TW202420415A - Photodiode structure and manufacturing method thereof - Google Patents

Abstract

The present invention provides a manufacturing method of a photodiode structure. The method includes the following steps: providing a substrate; performing an epitaxial process to form a first semiconductor layer on the substrate; performing an active area patterning and etching process to forming a recessed portion on the first semiconductor layer; performing a first coating process to form a first anti-reflection layer on the first semiconductor layer; and performing an ion implantation process to form a second semiconductor layer in the recessed portion pass through the first anti-reflection layer.

Description

Photodiode structure and manufacturing method thereof

The present invention relates to a method for manufacturing a photodiode structure, and more particularly to a method for manufacturing a photodiode structure capable of maintaining high linearity.

Photodiodes are used to receive external light and output corresponding analog electrical signals or switch between different states in the circuit. Currently, photodiodes are widely used in products that require optical measurement. For example, many smart wearable devices use photodiodes to perform corresponding pulse and/or blood oxygen measurement functions.

It is known that in the manufacturing process of photodiodes, the required N-type and P-type semiconductor layers are first formed, and then the anti-reflection layer is coated on the surface of these semiconductor layers. Since the materials and thicknesses used in each anti-reflection layer are different, the process of some anti-reflection layers may need to be performed in a high temperature environment to facilitate the formation of the corresponding anti-reflection layer. However, these semiconductor layers may undergo material changes due to the high temperature of the process, which may easily cause problems such as linearity degradation, thereby affecting the sensing performance of the photodiode.

Therefore, how to design a manufacturing method for a photodiode structure that can improve the above-mentioned problems is indeed a topic worthy of research.

The purpose of the present invention is to provide a method for manufacturing a photodiode structure that can maintain high linearity.

To achieve the above-mentioned object, the manufacturing method of the photodiode structure of the present invention includes the following steps: providing a substrate; performing an epitaxial process to form a first semiconductor layer on the substrate; performing an active region patterning etching process to form a recessed portion on the first semiconductor layer; performing a first coating process to form a first anti-reflection layer on the first semiconductor layer; and performing an ion dotting process to penetrate the first anti-reflection layer and form a second semiconductor layer in the recessed portion.

In one embodiment of the present invention, the first coating process is a high temperature LPCVD process.

In one embodiment of the present invention, the process temperature of the first coating process is not less than 800°C.

In one embodiment of the present invention, the thickness of the first anti-reflection layer is between 25 nm and XX.

In one embodiment of the present invention, the first anti-reflection layer is formed by XXX process.

In one embodiment of the present invention, the following steps are further included: performing a second coating process to form a second anti-reflection layer on the first anti-reflection layer; performing a first metallization process to form a first electrode electrically connected to the substrate; and performing a second metallization process to form a second electrode electrically connected to the second semiconductor layer.

In one embodiment of the present invention, the second coating process is a PVD process, and the process temperature of the second coating process is lower than the process temperature of the first coating process.

In one embodiment of the present invention, the process temperature of the second coating process is not higher than 200°C.

In one embodiment of the present invention, the thickness of the second anti-reflection layer is between XX and XX.

In one embodiment of the present invention, the first semiconductor layer is an N-type semiconductor layer, the second semiconductor layer is a P-type semiconductor layer, the first electrode is a negative electrode, and the second electrode is a positive electrode.

The present invention also includes a photodiode structure using the aforementioned manufacturing method and process.

Accordingly, by performing the high temperature coating process for forming the first reflective layer before forming the second semiconductor layer, the high temperature of the process can be prevented from affecting the formed second semiconductor layer, reducing the possibility of linearity degradation of the second semiconductor layer, thereby maintaining the original sensing performance of the photodiode structure of the present invention.

Since the various aspects and embodiments are only exemplary and non-restrictive, after reading this specification, a person with ordinary knowledge may also have other aspects and embodiments without departing from the scope of the invention. According to the following detailed description and patent application scope, the features and advantages of these embodiments will be more prominent.

In this document, "a" or "an" is used to describe the elements and components described herein. This is only for convenience of explanation and to provide a general meaning for the scope of the present invention. Therefore, unless it is obvious that it is otherwise intended, such description should be understood to include one or at least one, and the singular also includes the plural.

In this article, the terms "first" or "second" and similar ordinal numbers are mainly used to distinguish or refer to the same or similar elements or structures, and do not necessarily imply the order of these elements or structures in space or time. It should be understood that in some cases or configurations, ordinal numbers can be used interchangeably without affecting the implementation of the present invention.

As used herein, the terms "include," "have," or any other similar terms are intended to cover a non-exclusive inclusion. For example, a component or structure having plural elements is not limited to those elements listed herein but may include other elements that are not expressly listed but are generally inherent to the component or structure.

The photodiode structure of the present invention can be applied to smart wearable devices. Smart wearable devices use photodiodes as optical sensors to measure body parameters such as pulse and/or blood oxygen concentration. In order to maintain the stability of signal sensing and the accuracy of subsequent calculation processing, the photodiode needs to maintain high linearity. The aforementioned linearity refers to the ratio of the intensity of the received light source to the photocurrent generated by the photodiode itself as a constant. The smaller the ratio, the higher the linearity. This is explained in advance.

Please refer to Figures 1 to 2B below, where Figure 1 is a flow chart of the manufacturing method of the photodiode structure of the present invention, Figure 2A is a schematic diagram of the structure of the photodiode structure of the present invention before the second semiconductor layer is formed, and Figure 2B is a schematic diagram of the structure of the photodiode structure of the present invention after the second semiconductor layer is formed. As shown in Figures 1 to 2B, the manufacturing method of the photodiode structure of the present invention includes the following steps:

Step S1: providing a substrate.

First, the present invention provides a substrate 10 as a basic structural member of the photodiode structure 1 of the present invention. The substrate 10 can be made of semiconductor material, such as highly doped N-type semiconductor (i.e., N+ semiconductor), but the selection of the aforementioned semiconductor material will vary depending on different design requirements.

Step S2: performing an epitaxial process to form a first semiconductor layer on the substrate.

After providing the substrate 10 in the aforementioned step S1, the present invention can then perform an epitaxy (EPI) process on a surface of one side of the substrate 10 to form a first semiconductor layer 20 on the substrate 10. The first semiconductor layer 20 can utilize a low-doped N-type semiconductor (i.e., N-semiconductor) process, but the selection of the aforementioned semiconductor material will vary depending on different design requirements.

Generally speaking, after the first semiconductor layer 20 is formed, an initial oxidation process is performed on the surface of the exposed side of the first semiconductor layer 20 to form an oxide layer on the surface to be used as an insulating layer. In the manufacturing method of the photodiode structure of the present invention, the same process can also be performed after the first semiconductor layer 20 is formed, but the present invention is not limited thereto.

Step S3: performing an active region patterning etching process to form a recessed portion on the first semiconductor layer.

After forming the first semiconductor layer 20 in the aforementioned step S2, the present invention can then perform an active region patterning etching process on the surface of the exposed side of the first semiconductor layer 20, for example, using a photolithography process to form a necessary active region geometric structure on the first semiconductor layer 20. In the present invention, the first semiconductor layer 20 can at least form a recessed portion 21 after performing the active region patterning etching process, for providing the second semiconductor layer 40 described later (see FIG. 2B ).

Step S4: performing a first coating process to form a first anti-reflection layer on the first semiconductor layer.

After the aforementioned step S3, the present invention can then perform a first coating process on the surface of the exposed side of the first semiconductor layer 20 to form a first anti-reflection layer 30 on the first semiconductor layer 20. The first anti-reflection layer 30 can completely cover the recessed portion 21 of the first semiconductor layer 20. In the present invention, the first coating process adopts a low-pressure chemical vapor deposition (LPCVD) process, and the aforementioned LPCVD process is performed in a high temperature environment. The process temperature of the first coating process is not less than 800°C. For example, in one embodiment of the present invention, the process temperature of the first coating process is about 800°C, but the present invention is not limited thereto. In addition, in one embodiment of the present invention, the first anti-reflection layer is mainly formed by a silicon nitride process that needs to be formed by high temperature, and the thickness of the first anti-reflection layer 30 formed by the first coating process is between 20 and 30 nm. For example, in one embodiment of the present invention, the thickness of the first anti-reflection layer 30 is about 25 nm, but the thickness of the first anti-reflection layer 30 can be changed with different materials or design requirements.

Step S5: performing an ion distribution process to penetrate the first anti-reflection layer and form a second semiconductor layer in the recessed portion.

After forming the first anti-reflection layer 30 in the aforementioned step S4, the present invention can perform an ion dosing process on the location of the recessed portion 21 of the first semiconductor layer 20 to form the second semiconductor layer 40 in the recessed portion 21. Since the ion dosing process has a higher power, the material forming the second semiconductor layer 40 can pass through the first anti-reflection layer 30 and reach the recessed portion 21, thereby forming the second semiconductor layer 40 in the recessed portion 21.

Therefore, it can be seen that since the second semiconductor layer 40 is formed after the first anti-reflection layer 30 that needs to be treated at a high temperature, the second semiconductor layer 40 will not be affected by the high temperature of the first coating process, thereby ensuring the material properties of the second semiconductor layer 40 itself, and further maintaining the high linearity that the photodiode structure of the present invention can provide.

Please refer to FIG. 3 and FIG. 4 together below, where FIG. 3 is another flow chart of the manufacturing method of the photodiode structure of the present invention, and FIG. 4 is an overall schematic diagram of the photodiode structure of the present invention. As shown in FIG. 3 and FIG. 4, the manufacturing method of the photodiode structure of the present invention also includes the following steps:

Step S6: performing a second coating process to form a second anti-reflection layer on the first anti-reflection layer.

After forming the second semiconductor layer 40 in the aforementioned step S5, the present invention can then perform a second coating process on the surface of the exposed side of the first anti-reflection layer 30 to form the second anti-reflection layer 50 on the first anti-reflection layer 30. In the present invention, the second coating process adopts a physical vapor deposition (PVD) process, and the process temperature of the aforementioned PVD process is lower than the process temperature of the first coating process, wherein the process temperature of the second coating process is a temperature that does not affect the material properties of the second semiconductor layer 40 itself. The process temperature of the second coating process is not higher than 200°C. For example, in one embodiment of the present invention, the process temperature of the second coating process is about 200°C, but the present invention is not limited thereto. In addition, in one embodiment of the present invention, the second anti-reflection layer 50 is mainly formed by PVD process. Therefore, even if the second coating process is performed after the second semiconductor layer 40 is formed, the second semiconductor layer 40 will not be affected by the process temperature of the second coating process and change its material properties.

Generally speaking, after the second anti-reflection layer 50 is formed, other single or multiple coating processes can be selected to be executed according to different design requirements to further form more layers of anti-reflection layers on the exposed side surface of the second anti-reflection layer 50, and the materials and processes used for these anti-reflection layers are also different from the aforementioned first coating process and second coating process; however, the process temperature of these anti-reflection layers is also a temperature that does not affect the material properties of the second semiconductor layer 40 itself.

Step S7: Perform a first metallization process to form a first electrode electrically connected to the substrate.

After forming the second anti-reflection layer 50 in the aforementioned step S6, the present invention can then perform a first metallization process on the other exposed side surface of the substrate 10 to form a first electrode 60 on the other side of the substrate 10. In other words, in terms of structure, the first electrode 60 is formed below the substrate 10. In the present invention, the first electrode 60 is a negative electrode, but the present invention is not limited thereto.

Step S8: Perform a second metallization process to form a second electrode electrically connected to the second semiconductor layer.

After forming the second semiconductor layer 40 in the aforementioned step S7, the present invention can perform a second metallization process on the exposed side surface of the second anti-reflection layer 50 to form a second electrode 70 on the second anti-reflection layer 50. In the actual fabrication of the structure, a through hole is first generated at an appropriate position above the second semiconductor layer 40 for the formed first anti-reflection layer 30 and the second anti-reflection layer 50, and then the second electrode 70 is formed by performing a second metallization process, so that the second electrode 70 is electrically connected to the second semiconductor layer 40. In the present invention, the first electrode 60 is a positive electrode, but the present invention is not limited thereto.

The present invention also includes a photodiode structure 1 using the manufacturing method and process described above. The structural features of the photodiode structure 1 of the present invention are shown in FIG. 2 or FIG. 4, and the formation method of each detailed structure has been disclosed in the above description, and will not be elaborated here.

The above embodiments are essentially only for auxiliary explanation and are not intended to limit the embodiments of the application subject or the application or use of such embodiments. In addition, although at least one exemplary embodiment has been proposed in the aforementioned embodiments, it should be understood that the present invention can still exist in a large number of variations. It should also be understood that the embodiments described herein are not intended to limit the scope, use or configuration of the claimed application subject in any way. On the contrary, the aforementioned embodiments will provide a simple guide for those with ordinary knowledge in the field to implement one or more of the embodiments described. Furthermore, various changes can be made to the function and arrangement of the components without departing from the scope defined by the scope of the patent application, and the scope of the patent application includes known equivalents and all foreseeable equivalents at the time of filing the present patent application.

1: Photodiode structure 10: Substrate 20: First semiconductor layer 21: Recess 30: First anti-reflection layer 40: Second semiconductor layer 50: Second anti-reflection layer 60: First electrode 70: Second electrode S1~S8: Steps

FIG. 1 is a flow chart of the manufacturing method of the photodiode structure of the present invention. FIG. 2A is a schematic diagram of the structure of the photodiode structure of the present invention before the second semiconductor layer is formed. FIG. 2B is a schematic diagram of the structure of the photodiode structure of the present invention after the second semiconductor layer is formed. FIG. 3 is another flow chart of the manufacturing method of the photodiode structure of the present invention. FIG. 4 is an overall schematic diagram of the photodiode structure of the present invention.

S1~S5: Steps

Claims (12)

A method for manufacturing a photodiode structure, the method comprising the following steps: Providing a substrate; Performing an epitaxial process to form a first semiconductor layer on the substrate; Performing an active region patterning etching process to form a recess on the first semiconductor layer; Performing a first coating process to form a first anti-reflection layer on the first semiconductor layer; and Performing an ion distribution process to pass through the first anti-reflection layer and form a second semiconductor layer in the recess. A manufacturing method as described in claim 1, wherein the first coating process is a high temperature LPCVD process. A manufacturing method as described in claim 2, wherein the process temperature of the first coating process is not lower than 800°C. The manufacturing method as described in claim 1, wherein the thickness of the first anti-reflection layer is between 20 and 30 nm. A manufacturing method as described in claim 1, wherein the first anti-reflection layer is formed by a LPCVD process. The manufacturing method as described in claim 1 further includes the following steps: Performing a second coating process to form a second anti-reflection layer on the first anti-reflection layer; Performing a first metallization process to form a first electrode electrically connected to the substrate; and Performing a second metallization process to form a second electrode electrically connected to the second semiconductor layer. A manufacturing method as described in claim 6, wherein the second coating process is a PVD process, and the process temperature of the second coating process is lower than the process temperature of the first coating process. A manufacturing method as described in claim 7, wherein the process temperature of the second coating process is not higher than 200°C. A manufacturing method as described in claim 6, wherein the thickness of the second anti-reflection layer is between 100 and 150 nm. A manufacturing method as described in claim 6, wherein the second anti-reflection layer is formed by a PVD process. A manufacturing method as described in claim 6, wherein the first semiconductor layer is an N-type semiconductor layer, the second semiconductor layer is a P-type semiconductor layer, the first electrode is a negative electrode, and the second electrode is a positive electrode. A photodiode structure manufactured using the manufacturing method described in any one of claims 1 to 11.