediate layer (5) is smaller than the spacing of its input contacts (51). The input contact (51) of the intermediate layer (5) is electrically connected to the pixel (12) of the sensor chip (1), and The output contact (52) of the intermediate layer (5) is electrically connected to the input contact (41) of the substrate (4).

8. The radiation detector module (10) according to any one of the preceding claims. in, The sensor chip (1) includes a monolithic integrated wiring layer (13) covering the set of pixels (12), the wiring layer (13) including • A set of output contacts (131) located on its bottom surface. • Wiring (132) electrically connects its output contact (131) to the sensor pixel (12), The spacing of the output contacts (131) of the wiring layer (13) is smaller than the spacing of the pixels (12) of the sensor sheet (1), and The spacing of the output contacts (131) of the wiring layer (13) is equal to the spacing of the input contacts (41) of the substrate (4), and The output contact (131) of the wiring layer (13) is electrically connected to the input contact (41) of the substrate (4).

9. The radiation detector module (10) according to claim 1 or 2. in, The substrate (4) is sandwiched between the sensor chip (1) and the readout chip (2). The substrate (4) includes additional output contacts (46) located on its bottom surface. The input wiring (43) connects the input contact (41) to the additional output contact (46). The additional output contact (46) is electrically connected to the input contact (21) of the readout chip (2). Preferably, it includes a bottom filler disposed between the substrate (4) and the readout chip (2).

10. The radiation detector module (10) according to any one of the preceding claims. in, The input contacts (21) of the readout chip (2) are arranged in groups. Among them, the spacing between input contacts (21) in the same group is smaller than the distance between input contacts (21) in adjacent groups.

11. The radiation detector module (10) according to any one of the preceding claims. in, The at least one readout chip (2) includes a set of readout circuits (23), each readout circuit (23) being electrically connected to an assigned input contact (21), and each readout circuit (23) being configured to process signals received from a sensor pixel (12) electrically connected to the assigned input contact (21). Each readout circuit (23) includes: • An amplifier stage (231) is configured to amplify the signal received at the corresponding input contact (21). • Comparator (232) is configured to compare the amplified signal with a threshold (ETH) and output a pulse during the period when the signal exceeds the threshold (ETH). • The pulse evaluation unit (234) is configured to evaluate the pulse received from the comparator (232) and generate x pulses of a defined length and / or count x events for each received pulse, x = 1 if the length Δtp of the received pulse is less than the defined length Δtd, otherwise x = an integer function of Δtp / Δtd.

12. The radiation detector module (10) according to claim 11. in, At least two different thresholds (ETH1, ETH2) are assigned in the readout circuit (23) of the readout chip (2), such that at least two readout circuits (2) have different assigned thresholds (ETH1, ETH2). Preferably, respective thresholds (ETH1, ETH2) are applied to the readout circuit (23). Preferably, the threshold assigned to the readout circuit (23) is defined based on the capacitance caused at least by the input wiring between the input contact (41) of the substrate (4) and the input contact of the readout chip (2).

13. The radiation detector module (10) according to claim 11 or 12. in, At least two different defined lengths Δtd are implemented in the readout circuit (23) of the readout chip (2), such that at least two readout circuits (2) have different implemented lengths (Δtd). Preferably, the readout circuit (23) is applied with its own defined length Δtd. Preferably, the length (Δtd) realized in the readout circuit (2) is defined based on the capacitance caused by the input wiring between the input contacts (41) of the substrate (4) and the input contacts of the readout chip (2).

14. The radiation detector module (10) according to any one of the preceding claims. in, The substrate (4) is one of a printed circuit board and a molded interconnect device. Preferably, all sides of the readout circuit (2) are covered by the material of the substrate (4).

15. The radiation detector module (10) according to any one of the preceding claims, comprising: - Two sensor chips (1) - Two readout chips (2) - Each readout chip (2) is electrically connected to only one assigned sensor chip (1), and the spacing between the input contacts (21) of each readout chip (2) is smaller than the spacing between the pixels (12) of the assigned sensor chip (1). - Wherein, the readout chip (2) is embedded in the substrate (4), Preferably, the input wiring (43) includes a via portion in a third dimension (z) orthogonal to the horizontal plane. Preferably, the output wiring (44, 45) includes one or more vias (45) extending in the third dimension and passing through the substrate (4) and located next to the readout chip (2). Preferably, the extension of the substrate (4) in at least one of the two dimensions (x, y) is more than twice the extension of the readout chip (2) in that dimension (x, y), and is equal to or less than the extension of the two sensor pieces (1) arranged in that dimension.

16. The radiation detector module (10) according to any one of the preceding claims. Includes means for compensating for capacitance variations between the input contacts (21) of the readout chip (2) caused at least by the input wiring (43).

17. Radiation detectors, including - Substrate (6), and - A radiation detector module (10) according to any of the preceding claims, disposed on the substrate (6).

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