An active pixel sensor and a processing method

Abstract

Embodiments of the present disclosure disclose an active pixel sensor and a processing method. The active pixel sensor includes: a pixel device layer having a plurality of pixel regions; a collimation frame having a support portion and a collimation portion, the support portion being disposed on the pixel device layer, and the collimation portion being disposed on the support portion; the collimation portion having a boundary wall and an inner wall, the boundary wall enclosing a plurality of collimation channels, each collimation channel corresponding to a position of each pixel region one by one, the inner wall being disposed within the collimation channels formed by the boundary wall, the radial dimension of the collimation channels matching the dimension of the pixel regions; the collimation portion being configured to guide electrons to fall on corresponding pixel regions.

Description

Technical Field

[0001] The present invention relates to the field of optical devices, and more particularly, to an active pixel sensor and a processing method thereof. Background Art

[0002] An electron bombardment type active pixel sensor is a high-performance low-light imaging device, which adopts a light-optoelectron-electron multiplication mode. When the substrate of the active pixel sensor is thinned and the photoelectrons emitted from the photocathode bombard the back of the substrate under the action of the accelerating electric field, electron-hole pairs are generated due to the dissipation of the incident photoelectron energy, and electron bombardment semiconductor gain is obtained.

[0003] The electrons emitted from the photocathode have a transverse initial velocity and do not emit vertically aiming at the predetermined pixel area. Therefore, it is possible to bombard other non-predetermined pixel positions, resulting in crosstalk; in addition, the emitted electrons are accelerated by the electric field to become high-energy electrons, which are used to impact, for example, the anode of an image sensor, generating backscattered electrons or secondary electrons. These electrons may jump into adjacent non-predetermined pixel positions, causing secondary bombardment of the anode of other non-predetermined pixel positions, and thus forming a crosstalk problem.

[0004] Therefore, a new technical solution is needed to solve the above technical problems. Summary of the Invention

[0005] An object of the present invention is to provide a new technical solution for an active pixel sensor.

[0006] According to a first aspect of the present invention, there is provided an active pixel sensor. The active pixel sensor includes: a pixel device layer having a plurality of pixel regions; a collimation frame having a support portion and a collimation portion, the support portion being disposed on the pixel device layer, and the collimation portion being disposed on the support portion; the collimation portion having a boundary wall and an inner wall, the boundary wall enclosing a plurality of collimation channels, each collimation channel corresponding to a position of each pixel region one by one, the inner wall being disposed within the collimation channel surrounded by the boundary wall, and a radial dimension of the collimation channel matching a dimension of the pixel region; the collimation portion being configured to guide electrons to fall on the corresponding pixel region.

[0007] Optionally, the support portion includes a support wall, and a position of the support wall corresponds to a position of the boundary wall.

[0008] Optionally, a support wall is formed between each boundary wall and the pixel device layer.

[0009] Optionally, the support wall and the boundary wall are integrally formed.

[0010] Optionally, the inner wall includes a first inner wall and a second inner wall, the first inner wall and the second inner wall are spaced apart, and the first inner wall is closer to the boundary wall than the second inner wall.

[0011] Optionally, the distance between the first inner wall and the boundary wall is less than the distance between the first inner wall and the second inner wall.

[0012] Optionally, the first inner wall and the second inner wall are annularly distributed around the center of the collimation channel, and the first inner wall surrounds the second inner wall;

[0013] The radial dimension of the second inner wall is greater than the distance between the first inner wall and the second inner wall;

[0014] The distance between the first inner wall and the second inner wall is greater than the distance between the first inner wall and the boundary wall.

[0015] Optionally, the collimation part further has a connecting wall, and the connecting wall is configured to connect and fix the inner wall to the boundary wall.

[0016] Optionally, in the collimation channel, the connecting wall and the inner wall and / or the boundary wall jointly enclose a plurality of sub-channels.

[0017] Optionally, the connecting wall and the boundary wall and the first inner wall enclose a plurality of first sub-channels;

[0018] The connecting wall and the first inner wall and the second inner wall enclose a plurality of second sub-channels;

[0019] The radial dimension of the second sub-channel is greater than the radial dimension of the first sub-channel.

[0020] Optionally, the second inner wall is annularly distributed by itself, surrounding a third sub-channel, and the radial dimension of the third sub-channel is greater than the radial dimension of the second sub-channel.

[0021] Optionally, the ratio of the height of the collimation frame to the radial dimension of the pixel region ranges from 1.5 to 4.

[0022] Optionally, the ratio of the height of the collimation frame to the radial dimension of the pixel region is 2.

[0023] According to another aspect of the present invention, a method for processing an active pixel sensor is provided. The method includes: providing a pixel device layer having a plurality of pixel regions; depositing a first substrate layer on the pixel device layer, etching the first substrate layer to form a support portion; depositing a sacrificial layer around the support portion; depositing a second substrate layer on the support portion and the sacrificial layer, etching the second substrate layer to form a collimation portion; and releasing the sacrificial layer.

[0024] Optionally, when etching the first substrate layer, a strip-shaped mask is provided at the edge corresponding to the pixel region, and a support wall is formed by etching the first substrate layer;

[0025] When etching the second substrate layer, a strip-shaped mask is provided at the position corresponding to the support wall, the thickness of the strip-shaped mask is the same as the thickness of the support wall, and a boundary wall is formed by etching the second substrate layer, so that the thickness of the boundary wall is the same as the thickness of the support wall.

[0026] Optionally, when etching the second substrate layer, at the position corresponding to the pixel region, strip-shaped masks are provided on the second substrate layer in a cross distribution, and inner walls in a cross distribution are formed by etching.

[0027] In the embodiment of the present disclosure, a collimation frame is provided on the pixel device layer, and the collimation part of the collimation frame has inner walls and a boundary wall. The double walls collimate the electrons emitted by the photocathode, so that the electrons can fall into the predetermined pixel region smoothly and effectively, avoiding the crosstalk phenomenon caused by the electrons falling into other pixel regions, and finally achieving the purpose of improving the image quality.

[0028] Other features and advantages of the present invention will become clear from the following detailed description of the exemplary embodiments of the present invention with reference to the accompanying drawings. Description of the Drawings

[0029] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present invention and, together with the description, are used to explain the principles of the present invention.

[0030] Figure 1 is a cross-sectional view of an active pixel sensor according to an embodiment of the present disclosure.

[0031] Figure 2 is a top view of a collimation frame according to an embodiment of the present disclosure.

[0032] Figure 3 is a schematic diagram of the first bombardment of electrons emitted by a photocathode according to an embodiment of the present disclosure.

[0033] Figure 4 is a schematic diagram of the second bombardment of electron reflection according to an embodiment of the present disclosure.

[0034] Figures 5 - 10 is a schematic diagram of a processing method of an active pixel sensor according to an embodiment of the present disclosure.

[0035] Description of the Reference Numerals:

[0036] 1. Pixel device layer; 11. Pixel area; 21. Support part; 211. Support wall; 22. Collimation part; 221. Boundary wall; 2211. Collimation channel; 222. Inner wall; 2221. First inner wall; 2222. Second inner wall; 223. Connection wall; 2231. First sub-channel; 2232. Second sub-channel; 2233. Third sub-channel; 3. Photoelectric cathode; 301. First emitted electron; 302. Second emitted electron; 303. First scattered electron; 304. Second scattered electron; 4. First substrate layer; 5. Second substrate layer; 6. Sacrificial layer. Detailed implementation mode

[0037] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements, numerical expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0038] The following description of at least one exemplary embodiment is merely illustrative in nature and in no way serves as a limitation on the present invention or its application or use.

[0039] Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said techniques, methods and devices should be regarded as part of the specification.

[0040] In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0041] It should be noted that: similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0042] According to an embodiment of the present disclosure, an active pixel sensor is provided. As Figure 1 shown, the active pixel sensor includes: a pixel device layer 1 and a collimation frame.

[0043] The pixel device layer 1 has a plurality of pixel areas 11. The collimation frame has a support part 21 and a collimation part 22. The support part 21 is disposed on the pixel device layer 1. The collimation part 22 is disposed on the support part 21. The collimation part 22 has a boundary wall 221 and an inner wall 222. The boundary wall 221 encloses a plurality of collimation channels 2211. Each collimation channel 2211 corresponds to the position of each pixel area 11 one by one. The inner wall 222 is disposed within the collimation channel 2211 surrounded by the boundary wall 221. The radial dimension of the collimation channel 2211 matches the dimension of the pixel area 11. The collimation part 22 is configured to guide electrons to fall on the corresponding pixel area 11.

[0044] The pixel device layer 1 may have a plurality of pixel regions 11. Each pixel region 11 is used to receive the corresponding electrons emitted by the photocathode 3. A collimation frame is provided on the pixel device layer 1. The collimation frame is used to collimate the electrons emitted by the photocathode 3, intercept the electrons with too large lateral velocity and deviated movement trajectories, so that the emitted electrons accurately bombard the predetermined pixel region 11, preventing the emitted electrons from entering other pixel regions 11 and causing crosstalk phenomena, which affect the image quality.

[0045] For example, as Figures 3 - 4 shown, the working principle of the collimation frame of this embodiment will be described in detail:

[0046] As Figure 3 shown, due to the action of the accelerating electric field, the first emitted electron 301 and the second emitted electron 302 emitted by the photocathode 3 generally move vertically downward in an accelerated manner. However, due to the lateral initial velocity at the time of emission, the positions where they reach the corresponding pixel regions 11 on the pixel device layer 1 have a certain lateral offset relative to the positions where the photocathode 3 emits. Therefore, the first emitted electron 301 and the second emitted electron 302 may fall into other pixel regions 11, causing crosstalk phenomena.

[0047] In the embodiment of the present disclosure, a collimation frame is provided above the pixel device layer 1, and the collimation frame has an inner wall 222. The first emitted electron 301 and the second emitted electron 302 with a relatively large lateral initial velocity at the time of emission will collide with the inner wall 222 or the boundary wall 221, which can prevent the electrons emitted by the photocathode 3 from entering other pixel regions 11, and thus also avoid the generation of crosstalk problems.

[0048] As Figure 4 shown, after the first emitted electron 301 and the second emitted electron 302 bombard the predetermined pixel region 11, some backscattered electrons or secondary electrons may be generated due to reflection or other situations, such as the first scattered electron 303 and the second scattered electron 304. After the first scattered electron 303 and the second scattered electron 304 move a certain distance towards the photocathode 3, they are secondarily bombarded on the pixel device layer 1 under the action of the electric field. The first scattered electron 303 and the second scattered electron 304 in the predetermined pixel region 11 may also jump into other pixel regions 11 during the secondary bombardment process.

[0049] In the embodiment of the present disclosure, a collimation frame is provided above the pixel device layer 1, and the collimation frame can prevent the first scattered electron 303 and the second scattered electron 304 from rebounding and entering other pixel regions 11, and thus also avoid the generation of crosstalk problems.

[0050] As Figure 1As shown, the collimation frame has a support portion 21 and a collimation portion 22. The support portion 21 is disposed on the pixel device layer 1. The collimation portion 22 is disposed on the support portion 21. The support portion 21 is in contact with the pixel device layer 1 and can support a suspended area formed between the collimation portion 22 and the pixel device layer 1. As Figure 1 shown, there is a distance between the collimation portion 22 and the pixel device layer 1. The collimation portion 22 is relatively far from the pixel device layer 1, that is, relatively closer to the photocathode 3. In this way, electrons emitted from the photocathode 3 with a large initial lateral velocity are more likely to strike the inner wall 222 or the boundary wall 221, and thus are not likely to jump into other pixel regions 11.

[0051] If the collimation portion 22 is relatively close to the pixel device layer 1, then even if electrons have a relatively small initial lateral velocity during emission, at a position close to the pixel device layer 1, they may strike the inner wall 222 and thus be intercepted. This implementation causes electrons that could originally bombard the pixel device layer 1 normally to be absorbed by the collimation frame before reaching the corresponding pixel region 11, which will result in more electrons being intercepted and such a design will cause some signal loss. In the technical solution, the distance between the collimation portion 222 and the pixel device layer 1 can be changed.

[0052] The collimation portion 22 has a boundary wall 221 and an inner wall 222. The boundary wall 221 encloses a plurality of collimation channels 2211. Each collimation channel 2211 corresponds to the position of each pixel region 11 one by one. The radial dimension of the collimation channel 2211 matches the dimension of the pixel region 11. The plurality of collimation channels 2211 enclosed by the boundary wall 221 correspond to the positions of each pixel region 11. The boundary wall 221 can collimate the electrons entering each pixel region 11, preventing the electrons emitted from the photocathode 3 from falling into other pixel regions 11 and generating crosstalk.

[0053] For the technical feature that the radial dimension of the above collimation channel 2211 matches the dimension of the pixel region 11, there are various implementation manners in practical applications. For example, when the pixel region 11 is a rectangular or square area, the boundary wall 221 can enclose a square or rectangular collimation channel 2211. The radial side length of the square collimation channel 2211 is the same as or substantially consistent with the side length of the pixel region 11 below it. In another implementation manner, for example, when the pixel region 11 is a circular area, the boundary wall 221 can enclose a barrel-shaped collimation channel 2211. The diameter of the barrel-shaped collimation channel 2211 is the same as or substantially consistent with the diameter of the pixel region 11. In other implementation manners, the radial cross-section of the collimation channel 2211 is the same as the shape and dimension of the pixel region 11.

[0054] The inner wall 222 is disposed within the collimation channel 2211 surrounded by the boundary wall 221.

[0055] It should be noted that the higher the height of the boundary wall 221, the better the effect of the collimation frame in preventing crosstalk. However, an overly high boundary wall 221 will cause electrons that could originally bombard the corresponding pixel region 11 normally to be absorbed by the boundary wall 221 before reaching the pixel device layer 1, thereby causing a large amount of signal loss in the active pixel sensor and ultimately reducing the image quality.

[0056] In the embodiment of the present disclosure, by providing an inner wall 222 inside the boundary wall 221, the wall density of the collimation frame is increased, and electrons that deviate can be blocked and intercepted more effectively. Further, this design can reduce the height of the boundary wall 221. Ultimately, a balance point is found between the problem of reducing the boundary wall height and improving the collimation effect, that is, under the condition of reducing the height of the boundary wall 221, reducing signal loss and increasing the setting of the inner wall 222 to increase the wall density can still enable the collimation frame to maintain a good collimation effect. The technical solution of the present disclosure can overall reduce the thickness of the active pixel sensor, thereby making the product more miniaturized. Moreover, it can also ensure good filtering performance and the signal accuracy of image sensing.

[0057] In one example, the support portion 21 includes a support wall 211. The position of the support wall 211 corresponds to the position of the boundary wall 221.

[0058] For example, the positions of the support wall 211 and the boundary wall 221 correspond to each other. The final height of the collimation frame is the sum of the heights of the support wall 211 and the boundary wall 221. The corresponding positions of the support wall 211 and the boundary wall 221 can provide a good collimation effect for the suspended area between the inner wall 222 of the collimation frame and the pixel device layer 1, avoiding the problem of crosstalk caused by outgoing electrons jumping into other pixel regions 11.

[0059] The support portion 21 can be in the form of a wall to achieve the support function for the collimation portion 22. Being in the form of a wall can, on the one hand, better correspond to the boundary position of the pixel region 11, and on the other hand, better cooperate to achieve the collimation function and improve the signal accuracy of the image sensor. In other embodiments, other structures can also be used to achieve the support for the collimation portion.

[0060] In one example, a support wall 211 is formed between each boundary wall 221 and the pixel device layer 1.

[0061] For example, a support wall 211 is formed between each boundary wall 221 and the pixel device layer 1. Since the shape of each boundary wall 221 matches the shape of each pixel region 11, the support wall 211 located below each boundary wall 221 can combine with each boundary wall 221 to form a collimation channel with a longer length. This enables the support wall 211 to enclose the suspended area between the inner wall 222 of the collimation frame and the pixel device layer 1 to form an effective collimation effect, improving the collimation effect.

[0062] In one example, the support wall 211 and the boundary wall 221 are integrally formed.

[0063] For example, the integral formation of the support wall 211 and the boundary wall 221 can simplify and speed up the process of processing the collimation frame, facilitating the processing and use by the operator. In addition, the integral formation of the support wall 211 and the boundary wall 221 avoids the formation of burrs, depressions or protrusions at the connection between the support wall 211 and the boundary wall 221. These burrs, depressions or protrusions will change the movement direction of electrons, which is not conducive to the effective bombardment of electrons and will ultimately affect the image quality.

[0064] Of course, the support wall 211 and the boundary wall 221 can also be connected by other methods such as bonding and welding, which are not limited here, and those skilled in the art can choose according to actual needs.

[0065] In one example, the inner wall 222 includes a first inner wall 2221 and a second inner wall 2222. The first inner wall 2221 and the second inner wall 2222 are arranged at intervals. The first inner wall 2221 is closer to the boundary wall 221 than the second inner wall 2222.

[0066] For example, the number of inner walls 222 is also balanced between improving the collimation effect and reducing the signal loss to degrade the image quality. Too many inner walls 222, that is, too high a density of the inner walls 222, will also cause the electrons emitted by the photocathode 3 to be absorbed by the inner walls 222 before reaching the pixel device layer 1, ultimately resulting in excessive signal loss and reduced image quality. In this embodiment, the inner wall 222 includes a first inner wall 2221 and a second inner wall 2222. The appropriate density of the inner walls 222 enables a large amount of signal not to be lost while ensuring a good collimation effect, and thus can ensure good image quality.

[0067] In one example, the distance between the first inner wall 2221 and the boundary wall 221 is less than the distance between the first inner wall 2221 and the second inner wall 2222.

[0068] For example, as Figure 2As shown, the distance between the first inner wall 2221 and the boundary wall 221 is less than the distance between the first inner wall 2221 and the second inner wall 2222. This can make the tolerance of the first inner wall 2221 and the second inner wall 2222 to the lateral electron offset greater than that between the first inner wall 2221 and the boundary wall 221, avoiding many normal electrons (with relatively small lateral offsets) being blocked by the inner wall 222 before moving close to bombarding the pixel device layer 1, thereby reducing the image quality.

[0069] In one example, the first inner wall 2221 and the second inner wall 2222 are annularly distributed around the center of the collimation channel 2211. The first inner wall 2221 surrounds the second inner wall 2222. As Figure 2 shown, the first inner wall 2221 is located near the boundary wall 221 and forms a larger rectangular structure by surrounding. The second inner wall 2222 is located in the inner circle of the first inner wall 2221.

[0070] The radial dimension of the second inner wall 2222 is greater than the distance between the first inner wall 2221 and the second inner wall 2222.

[0071] The spacing between the first inner wall 2221 and the second inner wall 2222 is greater than the distance between the first inner wall 2221 and the boundary wall 221.

[0072] It should be noted that the larger the spacing, the higher the tolerance to the lateral offset of electrons; the smaller the spacing, the lower the tolerance to the lateral offset of electrons. Generally, the aperture of the inner wall 222 of the collimation part 22 corresponding to the center of the pixel device layer 1 is larger, and the tolerance to the lateral offset of electrons is higher, which can avoid many normal electrons (with relatively small lateral offsets) being blocked by the inner wall 222 before moving close to bombarding the pixel device layer 1, thereby unnecessarily losing more signals.

[0073] The aperture of the inner wall 222 of the collimation part 22 corresponding to the boundary of the pixel device layer 1 is smaller, and the tolerance to the lateral offset of electrons is lower, which can effectively prevent electrons from jumping into other pixel areas, thereby preventing the occurrence of crosstalk phenomena.

[0074] In the embodiments of the present disclosure, for example, as Figure 2As shown, the radial dimension of the second inner wall 2222 is greater than the spacing between the first inner wall 2221 and the second inner wall 2222. The spacing between the first inner wall 2221 and the second inner wall 2222 is greater than the spacing between the first inner wall 2221 and the boundary wall 221. In this way, in the collimation frame corresponding to a single pixel region 11, the spacing between the boundary wall 221, the first inner wall 2221, and the second inner wall 2222 increases step by step. On the premise of effectively collimating electrons with a large offset, it also avoids many electrons with a small lateral offset being blocked by the inner wall 222 before moving close to the bombardment pixel device layer 1, ultimately achieving the purpose of obtaining more signals and improving the image quality.

[0075] In one example, the collimation portion 22 further has a connecting wall 223. The connecting wall 223 is configured to connect and fix the inner wall 222 to the boundary wall 221. For the fixation and support of the inner wall structure itself, a connecting wall can be used to connect the inner wall to the boundary wall, thereby realizing the fixation of the inner wall itself.

[0076] For example, the connecting wall 223 can connect the inner wall 222 and the boundary wall 221, enabling the inner wall 222 to be stably connected to the boundary wall 221. As Figure 2 shown, between the first inner wall 2221 and the boundary wall 221, a connecting wall can be provided. Further, between the first inner wall and the second inner wall, a connecting wall is also provided, enabling the second inner wall to be connected to the boundary wall through the connecting wall and the first inner wall. This design ensures a good collimation effect and avoids the problem of collimation failure caused by the shaking or falling off of the inner wall 222.

[0077] In one example, in the collimation channel 2211, the connecting wall 223 and the inner wall 222 and / or the boundary wall 221 together enclose a plurality of sub-channels.

[0078] For example, the plurality of sub-channels can collimate electrons in multiple directions, avoiding the phenomenon of crosstalk caused by electrons jumping into other pixel regions 11.

[0079] In one example, the connecting wall 223 and the boundary wall 221 and the first inner wall 2221 enclose a plurality of first sub-channels 2231.

[0080] The connecting wall 223 and the first inner wall 2221 and the second inner wall 2222 enclose a plurality of second sub-channels 2232.

[0081] The radial dimension of the second sub-channel 2232 is greater than the radial dimension of the first sub-channel 2231.

[0082] The radial dimension of the second sub-channel 2232 is larger than that of the first sub-channel 2231. This enables the second sub-channel 2232 to have a greater tolerance for lateral electron displacement than the first sub-channel 2231, preventing many normal (less laterally displaced) electrons from being blocked by the inner wall 222 before reaching near the bombarding pixel device layer 1, thereby reducing the image quality. In contrast, the first sub-channel is located at the edge of the entire collimation channel. When electrons corresponding to other pixel regions deviate to the position corresponding to the current pixel region, they are more likely to appear at the edge of the collimation channel. Therefore, the smaller radial dimension of the first sub-channel is more conducive to intercepting electrons that deviate from other regions into this region, and also helps to intercept electrons located at the boundary position in this region and having a tendency to deviate outward.

[0083] In one example, the second inner wall 2222 is annularly distributed by itself, surrounding to form a third sub-channel 2233. The radial dimension of the third sub-channel 2233 is larger than that of the second sub-channel 2232.

[0084] It should be noted that the larger the radial dimension of the sub-channel, the higher the tolerance for lateral electron displacement; the smaller the radial dimension of the sub-channel, the lower the tolerance for lateral electron displacement. Generally, when electrons are emitted from the center of the pixel region 11 corresponding to the photocathode 3, even if they have a certain initial lateral velocity, they are likely to fall into the predetermined pixel region 11. When electrons are emitted from the edge of the pixel region 11 corresponding to the photocathode 3, if they have a certain initial lateral velocity, the probability of falling into a non-predetermined pixel region 11 is relatively large. Therefore, by setting the radial dimensions of the first sub-channel 2231, the second sub-channel 2232, and the third sub-channel 2233 to increase gradually, the first emitted electrons 301 at the center of the pixel region 11 corresponding to the photocathode 3 have a higher tolerance for lateral displacement, while the second emitted electrons 302 at the edge of the pixel region 11 corresponding to the photocathode 3 have a lower tolerance for lateral displacement.

[0085] In the embodiment of the present disclosure, the structure surrounded by the second inner wall 2222 is located in the inner circle of the structure surrounded by the first inner wall 2221, and it is used to form a rectangular third sub-channel 2233 in the central region corresponding to the pixel region 1. The radial dimension of the third sub-channel 2233 is larger than that of the second sub-channel 2232 surrounded by the first inner wall, the second inner wall, and the connecting wall. This enables the radial dimensions of the first sub-channel 2231, the second sub-channel 2232, and the third sub-channel 2233 to increase gradually in the collimation frame corresponding to a single pixel region 11. On the premise of effectively collimating electrons with a large displacement amount, it also prevents many electrons with a small lateral displacement from being blocked by the inner wall 222 before reaching near the bombarding pixel device layer 1, ultimately achieving the purpose of obtaining more signals and improving the image quality.

[0086] In one example, the ratio of the height of the collimation frame to the radial dimension of the pixel region 11 ranges from 1.5 to 4.

[0087] For example, the height of the collimation frame is the sum of the heights of the support wall 211 and the boundary wall 221. The ratio of the height of the collimation frame to the radial dimension of the pixel region 11 ranges from 1.5 to 4. This range of the dimension ratio enables the collimation frame to still achieve a good collimation effect without a large loss of signals, ultimately improving the image quality.

[0088] Preferably, the ratio of the height of the collimation frame to the radial dimension of the pixel region 11 is 2. Under this ratio characteristic, the collimation frame provided by this solution achieves an optimized effect. Compared with the embodiments shown in Figure 1 and Figure 2 , the collimation frame can achieve a good collimation effect and effectively reduce the overall thickness of the image sensor.

[0089] According to another embodiment of the present disclosure, a processing method of an active pixel sensor is provided. The processing method includes:

[0090] Providing a pixel device layer 1 having a plurality of pixel regions 11.

[0091] Depositing a first substrate layer 4 on the pixel device layer 1 and etching the first substrate layer 4 to form a support portion 21.

[0092] Depositing a sacrificial layer 6 around the support portion 21.

[0093] Depositing a second substrate layer 5 on the support portion 21 and the sacrificial layer and etching the second substrate layer 5 to form a collimation portion 22.

[0094] Releasing the sacrificial layer 6.

[0095] For example, as shown in Figures 5 - 10 , depositing a first substrate layer 4 on the pixel device layer 1, thinning the first substrate layer 4 to the height of the support wall 211, and etching the first substrate layer 4 to form a support portion 21.

[0096] Depositing a sacrificial layer 6 around the support portion 21. The material of the sacrificial layer 6 includes but is not limited to polyimide (PI) and phosphosilicate glass (PSG). The height of the sacrificial layer 6 is the same as the height of the support portion 21 and is used to support the collimation layer.

[0097] Depositing a second substrate layer 5 on the support portion 21 and the sacrificial layer and etching the second substrate layer 5 to form a collimation portion 22. The material of the collimation portion 22 includes but is not limited to Si3N4, SiO2, and SiON.

[0098] Releasing the sacrificial layer 6, and finally forming a complete collimation frame on the pixel device layer 1.

[0099] In one example, when etching the first substrate layer 4, a strip-shaped mask is provided at the edge corresponding to the pixel region 11, and the first substrate layer 4 is etched to form a support wall 211.

[0100] When etching the second substrate layer 5, a strip-shaped mask is provided at the position corresponding to the support wall 211. The thickness of the strip-shaped mask is the same as that of the support wall 211. The second substrate layer 5 is etched to form a boundary wall 221, such that the thickness of the boundary wall 221 is the same as that of the support wall 211.

[0101] In one example, when etching the second substrate layer 5, at the position corresponding to the pixel region 11, strip-shaped masks distributed crosswise are provided on the second substrate layer 5, and crosswise distributed inner walls 222 are etched.

[0102] In the embodiments of the present disclosure, a collimation frame is prepared on the pixel device layer 1 through a MEMS process. The collimation part 22 of the collimation frame has inner walls 222 and a boundary wall 221. The double walls perform a collimation operation on the electrons emitted by the photocathode 3, such that the electrons can successfully and effectively fall into the predetermined pixel region 11, avoiding the crosstalk phenomenon caused by the electrons falling into other pixel regions 11, and finally achieving the purpose of improving the image quality.

[0103] In the above embodiments, the differences between the embodiments are mainly described. As long as the different optimization features between the embodiments are not contradictory, they can be combined to form a more optimal embodiment. For the sake of brevity of the description, they will not be elaborated herein.

[0104] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. An active pixel sensor, characterized in that , including: a pixel device layer having a plurality of pixel regions; a collimation frame having a support portion and a collimation portion, the support portion being disposed on the pixel device layer, and the collimation portion being disposed on the support portion; the collimation portion has a boundary wall and an inner wall, the boundary wall encloses a plurality of collimation channels, each collimation channel corresponding to the position of each pixel region one by one, the inner wall being disposed in the collimation channel surrounded by the boundary wall, and the radial dimension of the collimation channel matching the dimension of the pixel region; the collimation portion is configured to guide electrons to fall on the corresponding pixel region.

2. The active pixel sensor according to claim 1, characterized in that the support portion includes a support wall, and the position of the support wall corresponds to the position of the boundary wall.

3. The active pixel sensor according to claim 2, characterized in that, a support wall is formed between each boundary wall and the pixel device layer.

4. The active pixel sensor according to claim 2, characterized in that, the support wall and the boundary wall are integrally formed.

5. The active pixel sensor according to claim 1, characterized in that, the inner wall includes a first inner wall and a second inner wall, the first inner wall and the second inner wall are spaced apart, and the first inner wall is closer to the boundary wall than the second inner wall.

6. The active pixel sensor according to claim 5, wherein the distance between the first inner wall and the boundary wall is less than the distance between the first inner wall and the second inner wall.

7. The active pixel sensor according to claim 5, wherein the first inner wall and the second inner wall are annularly distributed around the center of the collimation channel, and the first inner wall surrounds the second inner wall; the radial dimension of the second inner wall is greater than the distance between the first inner wall and the second inner wall; the spacing between the first inner wall and the second inner wall is greater than the distance between the first inner wall and the boundary wall.

8. The active pixel sensor according to claim 5, characterized in that, the collimation portion further has a connecting wall configured to connect and fix the inner wall to the boundary wall.

9. The active pixel sensor according to claim 8, wherein in the collimation channel, the connecting wall and the inner wall and / or the boundary wall together enclose a plurality of sub-channels.

10. The active pixel sensor according to claim 8, characterized in that, the connecting wall and the boundary wall and the first inner wall enclose a plurality of first sub-channels; the connecting wall and the first inner wall and the second inner wall enclose a plurality of second sub-channels; the radial dimension of the second sub-channel is greater than the radial dimension of the first sub-channel.

11. The active pixel sensor according to claim 10, characterized in that, the second inner wall is annularly distributed by itself, surrounding and forming a third sub-channel, and the radial dimension of the third sub-channel is greater than the radial dimension of the second sub-channel.

12. The active pixel sensor according to claim 1, wherein the ratio of the height of the collimation frame to the radial dimension of the pixel region ranges from 1.5 to 4.

13. The active pixel sensor according to claim 12, wherein the ratio of the height of the collimation frame to the radial dimension of the pixel region is 2.

14. A method for manufacturing the active pixel sensor according to any one of claims 1 to 13, characterized in that, including: providing a pixel device layer having a plurality of pixel regions; depositing a first substrate layer on the pixel device layer and etching the first substrate layer to form a support portion; depositing a sacrificial layer around the support portion; depositing a second substrate layer on the support portion and the sacrificial layer and etching the second substrate layer to form a collimation portion; releasing the sacrificial layer.

15. The processing method according to claim 14, wherein when etching the first substrate layer, a strip-shaped mask is disposed at the edge corresponding to the pixel region, and the first substrate layer is etched to form a support wall; When etching the second liner layer, a strip-shaped mask is disposed at a position corresponding to the support wall, the thickness of the strip-shaped mask is consistent with the thickness of the support wall, and the second liner layer is etched to form a boundary wall, so that the thickness of the boundary wall is consistent with the thickness of the support wall.

16. The processing method according to claim 14, wherein When etching the second liner layer, at a position corresponding to the pixel region, strip-shaped masks are disposed on the second liner layer in a cross distribution, and inner walls in a cross distribution are etched.

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