Backside illuminated image sensor device

A backside illuminated (BSI) image sensor device includes a device layer, a doped isolation region and a doped radiation sensing region. The device layer has a front side and a backside, in which the device layer has a thickness greater than or equal to 4 μm. The doped isolation region having a first dopant of a first conductivity is through the device layer to define a plurality of pixel regions of the device layer, in which the doped isolation region includes a first upper region adjacent to the front side and a first lower region between the first upper region and the backside, and the first upper region has a width less than a width of the first lower region. The doped radiation sensing region having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions of the device layer.

BACKGROUND

Image sensors are used to sense radiation such as light. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital camera or mobile phone camera applications.

A typical image sensor includes various optical and electronic elements formed on a front side of the sensor. The optical elements include at least an array of individual pixels to capture light incident on the image sensor, while the electronic elements include transistors. Although the optical and electronic elements are formed on the front side, an image sensor can be operated as a frontside illuminated (FSI) image sensor or a backside illuminated (BSI) image sensor. In an FSI image sensor, light to be captured by the pixels in the pixel array is incident on the front side of the sensor, while in a BSI image sensor, the light to be captured is incident on the back side of the sensor.

DETAILED DESCRIPTION

As mentioned above, although the optical and electronic elements are formed on the front side, an image sensor can be operated as a frontside illuminated (FSI) image sensor or a backside illuminated (BSI) image sensor. Compared with the FSI image sensors, the BSI image sensors have advantages of low cost, tiny size and high integration. The BSI image sensors also have advantages of low operating voltage, low power consumption and high quantum efficiency. Therefore, the BSI image sensors are adopted broadly in electronic products.

However, for some applications, such as for sensing non-visible infrared light (e.g., near infrared light), a thickness of the device layer should be increased. Therefore, the present application provides a BSI image sensor device for sensing non-visible infrared light, in which the BSI image sensor device has a device layer with a thickness greater than or equal to 4 μm and a doped isolation region with a specific shape. Embodiments of each element of the BSI image sensor device will be described below in detail.

FIG. 1is a cross-sectional view of a BSI image sensor device10in accordance with some embodiments of the present disclosure. The BSI image sensor device10includes a device layer100, a doped isolation region110in the device layer100and a doped radiation sensing region120in the device layer100.

In some embodiments, the device layer100is a silicon device layer doped with a dopant, such as a p-type dopant (e.g., boron), and such device layer may be called as a p-type device layer. Alternatively, in some embodiments, the device layer100is a silicon device layer doped with an n-type dopant (e.g., phosphorous or arsenic), and such device layer may be called as an n-type device layer. In some embodiments, the device layer100includes other elementary semiconductors such as germanium and diamond. In some embodiments, the device layer100includes a compound semiconductor and/or an alloy semiconductor. In some embodiments, the device layer100includes an epitaxial layer (epi layer). In some embodiments, the device layer100is an epitaxial layer.

The device layer100has a front side (also referred to as a front surface)100aand a back side (also referred to as a back surface)100bopposite to the front side100a. In some embodiments, for the BSI image sensor device10, radiation is projected from the back surface100b. In some embodiments, the reversed device (i.e., the BSI image sensor device)10is supported by a carrier substrate170(e.g., a carrier wafer). In some embodiments, the device layer100has a thickness t1 greater than or equal to 4 μm for sensing non-visible infrared light. In some embodiments, the thickness t1 is greater than or equal to 4.5 or 5 μm.

The doped isolation region110having a first dopant of a first conductivity is through the device layer100to define a plurality of pixel regions100cof the device layer100. In some embodiments, the first dopant of the doped isolation region110has the same conductivity as the dopant of the device layer100. In some embodiments, the doped isolation region110includes a p-type dopant, such as boron. In some embodiments, the doped isolation region110is a p-type doped region. In some embodiments, the doped isolation region110is formed by one or more ion implantation processes and diffusion processes.

In some embodiments, the doped isolation region110includes a first upper region110aadjacent to the front side100aand a first lower region110bbetween the first upper region110aand the back side100b. In some embodiments, the first upper region110ais in contact with the front side100a. In some embodiments, the first lower region110bis in contact with the back side100band connected to the first upper region110a. In some embodiments, the first upper region110ais elongated substantially along a thickness direction of the device layer100. In some embodiments, the first lower region110bis elongated along the thickness direction of the device layer100.

The first upper region110ahas a width w11 less than a width w12 of the first lower region110b, as shown inFIG. 1. In some embodiments, a ratio of the width w11 of the first upper region110ato the width w12 of the first lower region110bis greater than or equal to 1:10 and less than 1:1. In some embodiments, the width w11 of the first upper region110ais 5 to 30% based on the total thickness t1 of the device layer100. In some embodiments, the width 12 of the first lower region110bis 20 to 60% based on the total thickness t1 of the device layer100.

In some embodiments, a ratio of a depth d11 of the first upper region110ato a depth d12 of the first lower region110bis in a range of 1:10 to 2:1. In some embodiments, the depth d11 of the first upper region110ais greater than or equal to 10% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100. In some embodiments, the depth d12 of the first lower region110bis greater than or equal to 50% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100.

The doped radiation sensing region120having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions100cof the device layer100. In some embodiments, as shown inFIG. 1, the doped radiation sensing regions120are respectively in the pixel regions100cof the device layer100. In some embodiments, the second dopant of the doped radiation sensing region120has different conductivity of the dopant of the device layer100. In some embodiments, the doped radiation sensing region120includes an n-type dopant, such as phosphorous or arsenic. In some embodiments, the doped radiation sensing region120is an n-type doped region. In some embodiments, the doped radiation sensing region120is formed by one or more ion implantation processes and diffusion processes. In some embodiments, the doped isolation region110is separated from the doped radiation sensing region120.

For the BSI image sensor device10, the doped radiation sensing regions120respectively in the pixel regions100care operable to detect radiation, such as an incident light, which is projected toward the device layer100from the back side100b. In some embodiments, the doped radiation sensing region120includes a photodiode.

In some embodiments, the doped radiation sensing region120includes a second upper region120aadjacent to the front side100aand a second lower region120bbetween the second upper region120aand the back side100b. In some embodiments, the second upper region120ais in contact with the front side100a. In some embodiments, the second lower region120bis in contact with the back side100band connected to the second upper region120a. In some embodiments, the second upper region120ais elongated substantially along the thickness direction of the device layer100. In some embodiments, the second lower region120bis elongated substantially along the thickness direction of the device layer100.

In some embodiments, the second upper region120ahas a width w21 greater than or equal to a width w22 of the second lower region120b. In some embodiments, a ratio of the width w21 of the second upper region120ato the width w22 of the second lower region120bis in a range of 1:1 to 10:1. In some embodiments, the width w21 of the second upper region120ais greater than or equal to 60% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100. In some embodiments, the width w22 of the second lower region120bis 20 to 80% based on the total thickness t1 of the device layer100.

In some embodiments, the width w21 of the second upper region120ais greater than the width w22 of the second lower region120b, as shown inFIG. 1.FIG. 2is a cross-sectional view of a BSI image sensor device20in accordance with some embodiments of the present disclosure. In some embodiments, the width w21 of the second upper region120ais equal to the width w22 of the second lower region120b, as shown inFIG. 2.

In some embodiments, a ratio of a depth d21 of the second upper region120ato a depth d22 of the second lower region120bis in a range of 1:10 to 2:1. In some embodiments, the depth d21 of the second upper region120ais greater than or equal to 10% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100. In some embodiments, the depth d22 of the second lower region120bis greater than or equal to 50% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100.

In some embodiments, a ratio of the width w11 of the first upper region110ato the width w21 of the second upper region120ais in a range of 1:20 to 1:3. In some embodiments, a ratio of the width w12 of the first lower region110bto the width w22 of the second lower region120bis in a range of 1:10 to 10:1.

In some embodiments, a ratio of the depth d11 of the first upper region110ato the depth d21 of the second upper region120ais in a range of 1:3 to 3:1. In some embodiments, the depth d11 of the first upper region110ais greater than the depth d21 of the second upper region120a, as shown inFIG. 1. In some embodiments, a ratio of the depth d12 of the first lower region110bto the depth d22 of the second lower region120bis in a range of 1:3 to 3:1.

In some embodiments, the BSI image sensor device10further includes a deep trench isolation (DTI) structure130in the doped isolation region110. In some embodiments, the deep trench isolation structure130is in the first lower region110bof the doped isolation region110. In some embodiments, the deep trench isolation structure has a depth d3 greater than or equal to 2 μm. In some embodiments, the depth d3 of the deep trench isolation structure130is more than half the thickness t1 of the device layer100. In some embodiments, the deep trench isolation structure130has a surface130acoplanar with the back side100b. In some embodiments, the deep trench isolation structure130has two ends opposite to each other, and one end (not marked) of the deep trench isolation structure130adjacent to the back side110bhas a width w31 greater than a width w32 of the other end (not marked) of the deep trench isolation structure130adjacent to the front side100a. In some embodiments, the deep trench isolation structure130has a width w31 or w32 less than a width w12 of the first lower region of the doped isolation region. In some embodiments, the BSI image sensor device10further includes a metal grid180in contact with the deep trench isolation structure130.

In some embodiments, the BSI image sensor device10further includes a passivation layer190covering the metal grid180. In some embodiments, the passivation layer190includes a dielectric material such as silcon oxide. In some embodiments, the passivation layer190includes silicon nitride. In some embodiments, passivation layer190is formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or other suitable processes.

In some embodiments, the BSI image sensor device10further includes a transistor140in contact with the front side100aof the device layer100. In some embodiments, the transistor140is in contact with the first upper region110a. In some embodiments, the transistor140is a MOS transistor.

In some embodiments, the BSI image sensor device10further includes an interconnect structure150covering the transistor140. In some embodiments, the interconnect structure150includes a plurality of patterned dielectric layers (not shown) and conductive layers (not shown) that provide interconnections (e.g., wiring). In some embodiments, the interconnect structure150includes an interlayer dielectric (ILD) (not shown) and a multilayer interconnect (MLI) structure (not shown). In some embodiments, the MLI structure includes contacts, vias and metal lines.

In some embodiments, the BSI image sensor device10further includes a passivation layer160covering the interconnect structure150. In some embodiments, the passivation layer160includes a dielectric material such as silcon oxide. In some embodiments, the passivation layer160includes silicon nitride. In some embodiments, passivation layer160is formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) or other suitable processes.

In some embodiments, the carrier substrate170covers the passivation layer160. In some embodiments, the carrier substrate170includes a silicon material. In some embodiments, the carrier substrate170includes a glass substrate or another suitable material.

The present application further provides a BSI image sensor device for sensing non-visible infrared light, in which the BSI image sensor device has a device layer with a thickness greater than or equal to 4 μm and a doped radiation sensing region with a specific shape. Embodiments of each element of the BSI image sensor device will be described below in detail.

FIG. 3is a cross-sectional view of a BSI image sensor device30in accordance with some embodiments of the present disclosure. The BSI image sensor device30includes a device layer100, a doped isolation region110in the device layer100and a doped radiation sensing region120in the device layer100.

In some embodiments, the device layer100is a silicon device layer doped with a dopant, such as a p-type dopant (e.g., boron), and such device layer may be called as a p-type device layer. Alternatively, in some embodiments, the device layer100is a silicon device layer doped with an n-type dopant (e.g., phosphorous or arsenic), and such device layer may be called as an n-type device layer. In some embodiments, the device layer100includes other elementary semiconductors such as germanium and diamond. In some embodiments, the device layer100includes a compound semiconductor and/or an alloy semiconductor. In some embodiments, the device layer100includes an epitaxial layer (epi layer). In some embodiments, the device layer100is an epitaxial layer.

The device layer100has a front side (also referred to as a front surface)100aand a back side (also referred to as a back surface)100bopposite to the front side100a. In some embodiments, for the BSI image sensor device30, radiation is projected from the back surface100b. In some embodiments, the reversed device (i.e., the BSI image sensor device)30is supported by a carrier substrate170(e.g., a carrier wafer). In some embodiments, the device layer100has a thickness t1 greater than or equal to 4 μm for sensing non-visible infrared light. In some embodiments, the thickness t1 is greater than or equal to 4.5 or 5 μm.

The doped isolation region110having a first dopant of a first conductivity is through the device layer100to define a plurality of pixel regions100cof the device layer100. In some embodiments, the first dopant of the doped isolation region110has the same conductivity as the dopant of the device layer100. In some embodiments, the doped isolation region110includes a p-type dopant, such as boron. In some embodiments, the doped isolation region110is a p-type doped region. In some embodiments, the doped isolation region110is formed by one or more ion implantation processes and diffusion processes.

The doped radiation sensing region120having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions100cof the device layer100. In some embodiments, the second dopant of the doped radiation sensing region120has different conductivity of the dopant of the device layer100. In some embodiments, the doped radiation sensing region120includes an n-type dopant, such as phosphorous or arsenic. In some embodiments, the doped radiation sensing region120is an n-type doped region. In some embodiments, the doped radiation sensing region120is formed by one or more ion implantation processes and diffusion processes. In some embodiments, the doped isolation region110is separated from the doped radiation sensing region120.

For the BSI image sensor device30, the doped radiation sensing regions120respectively in the pixel regions100care operable to detect radiation, such as an incident light, which is projected toward the device layer100from the back side100b. In some embodiments, the doped radiation sensing region120includes a photodiode.

The doped radiation sensing region120includes a second upper region120aadjacent to the front side100aand a second lower region120bbetween the second upper region120aand the back side100b. In some embodiments, the second upper region120ais in contact with the front side100a. In some embodiments, the second lower region120bis in contact with the back side100band connected to the second upper region120a. In some embodiments, the second upper region120ais elongated substantially along a thickness direction of the device layer100. In some embodiments, the second lower region120bis elongated substantially along the thickness direction of the device layer100.

The second upper region120ahas a width w21 greater than width w22 of the second lower region120b, as shown inFIG. 3. In some embodiments, a ratio of the width w21 of the second upper region120ato the width w22 of the second lower region120bis greater than 1:1 and less than or equal to 10:1. In some embodiments, the width w21 of the second upper region120ais greater than or equal to 60% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100. In some embodiments, the width w22 of the second lower region120bis 20 to 80% based on the total thickness t1 of the device layer100.

In some embodiments, a ratio of a depth d21 of the second upper region120ato a depth d22 of the second lower region120bis in a range of 1:10 to 2:1. In some embodiments, the depth d21 of the second upper region120ais greater than or equal to 10% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100. In some embodiments, the depth d22 of the second lower region120bis greater than or equal to 50% based on the total thickness t1 of the device layer100and less than 100% based on the total thickness t1 of the device layer100.

In some embodiments, the doped isolation region110includes a first upper region110aadjacent to the front side100aand a first lower region110bbetween the first upper region110aand the back side100b. In some embodiments, the first upper region110ais in contact with the front side100a. In some embodiments, the first lower region110bis in contact with the back side100band connected to the first upper region110a. In some embodiments, the first upper region110ais elongated substantially along the thickness direction of the device layer100. In some embodiments, the first lower region110bis elongated along the thickness direction of the device layer100.

In some embodiments, the first upper region110ahas a width w11 less than or equal to a width w12 of the first lower region110b. In some embodiments, the width w11 is equal to the width 12, as shown inFIG. 3. In some embodiments, the width w11 is less than the width w12, as shown inFIG. 1 or 2. In some embodiments, a ratio of the width w11 of the first upper region110ato the width w12 of the first lower region110bis in a range of 1:10 to 1:1. In some embodiments, the width w11 of the first upper region110ais 5 to 30% based on the total thickness t1 of the device layer100. In some embodiments, the width 12 of the first lower region110bis 20 to 60% based on the total thickness t1 of the device layer100.

In some embodiments, the BSI image sensor device30further includes a deep trench isolation (DTI) structure130in the doped isolation region110. In some embodiments, the deep trench isolation structure has a depth d3 greater than or equal to 2 μm. In some embodiments, the depth d3 of the deep trench isolation structure130is more than half the thickness t1 of the device layer100. In some embodiments, the deep trench isolation structure130has a surface130acoplanar with the back side100b.

The present application further provides a BSI image sensor device for sensing non-visible infrared light, in which the BSI image sensor device has a device layer with a thickness greater than or equal to 4 μm and a deep trench isolation structure with a depth greater than or equal to 2 μm.

As shown inFIG. 1, the BSI image sensor device10includes a device layer100, a doped isolation region110, a deep trench isolation structure130and a doped radiation sensing region120. The device layer100has a front side100aand a back side100b, in which the device layer100has a thickness t1 greater than or equal to 4 μm. The doped isolation region110having a first dopant of a first conductivity is through the device layer100to define a plurality of pixel regions100cof the device layer100. The deep trench isolation structure130is in the doped isolation region110, in which the deep trench isolation structure130has a depth d3 greater than or equal to 2 μm. The doped radiation sensing region120having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions100cof the device layer100.

In some embodiments, the doped isolation region110includes a first upper region110aadjacent to the front side100aand a first lower region110bbetween the first upper region110aand the back side100b, and the first upper region110ahas a width w11 less than a width w12 of the first lower region110b, and the doped radiation sensing region120includes a second upper region120aadjacent to the front side100aand a second lower region120bbetween the second upper region120aand the back side100b, and the second upper region120ahas a width w21 greater than a width w22 of the second lower region120b. In some embodiments, the deep trench isolation structure130is in the first lower region110bof the doped isolation region110.

According to some embodiments, a BSI image sensor device includes a device layer, a doped isolation region and a doped radiation sensing region. The device layer has a front side and a back side, in which the device layer has a thickness greater than or equal to 4 μm. The doped isolation region having a first dopant of a first conductivity is through the device layer to define a plurality of pixel regions of the device layer, in which the doped isolation region includes a first upper region adjacent to the front side and a first lower region between the first upper region and the back side, and the first upper region has a width less than a width of the first lower region. The doped radiation sensing region having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions of the device layer.

According to some embodiments, a BSI image sensor device includes a device layer, a doped isolation region and a doped radiation sensing region. The device layer has a front side and a back side, in which the device layer has a thickness greater than or equal to 4 μm. The doped isolation region having a first dopant of a first conductivity is through the device layer to define a plurality of pixel regions of the device layer. The doped radiation sensing region having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions of the device layer, in which the doped radiation sensing region includes a second upper region adjacent to the front side and a second lower region between the second upper region and the back side, and the second upper region has a width greater than a width of the second lower region.

According to some embodiments, a BSI image sensor device includes a device layer, a doped isolation region, a deep trench isolation structure and a doped radiation sensing region. The device layer has a front side and a back side, in which the device layer has a thickness greater than or equal to 4 μm. The doped isolation region having a first dopant of a first conductivity is through the device layer to define a plurality of pixel regions of the device layer. The deep trench isolation structure is in the doped isolation region, in which the deep trench isolation structure has a depth greater than or equal to 2 μm. The doped radiation sensing region having a second dopant of a second conductivity opposite to the first conductivity is in one of the pixel regions of the device layer.