TWI574392B - Front side illumination sensor and fabrification method of front side illumination sensor - Google Patents

Description

Front light sensor and front light sensor manufacturing method

The present invention relates to a front-illuminated sensor and a method of fabricating the same, and more particularly to a front-illuminated sensor and a method of fabricating the same, including a sidewall structure useful for reducing interference.

A front-side illumination sensor can apply a light pipe in each pixel unit to direct incident light passing through a color filter into a substrate ( A photodiode on the substrate).

Please refer to FIG. 1 , which is a partial structural diagram of a conventional front light sensor 100 . The front light sensor 100 includes two pixel units PU1 and PU2. The pixel unit PU1 includes a sensing element (such as a photodiode PD1) and a light guiding element (such as a light pipe LP1) located on a substrate SUB. a color filter CF1 and a microlens ML1; likewise, the pixel unit PU2 includes a sensing element (such as the photodiode PD2) and a light guiding element (such as the light pipe LP2) located on the substrate SUB. a color filter CF2 and a microlens ML2, wherein the light pipes LP1 and LP2 are surrounded by a dielectric D (dielectric), which may be an inter-layer dielectric or an inter-metal dielectric. (inter metal dielectric)) surrounded by. Taking the pixel unit PU1 as an example, when the incident light is irradiated to the front illumination sensor 100, the incident light passes through the microlens ML1 and the color filter CF1 to generate a filter output and enter the light pipe LP1, and then to the photodiode. The body PD1, wherein the reflection coefficient of the constituent material of the light pipe LP1 is smaller than the reflection coefficient of the surrounding dielectric material D, so that the incident light passing through the light pipe LP1 is confined within the light pipe LP1 until entering the photosensitive diode Among the PD1. Since the light pipes LP1 and LP2 are used to guide incident light, the metal layers M1 and M2 can be used only for wiring other than the light pipes LP1 and LP2.

Please refer to FIG. 2, which is a partial flow diagram of the front surface illumination sensor 100 shown in FIG. First, a substrate SUB is provided, followed by photodiodes PD1 and PD2, and then a dielectric D is formed on the substrate SUB. The light pipes LP1 and LP2 are then formed in the dielectric D, for example, by etching. Then, the color filters CF1 and CF2 corresponding to each of the pixel units PU1 and PU2 are formed, that is, among the front illumination sensors 100, the color filters CF1 and CF2 of two adjacent pixel units PU1 and PU2 are formed. There will be direct contact. However, since there is no isolation mechanism between the color filters CF1 and CF2, the incident light may pass through the color filter CF2 and enter the light pipe LP2 and the photodiode after passing through the microlens ML1 of the pixel unit PU1. The body PD2, in turn, causes interference to the pixel unit PU2. Similarly, when the incident light passes through the microlens ML2 of the pixel unit PU2, it may pass through the color filter CF1 and enter the light pipe LP1 and the photodiode PD1, thereby causing Interference to pixel unit PU1.

In addition, conventional front illumination sensors reduce the length of the light guide as much as possible in order to reduce the travel path of incident light in the light pipe. However, the length of the light pipe is limited by the depth of the color filter, that is, the depth of etching of the dielectric D above the light pipes LP1 and LP2 and part of the light pipes LP1 and LP2, in the conventional semiconductor process. The depth of the etching can only be determined by the etching time, so the etching depth and the flatness of the etching surface cannot be accurately controlled, thereby affecting the quality of the light sensing.

In view of this, the present invention provides a front illumination sensor and related manufacturing method to solve the above problems.

According to an embodiment of the present invention, a method for fabricating a front light sensor includes: forming at least one sensing element in a substrate; forming a dielectric layer over the substrate; a metal layer in the electrical layer; the metal layer is used as a barrier layer, the dielectric layer is etched to form a first recess corresponding to the sensing component; and a second recess is formed on the sensing component The first component and the second recess are filled with a first material and a second material to form a color filter and a light guiding component, respectively.

In accordance with another embodiment of the present invention, a front illumination sensor is provided that includes a plurality of pixel units. Each pixel unit includes a color filter, a sensing element, a sidewall structure, and a light guiding element. The color filter is configured to receive an incident light and generate a filtered output. The light guiding element is used to guide the filter output to the sensing element. The sidewall structure surrounds the color filter to reduce interference of the filter output to adjacent pixel units.

In accordance with another embodiment of the present invention, a front illumination sensor is provided that includes a plurality of pixel units. Each pixel unit includes a color filter, a sensing element, and a light guiding element. The color filter is configured to receive an incident light and generate a filtered output. The light guiding element is used to guide the filter output to the sensing element. The color filter of each pixel unit has no direct contact with the color filter of any adjacent pixel unit.

Please refer to FIG. 3, which is a partial flow chart of a front illumination sensor according to an embodiment of the invention. Compared with the structure of the conventional front light sensor, the front light sensor of the present invention applies a dual damascene fabrication technique to sequentially form light guiding elements (such as light pipes) and color filters. In one example, the front illumination sensor applies a metal layer M2 as a barrier layer of the dual damascene structure to define a boundary between the light pipe and the color filter. In the first step of the fabrication process, a photodiode is formed on the substrate SUB (the photodiodes PD1 and PD2 in FIG. 3 correspond to the pixel units PU1 and PU2, respectively), and a dielectric and a metal layer are formed. (In this example, only the metal layers M1 and M2 are used. However, other embodiments may use only one type or two or more metal layers at the same time). Then, etching is performed in each pixel unit, and the first recess U1 is formed with the metal layer M2 as a barrier layer, and then etching is continued to form the second recess U2, wherein the first recess U1 and the second recess U2 A dual damascene structure (i.e., the extent of etching is controlled by the metal layer M2 to form a first recess U1 having a larger aperture and a second recess U2 having a smaller aperture). Then, the constituent material of the light guide (for example, a filter material or a light guide material) is filled in; finally, the constituent materials of the color filters corresponding to the respective pixel units are respectively filled in (for example, a filter) material). Since the present invention applies the metal layer M2 to realize the dual damascene structure, the present embodiment can accurately control the lengths of the light pipes LP1 and LP2 to meet different design requirements as compared with the light pipes in the prior art. However, the application of the metal layer M2 as a barrier layer is only one embodiment of the present invention, and other metal layers or other materials (for example, titanium nitride TiN or tantalum nitride TaN) may also be used to realize the barrier layer.

Please refer to FIG. 4 in conjunction with FIG. 3 to further understand the manufacturing process of the front side illumination sensor of the present invention. FIG. 4 is a partial structural diagram of a front illumination sensor 400 implemented in accordance with an embodiment of the present invention. First, the metal layer M2 is disposed around the predetermined shape of the light pipes LP1 and LP2. Next, the dielectric over each of the pixel units PU1, PU2 is etched to form a recess having two different apertures (one of the first recess having a larger aperture and one having a smaller aperture) Double groove structure of two grooves). Next, a material of the light guide (for example, a filter material or a light guiding material) is filled in each pixel unit to form the light pipes LP1 and LP2. Then, the color filter material corresponding to each pixel unit (for example, the filter material) is filled in separately to form color filters CF1 and CF2. Finally, corresponding microlenses ML1 and ML2 are formed on each pixel unit to complete pixel units PU1 and PU2.

As shown in FIG. 4, in this embodiment, there is no direct contact between the color filters (color filters CF1 and CF2) between each pixel unit (for example, PU1) and its adjacent pixel unit (for example, PU2). Instead, it is surrounded by the dielectric D. In other words, the color filters CF1 and CF2 in each pixel unit PU1 and PU2 are surrounded by the sidewall structure SW composed of the dielectric D to reduce the color filter. The filtered output of the slices CF1, CF2 interferes with adjacent pixel units. In addition, the reflection coefficients of the color filters CF1 and CF2 are different from the reflection coefficients of the dielectric D, so that when the incident light passes through the color filter CF1 of the pixel unit PU1 and a corresponding filter output is generated, the filter The light output does not pass through the dielectric D and interferes with the operation of the pixel unit PU2. Similarly, when the incident light passes through the color filter CF2 of the pixel unit PU2 and generates a corresponding filter output, the filter output Does not pass through the dielectric D and interferes with the operation of the pixel unit PU1.

It should be noted that although the present invention applies a dual damascene structure to the front illumination sensor, in practice, it is not necessary to make too much change in the process, and an effect of effectively reducing interference can be achieved. In addition, the main structural difference between the front illumination sensor 400 of the present invention and the conventional front illumination sensor 100 is that the sidewall structure surrounding the color filter is formed by the use of the dual damascene structure, and therefore, reference is made to the first paragraph in the above paragraph. The description of the front surface light sensor 100 shown in the figure should be able to easily understand the function and operation of the components in the front surface light sensor 400 shown in Fig. 4, and therefore will not be further described herein.

In summary, the present invention provides a front-illumination sensor that is simple and can effectively reduce interference, and can provide a sidewall structure around each pixel unit by micro-modifying the manufacturing process, thereby reducing the general front-illumination sensor. Interference between adjacent pixel units.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100, 400. . . Front illumination sensor

PU1, PU2. . . Pixel unit

ML1, ML2. . . Microlens

CF1, CF2. . . Color filter

LP1, LP2. . . Light pipe

PD1, PD2. . . Photosensitive diode

M1, M2. . . Metal layer

D. . . Dielectric

SUB. . . Substrate

SW. . . Side wall structure

Figure 1 is a partial schematic view of a conventional front light sensor.

Fig. 2 is a partial flow chart showing the production of the front face light sensor shown in Fig. 1.

FIG. 3 is a partial flow diagram of a front illumination sensor according to an embodiment of the invention.

4 is a partial structural diagram of a front illumination sensor implemented in accordance with an embodiment of the present invention.

400. . . Front illumination sensor

PU1, PU2. . . Pixel unit

ML1, ML2. . . Microlens

CF1, CF2. . . Color filter

LP1, LP2. . . Light pipe

PD1, PD2. . . Photosensitive diode

M1, M2. . . Metal layer

D. . . Dielectric

SUB. . . Substrate

Claims (11)

A method for manufacturing an image sensor includes: forming at least one sensing element in a substrate; forming a dielectric layer and a metal layer in the dielectric layer on the substrate; The metal layer is a barrier layer, and the dielectric layer is etched to form a first recess corresponding to the sensing component; a second recess is formed on the sensing component, which corresponds to the sensing component; The first recess and the second recess are filled with a first material and a second material to form a color filter and a light guiding component, respectively. The manufacturing method according to claim 1, wherein the first material is a filter material and the second material is a light guide material. The manufacturing method of claim 1, wherein the first material and the second material are the same as the filter material. The manufacturing method of claim 1, wherein the second groove is formed after the first groove. The manufacturing method of claim 1, wherein the first groove is formed after the second groove. A front side illumination sensor includes: a plurality of pixel units, each pixel unit includes: a sensing element; a color filter disposed in a first groove, Receiving an incident light and generating a filtered output; a light guiding component is disposed in a second recess for guiding the filter output to the sensing component, wherein the first recess and the second The groove is connected; and a sidewall structure forms the first groove and surrounds the color filter to reduce interference of the filter output on adjacent pixel units. The front illumination sensor of claim 6, wherein a reflection coefficient of one of the color filters is different from a reflection coefficient of the sidewall structure. The front illumination sensor of claim 7, wherein the color filter has a reflection coefficient greater than the reflection coefficient of the sidewall structure. The front illumination sensor of claim 6, wherein the light guiding element and the color filter system form a dual damascene structure. The front illumination sensor of claim 9, wherein the contact surface between the light guiding element and the color filter is surrounded by a barrier layer, and the barrier layer is It is a metal layer. The front illumination sensor of claim 6, wherein the color filter of each pixel unit has no direct contact with the color filter of any adjacent pixel unit.