X-ray sensor and method of forming same

Abstract

The disclosure provides an X-ray sensor and a method of forming the same. The X-ray sensor comprises a thin film transistor and a photodiode. The thin film transistor includes an oxide semiconductor layer electrically connected to and over the first source / drain region and the second source / drain region, a gate dielectric layer covering the oxide semiconductor layer, and a gate electrode on the gate dielectric layer, wherein the part, covered by the vertical projection of the gate electrode, of the oxide semiconductor layer serves as a channel of the thin film transistor. The photodiode is located on the first source / drain region. Wherein the oxide semiconductor layer includes a first oxide semiconductor portion extending over a top surface of the second source / drain region, a second oxide semiconductor portion extending along sidewalls of the photodiode, and a third oxide semiconductor portion extending over a top surface of the photodiode, therefore, the horizontal length of the channel can be reduced, the pixel area ratio of the photodiode can be increased, and the light conversion efficiency of the sensor can be improved.

Description

Technical Field

[0001] This disclosure relates to X-ray sensors and methods of their fabrication. Background Technology

[0002] An X-ray sensor receives X-rays from a target object and converts them into electronic signals to display an image of the target object on a monitor. Generally, an X-ray sensor has multiple pixels depending on its resolution. Each pixel includes a photodiode that receives light and a transistor that transmits electronic signals. The pixel area occupied by the photodiode affects the usable light-receiving area of ​​the X-ray sensor; however, the transistor also shares the pixel area, making it easy to limit the light-receiving area of ​​the X-ray sensor and thus difficult to improve its light conversion efficiency. Summary of the Invention

[0003] This disclosure provides an X-ray sensor and a method for forming the same, wherein the X-ray sensor increases the pixel area ratio of photodiodes to solve the aforementioned problems.

[0004] According to one embodiment of this disclosure, an X-ray sensor includes a thin-film transistor (TFT) and a photodiode. The TFT includes a first source / drain region and a second source / drain region located on a substrate and separated from each other; an oxide semiconductor layer located above and electrically connected to the first and second source / drain regions; a gate dielectric layer covering the oxide semiconductor layer; and a gate electrode located on the gate dielectric layer, wherein a portion of the oxide semiconductor layer covered by the vertical projection of the gate electrode serves as a channel of the TFT. The photodiode is located on the first source / drain region, wherein the oxide semiconductor layer includes a first oxide semiconductor portion extending above the top surface of the second source / drain region, a second oxide semiconductor portion extending along the sidewall of the photodiode, and a third oxide semiconductor portion extending above the top surface of the photodiode.

[0005] In some embodiments, the total length of the thin-film transistor channel is equal to the sum of the length of the second oxide semiconductor portion in the first direction and the length of the gate electrode in the second direction perpendicular to the first direction.

[0006] In some implementations, the vertical projection of the gate electrode overlaps the top surface of the photodiode.

[0007] In some implementations, the distance between the sidewall of the gate electrode and the sidewall of the photodiode is smaller than the distance between the sidewall of the oxide semiconductor layer and the sidewall of the photodiode.

[0008] In some embodiments, the gate electrode includes a first gate portion extending above the top surface of a first oxide semiconductor portion, a second gate portion extending along the sidewall of a second oxide semiconductor portion, and a third gate portion extending above the top surface of a third oxide semiconductor portion.

[0009] In some embodiments, the X-ray sensor further includes source / drain electrodes located above the top surface of the photodiode and extending into the first source / drain region, wherein the source / drain electrodes electrically connect the oxide semiconductor layer to the first source / drain region.

[0010] In some implementations, the source / drain electrodes cover a portion of the top surface of the oxide semiconductor layer and a portion of the top surface of the first source / drain region.

[0011] In some implementations, the distance between a portion of the sidewall of the photodiode located below the source / drain electrode and the sidewall of the first source / drain region is greater than the distance between the remaining portion of the photodiode's sidewall and the sidewall of the first source / drain region.

[0012] In some embodiments, the X-ray sensor further includes a conductive layer located on the top surface of the photodiode and electrically connected to the photodiode, wherein the distance between the sidewall of the oxide semiconductor layer and the sidewall of the photodiode is less than or equal to the distance between the sidewall of the conductive layer and the sidewall of the photodiode.

[0013] According to one embodiment of this disclosure, a method of forming an X-ray sensor includes the following steps: Forming a first source / drain region and a second source / drain region separated from each other on a substrate. Forming a photodiode and a conductive layer on the photodiode in the first source / drain region. Forming a first protective layer covering the first source / drain region, the second source / drain region, the photodiode, and the conductive layer. Forming a plurality of openings in the first protective layer to expose portions of the first source / drain region, the second source / drain region, and the conductive layer. Forming an oxide semiconductor layer in the first protective layer to contact the second source / drain region through one of the openings, wherein the oxide semiconductor layer includes an oxide semiconductor portion extending along the sidewall of the photodiode. Forming an electrode layer in the first protective layer, wherein the electrode layer includes source / drain electrodes that contact the oxide semiconductor layer and the first source / drain region through one of the openings, and a common electrode that contacts the conductive layer through one of the openings. Forming a gate dielectric layer covering the first protective layer, the oxide semiconductor layer, and the electrode layer. A gate electrode is formed on the gate dielectric layer, wherein the gate electrode includes a gate electrode portion extending along the sidewall of the oxide semiconductor portion. A second protective layer is formed to cover the gate dielectric layer and the gate electrode.

[0014] According to the above embodiments, the X-ray sensor disclosed herein includes a thin-film transistor and a photodiode, wherein the oxide semiconductor layer serving as a channel in the thin-film transistor includes an oxide semiconductor portion extending along the sidewall of the photodiode, thereby reducing the horizontal length of the channel and increasing the pixel area ratio of the photodiode, thus improving the light conversion efficiency of the X-ray sensor. Attached Figure Description

[0015] The various aspects of this disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industrial methods, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of discussion.

[0016] Figure 1 A top-view perspective view of an X-ray sensor is shown according to one embodiment of the present disclosure;

[0017] Figure 2 Draw Figure 1 A magnified view of a portion of the X-ray sensor in the image;

[0018] Figures 3A to 3F A diagram illustrating an embodiment of the present disclosure. Figure 1 Multiple cross-sectional views of the X-ray sensor in the image;

[0019] Figure 4 A cross-sectional view of an X-ray sensor is shown according to another embodiment of the present disclosure;

[0020] Figure 5 , Figure 6 , Figures 7A to 7C , Figure 8 , Figures 9A to 9C , Figures 10A to 10C , Figure 11 and Figures 12A to 12C Cross-sectional views of multiple stages of a process for forming an X-ray sensor are illustrated according to one embodiment of the present disclosure.

[0021] [Symbol Explanation]

[0022] 10,20: X-ray sensor

[0023] 100:Substrate

[0024] 102: First source / drain region

[0025] 102a: Sidewall

[0026] 104: Second source / drain region

[0027] 105: Thin-film transistor

[0028] 110: Photodiode

[0029] 110a, 110b: Sidewalls

[0030] 120: Conductor Layer

[0031] 120a, 120b: Sidewall

[0032] 130: First protective layer

[0033] 140: Oxide semiconductor layer

[0034] 142: First Oxide Semiconductor Section

[0035] 144: Second Oxide Semiconductor Section

[0036] 145: Through hole

[0037] 146: Third Oxide Semiconductor Section

[0038] 148: Fourth Oxide Semiconductor Section

[0039] 150: Electrode layer

[0040] 152: Source / Drain Electrode

[0041] 154: Common Electrode

[0042] 155, 156: Through holes

[0043] 160: Gate dielectric layer

[0044] 170: Gate electrode

[0045] 172: First gate portion

[0046] 174: Second gate portion

[0047] 175: Gate line

[0048] 176: Third gate section

[0049] 178: Fourth gate section

[0050] 180: Second protective layer

[0051] 190: Connector layer

[0052] 200: Source / Drain Contact

[0053] 210: Common electrode contact

[0054] 220: Gate contact

[0055] 270: Conductive layer

[0056] 500: Gap

[0057] 700, 710, 720: Opening

[0058] AA,BB,CC,DD,EE,FF: cut line

[0059] A1: Area

[0060] D1, D2: Distance

[0061] L1, L2: Length

[0062] X, Y, Z: Axes Detailed Implementation

[0063] To achieve the different features of the mentioned subject matter, the following disclosure provides many different embodiments or examples. Specific examples of components, configurations, etc., are described below to simplify this disclosure. Of course, these are merely examples and not limiting. For example, in the following description, forming a first feature on or over a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where an additional feature is formed between the first and second features such that the first and second features do not need to be in direct contact. Additionally, reference numerals and / or letters may be repeated in various examples. This repetition is for simplicity and clarity and does not in itself represent a relationship between the various embodiments and / or configurations discussed.

[0064] Furthermore, this document may use spatial relative terms such as “below,” “under,” “lower,” “above,” “upper,” etc., to facilitate the description of the relationship between one element or feature and another element or feature as shown in the figure. In addition to the orientations shown in the figure, spatial relative terms are intended to include different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other directions), and the spatial relative descriptive symbols used herein may be interpreted accordingly.

[0065] This disclosure provides an X-ray sensor and a method for forming the same, wherein the X-ray sensor includes a thin-film transistor (TFT) and a photodiode. The oxide semiconductor layer serving as a channel in the TFT includes an oxide semiconductor portion extending along the sidewall of the photodiode, thereby reducing the horizontal length of the channel and correspondingly increasing the pixel area ratio of the photodiode, thereby improving the light conversion efficiency of the X-ray sensor.

[0066] According to one embodiment of the present disclosure, Figures 1 to 3F Multiple views of the X-ray sensor 10 are shown, in which Figure 1 This is a top-view perspective view of the X-ray sensor 10. Figure 2 This is a magnified view of a portion of region A1 of the X-ray sensor 10. Figure 3AX-ray sensor 10 along Figure 1 Cross-sectional view of line AA in the diagram. Figure 3B X-ray sensor 10 along Figure 1 The cross-sectional view of line BB in the diagram. Figure 3C X-ray sensor 10 along Figure 1 The cross-sectional view of the cutoff line CC in the diagram. Figure 3D X-ray sensor 10 along Figure 1 The cross-sectional view of the cutoff line DD in the diagram. Figure 3E X-ray sensor 10 along Figure 1 The cross-sectional view of the cut-off line EE in the diagram, and Figure 3F X-ray sensor 10 along Figure 1 The cross-sectional view of line FF in the diagram is shown below. (Refer to the following...) Figures 1 to 3F The detailed structure of the X-ray sensor 10 is described.

[0067] The X-ray sensor 10 includes at least one pixel unit, wherein the pixel unit includes a thin film transistor (TFT) 105 located on a substrate 100 and a photodiode 110 electrically connected to the TFT 105. The X-ray sensor 10 can first convert incident X-rays into light (e.g., visible light) that can be received by the photodiode 110 by means of, for example, a scintillator, and the photodiode 110 then converts the light into an electronic signal that can be output by the TFT 105.

[0068] Specifically, the X-ray sensor 10 includes a substrate 100, a first source / drain region 102, a second source / drain region 104, a photodiode 110, a conductive layer 120, a first protective layer 130, an oxide semiconductor layer 140, an electrode layer 150, a gate dielectric layer 160, a gate electrode 170, and a second protective layer 180, wherein the first source / drain region 102, the second source / drain region 104, the oxide semiconductor layer 140, the gate dielectric layer 160, and the gate electrode 170 serve as thin-film transistors 105 corresponding to the photodiode 110.

[0069] The first source / drain region 102 and the second source / drain region 104 are located on the substrate 100 and are laterally separated in the Y-axis direction. The area of ​​the first source / drain region 102 in the XY plane can be larger than the area of ​​the second source / drain region 104. For example, the first source / drain region 102 can be a wide rectangle occupying the center of the pixel unit, while the second source / drain region 104 can be a narrow strip along the edge of the pixel unit in the X-axis direction. In the above example, the second source / drain region 104 can be a data line (DL) for transmitting the sensing signal of the photodiode 110. In some embodiments, the first source / drain region 102 and the second source / drain region 104 can be the source region and drain region of the thin-film transistor 105, respectively, or vice versa.

[0070] Photodiode 110 is located on and electrically connected to the first source / drain region 102. Photodiode 110 may be directly located on the first source / drain region 102, causing the bottom surface of photodiode 110 to physically contact the top surface of the first source / drain region 102, while the top surface of photodiode 110 is higher than the top surface of the second source / drain region 104. The area of ​​photodiode 110 in the XY plane may be less than or equal to the area of ​​the first source / drain region 102; for example, photodiode 110 may occupy 90% to 100% of the top surface of the first source / drain region 102. In some embodiments, photodiode 110 may be a PIN diode, wherein the PIN diode comprises sequentially stacked N-type semiconductor layers, intrinsically (I-type) semiconductor layers, and P-type semiconductor layers.

[0071] A conductive layer 120 is located on the photodiode 110 and electrically connected to it. The conductive layer 120 can serve as the upper electrode of the photodiode 110, while the second source / drain region 104 can serve as the lower electrode of the photodiode 110. In some embodiments, the conductive layer 120 can be a transparent conductor that directly contacts the top surface of the photodiode 110, such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO), to increase the light collection efficiency of the photodiode 110.

[0072] A first protective layer 130 covers the substrate 100, the first source / drain region 102, the second source / drain region 104, the photodiode 110, and the conductive layer 120, and fills the gap between the first source / drain region 102 and the second source / drain region 104 to provide protection and insulation. For example, the first protective layer 130 may be made of silicon oxide (SiO2). x ) or silicon nitride (SiN)x The single-layer or multi-layer structure formed by the photodiode 110. In some embodiments, the first protective layer 130 may substantially conformally cover the substrate 100, the first source / drain region 102, the second source / drain region 104, the photodiode 110, and the conductive layer 120.

[0073] An oxide semiconductor layer 140 is located on the first protective layer 130 to serve as the active layer of the thin-film transistor 105. The oxide semiconductor layer 140 may be located directly on the top surface of the first protective layer 130 and connected to the second source / drain region 104 via a via 145 through the first protective layer 130. The oxide semiconductor layer 140 may extend along the Y-axis direction to conformally cover the portion of the first protective layer 130 above the second source / drain region 104 and the photodiode 110. Since the top surface of the photodiode 110 is higher than the top surface of the second source / drain region 104, the oxide semiconductor layer 140 may include a portion extending along the sidewall of the photodiode 110 in the Z-axis direction.

[0074] For example, such as Figure 3A As shown, the oxide semiconductor layer 140 may include a first oxide semiconductor portion 142 extending above the top surface of the second source / drain region 104 in the Y-axis direction, a second oxide semiconductor portion 144 extending along the sidewall of the photodiode 110 in the Z-axis direction, a third oxide semiconductor portion 146 extending above the top surface of the first source / drain region 102 and the top surface of the photodiode 110 in the Y-axis direction, and a fourth oxide semiconductor portion 148 extending above the top surface of the photodiode 110 in the Y-axis direction. In other words, the projected area of ​​the oxide semiconductor layer 140 on the substrate 100 partially overlaps with the second source / drain region 104, the first source / drain region 102, and the photodiode 110.

[0075] The oxide semiconductor layer 140 extends above the top surface of the photodiode 110, thereby maximizing the extension length of the oxide semiconductor layer 140 along the sidewall of the photodiode 110 (i.e., the length L1 of the second oxide semiconductor portion 144 in the Z-axis direction). In some embodiments where the first protective layer 130 conformally covers the second source / drain region 104 and the photodiode 110, the length L1 of the second oxide semiconductor portion 144 may be approximately equal to the thickness of the photodiode 110 in the Z-axis direction. The second oxide semiconductor portion 144 can reduce the horizontal channel length of the thin-film transistor 105 in the Y-axis direction, which will be described in detail later.

[0076] In some embodiments, the oxide semiconductor layer 140 may be formed of a transparent semiconductor, such as a metal oxide material based on indium gallium zinc oxide (IGZO), to increase the light collection efficiency of the photodiode 110. The distance D1 in the Y-axis direction between the edge sidewall of the oxide semiconductor layer 140 and the sidewall of the photodiode 110 may be less than or equal to the distance between the sidewall of the conductive layer 120 and the sidewall of the photodiode 110, such that the oxide semiconductor layer 140 does not extend above the top surface of the conductive layer 120.

[0077] An electrode layer 150 is located on the first protective layer 130 to serve as a conductive path for the thin-film transistor 105 and the photodiode 110. Specifically, the electrode layer 150 may include a source / drain electrode 152 above the photodiode 110 to electrically connect the oxide semiconductor layer 140 to the first source / drain region 102. The source / drain electrode 152 can extend from above the photodiode 110 along the Z-axis to the first source / drain region 102 and is electrically connected to the first source / drain region 102 through a via 155 passing through the first protective layer 130. Since the source / drain electrode 152 electrically connects the oxide semiconductor layer 140 and the first source / drain region 102, the first source / drain region 102 simultaneously serves as a conductive path element for both the thin-film transistor 105 and the photodiode 110, thus simplifying the structure of the X-ray sensor 10.

[0078] In some embodiments, the source / drain electrode 152 may cover a portion of the top surface of the oxide semiconductor layer 140 to stabilize the conductive path between the oxide semiconductor layer 140 and the first source / drain region 102. The portion of the source / drain electrode 152 covering the oxide semiconductor layer 140 may be laterally separated from the via 155 in the X-axis direction to maintain the structural integrity of the thin-film transistor 105 channel and the photodiode 110. The via 155 may cover the sidewalls and a portion of the top surface of the first source / drain region 102 to stabilize the conductive path between the source / drain electrode 152 and the first source / drain region 102.

[0079] In some embodiments, the sidewalls of the photodiode 110 and the conductive layer 120 located below the source / drain electrode 152 may be recessed relative to the sidewalls of other portions of the photodiode 110 and the conductive layer 120, making it easier for the source / drain electrode 152 to be electrically connected to the first source / drain region 102. For example... Figure 2As shown, the distance in the Y-axis direction between the sidewall 110a of the photodiode 110 located below the source / drain electrode 152 and the sidewall 102a of the first source / drain region 102 is greater than the distance between the sidewall 110b of the photodiode 110 not located below the source / drain electrode 152 and the sidewall 102a of the first source / drain region 102. Similarly, the distance in the Y-axis direction between the sidewall 120a of the conductive layer 120 located below the source / drain electrode 152 and the sidewall 102a of the first source / drain region 102 is greater than the distance between the sidewall 120b of the conductive layer 120 not located below the source / drain electrode 152 and the sidewall 102a of the first source / drain region 102. This allows the source / drain electrode 152 to directly contact the top surface of the first source / drain region 102 through the through-hole 155.

[0080] Electrode layer 150 may further include a common electrode 154 above photodiode 110 for providing current to photodiode 110. The common electrode 154 extends across photodiode 110 along the X-axis from above photodiode 110 and is electrically connected to conductor layer 120 through a via 156 passing through first protective layer 130. Source / drain electrodes 152 and common electrode 154 are both located above photodiode 110 and can therefore be considered as electrode layers 150 of the same level. In some embodiments, electrode layer 150 may be a transparent conductor, such as indium tin oxide, indium zinc oxide, or zinc oxide, to increase the light collection efficiency of photodiode 110.

[0081] The gate dielectric layer 160 covers the first protective layer 130, the oxide semiconductor layer 140, and the electrode layer 150 to provide insulation between the oxide semiconductor layer 140 and the gate electrode 170. For example, the gate dielectric layer 160 may be a single-layer or multi-layer structure formed of silicon oxide or silicon nitride. In some embodiments, the gate dielectric layer 160 may substantially conformally cover the first protective layer 130, the oxide semiconductor layer 140, and the electrode layer 150.

[0082] Gate electrode 170 is located on gate dielectric layer 160, wherein the oxide semiconductor layer 140 below gate electrode 170 corresponds to a channel of thin-film transistor 105. Gate line 175 extends from gate electrode 170, conformally covering the portion of gate dielectric layer 160 above oxide semiconductor layer 140. Gate electrode 170 may extend from gate line 175, wherein gate line 175 extends along Y-axis direction to serve as a signal line (SL) for transmitting scan signals of photodiode 110.

[0083] For example, such as Figure 3AAs shown, the gate electrode 170 may include a first gate portion 172 extending above the top surface of the first oxide semiconductor portion 142 in the Y-axis direction, a second gate portion 174 extending along the sidewall of the second oxide semiconductor portion 144 in the Z-axis direction, a third gate portion 176 extending above the top surface of the third oxide semiconductor portion 146 in the Y-axis direction, and a fourth gate portion 178 extending above the top surface of the fourth oxide semiconductor portion 148 in the Y-axis direction.

[0084] The oxide semiconductor layer 140, covered by the vertical projection of the gate electrode 170, serves as a channel for the thin-film transistor 105. The total length of the channel includes its horizontal length in the Y-axis direction and its vertical length in the Z-axis direction. Specifically, the vertical length of the channel corresponds to the length L1 of the second oxide semiconductor portion 144 in the Z-axis direction, and the horizontal length of the channel corresponds to the length L2 of the gate electrode 170 in the Y-axis direction. With a fixed total length required for the channel, the vertical length of the channel can be reduced by decreasing the horizontal length. For example, if the total length required for the channel is approximately 3 micrometers, the vertical length of the channel can be approximately 1.2 micrometers, thereby reducing the horizontal length of the channel to approximately 1.8 micrometers.

[0085] The thin-film transistor 105 has a reduced horizontal channel length, thus reducing the pixel area ratio of the thin-film transistor 105 in the XY plane, thereby correspondingly increasing the pixel area ratio of the photodiode 110 in the XY plane. The larger the pixel area ratio of the photodiode 110, the larger the light-receiving area of ​​the X-ray sensor 10 and the higher the light conversion efficiency. In some embodiments, the pixel area ratio of the photodiode 110 can be referred to as the fill ratio of the photodiode 110, where the fill ratio is the ratio of the active area of ​​the photodiode 110 to the pixel area size. When the X-ray sensor 10 uses the thin-film transistor 105 in conjunction with the photodiode 110, the fill ratio of the photodiode 110 can be greater than or equal to 60%, for example, between 60% and 70%.

[0086] Furthermore, the thin-film transistor 105 uses the gate electrode 170 as the top layer of the stack, allowing the gate electrode 170 to shield the oxide semiconductor layer 140 below, which serves as the channel. Therefore, no additional light-shielding layer is needed to protect the oxide semiconductor layer 140, preventing additional light-shielding layers from occupying pixel area in the XY plane. The thin-film transistor 105 uses the sidewall of the photodiode 110 as the reference plane for the oxide semiconductor layer 140 to extend in the Z-axis direction. Therefore, no additional spacer layer is needed to provide a reference plane for the extension of the oxide semiconductor layer 140, thereby simplifying the fabrication steps of the X-ray sensor 10.

[0087] In some embodiments, the gate electrode 170 may extend above the top surface of the photodiode 110, such that the vertical projection portion of the gate electrode 170 overlaps the top surface of the photodiode 110 to maintain a sufficient horizontal channel length. For example... Figure 3A As shown, the fourth gate portion 178 of the gate electrode 170 extends above the top surface of the photodiode 110, wherein the sidewall of the fourth gate portion 178 above the photodiode 110 is spaced approximately 1 micrometer apart in the Y-axis direction by a distance D2 between it and the sidewall of the photodiode 110. The distance D2 between the sidewall of the fourth gate portion 178 and the sidewall of the photodiode 110 can be smaller than the distance D1 between the sidewall of the oxide semiconductor layer 140 and the sidewall of the photodiode 110, in order to increase the light-receiving area of ​​the photodiode 110.

[0088] The second protective layer 180 covers the gate dielectric layer 160 and the gate electrode 170 to provide protection and insulation. For example, the second protective layer 180 can be a single-layer or multi-layer structure formed of silicon oxide or silicon nitride. The second protective layer 180 can fill the recesses of the gate dielectric layer 160 and the gate electrode 170 and has a flat top surface. The thin-film transistor 105 is adjacent to the photodiode 110, and the thicknesses of the thin-film transistor 105 and the photodiode 110 are similar in the Z-axis direction. Therefore, the required thickness of the second protective layer 180 can be reduced, thereby thinning the X-ray sensor 10 and improving the light collection efficiency of the photodiode 110.

[0089] In some embodiments, the X-ray sensor 10 may further include source / drain contacts 200 located around the photodiode 110 and electrically connected to the second source / drain region 104. The source / drain contacts 200 include a first protective layer 130 on the second source / drain region 104, an electrode layer 150 on and through the first protective layer 130 contacting the second source / drain region 104, a gate dielectric layer 160 on the electrode layer 150, a conductive layer 270 on and through the gate dielectric layer 160 contacting the electrode layer 150, a second protective layer 180 on the conductive layer 270, and a pad conductor layer 190 on and through the second protective layer 180 contacting the conductive layer 270. The conductive layer 270 and the gate electrode 170 are at the same level, and the conductive layer 270 and the gate electrode 170 may be formed of the same conductive material. The pad conductor layer 190 can be a transparent conductor, such as indium tin oxide, zinc indium oxide, or zinc oxide.

[0090] In some embodiments, the X-ray sensor 10 may further include a common electrode contact 210 located around the photodiode 110 and electrically connected to the common electrode 154. The common electrode contact 210 includes a gate dielectric layer 160 on the common electrode 154, a conductive layer 270 on the gate dielectric layer 160 and extending through the gate dielectric layer 160 to contact the common electrode 154, a second protective layer 180 on the conductive layer 270, and a pad conductor layer 190 on the second protective layer 180 and extending through the second protective layer 180 to contact the conductive layer 270.

[0091] In some embodiments, the X-ray sensor 10 may further include a gate contact 220 located around the photodiode 110 and electrically connected to the gate line 175. The gate contact 220 includes a second protective layer 180 located on the gate line 175 and a pad conductor layer 190 located on the second protective layer 180 and extending through the second protective layer 180 to contact the gate line 175.

[0092] Figure 1 A pixel unit of an X-ray sensor 10 is illustrated, wherein the pixel unit may be defined by the intersection region of a data line (e.g., a second source / drain region 104 extending along the X-axis) and a signal line (e.g., a gate line 175 extending along the Y-axis). In some embodiments, the X-ray sensor 10 may include multiple Figure 1 It is a two-dimensional array composed of pixel units, and multiple pixel units can share data lines and signal lines.

[0093] According to another embodiment of this disclosure, Figure 4 Drawing X-ray sensor 20 along Figure 1 The cross-sectional view of line AA in the diagram. The X-ray sensor 20 is similar to... Figure 3A The X-ray sensor 10 is used in the X-ray sensor 20, but the first source / drain region 102 and photodiode 110 in the X-ray sensor 20 can have flush sidewalls below the gate electrode 170, which reduces the overlap between the gate electrode 170 and the first source / drain region 102, thereby reducing noise in the thin film transistor 105.

[0094] According to one embodiment of the present disclosure, Figures 5 to 12C Cross-sectional views of multiple stages in the process of forming an X-ray sensor are shown, in which Figure 5 , Figure 6 , Figure 7A , Figure 8 , Figure 9A , Figure 10A , Figure 11 and Figure 12A Draw along Figure 1 Cross-sectional view of line AA in the diagram. Figure 7B , Figure 9B , Figure 10B and Figure 12B Draw along Figure 1 The cross-sectional view of line BB in the diagram. Figure 7C , Figure 9C , Figure 10C and Figure 12C Draw along Figure 1 The cross-sectional view of the cutoff line CC in the diagram.

[0095] Figures 5 to 12C To form Figures 3A to 3C The X-ray sensor 10 in the example is shown, but Figures 5 to 12C The illustrated process can also be used to form other X-ray sensors within the scope of this disclosure. In some embodiments, certain steps may be performed in conjunction with... Figures 5 to 12C The diagrams illustrate different sequences, where some steps can occur simultaneously, some steps are unnecessary, and / or some steps can be repeated. Furthermore, it can be... Figures 5 to 12C Additional steps are performed before, during, or after each of the illustrated steps.

[0096] Reference to Figure 5 A first source / drain region 102 and a second source / drain region 104 are formed on the substrate 100, and a photodiode 110 and a conductive layer 120 on the photodiode 110 are formed on the first source / drain region 102. The first source / drain region 102 and the second source / drain region 104 can be separated by a gap 500 in the Y-axis direction, so that the photodiode 110 is formed only on the first source / drain region 102.

[0097] Reference to Figure 6 A first protective layer 130 is formed on the substrate 100, the first source / drain region 102, the second source / drain region 104, the photodiode 110, and the conductive layer 120. The first protective layer 130 can be formed using deposition processes such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), so that the first protective layer 130 conformally covers the top surface and sidewalls of the substrate 100, the first source / drain region 102, the second source / drain region 104, the photodiode 110, and the conductive layer 120, and the first protective layer 130 fills... Figure 5 The gap is 500.

[0098] Reference to Figures 7A to 7CAn etching process is performed to form openings 700, 710, and 720 in the first protective layer 130. Opening 700 exposes the top surface of the second source / drain region 104. Opening 710 exposes the top surface of the substrate 100 and the sidewalls of the first source / drain region 102. In some embodiments, opening 710 may also expose the top surface of the first source / drain region 102, wherein opening 710 is only partially formed on the top surface of the first source / drain region 102 to increase the pixel area ratio of the photodiode 110. Opening 720 exposes the top surface of the photodiode 110. The etching process may be, for example, an anisotropic etching process using patterned photoresist.

[0099] Reference to Figure 8 An oxide semiconductor layer 140 is formed on the first protective layer 130. The oxide semiconductor layer 140 can be formed over the second source / drain region 104 and the photodiode 110 using, for example, a conformal deposition process, such that the oxide semiconductor layer 140 includes a first oxide semiconductor portion 142 extending over the second source / drain region 104, a second oxide semiconductor portion 144 extending along the sidewall of the photodiode 110, a third oxide semiconductor portion 146 extending over the first source / drain region 102 and the photodiode 110, and a fourth oxide semiconductor portion 148 extending over the photodiode 110. The oxide semiconductor layer 140 is filled with material. Figure 7A An opening 700 is formed in the middle to create a via 145 that contacts the second source / drain region 104.

[0100] Reference to Figures 9A to 9C An electrode layer 150 is formed on the first protective layer 130. The electrode layer 150 can be formed over the first source / drain region 102 and the photodiode 110 by, for example, deposition or electroplating processes, such that the electrode layer 150 includes source / drain electrodes 152 electrically connecting the oxide semiconductor layer 140 and the first source / drain region 102. The electrode layer 150 is filled with material. Figure 7B An opening 710 is formed in the via 155 to contact the first source / drain region 102. The electrode layer 150 may also be formed above the conductor layer 120, such that the electrode layer 150 includes a common electrode 154 electrically connected to the conductor layer 120. The electrode layer 150 is filled with material. Figure 7C The opening 720 in the middle forms a through hole 156 for the contact wire layer 120.

[0101] Reference to Figures 10A to 10CA gate dielectric layer 160 is formed on the first protective layer 130, the oxide semiconductor layer 140, and the electrode layer 150. The gate dielectric layer 160 can be formed by, for example, a deposition process, such that the gate dielectric layer 160 conformally covers the top surface and sidewalls of the first protective layer 130, the oxide semiconductor layer 140, and the electrode layer 150.

[0102] Reference to Figure 11 A gate electrode 170 is formed on the gate dielectric layer 160. The gate electrode 170 can be conformally formed over the oxide semiconductor layer 140 by, for example, deposition or electroplating processes, such that the gate electrode 170 includes a first gate portion 172, a second gate portion 174, a third gate portion 176, and a fourth gate portion 178. The vertical projection of the gate electrode 170 may only cover a portion of the oxide semiconductor layer 140, such that the sidewalls of the gate electrode 170 are not flush with the sidewalls of the oxide semiconductor layer 140 in the YZ cross section.

[0103] Reference to Figures 12A to 12C A second protective layer 180 is formed on the gate dielectric layer 160 and the gate electrode 170. The second protective layer 180 can be formed by first depositing a protective layer material covering the gate dielectric layer 160 and the gate electrode 170 by a process such as chemical vapor deposition, and then performing a planarization process such as chemical mechanical polishing (CMP) on the protective layer material to form a second protective layer 180 with a flat top surface.

[0104] In some embodiments, the X-ray sensor process may further include forming a patterned conductive material on the second protective layer 180 as part of a contact electrically connected to the thin-film transistor 105 or photodiode 110, for example... Figures 3D to 3F The pad conductor layer 190 shown is illustrated.

[0105] according to Figures 5 to 12C In the illustrated fabrication process, the oxide semiconductor layer 140 in the thin-film transistor 105 uses the sidewall of the photodiode 110 as a vertically extending reference plane, and the gate electrode 170 in the thin-film transistor 105 directly serves as a light-shielding layer for the channel region. Therefore, the total number of photoresist layers and deposition steps used in the overall process can be reduced, thereby simplifying the process steps, reducing production costs, and improving production efficiency.

[0106] According to the above embodiments, the X-ray sensor disclosed herein includes a thin-film transistor and a photodiode. The thin-film transistor includes an oxide semiconductor layer as a channel, covered by the vertical projection of a gate electrode. The oxide semiconductor layer includes an oxide semiconductor portion extending along the sidewall of the photodiode. Therefore, the horizontal length of the channel can be reduced, thereby increasing the pixel area ratio of the photodiode. The oxide semiconductor portion uses the sidewall of the photodiode as a vertically extending reference plane, and the gate electrode serves as a light-shielding layer for the lower channel. Therefore, additional spacer layers or light-shielding layers can be omitted, simplifying the X-ray sensor manufacturing process.

[0107] The foregoing outlines features of some embodiments to enable those skilled in the art to better understand the ideas presented in this disclosure. Those skilled in the art should understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purpose and / or the same advantages as the embodiments described herein. Those skilled in the art should also understand that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure.

Claims

1. An X-ray sensor, characterized in that, include: A thin-film transistor, comprising; A first source / drain region and a second source / drain region are located on a substrate and are separated from each other; An oxide semiconductor layer is located above and electrically connected to the first source / drain region and the second source / drain region; A gate dielectric layer covering the oxide semiconductor layer; and A gate electrode is located on the gate dielectric layer, wherein a portion of the oxide semiconductor layer covered by a vertical projection of the gate electrode serves as a channel of the thin-film transistor; and a photodiode is located on the first source / drain region. The oxide semiconductor layer includes a first oxide semiconductor portion extending above a top surface of the second source / drain region, a second oxide semiconductor portion extending along a sidewall of the photodiode, and a third oxide semiconductor portion extending above a top surface of the photodiode.

2. The X-ray sensor as claimed in claim 1, characterized in that, The total length of the channel of the thin-film transistor is equal to the sum of the length of the second oxide semiconductor portion in a first direction and the length of the gate electrode in a second direction perpendicular to the first direction.

3. The X-ray sensor as described in claim 1, characterized in that, The vertical projection portion of the gate electrode overlaps with the top surface of the photodiode.

4. The X-ray sensor as claimed in claim 1, characterized in that, The distance between the sidewall of the gate electrode and the sidewall of the photodiode is less than the distance between the sidewall of the oxide semiconductor layer and the sidewall of the photodiode.

5. The X-ray sensor as claimed in claim 1, characterized in that, The gate electrode includes a first gate portion extending above a top surface of the first oxide semiconductor portion, a second gate portion extending along a sidewall of the second oxide semiconductor portion, and a third gate portion extending above a top surface of the third oxide semiconductor portion.

6. The X-ray sensor as claimed in claim 1, characterized in that, Further includes: A source / drain electrode is located above the top surface of the photodiode and extends to the first source / drain region, wherein the source / drain electrode electrically connects the oxide semiconductor layer to the first source / drain region.

7. The X-ray sensor as claimed in claim 6, characterized in that, The source / drain electrode covers a portion of the top surface of the oxide semiconductor layer and a portion of the top surface of the first source / drain region.

8. The X-ray sensor as claimed in claim 6, characterized in that, The distance between a portion of the sidewall of the photodiode located below the source / drain electrode and a sidewall of the first source / drain region is greater than the distance between the remaining portion of the sidewall of the photodiode and the sidewall of the first source / drain region.

9. The X-ray sensor as claimed in claim 1, characterized in that, Further includes: A conductive layer is located on the top surface of the photodiode and electrically connected to the photodiode. The distance between the sidewall of the oxide semiconductor layer and the sidewall of the photodiode is less than or equal to the distance between the sidewall of the conductive layer and the sidewall of the photodiode.

10. A method for forming an X-ray sensor, characterized in that, include: A first source / drain region and a second source / drain region, which are separated from each other, are formed on a substrate; A photodiode and a conductive layer on the photodiode are formed on the first source / drain region; A first protective layer is formed to cover the first source / drain region, the second source / drain region, the photodiode, and the conductive layer; Multiple openings are formed in the first protective layer to expose portions of the first source / drain region, the second source / drain region, and the conductor layer; An oxide semiconductor layer is formed on the first protective layer to contact the second source / drain region through one of the plurality of openings, wherein the oxide semiconductor layer includes an oxide semiconductor portion extending along the sidewall of the photodiode; An electrode layer is formed on the first protective layer, wherein the electrode layer includes a source / drain electrode that contacts the oxide semiconductor layer and the first source / drain region through one of the plurality of openings, and a common electrode that contacts the conductive layer through one of the plurality of openings. A gate dielectric layer is formed to cover the first protective layer, the oxide semiconductor layer, and the electrode layer; A gate electrode is formed on the gate dielectric layer, wherein the gate electrode includes a gate electrode portion extending along the sidewall of the oxide semiconductor portion; and A second protective layer is formed to cover the gate dielectric layer and the gate electrode.

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