Radiation sensing device and operating method thereof

A radiation sensing device is provided in the present disclosure. The radiation sensing device includes a substrate and a plurality of semiconductor units. The semiconductor units are disposed on the substrate, and at least one of the semiconductor units includes a first gate electrode, an active layer, and a second gate electrode. The active layer is disposed on the first gate electrode, and the second gate electrode is disposed on the active layer. The second gate electrode has a positive bias voltage during a standby mode. The second electrode may be configured to have a positive bias voltage during the standby mode for improving influence on electrical properties of the semiconductor unit after the semiconductor unit is irradiated by radiation.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to a radiation sensing device and an operation method thereof, and more particularly, to a radiation sensing device including semiconductor units and an operation method thereof.

2. Description of the Prior Art

Light sensing technology has been applied in many electronic products and inspection equipment with the related development, and the light sensing technology capable of detecting radiation (such as X-ray) is one of the applications that has received considerable attention. Because of properties such as low irradiation dose, fast electronic imaging, and convenience of viewing, copying, capturing, transferring, and analyzing electronic images, the traditional approach using films for detecting radiation has been gradually replaced by the digital radiation sensing device, and the digital radiation sensing device has become the current trend of development of digital medical imaging. In the general digital radiation sensing device, light sensing units are used to receive radiation energy and covert the radiation energy into electrical signals, and semiconductor switching units are used to control the reading of the signals. However, by the influence of the energy and/or the dose of the radiation during the irradiation, properties of stacked layers in the semiconductor switching units (such as a semiconductor channel layer, a gate dielectric layer, and/or a channel passivation layer) may change, and the electrical performance of the semiconductor switching units may be influenced accordingly. For instance, negative shift in the threshold voltage (Vth) of the semiconductor switching units may be generated, and there may be problems such as operation failure of the radiation sensing device accordingly.

SUMMARY OF THE DISCLOSURE

It is one of the objectives of the present disclosure to provide a radiation sensing device and an operation method thereof. A second gate electrode has a positive bias voltage during a standby mode for recovering influence on electrical properties of a semiconductor unit after the semiconductor unit is irradiated by radiation. The electrical performance of the semiconductor unit may be recovered to be normal, the influence of the radiation on the normal operation of the radiation sensing device may be avoided, and the lifetime of the radiation sensing device may be extended accordingly.

A radiation sensing device is provided in an embodiment of the present disclosure. The radiation sensing device includes a substrate and a plurality of semiconductor units. At least one of the semiconductor units is disposed on the substrate, and the semiconductor unit includes a first gate electrode, an active layer, and a second gate electrode. The active layer is disposed on the first gate electrode, and the second gate electrode is disposed on the active layer. The second gate electrode has a positive bias voltage during a standby mode.

An operation method of a radiation sensing device is provided in an embodiment of the present disclosure. The operation method includes the following steps. A radiation sensing device is provided. The radiation sensing device includes a substrate and semiconductor units disposed on the substrate. At least one of the semiconductor units includes a first gate electrode, an active layer, and a second gate electrode. The active layer is disposed on the first gate electrode. The second gate electrode is disposed on the active layer. The radiation sensing device is put into a standby mode, and the second gate electrode has a positive bias voltage during the standby mode.

DETAILED DESCRIPTION

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, equipment manufacturers may refer to a component by different names. This disclosure does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”.

The ordinal numbers, such as “first”, “second”, etc., used in the description and the claims are used to modify the elements in the claims and do not themselves imply and represent that the claim has any previous ordinal number, do not represent the sequence of some claimed element and another claimed element, and do not represent the sequence of the manufacturing methods. The use of these ordinal numbers is only used to make a claimed element with a certain name clear from another claimed element with the same name.

It should be understood that embodiments are described below to illustrate different technical features, but these technical features may be mixed to be used or combined with one another in different ways without conflicting with one another.

Please refer toFIG. 1andFIG. 2.FIG. 1is a schematic drawing illustrating a radiation system according to an embodiment of the present disclosure, andFIG. 2is a schematic diagram illustrating a part of a radiation sensing device101according to a first embodiment of the present disclosure. As shown inFIG. 1, in some embodiments, an object OB (such as human or other creatures or non-creatures) may be located between a radiation generating device901and the radiation sensing device101. Radiation may be generated by the radiation generating device901to the object OB, and the radiation sensing device101located behind the object OB is used to perform radiation sensing. The radiation sensing device101may convert the received radiation energy into electrical signals, and a processor device902(such as a computer device) connected with the radiation sensing device101may perform signal processing to generate a corresponding radiation image accordingly.

Please refer toFIG. 2,FIG. 3(a),FIG. 3(b), andFIG. 3(c).FIG. 2is a schematic diagram illustrating a part of the radiation sensing device101according to the first embodiment, andFIG. 3(a),FIG. 3(b), andFIG. 3(c)are schematic circuit diagrams of a part of the radiation sensing device101according to the first embodiment. As shown inFIG. 2, the radiation sensing device101in this embodiment may include a substrate10and a plurality of semiconductor units T. However, to concisely explain technical features of the present disclosure, there is only one semiconductor unit T illustrated in the drawings of the present disclosure. The semiconductor units T are disposed on the substrate10, and at least one of the semiconductor units T includes a first gate electrode G1, an active layer SC, and a second gate electrode G2. The active layer SC is disposed on the first gate electrode G1, and the second gate electrode G2is disposed on the active layer SC. Specifically, in some embodiments, the semiconductor unit T may further include a gate dielectric layer12, a source electrode SE, and a drain electrode DE. The gate dielectric layer12may be disposed between the first gate electrode G1and the active layer SC, and the source electrode SE and the drain electrode DE may be disposed on the active layer SC and the gate dielectric layer12, but not limited thereto. In addition, the radiation sensing device101may further include a protection layer14disposed on the source electrode SE, the drain electrode DE, and the active layer SC, and the second gate electrode G2may be disposed on the protection layer14. In some embodiments, the protection layer14may be regarded as a passivation layer or a channel passivation layer, but not limited thereto.

In some embodiments, the radiation sensing device101may further include at least one light sensing unit PU disposed on the substrate10, and the light sensing unit PU may include a photodiode, a capacitor structure, or other suitable photoelectric conversion unit. For example, the light sensing unit PU may include a first semiconductor layer P1, an intrinsic semiconductor layer P2, and a second semiconductor layer P3disposed in a direction perpendicular to a surface of the substrate10(such as a first direction D1), and the intrinsic semiconductor layer P2may be sandwiched between the first semiconductor layer P1and the second semiconductor layer P2accordingly. The first semiconductor layer P1may be electrically connected with a first terminal electrode E1, and the second semiconductor layer P3may be electrically connected with a second terminal electrode E2.

As shown inFIG. 2, in some embodiments, the radiation sensing device101may further include a first insulation layer16, a second insulation layer18, a first electrically conductive layer20, and a third insulation layer22. The first insulation layer16may be disposed on the second gate electrode G2and the protection layer14, the first terminal electrode E1described above may be disposed on the first insulation layer16, the first terminal electrode E1may be electrically connected with the drain electrode DE via an opening O1, and the opening O1may be formed with sidewalls of the protection layer14and the first insulation layer16above the drain electrode DE, but not limited thereto. The second insulation layer18may be disposed on the first insulation layer16, and the second insulation layer18may be disposed on the first terminal electrode E1, the light sensing unit PU, and the second terminal electrode E2also. The first electrically conductive layer20may be disposed on the second insulation layer18, and the first electrically conductive layer20may be electrically connected with the light sensing unit PU and the second terminal electrode E2for providing a reference voltage (such as a second voltage V2shown inFIG. 3(a)andFIG. 3(c)) to the light sensing unit PU and the second terminal electrode E2via an opening O2. The opening O2may be formed with sidewalls of the second insulation layer18located above the light sensing unit PU, but not limited thereto. The third insulation layer22may be disposed on the first electrically conductive layer20and the second insulation layer18.

In some embodiments, the substrate10may be a rigid substrate or a flexible substrate, and the material of the substrate10may include glass, plastic, ceramic materials, polyimide (PI), polyethylene terephthalate (PET), an arrangement combination of the above-mentioned materials, or other materials suitable for forming the substrate. The first gate electrode G1, the second gate electrode G2, the source electrode SE, the drain electrode DE, the first terminal electrode E1, the second terminal electrode E2, and the first electrically conductive layer20may respectively include electrically conductive materials, such as metallic conductive materials, transparent conductive materials, or other suitable types of electrically conductive materials. The metallic conductive materials described above may include at least one of aluminum, copper, silver, chromium, titanium, or molybdenum, a composed layer of the above-mentioned materials, or an alloy of the above-mentioned materials. The transparent conductive materials described above may include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), or other suitable transparent conductive materials. The materials of the gate dielectric layer12, the protection layer14, the first insulation layer16, the second insulation layer18, and the third insulation layer22described above may respectively include inorganic materials, such as silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide (Al2O3), and hafnium oxide (HfO2), organic materials, such as acrylic resin, or other suitable dielectric materials. In addition, the material of the active layer SC described above may include an amorphous silicon semiconductor material, a polysilicon semiconductor material, an organic semiconductor material, an oxide semiconductor material (such as indium gallium zinc oxide, IGZO), or other suitable semiconductor materials. It is worth noting that the radiation sensing device of the present disclosure is not limited to the structure shown inFIG. 2and/or the material properties described above, and other suitable structures and/or materials may also be applied in the radiation sensing device of the present disclosure.

As shown inFIG. 2,FIG. 3(a),FIG. 3(b), andFIG. 3(c), the first gate electrode G1of the semiconductor unit T may be connected to a scan line SL, the source electrode SE of the semiconductor unit T may be electrically connected to a data line DL, the drain electrode DE of the semiconductor unit T may be electrically connected with the light sensing unit PU, and another end of the light sensing unit PU may be connected to a reference voltage (such as a second voltage V2). It is worth noting that the connection condition of the source electrode SE and the connection condition of the drain electrode DE in the present disclosure may be replaced with each other. In other words, in some embodiments, the drain electrode DE may be electrically connected to the data line DL, and the source electrode SE may be electrically connected with the light sensing unit PU. In addition, the second gate electrode G2is not electrically connected with the source electrode SE, the drain electrode DE, and the active layer SC. In some embodiments, as shown inFIG. 3(a), the second gate electrode G2is not electrically connected with the light sensing unit PU. In some embodiments, as shown inFIG. 3(b), the second gate electrode G2is electrically connected with the light sensing unit PU.

In some embodiments, the light sensing unit PU may be formed by an amorphous silicon (a-Si) deposition process. For example, the intrinsic semiconductor layer P2may be an intrinsic amorphous silicon semiconductor layer, the first semiconductor layer P1may be a P-type semiconductor layer (such as a P-type doped amorphous silicon semiconductor layer), the second semiconductor layer P3may be an N-type semiconductor layer (such as a N-type doped amorphous silicon semiconductor layer), and the light sensing unit PU in this condition may be regarded as a PIN type photodiode (FIG. 3(a)may be the corresponding schematic circuit diagram). Additionally, in some embodiments, the first semiconductor layer P1may be an N-type semiconductor layer (such as a N-type doped amorphous silicon semiconductor layer), the second semiconductor layer P3may be a P-type semiconductor layer (such as a P-type doped amorphous silicon semiconductor layer), and the light sensing unit PU in this condition may be regarded as a NIP type photodiode (FIG. 3(c)may be the corresponding schematic circuit diagram), but not limited thereto. Additionally, in some embodiments, the radiation sensing device may include a plurality of the semiconductor units T and the corresponding light sensing units PU described above, the semiconductor units T and the corresponding light sensing units PU may be disposed and arranged in an array configuration, and the radiation sensing device may be regarded as an active matrix radiation sensing panel, but not limited thereto.

Please refer toFIG. 1andFIG. 4.FIG. 4is a schematic diagram illustrating timings of the radiation system according to an embodiment of the present disclosure. As shown inFIG. 4, an operation method of the radiation sensing device101in this embodiment may include the following steps. In some embodiments, the radiation sensing device101may enter a standby mode after being powered on, and an irradiation start signal may be transmitted to the radiation sensing device101and the radiation generating device901by an operator before the formal exposure of the radiation (such as X-ray) by the radiation generating device901. In other words, the radiation sensing device101may enter a photography mode from the standby mode by receiving the irradiation start signal. It is worth noting that the radiation sensing device101described is provided, and the radiation sensing device101is put into a standby mode. The second gate electrode G2has a positive bias voltage during the standby mode, and the second gate electrode G2may be positively biased during the standby mode.

In the photography mode, some of the light sensing units PU may be used to sense the radiation energy and accumulate the received radiation energy, an irradiation stop signal may be received by the radiation generating device901for stopping the radiation subsequently, and a comprehensive scan may then be executed by the radiation sensing device101for performing an image reading action. Finally, the photography mode may be ended after the image reading action is completed, and the radiation sensing device may return to the standby mode from the photography mode after the image reading action. For example, before the irradiation is finished, the semiconductor unit T may be controlled by the first gate electrode G1to be closed, and a charge accumulation action may be performed by the light sensing unit T exposed to the radiation. Comparatively, when the image reading action is performed, the semiconductor unit T may be controlled by the first gate electrode G1to be opened for reading signals from the light sensing unit PU.

In the operation method of the present disclosure, beyond the time between the radiation sensing device101receiving the irradiation start signal and completing the image reading action (such as the photography mode shown inFIG. 4), the radiation sensing device101may be regarded as being put in the standby mode. In the standby mode, the semiconductor unit T may be controlled by the first gate electrode G1to be closed, and a pixel reset action may be performed in the light sensing units PU for being ready for the next radiation exposure. It is worth noting that, in the standby node, the second gate electrode G2may have a positive bias voltage (such as a first voltage V1shown inFIG. 3(a)andFIG. 3(c)) for recovering the influence on electrical properties of the semiconductor unit T after the semiconductor unit T is irradiated by the radiation, and the electrical performance of the semiconductor unit T may be recovered to be normal. In some embodiments, there may be not any voltage applied to the second gate electrode G2during the photography mode described above, but not limited thereto.

Specifically, in some embodiments, by the influence of the energy and/or the dose of the radiation during the irradiation, properties of stacked layers in the semiconductor units T (such as the active layer SC, the gate dielectric layer12, and/or the protection layer14) may change, and the electrical performance of the semiconductor switching units may be influenced accordingly. For instance, the energy gap of the active layer SC and the portions of the active layer SC adjacent to other dielectric layers (such as the gate dielectric layer12and the protection layer14) may be influenced by the radiation and bend downward, and negative shift in the threshold voltage (Vth) of the semiconductor unit T may be generated accordingly. However, in the present disclosure, the electrons in the protection layer14may accumulate at a side adjacent to the active layer by positively biasing the second gate electrode G2of the radiation sensing device during the standby mode, and the energy gap of the active layer SC may be recovered to be the normal condition before being irradiated by the radiation. In other words, by positively biasing the second gate electrode G2for a specific period during the standby mode, the energy gap of the active layer SC may be raised to be normal, positive shift in the threshold voltage of the semiconductor unit T may be generated accordingly, and the threshold voltage of the semiconductor unit T may be recovered to be normal.

For example, in the operation method of this embodiment, the second gate electrode G2may have a positive bias voltage during the standby mode of the radiation sensing device101for performing a recovery treatment, and a treatment time of the recovery treatment may range from 1 minute to 60 minutes, from 5 minutes to 20 minutes, 5 minutes to 10 minutes, or other suitable time ranges. In other words, in some embodiments, the second gate electrode G2may have a positive bias voltage during a portion of the period of the standby mode of the radiation sensing device101for providing the treatment effect described above, but not limited thereto. In some embodiments, the second gate electrode G2may have a positive bias voltage during the whole period of the standby mode of the radiation sensing device101. In addition, a signal applied to the second gate electrode G2during the standby mode may include a DC signal, an AC signal, or signals of other suitable types, and the positive bias voltage applied to the second gate electrode G2in the recovery treatment may range from 5 volts to 20 volts or other suitable voltage ranges, and that may be adjusted according to design and will not be limited thereto. In some embodiments, there may be not any voltage applied to the first gate electrode G1during the recovery treatment described above, but not limited thereto. In some embodiments, when the negative shift in the threshold voltage of the semiconductor unit T influenced by the radiation is too significant, the first gate electrode G1may be positively biased in the recovery treatment described above and/or in the standby mode described above for closing the semiconductor unit T. In other words, the first gate electrode G1may also have a positive bias voltage in the standby mode, but not limited thereto.

Please refer toFIG. 5.FIG. 5is a schematic diagram illustrating the relationship between a drain current (ID) of the semiconductor unit T in the radiation sensing device101and a gate voltage (VG) of the semiconductor unit T (I-V curve) in this embodiment, wherein a first relation line L1stands for the I-V curve of the semiconductor unit after being exposed to radiation, and a second relation line L2stands for the I-V curve of the semiconductor unit after being exposed to radiation and being treated by the recovery treatment described above. From the first relation line L1, it is known that the threshold voltage of the semiconductor unit T is negatively shifted due to the radiation. Then, from the second relation line L2, it is known that the recovery effect may be achieved by the positive bias voltage of the second gate electrode G2in the standby mode. In other words, the threshold voltage of the semiconductor unit T after the recovery treatment may be higher than the threshold voltage of the semiconductor unit T before the recovery treatment.

By the radiation sensing device101and the operation method thereof in the present disclosure, the influence of the radiation on the electrical properties of the semiconductor unit T may be recovered, the electrical performance of the semiconductor unit T may be recovered to be normal, the influence of the radiation exposure on the normal operation of the radiation sensing device101may be avoided, and the lifetime of the radiation sensing device101may be extended accordingly. For example, in some embodiments, the negative shift in the threshold voltage may be recovered with about 1 volt by modifying the manufacturing processes of the stacked layers (such as the active layer SC, the gate dielectric layer12, and/or the protection layer14), and the negative shift in the threshold voltage may be recovered with about 4 volts by the method of positively biasing the second gate electrode G2in the present disclosure without modifying the process conditions of each of the stacked layers. Other negative influence of modifying the process conditions of each of the stacked layers (such as negative influence on the stability and/or the reliability) may be avoided accordingly.

The following description will detail the different embodiments of the present disclosure. To simplify the description, identical components in each of the following embodiments are marked with identical symbols. For making it easier to understand the differences between the embodiments, the following description will detail the dissimilarities among different embodiments and the identical features will not be redundantly described.

Please refer toFIG. 6.FIG. 6is a schematic diagram illustrating a radiation sensing device102according to an exemplary example of the first embodiment of the present disclosure. As shown inFIG. 6, the radiation sensing device102may further include an insulation layer13disposed on the active layer SC, and the source electrode SE and the drain electrode DE may be disposed on the insulation layer13. In this embodiment, the insulation layer13may be called an etching stop layer configured to protect the active layer SC during the manufacturing process of forming the source electrode SE and the drain electrode DE.

Please refer toFIG. 7.FIG. 7is a schematic diagram illustrating a radiation sensing device103according to another exemplary example of the first embodiment of the present disclosure. As shown inFIG. 7, the insulation layer13may be further sandwiched between the source electrode SE and the active layer SC and between the drain electrode DE and the active layer SC. The insulation layer13may have a first opening (such as an opening O3) and a second opening (such as an opening O4). The source electrode SE and the drain electrode DE may be electrically connected with the active layer via the opening O3and the opening O4respectively, and the opening O3and the opening O4may be formed with sidewalls of the insulation layer13located above the active layer SC, but not limited thereto.

Please refer toFIG. 8andFIG. 9.FIG. 8is a schematic diagram illustrating a radiation sensing device104according to a second embodiment of the present disclosure, andFIG. 9is a schematic circuit diagram of a part of the radiation sensing device104in the second embodiment. As shown inFIG. 8andFIG. 9, in the radiation sensing device104, the light sensing unit PU may include a capacitor structure CS optionally, and the capacitor structure CS may be formed with two electrically conductive layers and a dielectric material sandwiched between the two electrically conductive layers, such as being formed with a fourth electrically conductive layer17, a fifth electrically conductive layer19, and the second insulation layer18, but not limited thereto. In addition, the radiation sensing device104may further include a third electrically conductive layer15, a fourth insulation layer21, and a second electrically conductive layer24. The third electrically conductive layer15may be disposed on the protection layer14, and the first insulation layer16may be disposed on the third electrically conductive layer15. The third electrically conductive layer15may be electrically connected with the source electrode SE via an opening O5and electrically connected with the drain electrode DE via an opening O6. The opening O5and the opening O6may be formed with sidewalls of the protection layer14above the source electrode SE and the drain electrode DE. The fourth electrically conductive layer17described above may be disposed on the first insulation layer16, and the fourth electrically conductive layer17may contact the third electrically conductive layer15via an opening O7penetrating the first insulation layer16above the third electrically conductive layer15. In other words, the fourth electrically conductive layer17may be electrically connected with the drain electrode DE of the semiconductor unit T via the third electrically conductive layer15, but not limited thereto. The fifth electrically conductive layer19may be disposed on the second insulation layer18, and the first electrically conductive layer20may be disposed on and electrically connected with the fifth electrically conductive layer19for applying a reference voltage (such as a second voltage V2shown inFIG. 9) to the fifth electrically conductive layer19.

In addition, the fourth insulation layer21may be disposed on the first electrically conductive layer20, the fifth electrically conductive layer19, and the second insulation layer18. The third insulation layer22may be disposed on the fourth insulation layer21. The second electrically conductive layer24may be disposed on the third insulation layer22. The second electrically conductive layer24may be electrically connected with the fourth electrically conductive layer17via an opening O8, and the opening O8may be formed with the sidewalls of the second insulation layer18, the fourth insulation layer21, and the third insulation layer22above the fourth electrically conductive layer17, but not limited thereto. It is worth noting that, the capacitor structure CS and specific material (such as selenium or other suitable materials) disposed on the capacitor structure CS are used for sensing in this embodiment. A scintillator layer (not shown) may be used for the photodiode in the above-mentioned embodiments and converting radiation into visible light, and light sensing may then be performed by the photodiode accordingly, but not limited thereto.

To summarize the above descriptions, in the radiation sensing device and the operation method thereof in the present disclosure, the second gate electrode may have a positive bias voltage during the standby mode for recovering the influence of the radiation on the electrical properties of the semiconductor unit, and the electrical performance of the semiconductor unit may be recovered to be normal. The influence of the radiation exposure on the normal operation of the radiation sensing device may be avoided, and the lifetime of the radiation sensing device may be extended accordingly.