TWI425630B - Image sensor - Google Patents

Description

Image sensor

The invention relates to sensors, in particular image sensors.

Digital cameras are widely used in today's electronic products, and digital cameras include image sensors that convert light into electric charges. Image sensors can be classified as charge-coupled devices according to their principles. Charge-Coupled Device) image sensor (also known as CCD image sensor) and CMOS (complementary metal oxide semiconductor) image sensor, in which CMOS image sensor is manufactured based on complementary metal oxide semiconductor (CMOS) technology. . Since the CMOS image sensor is fabricated using a conventional CMOS circuit process, the image sensor and its peripheral circuits can be integrated.

In addition, CMOS image sensors are more inclined to further reduce the pixel size they use. However, small-sized pixels and pixel arrays will have an impact on the performance of CMOS Image Sensor (CIS) systems.

Conventional CMOS image sensors use Front Side Illumination (FSI) technology to fabricate pixels on a pixel array whose incident light passes through the front side of the pixel to reach the photo-sensing area. ). That is to say, the structure of the conventional front illumination CMOS image sensor is such that the incident light needs to pass through the dielectric layer and the metal layer before reaching the light sensing region, which leads to the conventional CMOS. Image sensors face problems such as low quantum efficiency, severe cross talk between pixels, and dark current.

Another CMOS image sensor is a Back Side Illumination (BSI) CMOS image sensor. Backlighting technology was originally used on the pixels of the CCD image sensor. Unlike the front illumination technology, which constructs an image sensor from the front end of the silicon die; the back illumination CMOS image sensor places a color filter and microlens on the back of the pixel ( Back side) causes incident light to enter the image sensor from the back of the image sensor. Compared to front-illuminated CMOS image sensors, this back-illuminated CMOS image sensor has several advantages: less light loss, lesser interlacing interference, and better quantum efficiency.

However, whether it is a front-illuminated CMOS image sensor or a new back-illuminated CMOS image sensor, there is a need to further improve its performance and reduce cross-interference or light loss. Therefore, there is an urgent need to propose new CMOS image sensors to provide superior performance.

In view of this, one of the objects of the present invention is to provide a new image sensor structure to improve the performance and quantum efficiency of a CMOS image sensor. The present invention applies a light shielding wall structure to a CMOS image sensor, and the light shielding wall is located at a periphery of at least one side of the pixel to effectively reflect incident light that touches the light shielding wall back into the corresponding pixel. In turn, the quantum efficiency of the CMOS image sensor is effectively improved while suppressing cross talk between pixels to reduce light loss.

According to an embodiment of the invention, an image sensor is provided. The image sensor includes: a substrate, at least one pixel, and at least one light shield, the light shielding wall is located around at least one side of the pixel, wherein the light shielding wall is formed on the When the contact is made.

Certain terms are used throughout the description and following claims to refer to particular elements. Those of ordinary skill in the art should understand that a hardware manufacturer may refer to the same component by a different noun. The scope of this specification and the subsequent patent application do not use the difference of the names as the means for distinguishing the elements, but the difference in function of the elements as the criterion for distinguishing. The term "including" as used throughout the specification and subsequent claims is an open term and should be interpreted as "including but not limited to". In addition, the term "coupled" is used herein to include any direct and indirect electrical connection. Therefore, if a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device or indirectly electrically connected to the second device through other devices or connection means.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of a back illumination (BSI) CMOS image sensor according to a first embodiment of the present invention. The backlight CMOS image sensor 100 includes a lens 110, a color filter 120, a substrate 130, a first dielectric layer 150, and a first metal wire layer. The backlight CMOS image sensor 100 may have other architectures, such as a second metal winding layer, a third metal winding layer, and a sandwich therebetween. Dielectric layer. In addition, as is well known to those skilled in the art, a CMOS image sensor can include a plurality of lenses, color filters, and pixels, wherein each pixel includes at least one photodiode and at least one Transistor. Please note that the structure of the backlight illumination CMOS image sensor 100 illustrated in FIG. 1 is for illustrative purposes only and is not one of the limitations of the present invention.

As shown, incident light 105 reaches pixel 135 after passing through lens 110 and color filter 120. The lens 110 is attached to the substrate 130, and in a preferred embodiment of the invention, it can be implemented as a micro lens. The pixel 135 includes a light emitting diode 180 for converting incident photons into electrons, wherein there is typically a shallow trench isolation (STI) region 132-1 and 132 on each side of the pixel 135. -2. The backlight CMOS image sensor 100 further has a contact 155 that is tied in the first dielectric layer 150, where the contact 155 is used to connect a gate 140 to a metal line 165, wherein Gate 140 is part of a transistor and the electro-crystalline system corresponds to pixel 135. Since not all of the incident light 105 is conventionally able to reach the pixel 135 smoothly, some of the photons may be reflected/refracted to adjacent pixels, and thus cause cross-interference between the pixels. In order to improve the performance of the image sensor, the backlight illumination CMOS image sensor 100 uses a light shielding wall 170 to smoothly direct the incident light 105 into the pixel 135. In this way, by using the light shielding wall 170 disposed on at least one side of the pixel 135 to effectively guide the incident light to the pixel 135 (or the light emitting diode 180), the light loss of the CMOS image sensor will be Effectively reduce and reduce the occurrence of cross interference.

In order to increase the quantum efficiency of the backlight illumination CMOS image sensor 100, the material of the light shielding wall 170 may be selected to ensure that the light shielding wall 170 can effectively guide the incident light that touches the light shielding wall 170 back to the pixel 135, and is not absorbed. Incident light 105. It is noted that the material of the light shielding wall 170 is not limited as long as the incident light 105 can be guided back to the pixel 135 and the incident light 105 is not absorbed. For example, through appropriate design considerations, the light shielding wall 170 can be solid or can be a liquid material. In a preferred embodiment of the invention, the light shielding wall 170 can be made of a metallic material. In addition, in order to effectively reduce the complexity of the manufacturing process, the light shielding wall 170 can be manufactured while forming the contact 155, and the material of the light shielding wall 170 can be selected to be the same as the material of the contact 155 to further reduce the production cost. In other words, in some preferred embodiments, the material of the light shielding wall 170 can be the same as the material of the manufacturing contact 155. It should be noted that the position of the aforementioned light shielding wall 170 and its material are for illustrative purposes only and are not one of the limitations of the present invention. For example, through appropriate design changes, the light shielding wall 135 can be placed on other structures of the backlight illumination CMOS image sensor 100 located around 135 pixels to achieve the purpose of reducing light loss and reducing cross interference of adjacent pixels. The aforementioned related design changes are all within the scope of protection of the present invention.

Please refer to FIG. 2, which shows the implementation details of the backlight illumination CMOS image sensor of the first embodiment of the present invention shown in FIG. 1. For the backlight CMOS image sensor 200, the incident light 105 passes through the light shielding wall 170 and passes through the lens 110 and the color filter 120 to reach the pixel 135. The light shielding wall 170 is located at the periphery of the pixel 135 to enclose most of the incident light, and reflects the incident light that touches the light shielding wall 170 back to the pixel 135, thereby improving the quantum efficiency of the back illumination CMOS image sensor and reducing the crossover thereof. interference. In addition, the pixel 135 has a light emitting diode 180 and a transistor 190, and the gate 140 is a part of the structure of the transistor 190. In the present embodiment, the light shielding wall 170 is fabricated while forming the contact 155, and the material of the light shielding wall 170 can be selected to be the same as the material of the contact 155.

In addition, in the embodiment illustrated in FIG. 2, the gate 140 is connected to a metal line (not shown) via contact 155. In addition, in some preferred embodiments, in order to further improve the performance of the backlight illumination CMOS image sensor 200, the material of the light shielding wall 170 may be selected such that it does not absorb incident light to further reduce the light loss of the incident light. In other words, the material of the light shielding wall 170 may vary with the design requirements. For example, the light shielding wall 170 is designed as a liquid structure or a solid structure depending on design requirements. However, please note that in addition to being applicable to backlit CMOS image sensors, the techniques of the present invention can also be applied to front illumination CMOS image sensors fabricated using front illumination techniques.

Please refer to FIG. 3. FIG. 3 is a schematic diagram of a front illumination (FSI) CMOS image sensor according to a second embodiment of the present invention. The front illumination CMOS image sensor 300 has a lens 110, a color filter 120, a substrate 130, a first dielectric layer 150, and a first metal winding layer 160. The pixel 135 is used to convert photons into electrons, and the Shallow Trench Isolation (STI) regions 132-1 and 132-2 are respectively located on both sides of the pixel 135. The front illumination CMOS image sensor 300 further includes a contact 155, a gate 140 and a metal line 165, and the gate 140 is part of a transistor (not shown); wherein the pixel 135 is included There is a light emitting diode 180 and a transistor. Since the structure of the front illumination CMOS image sensor 300 and its related internal operations are well known to those skilled in the art, the difference between the back illumination CMOS image sensor and the front illumination CMOS image sensor is in the previous paragraph. I have explained this, and I will not repeat them here for the sake of brevity.

Similar to the backlight illumination CMOS image sensor 100 of the foregoing first embodiment, in FIG. 3, the light shielding wall 170 is placed around the periphery of the pixel 135. And the light shielding wall 170 is manufactured while forming the contact 155; and the material of the light shielding wall 170 can be selected to be the same as the material of the contact 155. In some preferred embodiments, the material of the light shielding wall 170 may be a metal material (material) for forming the contact 155. However, please note that the material of the light shielding wall 170 may vary depending on the design requirements. For example, the material of the light shielding wall 170 may be a solid material benefit body material; in fact, any incident light 105 may be blocked by the light shielding wall 170. Materials that are reflected back to the pixels 135 can all be selected to make the light shielding walls 170. In addition to this, the material that does not absorb the incident light 105 can be further selected to fabricate the light shielding wall 170 to further enhance quantum efficiency and reduce cross interference.

In addition, in order to reduce the manufacturing cost, the material of the light shielding wall 170 may be selected to be the same as the material for manufacturing the contact 155. In addition, the shape of the light shielding wall 170 may also be changed according to the design requirements, and the related design changes mentioned above are also included in the protection scope of the present invention.

Please refer to FIG. 4 to FIG. 5 to see FIG. 1 to FIG. 3 . FIG. 4 is a top view of an embodiment of the CMOS image sensor of the present invention; FIG. 5 is a view of the present invention. A top view of another embodiment of a CMOS image sensor. As shown in FIG. 4, the light shielding wall 470 of the CMOS image sensor 400 is a light shielding wall of a slot-shaped sidewall structure, and in FIG. 5, the light shielding wall of the CMOS image sensor 500. The 570 is a shading wall of an island-shaped sidewall structure. In addition, as previously mentioned, the shape of the light-shielding wall of the present invention may vary with design requirements; for example, in other embodiments of the invention, the light-shielding wall may have a finger-shaped structure. . Please note that the foregoing description of the shape of the light-shielding wall is for illustrative purposes only, and all design variations of the shape of the light-shielding wall that can improve the performance of the CMOS image sensor are also within the scope of protection of the present invention.

In addition, the position of the light shielding wall is not limited by the foregoing description. For example, the light shielding wall may be located at any position of the pixel of the CMOD image sensor as long as it falls on the periphery of either side of the pixel. These related design changes are also within the scope of protection of the present invention.

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, 200. . . Back illumination CMOS image sensor

110. . . lens

120. . . Color filter

130. . . Substrate

132-1, 132-2. . . Shallow trench isolation zone

135. . . Pixel

140. . . Gate

150. . . First dielectric layer

155. . . contact

160. . . First metal winding layer

165. . . metal wires

170, 470, 570. . . Shading wall

180. . . Light-emitting diode

190. . . Transistor

300. . . Front illumination CMOS image sensor

400, 500. . . CMOS image sensor

1 is a schematic diagram of a back illumination (BSI) CMOS image sensor according to a first embodiment of the present invention.

Fig. 2 is a view showing the implementation details of the backlight illumination CMOS image sensor of the first embodiment of the present invention shown in Fig. 1.

3 is a schematic diagram of a front illumination (FSI) CMOS image sensor according to a second embodiment of the present invention.

Figure 4 is a top plan view of one embodiment of a CMOS image sensor of the present invention.

Fig. 5 is a top view showing another embodiment of the CMOS image sensor of the present invention.

100. . . Back illumination CMOS image sensor

110. . . lens

120. . . Color filter

130. . . Substrate

132-1, 132-2. . . Shallow trench isolation zone

135. . . Pixel

140. . . Gate

150. . . First dielectric layer

155. . . contact

160. . . First metal winding layer

165. . . metal wires

170. . . Shading wall

180. . . Light-emitting diode

Claims (14)

An image sensor comprising: a substrate; at least one pixel, wherein the pixel has a photodiode and at least one transistor, and the transistor is connected to a metal via a contact And a light shield disposed around at least one side of the pixel, wherein the light shielding wall is fabricated while forming the contact. The image sensor of claim 1, wherein the incident light that touches the light shielding wall is reflected by the light shielding wall to the pixel. The image sensor of claim 1, wherein the light shielding wall does not absorb incident light that touches the light shielding wall. The image sensor of claim 1, wherein the light shielding wall is solid. The image sensor of claim 4, wherein one of the materials of the light shielding wall is the same material as the one of the contacts of the image sensor. The image sensor of claim 5, wherein the material of the light shielding wall is a metal material. The image sensor of claim 1, wherein the light shielding wall is a liquid. The image sensor of claim 1, wherein the light shielding wall has an island-shaped sidewall structure. The image sensor of claim 1, wherein the light shielding wall has a slot-shaped sidewall structure. The image sensor of claim 1, wherein the light shielding wall has a finger-shaped sidewall structure. The image sensor of claim 1, wherein the image sensor further has a Shallow Trench Isolation (STI) region, the shallow trench isolation region is located outside the LED. And the light shielding wall is located above the shallow trench isolation zone. The image sensor of claim 1, wherein the image sensor adopts a Back Side Illumination (BSI) technology. The image sensor of claim 1, wherein the image sensor adopts a Front Side Illumination (FSI) technology. The image sensor according to claim 1, which is a Complementary Metal Oxide Semiconductor (CMOS) sensor.