WO2022170570A1

WO2022170570A1 - Dual charge-focusing single photon avalanche diode (spad) image sensor

Info

Publication number: WO2022170570A1
Application number: PCT/CN2021/076549
Authority: WO
Inventors: Chiehwei LIAO
Original assignee: Diensens Technology
Priority date: 2021-02-10
Filing date: 2021-02-10
Publication date: 2022-08-18

Abstract

The present disclosure provides a single photon avalanche diode (SPAD) that is suitable for use in SPAD image sensors. The SPAD (100) includes a micro lens (102), a sensor wafer (103), a backside illuminated deep trench isolation (BSI-DTI) region (104), a subsidiary deep trench isolation (SUB DTI) pillar (105), one or more deep trench isolation (DTI) regions (106), one or more first doping regions (107), one or more second doping regions (108), one or more third doping regions (109), a circuit wafer (110), one or more fourth doping regions (111), and one or more fifth doping regions (113). The existence of the one or more second doping regions (108) "craters" the equipotential lines of the regions, causing higher voltage gradients, and thus resulting in stronger electrical fields in some regions of the one or more first doping regions (107).

Description

DUAL CHARGE-FOCUSING SINGLE PHOTON AVALANCHE DIODE (SPAD) IMAGE SENSOR

FIELD OF TECHNOLOGY

The present invention generally relates to an image sensor, in particular, to a backside illuminated single photon avalanche diode image sensor.

BACKGROUND

An image sensor is a device that converts optical images into electronic signals and is widely used in digital cameras and other electronic optical devices. Image sensors with a backside illuminated (BSI) single photon avalanche diode (SPAD) are gaining popularity in recent years, because of the low-noise and picosecond timing resolution they offer.

An avalanche photodiode (APD) is a semiconductor photo-detector whose principle is similar to a photomultiplier tube. After a higher reverse bias voltage (usually 100-200 V in silicon materials) is applied to the APD, an internal current gain of about 100 can be obtained in the APD by using theavalanche breakdowneffect. In comparison, an SPAD is biased well above its reverse-bias breakdown voltage and has a structure that allows operation without damage or undue noise. At this bias, the electric field within the SPAD is so highthat a single photon can trigger a self-sustaining avalanche; hence the name.

But SPAD” sapplications are limited by device characteristics such as small active area, and poor photon absorption.

SUMMARY

The present disclosure provides a single photon avalanche diode (SPAD) that is suitable for use in SPAD image sensors. The SPAD includes a micro lens, a sensor wafer, a backside illuminated deep trench isolation (BSI-DTI) region, a subsidiary deep trench isolation (SUB DTI) pillar, one or more deep trench isolation (DTI) regions, one or more first doping regions, one or more second doping regions, one or more third doping regions, a circuit wafer, one or more fourth doping regions, and one or more fifth doping regions. The existence of the one or more second doping regions “craters” the equipotential lines of the regions, causing higher voltage gradients, and thus resulting in stronger electrical fields in some regions of the one or more first doping regions.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 depicts a cross-sectional view of a first exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 2 shows further details of the first exemplary SPAD depicted in Fig. 1.

Fig. 3 depicts a cross-sectional view of a second exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 4 depicts a cross-sectional view of a third exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 5 depicts a cross-sectional view of a fourth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 6 depicts a cross-sectional view of a fifth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 7 depicts a cross-sectional view of a sixth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 8 depicts a cross-sectional view of a seventh exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 9 depicts a cross-sectional view of an eighth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 10 depicts a cross-sectional view of a ninth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 11 depicts a cross-sectional view of a tenth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 12 depicts a cross-sectional view of a eleventh exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 13 depicts a cross-sectional view of a twelfth exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 14 depicts a top view of an SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

Fig. 15 depicts a bottom view of an SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques, and are not intended to limit aspects of the presently disclosed invention. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made to achieve the developers' specific goals, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

Within this document, terms such as "above" , "on” , “below” , “top” , “bottom” , “horizontally” and “vertically” should be construed with reference to the single photon avalanche diodes illustrated in the figures. In particular, a horizontal direction runs parallel to a sensor wafer, and a vertical direction runs perpendicularly in and out of the sensor wafer, with “down” leading to the sensor wafer and “up” leading to the surface, or “top” of the diode. Within this document, when a first element is positioned “above” or "on" a second element, the first element may either be directly on the top of the second element, or there might be additional elements in between the first and the second elements.

It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms, such as “above” , “on” , “below” , “top” , “bottom” , “horizontally” and “vertically” , are intended to include different orientations during use and operation. For example, if the device in the figures is rotated, then what is described as “below” or “beneath” or “under” may become “on” or “above” or “over. ” Thus, the term “below” and “under” may include both upper and lower orientations. Device may additionally be oriented differently (e.g., rotated 90 degrees or other orientations) , and the spatial relationship used in this description are interpreted accordingly.

Fig. 1 depicts a cross-sectional view of a first exemplary single photon avalanche diode (SPAD) 100 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. The first exemplary SPAD 100 includes a micro lens 102, a sensor wafer 103, a backside illuminated deep trench isolation (BSI-DTI) region 104, a subsidiary deep trench isolation (SUB DTI) pillar 105, one or more deep trench isolation (DTI) regions 106, one or more first doping regions 107, one or more second doping regions 108, one or more third doping regions 109, a circuit wafer 110, one or more fourth doping regions 111, and one or more fifth doping regions 113. The SPAD 100 may be cube-shaped or cylinder-shaped, and the cross-sectional view shows the internal of the SPAD 100 by vertically cutting through its center.

The micro lens 102 is connected to a bottom surface of the sensor wafer 103. A radiation source 101 is represented by an arrow 112. A semiconductor region is positioned above the sensor wafer 103, and in contact with a top surface of the sensor wafer 103. In other words, the semiconductor region may be deemed a SPAD sensing unit, and one or more of these SPAD sensing units may be arranged in rows and columns between the sensor wafer 103 and the circuit wafer 110.

The semiconductor region includes the BSI-DTI region 104, the SUB DTI pillar 105, the one or more DTI regions 106, the one or more first doping regions 107, the one or more second doping regions 108, the one or more third doping regions 109, the one or more fourth doping regions 111, and the one or more fifth doping regions 113. The circuit wafer 110 is positioned above the one or more DTI regions 106, the one or more second doping regions 108, and the one or more fifth doping regions 113. The circuit wafer 110 is also connected to a readout circuit. The circuit wafer 110 and the sensor wafer 103 are further connected through bonded pads. As shown in Fig. 1, part of the semiconductor region extends through the circuit wafer 110. In some embodiments, the semiconductor region is positioned entirely below the circuit wafer 110.

The one or more second doping regions 108, together with the one or more third doping regions 109 and the one or more fifth doping regions 113, divide the one or more first doping regions 107 into multiple parts in various embodiments as shown below. In some embodiments as shown in Fig. 1, the one or more first doping regions 107 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is adjacent to the BSI-DTI region 104 and includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 108, the one or more third doping regions 109 and the one or more fifth doping regions 113. In some embodiments, the one or more third doping regions 109 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 1, the cross sections of the protruding portion and the one or more third doping regions 109 are substantially aligned in the vertical direction.

In some embodiments, a channel/tunnel may be constructed in the first doping regions 107. The channel/tunnel may be vertically extended from the top surface of the BSI-DTI 104 to the bottom surface of the fifth doping regions 113, and may be located in the center area of the semiconductor region. The channel/tunnel may be filled with DTI, filling material, and/or a type of dopant that is different from the first doping regions 107. In Fig. 1’s embodiment, the channel/tunnel may be filled with SUB DTI 105 and the second doping regions 108.

The BSI-DTI region 104 is positioned above the sensor wafer 103. The SUB DTI pillar 105 and the one or more DTI regions 106 are positioned above the BSI-DTI region 104. The SUB DTI pillar 105 extends from the BSI-DTI region 104 to the one or more second doping regions 108. The one or more DTI regions 106 are positioned adjacent to and around the one or more first doping regions 107 and the one or more fifth doping regions 113. The one or more DTI regions 106 also extend from the BSI-DTI region 104 to the circuit wafer 110. The one or more first doping regions 107 are positioned above the BSI-DTI region 104, and around the SUB DTI pillar 105 and the one or more second doping regions 108. The one or more first doping regions 107 are also positioned below and around the one or more third doping regions 109.

The one or more second doping regions 108 are positioned above the SUB DTI pillar 105 and below a part of the one or more first doping regions 107. The one or more third doping regions 109 are surrounded by parts of the one or more first doping regions 107 and are also positioned above a part of the one or more first doping regions 107. The one or more fourth doping regions 111 are positioned above the one or more fifth doping regions 113. In some embodiments, the lower parts of the one or more fourth doping regions 111 are positioned between a part of the one or more first doping regions 107 and one of the one or more DTI regions 106; the upper parts of the one or more fourth doping regions 111 extend above the one or more DTI regions 106.

In operation, a reverse bias voltage above the breakdown voltage of the SPAD 100 is applied to the exemplary SPAD 100. Whenthe radiation source 101 (e.g., a beam of light) illuminates the first exemplary SPAD 100, self-sustaining avalanche pulses can be created from charge carriers which were in turn generated by photons striking the semiconductor region. Specifically, the reverse bias voltage above the breakdown voltage of the SPAD 100 is applied to the one or more fourth doping regions 111. Specifically, the photons first travel through the micro lens 102 before reaching the sensor wafer 103; then the photons enter the semiconductor region and generate the charge carriers by electron-hole creation; the charge carriers are then guided by the differently doped regions of the semiconductor region through a depletion region of the semiconductor region, and trigger an avalanche breakdown. The avalanche is quenched when the bias voltage is lowered down to, or below, the breakdown voltage of the SPAD 100.

Specifically, the SUB DTI pillar 105, combined with the one or more first doping regions 107, the one or more second doping regions 108, and the one or more fifth doping regions 113, guides the charge carriers toward parts of the one or more first doping regions 107 just below the one or more third doping regions 109, and then the charge carriers are pumped to the readout circuit to generate corresponding signal (s) . It is worth noting that, with a reverse bias voltage above the breakdown voltage of the SPAD 100, a single charge carrier injected into the depletion region can trigger a self-sustaining avalanche.

More specifically, the existence of the one or more second doping regions 108 “craters” the equipotential lines of the semiconductor region, causing higher voltage gradients, and thus resulting in stronger electrical fields in the regions of the one or more first doping regions 107 that are close to and below the one or more third doping regions 109; the charge carriers in the regions of the one or more first doping regions 107 below the one or more third doping regions 109 are then pumped from the one or more first doping regions 107 to the one or more third doping regions 109, and then to the readout circuit. In some embodiments, the one or more first doping regions 107 and the one or more third doping regions 109 are doped with the same dopant, but the latter is more heavily doped.

In operation, the BSI-DTI region 104 acts as a light shield to reduce incoming photons propagating outside the semiconductor region and thereby increases the photon absorption probability (PAP) of the exemplary SPAD 100. Specially, the BSI-DTI region 104 can reflect photons to keep them in the semiconductor region. In addition, the one or more DTI regions 106 can reduce optical and electrical crosstalk between neighboring SPADs. In some embodiments, the circuit wafer 110 includes one or more voltage supplies, and at least one of the one or more voltage supplies can provide a voltage higher than the breakdown voltage of the first exemplary SPAD 100.

In some embodiments, as shown in Fig. 1, the one or more first doping regions 107 are doped with n type dopants, the one or more second doping regions 108 are doped with p type dopants, the one or more third doping regions 109 are doped with n type dopants, the one or more fourth doping regions 111 are doped with p type dopants, and the one or more fifth doping regions 113 are doped with p type dopants. In some embodiments, the one or more third doping regions 109 are more heavily doped than the one or more first doping regions 107, and the one or more fourth doping regions 111 are more heavily doped than the one or more second doping regions 108 and the one or more fifth doping regions 113. In some embodiments, the one or more third doping regions 109 are less heavily doped than the one or more first doping regions 107, and the one or more fourth doping regions 111 are less heavily doped than the one or more second doping regions 108 and the one or more fifth doping regions 113.

In some embodiments, the one or more first doping regions 107 are doped with p type dopants, the one or more second doping regions 108 are doped with n type dopants, the one or more third doping regions 109 are doped with p type dopants, the one or more fourth doping regions 111 are doped with n type dopants, and the one or more fifth doping regions 113 are doped with n type dopants. In some embodiments, the one or more third doping regions 109 are more heavily doped than the one or more first doping regions 107, and the one or more fourth doping regions 111 are more heavily doped than the one or more second doping regions 108 and the one or more fifth doping regions 113. In some embodiments, the one or more third doping regions 109 are less heavily doped than the one or more first doping regions 107, and the one or more fourth doping regions 111 are less heavily doped than the one or more second doping regions 108 and the one or more fifth doping regions 113.

In some embodiments, there is a color filter between the micro lens 102 and the sensor wafer 103. In some embodiments, the color filter is a RGB filter. In some embodiments, the filter is an infrared cut-off filter. The infrared cut-off filter can be a 940 nm infrared cut-off filter, a 905 nm infrared cut-off filter, or an 850 nm infrared cut-off filter.

In some embodiments, the one or more second doping regions 108 are in direct contact with the SUB DTI pillar 105; in some other embodiments, the one or more second doping regions 108 are not in direct contact with the SUB DTI pillar 105. In other words, additional filling material may be added between the doping pillar which is a part of the second doping regions 108 and the SUB STI pillar 105. In some embodiments, the one or more first doping regions 107 separates a bottom surface of the one or more second doping regions 108 from a top surface of the SUB DTI pillar 105.

In some embodiments, as shown in Fig. 1, the one or more first doping regions 107 are positioned below and around the one or more third doping regions 109. In some other embodiments, the one or more first doping regions 107 are positioned entirely below the one or more third doping regions 109.

In some embodiments, the one or more second doping regions 108 have a “T” shaped cross section, as shown in Fig. 1, and the one or more second doping regions 108 consist of a horizontal portion and a vertical portion. In some embodiments, the one or more second doping regions 108 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 108 have a circular cross section. In some embodiments, the one or more second doping regions 108 have an elliptical cross section. In some embodiments, the one or more second doping regions 108 have a rectangular or hexagon cross section. In some embodiments, the one or more second doping regions 108 have a triangular cross section. In some embodiments, the one or more second doping regions 108 have an irregularly shaped cross section.

In some embodiments, the one or more third doping regions 109 have a rectangular cross section, as shown in Fig. 1. In some embodiments, the one or more second doping regions 108 have an “I” shaped cross section. In some embodiments, the one or more third doping regions 109 have a circular cross section. In some embodiments, the one or more third doping regions 109 have an elliptical cross section. In some embodiments, the one or more third doping regions 109 have a rectangular or hexagon cross section. In some embodiments, the one or more third doping regions 109 have a triangular cross section. In some embodiments, the one or more third doping regions 109 have an irregularly shaped cross section.

In some embodiments, the one or more fourth doping regions 111 have a rectangular cross section, as shown in Fig. 1. In some embodiments, the one or more second doping regions 108 have an “I” shaped cross section. In some embodiments, the one or more fourth doping regions 111 have a circular cross section. In some embodiments, the one or more fourth doping regions 111 have an elliptical cross section. In some embodiments, the one or more fourth doping regions 111 have a rectangular cross section. In some embodiments, the one or more fourth doping regions 111 have a triangular cross section. In some embodiments, the one or more fourth doping regions 111 have an irregularly shaped cross section.

In some embodiments, the one or more fifth doping regions 113 have a rectangular cross section, as shown in Fig. 1. In some embodiments, the one or more second doping regions 108 have an “I” shaped cross section. In some embodiments, the one or more fifth doping regions 113 have a circular cross section. In some embodiments, the one or more fifth doping regions 113 have an elliptical cross section. In some embodiments, the one or more fifth doping regions 113 have a rectangular cross section. In some embodiments, the one or more fifth doping regions 113 have a triangular cross section. In some embodiments, the one or more fifth doping regions 113 have an irregularly shaped cross section.

In some embodiments, the BSI-DTI region 104, the SUB DTI pillar 105 and the one or more DTI regions 106 are made of one or more of insulating materials. In some embodiments, the BSI-DTI region 104, the SUB DTI pillar 105 and the one or more DTI regions 106 are made of one or more of high-κ dielectric materials. In some embodiments, the BSI-DTI region 104, the SUB DTI pillar 105 and the one or more DTI regions 106 are made of one or more of materials including silicon dioxide (SiO ₂) , poly-silicon and other dielectric material. In some embodiments, the BSI-DTI region 104, the SUB DTI pillar 105 and the one or more DTI regions 106 are made of the same material (s) . In some embodiments, the BSI-DTI region 104, the SUB DTI pillar 105 and the one or more DTI regions 106 have different compositions.

The circuit wafer 110 and sensor wafer 103 can be made of any suitable material. In some embodiments, the circuit wafer 110 and sensor wafer 103are made of one or more of silicon, germanium, silicon-insulator-silicon, silicon on sapphire, and doped and un-doped semiconductors.

In some embodiments, the BSI-SPAD sensing unit can also be applicable to a front side illuminated (FSI) configuration. Specifically, thelens in the SPAD may be positioned on top of the device. Accordingly, the device’s front side, instead of back side, is illumined when in operation.

Fig. 2 shows further details of an embodiment of the first exemplary SPAD 100 depicted in Fig. 1. As mentioned above, the first exemplary SPAD 100 includes the micro lens 102, the sensor wafer 103, the BSI-DTI region 104, the SUB DTI pillar 105, the one or more DTI regions 106, the one or more first doping regions 107, the one or more second doping regions 108, the one or more third doping regions 109, the circuit wafer 110, the one or more fourth doping regions 111, and the one or more fifth doping regions 113.

In some embodiments, as shown in Fig. 2, the shortest distance between the sensor wafer 103 and the circuit wafer 110 is D, the shortest distance between a top surface of the one or more fifth doping regions 113 and a bottom surface of the circuit wafer 110 is D1, the one or more fifth doping regions 113 have a depth of D2, the horizontal portion of the one or more second doping regions 108 has a depth of D2, the vertical portion of the one or more second doping regions 108 has a depth of D3, the SUB DTI pillar 105 has a height of D4, and the shortest distance between a bottom surface of the one or more fifth doping regions 113 and a top surface of the BSI-DTI region 104 is D5.

In some embodiments, as shown in Fig. 2, the sum of D3 and D4 equals or substantially equals D5, and when D3 is larger D4 is smaller accordingly; In some other embodiments, the sum of D3 and D4 is smaller than D5, and there is a gap between the one or more second doping regions 108 and the SUB DTI pillar 105. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 107 are made of. The sum of D3 and D4 ranges from 1 micrometer to 20 micrometers. The ratio of D3 to D4 can be adjusted as needed.

In some embodiments, as shown in Fig. 2, the shortest distance between the one or more third doping regions 109 and the one or more DTI regions 106 is X1, the shortest distance between the one or more second doping regions 108 and the one or more fifth doping regions 113 is X2, and the horizontal portion of the one or more second doping regions 108 has a width of X3. The vertical portion of the one or more second doping regions x08 has a width of X3 -2XF, as shown in Fig. 2.

In some embodiments, as shown in Fig. 2, the first exemplary SPAD 100 is at least mirror symmetric, with its plane of symmetry cutting through the SUB DTI pillar 105 and perpendicular to the wafers. In some embodiments, the first exemplary SPAD 100 has discrete rotational symmetry, with its axis passing through the SUB DTI pillar 105 andperpendicular to the wafers. In some embodiments, the first exemplary SPAD 100 is not symmetric.

Fig. 3 depicts a cross-sectional view of a second exemplary SPAD 300 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 3 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The second exemplary SPAD 300 includes a micro lens 302, a sensor wafer 303, a BSI-DTI region 104, a SUB DTI pillar 305, one or more DTI regions 306, one or more first doping regions 307, one or more second doping regions 308, one or more third doping regions 309, a circuit wafer 310, one or more fourth doping regions 311, and one or more fifth doping regions 313. A radiation source 301 is represented by an arrow 312.

In some embodiments, as shown in Fig. 3, the one or more first doping regions 307 are divided into three parts; the three parts include two upper parts and one lower part; the lower part includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 308, the one or more third doping regions 309 and the one or more fifth doping regions 313. In some embodiments, the one or more third doping regions 309 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 3, the cross sections of the protruding portion and the one or more third doping regions 309 are substantially aligned in the vertical direction.

The BSI-DTI region 304 is positioned above the sensor wafer 303. The SUB DTI pillar 305 and the one or more DTI regions 306 are positioned above the BSI-DTI region 304. The SUB DTI pillar 305 extends upwards from the BSI-DTI region 304, and inside the one or more second doping regions 308. The one or more DTI regions 306 are positioned around the one or more first doping regions 307 and the one or more fifth doping regions 313. The one or more DTI regions 306 also extend from the BSI-DTI region 304 to the circuit wafer 310. The one or more first doping regions 307 are positioned above lower parts of the one or more fifth doping regions 313, which are above the BSI-DTI region 304. The one or more first doping regions 307 are also positioned around the SUB DTI pillar 305 and the one or more second doping regions 308. The one or more first doping regions 307 are also positioned below and around the one or more third doping regions 309.

The one or more second doping regions 308 are positioned above and around and the SUB DTI pillar 305, and below a part of the one or more first doping regions 307. The one or more third doping regions 309 are surrounded by parts of the one or more first doping regions 307 and are also positioned above a part of the one or more first doping regions 307. The one or more fourth doping regions 311 are positioned above the one or more fifth doping regions 313. In some embodiments, the lower parts of the one or more fourth doping regions 311 are positioned between a part of the one or more first doping regions 307 and one of the one or more DTI regions 306; the upper parts of the one or more fourth doping regions 311 extend above the one or more DTI regions 306.

the SUB DTI pillar 305, combined with the one or more first doping regions 307, the one or more second doping regions 308, and the one or more fifth doping regions 313, guides the charge carriers toward parts of the one or more first doping regions 307 just below the one or more third doping regions 309, and then the charge carriers are pumped to the readout circuit to generate corresponding signal (s) .

In some embodiments, as shown in Fig. 3, the one or more first doping regions 307 are positioned below and around the one or more third doping regions 309. In some other embodiments, the one or more first doping regions 307 are positioned entirely below the one or more third doping regions 309.

In some embodiments, the one or more second doping regions 308 have a “π” shaped cross section, as shown in Fig. 3, and the one or more second doping regions 308 consist of a horizontal portion and a vertical portion. The vertical portion further includes an upper portion and a lower portion, the upper portion has a rectangular cross section, and the lower portion encapsulates the SUB DTI pillar 305.

In some embodiments, as shown in Fig. 3, the one or more fifth doping regions 313 have an upper horizontal portion, a vertical portion and a lower horizontal portion. The upper horizontal portion of the one or more fifth doping regions 313 has substantially the same cross section as the one or more fifth doping regions 313 of the first exemplary SPAD 100. The vertical portion is formed between the lower part of the one or more first doping regions 307 and the one or more DTI regions 306, and extends from the BSI-DTI region 304 to the upper horizontal portion. The lower horizontal portion is formed above the BSI-DTI region 304 and below the lower part of the one or more first doping regions 307. Similar to the function of the one or more second doping regions 308, as discussed above, the vertical portion and the lower horizontal portion of the one or more fifth doping regions 313 create stronger electrical fields around them, which aids photons striking sides or edges of the semiconductor region in triggering avalanches.

The doping regions 313 may be deemed a layer of dopant to surround the exterior surfaces of the first doping regions 307, or a layer of dopant to surround the interior surfaces of the DTI regions (including BSI-DTI 304, SUB DTI 305, and DTI 306) as well as the exterior surface of the P type dopant pillar 308.

In some embodiments, as shown in Fig. 3, the shortest distance between the sensor wafer 303 and the circuit wafer 310 is D, the shortest distance between a top surface of the one or more fifth doping regions 313 and a bottom surface of the circuit wafer 310 is D1, the one or more fifth doping regions 313 have a depth of D2, the horizontal portion of the one or more second doping regions 308 has a depth of D2, the upper portion of the vertical portion of the one or more second doping regions 308 has a depth of D3, the SUB DTI pillar 305 has a height of D4, and the shortest distance between a bottom surface of the one or more fifth doping regions 313 and a top surface of the BSI-DTI region 304 is D5.

In some embodiments, as shown in Fig. 3, the sum of D3 and D4 equals or substantially equals D5, and when D3 is larger D4 is smaller accordingly; In some other embodiments, the sum of D3 and D4 is smaller than D5, and there is a gap between the one or more second doping regions 308 and the SUB DTI pillar 305. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 307 are made of. The sum of D3 and D4 ranges from 1 micrometer to 20 micrometers. The ratio of D3 to D4 can be adjusted as needed.

In some embodiments, as shown in Fig. 3, the shortest distance between the one or more third doping regions 309 and the one or more DTI regions 306 is aks1, the shortest distance between the one or more second doping regions 308 and the one or more fifth doping regions 313 is X2, and the horizontal portion of the one or more second doping regions 308 has a width of X3. The vertical portion of the one or more second doping regions 308 has a width of X3-2XF.

Fig. 4 depicts a cross-sectional view of a third exemplary SPAD 400 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 4 may correspond to their respective counterparts in Fig. 1, Fig. 3, and other figures, and may have substantially the same features and functionalities as described above.

The third exemplary SPAD 400 includes a micro lens 402, a sensor wafer 403, a BSI-DTI region 404, a SUB DTI pillar 405, one or more DTI regions 406, one or more first doping regions 407, one or more second doping regions 408, one or more third doping regions 409, a circuit wafer 410, one or more fourth doping regions 411, and one or more fifth doping regions 413. A radiation source 401 is represented by an arrow 412.

The one or more second doping regions 408, together with the one or more third doping regions 409 and the one or more fifth doping regions 413, divide the one or more first doping regions 407 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 4, the one or more first doping regions 407 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is adjacent to the BSI-DTI region 404 and includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 408, the one or more third doping regions 409 and the one or more fifth doping regions 413. In some embodiments, the one or more third doping regions 409 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 4, the cross sections of the protruding portion and the one or more third doping regions 409 are substantially aligned in the vertical direction.

The BSI-DTI region 404 is positioned above the sensor wafer 403. The SUB DTI pillar 405 and the one or more DTI regions 406 are positioned above the BSI-DTI region 404. The SUB DTI pillar 405 extends upwards from the BSI-DTI region 404 to the one or more second doping regions 408. The one or more DTI regions 406 are positioned adjacent to and around the one or more first doping regions 407 and the one or more fifth doping regions 413. The one or more DTI regions 406 also extend from the BSI-DTI region 404 to the circuit wafer 410. The one or more first doping regions 407 are positioned above the BSI-DTI region 404, and around the SUB DTI pillar 405 and the one or more second doping regions 408. The one or more first doping regions 407 are also positioned below and around the one or more third doping regions 409. The one or more second doping regions 408 are positioned above the SUB DTI pillar 405 and below a part of the one or more first doping regions 407.

The one or more third doping regions 409 are surrounded by parts of the one or more first doping regions 407 and are also positioned above a part of the one or more first doping regions 407. The one or more fourth doping regions 411 are positioned above the one or more fifth doping regions 413. In some embodiments, the lower parts of the one or more fourth doping regions 411 are positioned between a part of the one or more first doping regions 407 and one of the one or more DTI regions 406; the upper parts of the one or more fourth doping regions 411 extend above the one or more DTI regions 406.

In some embodiments, the one or more second doping regions 408 have a rectangular cross section, as shown in Fig. 4. In some embodiments, the one or more second doping regions 408 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 408 have a circular cross section. In some embodiments, the one or more second doping regions 408 have an elliptical cross section. In some embodiments, the one or more second doping regions 408 have a triangular cross section. In some embodiments, the one or more second doping regions 408 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 4, the shortest distance between the sensor wafer 403 and the circuit wafer 410 is D, the shortest distance between a top surface of the one or more fifth doping regions 413 and a bottom surface of the circuit wafer 410 is D1, the one or more fifth doping regions 413 have a depth of D2, the one or more second doping regions 408 has a depth of D2, the SUB DTI pillar 405 has a depth of D5, and the shortest distance between a bottom surface of the one or more fifth doping regions 413 and a top surface of the BSI-DTI region 404 is D5. In some other embodiments, there is a gap between the one or more second doping regions 508 and the SUB DTI pillar 505. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 507 are made of. D5 ranges from 1 micrometer to 20 micrometers.

In some embodiments, as shown in Fig. 4, the shortest distance between the one or more third doping regions 409 and the one or more DTI regions 406 is X1, the shortest distance between the one or more second doping regions 408 and the one or more fifth doping regions 413 is X2, and the one or more second doping regions 408 has a width of X3. The SUB DTI pillar 405 has a width of X3-2XF.

Fig. 5 depicts a cross-sectional view of a fourth exemplary SPAD 500 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 5 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The fourth exemplary SPAD 500 includes a micro lens 502, a sensor wafer 503, a BSI-DTI region 504, a SUB DTI pillar 505, one or more DTI regions 506, one or more first doping regions 507, one or more second doping regions 508, one or more third doping regions 509, a circuit wafer 510, one or more fourth doping regions 511, and one or more fifth doping regions 513. A radiation source 501 is represented by an arrow 512.

The one or more second doping regions 508, together with the one or more third doping regions 509 and the one or more fifth doping regions 513, divide the one or more first doping regions 507 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 5, the one or more first doping regions 507 are divided into three parts; the three parts include two upper parts and one lower part; the lower part includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 508, the one or more third doping regions 509 and the one or more fifth doping regions 513. In some embodiments, the one or more third doping regions 509 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 5, the cross sections of the protruding portion and the one or more third doping regions 509 are substantially aligned in the vertical direction.

The BSI-DTI region 504 is positioned above the sensor wafer 503. The SUB DTI pillar 505 and the one or more DTI regions 506 are positioned above the BSI-DTI region 504. The SUB DTI pillar 505 extends upwards from the BSI-DTI region 504 and inside the one or more second doping regions 308. The one or more DTI regions 306 are positioned around the one or more first doping regions 307 and the one or more fifth doping regions 313. The one or more DTI regions 306 also extend from the BSI-DTI region 304 to the circuit wafer 310. The one or more first doping regions 307 are positioned above lower parts of the one or more fifth doping regions 313, which are above the BSI-DTI region 304. The one or more first doping regions 307 are also positioned around the SUB DTI pillar 305 and the one or more second doping regions 308. The one or more first doping regions 307 are also positioned below and around the one or more third doping regions 309. The one or more second doping regions 308 are positioned above and around and the SUB DTI pillar 305, and below a part of the one or more first doping regions 307.

The one or more third doping regions 309 are surrounded by parts of the one or more first doping regions 307 and are also positioned above a part of the one or more first doping regions 307. The one or more fourth doping regions 311 are positioned above the one or more fifth doping regions 313. In some embodiments, the lower parts of the one or more fourth doping regions 311 are positioned between a part of the one or more first doping regions 307 and one of the one or more DTI regions 306; the upper parts of the one or more fourth doping regions 311 extend above the one or more DTI regions 306.

In some embodiments, the one or more second doping regions 508 have a “π” shaped cross section, as shown in Fig. 5, and the one or more second doping regions 508 consist of a horizontal portion and a vertical portion; the horizontal portion is positioned above the SUB DTI pillar 505, and the vertical portion is positioned around the SUB DTI pillar 505. In some embodiments, the one or more second doping regions 508 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 508 have a circular cross section. In some embodiments, the one or more second doping regions 508 have an elliptical cross section. In some embodiments, the one or more second doping regions 508 have a rectangular cross section. In some embodiments, the one or more second doping regions 508 have a triangular cross section. In some embodiments, the one or more second doping regions 508 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 5, the one or more fifth doping regions 513 have an upper horizontal portion, a vertical portion and a lower horizontal portion. The upper horizontal portion of the one or more fifth doping regions 513 has substantially the same cross section as the one or more fifth doping regions 113 of the first exemplary SPAD 100. The vertical portion is formed between the lower part of the one or more first doping regions 507 and the one or more DTI regions 506, and extends from the BSI-DTI region 504 to the upper horizontal portion. The lower horizontal portion is formed above the BSI-DTI region 504 and below the lower part of the one or more first doping regions 507. Similar to the function of the one or more second doping regions 508, as discussed above, the vertical portion and the lower horizontal portion of the one or more fifth doping regions 513 create stronger electrical fields around them, which aids photons striking sides or edges of the semiconductor region in triggering avalanches.

In some embodiments, as shown in Fig. 5, the shortest distance between the sensor wafer 503 and the circuit wafer 510 is D, the shortest distance between a top surface of the one or more fifth doping regions 513 and a bottom surface of the circuit wafer 510 is D1, the upper horizontal portion of the one or more fifth doping regions 513 have a depth of D2, the horizontal portion of the one or more second doping regions 508 has a depth of D2, the vertical portion of the one or more second doping regions 508 has a depth of D5, the SUB DTI pillar 505 has a height of D5, and the shortest distance between a bottom surface of the one or more fifth doping regions 513 and a top surface of the BSI-DTI region 504 is D5. In some other embodiments, there is a gap between the one or more second doping regions 508 and the SUB DTI pillar 505. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 507 are made of. D5 ranges from 1 micrometer to 20 micrometers.

In some embodiments, as shown in Fig. 5, the shortest distance between the one or more third doping regions 509 and the one or more DTI regions 506 is X1, the shortest distance between the horizontal portion of one or more second doping regions 508 and the upper horizontal portion of the one or more fifth doping regions 513 is X2, and the horizontal portion of the one or more second doping regions 508 has a width of X3. The vertical portion of the one or more second doping regions 508 has a width of X3-2XF.

Fig. 6 depicts a cross-sectional view of a fifth exemplary SPAD 600 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 6 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The fifth exemplary SPAD 600 includes a micro lens 602, a sensor wafer 603, a BSI-DTI region 604, a SUB DTI pillar 605, one or more DTI regions 606, one or more first doping regions 607, one or more second doping regions 608, one or more third doping regions 609, a circuit wafer 610, one or more fourth doping regions 611, and one or more fifth doping regions 613. A radiation source 601 is represented by an arrow 612.

The one or more second doping regions 608, together with the one or more third doping regions 609 and the one or more fifth doping regions 613, divide the one or more first doping regions 607 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 6, the one or more first doping regions 607 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is adjacent to the BSI-DTI region 604 and includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 608, the one or more third doping regions 609 and the one or more fifth doping regions 613. In some embodiments, the one or more third doping regions 609 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 6, the cross sections of the protruding portion and the one or more third doping regions 609 are substantially aligned in the vertical direction.

The BSI-DTI region 604 is positioned above the sensor wafer 603. The SUB DTI pillar 605 and the one or more DTI regions 606 are positioned above the BSI-DTI region 604. The SUB DTI pillar 605 extends upwards from the BSI-DTI region 604 to the one or more second doping regions 608. The one or more DTI regions 606 are positioned adjacent to and around the one or more first doping regions 607 and the one or more fifth doping regions 613. The one or more DTI regions 606 also extend from the BSI-DTI region 604 to the circuit wafer 610. The one or more first doping regions 607 are positioned above the BSI-DTI region 604, and around the SUB DTI pillar 605 and the one or more second doping regions 608. The one or more first doping regions 607 are also positioned below and around the one or more third doping regions 609. The one or more second doping regions 608 are positioned above the SUB DTI pillar 605 and below a part of the one or more first doping regions 607.

The one or more third doping regions 609 are surrounded by parts of the one or more first doping regions 607 and are also positioned above a part of the one or more first doping regions 607. The one or more fourth doping regions 611 are positioned above the one or more fifth doping regions 613. In some embodiments, the lower parts of the one or more fourth doping regions 611 are positioned between a part of the one or more first doping regions 607 and one of the one or more DTI regions 606; the upper parts of the one or more fourth doping regions 611 extend above the one or more DTI regions 606.

In some embodiments, the one or more second doping regions 608 have a “T” shaped cross section, as shown in Fig. 6, and the one or more second doping regions 608 consist of a horizontal portion and a vertical portion. In some embodiments, the one or more second doping regions 608 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 608 have a circular cross section. In some embodiments, the one or more second doping regions 608 have an elliptical cross section. In some embodiments, the one or more second doping regions 608 have a rectangular cross section. In some embodiments, the one or more second doping regions 608 have a triangular cross section. In some embodiments, the one or more second doping regions 608 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 6, the shortest distance between the sensor wafer 603 and the circuit wafer 610 is D, the shortest distance between a top surface of the one or more fifth doping regions 613 and a bottom surface of the circuit wafer 610 is D1, the one or more fifth doping regions 613 have a depth of D2, the horizontal portion of the one or more second doping regions 608 has a depth of D1+D2, the vertical portion of the one or more second doping regions 608 has a depth of D3, the SUB DTI pillar 605 has a height of D4, and the shortest distance between a bottom surface of the one or more fifth doping regions 613 and a top surface of the BSI-DTI region 604 is D5.

In some embodiments, as shown in Fig. 6, the sum of D3 and D4 equals or substantially equals D5, and when D3 is larger D4 is smaller accordingly; in some other embodiments, the sum of D3 and D4 is smaller than D5, and there is a gap between the one or more second doping regions 608 and the SUB DTI pillar 605. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 607 are made of. The sum of D3 and D4 ranges from 1 micrometers to 20 micrometers. The ratio of D3 to D4 can be adjusted as needed.

In some embodiments, as shown in Fig. 6, the shortest distance between the one or more third doping regions 609 and the one or more DTI regions 606 is X1, the shortest distance between the horizontal portion of one or more second doping regions 608 and the one or more fifth doping regions 613 is X2, and the horizontal portion of the one or more second doping regions 608 has a width of X3. The vertical portion of the one or more second doping regions 608 has a width of X3-2XF.

Fig. 7 depicts a cross-sectional view of a sixth exemplary SPAD 700 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 7 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The sixth exemplary SPAD 700 includes a micro lens 702, a sensor wafer 703, a BSI-DTI region 704, a SUB DTI pillar 705, one or more DTI regions 706, one or more first doping regions 707, one or more second doping regions 708, one or more third doping regions 709, a circuit wafer 710, one or more fourth doping regions 711, and one or more fifth doping regions 713. A radiation source 701 is represented by an arrow 712.

The one or more second doping regions 708, together with the one or more third doping regions 709 and the one or more fifth doping regions 713, divide the one or more first doping regions 707 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 7, the one or more first doping regions 707 are divided into three parts; the three parts include two upper parts and one lower part; the lower part includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 708, the one or more third doping regions 709 and the one or more fifth doping regions 713. In some embodiments, the one or more third doping regions 709 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 7, the cross sections of the protruding portion and the one or more third doping regions 709 are substantially aligned in the vertical direction.

The BSI-DTI region 704 is positioned above the sensor wafer 703. The SUB DTI pillar 705 and the one or more DTI regions 706 are positioned above the BSI-DTI region 704. The SUB DTI pillar 705 extends upwards from the BSI-DTI region 704 and inside the one or more second doping regions 708. The one or more DTI regions 706 are positioned adjacent to the one or more fifth doping regions 713 and around the one or more first doping regions 707 and the one or more fifth doping regions 713. The one or more DTI regions 706 also extend from the BSI-DTI region 704 to the circuit wafer 710. The one or more first doping regions 707 are positioned above the BSI-DTI region 704 and parts of the one or more fifth doping regions 713, and around the SUB DTI pillar 705 and the one or more second doping regions 708. The one or more first doping regions 707 are also positioned below and around the one or more third doping regions 709.

The one or more second doping regions 708 are positioned above the SUB DTI pillar 705 and below a part of the one or more first doping regions 707. The one or more third doping regions 709 are surrounded by parts of the one or more first doping regions 707 and are also positioned above a part of the one or more first doping regions 707. The one or more fourth doping regions 711 are positioned above the one or more fifth doping regions 713. In some embodiments, the lower parts of the one or more fourth doping regions 711 are positioned between a part of the one or more first doping regions 707 and one of the one or more DTI regions 706; the upper parts of the one or more fourth doping regions 711 extend above the one or more DTI regions 706.

In some embodiments, the one or more second doping regions 708 have a “π” shaped cross section, as shown in Fig. 7, and the one or more second doping regions 708 consist of a horizontal portion and a vertical portion. The vertical portion further includes an upper portion and a lower portion, the upper portion has a rectangular cross section, and the lower portion encapsulates the SUB DTI pillar 705. In some embodiments, the one or more second doping regions 708 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 708 have a circular cross section. In some embodiments, the one or more second doping regions 708 have an elliptical cross section. In some embodiments, the one or more second doping regions 708 have a rectangular cross section. In some embodiments, the one or more second doping regions 708 have a triangular cross section. In some embodiments, the one or more second doping regions 708 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 7, the one or more fifth doping regions 713 have an upper horizontal portion, a vertical portion and a lower horizontal portion. The upper horizontal portion of the one or more fifth doping regions 713 has substantially the same cross section as the one or more fifth doping regions 113 of the first exemplary SPAD 100. The vertical portion is formed between the lower part of the one or more first doping regions 707 and the one or more DTI regions 706, and extends from the BSI-DTI region 704 to the upper horizontal portion. The lower horizontal portion is formed above the BSI-DTI region 704 and below the lower part of the one or more first doping regions 707. Similar to the function of the one or more second doping regions 708, as discussed above, the vertical portion and the lower horizontal portion of the one or more fifth doping regions 713 create stronger electrical fields around them, which aids photons striking sides or edges of the semiconductor region in triggering avalanches.

In some embodiments, as shown in Fig. 7, the shortest distance between the sensor wafer 703 and the circuit wafer 710 is D, the shortest distance between a top surface of the one or more fifth doping regions 713 and a bottom surface of the circuit wafer 710 is D1, the shortest distance between a bottom surface of the one or more third doping regions 709 and the bottom surface of the circuit wafer 710 is also D1, the upper horizontal portion of the one or more fifth doping regions 713 have a depth of D2, the horizontal portion of the one or more second doping regions 708 has a depth of D1+D2, the upper portion of the vertical portion of the one or more second doping regions 708 has a depth of D3, the lower portion of the vertical portion of the one or more second doping regions 708 has a depth of D4, the SUB DTI pillar 705 has a height of D4, and the shortest distance between a bottom surface of the one or more fifth doping regions 713 and a top surface of the BSI-DTI region 704 is D5.

In some embodiments, as shown in Fig. 7, the sum of D3 and D4 equals or substantially equals D5, and when D3 is larger D4 is smaller accordingly; In some other embodiments, the sum of D3 and D4 is smaller than D5, and there is a gap between the one or more second doping regions 708 and the SUB DTI pillar 705. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 707 are made of. The sum of D3 and D4 ranges from 1 micrometers to 20 micrometers. The ratio of D3 to D4 can be adjusted as needed.

In some embodiments, as shown in Fig. 7, the shortest distance between the one or more third doping regions 709 and the one or more DTI regions 706 is X1, the shortest distance between the horizontal portion of one or more second doping regions 708 and the upper horizontal portion of the one or more fifth doping regions 713 is X2, and the horizontal portion of the one or more second doping regions 708 has a width of X3. The vertical portion of the one or more second doping regions 708 has a width of X3-2XF.

Fig. 8 depicts a cross-sectional view of a seventh exemplary SPAD that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 8 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The seventh exemplary SPAD 800 includes a micro lens 802, a sensor wafer 803, a BSI-DTI region 804, a SUB DTI pillar 805, one or more DTI regions 806, one or more first doping regions 807, one or more second doping regions 808, one or more third doping regions 809, a circuit wafer 810, one or more fourth doping regions 811, and one or more fifth doping regions 813. A radiation source 801 is represented by an arrow 812.

The one or more second doping regions 808, together with the one or more third doping regions 809 and the one or more fifth doping regions 813, divide the one or more first doping regions 807 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 8, the one or more first doping regions 807 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is adjacent to the BSI-DTI region 804 and includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 808, the one or more third doping regions 809 and the one or more fifth doping regions 813. In some embodiments, the one or more third doping regions 809 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 8, the cross sections of the protruding portion and the one or more third doping regions 809 are substantially aligned in the vertical direction.

The BSI-DTI region 804 is positioned above the sensor wafer 803. The SUB DTI pillar 805 and the one or more DTI regions 806 are positioned above the BSI-DTI region 804. The SUB DTI pillar 805 extends upwards from the BSI-DTI region 804 to the one or more second doping regions 808. The one or more DTI regions 806 are positioned adjacent to and around the one or more first doping regions 807 and the one or more fifth doping regions 813. The one or more DTI regions 806 also extend from the BSI-DTI region 804 to the circuit wafer 810. The one or more first doping regions 807 are positioned above the BSI-DTI region 804, and around the SUB DTI pillar 805 and the one or more second doping regions 808. The one or more first doping regions 807 are also positioned below and around the one or more third doping regions 809.

The one or more second doping regions 808 are positioned above the SUB DTI pillar 805 and below a part of the one or more first doping regions 807. The one or more third doping regions 809 are surrounded by parts of the one or more first doping regions 807 and are also positioned above a part of the one or more first doping regions 807. The one or more fourth doping regions 811 are positioned above the one or more fifth doping regions 813. In some embodiments, the lower parts of the one or more fourth doping regions 811 are positioned between a part of the one or more first doping regions 807 and one of the one or more DTI regions 806; the upper parts of the one or more fourth doping regions 811 extend above the one or more DTI regions 806.

In some embodiments, the one or more second doping regions 808 have a rectangular cross section, as shown in Fig. 8. In some embodiments, the one or more second doping regions 808 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 808 have a circular cross section. In some embodiments, the one or more second doping regions 808 have an elliptical cross section. In some embodiments, the one or more second doping regions 808 have a triangular cross section. In some embodiments, the one or more second doping regions 808 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 8, the shortest distance between the sensor wafer 803 and the circuit wafer 810 is D, the shortest distance between a top surface of the one or more fifth doping regions 813 and a bottom surface of the circuit wafer 810 is D1, the one or more fifth doping regions 813 have a depth of D2, the one or more second doping regions 808 has a depth of D2, the SUB DTI pillar 805 has a height of D5, and the shortest distance between a bottom surface of the one or more fifth doping regions 813 and a top surface of the BSI-DTI region 804 is also D5. In some there is a gap between the one or more second doping regions 808 and the SUB DTI pillar 805, and the depth of the BSI-DTI region 804 is smaller than D5. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 807 are made of. D5 ranges from 1 micrometer to 20 micrometers.

In some embodiments, as shown in Fig. 8, the shortest distance between the one or more third doping regions 809 and the one or more DTI regions 806 is X1, the shortest distance between the one or more second doping regions 808 and the one or more fifth doping regions 813 is X2, and the one or more second doping regions 808 has a width of X 3. The SUB DTI pillar 805 has a width of X3-2XF.

Fig. 9 depicts a cross-sectional view of an eighth exemplary SPAD 900 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 9 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The eighth exemplary SPAD 900 includes a micro lens 902, a sensor wafer 903, a BSI-DTI region 904, a SUB DTI pillar 905, one or more DTI regions 906, one or more first doping regions 907, one or more second doping regions 908, one or more third doping regions 909, a circuit wafer 910, one or more fourth doping regions 911, and one or more fifth doping regions 913. A radiation source 901 is represented by an arrow 912.

The one or more second doping regions 908, together with the one or more third doping regions 909 and the one or more fifth doping regions 913, divide the one or more first doping regions 907 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 9, the one or more first doping regions 907 are divided into three parts; the three parts include two upper parts and one lower part; the lower part includes a protruding portion; the protruding portion is in the upper portion of the lower part, and adjacent to the one or more second doping regions 908, the one or more third doping regions 909 and the one or more fifth doping regions 913. In some embodiments, the one or more third doping regions 909 have substantially the same top view as the protruding portion. In some embodiments, as shown in Fig. 9, the cross sections of the protruding portion and the one or more third doping regions 909 are substantially aligned in the vertical direction.

The BSI-DTI region 904 is positioned above the sensor wafer 903. The SUB DTI pillar 905 and the one or more DTI regions 906 are positioned above the BSI-DTI region 904. The SUB DTI pillar 905 extends upwards from the BSI-DTI region 904 and inside the one or more second doping regions 908. The one or more DTI regions 906 are positioned around the one or more first doping regions 907 and the one or more fifth doping regions 913. The one or more DTI regions 906 also extend from the BSI-DTI region 904 to the circuit wafer 910. The one or more first doping regions 907 are positioned above lower parts of the one or more fifth doping regions 913, which are above the BSI-DTI region 904. The one or more first doping regions 907 are also positioned around the SUB DTI pillar 905 and the one or more second doping regions 908. The one or more first doping regions 907 are also positioned below and around the one or more third doping regions 909. The one or more second doping regions 908 are positioned above and around and the SUB DTI pillar 905, and below a part of the one or more first doping regions 907.

The one or more third doping regions 909 are surrounded by parts of the one or more first doping regions 907 and are also positioned above a part of the one or more first doping regions 907. The one or more fourth doping regions 911 are positioned above the one or more fifth doping regions 913. In some embodiments, the lower parts of the one or more fourth doping regions 911 are positioned between a part of the one or more first doping regions 907 and one of the one or more DTI regions 906; the upper parts of the one or more fourth doping regions 911 extend above the one or more DTI regions 906.

In some embodiments, the one or more second doping regions 908 have a “π” shaped cross section, as shown in Fig. 9, and the one or more second doping regions 908 consist of a horizontal portion and a vertical portion. The vertical portion encapsulates the SUB DTI pillar 905. In some embodiments, the one or more second doping regions 908 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 908 have a circular cross section. In some embodiments, the one or more second doping regions 908 have an elliptical cross section. In some embodiments, the one or more second doping regions 908 have a rectangular cross section. In some embodiments, the one or more second doping regions 908 have a triangular cross section. In some embodiments, the one or more second doping regions 908 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 9, the one or more fifth doping regions 913 have an upper horizontal portion, a vertical portion and a lower horizontal portion. The upper horizontal portion of the one or more fifth doping regions 913 has substantially the same cross section as the one or more fifth doping regions 113 of the first exemplary SPAD 100. The vertical portion is formed between the lower part of the one or more first doping regions 907 and the one or more DTI regions 906, and extends from the BSI-DTI region 904 to the upper horizontal portion. The lower horizontal portion is formed above the BSI-DTI region 904 and below the lower part of the one or more first doping regions 907. Similar to the function of the one or more second doping regions 908, as discussed above, the vertical portion and the lower horizontal portion of the one or more fifth doping regions 913 create stronger electrical fields around them, which aids photons striking sides or edges of the semiconductor region in triggering avalanches.

In some embodiments, as shown in Fig. 9, the shortest distance between the sensor wafer 903 and the circuit wafer 910 is D, the shortest distance between a top surface of the one or more fifth doping regions 913 and a bottom surface of the circuit wafer 910 is D1, the upper horizontal portion of the one or more fifth doping regions 913 has a depth of D2, the horizontal portion of the one or more second doping regions 908 has a depth of D1+D2, the vertical portion of the one or more second doping regions 908 has a depth of D5, the SUB DTI pillar 905 has a height of D5, and the shortest distance between a bottom surface of the one or more fifth doping regions 913 and a top surface of the BSI-DTI region 904 is D5.

In some other embodiments, there is a gap between the one or more second doping regions 908 and the SUB DTI pillar 905, and the depth of the SUB DTI pillar 905 is smaller than D5. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 907 are made of. D5 ranges from 1 micrometer to 20 micrometers.

In some embodiments, as shown in Fig. 9, the shortest distance between the one or more third doping regions 909 and the one or more DTI regions 906 is X1, the shortest distance between the horizontal portion of one or more second doping regions 908 and the upper horizontal portion of the one or more fifth doping regions 913 is X2, and the horizontal portion of the one or more second doping regions 908 has a width of X3. The vertical portion of the one or more second doping regions 908 has a width of X3-2XF.

Fig. 10 depicts a cross-sectional view of a ninth exemplary SPAD 1000 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 10 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The ninth exemplary SPAD 1000 includes a micro lens 1002, a sensor wafer 1003, a BSI-DTI region 1004, a SUB DTI pillar 1005, one or more DTI regions 1006, one or more first doping regions 1007, one or more second doping regions 1008, one or more third doping regions 1009, a circuit wafer 1010, and one or more fourth doping regions 1011. A radiation source 1001 is represented by an arrow 1012.

The one or more second doping regions 1008, together with the one or more third doping regions 1009, divide the one or more first doping regions 1007 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 10, the one or more first doping regions 1007 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is adjacent to the BSI-DTI region 1004.

The BSI-DTI region 1004 is positioned above the sensor wafer 1003. The SUB DTI pillar 1005 and the one or more DTI regions 1006 are positioned above the BSI-DTI region 1004. The SUB DTI pillar 1005 extends upwards from the BSI-DTI region 1004 to the one or more second doping regions 1008. The one or more DTI regions 1006 are positioned adjacent to and around the one or more first doping regions 1007. The one or more DTI regions 1006 also extend from the BSI-DTI region 1004 to the circuit wafer 1010. The one or more first doping regions 1007 are positioned above the BSI-DTI region 1004, and around the SUB DTI pillar 1005 and the one or more second doping regions 1008. The one or more first doping regions 1007 are also positioned below and around the one or more third doping regions 1009. The one or more second doping regions 1008 are positioned above the SUB DTI pillar 1005 and below the one or more third doping regions 1009 and a part of the one or more first doping regions 1007.

The one or more third doping regions 1009 are surrounded by parts of the one or more first doping regions 1007 and are also positioned above the one or more second doping regions 1008. The one or more fourth doping regions 1011 are positioned above the one or more second doping regions 1008. In some embodiments, the lower parts of the one or more fourth doping regions 1011 are positioned between a part of the one or more first doping regions 1007 and one of the one or more DTI regions 1006; the upper parts of the one or more fourth doping regions 1011 extend above the one or more DTI regions 1006.

In some embodiments, the one or more second doping regions 1008 have a “T” shaped cross section, as shown in Fig. 10, and the one or more second doping regions 1008 consist of a horizontal portion and a vertical portion. In some embodiments, the one or more second doping regions 1008 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 1008 have a circular cross section. In some embodiments, the one or more second doping regions 1008 have an elliptical cross section. In some embodiments, the one or more second doping regions 1008 have a rectangular cross section. In some embodiments, the one or more second doping regions 1008 have a triangular cross section. In some embodiments, the one or more second doping regions 1008 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 10, the shortest distance between the sensor wafer 1003 and the circuit wafer 1010 is D, the shortest distance between a top surface of the one or more second doping regions 1008 and a bottom surface of the circuit wafer 1010 is D1, the horizontal portion of the one or more second doping regions 1008 has a depth of D2, the vertical portion of the one or more second doping regions 1008 has a depth of D3, the SUB DTI pillar 1005 has a height of D4, and the shortest distance between a bottom surface of the one or more second doping regions 1008 and a top surface of the BSI-DTI region 1004 is D5.

In some embodiments, as shown in Fig. 10, the sum of D3 and D4 equals or substantially equals D5, and when D3 is larger D4 is smaller accordingly; In some other embodiments, the sum of D3 and D4 is smaller than D5, and there is a gap between the one or more second doping regions 1008 and the SUB DTI pillar 1005. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 1007 are made of. The sum of D3 and D4 ranges from 1 micrometer to 20 micrometers. The ratio of D3 to D4 can be adjusted as needed.

In some embodiments, as shown in Fig. 10, the shortest distance between the one or more third doping regions 1009 and the one or more DTI regions 1006 is X1, the one or more third doping regions 1009 has a width of X2, and the horizontal portion of the one or more second doping regions 1008 has a width of X1+X2+X3+X2+X1. The vertical portion of the one or more second doping regions 1008 has a width of X3-2XF.

Fig. 11 depicts a cross-sectional view of a tenth exemplary SPAD 1100 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 11 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The tenth exemplary SPAD 1100 includes a micro lens 1102, a sensor wafer 1103, a BSI-DTI region 1104, a SUB DTI pillar 1105, one or more DTI regions 1106, one or more first doping regions 1107, one or more second doping regions 1108, one or more third doping regions 1109, a circuit wafer 1110, and one or more fourth doping regions 1111. A radiation source 1101 is represented by an arrow 1112.

The one or more second doping regions 1108, together with the one or more third doping regions 1109, divide the one or more first doping regions 1107 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 11, the one or more first doping regions 1107 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is encapsulated by the one or more second doping regions 1108.

The BSI-DTI region 1104 is positioned above the sensor wafer 1103. The SUB DTI pillar 1105 and the one or more DTI regions 1106 are positioned above the BSI-DTI region 1104. The SUB DTI pillar 1105 extends upwards from the BSI-DTI region 1104 and inside the one or more second doping regions 1108. The one or more DTI regions 1106 are positioned adjacent to the one or more second doping regions 1108 and around the one or more first doping regions 1107 and the one or more second doping regions 1108. The one or more DTI regions 1106 also extend from the BSI-DTI region 1104 to the circuit wafer 1110. The one or more first doping regions 1107 are positioned above the BSI-DTI region 1104 and the one or more second doping regions 1108, and around the SUB DTI pillar 1105 and the one or more second doping regions 1108. The one or more first doping regions 1107 are also positioned around the one or more third doping regions 1109. The one or more second doping regions 1108 encapsulate the SUB DTI pillar 1105 and are positioned below the one or more third doping regions 1109 and a part of the one or more first doping regions 1107. The one or more second doping regions 1108 also encapsulate the lower portion of the one or more first doping regions 1107.

The one or more third doping regions 1109 are surrounded by parts of the one or more first doping regions 1107 and are also positioned above the one or more second doping regions 1108. The one or more fourth doping regions 1111 are positioned above the one or more second doping regions 1108. In some embodiments, the lower parts of the one or more fourth doping regions 1111 are positioned between a part of the one or more first doping regions 1107 and one of the one or more DTI regions 1106; the upper parts of the one or more fourth doping regions 1111 extend above the one or more DTI regions 1106.

In some embodiments, a cross section of the one or more second doping regions 1108 is a “B” rotated 90 degrees clockwise, as shown in Fig. 11, and the one or more second doping regions 1108 consist of vertical portions, an upper horizontal, and a lower horizontal portion. The vertical portions consist of at least a central column. The central column consists of a top part and a bottom part. The bottom part of the central column encapsulates the SUB DTI pillar 1105. The lower horizontal portion of the one or more second doping regions 1108 is positioned above the BSI-DTI region 1104 and under the one or more first doping regions 1107.

In some embodiments, the one or more second doping regions 1108 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 1108 have a circular cross section. In some embodiments, the one or more second doping regions 1108 have an elliptical cross section. In some embodiments, the one or more second doping regions 1108 have a rectangular cross section. In some embodiments, the one or more second doping regions 1108 have a triangular cross section. In some embodiments, the one or more second doping regions 1108 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 11, the shortest distance between the sensor wafer 1103 and the circuit wafer 1110 is D, the shortest distance between a top surface of the one or more second doping regions 1108 and a bottom surface of the circuit wafer 1110 is D1, the upper horizontal portion of the one or more second doping regions 1108 has a depth of D2, the top part of the central column of the one or more second doping regions 1108 has a depth of D3, the SUB DTI pillar 1105 has a height of D4, and the shortest distance between a bottom surface of upper horizontal portion of the one or more second doping regions 1108 and a top surface of the BSI-DTI region 1104 is D5.

In some embodiments, as shown in Fig. 11, the sum of D3 and D4 equals or substantially equals D5, and when D3 is larger D4 is smaller accordingly; In some other embodiments, the sum of D3 and D4 is smaller than D5, and there is a gap between the one or more second doping regions 1108 and the SUB DTI pillar 1105. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 1107 are made of. The sum of D3 and D4 ranges from 1 micrometer to 20 micrometers. The ratio of D3 to D4 can be adjusted as needed.

In some embodiments, the shortest distance between the one or more third doping regions 1109 and the one or more DTI regions 1106 is X1, the one or more third doping regions 1109 has a width of X2, and the upper horizontal portion of the one or more second doping regions 1108 has a width of X1+X2+X3+X2+X1. The central column of the one or more second doping regions 1108 has a width of X3-2XF.

Fig. 12 depicts a cross-sectional view of a eleventh exemplary SPAD 1200 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 12 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The eleventh exemplary SPAD 1200 includes a micro lens 1202, a sensor wafer 1203, a BSI-DTI region 1204, a SUB DTI pillar 1205, one or more DTI regions 1206, one or more first doping regions 1207, one or more second doping regions 1208, one or more third doping regions 1209, a circuit wafer 1210, and one or more fourth doping regions 1211. A radiation source 1201 is represented by an arrow 1212.

The one or more second doping regions 1208, together with the one or more third doping regions 1209, divide the one or more first doping regions 1207 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 12, the one or more first doping regions 1207 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is adjacent to the BSI-DTI region 1204.

The BSI-DTI region 1204 is positioned above the sensor wafer 1203. The SUB DTI pillar 1205 and the one or more DTI regions 1206 are positioned above the BSI-DTI region 1204. The SUB DTI pillar 1205 extends upwards from the BSI-DTI region 1204 to the one or more second doping regions 1208. The one or more DTI regions 1206 are positioned adjacent to and around the one or more first doping regions 1207. The one or more DTI regions 1206 also extend from the BSI-DTI region 1204 to the circuit wafer 1210. The one or more first doping regions 1207 are positioned above the BSI-DTI region 1204, and around the SUB DTI pillar 1205. The one or more first doping regions 1207 are also positioned below and around the one or more third doping regions 1209. The one or more second doping regions 1208 are positioned above the SUB DTI pillar 1205 and below the one or more third doping regions 1209 and a part of the one or more first doping regions 1207.

The one or more third doping regions 1209 are surrounded by parts of the one or more first doping regions 1207 and are also positioned above the one or more second doping regions 1208. The one or more fourth doping regions 1211 are positioned above the one or more second doping regions 1208. In some embodiments, the lower parts of the one or more fourth doping regions 1211 are positioned between a part of the one or more first doping regions 1207 and one of the one or more DTI regions 1206; the upper parts of the one or more fourth doping regions 1211 extend above the one or more DTI regions 1206.

In some embodiments, the one or more second doping regions 1208 have rectangular cross section, as shown in Fig. 12. In some embodiments, the one or more second doping regions 1208 have an “T” shaped cross section In some embodiments, the one or more second doping regions 1208 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 1208 have a circular cross section. In some embodiments, the one or more second doping regions 1208 have an elliptical cross section. In some embodiments, the one or more second doping regions 1208 have a rectangular cross section. In some embodiments, the one or more second doping regions 1208 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 12, the shortest distance between the sensor wafer 1203 and the circuit wafer 1210 is D, the shortest distance between a top surface of the one or more second doping regions 1208 and a bottom surface of the circuit wafer 1210 is D1, the one or more second doping regions 1208 have a depth of D2, the SUB DTI pillar 1205 has a height of D5, and the shortest distance between a bottom surface of the one or more second doping regions 1208 and a top surface of the BSI-DTI region 1204 is D5.

In some other embodiments, the height of the SUB DTI pillar 1205 is smaller than D5, and there is a gap between the one or more second doping regions 1208 and the SUB DTI pillar 1205. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 1207 are made of. D5 ranges from 1 micrometer to 20 micrometers.

In some embodiments, as shown in Fig. 12, the shortest distance between the one or more third doping regions 1209 and the one or more DTI regions 1206 is X1, the one or more third doping regions 1209 has a width of X2, and the one or more second doping regions 1208 has a width of X1+X2+X3+X2+X1. The SUB DTI pillar 1205 has a width of X3-2XF.

Fig. 13 depicts a cross-sectional view of a twelfth exemplary SPAD 1300 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. Many elements in Fig. 13 may correspond to their respective counterparts in Fig. 1 and other figures, and may have substantially the same features and functionalities as described above.

The twelfth exemplary SPAD 1300 includes a micro lens 1302, a sensor wafer 1303, a BSI-DTI region 1304, a SUB DTI pillar 1305, one or more DTI regions 1306, one or more first doping regions 1307, one or more second doping regions 1308, one or more third doping regions 1309, a circuit wafer 1310, and one or more fourth doping regions 1311. A radiation source 1301 is represented by an arrow 1312.

The one or more second doping regions 1308, together with the one or more third doping regions 1309, divide the one or more first doping regions 1307 into multiple parts in some embodiments. In some embodiments, as shown in Fig. 13, the one or more first doping regions 1307 are divided into three parts; the three parts include two upper parts and one lower part; the lower part is encapsulated by the one or more second doping regions 1308.

The BSI-DTI region 1304 is positioned above the sensor wafer 1303. The SUB DTI pillar 1305 and the one or more DTI regions 1306 are positioned above the BSI-DTI region 1304. The SUB DTI pillar 1305 extends upwards from the BSI-DTI region 1304 and inside the one or more second doping regions 1308. The one or more DTI regions 1306 are positioned adjacent to the one or more second doping regions 1308 and around the one or more first doping regions 1307 and the one or more second doping regions 1308. The one or more DTI regions 1306 also extend from the BSI-DTI region 1304 to the circuit wafer 1310. The one or more first doping regions 1307 are positioned above the BSI-DTI region 1304 and the one or more second doping regions 1308, and around the SUB DTI pillar 1305 and the one or more second doping regions 1308. The one or more first doping regions 1307 are also positioned around the one or more third doping regions 1309. The one or more second doping regions 1308 encapsulate the SUB DTI pillar 1305 and are positioned below the one or more third doping regions 1309 and a part of the one or more first doping regions 1307. The one or more second doping regions 1308 also encapsulate the lower portion of the one or more first doping regions 1307.

The one or more third doping regions 1309 are surrounded by parts of the one or more first doping regions 1307 and are also positioned above the one or more second doping regions 1308. The one or more fourth doping regions 1311 are positioned above the one or more second doping regions 1308. In some embodiments, the lower parts of the one or more fourth doping regions 1311 are positioned between a part of the one or more first doping regions 1307 and one of the one or more DTI regions 1306; the upper parts of the one or more fourth doping regions 1311 extend above the one or more DTI regions 1306.

In some embodiments, a cross section of the one or more second doping regions 1308 is a “B” rotated 90 degrees clockwise, as shown in Fig. 13, and the one or more second doping regions 1308 consist of vertical portions, an upper horizontal, and a lower horizontal portion. The vertical portions consist of at least a central column. The central column encapsulates the SUB DTI pillar 1305. The lower horizontal portion of the one or more second doping regions 1308 is positioned above the BSI-DTI region 1304 and under the one or more first doping regions 1307. In some embodiments, the one or more second doping regions 1308 have an “I” shaped cross section. In some embodiments, the one or more second doping regions 1308 have a circular cross section. In some embodiments, the one or more second doping regions 1308 have an elliptical cross section. In some embodiments, the one or more second doping regions 1308 have a rectangular cross section. In some embodiments, the one or more second doping regions 1308 have a triangular cross section. In some embodiments, the one or more second doping regions 1308 have an irregularly shaped cross section.

In some embodiments, as shown in Fig. 13, the shortest distance between the sensor wafer 1303 and the circuit wafer 1310 is D, the shortest distance between a top surface of the one or more second doping regions 1308 and a bottom surface of the circuit wafer 1310 is D1, the upper horizontal portion of the one or more second doping regions 1308 has a depth of D2, the central column of the one or more second doping regions 1308 has a depth of D5, the SUB DTI pillar 1305 has a height of D5, and the shortest distance between a bottom surface of upper horizontal portion of the one or more second doping regions 1308 and a top surface of the BSI-DTI region 1304 is D5.

In some other embodiments, the height of the SUB DTI pillar 1305 is smaller than D5, and there is a gap between the one or more second doping regions 1308 and the SUB DTI pillar 1305. The gap can be devoid of solid materials. The gap can be filled with silicon. The gap can also be filled with the same material (s) that the wafers are made of. The gap can also be filled with the same material (s) that the one or more first doping regions 1307 are made of. D5 ranges from 1 micrometer to 20 micrometers.

In some embodiments, the shortest distance between the one or more third doping regions 1309 and the one or more DTI regions 1306 is X1, the one or more third doping regions 1309 has a width of X2, and the upper horizontal portion of the one or more second doping regions 1308 has a width of X1+X2+X3+X2+X1. The central column of the one or more second doping regions 1308 has a width of X3-2XF.

Fig. 14 depicts a top view of an SPAD 1400 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. As shown in Fig. 14, the SPAD 1400 includes at least a circuit wafer 1410, a DTI region 1406, multiple fourth doping regions 1411, one or more first doping regions 1407, a third doping region 1409, and a second doping region 1408. The second doping region 1408 is underneath the one or more first doping regions 1407, and therefore is represented with a dotted circle. The SPAD 1400 may correspond to a SPAD depicted in one or more of the previous figures. The SPAD 1400 may also correspond to none of the SPADs depicted in the previous figures. The second doping region 1408 in Fig. 14 may correspond to a vertical portion of one or more second doping regions depicted in some of the previous figures. The DTI region 1406 is positioned adjacent to and around the fourth doping regions 1411 and the one or more first doping regions 1407. The one or more first doping regions 1407 is positioned adjacent to and around the third doping region 1409. The third doping region 1409 is positioned around the second doping region 1408.

In some embodiments, as shown in Fig. 14, the SPAD has a circular layout, the DTI region 1406 has an annular top view, the top view of the one or more first doping regions 1407 is two concentric rings, the second doping region 1408 has a circular top view, the third doping region 1409 has an annular top view, and each of the fourth doping regions 1411 has a rectangular top view. In some embodiments, as shown in Fig. 14, the SPAD 1400 includes four fourth doping regions 1411, and they are surrounded by the one or more first doping regions 1407 and the DTI region 1406, and are positioned evenly along the outer circumference of the one or more first doping regions 1407.

In some embodiments, the SPAD 1400 has a quadrilateral layout. In some embodiments, the DTI region 1406 has a rectangular top view. In some embodiments, the one or more first doping regions 1407 has a rectangular top view. In some embodiments, the second doping region 1408 has a rectangular top view. In some embodiments, the third doping region 1409 has a rectangular top view. In some embodiments, each of the fourth doping regions 1411 has a circular top view.

In some embodiments, the SPAD 1400 has a hexagonal layout. In some embodiments, the DTI region 1406 has a hexagonal top view. In some embodiments, the one or more first doping regions 1407 has a hexagonal top view. In some embodiments, the second doping region 1408 has a hexagonal top view. In some embodiments, the third doping region 1409 has a hexagonal top view. In some embodiments, the SPAD includes six fourth doping regions 1411 and they are positioned evenly along the outer circumference of the one or more first doping regions 1407.

In some embodiments, the shape of the top view of the second doping region 1408 may correspond to the shape of the top view of the third doping region 1409. For example, when the cross-sectional shape of the second doping region 1408 is circular, the shape of the top view of the third doping region 1409 may be a donut-like ring; when the cross-sectional shape of the second doping region 1408 is square-like, the shape of the top view of the third doping region 1409 may be a square-like ring.

In some embodiments, as shown in Fig. 14, the SPAD 1400 has discrete rotational symmetry of the fourth order, with its axis passing through the second doping region 1408 and perpendicular to the circuit wafer 1410. In some embodiments, the SPAD 1400 has discrete rotational symmetry of the sixth order, with its axis passing through the second doping region 1408 and perpendicular to the circuit wafer 1410. In some embodiments, the SPAD 1400 has discrete rotational symmetry of the second order, third order, fifth order, seventh order, or eighth order, with its axis passing through the second doping region 1408 and perpendicular to the circuit wafer 1410. In some embodiments, the SPAD 1400 is not symmetric.

Fig. 15 depicts a bottom view of an SPAD 1500 that is suitable for use in SPAD image sensors according to one embodiment of the present disclosure. As shown in Fig. 15, the SPAD 1500 at least includes a sensor wafer and a micro lens 1502. The micro lens 1502 is positioned under the sensor wafer 1503.

As shown in Fig. 15, in some embodiments, the micro lens 1502 has a circular bottom view. In some embodiments, the micro lens 1502 has a rectangular bottom view. In some embodiments, the micro lens 1502 has a hexagonal bottom view.

While particular elements, embodiments, and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto because modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the invention.

Claims

A backside illumination (BSI) single-photon avalanche diode (SPAD) sensing unit, comprising:

a deep trench isolation (DTI) region;

a first cathode region formed above the DTI region;

a channel formed within the first cathode region;

an anode region formed above the first cathode region and the channel; and

a second cathode region formed above the anode region to output a leakage current.
The BSI-SPAD sensing unit as recited in claim 1, wherein:

the channel includes a first pillar coupled with the anode region and a second pillar coupled with the DTI region, and

the first pillar contains a p type dopant and the second pillar is a SUB-DTI.
The BSI-SPAD sensing unit as recited in claim 2, wherein:

the channel further includes a filling material between the first pillar and the second pillar.
The BSI-SPAD sensing unit as recited in claim 1, wherein:

the first cathode region comprises a n-type dopant,

the second cathode region comprises a n+ type dopant, and

the anode region comprises a p type dopant.
The BSI-SPAD sensing unit as recited in claim 1, wherein:

the first cathode region comprises a p-type dopant,

the second cathode region comprises a p+ type dopant,

the anode region comprises a n type dopant, and the channel contains a n type dopant.
The BSI-SPAD sensing unit as recited in claim 1, further comprising:

a DTI sidewall to cover sides of the first cathode region.
The BSI-SPAD sensing unit as recited in claim 1, further comprising:

an anode layer to separate the first cathode region from the BSI-DTI region, and separate the first cathode region from the channel.
The BSI-SPAD sensing unit as recited in claim 1, further comprising:

a third cathode region located within the anode region, positioning above the first cathode region and below the second cathode region.
The BSI-SPAD sensing unit as recited in claim 1, wherein:

the channel is substantially located in a central area of the first cathode region, and a cross-sectional view of the channel is circle, rectangle, or hexagon.
A backside illumination (BSI) single-photon avalanche diode (SPAD) sensor, comprising:

a circuit wafer comprising one or more BSI-SPAD sensing units; and

a sensor wafer attached to the one or more BSI-SPAD sensing units, wherein each of the BSI-SPAD sensing unit comprises:

a deep trench isolation (DTI) region;

a first cathode region comprising n-type dopant formed above the DTI region;

a channel comprising p type dopant formed within the first cathode region;

an anode region comprising p type dopant formed above the first cathode region and the channel; and

a second cathode region comprising n+ type dopant formed above the anode region to output a leakage current.
The BSI-SPAD sensor as recited in claim 10, wherein:

the sensor wafer includes a lens to direct photons into the one or more BSI-SPAD sensing units, and

when one of the photons enters a BSI-SPAD sensing unit selected from the one or more BSI-SPAD sensing units, the BSI-SPAD sensing unit outputs a corresponding leakage current to a circuitry located on the circuit wafer.
The BSI-SPAD sensor as recited in claim 10, wherein:

the channel includes a first pillar coupled with the anode region and a second pillar coupled with the DTI region, and

the first pillar contains a p type dopant and the second pillar is a SUB-DTI.
The BSI-SPAD sensor as recited in claim 10, wherein:

the first cathode region comprises a n-type dopant,

the second cathode region comprises a n+ type dopant, and

the anode region comprises a p type dopant.
The BSI-SPAD sensor as recited in claim 10, wherein:

the first cathode region comprises a p-type dopant,

the second cathode region comprises a p+ type dopant,

the anode region comprises a n type dopant, and the channel contains a n type dopant.