Back-illuminated image sensor

Abstract

The present invention is titled "Back-illuminated image sensor". The present invention provides an image sensor device, embodiments of which may include through-silicon vias (TSVs) that are formed in the rear side of the image sensor device and extend through the material of the die to metal landing pads. The metal landing pads may be within a contact layer. The device may include a TSV edge seal ring that surrounds a portion of the TSVs in the contact layer and extends from a first surface of the contact layer into the contact layer to a depth that coextends with the depth of the TSVs.

Description

Technical Field

[0001] Aspects of the present document generally relate to image sensors, such as back-illuminated image sensors. More specific embodiments relate to back-illuminated sensors having through-silicon vias. Background Art

[0002] Image sensors convey information related to an image by transmitting signals in response to incident electromagnetic radiation. Image sensors are used in a variety of devices, including smart phones, digital cameras, night vision devices, medical imagers, and many other devices. Back-illuminated image sensors can be used to improve the light reception efficiency of an image sensor, particularly for specific light wavelengths. Summary of the Invention

[0003] Embodiments of an image sensor device can include a through-silicon via (TSV) that is formed in a rear side of the image sensor device and extends through the material of the die to a metal landing pad. The metal landing pad can be within a contact layer. The device can include a TSV edge seal ring that surrounds a portion of the TSV in the contact layer and extends from a first surface of the contact layer into the contact layer to a depth that co-extends with the depth of the TSV.

[0004] Embodiments of an image sensor device can include one, all, or any of the following:

[0005] The TSV edge seal ring can include tungsten.

[0006] The TSV edge seal ring can be physically isolated from the metal landing pad.

[0007] The device can include a pinned layer directly coupled to one or more sidewalls of the TSV.

[0008] The device can include an anti-reflection layer coupled to one or more sidewalls of the TSV.

[0009] Embodiments of an image sensor device can include a through-silicon via (TSV) that is formed in a rear side of the image sensor device and extends through the material of the die to a metal landing pad. The metal landing pad can be within a contact layer. The device can include a TSV edge seal ring that surrounds a portion of the TSV in the contact layer and extends from a first surface of the contact layer to the metal landing pad.

[0010] The TSV edge seal ring can be directly coupled to a diffusion barrier layer.

[0011] The TSV edge seal ring can be directly coupled to one or more shallow trench isolation (STI) regions.

[0012] Embodiments of an image sensor device may include: a first through-silicon via (TSV) formed in the image sensor device, extending from the back side of the image sensor device into the material of the die to reach a contact layer; a second TSV formed within the first TSV and extending into the material of the die to reach a metal landing pad, where the metal landing pad is within the contact layer; and a TSV edge seal ring within the contact layer, surrounding the second TSV in the contact layer and extending from a first surface of the contact layer into the contact layer to a depth coextensive with the depth of the second TSV.

[0013] The TSV edge seal ring may include tungsten.

[0014] The TSV edge seal ring may be directly coupled to the metal landing pad.

[0015] The TSV edge seal ring may be physically isolated from the metal landing pad.

[0016] The device may include a pinning layer directly coupled to one or more sidewalls of the first TSV.

[0017] The device may include an anti-reflection layer coupled to one or more sidewalls of the first TSV.

[0018] The perimeter of the TSV edge seal ring may be aligned with the perimeter of the first TSV.

[0019] The perimeter of the TSV edge seal ring may be greater than the perimeter of the first TSV.

[0020] The perimeter of the TSV edge seal ring may be less than the perimeter of the first TSV.

[0021] The TSV edge seal ring may be directly coupled to a diffusion barrier layer.

[0022] The TSV edge seal ring may be directly coupled to one or more shallow trench isolation (STI) regions.

[0023] For those of ordinary skill in the art, the above and other aspects, features, and advantages will be apparent from the specification, the drawings, and the claims. Description of the Drawings

[0024] Embodiments will be described below in conjunction with the drawings, in which like reference numerals represent like elements, and:

[0025] Figure 1 is a cross-sectional side view of an image sensor device;

[0026] Figure 2 is a cross-sectional side view of another embodiment of an image sensor device;

[0027] Figure 3 A top view that is part of a first embodiment of an image sensor device, showing the relationship between a first through-silicon via (TSV), a second TSV, and a TSV edge seal ring;

[0028] Figure 4 A top view that is part of a second embodiment of an image sensor device, showing the relationship between a first through-silicon via (TSV), a second TSV, and a TSV edge seal ring; and

[0029] Figure 5 A top view that is part of a third embodiment of an image sensor device, showing the relationship between a first through-silicon via (TSV), a second TSV, and a TSV edge seal ring. Detailed Embodiments

[0030] The present disclosure, its aspects, and embodiments are not limited to the specific components, assembly processes, or method elements disclosed herein. Many additional components, assembly processes, and / or method elements known in the art that are suitable for an image sensor device will be apparent for use with specific embodiments of the present disclosure. Thus, for example, although the present invention discloses specific embodiments, such embodiments and implementation components may include any shape, size, style, type, model, version, measure, concentration, material, quantity, method element, step, etc. known in the art for such image sensor devices and implementation components and methods that are suitable for the intended operation and method.

[0031] Reference Figure 1 , shows a cross-sectional side view of an image sensor device. The image sensor device 2 includes a rear side 4 and a front side 6. The image sensor device 2 may be configured to receive light from the rear side of the device, as indicated by arrow 100. The image sensor device includes a semiconductor die 8. In various embodiments, the semiconductor die 8 includes a silicon layer 10. In other embodiments, the semiconductor die 8 may include layers having silicon dioxide, glass, silicon-on-insulator, gallium arsenide, sapphire, ruby, silicon carbide, polycrystalline or amorphous forms of any of the foregoing, and any other type of layer for constructing an image sensor or semiconductor device. In embodiments including the silicon layer 10, the silicon layer may include a photodiode array 20 therein.

[0032] The image sensor device 2 includes a contact layer 12 having a first surface 24 and a second surface 26. In various embodiments, the contact layer may be considered part of the semiconductor die 8, or it may be considered separate from but coupled to the semiconductor die 8. As used herein, the contact layer 12 is considered part of the semiconductor die 8 and is not considered to be separated from the material of the semiconductor die 8. In various embodiments, the contact layer 12 may be an interlayer dielectric (ILD) material 18. The contact layer 12 may also include one or more metal layers 14 therein. The metal layer 14 may include one or more metal landing pads 16. In various embodiments, the metal layer 14 and / or the metal landing pad 16 may include aluminum, copper, tungsten, any other metal, and any combination thereof. In various embodiments, the contact layer 12 may include one or more diffusion barrier layers 34. In a particular embodiment, the one or more diffusion barrier layers may be adjacent to the back side / first surface 58 and / or the front side / second surface 60. The diffusion barrier layer 34 may include SiN or any other material used in a diffusion barrier layer. The contact layer 12 may include other elements 22 therein, such as gates or other semiconductor elements. In various embodiments, and as shown, the front side 26 of the contact layer 12 may be coupled to the second semiconductor die 28. The second semiconductor die 28 may include a plurality of layers therein, including layers 30 and 32. The second semiconductor die 28 may be the same or similar to any type of semiconductor die disclosed herein or understood by those skilled in the art.

[0033] Still referring Figure 1 , the semiconductor die 8 includes a first through-silicon via (TSV) 32 that extends from the back side 4 of the image sensor device 2 and into the silicon layer 10. In a particular embodiment, and as shown, the first TSV 32 may extend through the silicon layer 10 and into the contact layer 12. In various embodiments, the first TSV 32 may also extend into the contact layer 12 and, in some embodiments, may extend all the way to the metal landing pad. In various embodiments, the pinning layer 38 may be coupled to the sidewall 36 of the first TSV, the first surface 40 (or back side) of the semiconductor die 8, and / or a portion of the base 42 of the first TSV 32. As a non-limiting example, the pinning layer 38 may include HfO2, Ta2O5, or a combination thereof. The pinning layer may inhibit the transfer of the pinning voltage therethrough. In a particular embodiment, the pinning layer may be directly coupled to the sidewall 36 of the first TSV, the first surface 40 of the semiconductor die 8, and / or a portion of the base 42 of the first TSV 32.

[0034] In various embodiments, an anti-reflection (AR) layer 44 may be coupled to the sidewall 36 of the first TSV, the first surface 40 of the semiconductor die 8, and / or a portion of the base 42 of the first TSV 32. As a non-limiting example, the AR layer 44 may include SiO2 or any other material for preventing light reflection. In a particular embodiment, and as Figure 1 shown, the AR layer 44 may be directly coupled on the pinned layer 38. In other embodiments, the image sensor device may not include the pinned layer 38, and the AR layer 44 may be directly coupled to the sidewall 36 of the first TSV, the first surface 40 of the semiconductor die 8, and / or a portion of the base 42 of the first TSV 32. In embodiments where the first TSV extends all the way to the metal landing pad, the image sensor device may not include more TSVs other than the first TSV. In such embodiments, a diffusion barrier layer may be coupled within the TSV and may be directly coupled to the metal landing pad.

[0035] In various embodiments, and as Figure 1 shown, the image sensor device 2 may include a second TSV 46. The second TSV 46 may be formed within the first TSV 32 (within the perimeter of the first TSV 32) and extend into the semiconductor die 8 material. As shown, the width of the second TSV 46 is less than the width of the first TSV 32. In various embodiments, if the first TSV 32 does not extend completely through the silicon layer, the second TSV 46 may partially extend through the silicon layer 10. The second TSV 46 may also extend into the contact layer 12. In a particular embodiment, the second TSV 46 extends into the metal landing pad 16 within the contact layer 12. In various embodiments, a metal layer 48 may be applied within the second TSV 46. The metal layer 48 may be any type of metal diffusion barrier layer, which by non-limiting example includes Ti, TiN, Al, W, Cu, Ta, TaN, and any combination thereof. In such embodiments, the metal layer 48 may be indirectly or directly coupled to the sidewall of the second TSV and / or the base 50 of the second TSV. The metal layer 48 may also serve as a mobile ion barrier, a moisture barrier, a hydrogen barrier, and as a barrier against any other contaminants of materials entering the second TSV 46 or the die itself. The metal layer 48 may also be coupled to a portion of the base 42 of the first TSV 32, and in embodiments having the pinned layer 38 and / or the AR layer 44, the metal layer may be coupled on the pinned layer and / or the AR layer within the first TSV. The metal layer 48 may extend along a portion of the rear side 4 of the image sensor device 2. In various embodiments, a sealant may be used instead of the metal layer 48.

[0036] Still referring to Figure 1, the image sensor device 2 may include one or more shallow trench isolation (STI) regions 52 within the semiconductor die 8. In various embodiments, the STI regions 52 may be formed within the silicon layer 10. The STI regions 52 may be adjacent to or in contact with the sidewalls 36 of the first TSV 32. In a particular embodiment, the STI regions 52 may be formed adjacent to a corner formed between the sidewalls 36 of the first TSV 32 and the base 42 of the first TSV. In other embodiments, the STI regions 52 may be formed below the first TSV 32. In other embodiments, the semiconductor die 8 may include regions that are doped opposite to the doping of the silicon layer 10, instead of the STI regions. As an example, if the silicon layer 10 is p-doped, the regions that replace the STI regions may be n- or n+-doped.

[0037] The image sensor device 2 includes a TSV edge seal ring 62. As a non-limiting example, the TSV edge seal ring 62 may be tungsten, copper, silver, gold, any other metal, any other metal alloy, or any combination thereof. In a particular embodiment, the TSV edge seal ring 62 may be formed of tungsten. As shown, the TSV edge seal ring 62 is within the contact layer 12. In such an embodiment, the TSV edge seal ring 62 may surround the second TSV 46 in the contact layer 12. In other embodiments, the TSV edge seal ring 62 may be partially within the silicon layer 10. In various embodiments, the TSV edge seal ring may extend from the first surface 58 of the contact layer 12 into the contact layer to a depth that is coextensive with the depth of the second TSV 46. In a similar embodiment, the TSV edge seal ring 62 may extend from the base 42 of the first TSV, or a position that is coextensive with the depth of the base of the first TSV, to a depth that is coextensive with the depth of the second TSV 46. In a particular embodiment, the TSV edge seal ring may be directly coupled to the metal landing pad 16. The TSV edge seal ring may also be directly coupled to the diffusion barrier layer 34 and / or one or more STI regions 52. Figure 1 As shown, and as combined later Figure 3 As described above, the perimeter of the TSV edge seal ring 62 may be larger than the perimeter of the first TSV. In such embodiments, the STI region 52 and / or the diffusion barrier layer 34 may cover the gap between the edge of the first TSV 32 and the TSV edge seal ring 62 to prevent any contaminants from entering the area directly surrounding the interface between the second TSV 46 and the metal landing pad 16.

[0038] refer to Figure 3 , illustrates a top view of a portion of a first embodiment of an image sensor device showing the relationship between a first TSV, a second TSV, and a TSV edge seal ring. Figure 3 The top view corresponds to Figure 1, since the TSV edge seal ring 64 has the largest perimeter, the perimeter of the first TSV 66 is just less than and within the perimeter of the TSV edge seal ring 64, and the second TSV 68 has the smallest perimeter and is located in the center of the first TSV 64. In various embodiments, the distance between the perimeters of the TSV edge seal ring 64, the first TSV 66, and the second TSV 68 can vary. However, in a particular embodiment and as shown, the perimeter of the first TSV 66 is made to be only slightly less than the perimeter of the TSV edge seal ring 64 to leave room for a small barrier (STI region or diffusion barrier layer) between the perimeter of the TSV edge seal ring and the perimeter of the first TSV. Refer to Figure 4 , a top view showing a part of a second embodiment of an image sensor device, which shows the relationship between a first TSV 72, a second TSV 74, and a TSV edge seal ring 70.

[0039] Compared with Figure 3 , in various embodiments, the perimeter of the first TSV 72 can be greater than the perimeter of the TSV edge seal ring 70, and the perimeter of the TSV edge seal ring 70 can be greater than the perimeter of the second TSV 72. In Figure 4 the embodiment shown, the TSV edge seal ring 70 is formed below the first TSV 72. As Figure 4 shown, the TSV edge seal ring 70 is positioned closer to the perimeter of the first TSV 72 and farther from the perimeter of the second TSV 74. However, in other embodiments, the TSV edge seal ring can be positioned anywhere between the perimeter of the first TSV 72 and the perimeter of the second TSV 74. Refer to Figure 5 , a top view showing a part of a third embodiment of an image sensor device, which shows the relationship between a first TSV 76, a second TSV 80, and a TSV edge seal ring 78. In various embodiments, the perimeter of the first TSV 76 can have the same size and shape as the perimeter of the TSV edge seal ring 78. In such embodiments, the perimeter of the first TSV 76 can be aligned with the perimeter of the TSV edge seal ring 78. Similar to Figure 4 the embodiment shown, the TSV edge seal ring 78 can be formed below the edge of the first TSV 76. The perimeter of the second TSV 80 can be less than the perimeters of the first TSV 76 and the TSV edge seal ring 78.

[0040] In an embodiment having only a single TSV extending to a metal landing pad, a TSV edge seal ring can surround the portion of the TSV in the contact layer. In such an embodiment, the perimeter of the TSV edge seal ring is greater than the perimeter of the first TSV. If there is a gap, the STI region and / or diffusion barrier layer can cover the gap between the TSV and the TSV edge seal ring. Thus, in embodiments having a single TSV or embodiments having first and second TSVs, the TSV edge seal ring 62 provides a barrier for the interface between the TSV coupled to the metal landing pad and the metal landing pad 16. Specifically, by way of non-limiting example, the TSV edge seal ring 62 can serve as a barrier to moisture, mobile ions, and hydrogen.

[0041] Reference Figure 2 , a cross-sectional side view of another embodiment of an image sensor device is shown. The image sensor device 82 is similar to Figure 1 the image sensor device 2. The main difference is that the TSV edge seal ring 84 is physically isolated from the material of the metal landing pad 86. As Figure 2 shown, the TSV edge seal ring 84 is directly coupled to one or more metal pads 88. One or more gaps 90 physically isolate the one or more metal pads 88 and thus the TSV edge seal ring 84 from the metal landing pad 86. In such an embodiment, to inhibit moisture, hydrogen, ions, or other contaminants from entering the region 92 directly surrounding the interface 96 between the second TSV 94 and the metal landing pad 86, the image sensor device can include an additional diffusion barrier layer 98. The diffusion barrier layer 98 can be any type of diffusion barrier layer disclosed herein. The diffusion barrier layer 98 can be directly coupled to the metal landing pad 86 and the one or more metal pads 88. The diffusion barrier layer 98 can also be a barrier to prevent contaminants from entering through the one or more gaps 90.

[0042] In various embodiments, a method of forming Figure 1 or Figure 2 the image sensor device can include forming the desired metal layer, metal landing pad, diffusion barrier layer, TSV edge seal ring, and any other elements in the contact layer (which can be an ILD). In various embodiments, the TSV edge seal ring can be directly coupled to the metal landing pad and can even be the same material as the metal landing pad. In a particular embodiment, the TSV edge seal ring can be formed as a single continuous piece with the metal landing pad. In other embodiments, the TSV edge seal ring can be physically isolated from the metal landing pad, similar to Figure 2The embodiments shown. The method may include coupling a wafer to a contact layer. The wafer may include a silicon layer (or any other die / wafer material previously disclosed herein) having an array of photodiodes coupled to the contact layer. The wafer may also include a plurality of STIs or retrograde doped regions. In various embodiments, the method includes thinning the wafer from the back side of the wafer to a desired thickness. The wafer may then be patterned, and TSVs may be formed in the wafer. In embodiments having STIs or retrograde doped regions, the edges of the TSVs may be configured to define such regions. The TSVs are formed from the back side of the device. The width and length of the TSVs may be configured to allow the perimeter of the TSVs to be smaller and fit within the perimeter of the TSV edge seal ring, larger and surround the perimeter of the TSV edge seal ring, or aligned with the perimeter of the TSV edge seal ring. The TSVs may be formed through the silicon layer (or other wafer material). In various embodiments (such as embodiments having two TSVs), the TSVs do not extend into the contact layer, whereas in other embodiments, the TSVs do extend into the contact layer and may even extend to a metal landing pad within the contact layer. The method may include depositing a pinning layer on the back side of the wafer and within the TSVs. The pinning layer may coat the sidewalls and base of the TSVs. Similarly, the method may include depositing an AR layer on the back side of the wafer and within the TSVs. In embodiments having a pinning layer, the AR layer may be deposited on the pinning layer.

[0043] In embodiments where the TSVs do not extend to the metal landing pad, the method may include patterning the base of the existing TSVs and forming second TSVs therein. In various embodiments, the second TSVs may have a smaller width than the existing first TSVs and may extend into the contact layer (and through the pinning layer and AR layer (if they exist)) and to the metal landing pad. In various embodiments, the method may include forming a diffusion barrier layer within the second TSVs. In addition to coating the base and sidewalls of the second TSVs, the diffusion barrier layer may also coat the interior of the first TSVs and may extend onto the back side of the wafer.

[0044] In various embodiments, the backside metal may be coupled to the back side of the image sensor device, such as by way of non-limiting examples copper, silver, gold, aluminum, nickel, tungsten, or any other metal, metal alloy, or combination thereof. The method includes dicing the wafer. The diced image sensor device (or the wafer prior to dicing) may be hydrogen annealed.

[0045] In various embodiments, the TSV edge seal ring may include tungsten.

[0046] In various embodiments, the anti-reflection layer may be coupled to one or more sidewalls of the TSVs.

[0047] In various embodiments, the pinning layer may be directly coupled to one or more sidewalls of the first TSV.

[0048] In various embodiments, the perimeter of the TSV edge seal ring is aligned with the perimeter of the first TSV.

[0049] In various embodiments, the perimeter of the TSV edge seal ring is greater than the perimeter of the first TSV.

[0050] In various embodiments, the perimeter of the TSV edge seal ring is less than the perimeter of the first TSV.

[0051] In various embodiments, the TSV edge seal ring may be directly coupled to the diffusion barrier layer.

[0052] In various embodiments, the TSV edge seal ring is directly coupled to one or more shallow trench isolation (STI) regions.

[0053] Where specific embodiments of the image sensor device and the implementation components, sub-components, methods, and sub-methods are mentioned in the above description, it should be apparent that various modifications can be made without departing from the essence of the present invention, and these embodiments, implementation components, sub-components, methods, and sub-methods can be applied to other image sensor devices.

Claims

1. An image sensor device, comprising: Through-Silicon Via (TSV), the TSV is formed in the rear side of the image sensor device and extends through the material of the die to a metal landing pad, wherein the metal landing pad is within a contact layer; TSV edge seal ring, the TSV edge seal ring surrounds a portion of the TSV in the contact layer and extends only from a first surface of the contact layer into the contact layer to a depth coextensive with the depth of the TSV; Pinning layer, the pinning layer covers one or more sidewalls of the TSV and a first surface of the die; and Anti-reflection layer, the anti-reflection layer is directly coupled on the pinning layer.

2. The image sensor device according to claim 1, wherein the TSV edge seal ring is directly coupled to the metal landing pad.

3. The image sensor device according to claim 1, wherein the TSV edge seal ring is physically isolated from the metal landing pad.

4. The image sensor device according to claim 1, wherein the pinned layer is directly coupled to the one or more sidewalls of the TSV.

5. An image sensor device, comprising: Through-Silicon Via (TSV), the TSV is formed in the rear side of the image sensor device and extends through the material of the die to a metal landing pad, wherein the metal landing pad is within a contact layer; TSV edge seal ring, the TSV edge seal ring surrounds a portion of the TSV in the contact layer and extends only from a first surface of the contact layer to the metal landing pad; Pinning layer, the pinning layer covers one or more sidewalls of the TSV and a first surface of the die; and Anti-reflection layer, the anti-reflection layer is directly coupled on the pinning layer.

6. The image sensor device according to claim 5, wherein the TSV edge seal ring is directly coupled to the diffusion barrier layer.

7. The image sensor device according to claim 5, wherein the TSV edge seal ring is directly coupled to one or more shallow trench isolation STI regions.

8. An image sensor device, comprising: First Through-Silicon Via (TSV), the first TSV is formed in the image sensor device, extends from the rear side of the image sensor device into the material of the die to reach a contact layer; Pinning layer, the pinning layer covers one or more sidewalls of the first TSV and a first surface of the die; Anti-reflection layer, the anti-reflection layer is directly coupled on the pinning layer; Second TSV, the second TSV is formed within the first TSV and extends into the material of the die to reach a metal landing pad, wherein the metal landing pad is within a contact layer; and TSV edge seal ring, the TSV edge seal ring is within the contact layer, surrounds the second TSV in the contact layer, and extends from a first surface of the contact layer into the contact layer to a depth coextensive with the depth of the second TSV, wherein the TSV edge seal ring is physically isolated from the metal landing pad.

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