TWI243477B - Image sensor with guard rings and method for forming the same - Google Patents

Abstract

An image sensor with air gaps as optical guard rings is provided. The air gaps are formed in a stacked insulating layer between the sensor areas, that is, around each pixel. A light transmitting insulating layer is formed on the stacked insulating layer without filling the air gaps.

Description

1243477

The technical field to which the invention belongs is particularly related to a method for avoiding strings between adjacent pixels. The present invention relates to an image sensor with an optical protection ring to avoid cross-talk. In the prior art, one or more of the charge couple diode array structure of a solid-state image-sensing digital video camera has one or more patterned sensitive layers. Among them, the CMOS image detector CMOS image detector and a detection logic circuit .Fill rate (aperture ef (light-sens iti example), although there is currently a degree of technology, but by further increasing the degree of fill, there are path products to develop a measuring lens, such as digital cameras, mobile phones and toys The detector is a necessary component. The traditional color analog or solid-state image sensor includes a charge-coupled device (CCD) or complementary metal-oxide-semiconductor ((^ 〇3)) light. The above device includes a color filter. The basic unit of a light image sensor below the middle layer of the array and above the surface layer of the microlens array element is defined as a daylight element. The basic manufacturing technology is the same as that of a CCD image detector. The detector includes a light sensor The factor that the light detector converts light into an electronic signal that detects light data (fi 11 factor) can sometimes be expressed as the aperture effect flClenCy, which is the size of the light-sensitive area J The size of the pixel (pixel) is larger than 4 plus shirts. 丨 丨 ～ ～ are filled factors to increase the sensitivity of the connection. The lines cannot be completely moved, so it is time to change the factor. It is limited by Φ ^ ^. Therefore, in order to increase the lens shape of the light-sensitive species, a 4 to 4 technology is used to converge, focus, and incident light onto the light detector by changing the light reaching the light detector.

1243477

2 = Image sensor for color images' Basically necessary and a color, a color on the media device that first detects the gain, and a medium device that generates and accumulates charge. For example, a plurality of light sensors set in the light detection group (three -co ^ r D .. The shirt color filter array basically selects a group of two or three primary colors ^. ί configurationλ primary configuration), which is RG Β, yellow (Υ), or RG (Υ) ), Red: = :?), green (cyan, c). Multiple are set at /. The microlenses on the pericardial column are used to increase the photosensitivity of the image sensor. The microlens is a conventional image sensor disposed on the substrate 10. Incident: The two light sources are effectively focused on the specified light diode 12 and will be transmitted to the adjacent light diode 12. In addition, when reducing the size of daylight and using a multi-layer metal layer to reduce the cost of the sensor, the crosstalk phenomenon becomes more serious due to the scattered light from the metal layers 6 and 20, resulting in a decrease in image resolution, especially black. And a white sensor, and it is more difficult to perform color correction on a color sensor. SUMMARY OF THE INVENTION In view of this, the object of the present invention is to provide an image sensor that avoids the phenomenon of crosstalk between adjacent daylight. To achieve the above object, the present invention provides an image sensor using an air gap as an optical protection ring. Including, the air gap is formed in a stacked metal interlayer dielectric layer and is located between the sensing regions, and a light penetrating dielectric layer is disposed on the stacked metal interlayer dielectric layer, but is not filled. Breathe

0503 -9717TWf (N1); TSMC2003-0735; Dav i d.p t d page 5 1243477 V. Description of the invention (3) Gap. Due to the above structure, the incident light is not transmitted to the neighboring daylight. In order to make the above-mentioned objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings to describe in detail as follows: Implementation Examples Please refer to FIGS. 2A to 2C. Describes a method for manufacturing an image sensor according to an embodiment of the present invention. An air gap is used as an optical guard ring to modify a conventional image sensor. As shown in FIG. 2A, a sensing region is formed, for example, a photodiode 102 is formed on a semiconductor substrate 100, and other components such as transistors (not shown) are also formed on the semiconductor substrate 100. Next, an interlayer dielectric layer (ILD) 104 is formed on the semiconductor substrate 100 and covers the components. The interlayer dielectric layer 104 is a light-transmitting metal front dielectric layer. The first metal layer is successively deposited on the interlayer dielectric layer 104, and is selectively patterned to form a first metal wire 106, wherein the metal wire is not located above the photodiode 102. After that, a first metal interlayer dielectric layer 108 is deposited on the first metal wire 106 to insulate the metal wires 106 adjacent to each other and planarize the dielectric layer. Next, a second metal layer is deposited on the first metal interlayer dielectric layer 108, and is selectively patterned to form a second metal wire 1 1 0. The second metal wire 1 1 0 is located on the first metal wire 106. Above and after, a second metal interlayer dielectric layer 112 is deposited on the second metal wire 110 to insulate the metal wires 110 adjacent to each other and planarize the dielectric layer. Gold formation

0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 6 1243477 V. Description of the invention (4) The step of interconnecting the interlayer dielectric layers 1 16 and 1 2 0. The metal interlayer dielectric layers 1 0 8, 1 1 2, 1 16 and 1 2 0 are only used to illustrate this embodiment. Therefore, the number of dielectric layers may be increased or decreased according to different requirements. In the 2β ^ to 2C diagrams, the metal interlayer dielectric layers 108, 112, 116, and 120 are regarded as a stack of metal interlayer dielectric layers 122. ^ ^ As shown in FIG. 2B, an energy sensitive layer such as a photoresist layer is deposited on the stacked metal interlayer dielectric layer 1 2 2 and a patterning step is performed using a conventional lithography process to form a Optical protection ring pattern, and then ^ using the patterned photoresist layer 1 24 with an optical protection ring pattern as an etch mask / metal interlayer dielectric layer 1 2 2 stacked on top of each other to form around each day element Air gap 1 2 6. As shown in FIG. 2C, a light penetrating dielectric layer 128 is formed on the stacked metal interlayer dielectric layers 1 2 2 but does not fill the air gap. 26. The light penetrating dielectric layer 128 is, for example, a The oxide layer deposited by PECVD has a thickness of approximately 3,500 to 10,500 microns, and is then planarized by CMP. The air gap 1 2 6 can be formed on all or part of the metal In the interlayer dielectric layer, as shown in FIG. 2C, the air gap 1 26 is produced by one etching process, or as shown in FIG. 3, 'air gap 1 2 6 is produced twice or more | Fabricated and isolated with light penetrating dielectric layers 128a, 128b and 128c that do not fill the air gap 126 between each other, the above method can produce the air gap 126 formed in the dielectric layer between all the metal layers. In addition, as shown in FIG. 4, after the light penetrating dielectric layer 128 covers the stacked metal interlayer dielectric layer 22, an interconnecting step of forming another metal interlayer dielectric layer 1 2 2 is performed, then The gaps 1 2 6 are only formed in a part of the metal interlayer dielectric layer.

1243477 V. Description of the invention (5) '"' ^ The optical protection ring of the present invention to avoid the phenomenon of crosstalk between adjacent celestial elements' has a refractive index of n = 1, and can be composed of air or a material having a refractive index of 1. When incident light enters a solid-state image sensor with an air gap as an optical protection ring, the incident light will cause total reflection between the air gaps and a total reflection angle of 42 degrees in the stacked metal interlayer dielectric layer. Figure 5 shows the relationship between crosstalk and the incident angle of incident light. The figure includes a conventional image sensor with no optical protection ring in the stacked interlayer dielectric layer and the present invention in the interlayer dielectric layer. An air-gap image sensor such as an optical guard ring. The crosstalk phenomenon is defined as the signal of the metal-light-shielded daylight (corresponding to the sensing area 102b, which is shielded by metal M4) separated by an unshielded daylight (corresponding to the sensing area 1 2a). As shown in Fig. 6, if the optical interlayer dielectric layers IMD1, iMD2, and IMD3 are not provided with an optical guard ring, the relationship between the crosstalk phenomenon and the incident light incident angle can be represented by curve A in Fig. 5, if the air gap 2 2 6β If it is placed in the metal interlayer dielectric layers IMD2 and IMD3, the relationship between the crosstalk phenomenon and the incident light incident angle can be represented by the curve B in Fig. 5, and if the air gap 2 2 6C is placed in the metal interlayer dielectric layers IMD1 and IMD2 The relationship between the crosstalk phenomenon and the incident angle of the incident light can be represented by the curve C in FIG. 5. As shown in Figure 5, in the traditional image sensor, the crosstalk phenomenon will become more serious as the incident angle increases, especially in the range of _30 ° to -40 ° and ^ 30 ° to 40 °. However, according to the present invention, the air gap is used as the optical guard ring of the image sensor, and the phenomenon of crosstalk will almost disappear. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art will not depart from the essence of the present invention.

0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 8

1243477

0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 9 1243477 Brief Description of Drawings Figure 1 shows a conventional image sensor installed on the substrate. Figures 2A to 2C show the method for manufacturing an image sensor according to the present invention. Figure 3 shows an image sensor with an air gap, which is formed through multiple etching steps and is isolated by light penetrating the dielectric layer. Figure 4 shows an image sensor with an air gap, where the air gap only appears in part of the interlayer dielectric layer. Figure 5 shows the relationship between crosstalk and the incident angle of incident light. The figure includes a traditional image sensor without an optical protection ring in the stacked metal interlayer dielectric layer and the invention uses gas in the metal interlayer dielectric layer. The gap serves as an image sensor for the optical guard ring. Fig. 6 shows a crosstalk phenomenon for measuring an image sensor with or without an air gap as an optical guard ring. Explanation of symbols Known part (Fig. 1) 10 ~ substrate; 1 2, 1 2 '~ photodiode; 16, 20 ~ metal layer; 3 0 ~ incident light. Part of the embodiment of this case (Figures 2A to 6) 100 ~ substrate; 102, 102a, 102b ~ photodiode (sensing area); 104 ~~ interlayer dielectric layer (ILD); 106 ~ First metal wire

0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 10 1243477 The diagram briefly illustrates 108 to the first metal interlayer dielectric layer; 106 to the first metal wire; 1 10 to the second metal wire; 112 ~ second metal interlayer dielectric layer; 1 16、1 2 0 ~ metal interlayer dielectric layer; 122 ~ stacked metal interlayer dielectric layer; 1 2 4 ~ photoresist layer; 126, 226B, 226C ~ air gap 128 ~ light penetrates the dielectric layer; A ~ does not set the relationship curve of air gap; B ~ sets the air relationship between the dielectric layer IMD2 and IMD3; C ~ sets the air gap to the dielectric layer IM D1 and I MD Relationship curve of 2; ILD ~ interlayer dielectric layer; IMD1, IMD2, IMD3 ~ metal interlayer dielectric layer; M4 ~ metal layer.

0503-9717TWf (Nl); TSMC2003-0735; David.ptd p. 11

Claims (1)

1243477 VI. Application scope 1. An image sensor with an optical protection ring, comprising: a substrate having a plurality of sensing regions; a stacked interlayer dielectric layer disposed on the substrate; a plurality of air gaps (Airgaps), disposed in the stacked metal interlayer dielectric layers, and located between the sensing regions; and a light penetrating dielectric layer, disposed on the stacked metal interlayer dielectric layers, but not filled Into these air gaps. 2. The image sensor with an optical protection ring as described in item 1 of the scope of patent application, wherein the light penetrating dielectric layer is a PECVD oxide layer. 3. The image sensor with an optical protection ring as described in item 1 of the scope of the patent application, which further includes an interlayer dielectric layer (I LD) disposed between the stacked interlayer dielectric layer and the substrate. . 4. The image sensor with an optical protection ring as described in item 1 of the patent application scope, further comprising another metal interlayer dielectric layer disposed on the light penetrating dielectric layer. 5. —A device comprising an image sensor with an optical protection ring, wherein the image sensor includes: a substrate 'having a plurality of sensing regions; a stacked interlayer dielectric layer disposed on the substrate A plurality of air gaps disposed in the stacked metal interlayer dielectric layers and located between the sensing regions; and a light penetrating dielectric layer disposed on the stacked metal interlayer dielectric layers, but Do not fill in these air gaps. 6. Contains an optical protection as described in item 5 of the scope of patent application 0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 12 1243477 6. Scope of patent application Ring image sensor device, where the device is a mobile phone. 7. The device including an image sensor with an optical protection ring as described in item 5 of the scope of patent application, wherein the device is a digital camera. 8. A device including an image sensor with an optical protection ring as described in item 5 of the scope of patent application, wherein the device is a toy. 9. An image sensor with an optical protection ring, comprising: a substrate having a plurality of sensing regions; a stacked metal interlayer dielectric layer disposed on the substrate; a plurality of optical elements having a refractive index n = 1 A guard ring is disposed in the stacked metal interlayer dielectric layers and is located between the sensing regions; and a light penetrating dielectric layer is disposed in the stacked metal interlayer dielectric layers and the optical protection rings on. I 0. The image sensor with an optical protection ring as described in item 9 of the scope of the patent application, wherein the optical protection rings are air gaps. II. The image sensor with an optical protection ring according to item 9 of the scope of the patent application, wherein the light penetrating dielectric layer is a PECVD oxide layer. 1 2. The image sensor with an optical protection ring according to item 9 of the scope of the patent application, further comprising an interlayer dielectric layer disposed between the stacked metal interlayer dielectric layer and the substrate. 1 3. The image sensor with an optical protection ring according to item 9 of the scope of the patent application, further comprising another metal interlayer dielectric layer disposed on the light penetrating dielectric layer. 1 4. An apparatus including an image sensor with an optical protection ring, wherein the image sensor includes: 0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 13 1243477 6. Patent application scope-a substrate with a plurality of sensing areas; a stacked metal interlayer dielectric layer disposed on the substrate; a plurality of An optical protection ring having a refractive index of n = 1 is disposed in the stacked metal interlayer dielectric layers and located between the sensing regions; and a light penetrating dielectric layer is disposed in the stacked metal interlayer dielectrics. The electrical layer and the optical protection rings. 1 5. The device including an image sensor with an optical protection ring as described in item 14 of the scope of patent application, wherein the device is a mobile phone. 16. The device as described in item 14 of the scope of patent application, which includes an image sensor with an optical protection ring, wherein the device is a digital camera. 1 7. The device as described in item 14 of the scope of patent application, comprising an image sensor with an optical protection ring, wherein the device is a toy. 1 8. —A method for manufacturing an image sensor with an optical protection ring, including the following steps: providing a substrate including a plurality of sensing regions; forming an interlayer dielectric layer on the substrate and the sensing regions Forming a stacked metal interlayer dielectric layer on the interlayer dielectric layer; forming a plurality of gaps surrounding each celestial layer in the metal interlayer dielectric layer; and forming a light penetrating dielectric layer on the stack On the metal interlayer dielectric layer, but do not fill in the gaps. 19. The method for manufacturing an image sensor with an optical protection ring as described in item 18 of the scope of patent application, wherein the light-transmitting dielectric layer is formed by PECVD deposition and planarized by CMP. 0503-9717TWf (Nl); TSMC2003-0735; David.ptd Page 14 1243477 0503-9717TWf (Nl); TSMC2003-0735; David.ptd p. 15