TWI685983B - Photodiode structure and manufacturing method therefore - Google Patents

Abstract

A photodiode structure including a substrate, at least one protrusion and a photodiode is provided. The substrate has a light sensing region. The protrusion is disposed on the substrate of the light sensing region. The photodiode is disposed in the substrate of the light sensing region.

Description

Photodiode structure and its manufacturing method

The invention relates to a semiconductor structure and a manufacturing method thereof, and particularly relates to an optical diode structure and a manufacturing method thereof.

The photodiode is a common photo sensor, which can be used to sense light. In detail, when the light strikes the photodiode, a photocurrent is generated, and the photointensity received by the photodiode can be known by measuring the photocurrent.

In order to increase the photocurrent, it can be achieved by increasing the optical contact area of the photodiode. The most direct way is to increase the size of the photodiode, but it will relatively increase the pixel size and the wafer area, resulting in increased manufacturing costs. Therefore, how to effectively increase the photocurrent generated when the photodiode is illuminated without increasing the size of the photodiode is the goal of continuous efforts in the industry at present.

The invention provides a photodiode structure and a manufacturing method thereof, which can effectively increase the photocurrent generated when the photodiode is illuminated without increasing the size of the photodiode.

The invention provides a photodiode structure, which includes a substrate, at least one protrusion and a photodiode. The substrate has a light sensing area. The protrusion is disposed on the base of the light sensing area. The photodiode is arranged in the substrate of the light sensing area.

According to an embodiment of the invention, in the above-mentioned photodiode structure, the protrusion may be a member different from the substrate or may be a part of the substrate.

According to an embodiment of the invention, in the above-mentioned photodiode structure, the protruding portion may have an arc surface.

According to an embodiment of the invention, in the above-mentioned photodiode structure, the material of the protrusion may be a light-transmitting material.

According to an embodiment of the invention, in the above-mentioned photodiode structure, the material of the protrusion is, for example, a semiconductor material or a dielectric material.

According to an embodiment of the invention, in the above-mentioned photodiode structure, the material of the protrusion is, for example, epitaxial silicon, polycrystalline silicon, silicon oxide, or silicon nitride.

According to an embodiment of the present invention, in the above-mentioned photodiode structure, the top-view pattern of the protrusion is, for example, a circle, concentric circles, lines, or a combination thereof.

According to an embodiment of the invention, in the above-mentioned photodiode structure, part of the photodiode may be located in the protrusion.

According to an embodiment of the invention, in the above-mentioned photodiode structure, the portion of the photodiode below the protrusion may have the same contour as the surface of the protrusion.

The invention provides a method for manufacturing an optical diode structure, which includes the following steps. Provide a base. The substrate has a light sensing area. At least one protrusion is formed on the substrate of the light sensing area. A photodiode is formed in the substrate of the light sensing area.

According to an embodiment of the present invention, in the manufacturing method of the above-mentioned photodiode structure, the method for forming the protrusion is, for example, an epitaxial growth method.

According to an embodiment of the present invention, in the manufacturing method of the above-mentioned photodiode structure, the forming method of the protrusion is, for example, a combination of a deposition process, a lithography process and an etching process.

According to an embodiment of the present invention, in the manufacturing method of the above-mentioned photodiode structure, the forming method of the protrusion is, for example, a patterning process on the substrate.

Based on the above, in the photodiode structure and its manufacturing method proposed by the present invention, since the protruding portion can increase the incident light irradiation area, the total amount of incident light irradiated to the photodiode can be increased. In this way, the photocurrent generated when the photodiode is illuminated can be effectively increased without increasing the size of the photodiode. In addition, in the case of maintaining the same photocurrent, the photodiode structure proposed by the present invention can have a smaller size compared to the conventional photodiode structure, thereby reducing the pixel size and thereby reducing the manufacturing cost.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the embodiments are specifically described below in conjunction with the accompanying drawings for detailed description as follows.

1A to 1D are cross-sectional views of a manufacturing process of an optical diode structure according to an embodiment of the invention. 2A to 2C are top views of photodiodes according to some embodiments of the present invention. In FIGS. 2A to 2C, only the substrate 100 and the protrusion 106 in the light sensing region R are marked to clearly represent the top-view pattern of the protrusion 106.

1A, a substrate 100 is provided. The substrate 100 has a light sensing area R. The substrate 100 is, for example, a semiconductor substrate, such as a silicon substrate. There may be an isolation structure 102 in the substrate 100. The isolation structure 102 can be used to define an active area. The isolation structure 102 is, for example, a shallow trench isolation structure (STI). The material of the isolation structure 102 is, for example, silicon oxide.

In addition, the substrate 100 may have a first conductivity type. Hereinafter, the first conductivity type and the second conductivity type described may be one of the P-type conductivity type and the N-type conductivity type and the other. In this embodiment, the first conductivity type is the P-type conductivity type, and the second conductivity type is the N-type conductivity type, but the invention is not limited thereto.

Next, a well 104 may be formed in the substrate 100. The well region 104 may have a first conductivity type (eg, P type). The formation method of the well region 104 is, for example, an ion implantation method.

Then, at least one protrusion 106 is formed on the substrate 100 of the light sensing region R. Since the protrusion 106 can increase the incident light irradiation area, the total amount of incident light irradiated to the subsequently formed photodiode can be increased. In this way, the photocurrent generated when the photodiode is illuminated can be effectively increased without increasing the size of the photodiode to improve the sensitivity to light. In this embodiment, the size of the photodiode refers to the area occupied by the photodiode. The protrusion 106 may have an arc surface, but the invention is not limited thereto. For example, the cross-sectional shape of the protrusion 106 may be semi-spherical.

The protrusion 106 may be a member different from the substrate 100 or may be a part of the substrate 100. The material of the protrusion 106 may be a light-transmitting material. The material of the protrusion 106 is, for example, a semiconductor material or a dielectric material, such as epitaxial silicon, polycrystalline silicon, silicon oxide, or silicon nitride.

For example, when the material of the protrusion 106 is epitaxial silicon, the formation method of the protrusion 106 is, for example, an epitaxial growth method. In this case, the protrusion 106 may be a member different from the base 100. In detail, the method of forming the protrusion 106 may include the following steps. A patterned mask layer (not shown) is formed on the substrate 100, and the patterned mask layer exposes a portion of the substrate 100 where the protrusions 106 are to be formed. The material of the patterned mask layer is, for example, silicon oxide or silicon nitride. Next, a protrusion 106 made of epitaxial silicon is formed on the substrate 100 exposed by the patterned mask layer by a selective epitaxial growth method. Then, the patterned mask curtain layer is removed. In addition, in the process of forming the protrusion 106 by the epitaxial growth method, the dopant in the well region 104 may diffuse into the protrusion 106, so that part of the well region 104 is located in the protrusion 106 (as shown in FIG. 1A ).

When the material of the protrusion 106 is polysilicon, silicon oxide, or silicon nitride, the formation method of the protrusion 106 is, for example, a combination of a deposition process, a lithography process, and an etching process. In this case, due to process factors, the well 104 will not be located in the protrusion 106. In addition, the protrusion 106 may be a member different from the substrate 100.

When the protruding portion 106 is a part of the substrate 100, a method for forming the protruding portion 106 is, for example, a patterning process on the substrate 100. In this case, the protrusion 106 and the substrate 100 may be the same material (eg, semiconductor material), and part of the well 104 may be located in the protrusion 106 (as shown in FIG. 1A ).

In addition, please refer to FIGS. 2A to 2C, the top view pattern of the protrusion 106 is, for example, a circle (FIG. 2A), a concentric circle (FIG. 2B), a line (FIG. 2C), or a combination thereof, but the present invention is not limited to this . In the technical field, the top-view pattern of the protrusion 106 can be adjusted according to product requirements. On the other hand, the number of protrusions 106 is not limited to the number shown in FIGS. 1A, 2A to 2C, as long as the number of protrusions 106 is more than one, it falls within the scope of the present invention.

1B, a dielectric layer 108 can be formed on the substrate 100. The material of the dielectric layer 108 is, for example, silicon oxide. The method of forming the dielectric layer 108 is, for example, a thermal oxidation method.

Next, a gate 110 may be formed on the dielectric layer 108 on one side of the light sensing region R. The gate 110 can be used as a transfer gate of a transfer transistor. The material of the gate 110 is, for example, doped polysilicon. The forming method of the gate electrode 110 is, for example, a combination of a deposition process, a lithography process and an etching process.

1C, a well region 112 may be formed in the substrate 100 of the light sensing region R. The well region 112 may have a second conductivity type (eg, N type). The well region 112 of the second conductivity type can be used as the photodiode PD, whereby the photodiode PD can be formed in the substrate 100 of the light sensing region R. The well 112 and the gate 110 may have overlapping portions. The method of forming the well region 112 is, for example, ion implantation. In this embodiment, the material of the protrusion 106 is a semiconductor material (e.g., epitaxial silicon or polysilicon), and the well region 112 can be formed in the protrusion 106, so that part of the photodiode PD can be located at The protrusion 106. In this way, the photodiode PD can increase the light contact area and fill factor by the protruding portion 106, so that the photocurrent and the sensitivity to light generated when the photodiode PD is illuminated can be further improved. The filling system 數 is defined as the ratio of the effective photosensitive area to the entire pixel size. In other embodiments, when the material of the protrusion 106 is a dielectric material (eg, silicon oxide or silicon nitride, etc.), the well region 112 will not be formed in the protrusion 106.

In addition, the portion of the photodiode PD under the protrusion 106 may have the same contour as the surface of the protrusion 106, thereby increasing the area of the PN junction of the photodiode PD. In the present embodiment, the description of "same" means "substantially the same", and "substantially" means that a slightly tolerable error can exist. Since the photocurrent generated when the photodiode PD is illuminated is proportional to the area of the PN junction, by increasing the area of the PN junction of the photodiode PD, the light generated by the photodiode PD can be further improved Current. In addition, when the area of the PN junction of the photodiode PD increases, the void area of the PN junction also increases, so the full well capacity (FWC) can be increased to further enhance the photodiode The sensitivity of the body PD to light.

1D, a pinning layer 114 may be formed between the well region 112 and the surface of the substrate 100. The pinned layer 114 can be used to reduce noise. The portion of the pinned layer 114 under the protrusion 106 may have the same contour as the surface of the protrusion 106. The pinned layer 114 may have a first conductivity type (eg, P type). The method of forming the pinned layer 114 is, for example, ion implantation. In this embodiment, the material of the protrusion 106 is an example of a semiconductor material, and part of the pinned layer 114 may be formed in the protrusion 106, but the invention is not limited thereto. In other embodiments, when the material of the protrusion 106 is a dielectric material, the pinned layer 114 is not formed in the protrusion 106.

In FIG. 1D, although the photodiode PD takes the pinned photodiode including the well region 112 and the pinning layer 114 as an example, the present invention is not limited thereto. In some embodiments, the photodiode PD may also be a photodiode without the pinning layer 114 (as shown in FIG. 1C).

In this embodiment, the dielectric layer 108 and the gate electrode 110 are formed first, and then the photodiode PD is formed as an example for description, but the invention is not limited thereto. In some embodiments, the photodiode PD may be formed first, and then the dielectric layer 108 and the gate electrode 110 may be formed. In addition, the subsequent process for forming the transfer transistor and the photosensitive element (eg, image sensor) is well known to those skilled in the art and will not be described here.

The optical diode structure 10 of this embodiment will be described below with reference to FIG. 1D. In addition, although the method of forming the photodiode structure 10 is described by taking the above method as an example, the present invention is not limited thereto.

The photodiode structure 10 includes a substrate 100, at least one protrusion 106, and a photodiode PD. The substrate 100 has a light sensing area R. The protrusion 106 is disposed on the substrate 100 of the light sensing area R. The photodiode PD is disposed in the substrate 100 of the light sensing region R. The photodiode PD may include a well region 112, and may further include a pinning layer 114. In some embodiments, the photodiode PD may also be a photodiode without the pinning layer 114 (as shown in FIG. 1C). The photodiode PD well region 112 is located in the substrate 100 of the light sensing region R. The pinned layer 114 is located between the well area 112 and the surface of the substrate 100. In some embodiments, part of the photodiode PD may be located in the protrusion 106. In addition, the photodiode structure 10 may further include at least one of the isolation structure 102 and the well region 104. The isolation structure 102 is disposed in the substrate 100. The well 104 is located in the substrate 100. The photodiode PD may be located in the well 104. In addition, the materials, arrangement methods, conductivity types, forming methods, and effects of the components in the photodiode structure 10 have been described in detail in the foregoing embodiments, and will not be repeated here.

Based on the foregoing embodiment, it can be seen that, in the above-described photodiode structure 10 and the manufacturing method thereof, since the protrusion 106 can increase the incident light irradiation area, the total amount of incident light irradiated to the photodiode PD can be increased. In this way, the photocurrent generated when the photodiode PD is illuminated can be effectively increased without increasing the size of the photodiode PD. In addition, in the case of maintaining the same photocurrent, the photodiode structure PD of the present embodiment can have a smaller size compared to the conventional photodiode structure, thereby reducing the pixel size, thereby reducing the manufacturing cost.

In summary, in the photodiode structure and the manufacturing method thereof in the above embodiments, the photocurrent generated when the photodiode is illuminated can be effectively improved by the protruding portion. In addition, compared with the conventional photodiode structure, the photodiode structure of the above-mentioned embodiment can have a smaller size, thereby reducing the pixel size, thereby reducing the manufacturing cost.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

10‧‧‧Photodiode structure

100‧‧‧ base

102‧‧‧Isolated structure

104, 112‧‧‧ well area

106‧‧‧Projection

108‧‧‧dielectric layer

110‧‧‧Gate

114‧‧‧ nailing layer

PD‧‧‧Photodiode

R‧‧‧Light sensing area

1A to 1D are cross-sectional views of a manufacturing process of an optical diode structure according to an embodiment of the invention. 2A to 2C are top views of photodiodes according to some embodiments of the present invention.

10‧‧‧Photodiode structure

100‧‧‧ base

102‧‧‧Isolated structure

104, 112‧‧‧ well area

106‧‧‧Projection

108‧‧‧dielectric layer

110‧‧‧Gate

114‧‧‧ nailing layer

PD‧‧‧Photodiode

R‧‧‧Light sensing area

Claims (11)

An optical diode structure, comprising: a substrate, wherein the substrate has a light sensing area; at least one protrusion, which is provided on the substrate of the light sensing area and a top-view pattern of the at least one protrusion includes A circle, a concentric circle, a line, or a combination thereof; and a light diode, which are disposed in the substrate of the light sensing area. The photodiode structure as described in item 1 of the patent application range, wherein the at least one protrusion is a member different from the substrate or a part of the substrate. The photodiode structure as described in item 1 of the patent application range, wherein the at least one protrusion has a circular arc surface. The photodiode structure as described in item 1 of the patent application range, wherein the material of the at least one protrusion includes a light-transmitting material. The photodiode structure as described in item 1 of the patent application range, wherein the material of the at least one protrusion includes a semiconductor material or a dielectric material. The photodiode structure as described in item 1 of the patent application range, wherein the material of the at least one protrusion includes epitaxial silicon, polycrystalline silicon, silicon oxide, or silicon nitride. The photodiode structure as described in item 1 of the patent application scope, wherein part of the photodiode is located in the at least one protrusion. The photodiode structure as described in item 1 of the patent application range, wherein a portion of the photodiode below the at least one protrusion has the same contour as the surface of the at least one protrusion. A method for manufacturing an optical diode structure, comprising: providing a substrate, wherein the substrate has a light sensing area; forming at least one protrusion on the substrate of the light sensing area and forming the at least one protrusion The method includes an epitaxial growth method; and forming a photodiode in the substrate of the light sensing area. The method for manufacturing a photodiode structure as described in item 9 of the patent application range, wherein the method for forming the at least one protrusion includes a combination of a deposition process, a lithography process and an etching process. The method for manufacturing a photodiode structure as described in item 9 of the patent application range, wherein the method for forming the at least one protrusion includes a patterning process on the substrate.

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