Semiconductor device and image sensor

Abstract

The utility model provides a semiconductor device and an image sensor. The semiconductor device has a substrate, wherein the substrate has a plurality of protruding portions over the light detector. An isolation structure is disposed in the substrate and laterally surrounds the light detector. The isolation structure has a reflective element comprising a conductive material. The first dielectric layer is over the light detector, wherein the first dielectric layer extends into the substrate and is disposed between the reflective element and the substrate. The top surface of the first dielectric layer is irregular. The second dielectric layer is on the first dielectric layer and over the light detector. A top surface of the second dielectric layer over the plurality of protruding portions is irregular. The second dielectric layer extends vertically into the substrate along a surface of the first dielectric layer. A second dielectric layer is disposed along the sidewalls and the bottom surface of the reflective element.

Description

Technical Field

[0001] This utility model relates to a semiconductor device and an image sensor. Background Technology

[0002] Image sensors are solid-state devices configured to convert incoming light (e.g., photons) into electrical signals. These electrical signals are then provided to a processor, which converts them into data that can be stored and / or viewed by the user. Integrated circuit chips (ICs) with image sensors are widely used in modern electronic devices such as mobile phones, security cameras, and medical devices. Utility Model Content

[0003] This invention provides a semiconductor device comprising: a photodetector disposed in a substrate, wherein the substrate has a plurality of protrusions above the photodetector; an isolation structure disposed in the substrate and laterally surrounding the photodetector, wherein the isolation structure includes a reflective element comprising a conductive material; a first dielectric layer located above the photodetector, wherein the first dielectric layer extends substantially vertically into the substrate and is disposed between the reflective element and the substrate, and the top surface of the first dielectric layer above the plurality of protrusions is irregular; and a second dielectric layer located on the first dielectric layer and above the photodetector, wherein the top surface of the second dielectric layer above the plurality of protrusions is irregular, wherein the second dielectric layer extends substantially vertically into the substrate along the surface of the first dielectric layer, and wherein the second dielectric layer is disposed along the sidewalls and bottom surface of the reflective element.

[0004] This invention provides an image sensor, comprising: a substrate including a front surface relative to a back surface, wherein the substrate includes a first plurality of protrusions on the back surface; a first photodetector disposed within the substrate and located below the first plurality of protrusions; a reflective element disposed within the substrate and laterally offset from the first photodetector, wherein the reflective element extends from the back surface to the front surface; a high-absorption structure disposed above the back surface of the substrate and extending into the substrate, wherein the high-absorption structure separates the bottom surface and sidewalls of the reflective element from the substrate, wherein the high-absorption structure includes a first dielectric layer contacting the first plurality of protrusions, and a second dielectric layer on the first dielectric layer, wherein the first dielectric layer and the second dielectric layer extend to the back surface of the substrate; and a pad layer located between the second dielectric layer and the reflective element, wherein the pad layer is laterally offset from the back surface of the substrate. Attached Figure Description

[0005] The best understanding of the features of this disclosure will be achieved by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, according to industry standard practice, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of explanation.

[0006] Figures 1 to 2 The illustration shows a cross-sectional view of an image sensor in some embodiments, which includes a high absorption structure and a trench isolation structure with reflective elements to improve quantum efficiency (QE) and modulation transfer function (MTF).

[0007] Figure 3 The illustration shows a cross-sectional view of an image sensor in some embodiments, the image sensor including a high-absorption structure and a trench isolation structure with reflective elements having varying heights.

[0008] Figure 4 The illustration shows a cross-sectional view of an image sensor in some other embodiments, the image sensor including a high-absorption structure and a trench isolation structure.

[0009] Figure 5A and Figure 5B The illustration shows a cross-sectional view of an image sensor in some embodiments, the image sensor including various configurations of a recessed reflective element and a high-absorption structure absorption layer.

[0010] Figure 6A The illustration shows a cross-sectional view of an image sensor in some embodiments, the image sensor including a high-absorption structure and a trench isolation structure with reflective elements.

[0011] Figure 6B Explanation in Figure 6A Enlarged cross-sectional view of the trench isolation structure in some embodiments.

[0012] Figure 7 The illustration shows a cross-sectional view of an image sensor in some embodiments, the image sensor including a trench isolation structure and radiation absorption regions of different shapes.

[0013] Figures 8 to 21 The following are cross-sectional views illustrating a method for forming an image sensor including a high-absorption structure and a trench isolation structure with reflective elements.

[0014] Figures 22 to 25 The following are cross-sectional views illustrating a method for forming an image sensor including a high-absorption structure and a trench isolation structure with reflective elements.

[0015] Figures 26 to 31 The following are cross-sectional views illustrating a method for forming an image sensor including a high-absorption structure and a trench isolation structure with reflective elements.

[0016] Figure 32 A flowchart illustrating a method for forming an image sensor including a high-absorption structure and a trench isolation structure with reflective elements in some embodiments to improve QE and MTF performance. Detailed Implementation

[0017] This disclosure provides numerous different embodiments or instances for implementing various features of this disclosure. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and are not intended to be limiting. For example, the following description of a first feature formed on or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, thereby preventing direct contact between the first and second features. Furthermore, this disclosure may reuse reference numerals and / or letters in various instances. Such reuse is for the purpose of brevity and clarity and is not intended to indicate a relationship between the various embodiments and / or configurations discussed.

[0018] Furthermore, for ease of explanation, this document may use spatially relative terms such as “beneath,” “below,” “lower,” “above,” “upper,” and similar expressions to describe the relationship between one device or feature shown in the figures and another device or feature. These spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptions used herein can be interpreted accordingly.

[0019] Image sensors (e.g., semiconductor image sensors (CIS)) may include multiple pixel sensors disposed on a substrate. Each pixel sensor includes a photodetector configured to convert energy from a radiation source (e.g., light, infrared radiation, X-rays, etc.) into an electric current. Over time, the semiconductor industry has reduced the size of the pixel regions of pixel sensors on the substrate to increase the number of pixel regions in the image sensor integrated circuit (IC). Increasing the number of pixel regions in the CIS integrated circuit improves the resolution of the image captured by the CIS integrated circuit. However, as the pixel region size decreases, the pixel regions become closer together, increasing crosstalk between adjacent pixel regions.

[0020] Crosstalk occurs when incident light intended for one pixel region is undesirably sensed by another pixel region, thus degrading the image quality captured by a CIS integrated circuit chip. To mitigate crosstalk, photodetectors can be separated from each other by isolation structures configured to reduce electrical or photonic crosstalk between them. In some respects, the isolation structures are formed from one or more of the back or front sides of the substrate containing the photodetectors. However, the isolation structure can affect the quantum efficiency (QE) and modulation transfer function (MTF) of the image sensor. For example, isolation structures formed of oxides can have high QE and low MTF. However, by forming the isolation structure of a metal, the MTF can be improved, but at the cost of a reduced QE.

[0021] Various aspects of this disclosure relate to an image sensor IC having a trench isolation structure formed from the back side of a substrate, the trench isolation structure having conductive reflective elements to improve the MTF performance of the image sensor. The trench isolation structure is combined with a high-absorption structure to improve the QE of the image sensor. The high-absorption structure covers the photodetector of the image sensor in a radiation absorption region. The high-absorption structure includes multiple dielectric layers to promote wavelength-matched absorption. In the radiation absorption region, the substrate beneath the high-absorption structure has multiple protrusions to improve photon absorption. The high-absorption structure is configured and aligned with the shape of the multiple protrusions, thereby increasing the receiving surface area of ​​light incident on the substrate and effectively guiding the incident light to the photodetector below. Therefore, the trench isolation structure and the high-absorption structure enhance MTF performance and QE, thereby minimizing crosstalk and noise in the pixel region of the image sensor.

[0022] Figure 1 A cross-sectional view of an image sensor 100 illustrated in some embodiments includes an absorptive structure 126 and a trench isolation structure 140 having a reflective element 122.

[0023] Image sensor 100 includes a substrate 102 having a plurality of pixel regions 106, 114. In some embodiments, substrate 102 includes a semiconductor body (e.g., bulk silicon) and / or has a first doping type (e.g., p-type). The plurality of pixel regions 106, 114 each include a photodetector 128 configured to convert incident radiation (e.g., photons) into electrical signals (i.e., generate electron-hole pairs from the incident radiation). In some embodiments, photodetector 128 is an image sensing element or a photodiode. In some embodiments, photodetector 128 may include a second doping type (e.g., n-type) opposite to the first doping type.

[0024] Substrate 102 has a front surface 102f and a back surface 102b. Dielectric structure 104 is disposed on the front surface 102f of substrate 102. A plurality of pixel devices 112 are configured along the front surface 102f of substrate 102 and disposed within dielectric structure 104. In some embodiments, the plurality of pixel devices 112 may be a plurality of transistor devices. In some embodiments, the plurality of pixel devices 112 may include a gate electrode, a gate dielectric layer, a source electrode, and a drain electrode. Pixel devices 112 are electrically connected to each other and / or electrically connected to other semiconductor devices (not shown) through a plurality of conductive wirings 108 and a plurality of vias 110.

[0025] In various embodiments, the electrical signals generated by the photodetectors 128 of the plurality of pixel regions 106, 114 can be read by the plurality of pixel devices 112. For example, the plurality of pixel devices 112 may include one or more transfer transistors configured to selectively form conductive channels in the substrate 102 between a floating diffusion node (not shown) and an adjacent photodetector 128 to transfer accumulated charge in the photodetector 128 (e.g., by absorbing incident radiation) to the floating diffusion node.

[0026] A trench isolation structure 140 (also referred to as an isolation structure) extends from the back side surface 102b into the substrate 102. The trench isolation structure 140 is disposed between a plurality of pixel regions 106, 114 and separates the photodetectors 128 of the plurality of pixel regions 106, 114 from each other. In some embodiments, the trench isolation structure 140 laterally surrounds each photodetector 128. In some embodiments, the trench isolation structure 140 is a deep trench isolation (DTI) structure. The back side surface 102b of the substrate 102 on the photodetectors 128 includes a radiation-absorbing region 134, characterized by having a non-planar surface defined by a plurality of protrusions 142 arranged in a periodically repeating pattern. The plurality of protrusions 142 are disposed above the top of the photodetectors 128. In some embodiments, the plurality of protrusions 142 are triangular or pyramidal structures. In some embodiments, the plurality of protrusions 142 have… arrive Or from arrive or arrive The protrusion height. In other embodiments, the protrusion height is... or It is understood that the repeating pattern density of the triangular structure may differ from that shown in image sensor 100. For example, image sensor 100 shows four triangular protrusions, but in other embodiments (not shown), the number of triangular protrusions may be greater than or less than four. Furthermore, the height and spacing (size) of the triangular protrusions may differ from those shown. The number and size of the triangular protrusions can be configured to maximize the absorption of one or more wavelengths of electromagnetic radiation through the high-absorption structure 136. A first dielectric layer 116 and a second dielectric layer 118 are disposed along the repeating pattern of the triangular protrusions and form a repeating pattern of a zigzag layer on the photodetector 128.

[0027] In some embodiments, the trench isolation structure 140 includes a reflective element 122 and a padding layer 120 along the sidewalls and bottom surface of the reflective element 122. Furthermore, a high-absorption structure 136 extends over a photodetector within a radiation-absorbing region 134 on the back surface 102b of the substrate 102. The high-absorption structure 136 includes a plurality of dielectric layers, including a first dielectric layer 116 and a second dielectric layer 118 extending along the surface of the reflective element 122. In some embodiments, portions of the first dielectric layer 116 and the second dielectric layer 118 disposed between the reflective element 122 and the substrate 102 are part of the trench isolation structure 140. An absorption layer 126 is disposed on the high-absorption structure 136 within the radiation-absorbing region 134, and a dielectric cap layer 124 is disposed on the trench isolation structure 140, separating the absorption layer 126 of the pixel region 106 from the absorption layer 126 of the pixel region 114. Therefore, a dielectric cap layer 124 is disposed on the reflective element 122, and an absorption layer 126 extends between the sidewalls of the dielectric cap layer 124. In some embodiments, the dielectric cap layer 124 and the absorption layer 126 have top horizontal surfaces that are coplanar or substantially coplanar with each other. In some embodiments, the dielectric cap layer 124 and the absorption layer 126 are composed of the same material. In other embodiments, the dielectric cap layer 124 is composed of a first material, and the absorption layer 126 is composed of a second material different from the first material. Since the dielectric cap layer 124 is aligned above the reflective element 122, the dielectric cap layer 124, composed of a first material different from the second material, can help increase the isolation between pixel regions while maximizing radiative transmission through the absorption layer 126.

[0028] Reflective element 122 is configured to reflect electromagnetic radiation incident on back surface 102b back to the corresponding photodetector 128. In some embodiments, reflective element 122 may be or include a metal, copper, aluminum, tungsten, or other suitable conductive material. Because reflective element 122 is configured to reflect electromagnetic radiation, it reduces crosstalk between adjacent pixel regions (e.g., pixel region 106 and pixel region 114). For example, when incident radiation 132 toward pixel region 106 strikes an interface between one or more of the absorption layer 126, the high absorption structure 136, and the substrate 102, a portion of the incident radiation 132 may be reflected toward pixel region 114 adjacent to pixel region 106. Reflective element 122 is configured to coherently reflect this portion of the incident radiation 132 back to pixel region 106, thereby reducing crosstalk and further improving the MTF performance of image sensor 100.

[0029] A high-absorption structure 136 covers and conforms to the shape of a plurality of protrusions 142. In some embodiments, a first dielectric layer 116 and a second dielectric layer 118 of the high-absorption structure 136 separate the reflective element 122 from the substrate 102. The first dielectric layer extends vertically or substantially vertically through the back side surface 102b into the substrate 102 and is located between the reflective element 122 and the substrate 102. The second dielectric layer 118 is disposed on the first dielectric layer 116, wherein the second dielectric layer 118 extends vertically into the substrate along the surface of the first dielectric layer 116. The second dielectric layer is disposed on the sidewalls and bottom surface of the reflective element 122. In some embodiments, a pad layer 120 is disposed between the reflective element 122 and the second dielectric layer 118, and the pad layer 120 is disposed on the bottom surface of the reflective element 122. In some embodiments, the pad layer 120 extends from a horizontal surface common to the top surface of the reflective element 122 and the second dielectric layer 118.

[0030] In some embodiments, the pad layer 120 is a diffusion barrier layer. The pad layer 120 prevents diffusion between the reflective element 122 and the second dielectric layer 118 and reduces capacitance between the substrate 102 and the reflective element 122. In some embodiments, the pad layer 120 minimizes light absorption by the reflective element 122, thereby maximizing light reflection within the plurality of pixel regions 106, 114. In some embodiments, the pad layer 120 may be or comprise an alloy or stack of materials such as titanium, aluminum, titanium aluminum, tantalum, tantalum nitride, other conductive materials, or metals. In other embodiments, the pad layer 120 may be or comprise a low dielectric constant material, such as silicon dioxide, silicon carbonitride, boron oxide, silica, or the like. As used herein, a low dielectric constant material refers to a dielectric material with a dielectric constant less than 3.9 or less than 2.7.

[0031] In some embodiments, the first dielectric layer 116 and the second dielectric layer 118 comprise the same material; in other embodiments, the first dielectric layer 116 and the second dielectric layer 118 comprise different dielectric materials relative to each other. For example, both the first dielectric layer 116 and the second dielectric layer 118 can be low dielectric constant materials or oxides, such as silicon oxides (e.g., SiO2, SiCO, etc.) or boron oxides (e.g., borosilicate glass (BSG), B2O3). In other embodiments, the first dielectric layer 116 is a high dielectric constant material (e.g., alumina, hafnium oxide, etc.), while the second dielectric layer 118 is an oxide. As used herein, a high dielectric constant material refers to a dielectric material with a dielectric constant greater than 3.9. Furthermore, the absorber layer 126 can be or includes oxides (e.g., one or more of SiO2, SiCO, B2O3, etc.). In some embodiments, the absorber layer 126 comprises the same material as the second dielectric layer 118; in other embodiments, the absorber layer 126 is a different material from the second dielectric layer 118 (e.g., a different oxide or an oxide of a different density).

[0032] A high-absorption structure 136 extends along the top surface (e.g., back surface 102b) of the substrate 102 in a radiation-absorbing region 134 above the photodetector 128. A first dielectric layer 116 and a second dielectric layer 118 are disposed above a plurality of protrusions 142 on the back surface 102b of the substrate 102. Therefore, the first dielectric layer 116 and the second dielectric layer 118 have a plurality of surfaces that conform to the shape of the plurality of protrusions 142 and increase the receiving surface area of ​​light incident on the back surface 102b of the substrate 102. In some examples, the top surface of the second dielectric layer 118 periodically extends from above the top surface 116t of the first dielectric layer 116 to a plane p1 below the top surface of the first dielectric layer. An absorption layer 126 is disposed on the second dielectric layer 118 and extends into a periodically repeating recess 146 located below the top surface of the second dielectric layer 118 and aligned downward with a periodically repeating pattern of a plurality of protrusions 142.

[0033] The shape and / or material of the first dielectric layer 116 and the second dielectric layer 118 in the high-absorption structure 136, combined with the absorption layer 126 and the plurality of protrusions 142, enhances the transmission of light of the desired wavelength toward the photodetector 128. Therefore, the first dielectric layer 116, the second dielectric layer 118, and the absorption layer 126 improve the QE of the image sensor 100. Thus, by combining the plurality of protrusions 142 with the high-absorption structure 136 in the radiation absorption region 134 and providing the reflective element 122 in the trench isolation structure 140, the image sensor 100 achieves improved MTF performance and improved QE.

[0034] Figure 2Cross-sectional views illustrating some embodiments of an image sensor 200 including a high-absorption structure 136 and a trench isolation structure 140 having a reflective element 122. Figure 2 Image sensor 200 description Figure 1 Other embodiments of the image sensor 100, wherein the image sensor 200 includes a plurality of microlenses 206, a plurality of filters 204, and a mesh structure 208 disposed above the back surface 102b of the substrate 102.

[0035] The image sensor 200 includes a lower dielectric layer 202 disposed on the back surface 102b of a substrate 102. A mesh structure 208 is disposed in the lower dielectric layer 202 and aligned between photodetectors 128 in multiple pixel regions 106, 114. Multiple filters 204 are disposed on the lower dielectric layer 202. Multiple microlenses 206 are disposed on the multiple filters 204.

[0036] Multiple microlenses 206 are configured to direct incident light toward a photodetector 128. Multiple filters 204 each comprise a material configured to allow wavelengths in a first range to pass while blocking wavelengths in a second range. A mesh structure 208 and a trench isolation structure 140 provide electrical and / or optical isolation between multiple pixel regions 106, 114. The photodetector 128 is configured to absorb incident light (e.g., photons) received by the microlenses 206 and generate respective electrical signals corresponding to the incident light.

[0037] The image sensor 200 also includes an STI structure 210 disposed in the substrate 102 and aligned below the trench isolation structure 140. The STI structure 210 may comprise one or more dielectric materials and is arranged on the front surface 102f of the substrate. In some embodiments, the STI structure 210 may extend from the front surface 102f to the bottom surface of the trench isolation structure 140. In other embodiments (not shown), the substrate 102 separates the STI structure 210 from the trench isolation structure 140. In some embodiments, the width of the STI structure 210 is wider than the width of the trench isolation structure 140. In other embodiments (not shown), the width of the STI structure 210 is narrower than the width of the trench isolation structure 140. The STI structure may provide additional electrical isolation and / or reduce leakage current of the plurality of pixel devices 112 between the photodetectors 128 of the plurality of pixel regions 106, 114.

[0038] Figure 3 A cross-sectional view illustrating some embodiments of an image sensor 300 with different height reflective elements.

[0039] Image sensor 300 displays reflective elements 122 with different heights. Reflective element 122 displays a first reflective portion 302 disposed between pixel region 106 and pixel region 114, and a second reflective portion 304 laterally offset from pixel region 106. The height of the first reflective portion 302 is less than the height of the second reflective portion 304. For example, the first reflective portion 302 and the second reflective portion 304 have bottom surfaces that are substantially flush with each other. The second reflective portion 304 has a top surface shared with the top surface of the second dielectric layer 118. The first reflective portion 302 has a top surface that is recessed by a vertical height offset 306 from the top surface of the second dielectric layer 118. Therefore, the height difference between the first reflective portion 302 and the second reflective portion 304 is a vertical height offset 306. Thus, the top surface of the first reflective portion 302 is recessed from the top surface of the second reflective portion 304.

[0040] A dielectric cap layer 124, aligned above the first reflective portion 302, extends between the inner sidewalls of the second dielectric layer 118 and extends from the first reflective portion 302 to the lower dielectric layer 202. In some embodiments, the top surface of the padding layer 120 lining the first reflective portion 302 is substantially flush with the top surface of the first reflective portion 302. Therefore, in some embodiments, the dielectric cap layer directly contacts the top surfaces of the padding layer 120 and the first reflective portion 302, located below the top surfaces of one or more first dielectric layers 116 or second dielectric layers 118. In some embodiments, the top portion of the dielectric cap layer 124 extending above the second dielectric layer 118 has a width greater than the bottom portion of the dielectric cap layer 124 extending between the sidewalls of the second dielectric layer 118 and located below the top surface of the second dielectric layer 118.

[0041] The height of the reflective element 122 can be configured to reflect one or more wavelengths of electromagnetic radiation toward the photodetector 128. For example, in some embodiments, the height of one or more portions of the reflective element 122 surrounding the photodetector 128 of pixel region 106 may vary or be a fixed height, which differs from the photodetector 128 of pixel region 114. Furthermore, it is understood that the width or thickness of the reflective element 122 may vary, wherein, for example (not shown), the width or vertical profile (e.g., taper) of the first reflective portion 302 differs from the width or vertical profile of the second reflective portion 304. The height or vertical profile of the reflective element 122 can be set according to one or more wavelengths of electromagnetic radiation to achieve coherent reflection from the reflective element 122 toward the photodetector 128. That is, the reflected energy constructively interferes to maximize the reception of one or more wavelengths of light by the photodetector.

[0042] Figure 4 A cross-sectional view illustrating some embodiments of an image sensor 400 having multiple rectangular protrusions 404.

[0043] Image sensor 400 provides relative to Figures 1 to 3 Other cross-sections of the radiation absorption region 402 of the radiation absorption region 134. The back surface 102b of the substrate 102 is non-planar and defined by a plurality of protrusions 404 arranged in a periodically repeating rectangular shape (also referred to as trench shape). A first dielectric layer 116 and a second dielectric layer 118 are disposed along the repeating rectangular shape protrusion pattern, such that the first dielectric layer 116 and the second dielectric layer 118 form a repeating zigzag pattern of layers on the photodetector 128, thereby forming a high absorption structure 136 on the photodetector 128. It is understood that the repeating pattern density of the rectangular shape protrusions may differ from that shown in the image sensor 400. For example, the image sensor 400 shows five rectangular shape protrusions, but in other embodiments (not shown), the number of rectangular shape protrusions may be greater than or less than five. Furthermore, the height and width (dimensions) of the rectangular shape protrusions may be set differently from those shown. The number and size of the rectangular shape protrusions may be set to maximize the absorption of one or more wavelengths of electromagnetic radiation through the high absorption structure 136. Understandable, although Figures 1 to 3 It displays multiple protrusions 142 with a triangular structure, but Figures 1 to 3 It can be modified to replace the triangular structure with the rectangular structure of the image sensor 400, or vice versa.

[0044] Figure 5A A cross-sectional view illustrating some embodiments of an image sensor 500a including a high-absorption structure 136 and a trench isolation structure 140 having a reflective element 122.

[0045] Image sensor 500a shows other alternative embodiments, in which the absorption layer 126 is disposed on the reflective element 122, rather than as shown. Figure 1A dielectric cap layer 124 is provided on the reflective element 122. An absorption layer 126 is provided along the second dielectric layer 118, wherein the absorption layer 126 extends from the lower surface of the second dielectric layer 118 to the top surface of the second dielectric layer 118 in a radiation absorption region 134. The reflective element 122 and the pad layer 120 are recessed below the top surfaces of one or more first dielectric layers 116 and second dielectric layers 118. In some embodiments, the absorption layer 126 is part of a trench isolation structure 140 and is provided on the top surfaces of the reflective element 122 and the pad layer 120. Thus, the absorption layer 126 extends from the reflective element 122 and the pad layer 120 to the top surface of the second dielectric layer 118. Accordingly, the absorption layer 126 is disposed between the inner sidewalls of the second dielectric layer 118 and extends from a horizontal surface common to the top surfaces of the pad layer 120 and the reflective element 122 to the top surface of the second dielectric layer 118. The image sensor 500a can achieve improved MTF performance and improved QE through a simpler manufacturing process.

[0046] Figure 5B A cross-sectional view illustrating an embodiment of an image sensor 500b having a high absorption structure 136 and a trench isolation structure 140 having a reflective element 122.

[0047] Image sensor 500b shows another embodiment of the absorption layer 126 relative to image sensor 500a. As shown in image sensor 500b, the absorption layer 126 extends from the lower surface of the reflective element 122, the pad layer 120, and the second dielectric layer 118 to a plane disposed above the second dielectric layer 118. In some embodiments, the height of the absorption layer 126 may be configured to extend above the second dielectric layer 118. The height of the absorption layer 126 may be configured to maximize the absorption of one or more electromagnetic radiation wavelengths. Although image sensors 500a and 500b show protrusions 142 having multiple triangular structures, it will be understood that the multiple protrusions 142 of image sensors 500a and 500b may be rectangular structures, for example... Figure 4 As shown (and vice versa).

[0048] Figure 6A A cross-sectional view illustrating an embodiment of an image sensor 600a having a high absorption structure 136 and a trench isolation structure 140 having a reflective element 122.

[0049] Image sensor 600a displays relative to Figure 4 Other embodiments of the image sensor 400, wherein Figure 4The dielectric cap layer 124 and the absorber layer 126 are omitted in the image sensor 600a. Therefore, the lower dielectric layer 202 is disposed on the second dielectric layer 118, the pad layer 120, and the reflective element 122. Furthermore, a mesh structure 208 is disposed on the reflective element. Thus, the second dielectric layer 118 has a flat top surface and an irregular bottom surface extending below the top surface of the first dielectric layer 116. The image sensor 600a can achieve improved MTF performance and improved QE through a simpler manufacturing process.

[0050] Figure 6B A cross-sectional view illustrating some embodiments of an image sensor 600b having a trench isolation structure 140.

[0051] Image sensor 600b display Figure 6A The lower portion of the trench isolation structure 140. Specifically, the image sensor 600b displays the relative thickness or width of the pad layer 120, the first dielectric layer 116, and the second dielectric layer 118. In some embodiments, the first dielectric layer 116 has… arrive The first thickness is 602. In some embodiments, the second dielectric layer 118 has arrive The second thickness is 604. In some embodiments, the padding layer 120 has arrive The third thickness is 606. Therefore, thicknesses 602, 604, and 606 can be configured to achieve improved MTF performance and improved QE of the image sensor 600b.

[0052] Figure 7 Cross-sectional views illustrating some embodiments of an image sensor 700 including a trench isolation structure 140 and different radiation absorption regions.

[0053] The image sensor 700 displays a pixel region 708a having a radiation absorption region 706a, which has a first plurality of protrusions 704a of a triangular structure on the back surface 102b of the substrate 102. Previously, according to... Figures 1 to 3 , Figure 5A and Figure 5B The aspects related to triangle structures discussed also apply to Figure 7 At a lateral offset from pixel region 708a is pixel region 708b, which has a radiation-absorbing region 706b and a second plurality of rectangular protrusions 704b on the back surface 102b of substrate 102. Previously, according to... Figure 4 and Figure 6A The aspects discussed regarding rectangular structures also apply to... Figure 7Therefore, radiation absorption regions 706a and 706b have different structures for their respective first plurality of protrusions 704a and second plurality of protrusions 704b.

[0054] In some embodiments, pixel region 704a has a first photodetector 702a disposed in substrate 102, and pixel region 704b has a second photodetector 702b disposed in substrate 102. Trench isolation structure 140 is spaced between the first photodetector 702a and the second photodetector 702b. A first plurality of protrusions 704a cover the first photodetector 702a, and a second plurality of protrusions 704b cover the second photodetector 702b. The first plurality of protrusions 704a have a first shape, and the second plurality of protrusions have a second shape different from the first shape.

[0055] Therefore, the first plurality of protrusions 704a and the second plurality of protrusions 704b, with different shapes, can provide tailored light absorption for electromagnetic radiation of different wavelengths. For example, the first plurality of protrusions 704a can be configured to effectively absorb a first wavelength, and the second plurality of protrusions 704b can be configured to effectively absorb a second wavelength, wherein the first wavelength is different from the second wavelength. Thus, each pixel region can be configured to correspond to a specific wavelength according to the radiation absorption region of that pixel region and the structure of the trench isolation structure 140, to achieve improved MTF performance and improved QE of the image sensor 700.

[0056] It is understood that in some embodiments, the first plurality of protrusions 704a may have four triangular structures, and the second plurality of protrusions 704b may have five rectangular structures. Therefore, the first plurality of protrusions 704a may have fewer protrusions than the second plurality of protrusions 704b. In other embodiments (not shown), the first plurality of protrusions 704a may have more protrusions than the second plurality of protrusions 704b. The number and size of the protrusions in one or more of the first plurality of protrusions 704a or the second plurality of protrusions 704b may be set according to one or more wavelengths to be absorbed, as previously described. Figure 1 and Figure 4 The subject of discussion.

[0057] Although Figures 1 to 7 While individual figures may show specific arrangements of radiation absorption regions or isolation structures, it is understandable that a particular feature of one figure can be replaced by a feature of another figure.

[0058] Figures 8 to 21 Various views 800 to 2100 illustrate some embodiments of a method for forming a semiconductor device or image sensor including a high-absorption structure and a trench isolation structure with reflective elements. Although Figures 8 to 21 The various views 800 to 2100 shown are described with reference to this method, but it will be understood that... Figures 8 to 21 The structure shown is not limited to this method and can exist independently of it. Furthermore, although... Figures 8 to 21 The actions are described as a series of steps, but it will be understood that these actions are not limited, as the order of these actions can be changed in other embodiments, and the disclosed method is also applicable to other structures. In other embodiments, some of the actions illustrated and / or described may be omitted in whole or in part. Furthermore, although the method describes the formation of a back-side image (BSI) sensor, it will be understood that the disclosed trench isolation structure can also be used for a front-side image (FSI) sensor.

[0059] As shown in cross-sectional view 800, a substrate 102 is provided having a back-side surface 102b and a front-side surface 102f. The substrate 102 can be any type of semiconductor body (e.g., silicon, SiGe, SOI, etc.), and any other type of semiconductor and / or epitaxial layer associated therewith. For example, in some embodiments, the substrate 102 may include a base substrate and an epitaxial layer. In some embodiments, the substrate 102 may include a silicon substrate.

[0060] A photodetector 128 is formed in a plurality of pixel regions 106, 114 of substrate 102. In some embodiments, the photodetector 128 may include a photodiode formed by implanting one or more dopants into the front surface 102f of substrate 102. For example, the photodiode may be formed (not shown) by selectively performing a first implantation process (e.g., according to a masking layer) to form a first region having a first doping type (e.g., n-type), followed by performing a second implantation process to form a second region adjacent to the first region and having a second doping type (e.g., p-type) different from the first doping type. In some embodiments, either the first or second implantation process may also be used to form a floating diffusion well (not shown).

[0061] Multiple pixel devices 112 are formed on the front surface 102f of the substrate 102, within multiple pixel regions 106, 114. In various embodiments, the multiple pixel devices 112 may correspond to a transfer transistor, a source-follower transistor, a row select transistor, and / or a reset transistor. In some embodiments, the multiple pixel devices 112 may be formed by depositing a gate dielectric film and a gate electrode film on the front surface 102f. The gate dielectric film and the gate electrode film are then patterned to form a gate dielectric layer and a gate electrode. Sidewall spacers may be formed on the outer sidewalls of the gate electrode. In some embodiments, the sidewall spacers may be formed by depositing a spacer layer (e.g., nitride, oxide, etc.) on the front surface 102f of the substrate 102 and selectively etching the spacer layer.

[0062] In some embodiments, one or more shallow trench isolation (STI) structures 802 may be formed in the front surface 102f of the substrate 102, located on opposite sides of the plurality of pixel regions 106, 114. Thus, the STI structure 802 is situated between the photodetectors 128 of the plurality of pixel regions 106, 114. The STI structure 802 may (not shown) be formed by selectively etching the front surface 102f of the substrate 102 to form shallow trenches, followed by forming one or more dielectric materials in the shallow trenches. In some embodiments, the STI structure 802 may be formed prior to the formation of the plurality of pixel devices 112 and / or the photodetectors 128.

[0063] like Figure 9As shown in cross-sectional view 900, a dielectric structure 104 is formed on the front surface 102f of a substrate 102. A plurality of conductive interconnect layers 902 are formed within the dielectric structure 104 and along the front surface 102f of the substrate 102. In some embodiments, the dielectric structure 104 includes a plurality of stacked inter-level dielectric (ILD) layers, and the plurality of conductive interconnect layers 902 include alternating conductive wiring layers 108 and a plurality of vias 110. In some embodiments, one or more of the plurality of conductive interconnect layers 902 may be formed using a damascene process (e.g., a single damascene process or a dual damascene process). The damascene process is performed by forming an ILD layer on the front surface 102f of the substrate 102, etching the ILD layer to form vias and / or metal trenches, and filling the vias and / or metal trenches with a conductive material. In some embodiments, the ILD layer may be deposited using physical vapor deposition techniques (e.g., chemical vapor deposition (CVD), plasma vapor deposition (PVD), plasma-enhanced CVD (PE-CVD), atomic layer deposition (ALD), etc.), while the conductive material may be formed using deposition processes and / or electroplating processes (e.g., electroplating, electroless plating, etc.). In various embodiments, the plurality of conductive interconnect layers 902 may include, for example, tungsten, copper, or aluminum-copper.

[0064] like Figure 10 As shown in the sectional view 1000, firstly... Figure 9 The fabricated portion is flipped along a horizontal axis. A first patterned mask layer 1002 is formed along the back surface 102b of the substrate 102. The first patterned mask layer 1002 includes sidewalls defining an opening 1004 along the back surface 102b of the substrate 102. In some embodiments, the first patterned mask layer 1002 can be formed by depositing a layer of photosensitive material (e.g., positive or negative photoresist) along the back surface 102b of the substrate 102. The photosensitive material layer is selectively exposed to electromagnetic radiation depending on the photomask. The electromagnetic radiation alters the solubility of the exposed areas in the photosensitive material to define soluble regions. The photosensitive material is then developed, and the opening 1004 in the photosensitive material is defined by removing the soluble regions. The opening 1004 is formed directly above the photodetectors 128 in the plurality of pixel regions 106, 114.

[0065] like Figure 11 As shown in the sectional view 1100, according to Figure 10A first patterned mask layer 1002 is used to perform a first etching process on the back surface 102b of the substrate 102. The first etching process is performed by exposing the substrate 102 to one or more etchants in the presence of the first patterned mask layer 1002. One or more etchants remove portions of the substrate 102 to define a plurality of recesses 1106 arranged between a plurality of protrusions 142 extending outwardly from the substrate 102. The plurality of protrusions 142 form a repeating periodic pattern of individual protrusions 1108 and have an outer boundary confined within the projected area of ​​the pixel region 106. In some embodiments, the first etching process may include a dry etching process. For example, the first etching process may include a plasma-coupled etching process, such as an inductively coupled plasma (ICP) etching process or a capacitively coupled plasma (CCP) etching process. In other embodiments, the first etching process may include a wet etching process.

[0066] In some embodiments, the repeating shape of each individual protrusion 1108 has a triangular or pyramidal shape, with its shape width (or spacing) and shape height corresponding to the height of one of the plurality of recesses 1106. The individual protrusions 1108 are separated from each other by a shape distance 1102. The shape height and width (or spacing) can be configured to maximize the transmission of light of a specific wavelength to the photosensor 128. In some embodiments (not shown), the plurality of protrusions 142 are rectangular in shape, for example... Figure 4 As shown.

[0067] like Figure 12 As shown in the cross-sectional view 1200, a second etching process is performed on the back surface 102b of the substrate 102 according to the second patterned mask layer 1202. The second etching process forms an isolation trench 1204, which will subsequently accommodate the trench isolation structure 140. The isolation trench 1204 exposes the inner sidewalls of the substrate 102 and the top surface of the STI structure 802. The isolation trench 1204 is formed around the sides of the photodetectors 128 in the plurality of pixel regions 106, 114. The second etching process is performed by exposing the unmasked areas of the substrate 102 to one or more etchants that remove portions of the substrate 102 in the unmasked areas to form the isolation trench 1204 of the trench isolation structure 140. In some embodiments, the isolation trench 1204 has tapered sidewalls such that the width of the isolation trench 1204 decreases as the distance from the back surface 102b of the substrate 102 to the front surface 102f of the substrate increases.

[0068] like Figure 13As shown in the cross-sectional view 1300, the second patterned mask layer 1202 is removed. In some embodiments, the second patterned mask layer is removed by chemical cleaning, etching, ashing, or other suitable removal processes. A first dielectric layer 116 is deposited on the exposed surfaces of the STI structure 802 and the substrate 102. In some embodiments, the first dielectric layer 116 is formed on the pads of the sidewalls and bottom surface of the isolation trench 1204, which are the top surface of the STI structure 802 and the sidewall of the substrate 102, respectively. Furthermore, the first dielectric layer 116 is formed on the back surface 102b of the substrate 102, for example, on a plurality of protrusions 142. In some embodiments, the first dielectric layer 116 may be or comprise a high-k dielectric layer, including hafnium oxide (HfO2), titanium oxide (TiO2), hafnium zirconium oxide (HfZrO), tantalum oxide (Ta2O3), hafnium silicon oxide (HfSiO4), zirconium oxide (ZrO2), zirconium silicon oxide (ZrSiO2), etc. In some embodiments, the first dielectric layer 116 can be deposited using deposition techniques (e.g., PVD, CVD, PE-CVD, ALD, etc.). In some embodiments, the first dielectric layer 116 is formed having arrive The first thickness or other suitable value.

[0069] like Figure 14 As shown in cross-sectional view 1400, a second dielectric layer 118 is deposited on the exposed surface of the first dielectric layer 116. The second dielectric layer 118 is formed on the first dielectric layer 116 within an isolation trench 1204 and on the back side surface of the substrate, with a plurality of protrusions 142 aligned above it. In some embodiments, the second dielectric layer 118 is formed by a deposition process such as ALD or other suitable processes (e.g., PVD, CVD, PE-CVD, etc.). In other embodiments, the second dielectric layer 118 is formed by a liquid oxide process. For example, the second dielectric layer 118 can be deposited using a liquid precursor (e.g., sol-gel) via a liquid phase process. In other examples, the second dielectric layer 118 is deposited via a sine-on process. The second dielectric layer 118 may be or comprise aluminum oxide (Al2O3), hafnium oxide (HfO2), ZrO2, titanium oxide (TiO2), silicon oxide (SiO2), tantalum oxide (Ta2O5), or the like. In some embodiments, the second dielectric layer 118 is formed having arrive The second thickness. The first dielectric layer 116 and the second dielectric layer 118 form a high absorption structure 136.

[0070] like Figure 15As shown in the cross-sectional view 1500, a pad layer 120 is deposited on the second dielectric layer 118. The pad layer 120 is deposited on the second dielectric layer 118 within the isolation trench 1204 and on the back surface 102b of the substrate 102. Therefore, the pad layer 120 is formed over a plurality of protrusions 142. In some embodiments, the pad layer 120 is a zero barrier layer to prevent diffusion. In some embodiments, the pad layer 120 may be or comprise an alloy or stack of materials such as tantalum, tantalum nitride, copper, aluminum, tungsten, rhodium, ruthenium, silver, gold, cobalt, iron, molybdenum, titanium, chromium, or other conductive materials or metals. In other embodiments, the pad layer 120 may be or comprise a low dielectric constant dielectric. The pad layer 120 can be deposited by a deposition process (e.g., PVD, CVD, PE-CVD, ALD, etc.). In some embodiments, the pad layer 120 is formed having arrive The third thickness. In some embodiments (not shown), the padding layer 120 may be omitted.

[0071] A conductive layer 1502 is formed within an isolation trench 1204 and on the back surface 102b of a substrate 102, covering a plurality of protrusions 142. The conductive layer 1502 is formed between the inner sidewalls of the liner layer 120 within the isolation trench 1204, thereby filling the central portion of the isolation trench 1204. In some embodiments, the deposited conductive layer 1502 has an upper surface comprising a plurality of curved surfaces arranged on and intersecting each other on the plurality of protrusions 142. The conductive layer 1502 may be or comprise metal, copper, aluminum, tungsten, rhodium, ruthenium, silver, gold, cobalt, iron, molybdenum, titanium, chromium, or other suitable conductive materials, and is deposited by a deposition process (e.g., PVD, CVD, PE-CVD, ALD, etc.).

[0072] like Figure 16 As shown in the cross-sectional view 1600, a removal process (also referred to as a first removal process) is performed to remove the pad layer 120 and conductive layer 1502 located above the photodetector 128 aligned with the plurality of protrusions 142. In some embodiments, the removal process is a planarization process (e.g., a chemical mechanical planarization process) to form a substantially flat surface aligned with the upper surface. The removal process is performed from (e.g., Figure 15 The conductive layer 1502 within the isolation trench 1204 forms a reflective element 122, wherein the padding layer 120 remains (e.g., Figure 15 The isolation trench 1204 is located within the reflective element 122 and shares a common top surface. The removal process is performed (e.g., Figure 15A trench isolation structure 140 is formed within the isolation trench 1204, wherein the trench isolation structure 140 has a high absorption structure 136, the high absorption structure 136 including a first dielectric layer 116 and a second dielectric layer 118. The trench isolation structure 140 also includes a pad layer 120 and a reflective element 122.

[0073] In some embodiments, the removal process removes (e.g., Figure 15 A portion of the second dielectric layer 118, the pad layer 120, and the conductive layer 1502 are located above the plurality of protrusions 142. Pad residue 120r of the pad layer 120 remains on the second dielectric layer 118 above the plurality of protrusions 142, and conductive layer residue 1502r of the conductive layer 1502 remains on the pad residue 120r above the plurality of protrusions 142. Therefore, after the removal process, portions of the pad layer 120 and the conductive layer 1502 remain above the plurality of protrusions 142.

[0074] like Figure 17 As shown in cross-sectional view 1700, a third dielectric layer 1702 is formed over the second dielectric layer 118 in the region above the trench isolation structure 140, the liner residue 120r, the conductive layer residue 1502r, and the plurality of protrusions 142. The third dielectric layer 1702 can be deposited by a deposition process (e.g., PVD, CVD, PE-CVD, ALD, etc.). The third dielectric layer 1702 can be or contains aluminum oxide (Al2O3), hafnium oxide (HfO2), ZrO2, titanium oxide (TiO2), silicon oxide (SiO2), tantalum oxide (Ta2O5), or the like. In some embodiments, the third dielectric layer 1702 is the same material as the second dielectric layer 118. In other embodiments, the third dielectric layer 1702 is a different material from the second dielectric layer 118. The material selection of the third dielectric layer depends on the light wavelength associated with the pixel regions 106, 114.

[0075] like Figure 18 The sectional view 1800 is shown (for example, Figure 17 The third dielectric layer 1702 is patterned to form a dielectric cap layer 124 over the trench isolation structure and the pad layer 120, exposing the liner residue 120r and conductive layer residue 1502r over the plurality of protrusions 142. The third dielectric layer 1702 is patterned according to a suitable patterning process, such as the patterning process previously described herein.

[0076] like Figure 19 As shown in the cross-sectional view 1900, above the plurality of protrusions 142 (e.g., Figure 18The liner residue 120r and conductive layer residue 1502r are removed by a removal process (also known as a second removal process), such as chemical cleaning, etching, ashing, or similar processes. After the removal process, the top surface of the second dielectric layer 118 is exposed in the region above the plurality of protrusions 142. In some examples, with Figure 16 The related first removal process is different from that of Figure 19 The related second removal process.

[0077] like Figure 20 As shown in the cross-sectional view 2000, an absorption layer 126 is formed on a second dielectric layer 118 above a plurality of protrusions 142 and between the inner sidewalls of a dielectric cap layer 124. The absorption layer 126 may be or comprise an oxide (e.g., silicon oxide). The absorption layer 126 may be deposited by a deposition process (e.g., PVD, CVD, PE-CVD, ALD, etc.). In some embodiments, the absorption layer 126 may be deposited to have an upper surface comprising a plurality of curved surfaces arranged above the plurality of protrusions 142. In some embodiments, the plurality of curved surfaces may be removed by a subsequent planarization process (e.g., chemical mechanical planarization) to form a substantially flat upper surface. A high-absorption structure 136, combined with the absorption layer 126 aligned above the plurality of protrusions 142, forms a radiation-absorbing region 134.

[0078] like Figure 21 As shown in the cross-sectional view 2100, a mesh structure 208 is formed on a dielectric cap layer 124. A lower dielectric layer 202 is formed over the mesh structure 208 and on the absorption layer 126 and the dielectric cap layer 124. A plurality of filters 204 are formed on the lower dielectric layer 202, and a plurality of microlenses 206 are formed on the plurality of filters 204. In some embodiments, the plurality of filters 204 can be formed by forming a color filter layer and patterning the color filter layer. The color filter layer is formed of a material that allows radiation (e.g., light) within a specific wavelength range to pass through while blocking light of wavelengths outside the specified range. In some embodiments, the plurality of microlenses 206 can be formed by depositing microlens material over the plurality of filters 204 (e.g., by spin coating or deposition process). A microlens template (not shown) having a curved surface is patterned over the microlens material. In some embodiments, the microlens template may comprise a photoresist material exposed using a distributed exposure dose (e.g., for negative photoresist, more light is exposed at the bottom of the curvature and less light at the top of the curvature), developed and baked to form a circular shape. The microlens material is then selectively etched according to the microlens template to form a plurality of microlenses 206.

[0079] Thus, an improved image sensor chip is provided, having a BSI structure with a trench isolation structure including a reflective element and a high-absorption structure extending from the trench isolation structure to a radiation-absorbing region aligned above a plurality of protrusions above a photodetector. By combining the plurality of protrusions in the radiation-absorbing region with the high-absorption structure and the reflective element in the trench isolation structure, the image sensor achieves improved modulation transfer function (MTF) performance and improved quantum efficiency (QE).

[0080] Figures 22 to 25 Various views 2200 to 2500 illustrate some embodiments of a method for forming a semiconductor device or image sensor, the image sensor including a high-absorption structure and a trench isolation structure with reflective elements. Although Figures 22 to 25 The various views 2200 to 2500 shown are described with reference to this method, but it should be understood that... Figures 22 to 25 The structure shown is not limited to this method, but can exist independently of it. Furthermore, although... Figures 22 to 25 The actions are described as a series of steps, but it should be understood that these actions are not limited, as the order of the actions can be changed in other embodiments, and the disclosed method is also applicable to other structures. In other embodiments, some of the actions illustrated and / or described may be omitted in whole or in part. Furthermore, although the method describes the formation of a BSI sensor, it should be understood that the disclosed trench isolation structure can also be used for front-illuminated (FSI) sensors.

[0081] The following discussion Figure 22 The method is to continue Figure 15 After that. Therefore, according to Figure 22 The characteristics of the discussion stem from Figure 15 The structure.

[0082] like Figure 22 As shown in the sectional view 2200, (e.g.) Figure 15 The conductive layer 1502 and the pad layer 120 undergo a removal process (also referred to as a first removal process) to remove the pad layer 120 and the conductive layer 1502 from the top surface of the second dielectric layer 118 aligned above the photodetector. The removal process can be, for example, chemical cleaning, etching, ashing, or a similar process. After the removal process, in (e.g.) Figure 15 A reflective element 122 is formed from the conductive layer 1502 within the isolation trench 1204, and the top surface of the second dielectric layer 118 above the photodetector is exposed. The padding layer 120 and the conductive layer 1502, aligned above the plurality of protrusions 142, are removed, and the top surfaces of the padding layer 120 and the reflective element 122 within the isolation trench are recessed below the top surface of the second dielectric layer 118. In some embodiments, a first removal process removes (not shown) the top portion of the second dielectric layer 118.

[0083] like Figure 23 As shown in cross-sectional view 2300, an absorption layer 126 is formed on the second dielectric layer 118 and between the inner sidewalls of the second dielectric layer 118 aligned above the top surface of the reflective element 122 and the pad layer 120. In some embodiments, the deposited absorption layer 126 has an upper surface comprising a plurality of curved surfaces arranged above and intersecting with each other, including a plurality of protrusions 142. Therefore, the upper surface of the absorption layer 126 is irregular and non-planar. The absorption layer 126 can be deposited by a deposition process (e.g., PVD, CVD, PE-CVD, ALD, etc.).

[0084] like Figure 24 As shown in the cross-sectional view 2400, a removal process (also referred to as a second removal process) is performed on the absorber layer 126. Therefore, the upper surface of the absorber layer 126, which includes multiple curved surfaces, is removed, and the top surface of the absorber layer 126 is substantially planar. In some embodiments, the removal process is a planarization process (e.g., a chemical mechanical planarization process). In some embodiments, Figure 23 The first removal process and Figure 24 The second removal process is a different type of removal process.

[0085] like Figure 25 As shown in the cross-sectional view 2500, a mesh structure 208 is formed on the absorption layer 126. A lower dielectric layer 202 is formed above the mesh structure 208 and on the absorption layer 126. A plurality of filters 204 are formed on the lower dielectric layer 202, and a plurality of microlenses 206 are formed on the plurality of filters 204. The mesh structure 208, the lower dielectric layer 202, the plurality of filters 204, and the plurality of microlenses 206 are configured according to a previously disclosed... Figure 21 The described method is formed.

[0086] Therefore, an improved image sensor chip is provided, having a BSI structure comprising a trench isolation structure including a reflective element, and a high-absorption structure extending from the trench isolation structure over a radiation-absorbing region aligned above a plurality of protrusions above a photodetector. By combining the plurality of protrusions and the high-absorption structure in the radiation-absorbing region, as well as the reflective element within the trench isolation structure, the image sensor achieves improved MTF performance and improved QE.

[0087] Figures 26 to 31 Various views 2600 to 3100 illustrate some embodiments of a method for forming a semiconductor device or an image sensor including a high-absorption structure and a trench isolation structure with reflective elements. Although described with reference to the method... Figures 26 to 31 The various views shown are 2600 to 3100, but it should be understood that... Figures 26 to 31The structure shown is not limited to this method, but can exist independently of it. Furthermore, although... Figures 26 to 31 The description is a series of actions, but it should be understood that these actions are not limited, as the order of the actions can be changed in other embodiments, and the disclosed method is also applicable to other structures. In other embodiments, some actions illustrated and / or described may be omitted entirely or partially. Furthermore, although the method describes the formation of a BSI sensor, it should be understood that the disclosed trench isolation structure can also be used for FSI sensors.

[0088] according to Figure 26 The method and steps discussed in section view 2600 are as follows: Figure 12 Later, but with some other characteristics. Specifically, Figure 26 Displaying multiple rectangular protrusions 404, instead of Figure 12 The triangle in the middle has multiple protruding parts 142. Furthermore, Figure 26 Showing the removal Figure 12 The image sensor is located behind the second patterned mask layer 1202. Figure 26 It also shows the isolation trench 1204 aligned above the STI structure 802.

[0089] like Figure 27 As shown in cross-sectional view 2700, a first dielectric layer 116 is deposited on the exposed surfaces of the STI structure 802 and the substrate 102. In some embodiments, the first dielectric layer 116 is formed on the sidewalls and bottom surface of the isolation trench 1204, which are the top surface of the STI structure 802 and the sidewall of the substrate 102, respectively. Furthermore, the first dielectric layer 116 is formed on the back surface 102b of a plurality of protrusions 142. Since the plurality of protrusions 142 are rectangular, the first dielectric layer 116 forms a zigzag structure on the plurality of protrusions 142. In some embodiments, the first dielectric layer 116 may be or comprise a high-k dielectric layer, including hafnium oxide (HfO2), titanium oxide (TiO2), hafnium zirconium oxide (HfZrO), tantalum oxide (Ta2O3), hafnium silicon oxide (HfSiO4), zirconium oxide (ZrO2), zirconium silicon oxide (ZrSiO2), etc. In some embodiments, the first dielectric layer 116 can be deposited by deposition techniques (e.g., PVD, CVD, PE-CVD, ALD, etc.).

[0090] like Figure 28As shown in cross-sectional view 2800, a second dielectric layer 118 is deposited on the exposed surface of the first dielectric layer 116. The second dielectric layer 118 is formed on the first dielectric layer 116 within the isolation trench 1204 and on the first dielectric layer 116 on a plurality of protrusions 404. Furthermore, the second dielectric layer 118 fills the open regions between the plurality of protrusions, forming a substantially coplanar top surface of the second dielectric layer 118. In some embodiments, the second dielectric layer 118 is formed by a deposition process such as ALD or other suitable processes (e.g., PVD, CVD, PE-CVD, etc.). The second dielectric layer 118 may be or comprises alumina (Al2O3), hafnium oxide (HfO2), ZrO2, titanium oxide (TiO2), silicon oxide (SiO2), tantalum oxide (Ta2O5), or the like.

[0091] like Figure 29 As shown in cross-sectional view 2900, a conductive layer 2902 is formed within the isolation trench 1204 and on the back surface 102b of the substrate 102 covering the plurality of protrusions 404. The conductive layer 2902 is formed between the inner sidewalls of the padding layer 120 within the isolation trench 1204, thereby filling the central portion of the isolation trench 1204. Thus, the conductive layer 2902 extends from the isolation trench 1204 over the top surface of the second dielectric layer 118. In other embodiments (not shown), the padding layer is formed along the region above the second dielectric layer 118 and the plurality of protrusions 404 in the isolation trench 1204.

[0092] like Figure 30 As shown in the sectional view 3000, for (e.g., Figure 29 The conductive layer 2902 is removed by a removal process, thereby removing the conductive layer 2902 above the plurality of protrusions 404. After the removal process, the reflective element 122 is formed in the isolation trench 1204, and its top surface is flush with the top surface of the second dielectric layer 118. In some embodiments, the removal process may be a planarization process (e.g., chemical mechanical planarization process).

[0093] like Figure 31 As shown in the cross-sectional view 3100, a mesh structure 208 is formed on the reflective element 122. A lower dielectric layer 202 is formed on the mesh structure 208, the second dielectric layer 118, and the reflective element 122. A plurality of filters 204 are formed on the lower dielectric layer 202, and a plurality of microlenses 206 are formed on the plurality of filters 204. The mesh structure 208, the lower dielectric layer 202, the plurality of filters 204, and the plurality of microlenses 206 are as previously described. Figure 21 The relevant methods were formed.

[0094] Therefore, the above content presents a comparison with... Figures 8 to 21 The relevant first method, and Figures 22 to 25 The related second method, and with Figures 26 to 31 A related third method. Compared to the second and third methods, the first method has more processing steps and provides a manufacturing process that enables larger feature sizes and / or more precise feature formation, for example, for trench isolation structures and radiation-absorbing regions. Compared to the first method, the second method has fewer processing steps, but compared to the third method, it has more processing steps. The second method can achieve medium feature sizes, for example, for trench isolation structures and radiation-absorbing regions, but has lower precision compared to the first method. Compared to the first and second methods, the third method has fewer processing steps and is therefore cost-effective, suitable for image sensors with smaller features or lower precision in forming trench isolation structures and radiation-absorbing regions.

[0095] Figure 32 Flowcharts illustrating some embodiments of a method 3200 for forming an image sensor including a high-absorption structure and a trench isolation structure with reflective elements.

[0096] Although method 3200 is illustrated and described herein as a series of actions or events, it should be understood that the illustrated order of such actions or events should not be construed as limiting. For example, some actions may occur in a different order and / or simultaneously with other actions or events besides those illustrated and / or described herein. Furthermore, not all illustrated actions may be required to implement one or more of the states or embodiments described herein. Additionally, one or more of the actions illustrated herein may be performed in one or more separate actions and / or stages.

[0097] In 3202, a substrate having a light detector formed in multiple pixel regions is provided. Figures 8 to 10 The illustrations are cross-sectional views 800 to 1000 corresponding to some embodiments of action 3202.

[0098] In step 3204, a first etching process is performed on the back surface of the substrate to form multiple protrusions with a periodically repeating pattern within pixel regions of multiple pixel areas, the periodically repeating pattern being located above the photodetector in the pixel region. In some examples, the periodically repeating pattern is triangular in shape, and in other examples, the periodically repeating pattern is rectangular. Figure 11 and Figure 26 The illustrations are cross-sectional views 1100 and 2600 corresponding to some embodiments of action 3204.

[0099] At 3206, a second etching process is performed to form isolation trenches within the substrate and between photodetectors in multiple pixel regions. Figure 12 and Figure 26 The illustration shows cross-sectional views 1200 and 2600 corresponding to some embodiments of action 3206.

[0100] At 3208, a first dielectric layer is formed within the isolation trench and on multiple protrusions of the substrate. Figure 13 and Figure 27 The illustrations are cross-sectional views 1300 and 2700 corresponding to some embodiments of action 3208.

[0101] In 3210, a second dielectric layer is formed on the first dielectric layer within the isolation trench and on a plurality of protrusions. The first and second dielectric layers form a high-absorption structure on the photodetector. Figure 14 and Figure 28 The illustrations are cross-sectional views 1400 and 2800 corresponding to some embodiments of action 3210.

[0102] At 3212, a conductive layer is formed within the isolation trench and on the multiple protrusions. In some examples, the conductive layer is formed on the second dielectric layer. Figure 15 and Figure 29 The illustration shows cross-sectional views 1500 and 2900 corresponding to some embodiments of action 3212.

[0103] At 3214, one or more first removal processes or second removal processes are performed to remove the conductive layer aligned on the photodetector, thereby forming a reflective element within the isolation trench. Figures 16 to 20 , Figures 22 to 24 and Figure 30 The illustrations are cross-sectional views 1600 to 2000, 2200 to 2400 and 3000, corresponding to some embodiments of action 3214.

[0104] In 3216, a color filter is formed on the dielectric material. Figure 21 , Figure 25 and Figure 31 The illustration shows cross-sectional views 2100, 2500, and 3100 corresponding to some embodiments of action 3216.

[0105] Therefore, this disclosure relates to an image sensor with an enhanced BSI structure having a reflective element and a high-absorption structure on the photodetector, which improves QE and MTF.

[0106] According to one aspect of this disclosure, a semiconductor device is disclosed in which a photodetector is disposed in a substrate, wherein the substrate has a plurality of protrusions above the photodetector. An isolation structure is disposed in the substrate and laterally surrounds the photodetector, wherein the isolation structure includes a reflective element comprising a conductive material. A first dielectric layer is located above the photodetector, wherein the first dielectric layer extends substantially vertically into the substrate and is disposed between the reflective element and the substrate. The top surface of the first dielectric layer above the plurality of protrusions is irregular. A second dielectric layer is located on the first dielectric layer and above the photodetector. The top surface of the second dielectric layer above the plurality of protrusions is irregular. The second dielectric layer extends substantially vertically into the substrate along the surface of the first dielectric layer, and wherein the second dielectric layer is disposed along the sidewalls and bottom surface of the reflective element.

[0107] In some embodiments, the substrate further includes a padding layer disposed between the reflective element and the second dielectric layer, wherein the padding layer is disposed along the bottom surface of the reflective element. In some embodiments, the padding layer extends from a horizontal surface common to the top surface of the reflective element and the second dielectric layer. In some embodiments, the plurality of protrusions are located on a back surface of the substrate above the photodetector and are arranged between the top of the photodetector and the top surface of the reflective element. In some embodiments, the plurality of protrusions comprises a periodically repeating triangular protrusion pattern. In some embodiments, the plurality of protrusions comprises a periodically repeating rectangular protrusion pattern. In some embodiments, the upper surface of the second dielectric layer periodically extends from above the top surface of the first dielectric layer to a plane below the top surface of the first dielectric layer.

[0108] According to one aspect of this disclosure, the disclosure relates to an image sensor having a substrate including a front surface relative to a back surface. The substrate includes a first plurality of protrusions on the back surface. A first photodetector is disposed within the substrate and below the first plurality of protrusions. A reflective element is disposed within the substrate and laterally offset from the first photodetector. The reflective element extends from the back surface to the front surface. A high-absorption structure is disposed above the back surface of the substrate and extends into the substrate, wherein the high-absorption structure separates the bottom surface and sidewalls of the reflective element from the substrate. The high-absorption structure includes a first dielectric layer contacting the first plurality of protrusions and a second dielectric layer on the first dielectric layer. The first and second dielectric layers extend to the back surface of the substrate. A pad layer is located between the second dielectric layer and the reflective element, wherein the pad layer is laterally offset from the back surface of the substrate.

[0109] In some embodiments, the structure further includes an absorption layer disposed above the high-absorption structure. In some embodiments, the structure further includes a dielectric cap layer disposed on the reflective element, wherein the absorption layer is disposed between the inner sidewalls of the dielectric cap layer, and wherein the dielectric cap layer and the absorption layer have top horizontal surfaces that are substantially coplanar with each other. In some embodiments, the dielectric cap layer extends from the top surface of the second dielectric layer to the inner sidewall of the second dielectric layer, and wherein the dielectric cap layer directly contacts the top surface of the pad layer and the top surface of the reflective element. In some embodiments, the absorption layer is disposed between the inner sidewalls of the second dielectric layer and extends from a horizontal surface common to the top surface of the pad layer and the reflective element to the top surface of the second dielectric layer. In some embodiments, the absorption layer extends below the top surfaces of the first dielectric layer and the second dielectric layer and the top surface of the reflective element in the region aligned from above with the first photodetector. In some embodiments, the substrate further includes: a second photodetector disposed within the substrate, wherein the reflective element is spaced between the first photodetector and the second photodetector, wherein the substrate includes a second plurality of protrusions on the back surface and covering the second photodetector, wherein the first plurality of protrusions have a first shape and the second plurality of protrusions have a second shape different from the first shape.

[0110] According to one aspect of this disclosure, this disclosure relates to a method of forming an image sensor. The method includes forming a photodetector within a substrate. The method includes patterning the substrate to form an isolation trench in the substrate, the isolation trench laterally surrounding the photodetector. The method includes forming a first dielectric layer within the isolation trench, wherein the first dielectric layer is formed to pad a bottom surface and sidewalls of the isolation trench, and the first dielectric layer is formed on a back surface of the substrate. The method includes forming a second dielectric layer on the first dielectric layer within the isolation trench and on the back surface of the substrate. The method includes forming a pad layer on the second dielectric layer within the isolation trench and on the back surface of the substrate. The method includes forming a conductive layer on the pad layer within the isolation trench and on the back surface of the substrate. The method includes performing a first removal process to remove the pad layer and the conductive layer from a surface of the second dielectric layer aligned above the photodetector, thereby forming a reflective element within the isolation trench.

[0111] In some embodiments, the method further includes: patterning the back surface of the substrate to form a plurality of protrusions on the back surface of the substrate, wherein the plurality of protrusions are formed above the photodetector; forming a first dielectric layer on the plurality of protrusions; forming a second dielectric layer on the first dielectric layer above the plurality of protrusions, wherein after the first removal process, the pad layer and the conductive layer remain above the plurality of protrusions; and performing a second removal process to remove the pad layer and the conductive layer above the plurality of protrusions, wherein the first removal process is different from the second removal process. In some embodiments, the second removal process includes: forming a third dielectric layer over the reflective element, the residue of the conductive layer above the plurality of protrusions, and the second dielectric layer; patterning the third dielectric layer to form a dielectric cap layer over the reflective element and exposing the residue of the conductive layer above the plurality of protrusions; removing the residue of the conductive layer above the plurality of protrusions; and after performing the second removal process, forming an absorption layer over the plurality of protrusions between the inner sidewall of the dielectric cap layer and the top surface of the second dielectric layer. In some embodiments, the method further includes: patterning the substrate to form a plurality of protrusions on the back surface of the substrate above the photodetector, wherein after the first removal process, the top surface of the second dielectric layer above the photodetector is exposed, and the top surface of the reflective element is recessed below the top surface of the second dielectric layer. In some embodiments, after performing the first removal process, the method further includes: forming an absorption layer above the second dielectric layer, within the plurality of protrusions, and above the reflective element, wherein the top surface of the absorption layer is non-planar; and performing a second removal process on the absorption layer, wherein after the second removal process, the top surface of the absorption layer is substantially planar. In some embodiments, wherein the first dielectric layer and the second dielectric layer comprise different dielectric materials relative to each other, the pad layer comprises a first conductive material, and the conductive layer comprises a second conductive material different from the first conductive material.

[0112] The foregoing has outlined features of several embodiments to enable those skilled in the art to better understand the nature of this disclosure. Those skilled in the art should understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or attain the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that they can make various changes, substitutions, and modifications thereto without departing from the spirit and scope of this disclosure.

Claims

1. A semiconductor device, characterized in that, include: A photodetector is disposed in a substrate, wherein the substrate has a plurality of protrusions above the photodetector; An isolation structure is disposed in the substrate and laterally surrounds the photodetector, wherein the isolation structure includes a reflective element comprising a conductive material; A first dielectric layer is located above the photodetector, wherein the first dielectric layer extends substantially vertically into the substrate and is disposed between the reflective element and the substrate, and the top surface of the first dielectric layer above the plurality of protrusions is irregular. as well as A second dielectric layer is located on the first dielectric layer and above the photodetector, wherein the top surface of the second dielectric layer above the plurality of protrusions is irregular, wherein the second dielectric layer extends substantially vertically into the substrate along the surface of the first dielectric layer, and wherein the second dielectric layer is disposed along the sidewalls and bottom surface of the reflective element.

2. The semiconductor device according to claim 1, characterized in that, Including: A padding layer is disposed between the reflective element and the second dielectric layer, wherein the padding layer is disposed along the bottom surface of the reflective element.

3. The semiconductor device according to claim 2, characterized in that, The padding layer extends from a horizontal surface shared with the top surface of the reflective element and the second dielectric layer.

4. The semiconductor device according to claim 1, characterized in that, The plurality of protrusions are located on the back surface of the substrate above the photodetector and are arranged between the top of the photodetector and the top surface of the reflective element.

5. The semiconductor device according to claim 1, characterized in that, The upper surface of the second dielectric layer periodically extends from above the top surface of the first dielectric layer to a plane below the top surface of the first dielectric layer.

6. An image sensor, characterized in that, include: A substrate, including a front surface relative to a back side surface, wherein the substrate includes a first plurality of protrusions on the back side surface; A first photodetector is disposed within the substrate and located below the first plurality of protrusions; A reflective element is disposed within the substrate and laterally offset from the first photodetector, wherein the reflective element extends from the back surface toward the front surface; A high-absorption structure is disposed above the back surface of the substrate and extends into the substrate, wherein the high-absorption structure separates the bottom surface and sidewalls of the reflective element from the substrate, wherein the high-absorption structure includes a first dielectric layer contacting the first plurality of protrusions, and a second dielectric layer on the first dielectric layer, wherein the first dielectric layer and the second dielectric layer extend to the back surface of the substrate. as well as A padding layer is located between the second dielectric layer and the reflective element, wherein the padding layer is laterally offset from the back surface of the substrate.

7. The image sensor according to claim 6, characterized in that, Including: An absorption layer is disposed above the high-absorption structure.

8. The image sensor according to claim 7, characterized in that, Including: A dielectric cap layer is disposed on the reflective element, wherein the absorbing layer is disposed between the inner sidewalls of the dielectric cap layer, and wherein the dielectric cap layer and the absorbing layer have top horizontal surfaces that are substantially coplanar with each other.

9. The image sensor according to claim 7, characterized in that, The absorption layer is disposed between the inner sidewalls of the second dielectric layer and extends from a horizontal surface common to the top surface of the second dielectric layer, which is shared with the top surface of the pad layer and the top surface of the reflective element.

10. The image sensor according to claim 6, characterized in that, Including: A second photodetector is disposed within the substrate, wherein the reflective element is spaced between the first photodetector and the second photodetector. The substrate includes a second plurality of protrusions on the back surface and covering the second photodetector, wherein the first plurality of protrusions have a first shape and the second plurality of protrusions have a second shape different from the first shape.

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